JP2006103147A - Laminated film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated film free of the generation of appearance defects such as a scaly pattern, good in blocking resistance performance, and excellent in transparency, moisture proof and heat seal characteristics. <P>SOLUTION: The laminated film has a structure formed by laminating a first layer consisting of a polyolefin resin A that at least has a molecular weight distribution W<SB>A</SB>of 3.5 or less and a second layer that comes into contact with the first layer and consists of a polyolefin resin B, and the fluidity parameter indicated by η<SB>0B</SB>/η<SB>0A</SB>×W<SB>B</SB>/W<SB>A</SB>satisfies formula (1). In formula (1) η<SB>0A</SB>and η<SB>0B</SB>each indicate a zero shear viscosity of the polyolefin resin A and that of the polyolefin resin B, and W<SB>A</SB>and W<SB>B</SB>indicate molecular weight distributions (Mw/Mn) of the polyolefin resin A and the polyolefin resin B, respectively. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyolefin-based laminated film, and in particular, relates to a polyolefin-based laminated film that does not cause poor appearance (scaly pattern), has good anti-blocking performance, and has excellent transparency, moisture resistance, and heat seal characteristics. .

Polyolefin films are widely used as packaging materials for foods, fibers and the like because they have good transparency, mechanical properties, and moisture resistance. Polyolefin-based films used for packaging materials are required to have heat-sealing properties, and heat-sealable films used for packaging materials are generally laminated with low-melting-point polyolefin-based resins on polypropylene-based resins. Co-extruded laminated polypropylene resin films, unstretched polyethylene resin films, or laminated polypropylene resin films obtained by laminating a polypropylene resin film and a stretched polypropylene resin film are frequently used.
In recent years, low-melting-point sealant resins polymerized with metallocene-based catalysts have emerged, improving heat seal characteristics, and preventing problems such as film stickiness (blocking) and deterioration of transparency over time Is being used. However, when a polypropylene resin polymerized with a metallocene catalyst is used, appearance defects such as sharkskin and melt fracture occur at the die exit when a co-pressed film is produced, the optical properties are significantly deteriorated, and the use is restricted. There was a case.

  In order to solve such problems, a base material layer A made of a crystalline polypropylene resin, an intermediate layer B, and a heat fusion layer C having a melting point of 150 ° C. or lower are sequentially laminated, and the melt flow of the base material layer A The rate (MFR (A)), the melt flow rate (MFR (B)) of the intermediate layer B, and the melt flow rate (MFR (C)) of the thermal fusion layer C are MFR (C) ≧ 2 × MFR (A) ≧ A laminated biaxially oriented polypropylene system that satisfies MFR (B) and that the resin that forms the intermediate layer B contains at least one resin that forms the base layer A and one that forms the thermal fusion layer C. Resin films have been proposed (see, for example, Patent Document 1). According to Patent Document 1, “the MFR of the intermediate layer B is not more than twice the MFR of the base layer A, but is preferably not less than the value of the MFR of the base layer A and not more than twice. When the MFR of the layer B is larger than twice the MFR of the base layer A, when the base layer A, the intermediate layer B, and the heat fusion layer C are melt-coextruded, the resin flow between the layers Difference between the layers, scaly spots between the layers, and the transparency tends to deteriorate, and the intermediate layer B tends to deform due to heat at the time of heat sealing, so that wrinkles and the like are generated. On the other hand, even when the MFR of the intermediate layer B is smaller than the MFR of the base layer A, when the base layer A, the intermediate layer B, and the heat fusion layer C are melt coextruded, There is a difference in flow, scaly spots between each layer, and transparency tends to deteriorate. ” To have. However, in the above invention, when a sealant resin having a narrow molecular weight distribution such as metallocene-based polypropylene is used, the appearance defect is hardly improved.

On the other hand, a method for improving the appearance defect of a tatami-shaped pattern appearing on the film surface using a resin composition obtained by blending two types of polypropylene polymer resins having different die swell ratios has been proposed (for example, (See Patent Document 2). However, in the method of Patent Document 2, it is possible to improve “the appearance defect caused by the unstable phenomenon of the interlayer interface” (hereinafter, this phenomenon is referred to as a scale pattern) that may occur when a multilayer film is manufactured. There is a problem that can not be.
Japanese Patent Laid-Open No. 2003-225979 JP 2002-80656 A

  In view of the above-mentioned problems, the object of the present invention is to produce a laminated film without causing appearance defects such as scaly patterns, good anti-blocking performance of the film, and excellent transparency, moisture resistance, and heat seal characteristics. It is to provide a laminated film.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have a laminate composed of two layers of polyolefins in which the fluidity parameter represented by the relationship between a specific molecular weight distribution and zero shear viscosity has a specific relationship. The present invention has been completed by finding that the film does not generate a scale pattern, has a good anti-blocking performance, and is a laminated film having excellent transparency, moisture resistance, and heat seal characteristics.

That is, according to the first aspect of the present invention, a first layer at least a molecular weight distribution W _A consists of 3.5 or less of the polyolefin resin A, in contact with the first layer, the second layer of polyolefin resin B There is provided a laminated film characterized by having a laminated structure and a fluidity parameter represented by η _0B / η _0A × W _B / W _A satisfying the following formula (1).

（式（１）中、η_０Ａ、η_０Ｂはそれぞれポリオレフィン系樹脂Ａ、ポリオレフィン系樹脂Ｂのゼロせん断粘度を表し、Ｗ_Ａ、Ｗ_Ｂはそれぞれポリオレフィン系樹脂Ａ、ポリオレフィン系樹脂Ｂの分子量分布（Ｍｗ／Ｍｎ）を表す。）

(In the formula _{(1), η 0A, η} 0B each represents a polyolefin resin A, the zero shear viscosity of the polyolefin resin _B, W A, _{W B} are each the polyolefin resin A, the molecular weight distribution of the polyolefin resin B ( Mw / Mn).)

  According to a second aspect of the present invention, there is provided a laminated film characterized in that, in the first aspect, the polyolefin resin A and the polyolefin resin B are polypropylene resins.

  According to the third invention of the present invention, in the first invention, the polyolefin resin B has a melt flow rate (MFR) of 0.01 g / 10 min or more and 4 g / 10 min or less of polypropylene (b1) and MFR. Is a polypropylene resin composition containing 20 g / 10 min or more and 100 g / 10 min or less of polypropylene (b2).

  According to a fourth aspect of the present invention, there is provided a laminated film characterized in that, in the first aspect, the polyolefin resin A comprises a propylene / α-olefin random copolymer as a main component.

  According to a fifth aspect of the present invention, there is provided a laminated film according to the fourth aspect, wherein the propylene / α-olefin random copolymer is a polymer produced by a metallocene catalyst. .

  According to a sixth aspect of the present invention, there is provided a laminated film characterized in that in any one of the first to fifth aspects, the laminated film is obtained by a co-pressing method.

  According to a seventh aspect of the present invention, there is provided the laminated film according to any one of the first to fifth aspects, wherein the laminated film is stretched at least in a uniaxial direction.

  ADVANTAGE OF THE INVENTION According to this invention, the appearance defect called the scaly pattern by the instability of the interface of an interlayer does not generate | occur | produce, transparency, the anti-blocking performance of a film is favorable, and the laminated film excellent in the heat seal characteristic is provided.

  The present invention is a laminated film having a structure in which a first layer made of polyolefin resin A and a second layer made of polyolefin resin B are laminated. The constituent resin components and the layer configuration will be described in detail below.

1. Resin constituting laminated film (1) Polyolefin resin A
Specifically, the polyolefin resin A used for the laminated film of the present invention is a homopolymer of α-olefin such as ethylene or propylene or a copolymer between α-olefins, such as ethylene homopolymer, polypropylene. Homopolymer, polybutene-1, propylene / α-olefin copolymer (for example, propylene / ethylene copolymer, propylene / 1-butene copolymer, propylene / 1-hexene copolymer, propylene / 4-methyl- 1-pentene copolymer, propylene / ethylene / 1-butene copolymer), ethylene / α-olefin copolymer (for example, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / 1- Hexene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene / propylene / 1-hexene Polymers, ethylene-1-butene-1-hexene copolymer) and the like.
Among these, a polypropylene homopolymer and a propylene / α-olefin copolymer are preferable, and a propylene / α-olefin copolymer is particularly preferable.

A particularly preferred propylene / α-olefin copolymer is a copolymer resin of propylene and an α-olefin having 2 to 12 carbon atoms other than propylene and the like that does not lose crystallinity, and a plurality of them selected from them. Resin. Examples of the α-olefin include one or more α-olefins selected from ethylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and the like.
Copolymerization is performed for the purpose of controlling heat sealability, and the content of repeating units derived from monomers other than propylene is 10% by weight or less in the case of ethylene, and α- having 4 to 12 carbon atoms. In the case of olefin, 30% by weight or less is preferable. Among these, the content of a repeating unit derived from ethylene is a random copolymer resin of propylene and ethylene having a content of 10% by weight or less, and the content of a repeating unit derived from an α-olefin having 4 to 12 carbon atoms. Random copolymer resin of propylene having an amount of 30% by weight or less and an α-olefin having 4 to 12 carbon atoms, the content of repeating units derived from ethylene being 10% by weight or less and 4 to 12 carbon atoms A ternary random copolymer resin of propylene, ethylene and an α-olefin having 4 to 12 carbon atoms, in which the content of repeating units derived from the α-olefin is 30% by weight or less is more preferably used. . As the α-olefin in the case of 4 to 12 carbon atoms, 1-butene is particularly preferable.

The polyolefin resin A used in the laminate film of the present invention has a molecular weight distribution (Mw / Mn) of 3.5 or less, preferably 3.25 or less, more preferably 3 to 2. When the molecular weight distribution of the polyolefin resin A is 4 or more, the anti-blocking performance is inferior.
Here, the molecular weight distribution (Mw / Mn) is a ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) obtained by measurement by gel permeation chromatography (GPC) method. Ask for.
Conversion from the retention volume to the molecular weight is performed using a calibration curve prepared in advance with standard polystyrene.
Standard polystyrenes used are F380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, and A1000, all of which are manufactured by Tosoh Corporation. A calibration curve is created by injecting 0.2 mL of a solution dissolved in ODCB (containing 0.5 mg / mL BHT) to 5 mg / mL. The calibration curve uses a cubic equation obtained by approximation by the least square method. The viscosity equation [η] = K × M ^α used for conversion to molecular weight uses the following numerical values.
PS: K = 1.38 × 10 −4, α = 0.7
PP: K = 1.03 × 10−4, α = 0.78
The measurement conditions for GPC are as follows.
Apparatus: Waters GPC (ALC / GPC 150C)
Detector: MIRAN 1A IR detector manufactured by FOXBORO (measurement wavelength: 3.42 μm)
Column: AD806M / S (3 pieces) manufactured by Showa Denko KK
Mobile phase solvent: o-dichlorobenzene Measurement temperature: 140 ° C
Flow rate: 1.0 ml / min Injection volume: 0.2 ml
Sample preparation: Prepare a 1 mg / mL solution using ODCB (containing 0.5 mg / mL BHT) and dissolve at 140 ° C. for about 1 hour.
The baseline and section of the obtained chromatogram are performed as shown in FIG.

The MFR (230 ° C., 2.16 kg load) of the polyolefin resin A used in the present invention is preferably 0.4 to 100 g / 10 minutes, more preferably 0.5 to 50 g / 10 minutes, and further preferably 1 to 20 g. / 10 minutes, particularly preferably 2 to 10 g / 10 minutes.
The melting peak temperature (Tm) by DSC of the polyolefin resin A is preferably 110 ° C. ≦ Tm ≦ 140 ° C., more preferably 115 ° C. ≦ Tm ≦ 135 ° C. If Tm is less than 110 ° C., stickiness of the film may occur. In such a case, the suitability for high-speed automatic packaging is inferior. If it exceeds 140 ° C., the low-temperature heat sealability is hardly exhibited.
Further, the melting end temperature (Te) of the polyolefin resin A by DSC is preferably Te−Tm ≦ 8 ° C., and more preferably satisfies Te−Tm ≦ 7.8 ° C. Copolymers with Te-Tm exceeding 8 ° C. may have insufficient heat-seal startup properties.
Furthermore, the extraction amount of the polyolefin resin A extracted at 40 ° C. using orthodichlorobenzene as a solvent is preferably 2.0% by weight or less, more preferably 1.5% by weight or less. A copolymer having an extraction amount of more than 2% by weight extracted at 40 ° C. using orthodichlorobenzene as a solvent may cause stickiness of the film. In such a case, the high-speed automatic packaging suitability is inferior.

The method for producing the polyolefin resin A is not particularly limited, and examples thereof include a gas phase polymerization method and a solvent polymerization method.
The polymerization catalyst is not limited, and a Ziegler catalyst having titanium and halogen as essential components, a metallocene catalyst having a coordination metal compound having a cyclopentadienyl skeleton as essential components, and the like are used. A metallocene catalyst is preferably used as a catalyst that easily provides a narrow molecular weight distribution.

(2) Polyolefin resin B
Specifically, the polyolefin resin B used in the laminated film of the present invention is an α-olefin homopolymer such as ethylene or propylene, or a copolymer between α-olefins, for example, an ethylene homopolymer, Polypropylene homopolymer, polybutene-1, propylene / α-olefin copolymer (for example, propylene / ethylene copolymer, propylene / 1-butene copolymer, propylene / 1-hexene copolymer, propylene / 4-methyl -1-pentene copolymer, propylene / ethylene / 1-butene copolymer), ethylene / α-olefin copolymer (for example, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / 1) -Hexene copolymer, ethylene 4-methyl-1-pentene copolymer, ethylene propylene 1-hex Emissions copolymer, ethylene-1-butene-1-hexene copolymer) and the like.
Among these, a polypropylene homopolymer and a propylene / α-olefin copolymer are preferable, and a propylene / α-olefin copolymer is particularly preferable. Further, it is preferably the same type of resin as the polyolefin resin A. When different types of resins are combined, the delamination strength between the first layer and the first layer may be inferior, and the application is limited.

The polyolefin-based resin B is selected from the above-mentioned resins, but the fluidity parameter represented by η _0B / η _0A × W _B / W _A in relation to the polyolefin-based resin A is represented by the following formula (1 ), Preferably satisfying the following formula (1 ′), more preferably satisfying the following formula (1 ″).

Equation (1), the formula (1 '), wherein _{(1 "), η 0A,} η 0B represents each polyolefin resin A, the zero shear viscosity of the polyolefin resin _B, W A, _{W B,} respectively polyolefin The molecular weight distribution (Mw / Mn) of resin A and polyolefin resin B is represented.

  When the fluidity parameter is 1 or less, the melt fluidity of each resin will be remarkably different. In the case of co-extrusion, a difference occurs in the flow of each layer resin, resulting in an unstable state at the interlayer interface. Will occur and the appearance will be significantly deteriorated. Furthermore, since the problem that the film thickness of a laminated | multilayer film is not stabilized arises, it is unpreferable practically. On the other hand, when the fluidity parameter exceeds 9, as in the above description, there is a difference in the flow of the resin in each layer, and a scale pattern is generated due to the unstable state of the interlayer interface, so that the appearance is remarkably deteriorated. Not preferable.

Here, the molecular weight distribution (Mw / Mn) is a value measured by the method described above, and the zero shear viscosity is a value measured as follows.
For the zero shear viscosity η ₀ , the frequency (ω) dependence of the dynamic melt viscosity at 240 ° C. is measured using the apparatus described below.
Apparatus: Mechanical spectrometer RMS800 manufactured by Rheometrics
Temperature: 240 ° C
Fixing jig: 25mmφ parallel plate Measurement mode: Frequency sweep Gap: 1.5mm
Frequency: 0.01-100 rad / s
Distortion: 10%
A zero shear viscosity (η ₀ ) is obtained by approximating the obtained nonlinear curve of viscosity and frequency with the following model equation (2).

（式（２）中、ηはある周波数ωにおける粘度を表し、η_０はゼロせん断粘度、λは緩和時間、ｎはパワーロー指数である。）

(In the formula (2), η represents the viscosity at a certain frequency ω, η ₀ is zero shear viscosity, λ is a relaxation time, and n is a power low index.)

The polyolefin resin A and the polyolefin resin B that satisfy the above formula (1) may be selected by any method, but can be performed, for example, by the following procedure.
The polyolefin resin A to be used for the first layer is determined. Then eta _0A of the polyolefin resin A, since _{W A} is uniquely determined, such eta _0B to satisfy equation (1), the range of _{W B} are determined. A matching polyolefin resin B can be prepared by combining a commercial product or a commercial product.
Since W is a molecular weight distribution, the molecular weight distribution of the polyolefin-based resin B is more likely to satisfy the formula (1) when the molecular weight distribution of the polyolefin-based resin A is wider. Further, since the zero shear stress shows a higher value as the amount of the high molecular weight component is larger, the polyolefin resin B is more likely to satisfy the formula (1) if it contains more high molecular weight component than the polyolefin resin A. Here, the high molecular weight component corresponds to a component having a weight average molecular weight of about 30 × 10 ⁵ or more, and the polyolefin resin B contains 15% or more, preferably 20 to 60%. .

The polyolefin resin B is preferably a resin composition containing a polypropylene (b1) having an MFR of 0.01 to 4 g / 10 min and a polypropylene (b2) having an MFR of 20 to 100 g / 10 min.
More preferably, MFR of polypropylene (b1) is 0.1 to 3.5 g / 10 minutes, and further preferably 0.5 to 3.0 g / 10 minutes.
More preferably, the MFR of polypropylene (b2) is 25 to 90 g / 10 minutes, and further preferably 30 to 75 g / 10 minutes.
The composition ratio of polypropylene (b1) and polypropylene (b2) is b1 / b2 = 90 wt% / 10 wt% to 30 wt% / 70 wt%, preferably 85 wt% / 15 wt% to 35 wt% / 65 wt% %, More preferably 80% by weight / 20% by weight to 40% by weight / 60% by weight. This polyolefin resin B was obtained by multistage polymerization including the step of producing (b1) and the step of producing (b2), even if it was a blend of the above polypropylene (b1) and polypropylene (b2). May be.

(3) Other components At least one of the first and second layers comprising the polyolefin resin A and the polyolefin resin B constituting the laminated film of the present invention is added to the film resin as long as the effects of the present invention are not hindered. An additive such as an antioxidant, and a modifier such as an elastomer and an alicyclic hydrocarbon resin can be appropriately added. For example, 2,6-di-t-butyl-p-cresol (BHT), tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (IRGANOX 1010) and n -Phenol stabilizer represented by octadecyl-3- (4'-hydroxy-3,5'-di-t-butylphenyl) propionate (IRGANOX 1076), bis (2,4-di-t-butylphenyl) Phophite stabilizers typified by pentaerythritol diphosphite and tris (2,4-di-t-butylphenyl) phosphite, lubricants typified by higher fatty acid amides and higher fatty acid esters, carbon atoms of 8 to 22 Antistatic agents such as glycerin esters, sorbitan acid esters and polyethylene glycol esters of fatty acids, Anti-blocking agent represented by Rica, calcium carbonate, talc, etc., ethylene-α-olefin copolymer, low density polyethylene, polyethylene resin represented by high density polyethylene, petroleum resin, terpene resin, rosin resin, Coumarone indene resins and alicyclic hydrocarbon resins represented by hydrogenated derivatives thereof may be added.

2. Laminated film The laminated film of the present invention has a structure in which a first layer made of the polyolefin resin A and a second layer made of a polyolefin resin B in contact with the first layer are laminated. Although the thickness of the whole laminated film is determined according to the use, it is 5-100 micrometers normally, Preferably it is the range of 10-60 micrometers. The ratio of the first layer to the second layer is usually 1 to 20%, preferably 1.5 to 10%.

  The laminated film can be obtained by coextrusion of a resin constituting each layer. A known method can be used without limitation as the co-pressing method, and examples thereof include a T-die method and an inflation method.

The laminated film may be a stretched film or an unstretched film.
In the case of a stretched film, it is preferably stretched in at least a uniaxial direction. As the stretching method, a method of co-extrusion of the resin constituting each layer and then biaxial stretching is adopted.
The stretching ratio is preferably 3 to 6 times for MD and 8 to 12 times for TD. If the draw ratio is 3 times in MD and less than 8 times in TD, the tensile elastic modulus of the film becomes small, and if the draw ratio is 6 times in MD and more than 12 times in TD, the heat shrinkage rate becomes large.

Moreover, it is important to employ | adopt the temperature conditions which suppress the orientation of the said highly crystalline polypropylene, and extending | stretching to MD and TD is generally performed by setting extending | stretching temperature to high temperature. The stretching temperature varies depending on the characteristics of the film forming machine, but for example, it is 150 ° C. to 165 ° C., preferably 156 ° C. to 160 ° C. in MD. When the stretching temperature is lower than 150 ° C., the thermal shrinkage rate is increased, and it becomes difficult to obtain a stretched film. When the stretching temperature is higher than 165 ° C., the MD sheet sticks to the roll.
On the other hand, the stretching temperature of TD is 160 ° C to 190 ° C, preferably 170 ° C to 180 ° C. When the stretching temperature is lower than 160 ° C, the thermal shrinkage rate is increased. When the stretching temperature is higher than 190 ° C, the film is whitened and the transparency is lowered.
The TD relaxation rate is 0 to 8%, preferably 0 to 3%. If it is larger than 8%, the orientation in the TD direction becomes too small, and as a result, the thermal contraction rate in the MD direction increases.

  Biaxially stretched laminated film can also be subjected to relaxation heat treatment during secondary processing after film formation to further reduce the heat shrinkage rate, but as described above, the film surface becomes rough and the appearance becomes poor. In addition, the transparency is likely to be lowered, and the rigidity expressed by the tensile elastic modulus is also liable to be lowered. Therefore, in the method of the present invention, it is most preferable not to perform heat relaxation treatment after film formation.

  The laminated film of the present invention has at least a first layer / second layer structure as described above, but may further have other layers depending on the purpose of use. Another resin layer, for example, a gas barrier resin layer such as saponified ethylene-vinyl acetate copolymer or polyvinyl alcohol, may be further laminated on at least one surface of the two layers. When providing other layers, a method of co-extrusion by T-die method or inflation method using an extruder suitable for the number of layers, dry lamination method, wet lamination method, etc. For example, a method for extrusion-coating another layer on the laminated film of the present invention, and a method for co-extrusion coating the laminated film of the present invention on another layer.

  The laminated film of the present invention can be subjected to a surface treatment in order to improve printing properties, laminating properties and the like. Examples of the surface treatment method include corona discharge treatment, plasma treatment, flame treatment, and acid treatment, and are not particularly limited. It is preferable to perform a corona discharge treatment, a plasma treatment, and a flame treatment that can be carried out continuously and can be easily carried out before the winding step of the film production process.

  The laminated film of the present invention can be made into a heat-sealable laminated film by selecting the polyolefin resin A and the polyolefin resin B. In particular, a heat-sealable laminated polypropylene-based resin film using a polypropylene-based resin is a two-layered / two-layered laminated film in which the first layer is a sealant layer and the second layer is a base material layer. It has sufficient heat seal strength, transparency and blocking performance, and grains, such as flour, rice, wheat, etc., and various pickles such as plate, thread konjac, takuan pickles, soy sauce pickles, Nara pickles, Suitable for packaging materials such as miso, soup stock, noodle soup, soy sauce, sauce, ketchup, mayonnaise, etc., and these are for paper cartons, tubes, bags, cups, standing packs, trays It can be used as a packaging body.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition, the evaluation method used by the Example and the comparative example, the resin used, and the manufacturing method of a laminated | multilayer film are as follows.

1. Evaluation method (1) Zero shear viscosity (η ₀ ): The above-described method was followed.
(2) Molecular weight distribution (Mw / Mn): The method described above was followed.
(3) Melt flow rate (MFR): Determined by measuring by a method based on JIS K7210 (230 ° C., 2.16 kg load).
(4) Appearance of film: Visual evaluation was performed on the transparency of the obtained film. The evaluation was carried out with x when the sense of transparency was poor and ◯ when the sense of transparency was excellent.
(5) Heat sealing start temperature: Two test films cut to a width of 15 mm are stacked so that the first layers are in contact with each other, and the sealing pressure is 1 kg / cm ² at 80 ° C. with a hot plate heat sealer manufactured by Toyo Seiki, sealing time Heat sealing was performed in 1 second, and a peel test of the heat seal portion was performed. Similarly, heat sealing was performed at intervals of 5 ° C., and the temperature at which the load required for peeling was first observed was defined as the heat sealing start temperature. The measurement was performed at a speed of 500 mm / min by opening a shopper type tensile tester.
(6) Blocking performance: A sample film of 2 cm (width) × 15 cm (length) is taken from the obtained resin film, and the first layers are stacked over a length of 5 cm (contact area 10 cm ² ), respectively, and 50 g / cm ² After conditioning for 7 days under an atmosphere of 40 ° C. under load, after removing each load and adjusting to a temperature of 23 ° C., the shopper type tensile tester is opened and the sample is peeled off at a rate of 500 mm / min. (Unit: g / cm ² ) was obtained. If this value is smaller than 30 g / cm ² , the blocking resistance is good.

2. Sample (1) PP1: Polypropylene resin (Novatech F203T manufactured by Nippon Polypro Co., Ltd .: MFR = 2.5 g / 10 min, melting peak temperature 158 ° C.)
(2) PP2: Polypropylene resin (Novatec SA03 manufactured by Nippon Polypro Co., Ltd .: MFR = 30 g / 10 min, melting peak temperature 164 ° C.)
(3) PP3: Polypropylene resin (Novatec SA06A manufactured by Nippon Polypro Co., Ltd .: MFR = 60 g / 10 min, melting peak temperature 160 ° C.)
(4) PP4: Polypropylene resin (Novatech MA8Q manufactured by Nippon Polypro Co., Ltd .: MFR = 0.85 g / 10 min, melting peak temperature 160 ° C.)
(5) PP5: polypropylene resin (propylene / ethylene random copolymer produced by metallocene catalyst) (Nippon Polypro Co., Ltd. Wintech WFX4T: MFR = 7.0 g / 10 min, melting peak temperature 125 ° C.)
(6) PP6: propylene resin (propylene / ethylene random copolymer produced by Ziegler-Natta catalyst) (Nippon Polypro Co., Ltd. Novatec F409ET: MFR = 9.0 g / 10 min, melting peak temperature 138 ° C.)
(7) PB1: Propylene / butene-1 random copolymer resin (Mitsui Chemicals, Inc. Toughmer XR110T: MFR = 6.5 g / 10 min, melting peak temperature 110 ° C.)
(8) F1: Inorganic fine particles (true spherical silica) (true spherical synthetic silica having an average particle size of 3.9 μm)

3. Manufacturing method of laminated film (1) Molding method of unstretched sheet Three types of resin compositions were connected to surface layer extruder-1, surface layer extruder-2, and intermediate layer extruder-3 at 240 ° C. It was melt-extruded from a three-layer T die and cooled and solidified with a cooling roll at 30 ° C. to obtain an unstretched sheet having a thickness of about 1 mm. Extruder-1 was charged with polyolefin resin A (first layer), and both extruder-2 and extruder-3 were charged with polyolefin resin B (second layer).
(2) Forming method of stretched film The unstretched sheet is stretched five times in the longitudinal direction at 105 ° C. in a tenter type sequential biaxial stretching apparatus, and then preheated to 160 ° C. in a tenter furnace, and then in the lateral direction at 158 ° C. The film was stretched at a stretching ratio of 9 times and subjected to heat setting at 158 ° C. while being relaxed by 5% to obtain a two-kind two-layer biaxially stretched polypropylene film having a total film thickness of 20 μm. A corona discharge treatment was applied to the second layer side of the obtained film so as to be 40 dyn / cm.

Example 1
For polyolefin resin A, 0.2 parts by weight of inorganic fine particles (F1) and 0.1 parts by weight of phenolic antioxidant (Ciba Geigy, Ir1010) are mixed with 100 parts by weight of polypropylene resin (PP5) using a Henschel mixer. Then, it was obtained by granulating with a 45 mm twin screw extruder. The polyolefin resin B was obtained by pellet blending a resin mixture consisting of 90 parts by weight of a polypropylene resin (PP1) and 10 parts by weight of a polypropylene resin (PP2), and then granulating with a 45 mm twin screw extruder. The polyolefin resin A was fed into the extruder-1 and the polyolefin resin B obtained by the above-described method was put into the extruder-2 and the extruder-3, and a two-kind two-layer laminated film was formed by the above method. W _B / W _A × η _0B / η _0A = 8.0 and 9 or less, and the evaluation result of the film appearance was ◯. Further, the heat seal starting temperature was 105 ° C. and the anti-blocking performance was 19 g / cm ² . The evaluation results of the obtained laminated film are shown in Table 1.

(Example 2)
In the preparation of the polyolefin resin B in Example 1, the blending ratio of the polypropylene resin (PP1) was changed from 90 parts by weight to 50 parts by weight, and the blending ratio of the polypropylene resin (PP2) was changed from 10 parts by weight to 50 parts by weight. Except for the above, a two-type two-layer laminated film was formed in the same manner as in Example 1. W _B / W _A × η _0B / η _0A = 2.0 and 9 or less, and the evaluation result of the film appearance was ◯. The heat seal starting temperature was 105 ° C., and the anti-blocking performance was 20 g / cm ² . The evaluation results of the obtained laminated film are shown in Table 1.

(Example 3)
For polyolefin resin A, 0.2 parts by weight of inorganic fine particles (F1) and 0.1 parts by weight of phenolic antioxidant (Ciba Geigy, Ir1010) are mixed with 100 parts by weight of polypropylene resin (PP5) using a Henschel mixer. Then, it was obtained by granulating with a 45 mm twin screw extruder. The polyolefin resin B was obtained by pellet blending a resin mixture consisting of 90 parts by weight of a polypropylene resin (PP1) and 10 parts by weight of a polypropylene resin (PP3), and then granulating with a 45 mm twin screw extruder. The polyolefin resin A was fed into the extruder-1 and the polyolefin resin B obtained by the above-described method was put into the extruder-2 and the extruder-3, and a two-kind two-layer laminated film was formed by the above method. W _B / W _A × η _0B / η _0A = 7.5 and 9 or less, and the evaluation result of the film appearance was ◯. The heat seal starting temperature was 105 ° C., and the anti-blocking performance was 18 g / cm ² . The evaluation results of the obtained laminated film are shown in Table 1.

Example 4
In the preparation of the polyolefin resin B of Example 3, the blending ratio of the polypropylene resin (PP1) was changed from 90 parts by weight to 75 parts by weight, and the blending ratio of the polypropylene resin (PP3) was changed from 10 parts by weight to 25 parts by weight. Was a two-type two-layer laminated film as in Example 3. W _B / W _A × η _0B / η _0A = 4.5 and 9 or less, and the evaluation result of the film appearance was ◯. The heat seal starting temperature was 105 ° C., and the anti-blocking performance was 18 g / cm ² . The evaluation results of the obtained laminated film are shown in Table 1.

(Example 5)
The polyolefin resin A contains inorganic fine particles (F1) 0 with respect to 100 parts by weight of a resin mixture composed of 70 parts by weight of a polypropylene resin (PP5) and 30 parts by weight of a propylene / butene-1 random copolymer resin (PB1). It was obtained by mixing 2 parts by weight and 0.1 parts by weight of a phenolic antioxidant (Ciba Geigy, Ir1010) with a Henschel mixer and then granulating with a 45 mm twin screw extruder. Polyolefin resin B was obtained by pellet blending a resin mixture consisting of 75 parts by weight of polypropylene resin (PP1) and 25 parts by weight of polypropylene resin (PP3) and then granulating with a 45 mm twin screw extruder. . The polyolefin resin A was fed into the extruder-1 and the polyolefin resin B was fed into the extruder-2 and the extruder-3, and a two-type two-layer laminated film was formed by the above-described method. W _B / W _A × η _0B / η _0A = 4.2 and 9 or less, and the evaluation result of the film appearance was ◯. Moreover, the heat seal start temperature was as good as 85 ° C. The anti-blocking performance was good at 23 g / cm ² . The evaluation results of the obtained laminated film are shown in Table 1.

(Comparative Example 1)
For polyolefin resin A, 0.2 parts by weight of inorganic fine particles (F1) and 0.1 parts by weight of phenolic antioxidant (Ciba Geigy, Ir1010) are mixed with 100 parts by weight of polypropylene resin (PP6) using a Henschel mixer. Then, it was obtained by granulating with a 45 mm twin screw extruder. The obtained polyolefin resin A was fed into Extruder-1 and polyolefin resin B as polypropylene resin (PP1) into Extruder-2 and Extruder-3. Molded. W _B / W _A × η _0B / η _0A = 8.2 and 9 or less, and the evaluation result of the film appearance was ◯. However, the heat seal initiation temperature is inferior and 120 ° C., also _{W A} is by wide and 3.7, anti-blocking performance was poor as 42 g / cm ^2. The evaluation results of the obtained laminated film are shown in Table 1.

(Comparative Example 2)
For polyolefin resin A, 0.2 parts by weight of inorganic fine particles (F1) and 0.1 parts by weight of phenolic antioxidant (Ciba Geigy, Ir1010) are mixed with 100 parts by weight of polypropylene resin (PP5) using a Henschel mixer. Then, it was obtained by granulating with a 45 mm twin screw extruder. The polyolefin resin B was 100 parts by weight of a polypropylene resin (PP1). The polyolefin resin A was fed into the extruder-1 and the polyolefin resin B was fed into the extruder-2 and the extruder-3, and a two-type two-layer laminated film was formed by the above-described method. Since W _B / W _A × η _0B / η _0A = 12.0, a scale pattern was generated and the film appearance was remarkably deteriorated, the evaluation result of the film appearance was x. The anti-blocking performance was 20 g / cm ² , but the heat seal starting temperature was slightly inferior at 115 ° C.

(Comparative Example 3)
A two-type two-layer laminated film was molded in the same manner as in Comparative Example 1 except that the polyolefin resin B of Comparative Example 2 was changed to 100 parts by weight of a polypropylene resin (PP4). Since W _B / W _A × η _0B / η _0A = 15.8, scaly patterns were generated and the film appearance was remarkably deteriorated, the evaluation result of the film appearance was x. The anti-blocking performance was 20 g / cm ² , but the heat seal starting temperature was slightly inferior at 115 ° C.

(Comparative Example 4)
In the preparation of the polyolefin resin B of Example 1, the blending ratio of the polypropylene resin (PP1) was changed from 90 parts by weight to 95 parts by weight, and the blending ratio of the polypropylene resin (PP2) was changed from 10 parts by weight to 5 parts by weight. Was a two-type two-layer laminated film as in Example 2. Since W _B / W _A × η _0B / η _0A = 9.1, a scale pattern was generated and the film appearance was remarkably deteriorated, the evaluation result of the film appearance was x. The anti-blocking performance was 19 g / cm ² , but the heat seal starting temperature was slightly inferior at 110 ° C.

(Comparative Example 5)
A two-type two-layer laminated film was molded in the same manner as in Comparative Example 3, except that the polyolefin resin B in Comparative Example 3 was changed to 100 parts by weight of the polypropylene resin (PP3). Since W _B / W _A × η _0B / η _0A = 0.2 and film breakage occurred during transverse stretching, a film could not be obtained.

  Since the laminated film of the present invention is a laminated film that does not cause poor appearance such as a scale pattern due to instability of the interface between layers, has excellent transparency, anti-blocking performance of the film, and excellent heat seal characteristics, various foods These can be used as packaging materials for paper cartons, tubes, bags, cups, standing packs, trays, and the like.

It is a figure explaining the baseline and the section of a chromatogram in the measurement of the polymer molecular weight by GPC.

Claims (7)

A first layer at least a molecular weight distribution W _A consists of 3.5 or less of the polyolefin resin A, in contact with the first layer has a structure obtained by stacking a second layer consisting of polyolefin resin B, and, eta _{0B /} eta _A fluidity parameter represented by _0A × W _B / W _A satisfies the following formula (1).

(In the formula _{(1), η 0A, η} 0B each represents a polyolefin resin A, the zero shear viscosity of the polyolefin resin _B, W A, _{W B} are each the polyolefin resin A, the molecular weight distribution of the polyolefin resin B ( Mw / Mn).)   The laminated film according to claim 1, wherein the polyolefin resin A and the polyolefin resin B are polypropylene resins.   Polyolefin resin B includes polypropylene (b1) having a melt flow rate (MFR) of 0.01 g / 10 min to 4 g / 10 min and polypropylene (b2) having an MFR of 20 g / 10 min to 100 g / 10 min. The laminated film according to claim 1, which is a polypropylene resin composition.   The laminated film according to claim 1, wherein the polyolefin-based resin A contains a propylene / α-olefin random copolymer as a main component.   The laminated film according to claim 4, wherein the propylene / α-olefin random copolymer is a polymer produced by a metallocene catalyst.   The laminated film according to any one of claims 1 to 5, wherein the laminated film is obtained by a co-pressing method.   The laminated film according to claim 1, wherein the laminated film is stretched at least in a uniaxial direction.

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