Polypropylene-based unoriented film and film laminate

Abstract

To provide polypropylene-based unoriented films and film laminates that have excellent transparency, low-temperature heat sealability, and heat seal strength, while simultaneously achieving rigidity and impact resistance, all while suppressing increases in manufacturing costs. [Solution] The laminate layer of the polypropylene-based unoriented film mainly consists of a polyolefin resin, either a propylene-α-olefin random copolymer or linear low-density polyethylene. The base layer has a composition of 50-95% by weight of propylene-α-olefin random copolymer and 5-50% by weight of propylene homopolymer with a crystallization temperature of 114°C or higher as measured by DSC. The sealant layer consists of a propylene-α-olefin random copolymer, and the heat of fusion of the polypropylene-based unoriented film measured by DSC is 2.5-40 J / g at a fractionation temperature of 150°C or higher.

Description

Technical Field

[0001] The present invention relates to a polypropylene-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 viewpoint of reducing environmental load, 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 (see, for example, Patent Document 1) or an inorganic filler (see, for example, 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] Further, in the film in which an inorganic filler is added to a polypropylene-based resin as in Patent Document 2, although the rigidity is increased, the transparency becomes insufficient. As another problem, the addition of an inorganic filler makes it difficult to recycle the film, which is not preferable from the viewpoint of reducing environmental load.

[0006] Also known is a polypropylene-based resin multilayer film in which the rigidity is controlled by selecting an intermediate layer resin, the heat sealability is improved by using a random polypropylene resin as the inner layer, and the impact resistance is improved by using a polypropylene-based resin added with a hydrogenated vinyl aromatic diene-based copolymer as the outer layer (see, for example, 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. Therefore, there is a need for a polypropylene-based unoriented film that has transparency, low-temperature heat sealability, and heat seal strength suitable for use as a packaging material, while suppressing the increase in manufacturing costs, and that also achieves both rigidity and impact resistance. [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 Initiative] [Problems that the invention aims to solve]

[0009] The present invention has been made in view of the above points, and provides a polypropylene-based unoriented film and film laminate that have transparency, low-temperature heat sealability, and heat seal strength suitable for use as packaging materials, 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 polypropylene unoriented film comprising a laminate layer, a base layer, and a sealant layer in that order, wherein the laminate layer mainly consists of a polyolefin resin, either a propylene-α-olefin random copolymer or linear low-density polyethylene; the base layer has a composition of 50-95% by weight of a propylene-α-olefin random copolymer and 5-50% by weight of a propylene homopolymer whose crystallization temperature, as measured by differential scanning calorimeter (DSC) in accordance with JIS K 7121 (2012), is 114°C or higher; and the sealant layer is made of a propylene-α-olefin random copolymer, wherein the heat of fusion of the polypropylene unoriented film, as measured by differential scanning calorimeter (DSC) in accordance with JIS K 7122 (2012), is 2.5-40 J / g at a fractionation temperature of 150°C or higher.

[0011] The second invention relates to a polypropylene-based unoriented film in which, in the first 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 1.55 GPa or more.

[0012] The third invention relates to a polypropylene-based unoriented film in which, in the first or second invention, the maximum heat seal strength in the heat seal temperature range of 130 to 160°C is 12.5 N / 15 mm or more.

[0013] The fourth invention relates to a polypropylene-based unoriented film in which the dirt impact strength (mass 300g) measured in accordance with JIS K 7124-1 (1999) is 0.30 J or more, as described in the first or second invention.

[0014] The fifth invention relates to a polypropylene-based unoriented film in which the dirt impact strength (mass 300g) measured in accordance with JIS K 7124-1 (1999) is 0.30 J or more, as described in the third invention.

[0015] The sixth invention relates to a polypropylene non-stretched film having a heat seal start temperature of 140°C or lower measured in accordance with JIS Z 1713 (2009) in the fourth invention.

[0016] The seventh invention relates to a polypropylene non-stretched film having a heat seal start temperature of 140°C or lower measured in accordance with JIS Z 1713 (2009) in the fifth invention.

[0017] The eighth invention relates to a polypropylene non-stretched film having a haze value of 6% or lower measured in accordance with JIS K 7136 (2000) in the fourth invention.

[0018] The ninth invention relates to a polypropylene non-stretched film having a haze value of 6% or lower measured in accordance with JIS K 7136 (2000) in the fifth invention.

[0019] The tenth invention relates to a film laminate in which another resin film is laminated on the laminate layer of the polypropylene non-stretched film described in the first or second invention.

[0020] The eleventh invention relates to a film laminate in which another resin film is laminated on the laminate layer of the polypropylene non-stretched film described in the fourth invention.

[0021] The twelfth invention relates to a film laminate in which another resin film is laminated on the laminate layer of the polypropylene non-stretched film described in the fifth invention.

Advantages of the Invention

[0022] According to the polypropylene-based unstretched film according to the first invention, it is a polypropylene-based unstretched film laminated in the order of a laminate layer, a base material layer, and a sealant layer. The laminate layer is mainly composed of either a propylene-α-olefin random copolymer or a linear low-density polyethylene polyolefin resin. The base material layer consists of a composition of 50 to 95% by weight of a propylene-α-olefin random copolymer and 5 to 50% by weight of a propylene homopolymer having a crystallization temperature of 114°C or higher measured in accordance with JIS K 7121 (2012) using a differential scanning calorimeter (DSC). The sealant layer is composed of a propylene-α-olefin random copolymer. Among the heat of fusion of the polypropylene-based unstretched film measured in accordance with JIS K 7122 (2012) using a differential scanning calorimeter (DSC), the heat of fusion at a fractionation temperature of 150°C or higher is 2.5 to 40 J / g. Therefore, while suppressing an increase in manufacturing cost, it has transparency, low-temperature heat sealability, and heat seal strength suitable for use as a packaging material, and a film that achieves both rigidity and impact resistance can be obtained. Since the film has high rigidity, it can maintain a firm feeling even when thinned, thus contributing to reducing the environmental load.

[0023] According to the polypropylene-based unstretched film according to the second invention, in the first 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 1.55 GPa or more, it has high rigidity.

[0024] According to the polypropylene-based unstretched film according to the third invention, in the first or second invention, since the maximum heat seal strength in the heat seal temperature range of 130 to 160°C is 12.5 N / 15 mm or more, it has a heat seal strength suitable as a packaging material.

[0025] According to the polypropylene-based unstretched film according to the fourth invention, in the first or second invention, since the dart impact strength (mass 300 g) measured in accordance with JIS K 7124-1 (1999) is 0.30 J or more, it has high impact resistance.

[0026] According to the polypropylene-based unoriented film of the fifth invention, the dirt impact strength (mass 300g) measured in accordance with JIS K 7124-1 (1999) in the third invention is 0.30J or more, thus providing high impact resistance.

[0027] According to the polypropylene-based unoriented film of the sixth invention, in the fourth invention, the heat seal initiation temperature measured in accordance with JIS Z 1713 (2009) is 140°C or lower, thus providing suitable low-temperature heat sealability for use as a packaging material.

[0028] According to the polypropylene-based unoriented film of the seventh invention, in the fifth invention, the heat seal initiation temperature measured in accordance with JIS Z 1713 (2009) is 140°C or lower, thus providing suitable low-temperature heat sealability for use as a packaging material.

[0029] According to the polypropylene-based unoriented film of the eighth invention, the haze value measured in accordance with JIS K 7136 (2000) in the fourth invention is 6% or less, thus providing high transparency.

[0030] According to the polypropylene-based unoriented film of the ninth invention, the haze value measured in accordance with JIS K 7136 (2000) in the fifth invention is 6% or less, thus providing high transparency.

[0031] According to the tenth invention, since another resin film is laminated on the laminate layer of the polypropylene-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 polypropylene-based unoriented film without impairing its stiffness.

[0032] According to the film laminate of the 11th invention, since another resin film is laminated on the laminate layer of the polypropylene-based unoriented film described in the 4th invention, it can be suitably used as a film product such as a packaging film that reduces environmental impact by using a thinned polypropylene-based unoriented film without impairing its stiffness.

[0033] According to the film laminate of the 12th invention, since another resin film is laminated on the laminate layer of the polypropylene-based unoriented film described in the 5th invention, it can be suitably used as a film product such as a packaging film that reduces environmental impact by using a thinned polypropylene-based unoriented film without impairing its stiffness. [Brief explanation of the drawing]

[0034] [Figure 1] This graph shows the relationship between the film thickness and the maximum heat seal strength (130-160°C) of a polypropylene-based unoriented film according to one embodiment of the present invention. [Figure 2] This graph shows the relationship between film thickness and dirt impact strength (mass 300g) in a polypropylene-based unoriented film according to one embodiment of the present invention. [Modes for carrying out the invention]

[0035] An embodiment of the present invention is a polypropylene-based unoriented film, which is a laminated film comprising a laminate layer, a base layer, and a sealant layer in that order. "Unoriented" means a state in which no intentional stretching has been applied, and includes cases where unavoidable stretching occurs during film formation, etc. This polypropylene-based unoriented film is manufactured by a known film manufacturing method such as the T-die method.

[0036] The polypropylene-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 polypropylene-based unoriented film is suitably used, for example, as a packaging film or the like.

[0037] The base layer of the polypropylene-based unoriented film of the present invention has a composition consisting of 50 to 95% by weight of propylene-α-olefin random copolymer and 5 to 50% by weight of propylene homopolymer. If the base layer has a composition in which the proportion of propylene-α-olefin random copolymer exceeds 95% by weight and the proportion of propylene homopolymer is less than 5% by weight, the propylene-α-olefin random copolymer, which is a relatively low-melting-point component, becomes excessive, and the propylene homopolymer, which is a high-melting-point component, becomes insufficient, thereby reducing the rigidity and heat seal strength (more specifically, the maximum heat seal strength at a heat seal temperature of 130 to 160°C) of the film, as well as reducing its water vapor barrier properties. On the other hand, if the base layer has a composition in which the proportion of propylene-α-olefin random copolymer is less than 50% by weight and the proportion of propylene homopolymer exceeds 50% by weight, the propylene-α-olefin random copolymer, which is a relatively low-melting-point component, becomes insufficient, and the propylene homopolymer, which is a high-melting-point component, becomes excessive, thereby reducing the impact resistance of the film. A film can be obtained with a base layer composed of 50-95% by weight of propylene-α-olefin random copolymer and 5-50% by weight of propylene homopolymer, while maintaining rigidity and impact resistance, and possessing good heat seal strength and water vapor barrier properties.

[0038] 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.

[0039] 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. These copolymers may be used individually or as a mixture of two or more. It is preferable that the propylene-α-olefin random copolymer is selected from at least one of propylene-ethylene random copolymers or propylene-ethylene-butene random copolymers.

[0040] 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.

[0041] 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.

[0042] The propylene homopolymer used in the substrate layer of the polypropylene-based unoriented film must have a crystallization temperature of 114°C or higher, as measured by differential scanning calorimeter (DSC) in accordance with JIS K 7121 (2012). The propylene homopolymer meeting this condition may be used alone or in a mixture of two or more types. If the crystallization temperature of the propylene homopolymer used in the substrate layer is too low, crystallization will be slow, reducing the degree of crystallinity and potentially decreasing the rigidity and water vapor barrier properties of the film. If the crystallization temperature of the propylene homopolymer is 114°C or higher, crystallization will be rapid, resulting in smaller crystal sizes and improved crystallinity, thus achieving good rigidity and water vapor barrier properties.

[0043] In the polypropylene-based unoriented film of the present invention, recycled materials or biomass materials may be incorporated into the base layer to the extent that the objectives of the present invention are not impaired, in order to create an environmentally friendly product.

[0044] Recycled raw materials are resin materials obtained by processing polypropylene resin molded products, such as film molded products, scraps and surplus products generated during film production, and other resin products, into re-pelletized or other re-raw material products. These recycled raw materials also include resin molded products that contain residual materials that are different from the main raw material and are difficult to remove, such as resins of a different type than the main raw material, additives such as antistatic agents and antiblocking agents, and resins used in the masterbatch of these additives. Biomass raw materials are resin materials (biomass plastics) obtained by chemically or biologically synthesizing renewable organic resources of biological origin.

[0045] The laminate layer of the polypropylene-based unoriented film of the present invention is mainly composed of a polyolefin, either a propylene-α-olefin random copolymer or linear low-density polyethylene.

[0046] The propylene-α-olefin random copolymers usable in the laminate layer are the same as those usable in the substrate layer. For the laminate layer, one type of propylene-α-olefin random copolymer may be used alone, or two or more types of propylene-α-olefin random copolymers may be mixed and selected as appropriate depending on the film's application. Furthermore, the propylene-α-olefin random copolymer used in the laminate layer may be the same as, or different from, the propylene-α-olefin random copolymer used in the substrate layer.

[0047] 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 acceptable. 3 More preferably, 0.94 g / cm³ 3 More preferably, 0.93 g / cm³ 3 The following will be used.

[0048] The sealant layer of the polypropylene-based unoriented film of the present invention is made of a propylene-α-olefin random copolymer. The propylene-α-olefin random copolymer that can be used for the sealant layer is the same as the propylene-α-olefin random copolymer that can be used for the base layer. One type of propylene-α-olefin random copolymer may be used alone for the sealant layer, or two or more types of propylene-α-olefin random copolymers may be mixed and used, and can be appropriately selected according to the application of the film. Furthermore, the propylene-α-olefin random copolymer used for the sealant layer may be the same as or different from the propylene-α-olefin random copolymer used for the base layer or laminate layer.

[0049] The polypropylene-based unoriented film of the present invention requires that the amount of heat of fusion of the film measured by differential scanning calorimeter (DSC) in accordance with JIS K 7122 (2012) is 2.5 to 40 J / g at fractionation temperatures of 150°C or higher. If the amount of heat of fusion at fractionation temperatures of 150°C or higher is too low, the relatively high-melting-point component, propylene homopolymer, will be insufficient, which may result in insufficient rigidity, heat seal strength, and water vapor barrier properties of the film. On the other hand, if the amount of heat of fusion at fractionation temperatures of 150°C or higher is too high, the relatively high-melting-point component, propylene homopolymer, will be in excess, which may result in insufficient impact resistance of the film. By having a heat of fusion at fractionation temperatures of 150°C or higher of 2.5 to 40 J / g, a film can be obtained that achieves both rigidity and impact resistance, as well as good heat seal strength and water vapor barrier properties.

[0050] The polypropylene-based unoriented film of the present invention preferably has a sum of tensile modulus in the longitudinal (MD) direction and transverse (TD) direction of 1.55 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). A higher tensile modulus value indicates that the film has higher rigidity and a stronger stiffness. By having a sum of tensile modulus in the longitudinal (MD) direction and transverse (TD) direction of 1.55 GPa or higher, sufficient stiffness 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 stiffness 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.

[0051] The polypropylene-based unoriented film of the present invention preferably has a Dirt impact strength (hereinafter also referred to as "Dirt impact strength (300g mass)") of 0.30 J or higher, as 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). A higher Dirt impact strength value indicates that the film has higher impact resistance. If the Dirt impact strength (300g mass) is 0.30 J or higher, good impact resistance suitable for various applications such as packaging films can be obtained. If the Dirt impact strength of the polypropylene-based unoriented film is too low, it may have poor impact resistance and there is a high possibility that it will tear when subjected to impact.

[0052] The polypropylene-based unoriented film of the present invention preferably has a maximum heat seal strength of 12.5 N / 15 mm or higher at a heat seal temperature range of 130 to 160°C, as required for various applications such as packaging films. If the maximum heat seal strength is too low, there is a high possibility that the sealed portion will peel off due to external force. If the maximum heat seal strength at a heat seal temperature range of 130 to 160°C (hereinafter also referred to as "maximum heat seal strength (130 to 160°C)") is 12.5 N / 15 mm or higher, the film can be given good heat seal strength.

[0053] The polypropylene-based unoriented film of the present invention preferably has a heat seal initiation temperature of 140°C or lower, which is a physical property required for various applications such as packaging films. The heat seal initiation temperature is a value measured in accordance with JIS Z 1713 (2009). If the heat seal initiation temperature is too high, it becomes necessary to raise the heat sealing conditions to a higher temperature, which can easily hinder productivity. If the heat seal initiation temperature is 140°C or lower, the film can be given good low-temperature heat sealability.

[0054] The polypropylene-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 6% 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.

[0055] In the polypropylene-based unoriented film of the present invention, additives are added as needed, to the extent that the objectives of the present invention are not impaired. Examples of additives include antioxidants, neutralizing agents, antistatic agents, antifogging agents, lubricants, nucleating agents, and colorants.

[0056] The thickness of the polypropylene unoriented film is not particularly limited and can be set appropriately depending on the application. 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 polypropylene unoriented film (layer ratio) can be determined appropriately depending on the application. In the polypropylene unoriented film, the ratios of the laminate layer, substrate layer, and sealant layer in the total layers are, for example, preferably 10 to 33.3%, 33.4% to 80%, and 10 to 33.3%. In other words, the layer ratio of laminate layer:substrate layer:sealant layer is, for example, preferably 1:8:1 to 1:1:1.

[0057] In the polypropylene-based unoriented film of the present invention, it is preferable that the laminate layer is surface-treated to have a wetting tension of 36 mN / m or more in order to broaden its range of applications as a sealant film, etc. 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.

[0058] As described above, the polypropylene-based unoriented film of the present invention is a film comprising a laminate layer, a base layer, and a sealant layer in that order, wherein the laminate layer mainly consists of a polyolefin resin, either a propylene-α-olefin random copolymer or linear low-density polyethylene, the base layer has a composition of 50-95% by weight of a propylene-α-olefin random copolymer and 5-50% by weight of a propylene homopolymer whose crystallization temperature, as measured by differential scanning calorimeter (DSC) in accordance with JIS K 7121 (2012), is 114°C or higher, and the sealant layer consists of a propylene-α-olefin random copolymer, and the heat of fusion of the polypropylene-based unoriented film, as measured by differential scanning calorimeter (DSC) in accordance with JIS K 7122 (2012), is characterized in that the heat of fusion at a fractionation temperature of 150°C or higher is 2.5-40 J / g. The polypropylene-based unoriented film of the present invention, which satisfies the above conditions, possesses transparency, low-temperature heat sealability, and heat seal strength suitable for use as packaging materials, while suppressing manufacturing costs, and also achieves both rigidity and impact resistance. Because the polypropylene-based unoriented film 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, and thus can greatly contribute to reducing the environmental burden. Furthermore, the polyolefin-based unoriented film of the present invention can be subjected to vapor deposition treatment or printing.

[0059] In the polypropylene-based unoriented film of the present invention, a film laminate can be formed by laminating another resin film onto the laminate layer 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 of the present invention, 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.

[0060] The resulting film laminate possesses high rigidity in the polypropylene-based unstretched 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]

[0061] [Preparation of polypropylene-based unstretched film] In the production of the polypropylene-based unoriented films for prototype examples 1 to 29, 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, the laminate layer was subjected to corona discharge treatment to produce the polypropylene-based unoriented film.

[0062] The thickness of each fabricated film was measured in accordance with JIS K 7130 (1999). The thickness ratio of each layer in the polypropylene unoriented film, consisting of a laminate layer, a base layer, and a sealant layer, was adjusted by the discharge rate from the T-die. The thickness obtained from measuring the molded film was then apportioned according to the set ratio to determine the layer ratio. The mixing ratios of the resin materials used in each layer of prototype examples 1 to 29 are shown in Tables 1 to 4 below.

[0063] [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 (G-01, manufactured by Toyo Seiki Seisakusho Co., Ltd.). Except for linear low-density polyethylene (LLDPE), the measurements were taken at a test temperature of 230°C, while the LLDPE measurement was taken at a test temperature of 190°C.

[0064] 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).

[0065] <Propylene-α-olefin random copolymer> • Binary RCP: Propylene-ethylene random copolymer (MFR 7g / 10min, crystallization temperature 102℃, melting point 135℃) • Ternary RCP: Propylene-ethylene-butene random copolymer (MFR 7g / 10min, crystallization temperature 96℃, melting point 140℃)

[0066] <Propylene homopolymer> • H-PP1: Propylene homopolymer (MFR 7.5g / 10min, crystallization temperature 114℃, melting point 166℃) • H-PP2: Propylene homopolymer (MFR 3g / 10min, crystallization temperature 117℃, melting point 159℃) • H-PP3: Propylene homopolymer (MFR 4.2g / 10min, crystallization temperature 118℃, melting point 167℃) • H-PP4: Propylene homopolymer (MFR 8g / 10min, crystallization temperature 121℃, melting point 165℃) • H-PP5: Propylene homopolymer (MFR 7g / 10min, crystallization temperature 110℃, melting point 162℃) • H-PP6: Propylene homopolymer (MFR 3g / 10min, crystallization temperature 112℃, melting point 165℃)

[0067] <Linear low-density polyethylene> • LLDPE: Linear low-density polyethylene (MFR 4g / 10min, crystallization temperature 102℃, melting point 116℃)

[0068] <Recycled materials> Recycled material: MFR 10.1g / 10min, crystallization temperature 102℃, melting point 140℃

[0069] [Prototype Example 1] Prototype Example 1 is a film obtained by blending 100% by weight of binary RCP, a propylene-α-olefin random copolymer, as the laminate layer, 100% by weight of binary RCP as the base layer, and 100% by weight of binary RCP as the sealant layer, with a layer ratio of laminate layer:base layer:sealant layer of 1:4:1 and a thickness of 30 μm.

[0070] [Prototype Example 2] Prototype Example 2 is a film obtained by forming a film with the same composition as Prototype Example 1, except that the base layer composition consisted of 98% by weight of binary RCP, which is a propylene-α-olefin random copolymer, and 2% by weight of H-PP1, which is a propylene homopolymer.

[0071] [Prototype Example 3] Prototype Example 3 is a film obtained by forming a film with the same composition as Prototype Example 1, except that the base layer composition was 95% by weight of binary RCP and 5% by weight of H-PP1.

[0072] [Prototype Example 4] Prototype Example 4 is a film obtained by fabricating a film with the same composition as Prototype Example 1, except that the base layer composition was 90% by weight of binary RCP and 10% by weight of H-PP1, and the film thickness was 20 μm.

[0073] [Prototype Example 5] Prototype Example 5 is a film obtained by fabricating a film identical to that of Prototype Example 4, except that the film thickness was set to 30 μm.

[0074] [Prototype Example 6] Prototype Example 6 is a film obtained by fabricating a film identical to that of Prototype Example 4, except that the film thickness was set to 40 μm.

[0075] [Prototype Example 7] Prototype Example 7 is a film obtained by fabricating a film identical to that of Prototype Example 4, except that the film thickness was set to 60 μm.

[0076] [Prototype Example 8] Prototype Example 8 is a film obtained by fabricating a film with the same composition as Prototype Example 1, except that the base layer composition was 70% by weight of binary RCP and 30% by weight of H-PP1, and the film thickness was 20 μm.

[0077] [Prototype Example 9] Prototype Example 9 is a film obtained by fabricating a film identical to that of Prototype Example 8, except that the film thickness was set to 30 μm.

[0078] [Prototype Example 10] Prototype 10 is a film obtained by fabricating a film identical to that of prototype 8, except that the film thickness was set to 40 μm.

[0079] [Prototype Example 11] Prototype 11 is a film obtained by fabricating a film identical to that of Prototype 8, except that the film thickness was set to 60 μm.

[0080] [Prototype Example 12] Prototype Example 12 is a film obtained by forming a film with the same composition as Prototype Example 1, except that the base layer composition was 60% by weight of binary RCP and 40% by weight of H-PP1.

[0081] [Prototype Example 13] Prototype 13 is a film obtained by manufacturing a film identical to that of prototype 12, except that the layer ratio of the laminate layer:substrate layer:sealant layer was set to 1:6:1.

[0082] [Prototype Example 14] Prototype 14 is a film obtained by manufacturing a film identical to that of prototype 12, except that the layer ratio of the laminate layer:substrate layer:sealant layer was set to 1:8:1.

[0083] [Prototype Example 15] Prototype Example 15 is a film obtained by forming a film with the same composition as Prototype Example 1, except that the base layer composition was 50% by weight of binary RCP and 50% by weight of H-PP1.

[0084] [Prototype Example 16] Prototype Example 16 is a film obtained by forming a film with the same composition as Prototype Example 1, except that the base layer composition was 30% by weight of binary RCP and 70% by weight of H-PP1.

[0085] [Prototype Example 17] Prototype 17 is a film obtained by forming a film using the same method as Prototype 1, except that 100% by weight of H-PP1, a propylene homopolymer, was incorporated as the base layer.

[0086] [Prototype Example 18] Prototype Example 18 is a film obtained by forming a film with the same composition as Prototype Example 1, except that the base layer composition consisted of 50% by weight of binary RCP, which is a propylene-α-olefin random copolymer, 20% by weight of ternary RCP, which is also a propylene-α-olefin random copolymer, and 30% by weight of H-PP1, which is a propylene homopolymer.

[0087] [Prototype Example 19] Prototype Example 19 is a film obtained by forming a film with the same composition as Prototype Example 1, except that the laminate layer composition consisted of 60% by weight of binary RCP, which is a propylene-α-olefin random copolymer, and 40% by weight of H-PP1, which is a propylene homopolymer.

[0088] [Prototype Example 20] Prototype Example 20 is a film obtained by forming a film with the same composition as Prototype Example 19, except that the base layer composition consisted of 60% by weight of binary RCP, which is a propylene-α-olefin random copolymer, and 40% by weight of H-PP1, which is a propylene homopolymer.

[0089] [Prototype Example 21] Prototype Example 21 is a film obtained by forming a film with the same composition as Prototype Example 19, except that the base layer composition consisted of 80% by weight of binary RCP, which is a propylene-α-olefin random copolymer, and 20% by weight of H-PP1, which is a propylene homopolymer.

[0090] [Prototype Example 22] Prototype 22 is a film obtained by forming a film with the same composition as Prototype 1, except that the laminate layer composition consists of 45% by weight of binary RCP, a propylene-α-olefin random copolymer, and 55% by weight of linear low-density polyethylene (LLDPE), and the base layer composition consists of 50% by weight of binary RCP and 50% by weight of H-PP1, a propylene homopolymer.

[0091] [Prototype Example 23] Prototype Example 23 is a film obtained by forming a film with the same composition as Prototype Example 1, except that the base layer composition consists of 50% by weight of binary RCP, which is a propylene-α-olefin random copolymer, 30% by weight of H-PP1, which is a propylene homopolymer, and 20% by weight of recycled materials.

[0092] [Prototype Example 24] Prototype Example 24 is a film obtained by forming a film with the same composition as Prototype Example 1, except that the propylene-α-olefin random copolymer in the laminate layer and sealant layer was changed from binary RCP to ternary RCP, and the composition of the base layer was set to 50% by weight of binary RCP, which is a propylene-α-olefin random copolymer, and 50% by weight of H-PP1, which is a propylene homopolymer.

[0093] [Prototype Example 25] Prototype Example 25 is a film obtained by fabricating a film identical to that of Prototype Example 24, except that the propylene homopolymer in the substrate layer was changed from H-PP1 to H-PP2.

[0094] [Prototype Example 26] Prototype 26 is a film obtained by forming a film using the same method as prototype 24, except that the propylene homopolymer in the substrate layer was changed from H-PP1 to H-PP3.

[0095] [Prototype Example 27] Prototype 27 is a film obtained by fabricating a film identical to that of prototype 24, except that the propylene homopolymer in the substrate layer was changed from H-PP1 to H-PP4.

[0096] [Prototype Example 28] Prototype 28 is a film obtained by forming a film using the same method as prototype 24, except that the propylene homopolymer in the substrate layer was changed from H-PP1 to H-PP5.

[0097] [Prototype Example 29] Prototype example 29 is a film obtained by forming a film using the same method as prototype example 24, except that the propylene homopolymer in the substrate layer was changed from H-PP1 to H-PP6.

[0098] [Table 1]

[0099] [Table 2]

[0100] [Table 3]

[0101] [Table 4]

[0102] The performance of the polypropylene-based unoriented films of prototypes 1 to 29 was evaluated as follows: haze, tensile modulus, dart impact strength (300g mass), heat seal initiation temperature, maximum heat seal strength (130-160°C), water vapor permeability, and heat of fusion. The results and evaluations of each test are shown in Tables 5 to 8 below.

[0103] [Haze value] For prototypes 1-29 of polypropylene-based unoriented films, the haze (%), an indicator of transparency, was measured based on a test method conforming to JIS K 7136 (2000). A haze meter (NDH-8000, manufactured by Nippon Denshoku Industries Co., Ltd.) was used to measure the haze. For transparency required for packaging films, the measured haze value was evaluated as "Good (〇)" if it was 6% or less, and as "Unacceptable (×)" if it exceeded 6%.

[0104] [Tensile modulus of elasticity] For the polypropylene unoriented films of prototype examples 1 to 29, the tensile modulus (GPa), an indicator of film stiffness, was measured based on the test method for plastic tensile properties conforming to JIS K 7127 (1999). A tensile testing machine (A&D Co., Ltd., "Tensilon Universal Material Tester RTF-1310") was used, and measurements were taken in two directions: the longitudinal direction (MD), which is the winding direction of the film, and the transverse direction (TD), which is perpendicular to it. The sum of the tensile moduli in the MD and TD directions was also calculated. As a measure of the stiffness required for packaging films, a sum of the obtained tensile moduli in the MD and TD directions of 1.55 GPa or higher was evaluated as "Good (〇)", and a sum of less than 1.55 GPa was evaluated as "Unacceptable (×)".

[0105] [Dirt impact strength (mass 300g)] For prototypes 1-29 of polypropylene-based unoriented films, the dart impact strength (J), an indicator of penetration failure, was measured based on a test method conforming to JIS K 7124-1 (1999). Using a dart impact tester with a low-temperature chamber (manufactured by Toyo Seiki Seisakusho Co., Ltd.), each prototype film was fixed horizontally with a fixing device, and a dart with adjusted mass (mass: 300g, hemispherical metal penetration part: diameter 25.4mm) was dropped to break and penetrate the film, and the fracture energy (J) was determined. From the viewpoint of impact resistance required for packaging films, films with a film thickness of 30 μm or more were evaluated as "Good (〇)" if the measured dart impact strength (mass 300g) was 0.30 J or higher, and as "Unacceptable (×)" if it was less than 0.30 J. In Tables 5-8, prototypes with a film thickness of less than 30 μm that were not subject to evaluation are indicated with "-".

[0106] [Heat sealing start temperature] For the polypropylene-based unoriented films of prototype examples 1 to 29, the heat seal start temperature (°C), an indicator of adhesive suitability, was measured based on a test method conforming to JIS Z 1713 (2009). Two copies of each prototype film were prepared, and the sealant layers of each were stacked. Using a heat seal tester (Toyo Seiki Seisakusho Co., Ltd., "Thermal Gradient Tester"), the seal bar shape was set to 10 mm x 25 mm, the seal pressure to 0.4 MPa, and the seal time to 1 sec. Heat sealing was performed under conditions where the temperature was gradually increased by 5°C increments. After heat sealing, a 15 mm wide test piece was cut out. The heat-sealed test piece was opened to 180°, and the sealed portion was peeled off using a tensile tester (Shimadzu Corporation; "EZ-SX") at a tensile speed of 200 mm / min. The temperature at which the heat seal strength reached 3 N / 15 mm width (heat seal temperature) was then determined. The measured heat seal start temperature was evaluated as "Good (〇)" if it was 140°C or lower, and as "Unacceptable (×)" if it exceeded 140°C.

[0107] [Maximum heat seal strength (130~160℃)] For the polypropylene-based unoriented films of prototype examples 1 to 29, the maximum heat seal strength (130-160°C) (N / 15mm), an indicator of adhesive suitability, was measured. For each prototype film, a 15mm wide test piece was prepared using a heat seal tester (Toyo Seiki Seisakusho Co., Ltd., "Thermal Gradient Tester"), in the same manner as the "Heat Seal Start Temperature" described above. At this time, a sealing pressure of 0.4 MPa and a sealing time of 1 sec were used, and heat sealing was performed in the heat seal temperature range of 130-160°C. For the test pieces obtained in the heat seal temperature range of 130-160°C, the heat seal strength (N / 15mm) was measured using a tensile tester (Shimadzu Corporation; "EZ-SX") at a tensile speed of 200 mm / min. The maximum value was determined from the heat seal strength in the heat seal temperature range of 130-160°C, and this value was defined as the maximum heat seal strength (130-160°C) (N / 15mm). For films with a thickness of 30 μm or more, a maximum heat seal strength of 12.5 N / 15 mm or higher was evaluated as "Good (〇)", and a strength less than 12.5 N / 15 mm was evaluated as "Unacceptable (×)". In Tables 5 to 8, prototype examples with a film thickness of less than 30 μm that were not subject to evaluation were indicated with "-".

[0108] [Water vapor transmission rate] For prototype examples 1-3, 5, 8-11, 14-16, 18-20, 24, 25, and 28 of polypropylene-based unoriented films, the water vapor transmission rate (g / m³), an indicator of water vapor barrier properties, was measured based on the test method conforming to JIS K 7129 (2008). 2 The water vapor transmission rate (day) was measured. A water vapor transmission rate measuring device (MOCON, "PERMATRAN-W(registered trademark) 3 / 33") was used, and measurements were taken at a temperature of 40°C and a relative humidity (RH) of 90%. The measured water vapor transmission rate for films with a thickness of 30 μm or more was 13.7 g / m². 2 • If it is less than or equal to day, it is marked as "Good (〇)", 13.7g / m² 2 If the time exceeded one day, it was evaluated as "Not acceptable (×)". In Tables 5 to 8, prototypes where water vapor transmission was not measured, and prototypes with a film thickness of less than 30 μm that were not subject to evaluation are indicated with "-".

[0109] [Of the heat of fusion of the film, the heat of fusion at fractionation temperatures of 150°C or higher] For prototype examples 1 to 29, the heat of fusion (J / g) of the polypropylene unoriented films was measured based on a test method conforming to JIS K 7122 (2012). A differential scanning calorimeter (NETZSCH, "DSC214 Polyma") was used for the measurements. For each prototype film, the heat of fusion at fractionation temperatures of 150°C or higher (i.e., the heat of fusion at 150°C or higher when fractionated at 150°C) was determined from the heat of fusion obtained by the above measurement (heat of fusion in the entire range). For each prototype film, if the heat of fusion at fractionation temperatures of 150°C or higher was within the range of 2.5 to 40 J / g, it was evaluated as "Good (〇)", and if it was outside this range, it was evaluated as "Unacceptable (×)".

[0110] [Table 5]

[0111] [Table 6]

[0112] [Table 7]

[0113] [Table 8]

[0114] [Results and Discussion] <Base material layer> First, we will investigate the preferred blending ratio of propylene-α-olefin random copolymer and propylene homopolymer in the base layer of the film (polypropylene-based unoriented film). Examples 1-3, 5, 9, 12, and 15-17 are films with the same composition except for the different blending ratios of binary RCP, which is a propylene-α-olefin random copolymer, and H-PP1, which is a propylene homopolymer, in the base layer.

[0115] Of these prototypes, films 1, 2, 16, and 17 did not achieve sufficient film performance. Specifically, in film 1, the sum of the tensile modulus in the MD and TD directions was less than 1.55 GPa, indicating insufficient rigidity. Films 1 and 2 both exhibited insufficient heat seal strength (130-160°C), and film 1 also showed insufficient water vapor barrier properties. Films 16 and 17 did not achieve sufficient impact resistance.

[0116] In prototypes 1 and 2, the proportion of propylene homopolymer in the base layer was too low (0% or 2%), and the proportion of propylene-α-olefin random copolymer was too high. In prototypes 16 and 17, the proportion of propylene homopolymer in the base layer was too high (70% or 100%), and the proportion of propylene-α-olefin random copolymer was too low. Therefore, from prototypes 3, 5, 9, 12, and 15, which yielded good results, it is considered that a desirable film can be obtained when the base layer consists of a composition of 50-95% by weight of propylene-α-olefin random copolymer and 5-50% by weight of propylene homopolymer, while maintaining both rigidity and impact resistance, as well as good transparency, low-temperature heat sealability, heat seal strength (more specifically, maximum heat seal strength (130-160°C)), and water vapor barrier properties.

[0117] Prototype Example 18 is a film in which the propylene-α-olefin random copolymer blended into the base layer is a mixture of binary RCP and ternary RCP. The film of Prototype Example 18 has a base layer composition of 70% by weight of propylene-α-olefin random copolymer (binary RCP and ternary RCP) and 30% by weight of propylene homopolymer. Since good results were obtained for Prototype Example 18, it is considered that if the propylene-α-olefin random copolymer and propylene homopolymer in the base layer satisfy the above-mentioned preferred blending ratio, good rigidity, impact resistance, transparency, low-temperature heat sealability, heat seal strength, and water vapor barrier properties can be obtained even if the propylene-α-olefin random copolymer in the base layer is not limited to binary RCP alone, but is a mixture of binary RCP and ternary RCP.

[0118] Prototype 24 is a film constructed identically to Prototype 15, except that the propylene-α-olefin random copolymer constituting the surface laminate layer and sealant layer is a ternary RCP. Similar to the film in Prototype 15, the film of Prototype 24 contains propylene-α-olefin random copolymer and propylene homopolymer blended in the base layer in the preferred proportions described above. Since Prototype 24 yielded good results, it is considered that when the propylene-α-olefin random copolymer and propylene homopolymer in the base layer satisfy the preferred proportions described above, good rigidity, impact resistance, transparency, low-temperature heat sealability, heat seal strength, and water vapor barrier properties can be obtained, regardless of whether the surface layer (laminated layer and sealant layer) is a binary RCP or a ternary RCP.

[0119] Prototype 23 is a film in which recycled materials are incorporated into the base layer while maintaining the above-mentioned preferred blending ratio of propylene-α-olefin random copolymer and propylene homopolymer in the base layer. Since good results were obtained with prototype 23, it is considered that good rigidity, impact resistance, transparency, low-temperature heat sealability, and heat seal strength can be obtained even when a small amount of recycled materials are added to the base layer, provided that the above-mentioned preferred blending ratio of propylene-α-olefin random copolymer and propylene homopolymer in the base layer is met.

[0120] <Propylene homopolymer incorporated into the base layer> Prototypes 24-29 are films with the same composition except for the type of propylene homopolymer used in the substrate layer. Of these prototypes, films 28 and 29 did not achieve sufficient film performance. Therefore, it is considered that the propylene homopolymers (H-PP5, H-PP6) used in the substrate layer of prototypes 28 and 29 are unsuitable as propylene homopolymers for obtaining good rigidity, impact resistance, transparency, low-temperature heat sealability, heat seal strength, and water vapor barrier properties.

[0121] From a comparison of the physical properties of the propylene homopolymers (H-PP1 to H-PP4) used in prototype examples 24 to 27, which showed good film performance, and the physical properties of the propylene homopolymers (H-PP5 and H-PP6) used in prototype examples 28 and 29, it is considered that the preferred physical properties of a propylene homopolymer are such that the crystallization temperature measured by differential scanning calorimeter (DSC) is 114°C or higher.

[0122] <Of the heat of fusion of the film, the heat of fusion at fractionation temperatures of 150°C or higher> Of the prototypes 1-3, 5, 9, 12, 15-17, prototypes 3, 5, 9, 12, and 15 demonstrated good film performance. On the other hand, the films of prototypes 1, 2, 16, and 17 received a "failure (×)" rating in at least one of the following evaluations: rigidity, impact resistance, maximum heat seal strength (130-160°C), and water vapor barrier properties. From the comparison between prototypes 3, 5, 9, 12, and 15 and prototypes 1, 2, 16, and 17, it is considered that a film with both rigidity and impact resistance, as well as good heat seal strength and water vapor barrier properties, can be obtained when the heat of fusion amount of the film at fractionation temperatures above 150°C is between 2.5 and 40 J / g. Furthermore, based on the results of prototype examples 3, 5, 9, 12, and 15, it is considered that films with a melting heat of 2.5 to 40 J / g at a fractionation temperature of 150°C or higher possess good transparency and low-temperature heat-sealability in addition to the above-mentioned performance.

[0123] <Laminate layer> Prototype 19 is a film identical in composition to Prototype 1, except that the laminate layer consists of a composition containing 60% by weight of propylene-α-olefin random copolymer (binary RCP) and 40% by weight of propylene homopolymer (H-PP1). The film of Prototype 19, like the film of Prototype 1, did not achieve sufficient film performance. Therefore, it is considered that in films where the proportion of propylene-α-olefin random copolymer in the substrate layer is excessive (i.e., the proportion of propylene homopolymer is insufficient), good film performance cannot be obtained even if propylene homopolymer is incorporated into the laminate layer. Comparing Prototype 1 and Prototype 19, when propylene homopolymer was incorporated into the laminate layer, the maximum heat seal strength (130~160°C) and water vapor barrier properties improved, but a decrease in rigidity was observed.

[0124] Prototypes 20 and 21, like prototype 19, are films in which the laminate layer has a composition containing 60% by weight of propylene-α-olefin random copolymer (binary RCP) and 40% by weight of propylene homopolymer (H-PP1). The films of prototypes 20 and 21 showed good film performance. Since the propylene-α-olefin random copolymer and propylene homopolymer in the substrate layer of prototypes 20 and 21 were in the above-mentioned preferred blending ratio, it is considered that even if the laminate layer that forms the surface of such a substrate layer consists mainly of propylene-α-olefin random copolymer, or a mixture of propylene-α-olefin random copolymer and propylene homopolymer, good rigidity, impact resistance, transparency, low-temperature heat sealability, heat seal strength, and water vapor barrier properties can be obtained.

[0125] Prototype Example 22 is a film in which the laminate layer has a composition containing 45% by weight of propylene-α-olefin random copolymer (binary RCP) and 55% by weight of linear low-density polyethylene (LLDPE). In other words, in Prototype Example 22, the main raw material of the laminate layer is linear low-density polyethylene, not propylene-α-olefin random copolymer. The film of Prototype Example 22 showed good film performance. Since the propylene-α-olefin random copolymer and propylene homopolymer in the base layer of the film of Prototype Example 22 were in the above-mentioned preferred blending ratio, it is considered that good rigidity, impact resistance, transparency, low-temperature heat sealability, and heat seal strength can be obtained even when the main component of the laminate layer that forms the surface of such a base layer is linear low-density polyethylene, not propylene-α-olefin random copolymer.

[0126] <Layer ratio> Prototypes 12, 13, and 14 are all films with the same composition except for the difference in layer ratio (laminate layer: substrate layer: sealant layer). Since good film performance was obtained for all of the films in prototypes 12, 13, and 14, it is considered that if the laminate layer, substrate layer, and sealant layer meet the specified conditions, changing the layer ratio will not cause a significant change in film performance.

[0127] <Maximum heat seal strength (130~160℃)> Based on the results obtained for prototypes 4-7 and 8-11, we will discuss the relationship between film thickness and maximum heat seal strength (130-160°C). Prototypes 4-7 are all films in which the proportion of propylene homopolymer in the base layer is 10%, and the thickness of the films (polypropylene unoriented films) differs for each. Prototypes 8-11 are all films in which the proportion of propylene homopolymer in the base layer is 30%, and the thickness of the films differs for each.

[0128] Figure 1 is a graph showing the relationship between the film thickness and the maximum heat seal strength (130-160°C) of the polypropylene-based unoriented film of the present invention. In the graph of Figure 1, the maximum heat seal strength (130-160°C) is on the vertical axis and the film thickness is on the horizontal axis. In the graph, black circles (●) indicate the case where the blending ratio of propylene homopolymer (H-PP) is 10% (Prototype Examples 4-7), and white triangles (△) indicate the case where the blending ratio is 30% (Prototype Examples 8-11).

[0129] As shown in Figure 1, the coefficient of determination (R) is the same for both 10% and 30% propylene homopolymer content, in relation to the film thickness and the maximum heat seal strength (130-160°C). 2 The ratio was 0.99 or higher, indicating a significant correlation. Thus, in the polypropylene-based unoriented film of the present invention, it was confirmed that the maximum heat seal strength (130-160°C) tends to increase as the film thickness increases.

[0130] <Dirt Impact Strength> Based on the results obtained for prototypes 4-7 and 8-11, we will consider the relationship between film thickness and dirt impact strength (mass 300g). Figure 2 is a graph showing the relationship between film thickness and dirt impact strength (mass 300g) in the polypropylene-based unoriented film of the present invention. In the graph of Figure 2, dirt impact strength (mass 300g) is on the vertical axis and film thickness is on the horizontal axis. In the graph, black circles (●) indicate the case where the blending ratio of propylene homopolymer (H-PP) is 10% (prototypes 4-7), and white triangles (△) indicate the case where the blending ratio is 30% (prototypes 8-11).

[0131] As shown in Figure 2, the coefficient of determination (R) is the same for both 10% and 30% of the propylene homopolymer blending ratio, in relation to the film thickness and dirt impact strength (mass 300g). 2 The ratio was 0.96 or higher, indicating a significant correlation. Thus, in the polypropylene-based unoriented film of the present invention, it was confirmed that the dirt impact strength (mass 300g) tended to increase as the film thickness increased.

[0132] <Water vapor transmission rate> Comparing the water vapor permeability in prototype examples 1, 2, 3, 5, and 9.15, a tendency was observed for water vapor permeability to decrease (i.e., water vapor barrier properties to improve) as the proportion of propylene homopolymer in the substrate layer increased. Furthermore, a difference in water vapor permeability was observed depending on whether the propylene-α-olefin random copolymer used in the substrate layer was a binary RCP (propylene-ethylene random copolymer) or a ternary RCP (propylene-ethylene-butene random copolymer), with binary RCPs tending to exhibit lower water vapor permeability compared to ternary RCPs.

[0133] Based on the evaluation of each prototype example above, it was shown that in a polypropylene-based unoriented film laminated in the order of a laminate layer, a base layer, and a sealant layer, the laminate layer mainly consists of a polyolefin resin selected from at least one of propylene-α-olefin random copolymer or linear low-density polyethylene; the base layer consists of 50-95% by weight of propylene-α-olefin random copolymer and 5-50% by weight of propylene homopolymer with a crystallization temperature of 114°C or higher, as measured by differential scanning calorimeter (DSC) in accordance with JIS K 7121 (2012); and the sealant layer consists of propylene-α-olefin random copolymer, and it is preferable that the heat of fusion of the polypropylene-based unoriented film measured by differential scanning calorimeter (DSC) in accordance with JIS K 7122 (2012) is 2.5-40 J / g at a fractionation temperature of 150°C or higher. Such polypropylene-based unoriented films have been shown to exhibit excellent rigidity, impact resistance, transparency, low-temperature heat sealability, heat seal strength, and water vapor barrier properties. [Industrial applicability]

[0134] In the polypropylene-based unoriented film of the present invention, the laminate layer is mainly composed of a polyolefin resin, either a propylene-α-olefin random copolymer or linear low-density polyethylene; the base layer is composed of a propylene-α-olefin random copolymer and a propylene homopolymer having a predetermined crystallization temperature in a predetermined proportion; and the sealant layer is made of a propylene-α-olefin random copolymer. When the amount of heat of fusion of the film at a fractionation temperature of 150°C or higher satisfies predetermined conditions, the film achieves transparency, low-temperature heat sealability, and heat seal strength suitable for use as a packaging material, while simultaneously achieving rigidity and impact resistance, all while suppressing an increase in manufacturing costs. Therefore, it is possible to provide a polypropylene-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 polypropylene-based unoriented films and their film laminates.

Claims

1. A polypropylene-based unoriented film comprising a laminate layer, a substrate layer, and a sealant layer in that order, The laminate layer mainly consists of a polyolefin resin, either a propylene-α-olefin random copolymer or linear low-density polyethylene. The aforementioned substrate layer is 50-95% by weight of propylene-α-olefin random copolymer, The composition consists of 5 to 50% by weight of a propylene homopolymer whose crystallization temperature, as measured by differential scanning calorimeter (DSC) in accordance with JIS K 7121 (2012), is 114°C or higher. The sealant layer is made of a propylene-α-olefin random copolymer. Of the heat of fusion of the aforementioned polypropylene-based unoriented film, measured using a differential scanning calorimeter (DSC) in accordance with JIS K 7122 (2012), the heat of fusion at fractionation temperatures of 150°C or higher is 2.5 to 40 J / g. A polypropylene-based unoriented film characterized by the following features.

2. The polypropylene-based unoriented film according to claim 1, 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 1.55 GPa or more.

3. The polypropylene-based unoriented film according to claim 1 or 2, wherein the maximum heat seal strength in the heat seal temperature range of 130 to 160°C is 12.5 N / 15 mm or more.

4. The polypropylene-based unoriented film according to claim 1 or 2, wherein the dirt impact strength (mass 300g) measured in accordance with JIS K 7124-1 (1999) is 0.30 J or more.

5. The polypropylene-based unoriented film according to claim 3, wherein the dirt impact strength (mass 300g) measured in accordance with JIS K 7124-1 (1999) is 0.30 J or more.

6. The polypropylene-based unoriented film according to claim 4, wherein the heat seal initiation temperature measured in accordance with JIS Z 1713 (2009) is 140°C or less.

7. The polypropylene-based unoriented film according to claim 5, wherein the heat seal initiation temperature measured in accordance with JIS Z 1713 (2009) is 140°C or less.

8. The polypropylene-based unoriented film according to claim 4, wherein the haze value measured in accordance with JIS K 7136 (2000) is 6% or less.

9. The polypropylene-based unoriented film according to claim 5, wherein the haze value measured in accordance with JIS K 7136 (2000) is 6% or less.

10. A film laminate comprising a laminate layer of a polypropylene-based unoriented film according to claim 1 or 2, on which another resin film is laminated.

11. A film laminate comprising a laminate layer of a polypropylene-based unoriented film according to claim 4, on which another resin film is laminated.

12. A film laminate comprising a laminate layer of a polypropylene-based unoriented film according to claim 5, on which another resin film is laminated.

Images