JP2007045049A - Polypropylene composite non-stretched film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated polypropylene composite non-stretched film having both of low temperature sealability and blocking resistance, excellent in impact resistance at a low temperature and capable of withstanding extremely severe treatment such as boiling water treatment or retorting treatment, especially air containing boiling treatment, for example, when used as a laminate with a polyamide film and a biaxially stretched polypropylene film. <P>SOLUTION: The laminated polypropylene composite non-stretched film comprises successively laminating three layers, that are, a laminate layer, a core layer and a sealing layer, wherein the respective layers comprise specified resin compositions. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laminated polypropylene-based unstretched film. Specifically, for example, when used in food packaging, it has excellent low-temperature heat sealability and low-temperature impact resistance, and, for example, with a polyamide film. When used as a laminate, the present invention relates to a laminated polypropylene-based unstretched film suitable for use in laminates that can withstand severe treatments such as boiling water treatment and retort treatment, particularly extremely severe treatments such as aerated boil treatment. .

  Polypropylene-based unstretched films are used in various packaging materials such as food packaging because they have high rigidity, good transparency and are inexpensive among sealant films. However, it has the disadvantage of being inferior in low-temperature heat sealability and impact resistance, particularly in low temperature impact resistance. On the other hand, in recent years, the speed of bag making machines has been increasing, and the market demand for low-temperature heat-sealing properties has been increasing for polypropylene-based unstretched films. In addition, the demand for improved impact resistance at low temperatures has increased due to the spread of frozen foods.

  In recent years, with the improvement of food culture, authenticity has become stronger, and noodle instant foods are also being switched from dry noodles to raw noodles. In the case of the raw noodle type, heat sterilization is performed after the raw noodles are sealed and packaged. Since this heat sterilization process is performed in an aerated state, a large stress is applied to the seal portion due to expansion of air and water vapor inside the sealed body due to heat. For this reason, only the sealing strength of the conventional packaging material is insufficient in terms of characteristics, and sealability and pressure resistance that can withstand the internal pressure generated by the air-containing boil treatment are required. In recent years, in order to meet advanced taste demands, the aerated boil conditions have become more severe, and the development of sealant films that can meet these market demands is desired.

In response to these requirements, a polypropylene-based unstretched copolymer comprising a binary copolymer of an ethylene random copolymer polypropylene polymer and a binary copolymer of ethylene and propylene or butene-1 or a terpolymer of these and a non-conjugated diene. It has been proposed to improve low-temperature heat sealability with a film (see, for example, Patent Document 1).
JP-A-5-262900

  However, the above method is not compatible with a binary copolymer of ethylene random copolymer and ethylene and butene or a ternary copolymer of these and a non-conjugated diene. Voids are formed, the sealing strength is reduced, and the internal pressure generated by the air-containing boil treatment cannot be withstood.

It has also been proposed to improve low-temperature heat sealability by using a propylene / α-olefin copolymer having a specific melting peak temperature, melting start temperature, and melting end temperature for the heat-sealing layer, that is, the sealing layer. (For example, refer to Patent Document 2).
JP 2004-268532 A

  However, the method disclosed in Patent Document 2 improves the low-temperature heat-sealability, but uses ethylene / α-olefin for the laminate layer, and the interlaminar strength decreases during boiling, which makes it easy to peel off. There was a problem that the laminate layer was whitened.

Furthermore, by laminating a base layer made of an ethylene random copolymer polypropylene polymer with a seal layer containing an ethylene random copolymer polypropylene polymer and a polyolefin random copolymer elastomer, low-temperature sealability and aerated boil puncture resistance are achieved. Improvement has been proposed (see, for example, Patent Document 3).
Japanese Patent Laid-Open No. 10-166526

  However, the above method is excellent in the resistance to aerated boil puncture when a biaxially stretched polyamide film that is easily deformed is used as the base film, but the case where a large amount of an organic slip agent is added for high speed processing or A problem in which the resistance to aerated boil puncture is impaired when a biaxially stretched polyamide film or biaxially stretched polypropylene film that is not easily deformed during boiling is laminated on the biaxially stretched polyamide film used as the material film. was there.

  The present invention has low temperature heat sealability, blocking resistance and transparency, and is excellent in impact resistance at low temperature. For example, when used as a laminate with a polyamide film or a biaxially oriented polypropylene film, boiling water An object of the present invention is to provide a laminated polypropylene-based unstretched film that can withstand severe treatment such as treatment and retort treatment, particularly extremely extreme treatment such as aerated boil treatment.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that a specific propylene / α-olefin random copolymer resin has a specific propylene / α-olefin block copolymer resin and / or a specific propylene / By laminating a laminate layer and a core layer to which a specific amount of ethylene block copolymer resin is added, and a seal layer in which a specific amount of the propylene / ethylene block copolymer resin is blended with the propylene / α-olefin random copolymer, a low temperature is obtained. The inventor has obtained the knowledge that a film having both heat sealability and blocking resistance, excellent impact resistance at low temperatures, and capable of withstanding the air-containing boil treatment has been obtained, and the present invention has been completed.

That is, the present invention provides a laminated polypropylene-based non-stretched film comprising three layers of a laminate layer, a core layer, and a seal layer, wherein the layers are laminated in the order described above, and each layer comprises at least the following resin composition. It is a stretched film.
(1) The laminate layer has a propylene / α-olefin random copolymer resin (A) having an α-olefin content of 2 to 8% by mass of 40 to 70% by mass and an α-olefin content of 3 to 10% by mass. The propylene / α-olefin block copolymer resin (B) and / or the xylene soluble part at 23 ° C. is 5 to 12% by mass, the melting point is 130 to 150 ° C., and the ethylene content is 6 to 15 Propylene / ethylene block copolymer resin (C) 30% to 60% by mass.
(2) The core layer has an α-olefin content of 2 to 8% by mass of propylene / α-olefin random copolymer resin (A) of 60 to 85% by mass and an α-olefin content of 3 to 10% by mass. The propylene / α-olefin block copolymer resin (B) and / or the xylene soluble part at 23 ° C. is 5 to 12% by mass, the melting point is 130 to 150 ° C., and the ethylene content is 6 to 15 It consists of 15-40 mass% of propylene-ethylene block copolymer resin (C) which is mass%.
(3) The seal layer has 80 to 90% by mass of propylene / α-olefin random copolymer resin (A) having an α-olefin content of 2 to 8% by mass and 5 to 5 xylene-soluble parts at 23 ° C. It consists of 10 to 20% by mass of a propylene / ethylene block copolymer resin (C) having 12% by mass, a melting point of 130 to 150 ° C., and an ethylene content of 6 to 15% by mass.
In this case, it is preferable to increase the amount of the propylene / α-olefin random copolymer resin (A) contained in the laminate layer, the core layer and the seal layer in the order of laminate layer <core layer <seal layer.
In this case, the propylene / α-olefin random copolymer resin (A) is preferably polymerized using a single site catalyst.

  The laminated polypropylene-based unstretched film of the present invention has both low-temperature heat sealability, blocking resistance and transparency, and is excellent in impact resistance at low temperatures. For example, on a biaxially stretched polyamide film used as a base film In addition, even when a layered product such as a biaxially stretched polyester film or a biaxially stretched polypropylene film is used that is not easily deformed during boiling, it is extremely difficult to perform severe treatments such as boiling water treatment and retort treatment, especially air-containing boil treatment. Can withstand extreme processing.

  The present invention is a laminated polypropylene-based unstretched film composed of three layers, a laminate layer, a core layer, and a seal layer. Thus, the present invention has a great feature in that the effect of the present invention that has been difficult to achieve with the prior art is achieved.

The three types of resins will be described below.
・ Resin (A)
The resin (A) according to the present invention is a propylene / α-olefin random copolymer resin having an α-olefin content of 2 to 8% by mass. The content of α-olefin is more preferably 3 to 7% by mass, and further preferably 4 to 6% by mass. When the α-olefin content is less than 2% by mass, the low-temperature sealing property is inferior, and when it exceeds 8% by mass, the blocking resistance deteriorates. Examples of the α-olefin include ethylene, 1-butene, 1-hexene, 4-methyl / 1-pentene, 1-octene and the like. In these, the random copolymer with ethylene and / or 1-butene is preferable. The MFR is not particularly limited as long as it can be a film, but it is usually in the range of 0.5 to 20 g / 10 minutes, preferably 2 to 10 g / 10 minutes. Further, the propylene / α-olefin copolymer (A) according to the present invention usually has a molecular weight distribution (expressed by a ratio of the weight average molecular weight Mw and the number average molecular weight Mn) in the range of 1.5 to 3. It is preferable. When it exceeds 3, low molecular weight substances increase and blocking resistance deteriorates. Therefore, it is preferable to polymerize using a single site catalyst.

・ Resin (B)
The resin (B) according to the present invention is a propylene / α-olefin block copolymer resin having an α-olefin content of preferably 2 to 10% by mass, more preferably 4 to 8% by mass. When the α-olefin content is less than 2% by mass, the impact resistance is inferior, and when it exceeds 8% by mass, the transparency and rigidity are deteriorated. Examples of the α-olefin include ethylene, 1-butene, 1-hexene, 4-methyl / 1-pentene, 1-octene and the like. In these, ethylene and / or 1-butene are preferable. The MFR is not particularly limited as long as it can be a film, but is usually in the range of 0.5 to 10 g / 10 minutes, preferably 1 to 5 g / 10 minutes. When the MFR is less than 0.5 g / 10 min, the productivity is inferior, and when it exceeds 10 g / 10 min, the impact resistance is inferior.

・ Resin (C)
The resin (C) according to the present invention is a propylene / ethylene block copolymer resin having an ethylene content in the range of 6 to 15% by mass. The resin (C) preferably has a xylene-soluble portion ratio at 20 ° C. of 5 to 12% by mass and a melting point of 130 to 150 ° C.
As for ethylene content, 7-14 mass% is more preferable, and 8-13 mass% is further more preferable. If the ethylene content is less than 6% by mass, the flexibility is poor, which is not preferable. On the other hand, if it exceeds 15% by mass, the rigidity decreases, which is not preferable.
The ratio of the xylene soluble part is more preferably 6 to 11% by mass, and further preferably 7 to 10% by mass. If the ratio of the xylene-soluble part is less than 6% by mass, the impact resistance is inferior, which is not preferable. On the contrary, when it exceeds 12 mass%, since transparency will deteriorate, it is not preferable.
As for the said melting | fusing point, 135-145 degreeC is more preferable. When the melting point is less than 130 ° C., the blocking resistance is deteriorated. Conversely, when the melting point is 150 ° C. or more, the low-temperature sealing property is deteriorated.

  In the present invention, the blending ratio of the resin (A), the resin (B) and the resin (C) in the laminate layer is such that the resin (A) is 40 to 70% by mass and the remaining 60 to 30% by mass is the resin ( B) and / or resin (C) are preferred. The ratio of the resin (A) is more preferably 45 to 65% by mass. When the proportion of the resin (A) is less than 40% by weight, the transparency is deteriorated. Conversely, if it exceeds 70% by weight, the resistance to aerated boil puncture is deteriorated.

In the present invention, the blending ratio of the resin (A), the resin (B) and the resin (C) in the core layer is such that the resin (A) is 60 to 85% by mass and the remaining 40 to 15% by mass is the resin ( B) and / or resin (C) are preferred. The ratio of the resin (A) is more preferably 55 to 80% by mass.
When the ratio of the resin (A) is less than 60% by mass, the transparency is deteriorated. On the contrary, when it exceeds 85 mass%, aeration boil puncture tolerance will deteriorate.

  In the present invention, the resin composition in the seal layer is preferably a combination of two types of resin (A) and resin (C). When the sealing layer is blended with the resin (B) blended in the laminate layer or the core layer, the low-temperature sealing property is lowered, which is not preferable. The blending ratio of the resin (A) and the resin (C) is preferably 80 to 90% by mass of the resin (A). 82-88 mass% is more preferable. When the ratio of the resin (A) is less than 80% by mass, the blocking resistance is deteriorated. On the other hand, when it exceeds 90% by mass, the low-temperature sealing property deteriorates.

  The above-mentioned resin (A), resin (B) and resin (C) according to the present invention are generally used as antioxidants, weathering stabilizers, antistatic agents, antifogging agents, as long as the object of the present invention is not impaired. Additives such as antiblocking agents, lubricants, nucleating agents, pigments or other polymers can be blended as necessary. In particular, various known anti-blocking agents such as inorganic compound particles such as silica, talc, zeolite and aluminum borate, organic compound particles such as polymethyl methacrylate, melamine formalin resin, melamine urea resin and polyester resin are contained in the seal layer. Addition of 0.01 to 1% by mass is preferable because a film having further improved anti-blocking properties can be obtained. Among these, silica and polymethyl methacrylate are particularly preferable in terms of antiblocking properties and transparency.

  In the seal layer and core layer, various known slip agents such as hydrocarbon, fatty acid, higher alcohol, aliphatic amide, metal soap, ester, etc. are added in an amount of 0.01 to 0.5. Addition by mass% is preferable because a film with improved slip properties can be obtained. Among these, when a combination system of erucic acid amide with immediate effect and delayed-acting behenic acid amide is used, stability of winding of the film at the time of film formation by subsequent erucic acid amide and subsequent cutting processing, printing The laminate workability can be improved, while the slow-acting behenic acid amide that is hardly adsorbed by the adhesive can improve the slipperiness and anti-blocking properties after dry lamete.

  Further, in the sealing layer, high density polyethylene, dibenzylidene sorbitol, methyl substituted dibenzylidene sorbitol, hydroxy-di-aluminum, bissorbicyl, bis-sodium methylene bis-acid phosphate sodium Addition of 0.01 to 1.0% by weight of various known crystallization nucleating agents such as salt suppresses the generation of roll marks during film formation, and provides slip and blocking properties immediately after film formation. Is preferable because an improved film can be obtained. Among these, the use of a polyethylene crystallization nucleating agent that is relatively easy to add and has no problem with odor can improve the quality and processability immediately after the film forming process in a well-balanced manner.

  It is preferable to add 0.01 to 1% by mass of various known anti-blocking agents to the laminate layer because a film with improved anti-blocking property of the film product roll can be obtained.

  In addition, as a method for adding these additives and polymers, a method of directly feeding into an extruder at the time of film formation is possible, but a master batch using a polymer used in the present invention as a base resin is prepared in advance. A method of feeding this master batch into an extruder during film formation is preferred.

  In the present invention, the haze measured as a transparency index is preferably 10% or less.

  In the present invention, the boil puncture ratio of the laminate with the biaxially stretched polyamide film measured as an index of impact resistance is preferably 10% or less, and the laminate with the biaxially stretched polyamide film and the biaxially stretched polypropylene film. The boil puncture rate is preferably 10% or less.

  In the present invention, the seal temperature is preferably 140 ° C. or lower.

  In the present invention, the blocking resistance is preferably 8 mN or less, more preferably 5 mN.

  The manufacturing method of said resin (A) concerning this invention, resin (B), and resin (C) is not limited. It can be produced by various known methods, for example, using a Ti-based Ziegler catalyst whose main component is Ti, Mg, Cl or the like. However, as described above, the propylene / α-olefin random copolymer resin (A) is particularly preferably a resin produced using a single site catalyst. The single site catalyst is a catalyst having a uniform active site (single site), and examples thereof include a metallocene catalyst (so-called Kaminsky catalyst) and a Brookhart catalyst. For example, a metallocene catalyst is a catalyst comprising a metallocene transition metal compound, at least one compound selected from the group consisting of an organoaluminum compound and a compound that forms an ion pair by reacting with the metallocene transition metal compound, and an inorganic substance. It may be carried on.

In a propylene / α-olefin random copolymer resin, it is common to increase the content of α-olefin in order to lower the sealing start temperature. However, when the content of α-olefin is increased, the film becomes soft and the blocking resistance is deteriorated.
On the other hand, the molecular weight distribution of the resin (expressed by the ratio of the mass average molecular weight Mw to the number average molecular weight Mn) increases the molecular weight distribution as the value increases, so the low molecular weight product increases and the blocking resistance deteriorates. To do. Therefore, in order to balance low-temperature heat sealability and blocking resistance, it is effective to narrow the molecular weight distribution of the resin and reduce low molecular weight products. In order to narrow this molecular weight distribution, it is effective to perform polymerization using a single site catalyst having uniform activity.

  Although the thickness of the laminated propylene-based unstretched film of the present invention is variously determined depending on the application, it is usually in the range of 10 to 500 μm, preferably 20 to 100 μm. The thickness ratio of each layer is preferably 5 to 40% for the seal layer, 30 to 80% for the core layer, and 10 to 30% for the lami layer. Furthermore, the ratio of the sealing layer is more preferably 10 to 35%, the ratio of the core layer is 40 to 75%, and the ratio of the lami layer is more preferably 15 to 25%.

  If the thickness ratio of the seal layer is less than 10%, the low-temperature sealability is deteriorated, which is not preferable. Conversely, if it exceeds 40%, blocking resistance and film rigidity are lowered, which is not preferable.

  If the thickness ratio of the core layer is less than 30%, the rigidity of the film decreases, which is not preferable. On the other hand, if it exceeds 80%, the resistance to aerated boil puncture is lowered, which is not preferable.

  When the thickness ratio of the laminate layer is less than 10%, the resistance to aerated boil puncture is lowered. Conversely, if it exceeds 30%, the transparency deteriorates, which is not preferable.

  In the present invention, the tensile strength, which is an index of film rigidity, is preferably 400 MPa or more, more preferably 450 MPa or more, and particularly preferably 480 MPa or more.

  The laminated propylene-based unstretched film of the present invention can employ various known film forming methods such as an inflation method and a T-die method. In addition, such laminated films may be individually laminated after film formation, but the method of film formation by coextrusion using a multilayer die having a three-layer structure is most preferable. Examples of the method for co-extrusion film formation include lamination using a feed block and a method using a multi-manifold die.

  The laminated propylene-based unstretched film of the present invention is subjected to an oxidation treatment by corona treatment, flame treatment, plasma treatment, or the like on the side surface of the laminated layer in order to improve the printability or adhesion to other films. A surface activation treatment such as a coating treatment may be performed.

The laminated propylene-based unstretched film of the present invention obtained by the above method may be used alone as various packaging materials, but is preferably used as a sealant film by being bonded to another base film.
The base film is preferably made of a sheet or film made of a thermoplastic resin. As the thermoplastic resin, various known thermoplastic resins such as polyolefin (polyethylene, polypropylene, poly-4-methyl / 1-pentene, polybutene, etc.), polyester (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyamide (Nylon-6, nylon-66, polymetaxylene adipamide, etc.), polyvinyl chloride, polyimide, ethylene / vinyl acetate copolymer or saponified product thereof, polyvinyl alcohol, polyacrylonitrile, polycarbonate, polystyrene, ionomer, or these And the like. Of these, thermoplastic resins having good stretchability and transparency, such as polypropylene, polyethylene terephthalate, and polyamide, are preferable. In addition, the base material made of such a thermoplastic resin film may be an unstretched film or a stretched film, or one or more types of coextrusion molding, extrusion laminating, dry laminating, thermal laminating, etc. The laminated body obtained by this may be sufficient. Moreover, in order to improve the adhesiveness of one side or both sides of the base material layer with the laminated propylene-based unstretched film of the present invention, for example, surface activation treatment such as corona treatment, flame treatment, plasma treatment, undercoat treatment, etc. You may keep going. The thickness of the base material layer is usually in the range of 5 to 500 μm, preferably 7 to 70 μm.

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

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

1. Melt flow rate [MFR]
(2004 edition) Measured according to JIS K7210 by the method of Condition-14 (load 2.16 kg, temperature 230 ° C.).

2. Melting point About 6 mg of propylene-based copolymer (C) was weighed and heated to 200 ° C. at a rate of temperature increase of 10 ° C./min using a differential scanning calorimeter (type 5200) manufactured by Seiko Denshi Kogyo Co., Ltd. , Held at 200 ° C. for 5 minutes, then cooled down to 0 ° C. at 100 ° C./min, and again measured the melting curve when the temperature was raised from 0 ° C. to 200 ° C. at 10 ° C./min. Then, from this melting curve, the method of (2004 version) JIS-K-7121 9.1 was followed, and the temperature at the top of the melting peak on the highest temperature side was melted from the melting curve.

3. Ratio of xylene soluble part at 20 ° C (%)
After 5 g of the sample was completely melted in 500 ml of boiling xylene, the temperature was lowered to 20 ° C. and left for 4 hours or more. Thereafter, the precipitate and the solution were separated by filtration, and the filtrate was dried and dried at 70 ° C. under reduced pressure. From the mass of the obtained dried product, the 20 ° C. xylene-soluble part amount was measured, and the ratio was determined.

4). Ethylene content The ethylene content was measured by ¹³ C-NMR method according to the method described on page 616 of Polymer Handbook (1995, published by Kinokuniya Shoten).

5. The haze was measured using “Haze Tester J” manufactured by Toyo Seiki Seisakusho in accordance with JIS-K-6714 of 2004 edition.

6). Blocking resistance In accordance with ATM-D1893-67, a load of 90N was applied to the area of A4 size, left for 2 hours in an atmosphere of 60 ° C., and then the load was removed. Measured with

7). Sealing temperature Make the sealing surfaces face each other, and place biaxially stretched polyester film (Toyobo Ester Co., Ltd. “Toyobo Ester” film [E5100 12 μm]) on both sides, and use a thermal gradient type 5-point sealer. Sealing was performed at a pressure of 0.2 MPa for 1 second, and the sealing strength was measured at a width of 15 mm. Create a graph where the seal temperature is 5 points on a 5 ° C pitch of 120 ° C to 140 ° C and the temperature is on the horizontal axis and the seal strength is on the vertical axis. The temperature at which the seal strength reaches 4.9 N / 15 mm (500 g / 15 mm) It was read on the graph and this temperature was defined as the seal temperature.

8). Tensile modulus According to 2004 edition JIS K7127, sample shape conforms to No. 1 test piece (sample length 200 mm, sample width 15 mm, chuck distance 100 mm), MD with crosshead speed of 500 mm / min. It measured about the direction (film longitudinal direction). Unit MPa.

9. Aerobic boil resistance of laminate with base film (1) Two-layer laminate A biaxially stretched polyamide film (Toyobo “Harden” film N6062 25 μm) and a polypropylene-based unstretched composite film , Using a polyester urethane adhesive (main agent: Taketake A310 “Takelac A310”, hardener: Takeda A3 “Takenate A3” mixed at a ratio of 3: 1), and the solid content concentration of the adhesive is 2.5 g. / M ² was applied, and dry lamination was performed according to a conventional method to obtain a two-layer laminate. The obtained two-layer laminated body was formed into a three-side sealed bag having an inner size of 13 cm × 13 cm and an outer size of 14 cm × 14 cm. The sealing conditions were a pressure of 0.2 MPa, a time of 1 second, and a temperature of 200 ° C. The interior was filled with 200 cc of water and 200 cc of air, and sealed under the same sealing conditions. This sealed bag was boiled for 60 minutes to determine the boil puncture rate.
(2) Three-layer laminated body A biaxially stretched polyamide film (Toyobo's “Harden” film N6062 25 μm) that has been subjected to water-resistant and easy-adhesion treatment, instead of water-resistant and easy-adhesion treatment. Harden ”film N6062 15 μm) and non-static type biaxially stretched polypropylene film (Toyobo“ Pyrene ”film P2102 20 μm) polyester urethane adhesive (main agent: Takeda Atake“ Takelac A310 ”, curing agent: Takeda "Takenate A3" made by mixing at a ratio of 3: 1) was applied so that the solid content concentration of the adhesive was 2.5 g / m ^2, and a laminate obtained by dry lamination according to a conventional method was used. Then, a polypropylene unstretched composite film was dry laminated on the biaxially stretched polyamide film side of the laminate. Sought and obtained a three-layer structure laminate by laminating the same manner, further likewise filled, boiled puncture rate by boiling treatment (1).
(3) Method for obtaining boil puncture rate Boil puncture rate (%) = (number of torn bags / number of sealed bags tested: 100 bags) × 100

10. Film, seal layer, and lami layer thickness measurements Film cross sections were cut out and measured with an optical microscope in reflected light.

Resins used in Examples and Comparative Examples are as follows: Resin (A): Propylene / ethylene random copolymer polymerized with metallocene catalyst (ethylene content = 4 mass%, MFR = 7)
Resin (B): Propylene / ethylene block copolymer (ethylene content = 6 mass%, MFR = 2.5)
Resin (C): Propylene-based copolymer (ethylene content = 10 mass%, 20 ° C. xylene soluble part 10%, melting point 140 ° C., MFR = 3)

Example 1
As a laminate layer, a composition comprising 60% by mass of resin (A), 20% by mass of resin (B), 20% by mass of resin (C), 600 ppm of amorphous silica (Silycia 550) having an average particle diameter of 3 μm, and 400 ppm of erucamide. A composition comprising, as a base layer, 70% by mass of resin [A] having an ethylene content of 4% by mass, 5% by mass of resin (B), 25% by mass of resin (C), and 300 ppm of erucamide, As a sealing layer, resin (A) 88% by mass, resin (C) 12% by mass, amorphous silica (Silycia 550) having an average particle diameter of 3 μm, 2000 ppm, spherical silica having an average particle diameter of 4 μm, 1000 ppm, erucic acid amide 600 ppm, behenine A composition comprising 200 ppm of acid amide was melt extruded using a separate extruder, and the T-die outlet resin temperature was 250 ° C. Degrees 50 m / min, and T-die cast under the conditions of a cooling roll temperature 30 ° C., to obtain laminate layer thickness 10 [mu] m, the base layer thickness of 20 [mu] m, the polypropylene-based non-stretched composite film of the sealing layer thickness of 10 [mu] m. The properties of the obtained film are shown in Table 1.
The average particle size of the inorganic particles was measured using a laser diffraction particle size distribution measuring device (Nikkiso Microtrack HRA model 9320-X100) manufactured by Lees & Northrup, and displayed as a volume average particle size.
In addition, the above-mentioned amorphous silica, spherical silica, erucic acid amide, and behenic acid amide are each prepared as a master batch previously added to the resin (A) at a high concentration, and the additive concentration becomes a predetermined value during melt extrusion. The masterbatch was added as follows.

(Examples 2 and 3 and Comparative Examples 1 and 2)
A resin composition was obtained in the same manner as in Example 1 except that the resin composition of the laminate layer was as described in Table 1. The properties of the obtained film are shown in Table 1.

(Comparative Examples 3 and 4) A resin composition was obtained in the same manner as in Example 1 except that the resin composition of the base layer was as described in Table 1. The properties of the obtained film are shown in Table 1.

(Comparative Examples 5 and 6)
A resin composition was obtained in the same manner as in Example 1 except that the resin composition of the seal layer was as described in Table 1. The properties of the obtained film are shown in Table 1.

The films described in Examples 1 to 3 satisfy the low-temperature heat-sealing property, the blocking resistance, and the rigidity of the film at the same time, and are excellent in the aeration boil puncture resistance. On the other hand, the comparative example 1 with a small amount of the resin (A) in the laminate layer is deteriorated in transparency, and the comparative example 2 in which the laminate layer is only the resin (A) is extremely inferior in the aerated boil puncture resistance. Moreover, the comparative example 3 whose core layer is only resin (A) is inferior in aeration boil puncture resistance, and the comparative example 4 with a low ratio of the resin (A) in the core layer is deteriorated in transparency. Further, Comparative Example 5 having a high resin (A) ratio in the heat seal layer is inferior in low-temperature sealability, and Comparative Example 6 having a low resin (A) ratio in the heat seal layer is significantly deteriorated in blocking resistance.

  The results are shown in Table 1.

  The laminated polypropylene-based unstretched film of the present invention has both low-temperature heat sealability and blocking resistance, and is excellent in impact resistance at low temperatures. For example, it was used as a laminate with a polyamide film or a biaxially stretched polypropylene film. Has the advantage of being able to withstand severe treatments such as boiling water treatment and retort treatment, especially extremely extreme treatments such as aerated boil treatment, such as sealed packaging of raw noodles It can be suitably used as a sealant film for packaging that is sterilized by heating in a state. Therefore, it is important to contribute to the industry.

Claims (2)

A laminated polypropylene-based unstretched film comprising three layers of a laminate layer, a core layer, and a seal layer, wherein the laminated polypropylene-based unstretched films are laminated in the above order, and each layer comprises at least the following resin composition.
(1) The laminate layer has a propylene / α-olefin random copolymer resin (A) having an α-olefin content of 2 to 8% by mass of 40 to 70% by mass and an α-olefin content of 3 to 10% by mass. Propylene / α-olefin block copolymer resin (B) and / or xylene soluble part at 20 ° C. is 5 to 12% by mass, melting point is 130 to 150 ° C., and ethylene content is 6 to 15 Propylene / ethylene block copolymer resin (C) 30% to 60% by mass.
(2) The core layer has an α-olefin content of 2 to 8% by mass of propylene / α-olefin random copolymer resin (A) of 60 to 85% by mass and an α-olefin content of 3 to 10% by mass. The propylene / α-olefin block copolymer resin (B) and / or 20 has a xylene soluble part of 5 to 12 mass%, a melting point of 130 to 150 ° C., and an ethylene content of 6 to 15 mass. % Propylene / ethylene block copolymer resin (C) 15 to 40% by mass.
(3) The seal layer has 80 to 90% by mass of propylene / α-olefin random copolymer resin (A) having an α-olefin content of 2 to 8% by mass and 5 to 5 parts of xylene soluble at 20 ° C. It consists of 10 to 20% by mass of a propylene / ethylene block copolymer resin (C) having 12% by mass, a melting point of 130 to 150 ° C., and an ethylene content of 6 to 15% by mass.   The laminated polypropylene-based unstretched film according to claim 1 or 2, wherein the propylene / α-olefin random copolymer resin (A) is polymerized using a single site catalyst.