Polyolefin-based unoriented films and film laminates

Abstract

To provide polyolefin-based unoriented films and film laminates that maintain transparency while achieving both rigidity and impact resistance. [Solution] A polyolefin-based unoriented film comprising a layer made of a polyolefin-based resin composition, wherein the polyolefin-based resin composition consists of 60-95% by weight of a polyolefin-based resin and 5-40% by weight of a polypropylene-based resin having a crystallization temperature of 115°C or higher and an Mz+1 / Mn ratio of 35-50, and the total amount of polypropylene-based resin relative to the film is 3-30% by weight.

Description

Technical Field

[0001] The present invention relates to a polyolefin-based non-stretched film and a film laminate using this film.

Background Art

[0002] Conventionally, a film laminate in which a sealant film is laminated on a base film has been widely used as a film product such as a packaging material. In recent years, from the perspective of reducing environmental impact, reduction of plastics has been demanded, and measures such as reducing the thickness (thinning) of films including sealant films have been taken.

[0003] In the case of a packaging material, from the viewpoints of shape retention and content protection, it is required to maintain a firm feeling even when the film thickness is reduced, so it is necessary to improve the rigidity of the film. Therefore, as a method for increasing the rigidity of the film, for example, a technique of adding an alicyclic hydrocarbon resin and a nucleating agent (for example, see Patent Document 1) or an inorganic filler (for example, see Patent Document 2) to a polypropylene-based resin is known.

[0004] However, in the film in which an alicyclic hydrocarbon resin and a nucleating agent are added to a polypropylene-based resin as in Patent Document 1, although it is excellent in transparency and rigidity, the impact resistance is not satisfactory.

[0005] In addition, in the film in which an inorganic filler is added to a polypropylene-based resin as in Patent Document 2, although the rigidity increases, the transparency becomes insufficient. Furthermore, there is also a concern about poor appearance of the film due to fish eyes caused by the inorganic filler. As another problem, the addition of an inorganic filler makes it difficult to recycle the film, which is not preferable from the perspective of reducing environmental impact.

[0006] Also, a polypropylene-based resin multilayer film is known in which the rigidity is controlled by selecting an intermediate layer resin and the impact resistance is improved by using a polypropylene-based resin to which a hydrogenated vinyl aromatic diene-based copolymer is added as an outer layer (for example, see Patent Document 3).

[0007] However, the film described in Patent Document 3 has the problem of high manufacturing costs because its impact strength is improved by the addition of a hydrogenated vinyl aromatic diene copolymer. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2016-10925 [Patent Document 2] Japanese Patent Publication No. 2019-85127 [Patent Document 3] Japanese Patent Publication No. 2001-88254 [Overview of the project] [Problems that the invention aims to solve]

[0009] The present invention has been made in view of the above points, and provides a polyolefin-based unoriented film and film laminate that have transparency and appearance suitable for use as packaging material, while suppressing an increase in manufacturing costs, and that also have rigidity and impact resistance. [Means for solving the problem]

[0010] In other words, the first invention relates to a polyolefin-based unoriented film comprising a layer made of a polyolefin-based resin composition, wherein the polyolefin-based resin composition comprises 60 to 95% by weight of a polyolefin-based resin and 5 to 40% by weight of a polypropylene-based resin having a crystallization temperature of 115°C or higher as measured by differential scanning calorimeter (DSC) in accordance with JIS K 7121 (2012) and an Mz+1 / Mn of 35 to 50 as measured by gel permeation chromatography (GPC) in accordance with JIS K 7252-1 (2016), and the total amount of the polypropylene-based resin relative to the film is 3 to 30% by weight.

[0011] The second invention relates to a polyolefin-based unoriented film in which the polyolefin-based resin comprises at least one of a propylene homopolymer or a propylene-α-olefin random copolymer, in the first invention.

[0012] The third invention relates to a polyolefin-based unoriented film in which, in the first or second invention, the sum of the tensile moduli in the longitudinal (MD) direction and transverse (TD) direction, measured in accordance with JIS K 7127 (1999), is 1.50 GPa or more.

[0013] The fourth invention relates to a polyolefin-based unoriented film in which the haze value measured in accordance with JIS K 7136 (2000) is 5% or less, as described in the first or second invention.

[0014] The fifth invention relates to a polyolefin-based unoriented film in which the haze value measured in accordance with JIS K 7136 (2000) is 5% or less, as described in the third invention.

[0015] The sixth invention relates to a film laminate in which another resin film is laminated on one side of a polyolefin-based unoriented film described in the first or second invention.

[0016] The seventh invention relates to a film laminate in which another resin film is laminated on one side of the polyolefin-based unoriented film described in the third invention.

[0017] The eighth invention relates to a film laminate in which another resin film is laminated on one side of the polyolefin-based unoriented film described in the fourth invention.

[0018] The ninth invention relates to a film laminate in which another resin film is laminated on one side of the polyolefin-based unoriented film described in the fifth invention. [Effects of the Invention]

[0019] According to the polyolefin non-stretched film according to the first invention, it is a polyolefin non-stretched film including a layer made of a polyolefin resin composition. The polyolefin resin composition consists of 60 to 95% by weight of a polyolefin resin and 5 to 40% by weight of a polypropylene resin having a crystallization temperature of 115°C or higher measured in accordance with JIS K 7121 (2012) using a differential scanning calorimeter (DSC) and an Mz+1 / Mn of 35 to 50 measured in accordance with JIS K 7252-1 (2016) using gel permeation chromatography (GPC). Since the total layer equivalent amount of the polypropylene resin with respect to the film is 3 to 30% by weight, it is possible to obtain a film that has transparency and appearance suitable for use as a packaging material, while suppressing an increase in manufacturing cost and achieving both rigidity and impact resistance. Since the film has high rigidity, it can maintain a firm feeling even when thinned, contributing to reducing the environmental load.

[0020] According to the polyolefin non-stretched film according to the second invention, in the first invention, since the polyolefin resin contains at least one of a propylene homopolymer or a propylene-α-olefin random copolymer, it has high transparency and impact resistance.

[0021] According to the polyolefin non-stretched film according to the third invention, in the first or second invention, since the sum of the tensile elastic moduli in the longitudinal (MD) direction and the transverse (TD) direction measured in accordance with JIS K 7127 (1999) is 1.50 GPa or more, it has high rigidity.

[0022] According to the polyolefin non-stretched film according to the fourth invention, in the first or second invention, since the haze value measured in accordance with JIS K 7136 (2000) is 5% or less, it has high transparency.

[0023] According to the polyolefin non-stretched film according to the fifth invention, in the third invention, since the haze value measured in accordance with JIS K 7136 (2000) is 5% or less, it has high transparency.

[0024] According to the film laminate of the sixth invention, since another resin film is laminated on one side of the polyolefin-based unoriented film described in the first or second invention, it can be suitably used as a film product such as a packaging film that reduces environmental impact by using a thinned polyolefin-based unoriented film without impairing its stiffness.

[0025] According to the film laminate of the seventh invention, since another resin film is laminated on one side of the polyolefin-based unoriented film described in the third invention, it can be suitably used as a film product such as a packaging film that reduces environmental impact by using a thinned polyolefin-based unoriented film without impairing its stiffness.

[0026] According to the film laminate of the eighth invention, since another resin film is laminated on one side of the polyolefin-based unoriented film described in the fourth invention, it can be suitably used as a film product such as a packaging film that reduces environmental impact by using a thinned polyolefin-based unoriented film without impairing its stiffness.

[0027] According to the film laminate of the ninth invention, since another resin film is laminated on one side of the polyolefin-based unoriented film described in the fifth invention, it can be suitably used as a film product such as a packaging film that reduces environmental impact by using a thinned polyolefin-based unoriented film without impairing its stiffness. [Modes for carrying out the invention]

[0028] The polyolefin-based unoriented film according to one embodiment of the present invention is a film comprising a layer made of a polyolefin-based resin composition. "Unoriented" means a state in which no intentional stretching has been applied, and includes cases where unavoidable stretching occurs during film formation, etc. The polyolefin-based unoriented film of the present invention is manufactured by known film manufacturing methods such as the T-die method.

[0029] The polyolefin-based unoriented film is suitably used as a sealant film or the like when laminated on other resin films. The other resin films are, for example, films that can be used as packaging films for food, daily necessities, general merchandise, cosmetics, pharmaceuticals, and other products. A film laminate formed by laminating the other resin film on one side of the polyolefin-based unoriented film is suitably used, for example, as a packaging film or the like.

[0030] The polyolefin resin composition forming the layer of the polyolefin-based unoriented film consists of 60 to 95% by weight of polyolefin resin and 5 to 40% by weight of polypropylene resin. If the proportion of polyolefin resin in the polyolefin resin composition exceeds 95% by weight and the proportion of polypropylene resin is less than 5% by weight, the rigidity of the film is reduced. If the proportion of polyolefin resin in the polyolefin resin composition is less than 60% by weight and the proportion of polypropylene resin exceeds 40% by weight, the impact resistance of the film is reduced.

[0031] The polyolefin resin is selected from at least one of the following: propylene homopolymer, propylene-α-olefin random copolymer, or polyethylene resin. Preferably, the polyolefin resin contains at least one of propylene homopolymer or propylene-α-olefin random copolymer.

[0032] The melt flow rate (MFR) of the propylene homopolymer is not particularly limited. For example, a propylene homopolymer with an MFR of 0.1 to 20 g / 10 min, particularly 1 to 10 g / 10 min, measured under conditions of 230°C and a load of 2.16 kg in accordance with JIS K 7210 (2014), is preferably used.

[0033] A propylene-α-olefin random copolymer is a random copolymer of propylene and an appropriate α-olefin other than propylene. Examples of α-olefins include ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. These copolymers may be used individually or as a mixture of two or more.

[0034] Examples of propylene-α-olefin random copolymers include binary random copolymers of propylene and ethylene, binary random copolymers of propylene and α-olefin, and ternary random copolymers of propylene, ethylene, and 1-butene. Preferably, the propylene-α-olefin random copolymer is selected from at least one of propylene-ethylene random copolymers or propylene-ethylene-butene random copolymers.

[0035] The melt flow rate (MFR) of the propylene-α-olefin random copolymer is not particularly limited. For example, a propylene-α-olefin random copolymer with an MFR of 0.1 to 20 g / 10 min, particularly 1 to 10 g / 10 min, measured under conditions of 230°C and a load of 2.16 kg in accordance with JIS K 7210 (2014), is preferably used.

[0036] Examples of polyethylene resins include low-density polyethylene, high-density polyethylene, and linear low-density polyethylene. Linear low-density polyethylene is preferred as the polyethylene resin. The melt flow rate (MFR) of linear low-density polyethylene is not particularly limited. For example, linear low-density polyethylene with an MFR of 0.1 to 30 g / 10 min, particularly 1 to 10 g / min, measured in accordance with JIS K 7210 (2014) at 190°C and a load of 2.16 kg, is preferably used. The density of linear low-density polyethylene is not particularly limited. For example, a density of 0.965 g / cm³ measured in accordance with JIS K 7112 (2023) is preferred. 3 More preferably, 0.94 g / cm³ 3More preferably, 0.93 g / cm³ 3 The following will be used.

[0037] Polypropylene resins must have a crystallization temperature of 115°C or higher, as measured by differential scanning calorimeter (DSC) in accordance with JIS K 7121 (2012), and a Mz+1 / Mn ratio of 35-50, as measured by gel permeation chromatography (GPC) in accordance with JIS K 7252-1 (2016).

[0038] The crystallization temperature affects the rigidity of a polyolefin-based unoriented film containing a layer made of a polyolefin-based resin composition. If the crystallization temperature of the polypropylene-based resin contained in the polyolefin-based resin composition is too low, crystallization will be slow, which may reduce the degree of crystallinity and thus decrease the rigidity of the film. If the crystallization temperature of the polypropylene-based resin is 150°C or higher, crystallization will be rapid, resulting in smaller crystal sizes and improved degree of crystallinity, thus achieving good rigidity.

[0039] Mz+1 / Mn represents the molecular weight distribution of high molecular weight components and is an indicator of the abundance of high molecular weight components. Mn is the number-average molecular weight, which is a value obtained by simply averaging the number of molecules in the molecular composition. Mz+1 is the Z+1 average molecular weight, and is influenced by the higher molecular weight portion even more than Mz (Z average molecular weight), which is a value that is more easily influenced by the presence of high molecular weights than Mw (weight-average molecular weight), which is a value obtained by multiplying the number of molecules by their molecular weight and then averaging it. Note that Mz+1 is defined by the following equation (i) and Mz is defined by the following equation (ii).

[0040] Mz+1=Σ(Ni·Mi 4 ) / Σ(Ni·Mi 3 ) … (i)

[0041] Mz = Σ(Ni·Mi) 3 ) / Σ(Ni·Mi 2 ) … (ii)

[0042] Mz+1 / Mn is an index representing the molecular weight distribution of high molecular weight components. A larger Mz+1 / Mn indicates a higher proportion of high molecular weight components. A higher proportion of high molecular weight components tends to result in a higher crystallization temperature. A moderately high crystallization temperature leads to faster crystallization, resulting in smaller crystal sizes and improved crystallinity, thus achieving good rigidity. A Mz+1 / Mn value of 35-50 results in a suitably high crystallization temperature, thus achieving good rigidity. If Mz+1 / Mn is too low, the high molecular weight components decrease, lowering the crystallization temperature and consequently slowing down crystallization. This can lead to a decrease in crystallinity and potentially reduce the rigidity of the film. If Mz+1 / Mn is too high, the high molecular weight components increase, which may result in appearance defects due to unmelted polypropylene resin when producing polyolefin-based unoriented films.

[0043] The melt flow rate (MFR) of the polypropylene resin is not particularly limited. For example, polypropylene resins with an MFR of 0.1 to 20 g / 10 min, particularly 1 to 10 g / min, measured under conditions of 230°C and a load of 2.16 kg in accordance with JIS K 7210 (2014), are preferably used.

[0044] The layer structure of the polyolefin-based unoriented film of the present invention may be either single-layer or multi-layer. When the polyolefin-based unoriented film has a multi-layer structure, it is preferable that the layer made of the polyolefin-based resin composition is at least one of the following: a base layer or a first surface layer provided on one side of the base layer.

[0045] When considering the case where the polyolefin-based unoriented film has a multilayer structure, the amount of polypropylene resin relative to the total layers of the film must be 3 to 30% by weight. If the amount of polypropylene resin relative to the total layers is less than 3% by weight, it will reduce the rigidity of the film, and if it exceeds 30% by weight, it will reduce the impact resistance of the film.

[0046] The thickness of the polyolefin-based unoriented film is set appropriately according to the application, etc. For example, 10 to 100 μm is preferred, and 15 to 70 μm is more preferred. The ratio of the thicknesses of each layer of the polyolefin-based unoriented film (layer ratio) is determined appropriately according to the application, etc. If the polyolefin-based unoriented film has a three-layer structure consisting of a base layer, a first surface layer provided on one side of the base layer, and a second surface layer provided on the other side of the base layer, the ratios of the first surface layer, base layer, and second surface layer in the total layers are preferably, for example, 10 to 33.3%, 33.4% to 80%, and 10 to 33.3%. In other words, the layer ratio of the first surface layer: base layer: second surface layer is preferably, for example, 1:8:1 to 1:1:1.

[0047] The polyolefin-based unoriented film of the present invention preferably has a sum of tensile modulus in the longitudinal (MD) direction and transverse (TD) direction of 1.50 GPa or higher, as a physical property required for various applications such as packaging films. The tensile modulus is a value measured in accordance with JIS K 7127 (1999). Tensile modulus is used as one of the indicators of film stiffness. A higher tensile modulus value indicates that the film has higher stiffness and a stronger rigidity. By having a sum of tensile modulus in the longitudinal (MD) direction and transverse (TD) direction of 1.50 GPa or higher, sufficient rigidity can be obtained even when the film is made thin. If the sum of tensile modulus in the longitudinal (MD) direction and transverse (TD) direction is too low, the film will have poor rigidity when made thin, which may make it difficult to maintain the shape of packaging materials such as packaging films using the film, or make it difficult to protect the contents.

[0048] The polyolefin-based unoriented film of the present invention preferably has a dirt impact strength of 0.16 J or higher for a 30 μm thick film, as this is a physical property required for various applications such as packaging films. The dirt impact strength is a value measured in accordance with JIS K 7124-1 (1999). Dirt impact strength is used as one of the indicators of penetration failure. A higher dirt impact strength indicates that the film has higher impact resistance. From the viewpoint of impact resistance required for various applications such as packaging films, it is preferable that the dirt impact strength of a 30 μm thick polyolefin-based unoriented film is 0.16 J or higher. Note that the dirt impact strength tends to increase as the thickness of the film increases. If the dirt impact strength of a polyolefin-based unoriented film is too low, it may have poor impact resistance and be more likely to tear under impact.

[0049] The polyolefin-based unoriented film of the present invention preferably has the transparency required for various applications such as packaging films. The transparency of the film is represented by the haze measured in accordance with JIS K 7136 (2000). A preferred haze value for this film is 5% or less. If the haze value is too high, the transparency generally required for packaging films and the like will be insufficient, and therefore undesirable.

[0050] In polyolefin-based unoriented films, additives are added as needed. Examples of additives include antioxidants, neutralizing agents, antistatic agents, antifogging agents, lubricants, nucleating agents, and colorants.

[0051] In the polyolefin-based unoriented film of the present invention, in order to broaden the range of applications as a sealant film, it is preferable that, if the film has a single-layer structure consisting only of a substrate layer, one side thereof, or if the film has a multilayer structure, the first surface layer thereof, be surface-treated to have a wetting tension of 36 mN / m or more. Examples of surface treatments include known treatments such as atmospheric pressure plasma treatment, flame treatment, and corona discharge treatment. The wetting tension is measured in accordance with JIS K 6768 (1999). If the wetting tension is less than 36 mN / m, it is undesirable as it may cause printing defects or lamination defects.

[0052] As described above, the polyolefin-based unoriented film of the present invention includes a layer made of a polyolefin resin composition comprising 60-95% by weight of a polyolefin resin and 5-40% by weight of a polypropylene resin having a crystallization temperature of 115°C or higher and an Mz+1 / Mn ratio of 35-50, characterized in that the total amount of the polypropylene resin relative to the film is 3-30% by weight. By blending an appropriate amount of polypropylene resin satisfying the above conditions into the layer made of the polyolefin resin composition, it is possible to achieve both rigidity and impact resistance while maintaining the transparency of the film. Because the polyolefin-based unoriented film of the present invention has high rigidity, sufficient stiffness can be obtained even when the film is made thin. Therefore, this film can reduce the amount of plastic in film products such as packaging films that include this film compared to conventional products, thus greatly contributing to reducing the environmental burden. Furthermore, the polyolefin-based unoriented film of the present invention can be subjected to vapor deposition treatment or printing.

[0053] In the polyolefin-based unoriented film of the present invention, a film laminate can be formed by laminating another resin film to one side of the film. Examples of other resin films that can be used include biaxially oriented polypropylene film (e.g., Futamura Chemical Co., Ltd., product name "FOR", thickness 20 μm). By using a resin film made of the same or substantially the same material as the polyolefin-based unoriented film, the resulting film laminate, or the packaging material or packaging bag using the film laminate, can be made into a monomaterial. The lamination method is not particularly limited. For example, known methods such as dry lamination, extrusion lamination, or hot melt lamination can be employed depending on the purpose.

[0054] The resulting film laminate possesses high rigidity in the polyolefin-based unoriented film, and the film can be thinned (volume reduced) without impairing the shape retention performance of the film laminate. Therefore, it can be suitably used as a film product such as a packaging film that reduces environmental impact. [Examples]

[0055] [Preparation of polyolefin-based unoriented films] In the preparation of the polyolefin-based unoriented films for prototype examples 1 to 23, each material described later was kneaded and melted according to a predetermined mixing ratio (weight %), co-extruded using the T-die method, and cooled with a cooling roll. Subsequently, if the film had a single-layer structure, corona discharge treatment was applied to one side of the base layer, or if it had a three-layer structure, to the first surface layer, thereby producing a polyolefin-based unoriented film.

[0056] The thickness of each fabricated film was measured in accordance with JIS K 7130 (1999). When the polyolefin-based unoriented film had a three-layer structure, the thickness ratio of each layer was adjusted by the discharge amount from the T-die, and the thickness obtained from measuring the molded film was apportioned according to the set ratio to determine the ratio (layer ratio). The mixing ratios of the resin materials used in each layer of prototype examples 1 to 23 are shown in Tables 1 to 4 below.

[0057] [Materials used] The following resins were used as the resin material for each layer. For each material, the melt flow rate (MFR) was measured in accordance with JIS K 7210 (2014) using a melt indexer (Toyo Seiki Seisakusho Co., Ltd., "G-01"). At this time, the measurement was taken at a test temperature of 230°C for all materials except linear low-density polyethylene (LLDPE), and the value for LLDPE was taken at a test temperature of 190°C.

[0058] Furthermore, for each material, the crystallization temperature (°C) and melting point (°C) were measured using a differential scanning calorimeter (NETZSCH, DSC214 Polyma) in accordance with JIS K 7121 (2012).

[0059] Furthermore, the molecular weight and molecular weight distribution of each material were measured in accordance with JIS K 7252 (2016). For the measurements, a high-temperature GPC apparatus (HLC-8321GPC / HT, manufactured by Tosoh Corporation) was used, with two columns, "TSKgel guardcolumn HHR(S)" and "TSKgel GMHHR-H(S)HT," and a differential refractometer as the detector. o-dichlorobenzene was used as the eluent, and the sample concentration was adjusted to 0.1 wt / vol% for complete dissolution. The column and injector temperatures were set to 145°C, and the flow rate to 1.0 mL / min. Polystyrene was used as the standard substance for molecular weight conversion. From the molecular weight distribution curve obtained from this measurement, the molecular weight distribution (Mz+1 / Mn) of the high molecular weight component was determined.

[0060] <Polyolefin resins> • Resin PO1: Propylene-ethylene random copolymer (MFR 7g / 10min, crystallization temperature 102℃, melting point 135℃, Mz+1 / Mn 7.4) • Resin PO2: Propylene-ethylene-butene random copolymer (MFR 7g / 10min, crystallization temperature 96℃, melting point 140℃, Mz+1 / Mn 39.6) • Resin PO3: Linear low-density polyethylene (MFR 5.5g / 10min, crystallization temperature 102℃, melting point 117℃, Mz+1 / Mn 6.6) • Resin PO4: Propylene homopolymer (MFR 3g / 10min, crystallization temperature 112℃, melting point 165℃, Mz+1 / Mn 92.5) • Resin PO5: Propylene homopolymer (MFR 7.5g / 10min, crystallization temperature 114℃, melting point 166℃, Mz+1 / Mn 100.0)

[0061] <Polypropylene resin> • Resin PP1: Polypropylene resin (MFR 8g / 10min, crystallization temperature 119℃, melting point 155℃, Mz+1 / Mn 39.8) • Resin PP2: Polypropylene resin (MFR 2.8g / 10min, crystallization temperature 120℃, melting point 155℃, Mz+1 / Mn 40.2) • Resin PP3: Polypropylene resin (MFR 1.3g / 10min, crystallization temperature 120℃, melting point 155℃, Mz+1 / Mn 46.5) • Resin PP4: Polypropylene resin (MFR 6g / 10min, crystallization temperature 121℃, melting point 159℃, Mz+1 / Mn 197.3)

[0062] [Prototype Example 1] Prototype Example 1 is a single-layer structure consisting only of a base layer. The base layer is made by blending 95% by weight of polyolefin resin PO1 and 5% by weight of polypropylene resin PP1, and forming a film with a thickness of 30 μm. The total amount of polypropylene resin relative to the film is 5.0% by weight.

[0063] [Prototype Example 2] Prototype Example 2 is a film obtained by forming a film using the same method as Prototype Example 1, except that the base layer consisted of 90% by weight of resin PO1 and 10% by weight of resin PP1. The total amount of polypropylene resin relative to the film is 10.0% by weight.

[0064] [Prototype Example 3] Prototype Example 3 is a film obtained by blending 100% by weight of polyolefin resin PO2 as the first surface layer, 95% by weight of polyolefin resin PO2 and 5% by weight of polypropylene resin PP1 as the base layer, and 100% by weight of polyolefin resin PO2 as the second surface layer, with a layer ratio of 1:4:1 for the first surface layer:base layer:second surface layer, and producing a film with a thickness of 30 μm. The total amount of polypropylene resin relative to the film is 3.3% by weight.

[0065] [Prototype Example 4] Prototype Example 4 is a film obtained by forming a film using the same method as Prototype Example 3, except that the base layer consisted of 90% by weight of PO2 resin and 10% by weight of PP1 resin. The total amount of polypropylene resin relative to the film is 6.7% by weight.

[0066] [Prototype Example 5] Prototype Example 5 is a film obtained by forming a film identical to that of Prototype Example 3, except that the base layer consisted of 80% by weight of the resin PO2 and 20% by weight of the resin PP1. The total amount of polypropylene resin relative to the film is 13.3% by weight.

[0067] [Prototype Example 6] Prototype Example 6 is a film obtained by forming a film using the same method as Prototype Example 3, except that the base layer consisted of 70% by weight of PO2 resin and 30% by weight of PP1 resin. The total amount of polypropylene resin relative to the film is 20.0% by weight.

[0068] [Prototype Example 7] Prototype Example 7 is a film obtained by manufacturing a film identical to that of Prototype Example 6, except that the resin PO2 in the first surface layer, base layer, and second surface layer was changed to resin PO1. The total amount of polypropylene resin relative to the film is 20.0% by weight.

[0069] [Prototype Example 8] Prototype Example 8 is a film obtained by forming a film identical to that of Prototype Example 3, except that the base layer consisted of 60% by weight of the resin PO2 and 40% by weight of the resin PP1. The total amount of polypropylene resin relative to the film is 26.7% by weight.

[0070] [Prototype Example 9] Prototype Example 9 is a film obtained by forming a film using the same method as Prototype Example 3, except that the base layer does not contain a polypropylene resin, and instead uses 100% by weight of a polyolefin resin, PO2. The total amount of polypropylene resin relative to the film is 0.0% by weight.

[0071] [Prototype Example 10] Prototype Example 10 is a film obtained by forming a film with the same specifications as Prototype Example 3, except that the base layer consisted of 98% by weight of the resin PO2 and 2% by weight of the resin PP1. The total amount of polypropylene resin relative to the film is 1.3% by weight.

[0072] [Prototype Example 11] Prototype Example 11 is a film obtained by forming a film identical to that of Prototype Example 3, except that the base layer consisted of 50% by weight of PO2 resin and 50% by weight of PP1 resin. The total amount of polypropylene resin relative to the film is 33.3% by weight.

[0073] [Prototype Example 12] Prototype 12 is a film obtained by fabricating a film identical to that of Prototype 6, except that the layer ratio of the first surface layer:substrate layer:second surface layer was set to 1:6:1. The total amount of polypropylene resin relative to the film is 22.5% by weight.

[0074] [Prototype Example 13] Prototype 13 is a film obtained by fabricating a film identical to that of Prototype 6, except that the layer ratio of the first surface layer: substrate layer: second surface layer was set to 1:8:1. The total amount of polypropylene resin relative to the film is 24.0% by weight.

[0075] [Prototype Example 14] Prototype Example 14 is a film obtained by manufacturing a film identical to that of Prototype Example 5, except that the polypropylene resin in the base layer was changed from resin PP1 to resin PP2. The total amount of polypropylene resin in the film, calculated on a total layer basis, is 13.3% by weight.

[0076] [Prototype Example 15] Prototype 15 is a film obtained by manufacturing a film identical to that of Prototype 5, except that the polypropylene resin in the base layer was changed from resin PP1 to resin PP3. The total amount of polypropylene resin in the film, calculated on a total layer basis, is 13.3% by weight.

[0077] [Prototype Example 16] Prototype 16 is a film obtained by forming a film identical to that of Prototype 3, except that the first surface layer is made by blending 30% by weight of polypropylene resin PP1 to make 70% by weight of resin PO2, and the base layer is made by 100% by weight of polyolefin resin PO2 without blending any polypropylene resin. The total amount of polypropylene resin in the film, calculated on a total layer basis, is 5.0% by weight.

[0078] [Prototype Example 17] Prototype Example 17 is a film obtained by forming a film identical to that of Prototype Example 6, except that the first surface layer was made by blending 20% ​​by weight of polypropylene resin PP1 and 80% by weight of resin PO2. The total amount of polypropylene resin in the film, calculated on a total layer basis, is 23.3% by weight.

[0079] [Prototype Example 18] Prototype Example 18 is a film obtained by manufacturing a film identical to that of Prototype Example 5, except that the polypropylene resin in the base layer was changed from resin PP1 to resin PP4. The total amount of polypropylene resin in the film, calculated on a total layer basis, is 13.3% by weight.

[0080] [Prototype Example 19] Prototype Example 19 is a film obtained by forming a film identical to that of Prototype Example 5, except that the polypropylene resin PP1 in the base layer was changed to a polyolefin resin PO4. The total amount of polypropylene resin in the film, calculated on a total layer basis, is 0.0% by weight.

[0081] [Prototype Example 20] Prototype Example 20 is a film obtained by manufacturing a film identical to that of Prototype Example 16, except that the polypropylene resin PP1 of the first surface layer was changed to a polyolefin resin PO4. The total amount of polypropylene resin in the film, calculated on a total layer basis, is 0.0% by weight.

[0082] [Prototype Example 21] Prototype Example 21 is a film obtained by fabricating a film identical to that of Prototype Example 3, except that the resin PO2 in the first surface layer, base layer, and second surface layer was all changed to resin PO1, and the resin PO1 in the base layer was set to 60% by weight, resin PO3 to 10% by weight, and resin PP1 to 30% by weight. The total amount of polypropylene resin in the film, calculated on a total layer basis, is 20.0% by weight.

[0083] [Prototype Example 22] Prototype Example 22 is a film obtained by manufacturing a film identical to that of Prototype Example 3, except that the resin PO2 in the first surface layer, base layer, and second surface layer was all changed to resin PO1, and the resin PO1 in the base layer was set to 60% by weight, resin PO4 to 20% by weight, and resin PP1 to 20% by weight. The total amount of polypropylene resin in the film, calculated on a total layer basis, is 13.3% by weight.

[0084] [Prototype Example 23] Prototype 23 is a film obtained by fabricating a film identical to that of Prototype 4, except that the resin PO2 in both the first and second surface layers was changed to resin PO1, and the resin PO2 in the base layer was changed to resin PO5. The total amount of polypropylene resin relative to the film is 6.7% by weight.

[0085] [Table 1]

[0086] [Table 2]

[0087] [Table 3]

[0088] [Table 4]

[0089] The performance of the polyolefin-based unoriented films of prototype examples 1 to 23 was evaluated in terms of moldability, haze, tensile modulus, and dirt impact strength. The results and evaluations of each test are shown in Tables 5 to 8 below.

[0090] [Moldability] In determining moldability, the films for prototypes 1-23 were visually inspected for defects such as fisheyes during production. A good appearance was judged as "Good (○)," and any defects were judged as "Unacceptable (×)."

[0091] [Haze value] Haze (%) is an indicator of transparency, and was measured using a haze meter (NDH-8000, manufactured by Nippon Denshoku Industries Co., Ltd.) according to the test method compliant with JIS K 7136 (2000). For the polyolefin-based unoriented films of prototype examples 1 to 23, a haze value of 5.0% or less was judged as "good (〇)" and a value exceeding 5.0% was judged as "unacceptable (×)" in terms of the transparency required for packaging films.

[0092] [Tensile modulus of elasticity] The tensile modulus (GPa) was measured in two directions: the longitudinal direction (MD), which is the winding direction of the film, and the transverse direction (TD), which is perpendicular to the longitudinal direction, using a tensile testing machine (Tensilon Universal Material Tester RTF-1310, manufactured by A&D Co., Ltd.) based on the test method for plastic tensile properties conforming to JIS K 7127 (1999). The sum of the tensile moduli in the MD and TD directions was also calculated. As a stiffness requirement for packaging films, a sum of the tensile moduli in the MD and TD directions of 1.50 GPa or higher was judged as "Good (〇)", and a sum of less than 1.50 GPa was judged as "Unacceptable (×)".

[0093] [Dirt impact strength] The dart impact strength (J) is an indicator of penetration failure. The dart impact strength (J) was measured in accordance with JIS K 7124-1 (1999) using a dart impact tester with a low-temperature chamber (manufactured by Toyo Seiki Seisakusho Co., Ltd.). In this measurement, prototype examples 1 to 23 were fixed horizontally with a fixing device, and the fracture energy (J) when a dart with adjusted mass (mass: 150g, hemispherical metal penetration part: diameter 25.4mm) was dropped to break and penetrate the film was determined. From the perspective of impact resistance required for packaging films, a measurement result of 0.16 (J) or higher was judged as "good (〇)", and a result of less than 0.16 (J) was judged as "unacceptable (×)".

[0094] Furthermore, since a defect in the appearance was confirmed in prototype example 18, other film performance parameters (haze, tensile modulus, and dirt impact strength) were not measured.

[0095] [Table 5]

[0096] [Table 6]

[0097] [Table 7]

[0098] [Table 8]

[0099] [Results and Discussion] Of the prototype films described above, prototypes 9-11 and 18-20 were the ones that did not achieve sufficient film performance. Unlike the other films that achieved good film performance, prototypes 9, 19, and 20 consisted of a layer (substrate layer or first surface layer) made of a polyolefin resin composition consisting only of polyolefin resin (resin PO2, or resin PO2 and resin PO4), and did not contain polypropylene resin. Prototypes 10 and 11 both included a substrate layer made of a polyolefin resin composition. In prototype 10, the proportion of polypropylene resin in the substrate layer was insufficient compared to the other films that achieved good film performance. In prototype 11, the proportion of polypropylene resin in the substrate layer was excessive compared to the other films that achieved good film performance. In prototype 18, the proportion of polypropylene resin in the polyolefin resin composition was equivalent to that of prototypes 5, 14, and 15, which achieved good film performance. From these findings, it can be concluded that the PP4 resin used in prototype example 18 is unsuitable as a polypropylene-based resin for obtaining good film performance.

[0100] Therefore, by comparing the physical properties of the polypropylene resins that yielded good results (resins PP1, PP2, PP3) with those of the polypropylene resin PP4, it is considered that the preferred physical properties of a polypropylene resin are a crystallization temperature of 115°C or higher, as measured by differential scanning calorimeter (DSC), and an Mz+1 / Mn ratio of 35-50, as measured by gel permeation chromatography (GPC).

[0101] On the other hand, the melt flow rate (MFR) of the polypropylene resin PP4 falls within the range of the melt flow rates of the polypropylene resins (PP1, PP2, and PP3) that yielded good results. Therefore, it is considered that the melt flow rate of the polypropylene resin does not affect the film performance.

[0102] From a comparison between prototype example 5 and prototype example 19, and between prototype example 16 and prototype example 20, even considering that good film performance could not be obtained when the polypropylene resin (resin PP1) blended into the polyolefin resin composition forming the layer (substrate layer or first surface layer) was replaced with a propylene homopolymer (resin PO4), which is classified as a polyolefin resin, it is considered that a good film can be obtained by using a polypropylene resin having the above physical properties.

[0103] Next, we investigated the preferred blending ratio of polypropylene resin. Prototypes 9, 19, and 20 did not contain polypropylene resin, and prototype 10 had an insufficient blending ratio. The films of prototypes 9, 10, 19, and 20 did not provide sufficient rigidity. Prototype 11 had an excessive blending ratio. The film of prototype 11 did not provide sufficient impact resistance. Therefore, from prototypes 1 to 8, which yielded good results, it is considered that a preferred film that balances rigidity and impact resistance can be obtained when the blending ratio of polypropylene resin in the polyolefin resin composition is 5 to 40% by weight.

[0104] Furthermore, a comparison of prototype films 9-11 and 18-20, which did not achieve sufficient film performance, with other films that did achieve good film performance suggests that a good film can be obtained when the total amount of polypropylene resin relative to the film is 3-30% by weight.

[0105] In prototypes 6, 12, and 13, the blending ratio of polypropylene resin in the polyolefin resin composition is the same, but the layer ratio (first surface layer: base layer: second surface layer) is different. Since good results were obtained in prototypes 6, 12, and 13, it is considered that even if the layer ratio is changed, as long as the blending ratio of polypropylene resin in the layers made of the polyolefin resin composition and the total amount of polypropylene resin in the film are within the above-mentioned preferred range, there will be no significant change in film performance.

[0106] Prototypes 1 and 2 are single-layer films consisting of a base layer made of a polyolefin resin composition. Prototypes 3 to 8 are three-layer films consisting of a base layer made of a polyolefin resin composition, a first surface layer, and a second surface layer. In all of the base layers of prototypes 1 to 8, polypropylene resin was blended in the preferred proportions described above, and good film performance was obtained in all cases. Therefore, regardless of whether the film is single-layer or multi-layer, it is considered that if the blending ratio of polypropylene resin in the layers made of the polyolefin resin composition, and the total amount of polypropylene resin in the film (calculated as total layers), are within the preferred range described above, there will be no significant change in film performance.

[0107] Prototype Example 6 is a film having a base layer made of a polyolefin resin composition, while Prototype Example 16 is a film having a first surface layer made of a polyolefin resin composition. In both Prototype Examples 6 and 16, polypropylene resin was blended into the base layer or first surface layer made of a polyolefin resin composition in the above-mentioned preferred blending ratio, and good film performance was obtained in both cases. Therefore, it is considered that regardless of whether the layer made of a polyolefin resin composition is the base layer or the first surface layer, as long as the blending ratio of polypropylene resin in the layer and the total amount of polypropylene resin in the film are within the above-mentioned preferred range, there will be no significant change in film performance.

[0108] Prototype Example 17 is a film in which both the base layer and the first surface layer are made of a polyolefin resin composition. In the film of Prototype Example 17, polypropylene resin is blended in the base layer and the first surface layer in the preferred blending ratio described above. Since good results were obtained for Prototype Example 17, it is considered that regardless of whether there is one layer or multiple layers made of polyolefin resin composition in the film, as long as the blending ratio of polypropylene resin in each layer made of polyolefin resin composition and the total amount of polypropylene resin in the film are within the preferred range described above, there will be no significant change in film performance.

[0109] Next, we will examine the polyolefin resins used in the polyolefin resin compositions. Prototype Example 6 is a film using propylene-ethylene-butene random copolymer (resin PO2) as the polyolefin resin, and Prototype Example 7 is a film using propylene-ethylene random copolymer (resin PO1). Prototype Example 23 is a film using propylene homopolymer (resin PO5) as the polyolefin resin.

[0110] Furthermore, prototype example 21 is a film using a mixture of propylene-ethylene random copolymer (resin PO1) and linear low-density polyethylene (resin PO3) as the polyolefin resin. Prototype example 22 is a film using a mixture of propylene-ethylene random copolymer (resin PO1) and propylene homopolymer (resin PO4) as the polyolefin resin.

[0111] In prototype examples 6, 7, and 21-23, the polypropylene resin was blended in the preferred proportions described above, and good film performance was obtained in all cases. Therefore, it is considered preferable that the polyolefin resin in the layered polyolefin resin composition is a resin containing at least one of a propylene homopolymer or a propylene-α-olefin random copolymer.

[0112] Based on the evaluation of each prototype example, it was shown that in a polyolefin-based unoriented film containing a layer made of a polyolefin-based resin composition, the polyolefin-based resin composition preferably consists of 60-95% by weight of polyolefin-based resin and 5-40% by weight of polypropylene-based resin, which has a crystallization temperature of 115°C or higher as measured by differential scanning calorimeter (DSC) and an Mz+1 / Mn of 35-50 as measured by gel permeation chromatography (GPC), and the total amount of polypropylene-based resin relative to the film layer is preferably 3-30% by weight. Such a polyolefin-based unoriented film was shown to have excellent moldability, transparency, rigidity, and impact resistance. [Industrial applicability]

[0113] In the polyolefin-based unoriented film of the present invention, when the polypropylene resin in the layered polyolefin resin composition satisfies predetermined conditions for crystallization temperature and Mz+1 / Mn, and when the blending ratio and total layer amount of this polypropylene resin in relation to the film also satisfy predetermined conditions, it is possible to achieve transparency and appearance suitable for use as packaging material, while simultaneously achieving rigidity and impact resistance, while suppressing an increase in manufacturing costs. Therefore, it is possible to provide a polyolefin-based unoriented film and a film laminate using this film that can contribute to reducing environmental impact, and it is promising as a replacement for conventional polyolefin-based unoriented films and their film laminates.

Claims

1. A polyolefin-based unoriented film comprising a layer made of a polyolefin-based resin composition, The aforementioned polyolefin resin composition, 60-95% by weight of polyolefin resin, The composition consists of 5 to 40% by weight of a polypropylene resin whose crystallization temperature, as measured by differential scanning calorimeter (DSC) in accordance with JIS K 7121 (2012), is 115°C or higher, and whose Mz+1 / Mn, as measured by gel permeation chromatography (GPC) in accordance with JIS K 7252-1 (2016), is 35 to 50. The total amount of the polypropylene resin relative to the film is 3 to 30% by weight. A polyolefin-based unstretched film characterized by the following features. Mz+1: Z+1 average molecular weight Mn: number average molecular weight

2. The polyolefin-based unstretched film according to claim 1, wherein the polyolefin-based resin comprises at least one of a propylene homopolymer or a propylene-α-olefin random copolymer.

3. The polyolefin-based unoriented film according to claim 1 or 2, wherein the sum of the tensile moduli in the longitudinal (MD) direction and transverse (TD) direction, measured in accordance with JIS K 7127 (1999), is 1.50 GPa or more.

4. The polyolefin-based unoriented film according to claim 1 or 2, characterized in that the haze value measured in accordance with JIS K 7136 (2000) is 5% or less.

5. The polyolefin-based unoriented film according to claim 3, characterized in that the haze value measured in accordance with JIS K 7136 (2000) is 5% or less.

6. A film laminate comprising a polyolefin-based unoriented film according to claim 1 or 2, with another resin film laminated on one side.

7. A film laminate comprising a polyolefin-based unoriented film according to claim 3, wherein another resin film is laminated on one side.

8. A film laminate comprising a polyolefin-based unoriented film according to claim 4, wherein another resin film is laminated on one side.

9. A film laminate comprising a polyolefin-based unoriented film according to claim 5, wherein another resin film is laminated on one side.

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