TW201538324A - Polyolefin-based unstretched multilayer film - Google Patents

Abstract

The present invention provides a polyolefin-based unstretched multilayer film, which has excellent optical characteristics, blocking resistance, heat sealing properties, hermetic sealing properties, package openability by tearing and easy peeling properties. This polyolefin-based unstretched multilayer film comprises a laminate layer, at least one intermediate layer, and a heat sealing layer. At least one intermediate layer is formed of a polyolefin-based resin containing a long-chain branched LLDPE. The long-chain branched LLDPE in the polyolefin-based resin of the intermediate layer has a ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) in terms of polystyrene as determined by gel permeation chromatography, namely Mw/Mn of 7.5-15.0 and an amorphous content of 1-4% by weight as determined by a temperature raising elution fractionation method. The long-chain branched LLDPE in the polyolefin-based resin of the intermediate layer has 1.5-5.0 branches, each of which has 8 or more carbon atoms, per 1,000 carbon atoms as determined by 13C-NMR.

Description

Polyolefin-free extended multilayer film

The present invention relates to a polyolefin-based non-stretch multilayer film. More specifically, it is related to optical characteristics such as excellent high transparency, high gloss, high reproducibility, resistance to retardation, low-temperature heat-sealing property, and the like, and the base film is laminated as a composite film. A polyolefin-based non-stretched multilayer film having excellent heat-sealing strength; sealing property; tear-opening property of the package to easy tearability.

Polyolefin-based resin films are widely used for packaging materials of various products. For example, food packaging applications; packaging purposes for daily groceries such as fibers and clothing; packaging applications for industrial components. In particular, since the polypropylene resin film has excellent rigidity and heat resistance and has a high supporting force of the film, it is widely used because it can improve the accuracy with respect to the bag making machine. However, the polypropylene resin film has at least heat sealability, particularly low temperature heat sealability, and insufficient impact resistance. Therefore, attempts have been made to improve heat sealability and impact resistance by copolymerizing polypropylene of a film material. However, in particular, it is not possible to replace the impact resistance at a significant low temperature. Moreover, in order to improve the heat sealability, a block problem occurs. Therefore, the above copolymerization proposal has not been successful.

Japanese Laid-Open Patent Publication No. Hei 5-147179 proposes that the intermediate layer is a linear ethylene-α-olefin copolymer (LLDPE) obtained by laminating the intermediate layer and a polypropylene resin layer for both outer layers. A polyolefin-based multilayer film that improves impact resistance. Although it was confirmed by this method that the impact resistance was improved, the optical properties (transparency, gloss, reproducibility, etc.) of the laminated film were impaired. Further, when the laminated film-attached base film is used as a composite film, the tear strength is extremely high, so that the tear-opening property when used as a packaging material is remarkably impaired.

JP-A-2004-276373 proposes a polyolefin-based multilayer film in which a specific polypropylene-based polymer is used as a two-layer outer layer to laminate an LLDPE layer of an intermediate layer to improve low-temperature heat-sealing property and retardation resistance. . Further, by this technique, the tear strength of the obtained composite film is extremely high, so that the tear-opening property required for use as a packaging material cannot be satisfied.

Further, for packaging for food packaging, for example, snacks, etc., in addition to the above-described tear opening, it is also required to be peeled off from the heat seal portion and opened. In other words, the vicinity of the heat seal portion of the film constituting the bag body is grasped by the hand, and is torn in a direction perpendicular to the film surface with respect to the film surface, and the heat seal portion is peeled off to be unsealed. The easy peelability of the heat seal portion is referred to as "easy opening property".

Even if it has a tear-opening packaging material, it is required to maintain the sealing property when it is used for food use or the like. However, in the prior art, it has hardly been reviewed how to improve the tearability of the packaging material while improving the tearability of the packaging material.

Summary of invention

The present invention is an invention based on the current state of the art.

An object of the present invention is to provide properties such as excellent optical properties, retardation resistance, low-temperature heat-sealing property, heat-sealing strength, sealing property, etc., and having excellent tear-opening property and tearability of a package. A polyolefin-based non-stretch multilayer film.

The above objects and advantages of the present invention can be attained by a polyolefin-based non-extended multilayer film having a laminate layer of the outermost layer, an intermediate layer of at least one layer, and a heat seal layer of the other outermost layer. The press layer is formed of a polyolefin resin, and at least one of the intermediate layers is formed of a polyolefin resin containing a long-chain branched LLDPE, and the heat seal layer is formed of a polyolefin resin containing a polypropylene resin. The polyolefin-based resin of the laminate layer has a melting point higher than that of the polypropylene-based resin of the heat-sealing layer, and the long-chain branched LLDPE in the polyolefin-based resin of the intermediate layer is by gel permeation chromatography. The ratio Mw/Mn of the measured polystyrene-equivalent weight average molecular weight Mw to the number average molecular weight Mn was 7.5 to 15.0.

The amount of the amorphous component measured by the temperature rising elution fractionation method is 1 to 4% by weight, and the number of branches having 8 or more carbon atoms measured by ¹³ C-NMR is 1.5 to 5.0 per 1,000 carbon atoms. . The multilayer film is achieved.

Form of implementing the invention

The polyolefin-based non-stretched multilayer film of the present invention is a heat-sealing layer having a laminate layer of the outermost layer, an intermediate layer of at least one layer, and another outermost layer.

<Laminated layer>

The laminate layer in the multilayer film of the present invention is formed of a polyolefin resin.

The polyolefin-based resin has a melting point higher than that of the polypropylene-based resin in the heat-sealing layer described later. The melting point of the polyolefin resin is preferably 3 ° C or more higher than the melting point of the polypropylene resin in the heat seal layer, more preferably 5 ° C or higher, and particularly preferably 15 ° C higher. By manufacturing or laminating the multilayer film of the present invention, it is possible to obtain sufficient heat resistance at the time of heat sealing. Further, the difference between the melting point of the polyolefin resin and the polypropylene resin in the heat seal layer is preferably 20 ° C or lower. When the difference in melting point is too large, the multilayer film may be curled.

The polyolefin-based resin constituting the laminate layer in the present invention is, for example, a polypropylene-based resin, a single polymer of ethylene, an ethylene-α-olefin copolymer, a thermoplastic elastomer or the like. These may be used alone or in combination of two or more. The melting point of the polyolefin-based resin is preferably in the range of 120 to 165 ° C, and the melt flow rate MFR is preferably in the range of 1 to 30 g/10 minutes. The melting point is the peak top temperature (Tm) of the maximum endothermic peak in the differential scanning calorimeter (DSC) chart; the MFR is a value measured in accordance with JIS K 7210 (the melting point and MFR of the present specification are the same below).

The above polypropylene-based resin, such as propylene alone polymer, propylene and a copolymer of polymeric components. The copolymerization component is preferably, for example, ethylene and an α-olefin, and specifically, for example, ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1- Terpene, 4-methyl-1-pentene or the like may be used, and one or more of them may be used. The ratio of the copolymerization component in the polypropylene resin is preferably 10 mol% or less, more preferably 5 mol% or less, and particularly preferably 3 mol% or less.

The above ethylene-α-olefin copolymer does not contain a corresponding one of the above polypropylene-based resins. The α-olefin of the copolymerization component in the above ethylene-α-olefin copolymer, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1 - Terpene, 4-methyl-1-pentene, which may be selected one or more. The proportion of the α-olefin component in the ethylene-α-olefin copolymer is preferably from 1 to 20 mol%, more preferably from 5 to 15 mol%.

The polyolefin-based resin in the laminate layer of the multilayer film of the present invention preferably contains the above-mentioned polypropylene-based resin. The laminate layer may be formed only of a polypropylene resin, and may also contain a polypropylene resin and other polymers. The other polymers used at this time are preferably selected from the above-mentioned individual polymers of ethylene, ethylene-α-olefin copolymers, and thermoplastic elastomers.

The content ratio of the other polymer is preferably 10% by weight or less, more preferably 5% by weight or less based on the entire polyolefin resin, and most preferably no other polymer.

[arbitrary ingredients]

The laminate layer of the multilayer film of the present invention may contain any additives other than the above-mentioned polyolefin-based resin, such as a heat stabilizer, a processing stabilizer, A lubricant, a nucleating agent, an antistatic agent, an antifogging agent, an anti-sticking agent, an antioxidant, an ultraviolet absorber, a pigment, and the like. These additives may be added by directly adding a polymer constituting the polyolefin resin, or by adding the additives at a high concentration as a masterbatch for addition. As the base resin of the master batch, any of the above polyolefin-based resins can be used.

The use ratio of the above-mentioned optional component is preferably 10% by weight or less, and more preferably 5% by weight or less based on the entire polyolefin resin. The best is to not contain any of the ingredients of this class.

[Thickness of laminated layer]

The thickness of the laminate layer in the multilayer film of the present invention is preferably from 1.0 to 30 μm, more preferably from 2.5 to 25 μm. By setting the laminate layer to a thickness within the range, it is preferred that the obtained multilayer film and composite film have high impact resistance without loss of heat resistance and opening property.

<intermediate layer>

At least one layer of the intermediate layer in the multilayer film of the present invention is formed of a polyolefin-based resin containing long-chain branched LLDPE (B1).

[long chain branch LLDPE]

The long-chain branched LLDPE (B1) of the present invention is a linear low-density polyethylene having a branch having 8 or more carbon atoms.

The LLDPE used in prior art films has the concept of branched low density polyethylene, and is associated with the long chain branch LLDPE (B1) of the present invention. Common to LDPE (low density polyethylene). However, the long chain branch LLDPE (B1) of the present invention differs from the prior art LLDPE and LDPE in at least the content of the long chain branch, the Mw/Mn and the amount of the amorphous component.

In the long-chain branched LLDPE (B1) of the present invention, the number of branches having 8 or more carbon atoms measured by ¹³ C-NMR is 1.5 to 5.0 per 1,000 carbon atoms. The value is preferably from 2.0 to 5.0, more preferably from 2.5 to 4.5. By using such a long-chain branched LLDPE, when the multilayer film of the present invention is used as a package, the advantages of tear-opening property and easy tearing property can be obtained.

From this point of view, the carbon number of the branched chain in the prior art LLDPE is mainly 6 or less, and even if there are branches having 8 or more carbon atoms, the amount thereof is small, and generally 1 or less per 1,000 carbon atoms, and at most 2 or less. .

Further, in the ¹³ C-NMR measurement of LDPE, the component of the branch having a carbon number of 8 or more was found to be more than 5 per 1,000 carbon atoms.

Therefore, the long-chain branched LLDPE (B1) of the present invention can be distinguished from the prior art LLDPE and LDPE by a branch amount of carbon number 8 or more as determined by ¹³ C-NMR.

The results of ¹³ C-NMR measurement of the branched structure of the long-chain branched LLDPE (B1) of the present invention and the branched structure of the prior art LLDPE will be described below. Wherein the branch line focus on the long chain branching of C ₈ branched LLDPE (1-decene structure) and of prior art LLDPE branched C ₆ (1-octene structure).

The methyl group carbon present in the main chain of the polyethylene can be observed at ¹³ C-NMR chemical shift δ = 30 ppm. Further, the methyl carbon at the end of the branch appeared at both the C ₈ branch and the C ₆ branch at a chemical shift of δ = 14.06 ppm. However, the chemical shifts of the second and third methyl carbons from the end of the branch are shown in Table 1, and the C ₈ branch is different from the C ₆ branch.

In the present invention, when the second methyl group is branched from the end of the branch, it is possible to determine whether or not the carbon number is 8 or more by the chemical shift.

The actual calculation is to evaluate the relative value of the peak area appearing at the chemical shift δ=22.87 ppm, and the peak area appearing with respect to the chemical shift δ=30 ppm of the methyl carbon derived from the main chain.

The measurement of the above ¹³ C-NMR can be carried out under the following conditions using an appropriate nuclear magnetic resonance analysis apparatus such as "JNM-ECS400" manufactured by Nippon Denshi Co., Ltd., for example.

Solvent: mixed solvent of trichlorobenzene/heavy benzene (75/25% by volume)

Sample concentration: 80mg/2.5mL solution

Measurement mode: 1H-complete decoupling

Measuring temperature: 120 ° C

Pulse amplitude: 90 degree pulse

Pulse repetition time: 9 seconds

The total number of calculations: 9,000 times

The content of the long-chain branch of the present invention is such that when the peak area of the methyl carbon (chemical shift δ = 30 ppm) constituting the polymer chain is 1,000, the second carbon (chemical shift δ) from the end of the C ₈ branch The relative value of the peak area of =22.87 ppm) is expressed. The unit is (pieces / 1,000C).

The long-chain branched LLDPE (B1) of the present invention has a ratio Mw/Mn (molecular weight distribution) of a weight average molecular weight Mw to a number average molecular weight Mn measured by gel permeation chromatography (GPC) of 7.5~. 15.0. The value is preferably from 8.5 to 14.5, more preferably from 9.5 to 13.5. By using the long-chain branched LLDPE having such a molecular weight distribution, when the multilayer film of the present invention is used as a package, the advantages of tear-opening property and easy tearing property can be obtained.

The long-chain branched LLDPE (B1) of the present invention preferably has a polystyrene-equivalent weight average molecular weight Mw measured by GPC of from 80,000 to 150,000, more preferably from 90,000 to 140,000.

The amount of the amorphous component measured by the temperature-rise elution fractionation method of the long-chain branched LLDPE (B1) of the present invention is 1 to 4% by weight.

The temperature-rise elution fractionation method is to supply a solution obtained by dissolving a polymer sample in a certain solvent at a high temperature to a TREF (Temperature Rising Elution Fractionation) column, and secondarily cooling to precipitate the column, adsorbing the polymer sample, and then the column The method of slowly raising the temperature and then analyzing the dissolved fraction. In the present invention, after the column to which the sample is supplied is cooled to 0° C., the supply of the solvent is started, and the fraction eluted during the period in which the column temperature is maintained at 0° C. is used as the amorphous component, and the ratio of the fraction to the total fraction is used as the ratio of the fraction to the total fraction. The amount of the amorphous component was evaluated. The amount of the amorphous component of the long-chain branched LLDPE is preferably from 1.5 to 3.0% by weight.

Such a temperature-increasing elution fractionation method can be carried out by, for example, a suitable temperature-rise elution (TREF) apparatus such as a TREF apparatus type manufactured by Sec.

By using the long-chain branched LLDPE having crystallinity as described above, the multilayer film of the present invention can be obtained with the advantages of ensuring retardation resistance and supporting force (elasticity).

The various parameters described above for the polyethylene of a representative commercial product are shown in reference to Table 2 below.

The long-chain branched LLDPE (B1) of the present invention as described above is defined as an article conforming to the above requirements, which can be synthesized by any method. For example, by using a known Ziegler-Natta catalyst, it is preferred to use a suitable donor compound. Method; using Phillips catalyst method; using a metallocene catalyst method or the like. Among them, a method using a metallocene catalyst is preferred to obtain a polymer having the above characteristics.

The metallocene catalyst is a catalyst formed by a metallocene-type transition metal compound having at least one, preferably two substituted or unsubstituted cyclopentadienyl ligands, and a promoter. The above-mentioned promoter may be one or more selected from the group consisting of an organoaluminum compound, an organoboron compound and a cation complex, an ion-exchangeable citrate or the like. The metallocene catalyst can be attached to a suitable inorganic substance. The metallocene catalyst can be selected from suitable metallocene catalysts known to the industry for its purpose.

[Other polymers]

The at least one layer of the intermediate layer in the multilayer film of the present invention may contain other polymers in addition to the long-chain branched LLDPE (B1) as described above.

Other polymers which can be used at this time are, for example, a polypropylene resin (B2), a polyethylene (B3) other than the long-chain branched LLDPE (B1), a thermoplastic elastomer or the like.

The polypropylene resin (B2) can be used, for example, the same resin as the above-described resin in the polypropylene resin for the polyolefin resin constituting the laminate layer.

Polyethylene (B3) other than the long-chain branched LLDPE (B1), such as HDPE, LLDPE, LDPE, and the like.

The intermediate layer in the multilayer film of the present invention may be contained by the other a resin selected from the group consisting of a polypropylene resin (B2) in a polymer and a polyethylene (B3) other than a long-chain branched LLDPE (B1), which is easy to tear when the multilayer film is used as a package. It is better to open the strength.

In view of the above, the at least one layer of the polyolefin-based resin of the intermediate layer in the multilayer film of the present invention is preferably formed only of long-chain branched LLDPE (B1) or long-chain branched LLDPE (B1), and It is generally formed of a resin selected from the group consisting of a polypropylene resin (B2) and a polyethylene (B3) other than the long-chain branched LLDPE (B1).

The at least one layer of the intermediate layer of the multilayer film of the present invention is formed of only a polypropylene resin as described above, and is preferably free of other resins.

It is preferable that the at least one layer of the polyolefin-based resin of the intermediate layer of the multilayer film of the present invention contains the above-mentioned resin in the following ratio.

Long-chain branched LLDPE (B1): preferably 40% by weight or more, more preferably 50% by weight or more

Polypropylene resin (B2): preferably 30% by weight or less, more preferably 25% by weight or less, and polyethylene (B3) other than long-chain branched LLDPE (B1): preferably 50% by weight or less, more preferably 30% by weight or less

The total amount of the polyethylene (B3) other than the long-chain branched LLDPE (B1), the polypropylene-based resin (B2), and the long-chain branched LLDPE (B1) was 100% by weight.

[arbitrary ingredients]

The intermediate layer of the multilayer film of the present invention may contain any of the additives described as the optional component of the laminate layer in the same manner.

[The middle layer aspect]

The intermediate layer of the multilayer film of the present invention may be formed of a single layer or a layer of two or more layers. The layers constituting the intermediate layer in the latter are selected from the above polyolefin-based resins. The polyolefin-based resin constituting each layer may be of a different type of polyolefin-based resin, and other polymers and additives having any optional components may be the same as the type and content ratio, or one or more of them may be different.

The thickness of the intermediate layer is preferably from 5 to 80 μm, more preferably from 10 to 50 μm. By setting the intermediate layer to this range, it is possible to obtain a high impact resistance and excellent reproducibility of the obtained multilayer film and composite film without impairing the rigidity for the multilayer film.

When the intermediate layer is formed of a laminate of a polyolefin resin, the number of laminations is preferably two to four layers, more preferably two to three layers. The polyolefin-based resins of the respective layers may be the same or different. The thickness of the laminate is preferably such that the thickness of the intermediate layer is within the above range. The thickness of each layer constituting the laminate is preferably 2 to 40 μm, more preferably 5 to 25 μm.

<heat seal layer>

The heat seal layer of the multilayer film of the present invention is formed of a polyolefin resin containing a polypropylene resin.

The polypropylene resin is preferably a polypropylene resin containing 70% by weight or more of the propylene-ethylene copolymer (C). The polymer in the polypropylene resin of the heat seal layer may be formed only of the above propylene-ethylene copolymer (C) or both the propylene-ethylene copolymer (C) and other polymers.

When the propylene-ethylene copolymer (C) is added to the polypropylene resin of the heat seal layer, the retardation resistance, low-temperature heat sealability, heat seal strength, and heat seal of the obtained multilayer film and composite film can be imparted. The pinhole resistance of the part. When the proportion of the propylene-ethylene copolymer (C) in the polypropylene resin of the heat seal layer is less than 70% by weight, it is found that the above effects are insufficient. The proportion of the propylene-ethylene copolymer (C) in the polypropylene resin of the heat seal layer is preferably 80% by weight or more, and more preferably 90% by weight or more.

In the propylene-ethylene copolymer (C), the molecular weight distribution Mw/Mn expressed by the ratio of the weight average molecular weight Mw to the number average molecular weight Mn is preferably from 1.5 to 3.5, more preferably from 1.8 to 3.2, still more preferably from 2.0 to 2. 3.0. When the Mw/Mn of the propylene-ethylene copolymer (C) is less than 1.5, the melt tension is too small, and the film formability is deteriorated. Further, from the viewpoint of ensuring the retardation resistance of the multilayer film and ensuring the optical characteristics of the multilayer film and the composite film, Mw/Mn is preferably 3.5 or less. The Mw of the above propylene-ethylene copolymer (C) is preferably from 450,000 to 100,000, more preferably from 400,000 to 200,000.

The propylene-ethylene copolymer (C) preferably has a melt flow rate MFR of from 1 to 30 g/10 min, more preferably from 5 to 15 g/10 min, measured in accordance with JIS K 7210 at 230 ° C under a load of 2.16 kg. When the MFR is less than 1 g/10 minutes, the melt viscosity is too high, and the pressure in the film forming machine (for example, an extruder) when the multilayer film is manufactured is excessively increased, so that in addition to reducing productivity, The appearance of the film thickness unevenness, melt fracture, and the like is poor. On the other hand, when the MFR exceeds 30 g/10 minutes, the difference in the melt viscosity of the resin with the intermediate layer is too large, and the film thickness of the outer layer is uneven, and the retardation resistance when used as a multilayer film is impaired.

The melting point of the above propylene-ethylene copolymer (C) is preferably from 120 to 140 ° C, more preferably from 120 to 135 ° C. The propylene-ethylene copolymer (C) having a melting point in this temperature range can be excellent, and the heat resistance at the time of producing a multilayer film is preferably balanced with the transparency for a multilayer film or a composite film.

The content ratio of the ethylene unit in the propylene-ethylene copolymer (C) is preferably from 1 to 10 mol%, more preferably from 2 to 5 mol%. By setting the content ratio of the ethylene unit to the range, the obtained multilayer film can be preferably found to have excellent retardation resistance without loss of transparency.

The propylene-ethylene copolymer (C) is preferably a polymer obtained by polymerization using a metallocene catalyst, and the propylene-ethylene copolymer (C) obtained by polymerization using a metallocene catalyst is used to obtain a multilayer obtained. The film has high resistance to retardation and is excellent as an optical property when used as a multilayer film or a composite film.

The metallocene catalyst is a catalyst formed from a metallocene-type transition metal compound having at least one, preferably two substituted or unsubstituted cyclopentadienyl ligands, and a promoter. The above-mentioned promoter may be one or more selected from the group consisting of an organoaluminum compound; an organoboron compound and a cation complex; an ion-exchangeable citrate. The metallocene catalyst can be attached to a suitable inorganic material. The metallocene catalyst can be used by the manufacturer It is known to be selected for use in a suitable metallocene catalyst.

[Other polymers]

The above other polymer is not particularly limited and used without affecting the effects of the present invention. However, in consideration of the tear-opening property of the packaging material which is one of the main features of the present invention, it is preferred to use a polypropylene-based resin (A1) other than the above-mentioned propylene-ethylene copolymer (C). The molecular weight distribution Mw/Mn expressed by the ratio of the weight average molecular weight Mw to the number average molecular weight Mn in the polypropylene resin (A1) is preferably 4 or more, more preferably 4.5 to 10, still more preferably 5 to 8. When the Mw/Mn of the polypropylene-based resin (A1) is less than 4, the tear strength of the obtained multilayer film and the composite film produced using the same is too high, and it is difficult to find an effect of improving the tear-opening property of the packaging material. It is presumed that when Mw/Mn is less than 4, melt alignment tends to occur when a multilayer film is produced. Further, in order to obtain a melt tension in an appropriate range when producing a multilayer film, it is preferable that Mw/Mn is 10 or less from the viewpoint of resistance to retardation when used as a multilayer film. The Mw of the polypropylene resin (A1) is preferably from 450,000 to 100,000, more preferably from 400,000 to 200,000.

The weight average molecular weight Mw and the number average molecular weight Mn are values in terms of polystyrene measured by gel permeation chromatography (GPC).

The polypropylene resin (A1) preferably has a melt flow rate MFR of from 1 to 30 g/10 min, more preferably from 5 to 15 g/10 min, measured in accordance with JIS K 7210 at 230 ° C under a load of 2.16 kg. When the MFR is less than 1 g/10 minutes, the melt viscosity is too high, and the pressure in the film forming machine (for example, an extruder) when the multilayer film is produced is excessively increased, thereby lowering productivity and causing film. The appearance of uneven thickness, melt fracture, etc. is poor. On the other hand, when the MFR exceeds 30 g/10 minutes, the difference in the melt viscosity of the resin with the intermediate layer is too large, and the thickness of the outer layer is uneven, and the retardation resistance when used as a multilayer film is impaired.

The melting point of the polypropylene resin (A1) is preferably from 120 to 150 ° C, more preferably from 130 to 145 ° C. The polypropylene resin (A1) having a melting point in this temperature range can be excellent, and the heat resistance at the time of producing a multilayer film is preferably balanced with the transparency when used as a multilayer film or a composite film. The melting point of the resin at this time means the peak top temperature (Tm) of the maximum endothermic peak in the differential scanning calorimeter (DSC) chart.

The above polypropylene-based resin (A1) may be a single polymer of propylene or a copolymer of propylene and a copolymerization component. The copolymerization component used at this time is preferably ethylene and an α-olefin, and specifically, for example, ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-anthracene As the olefin, 1-decene, 4-methyl-1-pentene or the like, one or more selected from them can be used. The proportion of the copolymerization component in the polypropylene resin (A1) is preferably 10 mol% or less, more preferably 5 mol% or less, still more preferably 3 mol% or less.

The heat seal layer is preferably formed only of the above propylene-ethylene copolymer (C) or only of the propylene-ethylene copolymer (C) and the polypropylene resin (A1).

[arbitrary ingredients]

The heat seal layer of the multilayer film of the present invention may contain the additive described as an optional component of the laminate layer in the same manner.

[Thickness of heat seal layer]

The thickness of the heat seal layer in the multilayer film of the present invention is preferably from 2 to 30 μm, more preferably from 2.5 to 25 μm. When the thickness of the heat seal layer is set to this range, the obtained multilayer film and composite film can be preferably subjected to high impact resistance without damaging low temperature heat sealability and pinhole resistance.

<Thickness of polyolefin-based non-extended multilayer film>

The thickness of the polyolefin-based non-stretched multilayer film of the present invention can be appropriately set depending on the use form and use. The multilayer film of the present invention is used as the packaging material, or is bonded to the film substrate as a composite film, and the use can be the type and weight of the contents of the packaging material.

The polyolefin-based non-stretched multilayer film of the present invention has a thickness of, for example, 10 to 200 μm, preferably 15 to 150 μm, more preferably 18 to 100 μm.

<Method for Producing Polyolefin-Based Non-Extended Multilayer Film>

The multilayer film of the present invention can be produced by any method which is substantially free of elongation. "Substantially without extension" means that any alignment occurs during the non-prohibition of the manufacture of the film without the extended steps explicitly indicated by the present invention. It can therefore be explained that, for example, it is possible to allow several alignments to occur when used in extrusion steps under generally employed conditions.

The method for producing a multilayer film of the present invention may be, for example, an appropriate method such as extrusion or casting. The resin constituting each layer of the multilayer film of the present invention has a moderate MFR, and is relatively suitable for a melt type film forming machine. In the case of the above-mentioned extrusion method, it is preferable to obtain the maximum effect of the present invention. The die of the extrusion method can use a T die, a ring die, or the like. However, from the viewpoint of obtaining excellent optical characteristics by precisely controlling the thickness of the layer, it is not preferable to use a ring die, and it is preferable to use a T die or the like.

The multilayer film of the present invention is a multilayer structure having at least three layers of a laminate layer, at least one intermediate layer, and a heat seal layer. The method of multilayering a film can employ a known method such as a co-extrusion method, an in-line lamination method, or the like. The above coextrusion method is, for example, a multi-tube method, a feed block method, or the like. In the case of the co-extrusion method, it is preferred to uniformly control the thickness of each layer in the width direction.

It is expected that the multilayer film of the present invention can be used as a packaging material in the form of a composite film which is directly or bonded to a film substrate. Therefore, in order to express the product on the outermost surface or to find the effect of the product, the former can be printed, and the latter is attached to the outermost surface, and the film substrate is generally attached to the surface of the laminate. In this case, in order to improve the affinity or adhesion to the ink or the adhesive, the surface treatment may be carried out on the outermost surface, generally on the surface of the laminate layer, in an on-line or stand-alone manner. The surface treatment such as corona discharge treatment, combustion or flame treatment, and the like.

<Composite film>

The composite film of the present invention is obtained by attaching the above-mentioned multilayer film to the film substrate with the laminate layer side of the multilayer film as the attachment surface. The composite film of the present invention can have good low-temperature heat-sealing properties, heat-sealing strength, and pinhole resistance of the heat-sealed portion, and has excellent tear-opening properties when used as a packaging material.

[Film substrate]

The material constituting the film substrate in the composite film of the present invention can be appropriately determined depending on the use of the packaging material. For example, a resin selected from a group consisting of a polypropylene resin, a polyethylene resin, a polyethylene terephthalate resin, and a polyamide resin, or a metal. The film substrate may be a layer containing one or more selected from the materials, or a laminate formed by a plurality of layers.

The thickness of the film substrate may be arbitrary depending on the use of the packaging material, and may be, for example, 5 to 75 μm, preferably 10 to 50 μm.

[Thickness of composite film]

The total thickness of the composite film of the present invention can be arbitrarily set depending on the use of the packaging material, and can be, for example, 15 to 250 μm, preferably 20 to 200 μm, more preferably 23 to 150 μm.

<Method of Manufacturing Composite Film>

The method for producing a composite film may be a method in which the multilayer film of the present invention is attached to the film substrate so that the side of the laminate layer is a side surface, and is not particularly limited.

The bonding between the film substrate and the laminate of the multilayer film may be by a suitable adhesive or by thermal compression bonding. The adhesive used at this time may be a commercially available adhesive or a molten resin such as a polyethylene resin. The coating method of the subsequent agent is, for example, a gravure method of a gravure, a gravure, a lithographic plate, etc.; a planing method of a rod, a sectional bar, or the like.

If necessary, a method of laminating a film substrate and a multilayer film with an adhesive layer may be interposed, such as a dry lamination method, a thermal lamination method, or the like.

Example

Hereinafter, the present invention will be described by way of examples and comparative examples, but the present invention is not limited to the examples.

Each of the evaluation methods of the following examples and comparative examples was each subjected to the following steps.

<Evaluation of Multilayer Films> (1) turbidity

A turbidity meter (Model: NDH5000) manufactured by Nippon Denshoku Industries Co., Ltd. was used, and turbidity was measured as an index of transparency in accordance with JIS K 7136.

(2) gloss

A gloss meter (model: UGV-5D) made by a Sijia test machine (model) was used, and gloss was measured as an indicator of gloss according to JIS K 7105. The gloss was evaluated by performing on both sides of the surface of the laminate layer side of the multilayer film and the surface of the heat seal layer side.

(3) like vividness

Reproducibility tester using the Sijia test machine (model: ICM- 1DP), according to JIS K 7105, the image width of the optical comb was measured to be 0.125 mm.

(4) Blocking strength

The retardation strength was investigated as an index of resistance to block by the following tensile tester.

By laminating 10 layers of a 120 mm × 120 mm square multilayer film by laminating the heat seal layer between the films, the film was stored at a temperature of 40 ° C and a humidity of 70% in a state of a top load of 10 kg. RH constant temperature and humidity machine for 3 days (ie 72 hours). After the storage of the multilayer film, two of the upper layer and the lower layer of the two samples were removed, and then two of the adjacent layers were peeled off to obtain three groups. In each of the two layers, the multilayer film was laminated under the above conditions in such a manner that the laminate layer was bonded to the heat seal layer. A rectangular shape of 30 mm × 120 mm was cut out from each group, and three test pieces were removed. The test piece was peeled off on the shorter side, and the length of the pressed portion was 40 mm, and the pressed portion 30 mm × 40 mm remaining in each test piece was used as the measurement region of the resistance.

Next, an automatic crucible manufactured by Shimadzu Corporation (model: AG-500D) was used, and each of the two holders was placed on the layer of the peeled portion of the test piece to measure the temperature at 23 ° C and the tensile strength of 50 mm / min. The tensile test was carried out under the conditions, and the maximum value of the stress which can completely peel off the test piece was investigated. The average value (kPa) of the maximum value when n is 3 is taken as the retardation strength.

(5) Impact strength

The impact strength was measured as an index of impact resistance under the following conditions using a film impact tester manufactured by Toyo Seiki Co., Ltd.

Test piece size: 120mm × 120mm

Measuring temperature: 23 ° C environment and 0 ° C environment

(6) Tear strength (the splitting method: Trauzer Tear Method)

An automatic crucible manufactured by Shimadzu Corporation (model: AG-500D) was used in accordance with JIS K 7128-1, and tear strength was measured as an index of tear resistance under the following conditions.

Test piece size: long side (length) 100mm, short side (width) 50mm

Gap: at the center of one short side of the test piece (25 mm from the long side), cut a 20 mm long slit parallel to the long side

Stretching speed: 500mm/min

Measuring temperature: 23 ° C environment

<Evaluation of composite film> (7) Heat seal strength

After bonding the heat seal layers of the two composite films, they were used as indicators for heat sealability at the respective temperatures by the following tensile test.

Two composite films of 15 mm × 200 mm rectangular shape were cut out, and the heat-sealing layers were superposed on each other in two pieces. Then, the YSS heat sealer manufactured by Yasuda Seiki Seisakusho Co., Ltd. was heat-sealed under the following conditions. Test piece.

Heat sealing rod width: 5mm

Heat sealing pressure: 0.1MPa

Heat sealing time: 1.0 seconds

Heat sealing temperature: 150 ° C, 160 ° C and 170 ° C

The fields of 5 mm × 15 mm of the heat seal portion of the test piece obtained above were each used as a measurement field of heat seal strength. In this case, the long side of the rectangle coincides with the extrusion direction of the film, and the test piece for the "long" direction is used, and the long side of the rectangle is orthogonal to the extrusion direction of the film, and the test piece is used as the "wide" direction. A test piece of 2 directions × 3 temperature = 6 kinds of each of the composite films was produced.

An automatic crucible manufactured by Shimadzu Corporation (model: AG-500D) was used, and the heat-sealed portion of the test piece was peeled off at each temperature and then clamped with two holders at a tensile strength of 300 mm/min. The tensile test was carried out under the conditions to investigate the maximum stress.

When the maximum value of the above stress is 3 N/15 mm or more, it can be evaluated as having sufficient heat seal strength at this temperature; when it is 13 N/15 mm or less, it is evaluated as having tearability.

(8) easy tearability (functional test)

In order to investigate the tearability, a functional test by opening the package by hand was performed.

The heat seal layers of the composite film were heat-sealed with each other under the following conditions using a long pillow packaging machine (manufactured by Tokyo Kogyo Co., Ltd., model "TWX1N") to obtain a package having a length of 120 mm and a width of 100 mm.

Heat sealing temperature 120 ° C

Heat sealing time 0.6 seconds

Heat sealing pressure 0.5MPa

The surface of the unsealed composite film was grasped by fingers of the right hand and the left hand, respectively, 30 mm above the mouth of the heat-sealed bag of the obtained package, and opened by hand.

The tactile sensation (peeling feeling) at this time was evaluated as an index of easy tearability by the following criteria.

A: Easy and smooth peeling (very good)

B: Slightly resistive but easy to peel off (good)

C: The resistance is large but can be peeled off (may)

D: Unable to peel or the part other than the heat seal is broken (bad)

(9) tear opening

The tear-opening property of the heat-sealing layers of the two composite films was heat-sealed.

A rectangle of 150 mm × 100 mm was cut out from the composite film, and then two pieces were placed in a group, and the heat seal layers were joined to each other. The YSS heat sealer manufactured by Yasuda Seiki Co., Ltd. was heat-sealed on the four sides under the following conditions to obtain a bag-like body. The four sides of the pseudo-bag-like body are heat sealed to the ends.

Heat sealing temperature: 160 ° C

Heat sealing pressure: 0.1MPa

Heat sealing time: 1.0 seconds

Sealing width: 5mm

Using a cutter to obtain the end of the heat-sealed portion of the piece that is intended to be a bag-like body, After cutting the 10 mm incision in the vertical direction, the incision is pulled in the direction of the hand in the width direction (parallel to the direction of the surface of the bag-like body and perpendicular to the direction of the slit), and the force required at the time of pulling and the state of the tearing portion are investigated. Then, judged by the following criteria, and then evaluated by the following calculation formula.

The light force can be pulled straight from the slit, the film is not stretched and fluff appears, etc.: A (very good)

Feel slightly heavier when pulled open, but can be pulled straight out: B (good)

It feels very heavy when pulled open, and the stretched film will stretch and appear fluff: (bad)

The film is elongated by the slit and is not pulled apart: D (very bad)

The test was carried out by taking 10 test pieces from each of the three testers, and evaluating by the following formula (1), the ratio of the judged "A" in the total of 30 test pieces was expressed as a percentage.

Judging the ratio of "A" (%) = (determining the number of "A" ÷ 30) × 100 (1)

(10) Pinhole resistance

The flaw detection test of the heat seal portion is used as an index of pinhole resistance of the heat seal portion.

A rectangular film of 150 mm × 100 mm was cut out from the composite film, and the heat-sealed layer was folded inward from the center of the short side. The opening portion is left in one of the short side portions, and the other side (one side and the long side of the short side) is VSS heat sealer manufactured by Yasuda Seiki Seisakusho Co., Ltd., and the envelope-like pseudo-bag body is heat-sealed under the following conditions. .

Heat sealing temperature: 160 ° C

Heat sealing pressure: 0.1MPa

Heat sealing time: 1.0 seconds

Sealing width: 5mm

The dye-impregnated flaw detector "Immersion liquid FP-S standard type" manufactured by a misty Tashsett (sand) was sprayed into the opening of the pseudo-bag-making body, and the liquid leakage state of the sealing portion was visually observed, and the following criteria were used. to evaluate.

The heat seal is not leaking: ○ (good pinhole resistance)

Leakage in the heat seal: × (poor pinhole resistance)

Example 1 <Manufacture of multilayer film>

A total of three extruders using a single-axis extruder with a spiral diameter of 75 mm for the intermediate layer and two single-axis extruders with a spiral diameter of 50 mm for the two outer layers (laminate layer and heat seal layer) Three types of three-layer T-die type film forming apparatuses are constructed, and the resin is supplied to each extruder in the following manner.

Extruder for intermediate layer: b-LLDPE-1 (manufactured by Sumitomo Chemical Co., Ltd., article number: CU7004, melting point = 108 ° C, MFR = 3.0 g/10 min (190 ° C), Mw / Mn = 11.9, density = 0.924 g/cm ³ , amorphous component = 2.5% by weight, long chain branching amount = 4.12 / 1,000 C) 100 parts by weight

Press for laminating layer: PP-1 (made by Porrillo, Japan, article number: WFX4TA, melting point = 126 ° C, MFR = 7.0 g / 10 min (230 ° C), Mw / Mn = 3.0) 70 Parts by weight and PP-2 (Polylo, Japan) (stock) system, article number: FW3GT, melting point = 148 ° C, MFR = 7.0 g / 10 minutes (230 ° C), Mw / Mn = 5.3) 30 parts by weight of the mixture

Extruder for heat seal layer: PP-1 (made by Porrillo, Japan, article number: WFX4TA, melting point = 126 ° C, MFR = 7.0 g / 10 min (230 ° C), Mw / Mn = 3.0) 100 Each of the three extruders was extruded from each T die at a resin temperature of 220 ° C, a residence time of 1 minute, and a T die temperature of 230 ° C. The three layers were superposed and passed through a 25 ° C cooling roll. The multilayer film has a three-layer structure with a total thickness of 30 μm and a thickness structure of three layers of about 1:2:1.

Subsequently, the corona discharge treatment was carried out so that the surface wetting tension on the side of the laminate layer of the multilayer film was 42 mN/m, and then the polyolefin-based non-stretched multilayer film was obtained by aging at 40 ° C for 24 hours.

The above (1) to (6) evaluation was carried out using this polyolefin-based non-stretch multilayer film. The evaluation results are shown in Table 5.

<Manufacture of composite film>

The laminated layer of the above polyolefin-based non-stretched multilayer film was bonded to a biaxially stretched polypropylene film to produce a composite film.

Compared to the corona treated surface of the biaxially stretched polypropylene film (product number: Shanteku-OP PA20, thickness: 20 μm, single-sided corona treatment), using a coater (set 2 mil) Applying a dry laminating adhesive (15% of the main agent (product number: TM-595) made by Toyo Morton Co., Ltd., a hardener (product number: CTA-56) 2.7 g and ethyl acetate 36.8 g of the resulting solution was mixed and dried at 80 ° C for 1 minute. Second use A hand roll was attached to the adhesive layer of the polyolefin-based non-stretched multilayer film obtained above, and after lamination, the composite film was aged at 40 ° C for 3 days. Further, the above unit "mil" means 0.001 inch, and 1 mil is equivalent to about 25.5385 m.

The above (7) to (10) evaluation was carried out using the composite film obtained above. The evaluation results are shown in Table 5.

Examples 2 to 10 and Comparative Examples 1 to 4

The polyolefin-based non-stretch multilayer film and the composite film were produced in the same manner as in Example 1 except that the types and amounts of the resins of the extruders for supplying the respective layers in the above-mentioned Example 1 were as described in Tables 3 and 4.

The evaluation results are shown in Tables 5 and 6.

The code names of the resin materials in Tables 3 and 4 are as follows.

b-LLDPE-1: Sumitomo Chemical Co., Ltd., item number "CU7004"

b-LLDPE-2: Sumitomo Chemical Co., Ltd., item number "GT140"

b-LLDPE-3: Sumitomo Chemical Co., Ltd., item number "GH051"

LLDPE-1: Ube Maruyama Polyethylene Co., Ltd., item number "1540F"

LLDPE-2: Ube Maruzen Polyethylene Co., Ltd., product number "2040FC"

LLDPE-3: Shima Chemical Japan Co., Ltd., item number "KC8852G"

LDPE-1: Sumitomo Chemical Co., Ltd., item number "L405"

PP-1: Japan's Porillo (share) system, item number "WFX4TA"

PP-2: Japan's Porillo (stock) system, item number "FW3GT"

The parameters of the above resin raw materials are shown in Table 7 below.

The value of the MFR column of Table 7 is the melt flow rate measured in accordance with JIS K 7210 load 2.16 kg. The measurement temperature was 190 ° C for a polyethylene resin and 230 ° C for a polypropylene resin.

The melting point is the maximum temperature of the melting point as determined by differential scanning calorimetry (DSC).

The content of the long-chain branch represented by the "long-chain branch" column is calculated from the results of ¹³ C-NMR measured under the following conditions, and is calculated by the following formula (2), and the carbon number per 1,000 carbon atoms is 8 or more. The number of branches.

[ ¹³ C-NMR measurement conditions]

Measuring device: Japanese electronic (share) type "JNM-ECS400"

Solvent: mixed solvent of trichlorobenzene/heavy benzene (75/25% by volume)

Sample concentration: 80mg/2.5mL solution

Measurement mode: 1H-complete decoupling

Measuring temperature: 120 ° C

Pulse amplitude: 90 degree pulse

Pulse repetition time: 9 seconds

The total number of calculations: 9,000 times

Long chain branch content (units / 1000 C) = A ÷ B × 1,000 (2)

(In the formula (2), A is a peak area of a chemical shift δ = 22.87 ppm, and B is a peak area of a chemical shift δ = 30 ppm).

The content of the amorphous component is a temperature-melting and melting method under the following conditions, in which the column after the supply of the sample is cooled to 0° C., and then the solvent is supplied, and the fraction distilled during the period in which the column temperature is maintained at 0° C. is relative to The proportion by weight of the whole fraction.

Measuring device: Prerequisite science (stock) system, model "TREF device special type"

Column: inner diameter 10mm × 300mm

Filler: Cullo P NAW (Kinyer (share) system, 30/60mesh)

Sample solution concentration: 5mg/mL

Sample solution injection amount: 2mL

Solvent: o-dichlorobenzene

Flow rate: 1mL/min

Sample injection temperature: 140 ° C

Cooling speed: 5 ° C / h

Cooling arrival temperature: 0 ° C

Cooling arrival temperature maintenance time: 30 minutes

Heating rate: 5 ° C / h

Verifier: Infrared Verifier

Determination of wave number: 3.42 μm

Effect of the invention

The invention can provide polyolefins with excellent optical properties, resistance to retardation, low-temperature heat-sealing property, heat-sealing strength, sealing property and the like, and has excellent tear tearability and tearability of the polyolefin. Multilayer film.

The package formed of the multilayer film of the present invention is particularly suitable for use, for example, in food packaging applications and the like.

Claims (6)

A multilayer film characterized by comprising a laminate layer having an outermost layer, an intermediate layer of at least one layer, and a heat-sealable layer of another outermost layer, wherein the laminate layer is made of a polyolefin resin. Forming, at least one layer of the intermediate layer is formed of a polyolefin-based resin containing long-chain branched LLDPE, and the heat-sealing layer is formed of a polyolefin-based resin containing a polypropylene-based resin, and the polyolefin layer of the laminated layer is formed. The resin has a melting point higher than that of the polypropylene resin of the heat seal layer, and the long-chain branched LLDPE in the polyolefin resin of the intermediate layer has a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography. The ratio Mw/Mn of Mw to the number average molecular weight Mn is 7.5 to 15.0, the amount of the amorphous component measured by the temperature rising elution fractionation method is 1 to 4% by weight, and the carbon number measured by ¹³ C-NMR is 8 or more. The number of branches is 1.5 to 5.0 per 1,000 carbon atoms. The multilayer film according to claim 1, wherein the density of the long-chain branched LLDPE in the polyolefin resin of the intermediate layer is 0.90 to 0.94 g/cm ³ , and the melt flow measured at 190 ° C at a load of 2.16 kg according to JIS K 7210 The rate MFR is 0.1 to 20 g/10 minutes. The multilayer film according to claim 1 or 2, wherein the polyolefin resin of the intermediate layer contains 40% by weight or more of the polypropylene resin of 30% by weight or less of the long-chain branched LLDPE and 50% by weight or less. LLDPE (except for the aforementioned long-chain branch LLDPE). The multilayer film according to claim 1 or 2, wherein the polypropylene resin in the heat seal layer has a molecular weight distribution Mw/Mn of 1.5 to 3.5, and a melt flow rate MFR measured at 230 ° C under a load of 2.16 kg according to JIS K 7210. It is 1 to 30 g/10 min, has a melting point of 120 to 140 ° C, and further contains 70% by weight or more of a propylene-ethylene copolymer obtained by polymerization using a metallocene catalyst. A composite film obtained by laminating a laminate of a multilayer film according to any one of claims 1 to 4 on a film substrate. A package formed from the composite film of claim 5.