JP2006188600A - Polyolefin film for retort - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyolefin film for retort maintaining impact resistance comparable to that of a conventional film for retort and having excellent heat sealing suitability, transparency and blocking resistance after retort and suppressing deterioration of flavor of contents after the retort treatment. <P>SOLUTION: The polyolefin film for retort is characterized as follows. The polyolefin film for retort is composed of 90-95 pts.wt. of polypropylene or a propylene-α-olefin random copolymer polymerized by using a metallocene catalyst and 5-10 pts.wt. of an olefinic elastomer. An additive, as necessary, is added and the peak area sum total of a residual volatile component per 1 g of the film is ≤200 pA×s/g. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyolefin film for retort.

  In recent years, with the change of eating habits, retort foods that are simple and can save the labor of cooking are frequently used. This retort food is prepared by pre-cooked food in a bag, sealed and then pressurized and heat sterilized. Store it at room temperature or refrigerated / frozen and heat it in hot water when needed. The contents can be taken out and used for meals.

  For this reason, as a film used for a bag of retort food, it has heat resistance that can withstand pressurization and heat sterilization after filling and sealing of food, and has excellent transparency and blocking resistance as film properties Is desirable. Also, in general, retort food bags are often used by laminating two or more layers using nylon film, polyester film, etc., and are thicker than general packaging films, making them suitable for heat sealing. Since it is inferior, a low temperature heat seal is preferable. In addition, when displaying the contents, it is necessary to have excellent transparency, but a balance with blocking resistance is important. Furthermore, the thing excellent in the impact resistance which does not break in transportation and conveyance is desired.

  As such a film for retort, for example, a thermoplastic elastomer is blended with a mixed resin composed of a polyolefin mainly composed of a propylene / ethylene block copolymer and a propylene copolymer. There is a polyolefin film for retort in which the blending ratio and the like of these components are specified within a specific range (see Patent Document 1). And a film formed from a composition comprising a propylene polymer component, a propylene-α-olefin random copolymer component, and a random copolymer component of ethylene and an α-olefin having 4 or more carbon atoms. There is a film for retort food packaging in which the blending ratio and the like are defined within a specific range (see Patent Document 2).

By the way, in the recent food industry, there is a demand for light-tasting foods in which the amount of various seasonings used is reduced, and this tendency is the same for retort foods. For this reason, when the volatile component derived from the film for retorts transfers to the foodstuff which is a content, the deterioration of the flavor of the content by the volatile component becomes a problem. However, in the conventional retort film, the deterioration of the flavor of the contents has not been improved yet, and even if it is light, it can be kept delicious without deteriorating the flavor of the contents. A retort film was desired.
Japanese Patent Laid-Open No. 9-248885 JP 2003-96251 A

  The present invention has been made in view of the above points, maintains impact resistance, is excellent in heat sealability after retort, transparency, and blocking resistance, and deteriorates the flavor of the contents after retort treatment. A polyolefin film for retort to be suppressed is provided.

  That is, the invention of claim 1 comprises 90 to 95 parts by weight of a polypropylene or propylene-α-olefin random copolymer polymerized using a metallocene catalyst, and 5 to 10 parts by weight of an olefin elastomer. According to the above, the present invention relates to a polyolefin film for retort characterized in that the total peak area of residual volatile components per gram of film measured by the following measuring method is 200 pA · s / g or less.

  In the measurement method, a sample obtained by cutting the polyolefin film is sealed in a 20 mL vial, heated at 100 ° C. for 15 minutes, 1 mL of the gas in the vial is extracted by a headspace sampler, and subjected to gas chromatography. A helium gas is used as a carrier gas and a volatile component is detected at a carrier gas flow rate of 2.0 mL / min. The total peak area is obtained by calculating and summing the peak areas from the peaks of volatile components detected during a retention time of 0 to 35 minutes.

  In the invention of claim 2, the melting point of the polypropylene or propylene-α-olefin random copolymer is 130 to 145 ° C, and the MFR at 230 ° C is 0.5 to 10 g / 10 min. It relates to the polyolefin film for retort described.

The invention according to claim 3 is the ethylene-α having the density of 0.86 to 0.90 g / cm ³ and the MFR at 190 ° C. of 0.1 to 10 g / 10 min in the olefin elastomer. The polyolefin film for retort according to claim 1, which is a olefin random copolymer.

  According to the polyolefin film for retort of the invention of claim 1, while exhibiting the same impact resistance as that of the conventional product, it has excellent heat sealability after retort, transparency and blocking resistance, and the flavor of the contents after retort treatment. Can be prevented.

  According to the invention of claim 2, in the invention of claim 1, the melting point of the polypropylene or propylene-α-olefin random copolymer is 130 to 145 ° C, and the MFR at 230 ° C is 0.5 to 10 g. / 10 minutes, it is possible to obtain a film that is excellent in low-temperature heat-sealing properties and can suppress fusion between films after semi-retort treatment, and the film can be easily formed.

According to the invention of claim 3, in the invention of claim 1 or 2, the olefin elastomer has a density of 0.86 to 0.90 g / cm ³ and an MFR at 190 ° C. of 0.1. Since it is an ethylene-α-olefin random copolymer of 1 to 10 g / 10 min, it is possible to obtain a film having good blocking resistance and excellent impact resistance, and also easily forming the film. Can do.

  The polyolefin film for retort of the present invention comprises 90 to 95 parts by weight of a polypropylene or propylene-α-olefin random copolymer polymerized using a metallocene catalyst, and 5 to 10 parts by weight of an olefin elastomer and is necessary. Depending on the case, additives are added. As for the polypropylene or propylene-α-olefin random copolymer, a propylene-α-olefin random copolymer such as a propylene-ethylene random copolymer is suitably used as disclosed mainly in the examples described later. This polyolefin film for retort is used as a semi-retort (sterilization treatment at around 120 ° C.) type.

  As defined in the invention of claim 2, the propylene-α-olefin random copolymer has a melting point within the range of 130 to 145 ° C and an MFR at 230 ° C of 0.5 to 10 g. / 10 minutes is preferred. When the melting point is approximately 135 ° C., a film having good resistance to semi-retort such as fusion and excellent in low-temperature heat sealability can be obtained. Moreover, if MFR is 0.5-10 g / 10min, it is supposed that it can be set as a film with easy shaping | molding.

  The propylene-α-olefin random copolymer used in the present invention is polymerized using a metallocene catalyst. The metallocene-based catalyst is a compound that is coordinated with a transition metal having the following structure, for example, represented by the chemical formula (1). In Chemical Formula 1, Q is a binding group that bridges two conjugated five-membered ring ligands, and examples thereof include a divalent hydrocarbon group having 1 to 20 carbon atoms, a silylene group, and an oligosilylene group. M is a metal atom selected from titanium, zirconium, and hafnium, and X and Y are a hydrogen atom bonded to M, a hydrocarbon group having 1 to 20 carbon atoms such as a halogen atom, a methyl group, an isobutyl group, and a phenyl group, oxygen And a hydrocarbon group having 1 to 20 carbon atoms containing nitrogen or silicon. R represents hydrogen, a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a phenyl group, a naphthyl group, a butenyl group, a butadienyl group, etc., a hydrocarbon group having 1 to 20 carbon atoms, a halogen atom, Methoxy group containing halo, silicon, nitrogen, oxygen, boron, phosphorus, ethoxy group, phenoxy group, trimethylsilyl group, diethylamino group, diphenylamino group, pyrazolyl group, indolyl group, dimethylphosphino group, diphenylphosphino group, Examples thereof include a diphenylboron group and a dimethoxyboron group. For the metallocene catalyst, for example, JP-A-2003-201379 is referred to.

  Polypropylene or propylene-α-olefin random copolymer polymerized using a metallocene catalyst is narrower in molecules obtained by polymerization than a polymer polymerized by a conventional titanium Ziegler-Natta catalyst. It is known to show a molecular weight distribution. For this reason, it is estimated that the obtained film will be excellent in heat sealing properties such as a foreign matter seal. In addition, a polymer polymerized using a metallocene catalyst can be obtained in spite of a low melting point because there are few components having low stereoregularity compared to a polymer obtained using a conventional Ziegler-Natta catalyst. The film is preferable because it is less sticky and has excellent blocking resistance.

  Examples of the polymerization method include a slurry method using an inert solvent in the presence of the metallocene catalyst, a gas phase method using substantially no solvent, a solution method, or a bulk polymerization method using a polymerization monomer as a solvent. .

  In addition, even if it exists in a polypropylene, since properties, such as MFR and melting | fusing point, are assumed similarly to the case where a propylene-alpha-olefin random copolymer is used, it is anticipated that it is suitable for use.

  Here, the propylene-α-olefin random copolymer is a copolymer of propylene and an α-olefin having 2 to 10 carbon atoms other than propylene. Examples of the α-olefin include ethylene, 1-butene, 3-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene and 1-octene. Can be mentioned. These may be used alone or in combination of two or more.

Next, the olefin elastomer used in the polyolefin film for retort has a density of 0.86 to 0.90 g / cm ³ and an MFR at 190 ° C. of 0.1 to 0.1 as specified in the invention of claim 3. An ethylene-α-olefin random copolymer of 10 g / 10 min is preferably used. This is because when the density is 0.90 g / cm ³ or more, the impact resistance of the film is inferior, and when it is less than 0.86 g / cm ³ , there are many sticky components, and the blocking resistance of the film may be deteriorated. When the MFR at 190 ° C. is 0.1 to 10 g / 10 minutes, the film can be easily molded and has excellent impact resistance at low temperatures. The ethylene-α-olefin random copolymer is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, and examples thereof include an ethylene-propylene random copolymer and an ethylene-butene random copolymer. It is done. These may be used alone or in combination of two or more.

  The olefin-based elastomer is added in an amount of 5 to 10 parts by weight with respect to 90 to 95 parts by weight of the above-mentioned polypropylene or propylene-α-olefin random copolymer. When the amount of the olefin elastomer added is less than 5 parts by weight, the impact resistance may be insufficient. On the other hand, when the amount of the olefin-based elastomer added is more than 10 parts by weight, physical properties such as a decrease in heat seal strength after retorting are pointed out.

  If necessary, appropriate additives such as a lubricant, an antistatic agent, an antioxidant, a neutralizing agent, and an antiblocking agent are added to the polyolefin film for retort.

  The polyolefin film for retort is characterized in that the total peak area of residual volatile components per gram of film measured by the following measurement method is 200 pA · s / g or less. The measurement method is that a sample obtained by cutting the polyolefin film is sealed in a 20 mL vial, heated at 100 ° C. for 15 minutes, and then 1 mL of the gas in the vial is collected using a headspace sampler. Extracted and loaded into gas chromatography, helium gas is used as the carrier gas, and the carrier gas flow rate is 2.0 mL / min to detect volatile components. The total peak area is obtained by calculating and summing the peak areas from the peaks of volatile components detected during a retention time of 0 to 35 minutes.

  When the inventors manufactured a retort food using a film having a total peak area of residual volatile components per gram of film of 200 pA · s / g or less, the flavor of the contents deteriorates due to the volatile components derived from the film. It was verified that it can be suppressed. At the same time, the inventors also revealed that when the total peak area of residual volatile components per gram of film exceeds 200 pA · s / g, the flavor of the contents deteriorates due to the volatile components derived from the film. . These can be understood from examples described later.

  Next, the production of the polyolefin film for retort of the present invention will be described. The above-mentioned polypropylene or polypropylene-α-olefin random and the olefin-based elastomer are put into known mixers (tumblers, Henschel mixers, etc.) in parts by weight of the predetermined blending ratio, and the above-mentioned additives are added as necessary. Add and dry blend. The obtained mixture is supplied to a known extruder, melted at a temperature of 200 to 300 ° C., extruded from a T die provided at the tip of the extruder, brought into contact with a cooling roll, and cooled and solidified. The thickness of the obtained polyolefin film for retort is 20-150 micrometers.

  Moreover, the polyolefin film for retort of this invention is surface-treated as needed, in order to improve the adhesiveness, when laminating with a nylon film, a polyethylene terephthalate film, etc. Examples of the surface treatment method include corona discharge treatment, flame treatment, and plasma treatment.

  The polyolefin film for retort of the present invention thus obtained can be used as a retort film by being laminated with a nylon film, a polyethylene terephthalate film or the like. Examples of the laminating method include a method of dry laminating via a urethane adhesive or the like.

Next, the polyolefin film for retort of Examples 1 and 2 and Comparative Examples 1 to 3 of the present invention was made as a prototype, and the transparency (haze), dirt impact strength (J), and blocking strength (N / 4 cm ² ) of each film. ), Heat seal strength (N / 15 mm), heat seal temperature (° C./3N), residual volatile components, fusion strength (N / 3 cm ² ), and taste (sensory evaluation) of the contents.

[transparency]
The haze measured using a digital haze meter (manufactured by Nippon Denshoku Industries Co., Ltd.) by the method described in JIS K 7105 (1997) was used.

[Dirt impact strength]
Using a dirt impact tester with a cryogenic bath (manufactured by Toyo Seiki Seisakusho), the amount of work required for penetration fracture was measured. That is, the polyolefin films of Examples and Comparative Examples were fixed horizontally by a fixing device, and the dirt (hemispherical metal penetrating part) whose mass was adjusted was dropped to destroy and penetrate the film, after passing through the film. The dart passing speed (V ₁ ) and the dart passing speed (V ₀ ) at the same point as the V ₁ measurement point when the dart was dropped in the absence of film were measured and shown in the following formula 1. The breaking energy (J) of the film was determined by a mathematical formula. M is the weight of the dirt.

[Blocking strength]
The non-corona-treated surfaces of the polyolefin films of Examples and Comparative Examples were overlapped, and a load of 1N was applied to 4 cm ² of the film and left at 40 ° C. for 24 hours. Then, “Autograph AGS-500NG” manufactured by Shimadzu Corporation was used. Shear peel strength was measured. The peel strength is a value obtained by measuring the force with which a film after applying a load shears at a tensile speed of 200 mm / min of a tensile tester.

[Heat seal strength]
The polyolefin films of Examples and Comparative Examples are dry-laminated with a nylon film having a thickness of 15 μm, and the polyolefin film surfaces of the obtained laminated films of Examples and Comparative Examples are overlapped, and a heat seal tester (manufactured by Tester Sangyo Co., Ltd.) is used. Then, after heat-sealing at a seal pressure of 0.3 MPa, a seal time of 0.5 seconds, an upper seal bar of 160 ° C. and a lower seal bar of 50 ° C., cut to a width of 15 mm and use “Autograph AGS-500NG” manufactured by Shimadzu Corporation The peel strength was measured. The peel strength is a value obtained by measuring the force with which the film after heat sealing peels off at a tensile speed of 200 mm / min (T peel test). Moreover, the 15 mm width cut piece after heat sealing produced similarly was retorted, and peel strength was measured similarly. The retort treatment in this example refers to a treatment heated at 120 ° C. for 30 minutes using “Retort Food Autoclave SR240” manufactured by Tommy Seiko Co., Ltd.

[Heat seal temperature]
The polyolefin films of Examples and Comparative Examples obtained as described above were dry-laminated with a nylon film having a thickness of 15 μm, and the polyolefin film surfaces of the obtained laminate films were overlapped with each other, and a thermal inclination tester manufactured by Toyo Seiki Seisakusho was used. Used, after heat-sealing with a sealing pressure of 0.34 MPa and a sealing time of 1.0 second, cut to a width of 15 mm, and measure the heat-seal strength as described above using “Autograph AGS-500NG” manufactured by Shimadzu Corporation The temperature at which the seal strength becomes 3N was determined.

[Residual volatile components]
The measurement was performed by gas chromatography (“HP6890” manufactured by HEWLETTPACKARD, column “HP-Wax” manufactured by HEWLETTPACKARD) under the following conditions. Samples obtained by cutting the polyolefin films of Examples and Comparative Examples were put in 20 mL vials and sealed, heated at 100 ° C. for 15 minutes, and then 1 mL of gas in the vials was converted into a headspace sampler (“HP7694” manufactured by HEWLETTPACKARD). ) And was loaded into a gas chromatography and measured. Helium gas was used as a carrier gas, and a volatile component was detected at a carrier gas flow rate of 2.0 mL / min. The total peak area (pA · s / g) is obtained from the peak of the volatile component detected during the retention time from 0 to 35 minutes, and the area of the peak is calculated and summed. The value was divided by the weight (g). That is, the total peak area is obtained by adding the areas surrounded by the approximate baseline and each peak connected by a straight line connecting the start point and end point of each peak, and is the weight (g) of the sample used. The total peak area per gram was determined by dividing.

[Fusion strength]
The polyolefin films of Examples and Comparative Examples were dry laminated with a nylon film having a thickness of 15 μm, the polyolefin film surfaces of the obtained laminated films of Examples and Comparative Examples were overlapped, and sealed with “Impulse Sealer VG400” manufactured by Fuji Impulse. Sealing was performed for 1.5 seconds to make a three-sided bag of 10 cm × 10 cm. After degassing the three-sided bag for 5 seconds, the upper portion of the opened bag was sealed with the “impulse sealer VG400” for a sealing time of 1.5 seconds, and after the retort treatment, the shear peel strength of the fused portion was measured.

[Taste of contents]
After filling the three-side bags of Examples and Comparative Examples prepared as described above with 30 mL of natural water made by Suntory, the upper portion of the three-side bag was sealed with the “impulse sealer VG400” for a sealing time of 1.5 seconds. Then, retort treatment was performed. And the smell and taste of natural water were evaluated according to the following criteria based on the sensuality of 10 panelists. The target of comparison is non-retort natural water.
1 point: unbearable odor 2 points: strong odor 3 points: odor 4 points: not very odor 5 points: no odor at all

Example 1
94 parts by weight of a propylene-ethylene random copolymer polymerized with a metallocene catalyst as a propylene-α-olefin copolymer at a melting point of 135 ° C. and 230 ° C. of MFR 7.0 g / 10 min, and a pellet of ethylene as an olefin elastomer 6 parts by weight of a butene copolymer (“Tuffmer A4085” manufactured by Mitsui Chemicals, Inc., density 0.88 g / cm ³ , MFR at 190 ° C. is 3.6 g / 10 min) is dry-blended with a mixer, and this is sent to an extruder. Supplied, melted at 230 ° C., extruded from a T-die having a width of 70 mm, formed into a sheet, wound around a 35 ° C. cooling roll and cooled and solidified to obtain a polyolefin film for retort of Example 1 having a thickness of 60 μm. .

(Example 2)
The same treatment as in Example 1 was performed except that 90 parts by weight of the propylene-ethylene random copolymer used in Example 1 and 10 parts by weight of the ethylene-butene copolymer of Example 1 were used. A polyolefin film for retort was obtained.

(Comparative Example 1)
The same treatment as in Example 1 was performed except that 85 parts by weight of the propylene-ethylene random copolymer used in Example 1 and 15 parts by weight of the ethylene-butene copolymer of Example 1 were used. A polyolefin film for retort was obtained.

(Comparative Example 2)
Instead of the propylene-ethylene random copolymer used in Example 1, a propylene-ethylene random copolymer polymerized with a Ziegler-Natta catalyst and having a melting point of 142 ° C. and an MFR of 6.5 g / 10 min at 230 ° C. ( A polyolefin film for retort of Comparative Example 2 was obtained in the same manner as in Example 1 except that 94 parts by weight) was used.

(Comparative Example 3)
Instead of the propylene-ethylene random copolymer used in Example 1, a propylene-ethylene random copolymer polymerized with a Ziegler-Natta catalyst and having a melting point of 137 ° C. and MFR at 230 ° C. of 7.0 g / 10 min was used. A polyolefin film for retort of Comparative Example 3 was obtained in the same manner as in Example 1 except that it was used.

  Moreover, about Example 1 and 2 and Comparative Examples 1-3, the result of having investigated the transparency of each film, dart impact strength, blocking strength, heat seal strength, heat seal temperature, fusion strength, and the taste of the contents and The total peak area of residual volatile components is shown in Table 1. Regarding heat seal strength, heat seal temperature, and fusion strength, each film of Examples 1 and 2 and Comparative Examples 1 to 3 was obtained by dry laminating each with a 15 μm thick nylon film and a urethane adhesive. It measured using the laminate film. The total peak area of residual volatile components was calculated for Example 1 from the gas chromatography analysis chart shown in FIG. Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were calculated from the analysis charts shown in FIG. 2, FIG. 3, FIG. 4, and FIG. The value of the taste of the contents represents the average value of 10 panelists.

  As shown in Table 1 above, the polyolefin film for retort of the example has substantially the same impact resistance (dirt impact strength) as compared with the film of the comparative example, and is excellent in heat sealability after retort. It is obvious that the flavor of the contents can be prevented from deteriorating due to the volatile component derived from it, and it is clear that it is suitable as a film for retort. Moreover, it turns out that the film of an Example is excellent also in transparency and blocking resistance.

2 is an analysis chart of gas chromatography according to Example 1. FIG. 3 is an analysis chart of gas chromatography according to Example 2. FIG. 6 is an analysis chart of gas chromatography according to Comparative Example 1. 6 is an analysis chart of gas chromatography according to Comparative Example 2. 10 is an analysis chart of gas chromatography according to Comparative Example 3.

Claims (3)

It consists of 90 to 95 parts by weight of a polypropylene or propylene-α-olefin random copolymer polymerized using a metallocene catalyst, and 5 to 10 parts by weight of an olefin elastomer, and additives are added as necessary. A polyolefin film for retort, wherein the total peak area of residual volatile components per gram of film measured by the following measurement method is 200 pA · s / g or less.
Measurement method: A sample obtained by cutting the polyolefin film is sealed in a 20 mL vial, heated at 100 ° C. for 15 minutes, 1 mL of gas in the vial is extracted by a headspace sampler, and loaded into a gas chromatography. Then, helium gas is used as the carrier gas, and the volatile component is detected at a carrier gas flow rate of 2.0 mL / min. The total peak area is obtained by calculating and summing the peak areas from the peaks of volatile components detected during a retention time of 0 to 35 minutes.   2. The polyolefin film for retort according to claim 1, wherein the polypropylene or the propylene-α-olefin random copolymer has a melting point of 130 to 145 ° C. and an MFR at 230 ° C. of 0.5 to 10 g / 10 min. The olefin elastomer is an ethylene-α-olefin random copolymer having a density of 0.86 to 0.90 g / cm ³ and an MFR at 190 ° C. of 0.1 to 10 g / 10 min. The polyolefin film for retorts according to claim 1 or 2.

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