JP2018090723A - Polypropylene-based sealant film and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stably producing a polypropylene-based sealant film by an upward air-cooled inflation method.SOLUTION: There is provided a method for producing a polypropylene-based sealant film, which contains a resin composition containing 1-50 pts.mass of an ethylene-α-copolymer with respect to 100 pts.mass of a polypropylene resin composition containing 70-95 mass% of a propylene homopolymer and 5-30 mass% of a propylene copolymer elastomer as a main component, with an upward air-cooled inflation film-formation machine provided with a thermal insulation cylinder covering the outside of resin bubbles discharged from a dice from its base up to the top of a frost line.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sealant film made of polypropylene resin as a main material and formed by an upward air-cooling inflation method and a method for manufacturing the same. The film has a heat resistance of up to 135 ° C. and is improved in tensile strength and elongation in the longitudinal and transverse directions by about 20 to 40% compared to a conventional cast film (CPP) of the same thickness. Excellent tearability in the film direction (MD direction).

  Polypropylene is a low-cost resin that has excellent transparency, heat resistance, flexibility, weather resistance, recyclability, and the like, as well as polyethylene. Films mainly composed of polypropylene resin are widely used as sealant films that are responsible for the sealing and heat-sealing properties of packaging materials. A general polypropylene sealant film is called CPP, and most of the films are formed using a casting method.

  An air-cooled inflation method is the most economical film production method for commercial production of resin films, and polyethylene resin films are produced not only by the casting method but also by this method.

  As a method for producing a polypropylene sealant film, there are methods disclosed in Patent Document 1 and Patent Document 2.

  Patent Document 1 discloses a sealant film by an air-cooled inflation method using a polypropylene resin containing an elastomer component composed of a propylene elastomer and / or an ethylene elastomer. This invention improves the point that polypropylene resin is inferior in low-temperature heat-sealability by adding an elastomer component, and further solves the yuzu skin problem that occurs when an oil-containing food is packaged and subjected to a high retort treatment.

  Patent Document 2 also discloses an invention in which a polypropylene resin composition containing a propylene-ethylene copolymer or a polypropylene-α-olefin copolymer as an elastomer component in a polypropylene component is formed by an air-cooled inflation method. The present invention solves the problem that polypropylene is inferior in impact resistance at low temperatures.

JP 2002-331578 A Japanese Patent Laid-Open No. 2004-27218

  However, polypropylene resin has a lower melt tension and higher crystallization speed than polyethylene resin, so in the case of producing a sealant film, the shape of the blown bubble may be unstable in upward air-cooled inflation. It was difficult to increase the blowing ratio (blow ratio), and it was difficult to obtain a uniform thin film or a wide film. As a result, inflation film formation was usually performed downward.

  Further, the upward air-cooled inflation method has a high tearability because the molten bubbles are solidified while being aligned vertically and horizontally in the film forming (vertical direction) and blowing (horizontal direction). A high tear strength has a high strength as a packaging material, but becomes a packaging material that is difficult to open when opened by a consumer.

  The methods of Patent Documents 1 and 2 improve low-temperature heat sealability and impact resistance at low temperatures, but do not basically solve the instability and tearability of film formation in the upward air-cooled inflation method. Absent.

  It is an object of the present invention to have tensile strength and elongation in the longitudinal and transverse directions as compared with a conventional cast film (CPP) having the same thickness and heat resistance up to 135 ° C. by an upward air-cooled inflation method. Is to provide a method capable of stably producing a polypropylene-based sealant film that is improved by about 20 to 40% and is excellent in tearability in a direction parallel to film formation.

  In order to solve the above-mentioned problems, the present inventors proceeded with intensive studies, and by adding a propylene copolymer elastomer to a propylene homopolymer that is polypropylene to increase the melt tension, on the other hand, the outside of the resin bubble discharged from the die The same diameter cylindrical shape is formed by providing a heat insulating cylinder covering from the lip portion to the frost line (in the inflation film formation, the material extruded from the die is cooled and the boundary line where the transparency changes suddenly when solidified from the molten state). While maintaining, the crystallization progresses slowly while mainly applying the orientation in the longitudinal direction, and further, by blending the ethylene-α-olefin copolymer, the crystallization of polypropylene is suppressed. Polypropylene sealant film can be manufactured stably with upward air-cooled inflation method The obtained film has heat resistance up to 135 ° C., and the tensile strength and elongation in the longitudinal and transverse directions are improved by about 20 to 40% as compared with the conventional cast film-forming film (CPP) of the same thickness. It was found that the film has excellent tearability in the film direction.

  The air-cooled upward inflation method enables film formation at a lower temperature than the casting method, and can suppress thermal degradation of the resin (especially in the case of polypropylene resin, molecular cutting due to thermal history). Can exhibit tensile strength and elongation equal to or better than cast products.

  Accordingly, the present invention relates to an ethylene-α-olefin copolymer of 1 to 50 parts by mass with respect to 100 parts by mass of a propylene-based resin composition composed of 70 to 95% by mass of a propylene homopolymer and 5 to 30% by mass of a propylene copolymer elastomer. With respect to 100 parts by mass of a propylene-based resin composition comprising a polypropylene-based sealant film containing as a main component a resin composition containing 70 parts, a propylene homopolymer 70 to 95% by mass, and a propylene copolymer elastomer 5 to 30% by mass A heat insulation cylinder is provided to cover the outside of the resin bubble discharged from the die from the base to the top of the frost line with a resin composed mainly of a resin composition containing 1 to 50 parts by mass of an ethylene-α-olefin copolymer. Polypropylene-based sealant, characterized in that the film is formed with an upwardly air-cooled inflation film forming machine A method for producing a film is provided.

  According to the present invention, not only can a polypropylene-based sealant film be stably produced, but it can also be produced stably by a conventional upward air-cooled inflation method that has heretofore been hardly possible. In the conventional downward inflation method, an extruder, which is a heavy machine, has to be installed on the floor, and the burden of equipment investment such as a raw material supply line and a load-bearing rack is large. However, in the present invention, the extruder can be installed on the ground by facing upward, and an advantage is obtained that only the film forming apparatus is required on the floor. The obtained film has heat resistance capable of high-pressure steam sterilization at 135 ° C., and does not produce cocoon skin even when containing oily food. Compared to the conventional cast film (CPP) of the same thickness, the tensile strength and elongation in the vertical and horizontal directions can be improved by about 20 to 40%. Even if used, it is easy to open. Since expensive raw materials are not used, an inexpensive film can be obtained.

It is a figure which shows schematic structure of an example of the inflation film forming machine which manufactures the polypropylene-type sealant film of this invention. It is a figure which shows arrangement | positioning of the thermal insulation cylinder and a rectification | straightening member. It is a top view which shows arrangement | positioning of three kneading machines and dice | dies.

  The resin composition used for the polypropylene sealant film of the present invention comprises a polypropylene resin composition comprising a propylene homopolymer and a propylene copolymer elastomer and an ethylene-α-olefin copolymer. The polypropylene resin composition is composed of a propylene homopolymer and a propylene copolymer elastomer.

  The propylene homopolymer is polymerized with a catalyst using propylene as a monomer. It is preferable that the melt flow rate (230 ° C.) is about 0.1 to 8 g / 10 minutes, preferably about 0.5 to 2 g / 10 minutes, and the melting point is 155 to 162 ° C., preferably 157 to 161 ° C.

  The propylene copolymer elastomer serves to supplement the melt tension during melt film formation and also to supplement the cold resistance of the film. Preferred comonomers are ethylene and diene, and its binary or ternary copolymer is generally EPR. , EPM, EPDM. A copolymer having an ethylene copolymerization ratio of 47 to 67 mol% is particularly preferred. As for the physical properties, those having a specific gravity of 0.84 to 0.87, a Mooney viscosity at 100 ° C. of 40 to 100, and a glass transition temperature of −60 to −35 ° C. are desirable. The process of blending this propylene copolymer elastomer into a propylene homopolymer is cumbersome, such as the need for a rubber processing machine, so a commercial product in pellet form so that it can be blended with a general-purpose resin processing machine Is preferably used. This is sold, for example, under the trade names of “Tafmer” manufactured by Mitsui Chemicals, Inc. and “Esplen” manufactured by Sumitomo Chemical Co., Ltd.

  The blending ratio of the propylene homopolymer and the propylene copolymer elastomer is 70 to 95% by mass of the propylene homopolymer, preferably about 85 to 95% by mass, more preferably about 90 to 95% by mass, and the propylene copolymer elastomer. Is about 5 to 30% by mass, preferably about 5 to 15% by mass, more preferably about 5 to 10% by mass.

  The ethylene-α-olefin copolymer is a copolymer of ethylene and an α-olefin having about 4 to 8 carbon atoms, preferably about 4 to 6 carbon atoms, and linear low density polyethylene is particularly suitable. The physical property value is such that the MFR (190 ° C.) is about 0.1 to 20 g / 10 minutes, preferably about 0.5 to 8 g / 10 minutes. This ethylene-α-olefin copolymer exhibits an action of suppressing excessive crystallization by blending with polypropylene as a main material, and an auxiliary action of melt tension at the time of melt film formation. Will also improve.

  The blending ratio of the ethylene-α-olefin copolymer is about 1 to 50 parts by mass, preferably about 5 to 35 parts by mass, more preferably about 100 parts by mass of the polypropylene resin composition. Is preferably about 15 to 25 parts by mass.

  Other resins such as polyethylene can be added to the resin composition within a range that can ensure the characteristics of the present invention, and thus it is possible to produce an easily peelable sealant film with arbitrarily adjusted heat seal strength. is there. The blending amount of polyethylene can be, for example, about 5 to 25% by mass of low density polyethylene, and about 10 to 50% by mass in total. Further, for example, additives such as an antioxidant, an ultraviolet absorber, a filler, and a colorant can be added.

  The thickness of the polypropylene-based sealant film is about 20 to 500 μm, usually about 30 to 200 μm, particularly about 50 to 150 μm.

  In addition, this polypropylene-based sealant film has a multilayer structure having an inner layer, an intermediate layer, and an outer layer, and a film having excellent light shielding properties even if it is thinned by blending titanium dioxide in the inner and outer layers and carbon black in the intermediate layer. can do. The content of titanium dioxide is about 15 to 30% by mass, preferably 20 to 25% by mass, and the carbon black is about 5 to 15% by mass, preferably about 8 to 12% by mass. The thickness of each layer is about 7 to 200 μm, usually about 10 to 50 μm, particularly about 15 to 30 μm for both the inner layer, the outer layer, and the intermediate layer, and the thickness of each layer may be the same or different. Conventionally, as shown in Japanese Patent No. 4170415, one incorporating a black layer using a gray pigment is known, but the light shielding property is not sufficient. Moreover, although what laminated | stacked aluminum foil is also used, this has the problem that the metal detector which is a foreign material detector of a package body misdetects. The film of such an embodiment of the present invention is excellent without these problems.

The inflation film forming machine to be used is a normal inflation film forming machine provided with a heat retaining cylinder covering 30 to 800 mm, preferably 30 to 500 mm above the frost line in the steady state of the resin bubble from the air ring. By attaching this heat retaining cylinder, the molten resin is kept warm and the crystallization proceeds slowly, with the result that the frost line position rises. In the resin below the frost line, weak molecular orientation is formed mainly in the longitudinal direction, and the tearability of the film is improved. Furthermore, the thermal insulation cylinder does not affect the turbulence of the external air current, and the blown air is rectified.
For example, a transparent plastic is preferably used so that the inside of the heat insulating cylinder can be seen.

  It is preferable to provide a rectifying member along the curvature of the blowing expansion of the resin bubble inside the heat insulating cylinder. By providing this flow regulating member, the position and shape of the bottom of the resin bubble can be stabilized. The rectifying members are preferably arranged evenly so as to stably support the bottom of the resin bubble. For example, as shown in FIG. 2, a plurality of cylinders are arranged concentrically, and the upper edge of the rectifying member is The resin bubble is arranged so as to have a shape close to the curvature of expansion of the blowing of the resin bubble, that is, a shape similar to the shape similar to the bottom of the resin bubble formed in a substantially bowl shape. The interval between the surface connecting the upper edges of the rectifying member and the bottom of the resin bubble (interval in the direction perpendicular to the tangent) is preferably about 1 to 10 mm. The air outlet may be provided near the base of the resin bubble as in the case of normal airing. The material of the heat insulating cylinder is not particularly limited, but it is preferable to use, for example, a transparent plastic that can easily recognize the frost line state and has excellent heat insulation.

  Inflation film forming machines are also equipped with a multistage heat treatment roll after the resin bubbles are folded flat with a pinch roll, and the film is gradually cooled, so that the secondary crystallization of the polypropylene progresses slowly. It is possible to avoid problems such as squeezing and curling of the film wound up. The film travel path length of this multistage heat treatment roll section is about 1 to 20 m, preferably about 1.5 to 10 m, particularly preferably about 2 to 5 m, and the number of heat treatment rolls is about 3 to 30.

  The method of forming an inflation film using such an upward air-cooled inflation film forming machine is as follows. First, a propylene homopolymer pellet, a propylene copolymer elastomer pellet, and an ethylene-α-olefin copolymer pellet are predetermined. Mix in proportions. The order of blending the propylene homopolymer, the propylene copolymer elastomer, and the ethylene-α-olefin copolymer is not limited, and any of them may be added and mixed at the same time. For example, a propylene homopolymer and a propylene copolymer elastomer are kneaded in a kneading extruder equipped with a biaxial screw at 170 to 230 ° C., preferably 180 to 210 ° C., to give a pellet, which is an ethylene-α-olefin copolymer May be mixed and put into a film forming machine, or three materials may be dry blended and put into a film forming machine. Then, for example, propylene homopolymer pellets and ethylene-α-olefin copolymer pellets in which this propylene copolymer elastomer is compounded are put into a hopper of an intermediate layer extruder at a predetermined ratio, and inner and outer layer extrusion Each resin is put into a machine, kneaded with a kneader, and extruded from a die into a multilayer tube at about 160 to 210 ° C. (melting point of propylene homopolymer + 50 ° C.). Then, the tube is inflated with air pressure from the inside, and air is sent from the outside to raise the temperature. The blow ratio is not particularly limited. The temperature of this air is suitably 55 to 65 ° C. If it is higher than 65 ° C., the film is excessively heated and hinders solidification. On the other hand, if it is lower than 55 ° C., it solidifies quickly. And it folds flat with the pinch roll of the top, and while passing the heat processing roll, the temperature of a film is reduced about 20 degreeC from about 60-65 degreeC to about 40-45 degreeC.

  The obtained film has a tensile strength (JIS-Z-1702) in the longitudinal direction of about 35 to 85 MPa, and a tear strength (JIS-Z-1702) (MD) of about 0.05 to 1 N, particularly 0.05 to 0. About 2N, impact strength (JIS-K-7124) is 3 kgf or more, and heat resistance is up to about 135 ° C.

  The film of the present invention has a high tensile strength, and an equivalent strength can be obtained at a thickness of 60 to 80% compared to a conventional cast film (CPP).

  The polypropylene-based sealant film of the present invention can be used alone as a packaging film as it is, but can be used as a packaging body by performing a lamination process such as laminating on a base film. For example, it may be used by laminating with an appropriate base film for the purpose of printing display, cosmetics, light shielding properties, gas barrier properties, heat insulation properties, protection of the deposited layer, and the like. Specific examples of the base film include paper, metal foil, (deposition) (no) stretched polyester film, (deposition) (no) stretched polyamide film, (deposition) stretched polypropylene film, foam film, ethylene-vinyl alcohol copolymer Examples include a coalesced film. As a lamination method, a general dry laminate or extrusion laminate is used, and a dry laminate that is commonly used as a lamination method is particularly suitable. At that time, it is more preferable that the polypropylene-based sealant film of the present invention is subjected to a corona discharge treatment immediately after film formation on the laminate surface. The corona discharge treatment amount is preferably 37 to 47 dyne / cm in terms of the wetting index of the film surface immediately after the treatment.

  A schematic configuration of the film forming apparatus used in the examples is shown in FIG. This apparatus comprises an inflation film forming machine main body 1, three kneaders for melting and kneading the inner layer, intermediate layer, and outer layer resins connected thereto and extruding them, and a multistage heat treatment roll group 3.

  The inflation film forming machine 1 has a die for co-extruding resin extruded from three kneaders in a tube shape, and a mechanism (not shown) for pressurizing the resin extruded in a tube shape with air pressure from the inside. The apparatus includes an apparatus for air-cooling the resin extruded in a tube shape from the outside, a guide 5 for gradually folding the resin bubble 4 that is inflated in the tube shape and a pinch roll 6 for flattening it.

  The air-cooling device from the outside includes a branch pipe 13 that sends air heated by a hot air blower 9 from a blower 7 to an air outlet between an air ring 10 and a multi-cylinder 11 that is a rectifying member, and a blown air from the outside. It consists of a heat insulating cylinder 14 that eliminates the influence. The height of the heat insulating cylinder 14 from the die is 1000 mm, and the inner diameter is 1000 mm. As shown in FIG. 2, the multiple cylinders 11 are arranged concentrically as shown in FIG. 2, and the heights are 50 mm, 160 mm, 210 mm, 500 mm, 1000 mm from the inside. It has become. Air outlets 12 are arranged at equal intervals on the bottom surface between the cylinders of the multiple cylinder 11.

  The resin supplied from the kneader is extruded into a tube shape from a die, is expanded by air pressure from the inside, is gradually folded by a guide 5, and is flattened by a pinch roll 6. Then, it passes through the guide rolls 15 and 16 and is gradually cooled by a multistage heat treatment roll group (tempering roll) 3 having a runway length of 2.5 m and subjected to corona treatment by a surface treatment machine 17.

  The diameter of the resin bubble 4 in the part which became the same diameter is 600-1000 mm, and the height from the die | dye of the frost line 18 is 30-800 mm.

  The following examples were performed using the film forming apparatus.

<Resin used>
Block PP: propylene homopolymer (melt flow rate 0.5 g / 10 min,
(Melting point 162 ° C.) 93% by mass
Propylene composed of 50 mol% ethylene and 50 mol% propylene
Copolymer elastomer (ethylene-propylene rubber: EPM)
(Mooney viscosity at 100 ° C 55, glass transition temperature -45 ° C)
7% by mass
To 100 parts by mass of a propylene resin composition comprising
Ethylene-hexene copolymer (linear low density polyethylene)
Melted mixture with 20 parts by weight
MFR (230 ° C.) = 1.2 g / 10 min, melting point 163 ° C.
Random PP: 95 mol% polypropylene, 5 mol% ethylene
Random Copolymers Polymerized Using Various Metallocene Catalysts
MFR (230 ° C.) = 7.0 g / 10 min, melting point 110 ° C.

  The measuring method of each physical property value is as follows.

<Heat sealability / easy peelability>
Two films of the present invention were stacked and heat-sealed with a heat sealer at a temperature of 170 ° C., a pressure of 0.2 MPa, and a time of 1 second. A specimen piece obtained by arbitrarily cutting the heat-sealed portion with a width of 15 mm was measured for peel strength (N / 15 mm) using a tensile tester in accordance with JIS-Z0238.

<Heat resistance>
Two sheets of the film of the present invention cut to 100 × 100 mm are overlapped, the three peripheral edges are heat-sealed, 100 mL of distilled water is filled from the remaining one side, and a packaging bag sealed with a seal so as to be filled, Retort treatment was performed at 135 ° C. for 10 minutes using a retort testing machine (manufactured by Nisaka Seisakusho).
From the appearance of the specimen after retort processing (dimension expansion / contraction, transparency, wrinkles, welding, etc.), those having no problem were judged as “good”.

<Tensile strength, tear strength>
All were performed according to JIS-Z-1702 using Toyo Seiki's Strograph VES05D.

<Impact strength>
Using a film impact tester (manufactured by Tester Sangyo Co., Ltd.), the test was performed according to JIS-K-7124.

<Light shielding>
A 200 V 100 W incandescent bulb was placed in the box, a test film was attached to the opening, and observed with the naked eye from the outside.

<Wrinkles>
Visually

<Easy peel properties>
Peeling after sealing at 170 ° C. The evaluation criteria for each product level are as follows.
Product level A: No wrinkles can be easily peeled Product level B: Wrinkles are slightly not easy peeled (partly welded)
Product level C: Wrinkles occur frequently Easy peeling (completely welded)

Acrylic was used for the heat insulating cylinder. Block PP is used for each of the inner layer, intermediate layer, and outer layer, extrusion temperature 200 ° C., blow ratio 1.7, bubble diameter 1,000 mm, cooling air temperature 60 ° C., air volume 30 (HZ) m ³ / min, manufactured A single layer film having a width of 12.8 m / min and an inner layer thickness of 20 μm, an intermediate layer of 15 μm, an outer layer of 25 μm, and a total of 60 μm and a width of 800 mm was prepared. The position of the frost line was around 700 mm from the die.

  When the physical properties of the obtained film were measured, the heat seal strength was 50 N / 15 mm, the heat resistance was 135 ° C., the tensile strength (vertical) was 50 MPa, the horizontal width was 40 MPa, the tear strength in the MD direction was 0.1 N, and the impact strength was 5.8 kgf · cm. This film has heat resistance, and is improved in tensile strength and elongation in the longitudinal and transverse directions and superior in impact strength compared to conventional cast film (CPP) having the same tearability in the MD direction and the same thickness. It was suitable as a sealant for easily tearable high retort. The product level rating was A.

  On the other hand, when the same block PP was used and it was manufactured with normal cooling and normal equipment without using a heat insulating cylinder and a tempering roll, wrinkles were formed in both ears, and tarmi was produced in the central part. The product level evaluation was C. It was.

  Both the inner layer and the outer layer are a resin composition in which 70% by mass of block PP, 30% by mass of masterbatch composed of 70% by mass of titanium dioxide and 30% by mass of random PP are blended, and the intermediate layer has 80% by mass of block PP and carbon. Using a resin composition in which a master batch of 20% by mass consisting of 35% by mass of black and 65% by mass of random PP was blended, the inner layer thickness was 20 μm, the intermediate layer was 15 μm, the outer layer was 25 μm, and a total of 60 μm was 900 mm and 940 mm. A three-layer coextruded film of width was made. The position of the frost line was around 700 mm from the die.

  When the physical properties of the obtained film were measured, heat seal strength 50 N / 15 mm, heat resistance 135 ° C., tensile strength (vertical) 49 MPa, (horizontal) 27 MPa, MD direction tear strength 0.1 N, impact strength 5.8 kgf · cm. This film has heat resistance, is easily tearable in the MD direction and has a light-shielding property, and has improved tensile strength and elongation in the longitudinal and transverse directions compared to a conventional cast film (CPP) of the same thickness. It was suitable as a light-shielding sealant for high retort. The product level rating was A.

  On the other hand, when the same block PP was used and it was manufactured with normal cooling and normal equipment without using a heat insulating cylinder and a tempering roll, wrinkles were produced in both ears and tarmi was produced in the central part, and the product level evaluation was C. .

  A resin composition comprising 60% by mass of block PP, 20% by mass of HDPE, and 20% by mass of LDPE for the inner layer, and block PP is used for both the intermediate layer and the outer layer, and the inner layer thickness is 16 μm and the intermediate layer under the same conditions as in Example 1. A coextruded film of 50 μm, outer layer 54 μm and a total of 120 μm and a width of 882 mm was prepared. The position of the frost line was around 700 mm from the die.

  When the physical properties of the obtained film were measured, the heat seal strength was 18 N / 15 mm, the heat resistance was 135 ° C., the tensile strength (vertical) was 75 MPa, the (horizontal) was 60 MPa, the tear strength in the MD direction was 0.1 N, and the impact strength was 3.1 kgf · cm. This film has easy peel properties, is easy to tear in the MD direction, and has improved tensile strength and elongation in the longitudinal and transverse directions compared to conventional cast film (CPP) of the same thickness. The evaluation was A.

  On the other hand, when only the block PP was used as the inner layer, it was completely heat-sealed and there was no easy peel property.

  A coextruded film was prepared in the same manner as in Example 3 except that the inner layer thickness was 20 μm, the intermediate layer was 70 μm, the outer layer was 60 μm, and the total was 150 μm. The position of the frost line was around 700 mm from the die.

  When the physical properties of the obtained film were measured, heat seal strength 18 N / 15 mm, heat resistance 135 ° C., tensile strength (vertical) 76 MPa, (horizontal) 62 MPa, MD direction tear strength 0.1 N, impact strength 3.1 kgf · cm. This film has easy peel properties, is easy to tear in the MD direction, and has improved tensile strength and elongation in the longitudinal and transverse directions compared to conventional cast film (CPP) of the same thickness. Was A.

  On the other hand, when only the block PP was used as the inner layer, it was completely heat-sealed and there was no easy peel property.

  The inner layer has a block PP of 54.4% by mass, the HDPE of 30% by mass, and the LDPE of 15.6% by mass. The intermediate layer and the outer layer both use block PP, and under the same conditions as in Example 1, the inner layer thickness is 20 μm. A coextruded film having an intermediate layer of 20 μm and an outer layer of 10 μm and a total of 50 μm and a width of 600 mm was prepared. The position of the frost line was around 700 mm from the die.

  When the physical properties of the obtained film were measured, the heat seal strength was 18 N / 15 mm, the heat resistance was 135 ° C., the tensile strength (vertical) was 75 MPa, the (horizontal) was 60 MPa, the tear strength in the MD direction was 0.1 N, and the impact strength was 3.1 kgf · cm. This film has easy peel properties, is easy to tear in the MD direction, and has improved tensile strength and elongation in the longitudinal and transverse directions compared to conventional cast film (CPP) of the same thickness. Was A.

  On the other hand, when only the block PP was used as the inner layer, it was completely heat-sealed and there was no easy peel property.

  The polypropylene-based sealant film of the present invention can be stably formed by the upward air-cooled inflation film forming method, can be manufactured at a low cost and in a wide range of film widths, has good heat resistance and good hand cutting properties, and has the same thickness. Compared with conventional cast film (CPP), the tensile strength and elongation in the longitudinal and transverse directions are improved by about 20 to 40%, so that the same strength can be obtained at a thickness of 60 to 80%. It can be used to manufacture and use sealant films.

DESCRIPTION OF SYMBOLS 1 Inflation film forming machine body 3 Multi-stage heat treatment roll group 4 Resin bubble 5 Stabilizing plate 6 Pinch roll 7 Blower 9 Warm air machine 10 Air ring 11 Multiple cylinder 13 Branch pipe 14 Heat insulation cylinder 15 Guide roll 16 Guide roll 17 Surface treatment machine 18 Frost line

Claims (9)

  A resin in which 1 to 50 parts by mass of an ethylene-α-olefin copolymer is blended with 100 parts by mass of a propylene-based resin composition composed of 70 to 95% by mass of a propylene homopolymer and 5 to 30% by mass of a propylene copolymer elastomer. Polypropylene sealant film mainly composed of the composition   In any case, 1 to 50 parts by mass of an ethylene-α-olefin copolymer is blended with 100 parts by mass of a propylene-based resin composition composed of 70 to 95% by mass of a propylene homopolymer and 5 to 30% by mass of a propylene copolymer elastomer. An inner layer, an intermediate layer, and an outer layer containing the resin composition as a main component. The inner layer and the outer layer are 60 to 80% by mass of the resin composition, 15 to 30% by mass of titanium dioxide, and 5 to 15% by mass of a propylene random copolymer. The intermediate layer is a polypropylene sealant film comprising 70 to 90% by mass of the resin composition, 5 to 15% by mass of carbon black, and 15 to 30% by mass of a propylene random copolymer.   In any case, 1 to 50 parts by mass of an ethylene-α-olefin copolymer is blended with 100 parts by mass of a propylene-based resin composition composed of 70 to 95% by mass of a propylene homopolymer and 5 to 30% by mass of a propylene copolymer elastomer. An inner layer composed mainly of a resin composition, and an outer layer. The inner layer is a polypropylene system comprising 50 to 90% by mass of the resin composition, 5 to 25% by mass of low density polyethylene, and 5 to 25% by mass of high density polyethylene. Sealant film   A resin in which 1 to 50 parts by mass of an ethylene-α-olefin copolymer is blended with 100 parts by mass of a propylene-based resin composition composed of 70 to 95% by mass of a propylene homopolymer and 5 to 30% by mass of a propylene copolymer elastomer. The resin having the composition as a main component is formed by an upward air-cooled inflation film forming machine provided with a heat insulating cylinder that covers the outside of a resin bubble discharged from a die from the base to the top of the frost line. , Production method of polypropylene-based sealant film   The manufacturing method of the polypropylene-type sealant film of Claim 4 whose air temperature which blows off from an air ring is 55-65 degreeC.   Inflation film forming machine characterized in that a heat insulating cylinder is attached to cover from 30 to 800 mm above the frost line of a resin bubble from an air ring that blows out air that cools the outside of the resin bubble   The inflation film forming machine according to claim 6, wherein a rectifying member is provided on the inner side of the heat insulating cylinder along a curvature of blowing expansion of the resin bubble.   The inflation film forming machine according to claim 7, wherein the rectifying member is a plurality of cylindrical bodies arranged concentrically.   The inflation film forming machine according to any one of claims 6 to 8, wherein a multi-stage roll is provided to gradually cool a film formed on the downstream side of a pinch roll that folds a resin bubble flatly.

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