JP2011037453A - Food packaging film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a food packaging film which is superior in heat resistance, stable heat sealability, food hygiene, impact resistance under a low-temperature condition, and drop rupture resistance under a low-temperature condition. <P>SOLUTION: The food packaging film is a film that is composed mainly of a propylene-ethylene block copolymer. The food packaging film contains at least a phenolic antioxidant, phosphorous-acid-based antioxidant, and acrylate-based antioxidant and includes a 20°C xylene solubilized portion of 20 to 30 mass%. The film is cut in the direction parallel with its longitudinal direction and perpendicular to the film surface, and the resultant cut section is stained with a ruthenium oxide, then carbon is vapor deposited on the stained section. When the carbon-deposited stained section is observed with a transmission electron microscope, it is found that island components present in an actual area of 600 μm<SP>2</SP>, in which the island components' longitudinal maximum length is 20 μm or longer and the ratio of the longitudinal maximum length and the vertical maximum length is 0.2 or above, accounts for 20% or above of the section. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a film for food packaging, and more particularly to a film used for food packaging particularly suitable for retort treatment as a film laminated with a substrate.

Films having heat sealing properties are widely used for packaging applications such as food packaging and fiber packaging.
Especially for food packaging applications, after retort treatment after food filling, the form that is boxed, transported and sold over the counter is increasing in recent years, and a film that combines both sealing and heat resistance is required, Polypropylene film is used.
Furthermore, after the retort treatment as described above, there are many cases in which bag tearing due to freezing storage or dropping during freezing transport is regarded as a problem, and an improvement in bag breaking strength at low temperatures is also demanded.
A number of proposals have been made as a method for solving the above-described demand (see, for example, Patent Documents 1 to 4).

Japanese Patent Laid-Open No. 9-248885 JP 2000-143931 A JP 2000-186159 A JP 2002-302579 A

  Patent Document 1 includes 50 to 80% by mass of a polyolefin mainly composed of a propylene-ethylene block copolymer having a melting point of 140 to 165 ° C. and 50 to 20% by mass of a propylene copolymer having a melting point of 130 to 150 ° C. A polyolefin film for retort obtained by blending 3 to 20 parts by mass of a thermoplastic elastomer with respect to 100 parts by mass of a mixed resin is disclosed.

  In Patent Document 2, a specific amount of thermoplastic elastomer is blended with a polyolefin-based polymer mainly composed of a block polyolefin resin whose main component is a propylene-ethylene block copolymer having a melting point of 156 to 168 ° C. Heat resistance, stable heat sealability, food hygiene, and impact resistance at low temperatures by setting the intrinsic viscosity of the raw resin and the resulting film to a specific range. In addition, it is disclosed that a food packaging film having excellent burst resistance when dropped at a low temperature can be obtained.

  Patent Document 3 discloses a film for retort food packaging having good impact resistance, blocking resistance, and heat sealability at low temperatures by using a propylene-ethylene block copolymer obtained by a gas phase polymerization method as a raw material. Is disclosed.

  In Patent Document 4, an odor is obtained by using a resin composition containing 100 parts by weight of a polypropylene resin such as a propylene-ethylene block copolymer and 0.01 to 0.5 parts by weight of a specific phosphite. It is disclosed that a molded product for food packaging having excellent taste and impact strength can be obtained.

However, recently, sterilization at higher temperatures has been carried out, and seal resistance after such high-temperature sterilization and durability against external forces such as impact during transportation are resistant to rupture and separation of the seal part. The demand for sex is becoming stricter.
In the conventional film, the impact resistance is improved by blending the thermoplastic elastomer, but the seal strength is not sufficient, and there is a problem that the burst resistance at the time of dropping at a low temperature is not sufficient.

  An object of the present invention is to provide a film for food packaging excellent in heat resistance, stable heat sealability, food hygiene, and bursting resistance when dropped at a low temperature or when a large external force is applied.

  As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.

That is, the present invention is a film comprising a propylene-ethylene block copolymer as a main component, and contains at least a phenolic antioxidant, a phosphorous acid antioxidant and an acrylate antioxidant. The xylene soluble part is 20 to 30% by mass, the cut section of the film cut in a direction parallel to the longitudinal direction and perpendicular to the film surface is dyed with ruthenium oxide, and the dyed surface is carbon-deposited to be transmissive type An island component observed using an electron microscope and having an actual longest diameter in an area of 600 μm ² having an actual longest diameter of 20 μm or more and a ratio of the longest diameter to the maximum vertical diameter of 0.2 or more Is a film for food packaging, characterized in that the ratio is 20% or more.
In this case, it is preferable that the ratio of falling bag broken bags evaluated by the method described in the specification of the food packaging film is 20% or less and the seal strength after retorting is 38 to 110 N / 15 mm. .
Further, in this case, 85 to 95 parts by mass of a polypropylene-based block copolymer resin whose main component is a propylene-ethylene block copolymer having a 20 ° C. xylene soluble part of 5 to 20% by mass and a thermoplastic elastomer of 5 to 15 parts by mass. It is preferable to consist of the resin composition which mix | blended the part.

According to the film for food packaging of the present invention, it has excellent sealing properties, heat resistance, bag-breaking resistance, food hygiene, and simultaneously satisfies the characteristics required as a food packaging film suitable for retort processing.
In particular, the balance between anti-breaking bag resistance and seal strength after retort treatment is improved, and both properties are compatible, so when used as a constituent material for packaging bags for retort foods, excellent retort treatment In addition, the reliability of durability against external forces such as impact of the packaging bag during storage and transportation of food after retorting is improved.
Therefore, it can be suitably used as a constituent material of a food packaging film, particularly a retort food packaging bag.

In the film mainly composed of a block polyolefin resin mainly composed of the propylene-ethylene block copolymer of the present invention, the 20 ° C. xylene soluble part of the film is 20 to 30% by mass.
As for the 20 degreeC xylene soluble part of the said film, 22-28 mass% is more preferable. Here, the 20 ° C. xylene-soluble part reflects the amount of rubber contained in the film. If the 20 ° C. xylene-soluble part of the film is less than 20% by mass, the impact resistance of the film is lowered, and the falling bag breaking resistance of a packaging bag obtained using the film is not preferable. On the contrary, when it exceeds 30 mass%, since the sealing strength and transparency of a film fall, it is unpreferable.

The polypropylene block copolymer resin in the present invention is a block copolymer of a copolymer component of a large amount of propylene and a small amount of ethylene and a copolymer component of a small amount of propylene and a large amount of ethylene. Yes, the molecular weight of each copolymer block is controlled at the polymerization stage.
Specifically, as shown in JP-A No. 2000-186159, it is preferable to use one that is subjected to gas phase polymerization. That is, in the first step, a polymer part (component A) mainly composed of propylene is polymerized in the presence of an inert solvent, and then in the second step, the ethylene content is 20 to 50% by weight in the gas phase. The block copolymer obtained by superposing | polymerizing the copolymer part (B component) of propylene and ethylene is mentioned.

As a method for bringing the amount of the 20 ° C. xylene soluble part of the above film into the above range, when the above polypropylene block copolymer is used alone or when the above polypropylene block copolymer is mixed with another thermoplastic elastomer Is mentioned.
The amount of the 20 ° C. xylene soluble part of the film has a correlation with the total content of the B component and the thermoplastic elastomer component of the polypropylene block copolymer. For example, when the polypropylene block copolymer is used alone, The method of making the quantity of a 20 degreeC xylene soluble part of a polypropylene-type block copolymer resin 20-30 mass% is mentioned.
At this time, even if the ethylene content in the polypropylene block copolymer is the same, it varies depending on the copolymerization ratio of ethylene-propylene in the A component and the B component, and thus needs to be adjusted as appropriate.

  The melt flow rate (MFR) of the polypropylene block copolymer resin is preferably 1 to 10 g / 10 min, and more preferably 2 to 7. If it is less than 1 g / 10 minutes, the viscosity is too high and extrusion with a T-die is difficult. Conversely, if it exceeds 10 g / 10 minutes, the stickiness of the film and the impact strength (impact strength) of the film are inferior. This is because problems arise.

  1.0-3.0 are preferable and, as for the intrinsic viscosity ((eta)) of the said polypropylene-type block copolymer resin, 1.2-2.8 are more preferable. If it exceeds 3.0, the viscosity is too high and extrusion with a T-die is difficult. Conversely, if it is less than 1.0, the stickiness of the film and the impact strength (impact strength) of the film are inferior. This is because problems arise.

  In general, it is known that there is a correlation between MFR and intrinsic viscosity η. By knowing the η of the film, the MFR of the resin used can be known. η is a measure of molecular weight, and the larger the value, the larger the molecular weight, and the smaller the value, the smaller the molecular weight. MFR is a measure of molecular weight. The smaller the value, the larger the molecular weight, and the larger the value, the smaller the molecular weight.

The polypropylene block copolymer resin having a 20 ° C. xylene soluble part amount higher than 20% by mass may be difficult to handle.
Therefore, for example, a resin composition in which 85 to 95 parts by mass of a block polyolefin resin mainly composed of a propylene-ethylene block copolymer having a 20 ° C. xylene soluble part of 5 to 20% by mass and 5 to 15 parts by mass of a thermoplastic elastomer is blended. It is preferable in terms of handleability to use a product, more preferably 7 to 18 parts by mass of a 20 ° C. xylene-soluble part of a block polyolefin resin mainly composed of a propylene-ethylene block copolymer, and further 12 to 18 parts by mass preferable.
Further, the blending amount of the block polyolefin resin mainly composed of the propylene-ethylene block copolymer is more preferably 87 to 93 parts by mass, and the blending amount of the thermoplastic elastomer is more preferably 7 to 13 parts by mass.

  An α-olefin copolymer resin is used as the thermoplastic elastomer. More specifically, an ethylene / α-olefin copolymer resin, a hydrogenated block copolymer resin and the like can be mentioned.

The ethylene / α-olefin copolymer resin is obtained by copolymerizing ethylene and an α-olefin having 3 to 12 carbon atoms using a metallocene catalyst, and is a melt flow rate (Condition E of ASTM D 1238). (Measured at a temperature of 190 ° C. and a load of 2.16 kg) is 0.1 to 10 g / 10 min, a density is 0.820 to 0.930 g / cm ³ (measured by ASTM D 1505), and a molecular weight distribution (Mw) determined by GPC method It is desirable to use those having a / Mn) of 1.3 to 6.0.

The α-olefin is specifically an alkene having a carbon-carbon double bond at the α-position. Alkenes are unsaturated hydrocarbons and are represented by C _n H _2n . For example. If n = 3, it is propylene, and two of the three carbons have a double bond between two carbons, one of which is a π bond and one is a σ bond. In addition, the π bond portion tends to cause an addition reaction because the bond energy is small.

  The hydrogenated block copolymer is composed of a polymer block A mainly composed of at least one vinyl aromatic compound and a copolymer block B mainly composed of at least one hydrogenated conjugated diene compound. For example, it is a hydrogenated block copolymer composed of ABA, BABA, BABA, and a mixture thereof. And what contains 10-40 mass% of vinyl aromatic compounds can be used as this hydrogenated block copolymer.

  As the vinyl aromatic compound constituting the hydrogenated block copolymer, for example, styrene, α-methylstyrene, and the like can be used, and styrene is particularly preferable. As the conjugated diene compound before hydrogenation constituting the hydrogenated conjugated diene compound, for example, butadiene, isoprene, or 1-3 pentadiene can be used, and butadiene is particularly preferable. The olefinic compound polymer block B is preferably obtained by hydrogenating 80%, preferably 90% or more of the aliphatic double bond based on the conjugated diene compound of the vinyl aromatic compound-conjugated diene compound block copolymer. A typical example of the copolymer is a styrene-ethylene-butylene-styrene copolymer, and the copolymerization amount of styrene is preferably 10 to 30% by weight. From the viewpoint of transparency, 10 to 20% by weight is preferred.

The melt flow rate (MFR) of the thermoplastic elastomer is preferably 5 g / 10 min or less, preferably 0.2 to 5 g / 10 min in terms of impact resistance at low temperatures.
The difference between the melt flow rate (MFR) of the thermoplastic elastomer and the melt flow rate (MFR) of the polypropylene block copolymer resin is preferably 0 to 7 and preferably 0 in terms of uniform kneading and preventing fish eye. ~ 4.
In addition, the intrinsic viscosity (η) of the thermoplastic elastomer is preferably 1.0 to 5.0, and preferably 1.2 to 5.0 in terms of maintaining uniform seal strength, impact strength, and bag drop strength. 3.0.
The difference between the intrinsic viscosity (η) of the thermoplastic elastomer and the intrinsic viscosity (η) of the polypropylene block copolymer resin is preferably from 0 to 5.0 in view of uniform kneading and preventing fish eyes, and preferably 0. ~ 3.0.

  In the present invention, it is preferable to use an ethylene / α-olefin copolymer resin from the viewpoints of low molecular weight bleed and transparency, food safety and food hygiene.

In the present invention, the cross section of the film cut in a direction parallel to the longitudinal direction and perpendicular to the film surface is dyed with ruthenium oxide, the dyed surface is carbon-deposited and observed using a transmission electron microscope, and the actual area The maximum length in the longitudinal direction existing in an area of 600 μm ² is 20 μm or more, and the ratio of the maximum length in the longitudinal direction to the maximum length in the longitudinal direction and the maximum length in the vertical direction is 0.2 or more. The ratio is preferably 20% or more.

The film for food packaging of the present invention is obtained by dyeing a cut section obtained by cutting the film in a direction parallel to the longitudinal direction and perpendicular to the film surface with ruthenium oxide, depositing the dyed surface with carbon, and using a transmission electron microscope. Observed, the ratio of the island component whose actual longest diameter existing in an area of 600 μm ² is 20 μm or more and the ratio of the longest diameter to the maximum diameter in the vertical direction is 0.2 or more is 30%. More preferably, it is more preferably 40% or more.

The island component observed by the above method is composed of the component B derived from the polypropylene block copolymer resin in the film and a component derived from the thermoplastic elastomer.
The component B derived from the polypropylene block copolymer resin and the component derived from the thermoplastic elastomer are hardly compatible with the component A of the polypropylene block copolymer resin, and are dispersed in the component A with a specific diameter.
Such an island component easily adsorbs ruthenium oxide, and can be distinguished from the resin derived from the A component that hardly adsorbs ruthenium oxide.
The impact resistance of the film is proportional to the number and size of islands in the film, and the impact resistance is improved as the volume ratio of the islands in the film increases. On the other hand, there is a trade-off phenomenon that the seal strength decreases as the ratio of the area occupied by the island in the film cross section (in the direction parallel to the film surface) increases.
As described above, the method of absorbing and dispersing the energy of external force such as impact by the rubber component by simply blending the rubber component with the polypropylene film is an effective method as means for improving the impact resistance. Even if the peel strength at the interface between the rubber component and the polypropylene resin as the matrix component is reduced, the sealing strength is reduced and the impact resistance of the film itself is improved. When the force is applied, the heat seal part peels off, and the bag is easily broken.
However, the inventors have also affected the shape of the island in the film, and the seal strength is reduced by reducing the flatness in the direction parallel to the film surface of the island-shaped cross section (direction perpendicular to the film surface), that is, It became possible to suppress the decrease in the seal strength by making it close to a circle, and it was found that the above antinomy event can be overcome.
Therefore, it is possible to improve the seal strength as well as the impact resistance by controlling the dispersed shape of the islands in the film.
The ratio of the maximum length in the longitudinal direction of the island component to the maximum length in the longitudinal direction and the maximum length in the vertical direction is a measure of the flatness in the horizontal direction of the shape of the rubber component dispersed in the film, When the ratio of the maximum length in the longitudinal direction of the island component to the maximum length in the longitudinal direction and the maximum length in the vertical direction is 0.2 or more, the influence on the decrease in seal strength is reduced. Moreover, the influence of the size of the maximum length in the longitudinal direction is large, and it has empirical knowledge that the influence of an island having a maximum length of 20 μm or more in the longitudinal direction is large. Therefore, the ratio of the island component having an actual longest diameter of 20 μm or more and a ratio of the maximum length in the longitudinal direction to the maximum length in the longitudinal direction and the maximum length in the vertical direction being 0.2 or more is reduced with respect to the total island component. As a result, the sealing strength can be improved, and the bag-breaking resistance can be greatly improved.
Therefore, the film of the present invention can suppress the occurrence of burst resistance and seal leakage even when a large external force such as an impact is applied to the packaging bag during storage or transportation of food after retorting, and thus the reliability of durability against external force Can be improved. The effect is particularly great at low temperatures.

In order to control the dispersed shape of the islands in the film, it is a preferred embodiment to optimize the composition of the antioxidant when changing the design with the screw of the extruder (or when it is difficult to change the screw design).
The method preferably comprises at least three antioxidants, phenolic, phosphorous and acrylate. The total amount of the antioxidant at this time is preferably 1500 to 3500.
The function of each antioxidant is as follows. The acrylate antioxidant has a function of capturing the radical “R.” generated by heat and shearing and returning it to “RH” in the extruder. The phenolic antioxidant is said to be a primary antioxidant, and has a function of scavenging a radical in which “R.” is combined with oxygen (O ₂ ) and becomes “ROO.” To “ROOH”. Phosphorous acid system has a phenolic antioxidant part and a phosphoric acid antioxidant part in the molecule, and it functions as a phosphorus antioxidant while acting as a phenolic antioxidant. Has excellent performance.

  Examples of phosphorous acid antioxidants include phosphites represented by the following general formula (I).

In the phosphites represented by the general formula (I), the substituents R ¹ , R ² , R ⁴ and R ⁵ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or 5 carbon atoms. Represents a cycloalkyl group having 8 to 8 carbon atoms, an alkylcycloalkyl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, or a phenyl group.

  Here, as a representative example of an alkyl group having 1 to 8 carbon atoms, for example, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, Examples thereof include t-butyl group, t-pentyl group, i-octyl group, t-octyl group, 2-ethylhexyl group and the like. Typical examples of the cycloalkyl group having 5 to 8 carbon atoms include, for example, cyclopentyl group, cyclohexyl. Group, cycloheptyl group, cyclooctyl group and the like, and typical examples of the alkylcycloalkyl group having 6 to 12 carbon atoms include, for example, 1-methylcyclopentyl group, 1-methylcyclohexyl group, 1-methyl-4- i-propylcyclohexyl group and the like, and typical examples of the aralkyl group having 7 to 12 carbon atoms include, for example, benzyl group and α-methylbenzyl group. alpha, alpha-dimethylbenzyl group and the like.

R ¹ , R ² and R ⁴ are preferably an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, and an alkylcycloalkyl group having 6 to 12 carbon atoms. Among these, R ¹ and R ⁴ are more preferably a t-butyl group, a t-pentyl group, a t-octyl group such as a t-octyl group, a cyclohexyl group, or a 1-methylcyclohexyl group.

R ² is more preferably carbon such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, t-pentyl group, etc. An alkyl group having 1 to 5 atoms, more preferably a methyl group, a t-butyl group, or a t-pentyl group.

R ⁵ is preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms, more preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, i -An alkyl group having 1 to 5 carbon atoms such as a propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, t-pentyl group.

The substituent R ³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and examples of the alkyl group having 1 to 8 carbon atoms include the same alkyl groups as described above. Preferably they are a hydrogen atom or a C1-C5 alkyl group, More preferably, they are a hydrogen atom or a methyl group.

  Substituent X, when n is 0, represents that two groups having a phenoxy group skeleton are directly bonded, and when n is 1, a sulfur atom or an alkyl group having 1 to 8 carbon atoms. Or the methylene group which the C5-C8 cycloalkyl group may substitute is represented. Here, examples of the alkyl group having 1 to 8 carbon atoms and the cycloalkyl group having 5 to 8 carbon atoms substituted on the methylene group include the same alkyl groups and cycloalkyl groups as described above. As the substituent X, preferably n is 0 and a group having two phenoxy group skeletons is directly bonded, or n is 1, and a methylene group, a methyl group, an ethyl group, or an n-propyl group. , I-propyl group, n-butyl group, i-butyl group, t-butyl group and the like are substituted methylene groups.

Substituent A is an alkylene group having 2 to 8 carbon atoms or * -CO (R ⁷ ) m-group (R ⁷ is an alkylene group having 1 to 8 carbon atoms, and * is a bonding site with an oxygen atom. And m is 0 or 1.

Here, as typical examples of the alkylene group having 2 to 8 carbon atoms, for example, ethylene group, propylene group, butylene group, pentamethylene group, hexamethylene group, octamethylene group, 2,2-dimethyl-1,3- A propylene group etc. are mentioned, Preferably it is a propylene group. The * -COR 7 ^- * in group indicates that the carbonyl group is a moiety that binds to the oxygen atom of the phosphite group. As typical examples of the alkylene group having 1 to 8 carbon atoms in R ⁷ , for example, a methylene group, an ethylene group, a propylene group, a butylene group, a pentamethylene group, a hexamethylene group, an octamethylene group, 2,2-dimethyl- Examples include 1,3-propylene group. * -CO (R ⁷ ) m- group, preferably m is 0 * -CO- group, or m is 1 and R ⁷ is ethylene * -CO (CH ₂ CH ₂ )-group It is.

  One of Y and Z represents a hydroxyl group, an alkoxy group having 1 to 8 carbon atoms or an aralkyloxy group having 7 to 12 carbon atoms, and the other represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. .

  Here, examples of the alkyl group having 1 to 8 carbon atoms include the same alkyl groups as described above. Examples of the alkoxy group having 1 to 8 carbon atoms include an alkyl moiety having the above-described alkyl having 1 to 8 carbon atoms. The alkoxy group which is the same alkyl is mentioned, and the aralkyloxy group having 7 to 12 carbon atoms includes, for example, an aralkyloxy group in which the aralkyl moiety is the same aralkyl as the aralkyl having 7 to 12 carbon atoms.

  The phosphites represented by the above general formula (I) are 2,4,8,10-tetra-tert-butyl-6- [3- (3-methyl-4-hydroxy-5-tert-butylphenyl). Propoxy] dibenzo [d, f] [1,3,2] dioxaphosphine is preferred. The use of Sumitizer GP (registered trademark) manufactured by Sumitomo Chemical Co., Ltd. is preferred.

  Although the compounding quantity of said phosphite ester in this invention is not limited, The range of 100-1000 ppm is preferable with respect to the above-mentioned all polypropylene resin composition. 200 to 800 ppm is more preferable, and 300 to 700 ppm is more preferable.

  The acrylate antioxidant of the present invention is an antioxidant having a phenol derivative containing an acrylate residue in the molecule, and includes those having a structure represented by the following formula (II).

In the formula (II), R ⁶ is an alkyl group having 1 to 5 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, a t-butyl group, and a 2,2-dimethylpropyl group. A methyl group or an ethyl group is preferable, and an ethyl group is more preferable.

In the formula (II), R ⁷ is an alkyl group having 1 to 8 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, a t-butyl group, a t-pentyl group, and a t-octyl group. It is done. A methyl group, a t-butyl group or a t-pentyl group is preferred, and a t-pentyl group is more preferred.

In the formula (II), R ⁸ is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and examples thereof include a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and an octyl group. . Preferably they are a hydrogen atom or a methyl group, More preferably, it is a methyl group.

In the formula (II), R ⁹ is a hydrogen atom or a methyl group. Preferably it is a hydrogen atom.

  Examples of the acrylate compound include 2,4-di-t-amyl-6- [1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl] phenyl acrylate, 2,4-di- t-amyl-6- [1- (3,5-di-t-amyl-2-hydroxyphenyl) butyl] phenyl acrylate, 2,4-di-t-amyl-6- [1- (3,5- Di-t-amyl-2-hydroxyphenyl) propyl] phenyl acrylate, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, and the like. .

  Preferably, 2,4-di-t-amyl-6- [1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl] phenyl acrylate and 2-t-butyl-6- (3- t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate.

  As said acrylate compound, it can select from a commercially available thing suitably and can be used. For example, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, Sumitizer GM (registered trademark) manufactured by Sumitomo Chemical Co., Ltd., 2,4- Sumitizer GS (registered trademark) manufactured by Sumitomo Chemical Co., Ltd., which is di-t-amyl-6- [1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl] phenyl acrylate, can be exemplified. . In particular, it is preferable to use a Sumilizer GS (registered trademark).

  The blending amount of the acrylate antioxidant in the present invention is preferably in the range of 100 to 1000 ppm with respect to the total polypropylene resin composition. 200 to 800 ppm is more preferable, and 300 to 700 ppm is more preferable.

  The phenolic antioxidant used in the present invention is an antioxidant having a phenol derivative in the molecule, such as 2,6-di-t-butyl-4-methylphenol, 2,6-di-t. -Butyl-4-ethylphenol, 2,6-dicyclohexyl-4-methylphenol, 2,6-di-t-amyl-4-methylphenol, 2,6-di-t-octyl-4-n-propylphenol 2,6-dicyclohexyl-4-n-octylphenol, 2-isopropyl-4-methyl-6-t-butylphenol, 2-t-butyl-2-ethyl-6-t-octylphenol, 2-isobutyl-4-ethyl -6-t-hexylphenol, 2-cyclohexyl-4-n-butyl-6-isopropylphenol, dl-α-tocopherol, t-butyl Ruhydroquinone, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 4,4′-thiobis (3-methyl-) 6-t-butylphenol), 2,2-thiobis (4-methyl-6-t-butylphenol), 4,4′-methylenebis (2,6-di-t-butylphenol), 2,2′-methylenebis [6 -(1-methylcyclohexyl) -p-cresol], 2,2′-ethylidenebis (4,6-di-t-butylphenol), 2,2′-butylidenebis (2-t-butyl-4-methylphenol) ,

  2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- [1- (2-hydroxy-3,5-di-t-pentyl) Phenyl) ethyl] -4,6-di-t-pentylphenyl acrylate, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2 , 2-thiodiethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-tert-butyl) -4-hydroxy-hydrocinnamide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, tris (2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate, tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, tris [(3,5-di-t-butyl-4-hydroxyphenyl) propionyloxyethyl] isocyanurate, tris (4-t- Butyl-2,6-dimethyl-3-hydroxybenzyl) isocyanurate, 2,4-bis (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5 -Triazine, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate Methane, 2,2′-methylenebis (4-methyl-6-tert-butylphenol) terephthalate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxy Benzyl) benzene, 3,9-bis [1,1-dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} ethyl] -2,4,8,10 -Tetraoxaspiro [5,5] undecane, 2,2-bis [4- (2- (3,5-di-t-butyl-4-hydroxyhydrocinnamoyloxy)) ethoxyphenyl] propane, β- ( 3,5-di-t-butyl-4-hydroxyphenyl) propionic acid stearyl ester and the like.

  Preferably, β- (3,5-di-t-butyl-4-hydroxyphenyl) propionic acid stearyl ester, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] Methane, tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4- Hydroxybenzyl) benzene, dl-α-tocopherol, tris (2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate, tris [(3,5-di-tert-butyl-4-hydroxyphenyl) ) Propionyloxyethyl] isocyanurate, 3,9-bis [1,1-dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methyl) Butylphenyl) propionyloxy} ethyl] -2,4,8,10-tetra-oxa-spiro [5,5] undecane.

  Commercially available products may be used as the phenolic antioxidant used in the present invention. For example, Irganox 1010 (manufactured by Ciba Specialty Chemicals), Irganox 1076 (manufactured by Ciba Specialty Chemicals) ), Irganox 1330 (manufactured by Ciba Specialty Chemicals), Irganox 3114 (manufactured by Ciba Specialty Chemicals), Irganox 1425WL (manufactured by Ciba Specialty Chemicals), and the like.

  In these, it is preferable to use together 2 types of phenolic antioxidants from which molecular weight differs. Although this combination is not limited, for example, two types of Irganox 1010 (Ciba Specialty Chemicals, Inc., molecular weight 1178) and Irganox 1076 (Ciba Specialty Chemicals, Inc., molecular weight 531) are used in combination. Is preferred. The reason why the effect of the present invention is more remarkably expressed by the combination is not clear, but, for example, by using an antioxidant having a molecular weight of 1000 or less, familiarity with the rubber component is improved and the rubber component is deteriorated. It is conjectured that the circularity of the island formed by the rubber component is suppressed and the sealing strength is improved as a result.

  The blending amount of the phenolic antioxidant in the present invention is preferably in the range of 500 to 5000 ppm with respect to the total polypropylene resin composition. 1000 to 4000 ppm is more preferable, and 1500 to 3000 ppm is more preferable.

  In the present invention, it is a more preferable embodiment that another type of phosphoric acid-based antioxidant other than the phosphorous acid type is used in combination with the above three types of antioxidant systems.

  As a specific example of another phosphorus antioxidant used in the present invention, for example, a heat containing a trivalent phosphorus atom in the molecule and having at least one P—O—C bond. Stabilizers can be mentioned. For example, tributyl phosphite, trioctyl phosphite, trilauryl phosphite, tristearyl phosphite, tridecyl phosphite, tricresyl phosphite, tricyclohexyl phosphite, triphenyl phosphite, trilauryl thiophosphite, tris ( 2-ethylhexyl) phosphite, tris (isodecyl) phosphite, tris (tridecyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, tris (butoxyethyl) phosphite, tris (nonylphenyl) Phosphite, tris (3,5-di-t-butyl-4-hydroxyphenyl) phosphite, tris [4,4′-isopropylidenebis (2-t-butylphenol)] phosphite, tris (1,3- Gieste (Royloxyisopropyl) phosphite, 2-ethylhexyl diphenyl phosphite, decyl diphenyl phosphite, phenyl di-2-ethyl hexyl phosphite, phenyl didecyl phosphite, phenyl diisodecyl phosphite, phenyl di (tridecyl) phosphite, diphenyl nonyl phosphite, Diphenyl isooctyl phosphite, diphenyl isodecyl phosphite, diphenyl mono (tridecyl) phosphite, dibutyl hydrogen phosphite, 4,4′-isopropylidene diphenol alkyl (C12 to C15) phosphite, 4,4′-butylidenebis ( 3-methyl-6-tert-butylphenyl) di-tridecyl phosphite, 2,2-methylenebis (4,6-di-tert-butylphenyl) octyl Sufite, 2,2'-ethylidenebis (4,6-di-t-butylphenol) fluorophosphite, bis (2,4-di-t-butyl-6-methylphenyl) .ethyl phosphite, 4,4 ' -Isopropylidenebis (2-t-butylphenol) di (nonylphenyl) phosphite, distearyl pentaerythritol diphosphite, di (nonylphenyl) pentaerythritol diphosphite, diphenylpentaerythritol diphosphite, phenyl 4, 4'-isopropylidenediphenol pentaerythritol diphosphite, bis (4,6-di-t-butylphenyl) pentaerythritol diphosphite, bis (2,6-di-t-butyl-4-methylphenyl) Pentaerythritol diphosphite, phenyl -Bisphenol A pentaerythritol diphosphite, tetraphenyldipropylene glycol diphosphite, tetra (tridecyl) -1,1,3-tris (2-methyl-5-tert-butyl-4-hydroxyphenyl) butanediphos Phyto, tetra (C12-C15 mixed alkyl) -4,4′-isopropylidene diphenyl diphosphite, tetra (tridecyl) -4,4′-butylidenebis (3-methyl-6-tert-butylphenol) diphosphite, tetrakis (4 , 6-Di-t-butylphenyl) -4,4′-biphenylene diphosphonite, tetrakis (2-methyl-4,6-di-t-butylphenyl) -4,4′-biphenylene diphosphonite Bis (octylphenyl) -bis [4,4′-butylidenebis (3-methyl) 6-t-butylphenol)] • 1,6-hexanediol diphosphite, hydrogenated-4,4′-isopropylidene diphenol polyphosphite, 9,10-di-hydro-9-oxa-9-oxa- 10-phosphaphenanthrene-10-oxide, 2-[{2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo (D, F) (1,3,2) -dioxaphos Fephin-6-yl} oxy] -N, N-bis [2-[{2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo (D, F) (1,3,2) -Dioxaphosphine-6-yl} oxy] ethyl] ethanamine, 1,1,3-tris (2-methyl-4-di-tridecylphosphite-5-t-butylphenyl) butane, 3,4 , 5,6-Tetraben Like 1,2-oxa phosphane-2-oxide.

  Preferably, those having no pentaerythritol skeleton, tris (2,4-di-t-butylphenyl) phosphite, tris (3,5-di-t-butyl-4-hydroxyphenyl) phosphite, Bis (2,4-di-t-butyl-6-methylphenyl) .ethyl phosphite, tetrakis (2-methyl-4,6-di-t-butylphenyl) -4,4'-biphenylenediphosphonite It is.

  Commercially available products may be used as the phosphorus-based antioxidant used in the present invention. For example, Irgaphos 168 (Ciba Specialty Chemicals Co., Ltd.), Irgaphos 38 (Ciba Specialty Chemicals Co., Ltd.), Examples include GSY-P101 (manufactured by Yoshitomi Fine Chemical Co., Ltd.), Ultranox 641 (manufactured by GE Specialty Chemicals Co., Ltd.), and the like.

  The blending amount of the phosphorus antioxidant in the present invention is preferably in the range of 500 to 5000 ppm with respect to the total polypropylene resin composition. 1000 to 4000 ppm is more preferable, and 1500 to 3000 ppm is more preferable.

  The above phosphorus antioxidant is made into “ROOH” by the primary antioxidant, but it is still unstable and “RH” acts on it, and it is easy to generate “R · + ROOH” and radicals. It has the function of changing to a stable “ROH” and inactivating it, and its synergistic effect is exhibited.

  Further, in addition to the above four kinds of antioxidants, for example, an antioxidant having another structure such as a sulfur-based antioxidant may be further used in combination.

  The thickness of the film of the present invention is preferably 1 to 500 μm, more preferably 10 to 100 μm.

  The method for preparing a polypropylene resin composition containing the antioxidant and other additives used in the present invention is, for example, a method of heat-melt kneading using a kneader such as a kneader, a Banbury mixer, or a roll, uniaxial or Examples thereof include a method of heat-melt kneading using a twin screw extruder or the like. Various resin pellets may be dry blended. In the method for preparing the composition, the antioxidant and the crystal nucleating agent may be added directly to the respective powders, or may be added as a master batch previously mixed with the polypropylene resin. When adding as a masterbatch, it may be prepared for each additive or may be prepared by mixing two or more. Moreover, you may implement combining the commercially available resin in which the said additive was mix | blended well. In addition, the composition may be prepared in advance to be supplied to a film forming process and supplied to a film forming extruder, or the components constituting the composition may be supplied to the film forming extruder. It may be supplied and prepared to form a film.

  The film of the present invention can be formed by a known method such as a T-die method or an inflation method, and is preferably an unstretched film.

  The degree of dispersion of the above-mentioned island component, that is, the rubber component in the film is affected by the degree of kneading of the raw material resin composition in the extrusion process of film formation. Increasing the degree of kneading improves the spherical dispersibility of the rubber component, but also promotes the deterioration of the resin including the rubber component, which adversely affects the bag breaking resistance and the sealing strength described above. In particular, it greatly affects the seal strength. For this purpose, it is preferable to avoid excessive kneading in the extrusion process of film formation.

  In this invention, it is preferable to implement on the following extrusion conditions. Extrusion process temperature: 230-280 ° C., screw length / screw diameter of extruder screw: 20-50, extruder screw rotation speed: 30-60 rpm, supply pressure to die 10-16 Mpa, extruder outlet pressure: 29-36 Mpa .

  The extruded film of the present invention can be subjected to surface treatment such as corona discharge treatment or flame treatment by a method generally employed industrially.

  In this invention, it is preferable that the ratio of the fallen bag broken bag which evaluated the said food packaging film by the following method is 25% or less, and the seal strength after retort treatment is 38 to 110 N / 15 mm, and 38 to 60 N. More preferably, it is / 15 mm.

  When the sealing strength after the retort treatment is less than 38 N / 15 mm, for example, when used as a sealant film for a packaging bag of retort food, seal leakage due to peeling of the sealing portion due to external force applied to the packaging bag due to impact during storage or transportation Reliability for occurrence prevention is reduced. The higher the seal strength after the retort treatment is, the higher the better. However, as described above, the seal strength after the retort treatment and the above-mentioned bag-breaking bag breaking property are a trade-off phenomenon, and therefore the upper limit of the seal strength after the retort treatment. Is preferably 110 N / 15 mm. Although it is preferable that the seal strength is higher, if it exceeds 110 N / 15 mm, the above described falling bag breaking property may be deteriorated.

The film of the present invention is preferably used as a laminate of a biaxially stretched polyester film and an aluminum foil.
With this configuration, it can be suitably used as a packaging material for retort food represented by retort curry.

  The film of the present invention can also be used as a laminate with a film such as a polyamide biaxially stretched film.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, but may be implemented with appropriate modifications within a scope that can meet the gist of the present invention. These are all included in the technical scope of the present invention.

  The measurement and evaluation methods employed in this specification are as follows.

1. Melt flow rate [MFR]
According to JIS K7210, it was measured by the method of Condition-14 (load 2.16 kg, temperature 230 ° C.).
2. Ratio of xylene soluble part at 20 ° C. (% by mass)
After 5 g of the sample was completely melted in 500 ml of boiling xylene, the temperature was lowered to 20 ° C. and left for 4 hours or more. Thereafter, the precipitate and the solution were separated by filtration, and the filtrate was dried and dried at 70 ° C. under reduced pressure. From the mass of the obtained dried product, the 20 ° C. xylene-soluble part amount was measured, and the ratio was determined.

3. Ethylene content Measured by ¹³ C-NMR method according to the method described on page 616 of Polymer Handbook (published by Kinokuniya, 1995).

4). Haze value Based on JIS-K-6714, it was measured using “Haze Tester J” manufactured by Toyo Seiki Seisakusho.

5). Blocking resistance Overlap the sealant surfaces (seal surfaces) of the MD direction 80 mm x TD direction 120 mm film, and after heat treatment at 50 ° C for 30 minutes, the load per unit area of the sample is 14 by hot pressing the 5 cm x 5 cm part. Adjust to 1 MPa / cm2, apply pressure and pressurize at 50 ° C for 15 minutes. After pressurization, cool this under the condition of 23 ° C x 65% RH, and in accordance with ASTM D-1893, The peel strength (mN / 70 mm) was measured with a tensile tester. Measure with N = 4 and use the average value as data. The smaller this value, the better the blocking resistance.

6). Observation of dispersion state of rubber component A cross section obtained by cutting the evaluation film with a microtome in a direction parallel to the longitudinal direction and perpendicular to the film surface is dyed with ruthenium oxide, and the dyed surface is carbon-deposited to transmit transmission electrons. Observe with a microscope, divide the film in the thickness direction into three equal parts, and the maximum length in the longitudinal direction, the maximum length in the longitudinal direction, and the maximum length in the vertical direction existing in the surface area of 600 μm ² The number of island components having a ratio of 0.2 to 0.2 was taken as a factor. The coefficient of the number was performed using an observation photograph. The observation photograph is taken at a magnification of 5000 times. Apply tracing paper from the top of the photo, and use a 0.5mm mechanical pencil (Zebra's Tapliclip 0.5mm) with a maximum length of 20μm or more in the longitudinal direction. The core is "Ain 0.5mm B To trace. Depending on the cutting method, there may be streaks or lines on the cut surface, which are ignored. Obtained from the traced one.

7). Evaluation of anti-drop bag breaking resistance In advance, a polyester adhesive was applied to a corona-treated surface (48 mN / m or more) of a 12 μm biaxially stretched polyester film (E5100 manufactured by Toyobo Co., Ltd.). A laminate of 5 μm aluminum foil (manufactured by Sumi Light Aluminum Foil Co., Ltd., for food packaging (for retort use)) and aged at 40 ° C. for 5 days is prepared.
A polyester adhesive is applied to the aluminum foil surface of the laminate, and the corona treatment of the 70 μm-thick polypropylene resin film for corona treatment (wet tension of 48 mN / m or more) is applied to the coated surface. The surface of the agent was laminated so as to be in contact with each other, and a laminate film was obtained by aging at 40 ° C. for 5 days.
Both of the polyester-based adhesive and the catalyst used in the production of the laminate film are TM590 and CAT56 manufactured by Toyo Morton Co., Ltd. Both were applied by the following method.
TM590: 15 kg, CAT56: 2.4 kg, and ethyl acetate 25.3 kg are mixed and sufficiently stirred to make a uniform liquid, and the time is adjusted to 12.7 seconds with Zahn cup # 3. (Equivalent to 25% non-volatile content) Using this solution, using a 1000 coating test machine UCT-2500 manufactured by Musashino Machine Design Office Co., Ltd., coated with a 100 l × 90 μm / inch gravure roll, dried at 80 ° C., It is applied so that the solid content is 3 g / m ² .
The laminate film prepared by the above method was formed into a bag under the following conditions using a test sealer (product number: custom-made product, LOT: A56430, DATE: 670670) manufactured by Seibu Kikai Co., Ltd.
After the temperature of the bar reaches 270 ° C. in advance, the blanking is performed 30 times or more, and the lower bar is heated. Seal temperature: 270 ° C. × 2 kg × 1 second, cooling bar: water temperature × 2 kg X Perform in 1 second. After the seal is struck, it is always performed once before the next seal is struck. In this way, a bag sealed on three sides of 130 mm × 165 mm (sealing width: 5 mm) was produced.
200 g of water was put into the bag, and the entire surface was sealed by impulse sealing under the conditions of a vacuum level of 90%, a sealing time of 2 seconds, and a cooling time of 1 second using a product made by Tosei Corporation (TOSPACK V-602G-2). Make a water-filled bag.
The water-filled bag was treated with a hot water retort treatment machine (RCS-60SPXTG) manufactured by Nisaka Manufacturing Co., Ltd. at a pressure of 0.2 MPa at 120 ° C. for 30 minutes (condition: temperature increase 30 ° C. → 120 ° C .: 10 minutes) 120 ° C .: 30 minutes, cooling 120 => 30 ° C .: 10 minutes), and the retort treatment was performed. The water-filled bag subjected to the retort treatment is packed in a cosmetic box having a longitudinal direction of 160 mm, a lateral direction of 130 mm, and a thickness direction of 20 mm, and further, the cosmetic box is composed of one longitudinal direction, three lateral directions, and 12 depth directions. Collected and packed in a collection box. After storing it at 5 ° C for 24 hours or more, from the height of 1.6m at room temperature (from the concrete floor to the bottom of the box packed and packed), the vertical direction of the vanity box is the falling direction, and the top and bottom are alternated Instead of dropping 10 times continuously, find the percentage of bags torn. It carries out by n = 3 and displays it as an average value.
The evaluation criteria were as follows.
(Double-circle): The ratio of the torn bag is 10% or less,
○: Ratio of torn bags is 11 to 20% ×: Ratio of torn bags exceeds 20%

8). Seal strength after retort treatment The seal part of the water-filled bag retort-treated by the above method is cut to a width of 50 mm in the vertical direction and a width of 15 mm, and in accordance with JIS K7127-1989, test speed H: speed of 200 mm / min Measure the seal strength with. As the measuring device which measured each side of the bag with n = 5 and displayed the average value, a universal tensile tester TENSILON / STM-T-50BT manufactured by Toyo Baldwin Co., Ltd. was used.

Example 1
0.05% by mass of Irgafos 168 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a phosphorus-based antioxidant and 0 of Irganox 1010 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a phenolic antioxidant Block copolymerized polypropylene resin containing 20% by mass of ethylene and 7% by mass of 20 ° C. xylene solubles (MFR = 3.0 g / 10 min, WFS 5293-22 manufactured by Sumitomo Chemical Co., Ltd.) ) 86% by mass of ethylene-propylene copolymer resin-based thermoplastic elastomer containing 0.05% by mass of Irganox 1076 (manufactured by Ciba Specialty Chemicals Co., Ltd.) (MFR = 0.7 g / 10 min, Mitsui Chemicals) P0680) 12 parts by mass, 4% by mass of ethylene random Masterbatch resin (Sumitomo Chemical Co., Ltd. MA180, MFR: 10 g / 10) containing 5% by mass of polymerizer (melting point: 142 ° C.) and 5% by mass of a phosphite-based antioxidant, Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.) Min) Masterbatch resin in which 5% by mass of a randomizer GS (manufactured by Sumitomo Chemical Co., Ltd.), an acrylate-based antioxidant, is blended with 1 part by mass of a polypropylene random copolymer resin (melting point 142 ° C.) having an ethylene amount of 4% by mass. (MA181 manufactured by Sumitomo Chemical Co., Ltd., MFR: 10 g / 10 min) 1% by mass was melt-extruded with a T-die film forming machine to obtain an unstretched film having a thickness of 70 μm at a cooling roll temperature of 55 ° C. The extruder screw is a single layer type with L / D = 29. The number of revolutions of the extruder was 55 rev / min, the die was flexible, a hanger coat type, and a single layer die with a die width of 4550 mm was used for film formation. The extruder temperature was set to 230 ° C on the hopper inlet side, 235 ° C on the extruder outlet side, and the die temperature was set to 240 ° C for all.
The results are shown in Table 1.
The food packaging film obtained in this example had good properties with all the properties shown in Table 1 and high quality.

(Comparative Example 1)
In the method of Example 1, the blending of the ethylene / propylene copolymer resin-based thermoplastic elastomer (MFR = 0.7 g / 10 min, Mitsui Chemicals, P0680) was canceled, and the block copolymerized polypropylene resin blending amount was A food packaging film of Comparative Example 1 was obtained in the same manner as in Example 1 except that the content was changed to 98 parts by mass. The results are shown in Table 1.
The film for food packaging obtained in Comparative Example 1 was inferior in dropping bag resistance and low quality.
The food packaging film obtained in Example 2 had the same characteristics as the food packaging film obtained in Example 1 and was of high quality.

(Comparative Example 2)
In the method of Example 1, an ethylene / propylene copolymer resin-based thermoplastic elastomer (MFR = 0.7 g / 10 min, manufactured by Mitsui Chemicals, Inc., P0680) was used in an amount of 20% by mass, and block copolymerized polypropylene. A food packaging film of Comparative Example 2 was obtained in the same manner as in Example 1 except that the resin content was changed to 78% by mass. The results are shown in Table 1.
Since the food packaging film obtained in this Comparative Example 2 has a large amount of elastomer, the amount of soluble part at 20 ° C. xylene increases, and the amount of polypropylene that contributes to the sealing strength is reduced although the drop-off bag breaking resistance is improved. The seal strength after retort treatment was low and the quality was low.

(Comparative Example 3)
In the method of Example 1, a master batch resin obtained by blending a polypropylene random copolymer resin (melting point 142 ° C.) having an ethylene amount of 4% by mass with a phosphite antioxidant Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.). (Master Sumitomo Chemical Co., Ltd., MA180, MFR = 10 g / min) and Masterbatch resin (Sumitomo Chemical Co., Ltd. MA181, MFR = 10 g / M), blended with Sumitizer GS (manufactured by Sumitomo Chemical Co., Ltd.) which is an acrylate antioxidant. The food packaging film of Comparative Example 3 was obtained in the same manner as in Example 1 except that the blending of (min) was stopped and the blending amount of the block copolymer polypropylene resin was changed to 88% by mass. The results are shown in Table 1.
The film for food packaging obtained in this Comparative Example 3 has no post-added antioxidant, so the resin deteriorates, and the surface area of the polypropylene that contributes to the seal strength is reduced. Therefore, the seal strength after retort treatment is low and the quality is low. Met. Moreover, blocking resistance was also inferior to the film for food packaging obtained in Example 1.

(Comparative Example 4)
In the method of Example 1, a food packaging film of Comparative Example 4 was obtained in the same manner as in Example 1 except that the extruder screw rotation speed was changed to 75 rotations / minute. The results are shown in Table 1. Although the food packaging film obtained in Comparative Example 4 has added an antioxidant, the share deterioration is severe, and the surface area of polypropylene that contributes to the seal strength is reduced, so the seal strength after retort treatment is low and the quality is low. Met. Moreover, blocking resistance was also inferior to the film for food packaging obtained in Example 1.

(Example 2)
In the method of Example 1, Irgafos 168 (Ciba Specialty Chemicals Co., Ltd.) using block copolymerized polypropylene resin (MFR = 3.0 g / 10 min, WFS 5293-22 manufactured by Sumitomo Chemical Co., Ltd.) as a phosphorus-based antioxidant. Made of Irganox 1010 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a phenolic antioxidant and containing 0.20% by mass of ethylene, 5% xylene soluble part Is replaced by 10% by mass of block copolymerized polypropylene resin (WFS 5293-26: manufactured by Sumitomo Chemical Co., Ltd., MFR = 3.1 g / 10 min), and the blending ratio is 81% by mass, and ethylene / propylene copolymer resin. Thermoplastic elastomer (MFR = 0.7 g / 10 min, manufactured by Mitsui Chemicals, P0680) Except for changing the total amount to 17 mass%, to obtain a food packaging film of Example 2 in the same manner as in Example 1. The results are shown in Table 1.

(Examples 3, 4, and 5)
In the method of Example 1, the blending amounts of ethylene / propylene copolymer resin-based thermoplastic elastomer (MFR = 0.7 g / 10 min, manufactured by Mitsui Chemicals, Inc., P0680) were 7, 9, and 14% by mass, respectively. As described above, food packaging films of Examples 3 to 5 were obtained in the same manner as in Example 1 except that the blending amount of the block copolymerized polypropylene resin was changed so that the total resin amount was 100% by mass. The results are shown in Table 1.
The food packaging film obtained in these Examples is excellent in both the fall bag resistance and the sealing strength after the retort treatment in the same manner as the food packaging film obtained in Example 1. there were.

(Example 6)
In the method of Example 1, 0.15% by mass of Irganox 1010 (manufactured by Ciba Specialty Chemicals, Inc., molecular weight 1178) as a phenolic antioxidant and 0.05% by mass of Sumizer GP (manufactured by Sumitomo Chemical Co., Ltd.) Block copolymer polypropylene resin (MFR = 3.0 g / 10 min, WFS 5293-39, manufactured by Sumitomo Chemical Co., Ltd.) having an ethylene content of 7% by mass and a 20 ° C. xylene soluble part of 15% by mass 87. 4 mass%, ethylene / propylene copolymer resin-based thermoplastic elastomer (MFR = 0.7 g / 10 min) containing 0.05 mass% of Irganox 1076 (manufactured by Ciba Specialty Chemicals Co., Ltd., molecular weight 531), (Mitsui Chemicals, P0680) 12% by mass, 4% by mass of ethylene Master batch resin (MA181 manufactured by Sumitomo Chemical Co., Ltd., MFR: 10 g / 10 min) 0.6 mass containing 5% by mass of acrylate antioxidant SUMILIZER GS (manufactured by Sumitomo Chemical Co., Ltd.) in a dam copolymer resin. A food packaging film of Example 6 was obtained in the same manner as in Example 1 except that it was made a part. The results are shown in Table 1.
The film for food packaging obtained in Example 6 is slightly inferior in sealing strength after retorting treatment than the film for food packaging obtained in Example 1, but has a falling bag breakage resistance and sealing strength after retorting treatment. It was compatible and high quality.

  According to the film for food packaging of the present invention, it has excellent heat resistance, sealing property, bag-breaking resistance and food hygiene, and simultaneously satisfies the characteristics required as a food packaging film suitable for retort processing. In particular, the balance between anti-breaking bag resistance and seal strength after retort treatment is improved, and both properties are compatible, so when used as a constituent material for packaging bags for retort foods, excellent retort treatment In addition, the reliability of durability against external forces such as impact of the packaging bag during storage and transportation of food after retorting is improved. Therefore, since it can be used suitably as a constituent material for food packaging films, particularly retort food packaging bags, it greatly contributes to the industry.

Claims (3)

The film mainly composed of a propylene-ethylene block copolymer contains at least a phenol-based antioxidant, a phosphorous acid-based antioxidant, and an acrylate-based antioxidant. 20-30% by mass, the cut section of the film cut in a direction parallel to the longitudinal direction and perpendicular to the film surface is dyed with ruthenium oxide, the dyed surface is carbon-deposited and observed with a transmission electron microscope The maximum length in the longitudinal direction existing in an area of 600 μm ² in actual area is 20 μm or more, and the ratio of the maximum length in the longitudinal direction to the maximum length in the longitudinal direction and the maximum length in the vertical direction is 0.2 or more. The film for food packaging characterized by the ratio of a certain island component being 20% or more.   The ratio of falling bag broken bags evaluated by the method described in the specification of the food packaging film is 20% or less, and the sealing strength after retorting is 38 to 110 N / 15 mm. The film for food packaging according to 1.   Resin composition in which 85 to 95 parts by mass of a polypropylene block copolymer resin whose main component is a propylene-ethylene block copolymer having a 20 ° C. xylene soluble part of 5 to 20% by mass and 5 to 15 parts by mass of a thermoplastic elastomer The food packaging film according to claim 1, wherein the food packaging film is a product.