KR20030025878A - Heat-sealable film and its uses - Google Patents

Abstract

PURPOSE: A film for thermal sealing, a layered film containing the film for thermal sealing and a packed product packed by using the layered film are provided, to improve the blocking resistance, the rigidity and the low temperature impact strength and to reduce the decrease of the thermal sealing strength after heating. CONSTITUTION: The film is prepared from the propylene polymer composition comprising a propylene polymer component, a propylene-α-olefin random copolymer component and an ethylene-α-olefin random copolymer component prepared from ethylene and α-olefin of C4 or more, wherein the mass ratio of the propylene polymer component to the propylene-α-olefin random copolymer component is 80/20 to 95/5, the propylene-α-olefin random copolymer component has an intrinsic viscosity of 2-3.5 dl/g and contains 70-85 wt% of propylene unit, and the ethylene-α-olefin random copolymer component has a density of 0.865-0.910 g/cm3 and its content is 10-30 wt%.

Description

Heat Sealable Film and Uses thereof {HEAT-SEALABLE FILM AND ITS USES}

The present invention relates to a heat sealable film made from a propylene polymer composition, which is suitably used as a packaging material for contents such as retort food. More specifically, the present invention is excellent in blocking resistance, rigidity and low temperature impact resistance, heat sealing strength is not impaired even after heat treatment such as retort sterilization treatment, almost concave and convex and phenomenon on the package It is related with the film used suitably as packaging materials, such as a retort foodstuff which is not. In addition, the present invention relates to a heat-sealing laminated film obtained from the film, which is suitably used as a packaging material for contents requiring heat sterilization treatment such as retort food, medicine, pet food, etc. The contents to be related to a package sealed using this laminated film.

Diverse food cultures include: continued social changes, such as national population aging, the tendency to nuclear family, an increase in the number of employees who leave their families and work in other cities, an increase in the age group where both husbands and wives are usually employed, and the age of marriage As a catalyst for the growth of the market, there is a strong demand for shortening of cooking time and convenience of cooking. Under these circumstances, there is an increasing opportunity for manufacturers to purchase so-called retort foods that are supplied to the market after pre-cooked foods are packaged in hermetically sealed pouches and then subjected to autoclaving. The consumer may soak the retort food pouch in boiling water as needed and restore the heated contents for instant service. This kind of retort food is generally accepted among ordinary consumers as well as those who pursue tradition. Based on the above-mentioned trend, the demand for the packaging material which can collectively package a large quantity of food is increasing.

Since retort food is usually stored at room temperature for a long time, or kept in a cold storage or a frozen storage state, the film used as a packaging material has a heat-seal strength and low temperature so that the package is not broken by the initial damage to the heat-sealed portion. High impact strength is required. From the viewpoint of efficient food quality control, in order to withstand the retort sterilization in a pressurized heating pot maintained at a temperature of 100 to 140 ° C. and also to load the cooked food and seal the pouch in the next step, Sufficient heat resistance and the maintenance of the heat-sealing strength of the heat-sealing portion during the packaging are required.

Films conventionally used for this purpose are films made from blends of propylene polymers and ethylene-α-olefin copolymer rubbers, films made from propylene block copolymers, the propylene block copolymers and ethylene-α-olefin copolymer rubbers. Films prepared from blends of Although this kind of film has good heat resistance and low temperature impact strength, it cannot be said that there is sufficient balance between low temperature impact strength and blocking resistance, and the heat sealing strength tends to be poor after the retort treatment.

In view of preventing the heat seal strength from being reduced to the limit after retort treatment, Japanese Patent Application Laid-Open No. 2000-255012 discloses a propylene-α-olefin block air of 95 to 70% by weight of polypropylene block and 5 to 30% by weight of elastomer block. It is disclosed that the coalescence is used as a heat seal layer. However, films made of propylene-α-olefin block copolymers of elastomeric block units having a propylene content of 30-70 mol%, which are specifically described in this publication, do not have sufficient low-temperature impact strength and are sealed after retort treatment. The strength tends to be lowered. In addition, a rough surface ("orange peeling") appears on the surface of the package and tends to deteriorate in appearance.

Japanese Patent Application Laid-Open No. 2000-119480 discloses propylene-ethylene having an intrinsic viscosity [η] of 1.5 to 2.8 (dl / g) of p-xylene solubles in order to improve low temperature impact resistance, heat sealing strength, heat resistance, etc. of the retort film itself. A composition prepared by adding 1 to 10% by weight of an ethylene-α-olefin copolymer rubber to 90 to 99% by weight of a block copolymer is described. Although the film made from this composition improves the low temperature impact resistance, the blocking resistance is not so good and the effect of suppressing the decrease in the sealing strength after the retort treatment is not very satisfactory.

It is an object of the present invention to provide a heat sealable film suitable for packaging contents requiring heat sterilization treatment, such as retort food.

Another object of the present invention is to have a rigidity and low temperature impact resistance, excellent blocking resistance and heat sealing strength, heat sealing strength is reduced only slightly after heat treatment, to prevent the phenomenon of concave, convex on the surface of the package or It is to provide a heat-sealable film that can be relaxed.

It is another object of the present invention to provide a heat sealable laminated film having the heat sealable film as one layer.

It is still another object of the present invention to provide a package containing a content for which heat sterilization treatment is required, in which the heat sealable film is used.

Other objects, features and advantages of the present invention will become more apparent from the following description.

That is, the present invention relates to a propylene polymer component (A), a propylene-α-olefin random copolymer component (B), and an ethylene-α-olefin random copolymer component (C) prepared from ethylene and an α-olefin having 4 or more carbon atoms. A heat-seal film made from a propylene polymer composition, wherein the composition is

(1) the weight ratio of the propylene polymer component (A) and the propylene-α-olefin random copolymer component (B) is 80/20 to 95/5,

(2) the propylene-α-olefin random copolymer component (B) has an intrinsic viscosity [η] of 2 to 3.5 (dl / g) and contains 70 to 85% by weight of propylene units;

(3) The ethylene-α-olefin random copolymer component (C) has a density of 0.865 to 0.910 (g / cm ³ ) and is composed of 10 to 30% by weight based on the total amount of the composition.

It is preferable that the said propylene polymer composition contains 15-30 weight% of 23 degreeC p-xylene solubles, and 2.5 weight% or less of 50 degreeC hexane solubles. In addition, the propylene polymer composition has a melt flow rate of 2 to 10 (g / 10 minutes) at 230 ° C. and contains 10 to 20% by weight of ethylene units. It is preferable that the melt flow rate in 190 degreeC of the said ethylene-alpha-olefin random copolymer (C) is 0.01-5 (g / 10min). The film is excellent in low temperature impact resistance, maintains high heat sealing strength, and has a good appearance even after exposure to retort treatment, and therefore, the film can be suitably used for packaging contents requiring heat sterilization treatment such as retort food.

The present invention also relates to a heat sealable laminated film in which a base material layer is laminated on one side of the heat sealable film, and the laminated film is suitable for packing contents such as retort food.

In addition, the present invention relates to a package containing a retort food, produced by heat-sealing the heat-sealing film and the contents packaged therein.

Detailed description of preferred embodiments

The heat-sealable film of this invention, the laminated | multilayer film containing this film as one layer, and the said laminated | multilayer film are used, and the packaged article containing the content which requires heat sterilization process is explained in full detail one by one.

Propylene Polymer Composition

The heat-sealing film of the present invention is a raw material of a propylene polymer composition basically composed of a propylene polymer component (A), a propylene-α-olefin random copolymer component (B), and an ethylene-α-olefin random copolymer component (C). It is a film obtained by molding.

The composition ratio (% by weight) of the propylene polymer component (A) and the propylene-α-olefin random copolymer component (B), that is, (A) / (B) is 80/20 to 95/5, preferably 83/17 ˜90 / 10. The relative weight of the ethylene-α-olefin random copolymer component (C) with respect to the total composition is 10-30% by weight, preferably 11-23% by weight, more preferably 12-20% by weight. Films prepared from the polymer compositions described above have good low temperature impact resistance, stiffness, initial heat seal strength and post heat treatment heat seal strength. The film thus obtained is particularly suitable for packaging contents requiring heat sterilization treatment such as retort food.

According to ASTM D-1238 of this composition, the melt flow rate (MFR) measured at 230 ° C. and 2.16 kg load is preferably 2 to 10 (g / 10 minutes), more preferably 2.5 to 8 (g / 10). Min). If the melt flow rate of the said polymer composition is the said range, the film excellent in film formability and excellent in low-temperature impact resistance can be obtained easily. The ethylene unit content of this composition is preferably 10 to 20% by weight, more preferably 12 to 18% by weight.

In the above propylene polymer composition, a composition containing 15-30% by weight of 23 ° C p-xylene soluble content and 2.6% or less of 50 ° C hexane soluble content satisfies hygienic conditions for food use according to FDA standards and the like, and thus, heat such as retort food. It is suitably used for the production of food packaging films for packaging contents requiring sterilization.

Next, each component which comprises the said propylene polymer composition is demonstrated in detail.

<Propylene polymer component>

The propylene polymer (A) constituting the main component of the propylene polymer composition is a propylene homopolymer or a copolymer made from propylene and up to 10% by weight, preferably up to 5% by weight of an α-olefin. 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- C2-C10 alpha olefins other than propylene, such as an octene, are mentioned. Among the homopolymers and copolymers prepared from the comonomers, propylene homopolymers are preferably used because they provide a film having excellent heat resistance.

<Propylene-α-olefin random copolymer component>

The propylene-α-olefin random copolymer (B) is a copolymer prepared from propylene and an α-olefin having 2 to 10 carbon atoms other than the above propylene, and exhibits properties similar to those of the original elastomer. Particularly preferred as the α-olefin is ethylene.

The content of the propylene unit of the propylene-α-olefin random copolymer (B) is preferably 70 to 85% by weight, more preferably 75 to 83% by weight. The α-olefin content of the copolymer is 15 to 30% by weight, preferably 17 to 25% by weight. When the propylene content is in the above range, a film having excellent low temperature impact resistance and low temperature heat sealing property and capable of maintaining a high sealing strength even after exposure to heat treatment can be formed from the composition containing the component. This propylene unit content can be obtained by IR spectroscopy.

The proportion of the propylene-α-olefin random copolymer component (B) in the propylene polymer composition can be calculated based on the following method. That is, the sample amount (grams) of the composition (a) was completely dissolved in p-xylene, and the solution was allowed to stand at 23 ° C. for 24 hours, after which the precipitate (b) (grams) was separated by centrifugation, The p-xylene soluble content is used as a propylene-alpha-olefin random copolymer (B), and it calculates based on following Formula.

Copolymer (B) content = [(a-b) / a] × 100 (% by weight)

The intrinsic viscosity [η] of the propylene-α-olefin random copolymer (B) is 2 to 3.5 (dl / g), preferably 2.5 to 3.3 (dl / g). If intrinsic viscosity [(eta)] is the said range, the film with favorable blocking resistance can be manufactured, suppressing generation | occurrence | production of a fisheye at the time of film shaping | molding.

Intrinsic viscosity [η] is a measure of the viscosity of the precipitate recovered in 135 ° C. decalin solvent based on the viscosity obtained by precipitating the soluble fraction from the p-xylene soluble fraction separated by the separation process by adding excess acetone. By calculating.

<Ethylene-α-olefin Random Copolymer Component>

The ethylene-α-olefin random copolymer (C) is a random copolymer prepared from ethylene and an α-olefin having 4 or more carbon atoms, preferably 4 to 10 carbon atoms. Specific examples of the α-olefin include 1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-tetradecene and 1-octadecene Can be mentioned. Of the aforementioned comonomers, 1-butene, 1-hexene, and 1-octene are particularly preferred. You may use these alpha-olefins individually or in combination of 2 or more types. Moreover, these may be in the state of the mixture with another ethylene-alpha-olefin random copolymer component.

Preferable examples of the ethylene-α-olefin random copolymer (C) include ethylene-1-butene random copolymers, ethylene-1-hexene random copolymers, and ethylene-1-octene random copolymers.

The density of this copolymer (C) is 0.865-0.910 (g / cm <^3> ), Preferably it is 0.875-0.900 (g / cm <^3> ).

The ethylene-α-olefin random copolymer (C) preferably has an ethylene unit content of 70 to 95 mol%, more preferably 80 to 93 mol%, and preferably an amount of 5 to 30 mol. %, More preferably, it is 7-20 mol%.

It is preferable that this ethylene-alpha-olefin random copolymer (C) has one or more of the following characteristics, and it is low temperature impact resistance and drop impact strength from the propylene polymer composition containing the said ethylene-alpha-olefin random copolymer component (C). An excellent film is obtained.

(1) According to ASTM D-1238, the melt flow rate (MFR) measured at 190 ° C under 2.16 kg load is preferably 0.01 to 5 (g / 10 min), more preferably 0.1 to 3 (g / 10) Min).

(2) The crystallinity determined by the X-ray diffraction method is preferably 5 to 40%, more preferably 7 to 30%.

(3) The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) determined by gel permeation chromatography (GPC) is preferably 3 or less, and more preferably 2.5 or less.

(4) Melting | fusing point calculated | required with reference to the float endothermic curve on the conditions of the temperature increase rate of 10 degree-C / min by the differential scanning type calorimeter is 40-40 degreeC, More preferably, it is 60-90 degreeC.

<Manufacturing process of the composition>

The propylene polymer composition can be prepared according to the following process, for example.

(1) The propylene polymer component (A), the propylene-α-olefin random copolymer component (B), and the ethylene-α-olefin random copolymer component (C) prepared from ethylene and an α-olefin having 4 or more carbon atoms, respectively, in advance After manufacture, these components are blended in a homogeneous batch at a predetermined ratio.

(2) A mixture of the propylene polymer component (A) and the propylene-α-olefin random copolymer component (B) was prepared in advance, and the ethylene-α-olefin random copolymer component prepared from ethylene and α-olefin in this mixture ( C) is mixed at a predetermined ratio.

The mixture of the propylene polymer component (A) and the propylene-α-olefin random copolymer component (B) may be prepared after each of the production of (A) and (B) in a different polymerization step. Each of these polymerization steps can be performed in parallel or in series. In the former case, any one step may be preceded by another step, but from the viewpoint of obtaining a polymer having a high degree of crystallinity, it is preferable to first perform a polymerization step for the propylene polymer component (A). Although either a batch type or a continuous type can be selected as a 1st polymerization process, continuous type is preferable. The continuous type may be either a one-stage polymerization step using one polymerization tank or a step using a multistage polymerization system in which a plurality of polymerization tanks are integrated into a multistage polymerization system. A mixture of the propylene polymer component (A) and the propylene-α-olefin random copolymer component (B) produced by each of the above polymerization steps is usually referred to as a propylene-α-olefin block copolymer.

Mixtures of the propylene polymer component (A) and the propylene-α-olefin random copolymer component (B) can be prepared using stereoregular olefin polymerization catalysts such as Ziegler-Natta catalysts and metallocene catalysts. Examples of the polymerization catalyst include a solid titanium catalyst component having an active magnesium compound, a titanium compound, a halogen compound and an internal electron donor as essential components on an organic or inorganic carrier; To it is added an organometallic compound derived from a metal of Groups I-III of the periodic table; Again, a catalyst system prepared by adding an external electron donor can be mentioned here. This catalyst system may be used for the preliminary polymerization of the α-olefin prior to the polymerization of propylene or the like. As the solid titanium catalyst component, a reactant prepared by a reaction between an alcohol-containing magnesium compound and titanium tetrachloride in a hydrocarbon solvent is preferable. As the external electron donor, a diether compound and / or a silane compound is preferable. The said polymerization catalyst can also be used for manufacture of an ethylene-alpha-olefin random copolymer component (C).

As said polymerization process, any of suspension polymerization in a hydrocarbon solvent, suspension polymerization in a propylene solvent, gas phase polymerization, and the combination of the said polymerization process can be used. For example, in the case of producing the two components, the first step may be performed by suspension polymerization in a propylene solvent, and the second step may be performed by gas phase polymerization.

The mixture of the propylene polymer component (A) and the propylene-α-olefin random copolymer component (B) may be prepared by melt kneading two previously prepared components without going through the above polymerization route.

For use in applications where a high impact film is desired, the propylene polymer composition may further contain an elastomer component. As said elastomer, you may use a normal thermoplastic elastomer. Examples of the elastomer component that can be blended include ethylene-propylene copolymer rubber, ethylene-1-butene copolymer rubber, ethylene-1-hexene copolymer rubber, ethylene-1-octene copolymer rubber, ethylene-propylene-diene copolymer rubber And ethylene-1-butene-diene copolymer rubbers, halogenated styrene-butadiene block copolymers and halogenated styrene-isoprene block copolymers.

Prior to the film forming step, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a hydrochloric acid absorbent, an antiblocking agent, a slip agent, a pigment, a dye, or the like may be added to the propylene polymer composition.

Examples of the antioxidant include phenolic antioxidants, organophosphorus antioxidants, thioether antioxidants, hindered amine antioxidants and the like. Examples of the antiblocking agent include aluminum oxide, silica fine particles, polymethyl methacrylate powder, silicone resin and the like.

Examples of slip agents include bisamides such as ethylene bisstearoamide, oleic acid amides, higher fatty acid amides such as erucic acid amide, and the like. Examples of the lubricant include calcium stearate, zinc stearate, metal salts of higher fatty acids such as metal salts of montanic acid, polyolefin waxes such as polyethylene wax and polypropylene wax. Examples of nucleating agents include dibenzylidene sorbitol, rosin-based nucleating agents such as some metal salts of rosin acid, aluminum-based nucleating agents, talc, and the like.

film

The heat sealable film of the present invention is a film made from the propylene polymer composition. There is no restriction | limiting in particular in the method of manufacturing the said film, You may employ | adopt a conventionally well-known method. For example, the pelletized or powdered propylene polymer composition is melted using a single or twin screw compressor, and the molten resin is passed through a flat die (T-die) or a circular die mounted at the tip of the extruder to form a film. It can manufacture. The molten resin temperature in an extruder is 200-300 degreeC normally, Preferably it is 200-280 degreeC.

When the molten resin is extruded through a flat die (T-die), after the extruded film is chilled and solidified while contacting with a roll kept at a specific temperature in water or another cooling medium, it is wound up using a winder. When the molten resin is extruded through a circular die, the outside and / or the inside of the circular film is chilled by a cooling medium such as cold air or water. After that, the film is wound up or woven into a film having a desired shape. The film obtained in this way is 20-1000 micrometers normally, Preferably it is 30-200 micrometers, More preferably, it is 40-100 micrometers.

It is known that this film may be used in a normal packaging application in the form of an original single layer film, and is particularly suitable for use as a packaging film of contents requiring heat sterilization treatment such as retort food. After laminating the film on one layer that can function as a substrate, it has been suggested that it can be used for the same purpose in the form of a laminate.

Laminated film

The laminated | multilayer film of this invention is a laminated body which laminated | stacked the base material on one side or the surface of the film of this invention. The type of substrate is not particularly limited as long as it can be used as a packaging material. This may be in the form of a sheet, film, tray, container, or the like.

Examples of substrate layers that can be used include thermoplastic films and sheets, similarly formed from trays and hollow containers obtained by thermoforming the sheet, aluminum foil or paper. Examples of this film include polyester resin films made from poly (ethylene terephthalate), poly (ethylene naphthalate), etc., polycarbonate films, polyamide films made from nylon-6, nylon-6,6, and the like, And polyolefin films prepared from ethylene-vinyl alcohol copolymer films, polyvinyl alcohol films, polyvinyl chloride films, polyvinylidene chloride films, and polypropylene.

When a base material layer is a film form, this film may be an unstretched film, a uniaxial stretched film, or a biaxially stretched film. The thermoplastic resin film may be a metallized or deposited film obtained by depositing a metal such as aluminum or zinc, an oxide such as silica, aluminum oxide or an inorganic compound. In addition, the substrate may be a composite or a laminate in which the films are bonded together.

As a method of forming a laminated film by forming the heat-sealing film layer of the present invention on one side or the surface of a base layer, a conventionally known lamination method can be employed as it is, and an adhesive layer is provided at the interface between the two layers. can do. For example, the substrate may be prepared by coating a urethane or isocyanate based primer or anchor coating and dry laminating it with a heat sealable film, or by extrusion extrusion or extrusion coating by direct extrusion of the propylene polymer composition onto the substrate. . When the base material layer is formed from a thermoplastic resin, the laminated film can be directly formed by the coextrusion method. When the laminated film is to be used as a packaging application of contents requiring heat sterilization treatment such as retort food, the substrate is usually laminated on one side of the heat sealable film. When using it as another kind of packaging material, a base material layer may be laminated | stacked on one side or both sides of a heat-sealing film.

In the laminated film thus obtained, the heat sealable film layer has a high heat sealing strength or a peeling strength of the heat sealing portion when used as a packaging material, and maintains high heat sealing strength even after retort treatment is performed under high temperature and high pressure. . For example, this maintains a peel strength of 35 (N / 15 mm) or more.

The laminated | multilayer film of this invention has the heat sealing film layer excellent in heat resistance, low temperature impact resistance, heat sealing strength, and rigidity on the surface. Moreover, although it depends on the kind of base material layer to be used, it further increases gas barrier property and mechanical strength. For this reason, it can be used in a wide range of fields including retort food packaging. The laminated film can be used as a packaging material after being converted into a layered film type or a tray type and a container type.

Package

The packaging product of the present invention including the contents requiring heat sterilization treatment such as retort food, medicine, medical container, and pet food is a laminated film laminated on a substrate using at least one heat-sealing film having the above characteristics as a packaging material. Since the above contents are packaged using the above, the heat sealable film layer can be disposed on the inner surface side to package retort food or the like as the contents, and heat seal the heat sealable film layer later.

Although the one-layer film itself can be used as a packaging material, it is preferable to use a laminated film because it can utilize various characteristics inherent in the substrate layer. When the said laminated | multilayer film is used for manufacture of the package containing a retort food etc., the example of the preferable combination of a base material layer and a heat-sealing film layer is mentioned.

Polyester Layer / Heat Sealable Film

Polyamide Layer / Heat Sealable Film

Polyester Layer / Aluminum Foil / Heat Sealable Film

Polyester layer / polyamide layer / aluminium foil / heat sealable film

Polyamide layer / polyvinylidene chloride layer / polyester layer / heat sealable film

Since the heat-sealing film layer is heat-sealed after arranging at the position of the innermost layer in the package containing the contents requiring heat sterilization treatment, the heat-sealing portion has high heat-sealing strength and undergoes heat sterilization treatment such as retort treatment. High heat-seal strength is maintained even after performing.

Therefore, the above-mentioned packaged product containing the retort food is convenient to handle since food leakage does not substantially occur in transportation, storage, home, etc., and it is hardly damaged even after long-term storage at room temperature or in a refrigerated or frozen state. In the present invention, the package includes not only general foods but also items (eg, retort foods, medicines, medical supplies, pet foods) that require heat sterilization such as retort sterilization.

Example

The present invention is explained in more detail with reference to the following examples. However, these examples illustrate the present invention and do not limit the scope of the present invention.

The test results for the properties of the (co) polymer and the polymer composition and the test results for evaluating the film and the laminated film were measured according to the following test method.

(1) Test method for measuring physical properties of polymer

Ethylene content;

The ethylene content was determined based on the absorbance for the wavelength 720 cm ^-1 in the IR absorption spectrometer.

Intrinsic viscosity [η];

Intrinsic viscosity [η] was calculated based on the value obtained by dissolving the polymer sample in 135 ° C. decalin and performing a test using a Ubelrod viscometer.

Melt Flow Rate (MFR):

Meltflowrate was obtained under a load of 2.16 kg at 190 ° C. or 230 ° C., according to ASTM D-1238.

p-xylene solubles;

The p-xylene solubles were calculated based on the calculated value by subtracting the amount of precipitate precipitated by centrifugation from the p-xylene solution in which the polymer composition was completely dissolved from the amount of sample. Prior to the centrifugation, the p-xylene solution was left at 23 ° C. for 24 hours.

Hexane solubles;

2 g of polymer composition samples were put in 1 liter of hexane, and the solution was stirred at 50 ° C. for 2 hours, and then the solid content was separated by filtration. Thereafter, hexane in the liquid phase was completely evaporated to collect hexane soluble fraction as a residual. This hexane solubles were weighed and the value recorded.

(2) Test method to measure film characteristic

Low temperature impact strength

Low temperature impact strength is a film impact tester manufactured by Yasuda Precision Machinery Co., Ltd., according to ASTM D-3420, except that the test temperature is -10 ° C, the front diameter of the hammer is 1 inch, and the energy of the hammer is 3 Joule. Measured using. The test piece film was 70 micrometers in thickness.

Blocking resistance;

Blocking resistance was obtained by measuring the degree of blocking after leaving the film having a thickness of 70㎛ for 7 days under a load of 40kg at 60 ℃ according to ASTM D-1893.

Whitening resistance due to bending

The opposing edges of the film samples cut to A4 size (9 "x 12" or 210 x 297 mm) were held with both hands and bent 30 times, and then whitening in the bends was examined.

Haze;

According to ASTM D-1003, haze was measured.

(3) Test method for measuring physical properties of laminated film

Heat seal strength;

One of the two sheets of laminated film was placed on the other, and an envelope-shaped pouch (three sides were heat-sealed) of a size suitable for accommodating the contents of 105 mm (length direction) x 155 mm (horizontal direction) was produced. Hot-sealing was performed for 1 second at the pressure of 0.2 Mpa at 200 degreeC and 210 degreeC using the width 5 mm sealing bar.

Cut 15 mm wide specimens from the vertical heat seals (hot seals along the side edges) and horizontal heat seals (hot seals along the bottom edges) of the fabricated envelope-shaped pouches, and each specimen was subjected to crosshead speed. Peeling was performed with a tester at 500 mm / min. Prior to the retort sterilization treatment, the peel strength was measured to be a heat seal strength (N / 15 mm).

The heat sealing strength after retort sterilization treatment (“post heat treatment heat sealing strength”) was measured by the following method. That is, 200 ml of a liquid prepared by mixing together 9 parts of water and 1 part of salad oil was placed in an envelope-type pouch (three sides were heat sealed), and then the opening was heat sealed under the above conditions. The filled pouches were heated at 121 ° C. for 30 minutes using a heat shredder type high pressure autoclave. Thereafter, the pouch was cooled, the contents were discarded, and the slippery substance remaining in the pouch was washed with a detergent, and finally the pouch was air dried. Then, the test piece was cut out of the pouch by the method similar to the method performed with respect to the test piece before above-mentioned retort process, and the heat-sealing strength (N / 15mm) was calculated | required by the same method.

Drop impact strength;

One of the two sheets of laminated film was placed on the other, and an envelope-shaped pouch (three sides were heat-sealed) of a size suitable for accommodating the contents of 105 mm (length direction) x 155 mm (horizontal direction) was produced. Hot sealing was performed for 2 second at the pressure of 0.2 Mpa at 200 degreeC using the width 10 mm sealing bar.

200 ml of a liquid prepared by mixing 9 parts of water and 1 part of salad oil together was placed inside the pouch, and then the opening was heat sealed. Ten pouches were prepared, and these pouches were subjected to the same treatment as the retort sterilization treatment described above. This pouch was then stored for 7 days in a refrigerator kept at 5 ° C.

Drop impact testing was performed by free dropping all sample pouches weighing 1 kg of the same size one by one onto a stainless steel tray placed on a concrete floor in a refrigerator maintained at 5 ° C. at a height of 80 cm (condition a) and 60 cm (condition b). . The drop test was repeated for all ten pouches until rupture occurred in all pouches. Each of these pouches counted the number of drops until the rupture occurred, and the average number of drops was determined. This average fall number was made into the drop impact strength.

Surface smoothness;

One of the two sheets of laminated film was placed on the other, and an envelope-shaped pouch (three sides were heat-sealed) of a size suitable for accommodating the contents of 105 mm (length direction) x 155 mm (horizontal direction) was produced. Hot sealing was performed for 2 second at the pressure of 0.2 Mpa at 200 degreeC using the width 5 mm sealing bar.

Mabotofu-no-Moto (karakuchi) (Chinese seasonal tofu) (very spicy pepper), made by Marumiya Co., was charged into the pouch. Five identical filled pouches were prepared and all pouches were subjected to retort sterilization using a high pressure autoclave. The surface smoothness of the outer surface (top and bottom outer surfaces) of the pouch was then visually observed. Surface smoothness was evaluated based on the following criteria.

Excellent: very little unevenness

Good: some uneven areas

Poor: Shallow concave over a large area

Poor: deep concave over a narrow area.

Example 1

As a polymer composition composed of a propylene polymer and a propylene-α-olefin random copolymer, a propylene-ethylene block copolymer having the following properties was prepared. In addition, an ethylene-1-butene random copolymer having the following properties was prepared as the ethylene-α-olefin random copolymer.

Propylene-ethylene block copolymer

Propylene Homopolymer Component: 85.9 wt%

Propylene-ethylene random copolymer component: 14.1 wt%

Ethylene Content: 19.5 wt%

Propylene content; 80.5% by weight

Intrinsic viscosity η; 3.1 (dl / g)

Melt flow rate of the block copolymer (230 ° C.); 3.2 (g / 10 minutes)

Ethylene-1-butene Random Copolymer

Density: 0.885 g / cm ³ , ethylene content; 89 mol%

Crystallinity: 13%, melting point; 68 ℃

Mw / Mn: 2.0, Melt flow rate (190 ° C.): 0.5 (g / 10 min)

The properties of each (co) polymer are shown in Table 1.

After the following additives were added to the (co) polymer, the propylene polymer composition was pelletized by extrusion with a single screw extruder ("pellet composition").

(1) Propylene-ethylene block copolymer: 85 wt%

(2) ethylene-1-butene random copolymer: 15% by weight

(3) Phenol-based heat stabilizer (manufactured by Chivas pessultic chemical company, brand name: Irganox 1010): 0.1% by weight

(4) Organophosphorus thermal stabilizer (available from Ciba Special Sulchemical Co., Ltd., brand name: Irgafox 168): 0.1 wt%

(5) 0.1% by weight of calcium stearate

This pelletized composition has the following properties.

p-xylene solubles (23 ° C): 25.7 wt%

Hexane solubles (50 ° C): 1.7 wt%

Melt flow rate (230 ° C.); 2.8 (g / 10 minutes)

The properties of the composition thus obtained are collected and shown in Table 1.

This pelletized composition was fed to an extruder and melted at 230 degreeC, This molten resin was extruded by the flat die (T-die), and it was set as the film form. The extrudate was then contacted with a metal roll held at 30 ° C. to cool and solidify and wound onto a roll. Thus, a film having a thickness of 70 µm was obtained. The properties of the thus obtained film were measured, and the results are shown in Table 1.

Comparative Example 1

A film having a thickness of 70 μm was formed in the same manner as in Example 1 except that only the propylene-ethylene block copolymer shown in Table 1 was used as a raw material. The characteristic of this obtained film is measured, and the result is shown in Table 1.

Comparative Example 2

Propylene-ethylene block copolymers and ethylene-propylene random copolymers having the following properties were prepared, respectively.

Propylene-ethylene block copolymer

Propylene Homopolymer Component: 84.0 wt%

Propylene-ethylene random copolymer component: 16.0 weight percent

Ethylene Content: 26.0 wt%

Propylene content; 74.0 wt%

Intrinsic viscosity η; 1.9 (dl / g)

Melt flowrates of block copolymers; 1.8 (g / 10 minutes)

Ethylene-propylene Random Copolymer

Density: 0.870 g / cm ³ , ethylene content; 82.6 mol%

Mw / Mn: 2.0, melt flow rate (190 ° C.): 3.6 (g / 10 min)

The properties of each copolymer are collectively shown in Table 1.

A propylene polymer composition comprising 95% by weight of the propylene-ethylene block copolymer and 5% by weight of the ethylene-propylene random copolymer was used in the same manner as in Example 1 except that the propylene polymer composition was 70 µm thick. A film was formed. The characteristic of the film thus obtained is measured, and the results are shown in Table 1.

Comparative Example 3

Propylene-ethylene block copolymers and ethylene-1-butene random copolymers having the following properties were prepared, respectively.

Propylene-ethylene block copolymer

Propylene Homopolymer Component: 85.9 wt%

Propylene-ethylene random copolymer component: 14.1 wt%

Ethylene Content: 19.5 wt%

Propylene content; 80.5% by weight

Intrinsic viscosity η; 3.8 (dl / g)

Melt flow rate of the block copolymer (230 ° C.); 3.2 (g / 10 minutes)

Ethylene-1-butene Random Copolymer

Density: 0.885 g / cm ³ , ethylene content; 89 mol%

Crystallinity: 13%, melting point; 68 ℃

Mw / Mn: 2.0, Melt flow rate (190 ° C.): 0.5 (g / 10 min)

The properties of each copolymer are collectively shown in Table 1.

A propylene polymer composition comprising 95% by weight of the propylene-ethylene block copolymer and 5% by weight of ethylene-1-butene random copolymer was used in the same manner as in Example 1 except that the propylene polymer composition was used in a thickness of 70. A film of μm was formed. The film thus obtained did not measure the properties of this film because a large amount of fisheye was observed, and was determined to be unsuitable for use as a packaging film.

TABLE 1

Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Component of Polymer Composition Propylene-ethylene block copolymer MFR (230 ° C) g / 10 min Propylene polymer wt% Propylene-ethylene wt% Random copolymer Specific viscosity [η] dl / g Propylene content wt% 3.285.914.13.180.5 0.887.013.02.765.0 1.884.016.01.974.0 3.285.914.13.880.5 Ethylene-α-olefin Random Copolymers Type of α-olefin MFR (190 ° C) g / 10 Density g / cm 3 Ethylene Content Mole% Crystallization% Melting Point ° C Mw / Mn Composition Ratio in Parts 1-butene0.50.8858913682.015 -------0 Propylene 3.60.87082.6 Don't Know 2.05 1-butene0.50.8858913682.015 Properties of Polymer Composition MFR (230 ° C) g / 10min Ethylene Content wt% p-Xylene Solubility (23 ° C) wt% Hexane Solubility (50 ° C) wt% 2.815.325.71.7 0.84.613.00.9 2.58.020.41.1 2.815.325.31.6 Characteristics of the film Blocking resistance N / m Low temperature impact strength (-10 ℃) kJ / m Haze% Whitening resistance by bending 0.301441 No change White flower 8.401620 No change

Example 2

A laminate was prepared by dry laminating a 12 탆 thick biaxially stretched poly (ethylene terephthalate) (PET) film on a 7 탆 thick aluminum foil using a urethane adhesive. Thereafter, the film prepared in Example 1 was dry laminated using a urethane adhesive on the surface of the aluminum foil. The characteristic of the obtained laminated body is measured, and the result is shown in Table 2.

Comparative Examples 4 and 5

Among the laminates of biaxially stretched poly (ethylene terephthalate) (PET) films and aluminum foils in Example 2, except that the films prepared in Comparative Examples 1 and 2 were dry laminated on the aluminum foil surface, respectively. Prepared a laminate in the same manner as in Example 2.

The characteristic of the film thus obtained is evaluated, and the result is shown in Table 2.

TABLE 2

Example 2 Comparative Example 4 Comparative Example 5 Heat seal strength of laminates in the longitudinal and horizontal directions (length / horizontal) (N / 15mm) Heat seal temperature 200 ℃ 210 ℃ 41.8 / 54.941.9 / 61.3 44.6 / 47.947.2 / 48.0 32.1 / 41.434.8 / 43.5 Heat seal strength (N / 15mm) of laminate after heat treatment in the longitudinal and horizontal direction (length / horizontal) (Heating conditions: 121 ℃ / 30 minutes) Heat seal temperature 200 ℃ 210 ℃ 36.6 / 57.841.2 / 59.8 37.2 / 40.139.1 / 41.7 28.4 / 36.530.4 / 38.1 Drop impact strength (falls to burst) Condition a 5.7 1.9 2.5 Condition b 6.4 3.3 4.0 Surface smoothness Upper side Great Good Great Bottom Poor Bad Poor

The heat sealable film of the present invention has a high heat seal strength, a slight decrease in the heat seal strength even after heat treatment, excellent blocking resistance and excellent whitening resistance due to bending, and high rigidity and low temperature impact resistance. . Therefore, this film can be suitably used as a packaging film for contents requiring heat sterilization treatment such as a retort food as well as a packaging film for general foods.

Since the heat-sealing film which has the above-mentioned characteristic is formed on the surface as a heat-sealing layer, the heat sealing laminated film of this invention can be used as a packaging material for retort foodstuffs and various packaging articles.

The packaging of the present invention, including the contents that require heat sterilization treatment such as retort food, maintains high heat sealing strength even after retort sterilization as well as the above characteristics, and prevents convex convexity on the surface of the package. Or relaxes and has a good appearance. Thus, the package can substantially retain its contents without being damaged during transportation or when stored at room temperature, refrigerated or frozen conditions.

Claims (8)

From a propylene polymer composition comprising a propylene polymer component (A), a propylene-α-olefin random copolymer component (B), and an ethylene-α-olefin random copolymer component (C) prepared from ethylene and an α-olefin having 4 or more carbon atoms. As a heat-sealed film prepared, the composition is (1) the weight ratio of the propylene polymer component (A) and the propylene-α-olefin random copolymer component (B) is 80/20 to 95/5, (2) the propylene-α-olefin random copolymer component (B) has an intrinsic viscosity [η] of 2 to 3.5 (dl / g) and contains 70 to 85% by weight of propylene units; (3) The ethylene-α-olefin random copolymer component (C) has a density of 0.865 to 0.910 (g / cm ³ ) and is heat sealable film, characterized in that it is composed of 10 to 30% by weight based on the total amount of the composition. . The method of claim 1, The propylene polymer composition contains 15 to 30% by weight of 23 ° C p-xylene soluble component, 2.5% by weight or less of 50 ° C hexane soluble component. The method according to claim 1 or 2, The propylene polymer composition has a melt flow rate of 2 to 10 (g / 10 minutes) at 230 ° C., and contains 10 to 20% by weight of ethylene units. The method according to any one of claims 1 to 3, The ethylene-α-olefin random copolymer (C) is a heat-sealing film, characterized in that the melt flow rate at 190 ℃ 0.01 to 5 (g / 10 minutes). The method according to any one of claims 1 to 4, A heat sealable film, characterized in that it is designed for services suitable for the packaging of contents requiring heat sterilization. The heat-sealing laminated film in which the base material layer was laminated | stacked on one side of the heat-sealing film of any one of Claims 1-4. The method of claim 6, A heat-sealing laminated film, characterized in that it is designed for services suitable for the packaging of contents requiring heat sterilization. A package comprising a content that requires heat sterilization treatment, the content of which is packaged by heat sealing with a heat sealable laminated film layer according to claim 6.