Unstretched polypropylene-based film

Abstract

To provide an unstretched polypropylene-based film capable of securing good water vapor barrier properties without relying on lamination or coating, and suppressing deterioration of water vapor barrier properties of a film that has been thinned by volume reduction.SOLUTION: An unstretched film body mainly comprises a polypropylene resin, comprising at least three or more layers of a surface layer 20, a base layer 30, and a sealant layer 40, wherein the surface layer 20, the base layer 30, and the sealant layer 40 are laminated in this order, and the base layer 30 comprises 2.0% or more of an alicyclic hydrocarbon resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an unstretched polypropylene film. [Background technology]

[0002] Among resin films for packaging, polypropylene-based films are extremely useful as packaging materials due to their excellent heat resistance, chemical resistance, heat sealing properties, etc. Among these polypropylene-based films, unstretched films and uniaxially or biaxially stretched films are appropriately selected depending on the application, etc. For example, unstretched polypropylene-based films are preferably used as packaging materials (packaging bags) for food products.

[0003] In recent years, with the promotion of Sustainable Development Goals (SDGs), various efforts have been made to reduce the environmental burden, such as by using renewable energy to reduce emissions of greenhouse gases such as carbon dioxide. In the field of resin films used in packaging, various methods have been used to reduce the environmental burden, such as by using films made from plant-derived materials (biomass materials) instead of petroleum-derived materials. Accordingly, a non-oriented polypropylene film using plant-derived materials as part of the film's constituent materials has been proposed (see, for example, Patent Document 1).

[0004] Another environmental measure in the field of resin films is the reduction of film volume. Volume-reduced films tend to have reduced physical properties due to the thinner film itself. This reduction can be prevented by, for example, using a relatively high-density resin raw material. Since unstretched polypropylene films are not stretched, they have inferior water vapor barrier and gas barrier properties compared to uniaxially or biaxially oriented polypropylene films. Reducing the film thickness through volume reduction can further reduce these properties. Therefore, it has been necessary to innovate to ensure water vapor and gas barrier properties by laminating other films with water vapor and gas barrier properties or by applying coating agents. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-175606 Summary of the Invention [Problem to be solved by the invention]

[0006] However, depending on the application of the film, lamination may not be suitable, or coating may not be suitable when the unstretched polypropylene film is used alone. Therefore, there has been a need for a method that does not deteriorate the physical properties of the unstretched polypropylene film without using lamination or coating.

[0007] The present invention provides an unstretched polypropylene film that ensures good water vapor barrier properties without relying on lamination or coating, and that can suppress the deterioration of the water vapor barrier properties of a film that has been thinned by volume reduction. [Means for solving the problem]

[0008] That is, the first invention relates to an unstretched film body made mainly of polypropylene resin, which consists of three or more layers, at least a surface layer, a base layer, and a sealant layer, laminated in that order, and which is characterized in that the base layer contains 2.0% or more of an alicyclic hydrocarbon resin.

[0009] A second invention relates to the unstretched polypropylene film of the first invention, wherein the alicyclic hydrocarbon resin is a hydrogenated alicyclic hydrocarbon resin.

[0010] A third invention relates to the unstretched polypropylene film according to the first or second invention, wherein the softening point of the alicyclic hydrocarbon resin is 90 to 140°C.

[0011] A fourth invention relates to the unstretched polypropylene film according to the first or second invention, wherein the base layer contains 25.0% or less of an alicyclic hydrocarbon resin.

[0012] A fifth invention relates to the unstretched polypropylene film of the third invention, wherein the base layer contains 25.0% or less of an alicyclic hydrocarbon resin.

[0013] A sixth aspect of the present invention relates to the unstretched polypropylene film of the first or second aspect of the present invention, wherein the sum of the tensile modulus in the machine (MD) direction and the tensile modulus in the transverse (TD) direction (MD+TD) is 1.5 to 3.0 GPa.

[0014] A seventh aspect of the present invention relates to the unstretched polypropylene film of the third aspect, which has a sum (MD+TD) of the tensile modulus of elasticity in the machine (MD) direction and the tensile modulus of elasticity in the transverse (TD) direction of 1.5 to 3.0 GPa.

[0015] An eighth aspect of the present invention relates to the unstretched polypropylene film of the fourth aspect, wherein the sum of the tensile modulus in the machine (MD) direction and the tensile modulus in the transverse (TD) direction (MD+TD) is 1.5 to 3.0 GPa.

[0016] A ninth aspect of the present invention relates to the unstretched polypropylene film of the fifth aspect, which has a sum (MD+TD) of tensile modulus of elasticity in the machine (MD) direction and tensile modulus of elasticity in the transverse (TD) direction of 1.5 to 3.0 GPa.

[0017] A tenth aspect of the present invention relates to a non-stretched polypropylene film for packaging bread, in which the non-stretched polypropylene film according to the first or second aspect of the present invention is used for packaging bread.

[0018] An eleventh aspect of the present invention relates to a non-stretched polypropylene film for packaging bread, in which the non-stretched polypropylene film according to the third aspect of the present invention is used for packaging bread.

[0019] A twelfth aspect of the present invention relates to a non-stretched polypropylene film for packaging bread, in which the non-stretched polypropylene film according to the fourth aspect of the present invention is used for packaging bread.

[0020] A thirteenth aspect of the present invention relates to a non-stretched polypropylene film for packaging bread, in which the non-stretched polypropylene film according to the fifth aspect of the present invention is used for packaging bread.

[0021] A fourteenth aspect of the present invention relates to a non-stretched polypropylene film for packaging bread, in which the non-stretched polypropylene film according to the sixth aspect of the present invention is used for packaging bread.

[0022] A fifteenth aspect of the present invention relates to a non-stretched polypropylene film for packaging bread, in which the non-stretched polypropylene film according to the seventh aspect of the present invention is used for packaging bread.

[0023] A sixteenth aspect of the present invention relates to a non-stretched polypropylene film for packaging bread, in which the non-stretched polypropylene film according to the eighth aspect of the present invention is used for packaging bread.

[0024] A seventeenth aspect of the present invention relates to a non-stretched polypropylene film for packaging bread, in which the non-stretched polypropylene film according to the ninth aspect of the present invention is used for packaging bread. [Effects of the Invention]

[0025] The unstretched polypropylene film according to the first aspect of the present invention is an unstretched film body made primarily of polypropylene resin, which comprises three or more layers: at least a surface layer, a base layer, and a sealant layer, with the surface layer, base layer, and sealant layer laminated in that order. Since the base layer contains 2.0% or more of an alicyclic hydrocarbon resin, good water vapor barrier properties can be ensured without lamination or coating, and a decrease in water vapor barrier properties due to volume reduction of the film can be suppressed while also suppressing a decrease in film rigidity.

[0026] According to the non-stretched polypropylene film of the second invention, since the alicyclic hydrocarbon resin in the first invention is a hydrogenated alicyclic hydrocarbon resin, compatibility when mixed with a polypropylene resin is good.

[0027] According to the non-stretched polypropylene film of the third invention, since the softening point of the alicyclic hydrocarbon resin in the first or second invention is 90 to 140°C, the water vapor barrier property can be more appropriately improved without deteriorating the physical properties of the film.

[0028] According to the unstretched polypropylene film of the fourth invention, in the first or second invention, the base layer contains 25.0% or less of an alicyclic hydrocarbon resin, so that it is possible to appropriately improve the water vapor barrier property while suppressing a decrease in rigidity due to thinning.

[0029] According to the unstretched polypropylene film of the fifth invention, in the third invention, the base layer contains 25.0% or less of an alicyclic hydrocarbon resin, so that it is possible to appropriately improve the water vapor barrier property while suppressing a decrease in rigidity due to thinning.

[0030] According to the unstretched polypropylene film of the sixth invention, in the first or second invention, the sum of the tensile modulus in the machine direction (MD) and the tensile modulus in the transverse direction (TD) (MD+TD) is 1.5 to 3.0 GPa, so that the volume of the film can be appropriately reduced.

[0031] According to the unstretched polypropylene film of the seventh invention, in the third invention, the sum of the tensile modulus in the machine direction (MD) and the tensile modulus in the transverse direction (TD) (MD+TD) is 1.5 to 3.0 GPa, so that the volume of the film can be appropriately reduced.

[0032] According to the unstretched polypropylene film of the eighth invention, in the fourth invention, the sum of the tensile modulus in the machine direction (MD) and the tensile modulus in the transverse direction (TD) (MD+TD) is 1.5 to 3.0 GPa, so that the volume of the film can be appropriately reduced.

[0033] According to the non-stretched polypropylene film of the ninth invention, in the fifth invention, the sum of the tensile modulus in the machine direction (MD) and the tensile modulus in the transverse direction (TD) (MD+TD) is 1.5 to 3.0 GPa, so that the volume of the film can be appropriately reduced.

[0034] The unstretched polypropylene film for packaging bread according to the tenth invention is the unstretched polypropylene film according to the first or second invention, which is used to package bread. Therefore, it is possible to provide a film suitable for packaging bread that can contribute to reducing the environmental load by reducing the volume while maintaining good water vapor barrier properties.

[0035] The unstretched polypropylene film for packaging bread according to the eleventh invention is the unstretched polypropylene film according to the third invention, which is used to package bread. Therefore, it is possible to provide a film suitable for packaging bread that can contribute to reducing the environmental load by reducing the volume while maintaining good water vapor barrier properties.

[0036] The unstretched polypropylene film for packaging bread according to the twelfth invention is the unstretched polypropylene film according to the fourth invention, which is used to package bread. Therefore, it is possible to provide a film suitable for packaging bread that can contribute to reducing the environmental load by reducing the volume while maintaining good water vapor barrier properties.

[0037] The unstretched polypropylene film for packaging bread according to the thirteenth invention is the unstretched polypropylene film according to the fifth invention, which is used to package bread. Therefore, it is possible to provide a film suitable for packaging bread that can contribute to reducing the environmental load by reducing the volume while maintaining good water vapor barrier properties.

[0038] The unstretched polypropylene film for packaging bread according to the fourteenth invention is the unstretched polypropylene film according to the sixth invention, which is used to package bread. Therefore, it is possible to provide a film suitable for packaging bread that can contribute to reducing the environmental load by reducing the volume while maintaining good water vapor barrier properties.

[0039] The unstretched polypropylene film for packaging bread according to the fifteenth invention is the unstretched polypropylene film according to the seventh invention, which is used to package bread. Therefore, it is possible to provide a film suitable for packaging bread that can contribute to reducing the environmental load by reducing the volume while maintaining good water vapor barrier properties.

[0040] The unstretched polypropylene film for packaging bread according to the sixteenth invention is the unstretched polypropylene film according to the eighth invention, which is used to package bread. Therefore, it is possible to provide a film suitable for packaging bread that can contribute to reducing the environmental load by reducing the volume while maintaining good water vapor barrier properties.

[0041] The unstretched polypropylene film for packaging bread according to the seventeenth invention is the unstretched polypropylene film according to the ninth invention, which is used to package bread. Therefore, it is possible to provide a film suitable for packaging bread that can contribute to reducing the environmental load by reducing the volume while maintaining good water vapor barrier properties. [Brief explanation of the drawings]

[0042] [Figure 1] 1 is a schematic cross-sectional view of an unstretched polypropylene film according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0043] The unstretched polypropylene film 10 of the present invention shown in FIG. 1 is an unstretched film body mainly made of polypropylene resin, which is composed of three or more layers, namely, at least a surface layer 20, a base layer 30, and a sealant layer 40, and in which the surface layer 20, the base layer 30, and the sealant layer 40 are laminated in this order.

[0044] The unstretched polypropylene film 10 is produced by a known film production method such as the T-die method or the inflation method. The term "unstretched" in this film 10 refers to a state in which the film is not substantially stretched in a specific direction such as the take-up direction or the width direction, and also includes cases in which stretching is applied as an unavoidable force during film production. The unstretched polypropylene film 10 exhibits good heat seal strength because stretching is suppressed and the film has relatively low orientation.

[0045] The polypropylene resin used in the non-oriented polypropylene film 10 can be appropriately selected from resins produced from suitable starting materials, such as petroleum-derived, biomass-derived, material-recycled, and chemical-recycled. The polypropylene resin can be any common polypropylene resin, such as at least one selected from propylene homopolymer, propylene-α-olefin random copolymers such as propylene-ethylene random copolymers and propylene-ethylene-butene random copolymers, or propylene-ethylene block copolymers. A polypropylene-α-olefin random copolymer is particularly preferred. The polypropylene resin can also be a mixture of one or more of the above. Furthermore, catalysts used in producing the polypropylene resin include Ziegler-Natta catalysts containing a solid titanium catalyst component and an organometallic compound catalyst component, and metallocene catalysts. Each layer of the non-oriented polypropylene film may contain other resins. For example, other resins, such as masterbatches for additives, may be included to the extent that they do not impair the film's properties.

[0046] From the viewpoint of reducing environmental impact, polypropylene resins may contain polyolefin resins derived from recycled materials such as material recycling and chemical recycling, or from biomass. Examples of biomass-derived polyolefin resins include polyethylene-based resins obtained by processing plant materials. Specifically, these are polyethylene-based resins produced by subjecting sugar solutions extracted from plant materials such as sugarcane to alcoholic fermentation using yeast to produce ethanol, which is then converted into ethylene, and then subjected to a known resinification process. The higher the weight proportion of biomass-derived polyolefin resin, the greater the contribution to reducing environmental impact.

[0047] Furthermore, additives such as lubricants, antistatic agents, antiblocking agents, crystal nucleating agents, heat stabilizers, antioxidants, light stabilizers, ultraviolet absorbers, colorants, etc. may be added to each layer as needed within the range that does not impair the properties of the film of the present invention. The type of additive may be determined appropriately depending on the application, and for example, fatty acid amides may be added as lubricants.

[0048] The surface layer 20 corresponds to one surface layer of the unstretched polypropylene film 10. The polypropylene resin constituting the surface layer 20 is not particularly limited and can be appropriately selected from general polypropylene resins. The surface layer 20 may be subjected to an appropriate surface treatment such as corona treatment, flame treatment, or plasma treatment depending on the application.

[0049] The base layer 30 corresponds to the middle layer of the unstretched polypropylene film 10. The polypropylene resin constituting the base layer 30 is not particularly limited and can be appropriately selected from general polypropylene resins. The polypropylene resin of the base layer 30 may be the same as or different from the polypropylene resin used in the surface layer 20.

[0050] The sealant layer 40 corresponds to the surface layer on the other side of the unstretched polypropylene film 10 and has heat sealing properties. When used as a packaging material (packaging bag), the sealant layer 40 becomes the sealing surface on the inner side of the bag. As the polypropylene resin constituting the sealant layer 40, a polymer mainly composed of propylene, such as a copolymer (propylene copolymer) of propylene with other olefins such as ethylene or butene, is preferably selected.

[0051] In this type of unstretched polypropylene film 10, when volume reduction is attempted, the water vapor barrier property, which is already not as high as that of stretched polypropylene films, may deteriorate further, and the strength may decrease. The present inventors have conducted extensive research, focusing on the resin to be added to the base layer 30 of the film, to produce a film that can be reduced in volume while suppressing the deterioration of water vapor barrier property and further suppressing the deterioration of rigidity without using lamination or coating, and have found that these problems can be solved.

[0052] That is, in the non-stretched polypropylene film 10 of the present invention, the base layer 30 contains 2.0% or more of an alicyclic hydrocarbon resin, commonly known as a petroleum resin. Alicyclic hydrocarbon resins are hydrocarbons that are not aromatic hydrocarbons but have a cyclic molecular structure, and are relatively bulky compounds. Non-stretched polypropylene films have crystalline and amorphous portions, and water vapor permeates through the amorphous portions, making it difficult to achieve high water vapor barrier properties. Reducing the film thickness by volume reduction also reduces water vapor barrier properties. It is believed that adding an alicyclic hydrocarbon resin to this polypropylene film fills the amorphous portions with the alicyclic hydrocarbon resin molecules, suppressing molecular motion and inhibiting water vapor permeation.

[0053] The amount of alicyclic hydrocarbon resin added to ensure water vapor barrier properties is preferably 2.0% or more, more preferably 5.0% or more, and even more preferably 9.0% or more, in the resin constituting the base layer 30. From the perspective of ensuring water vapor barrier properties, there is no particular upper limit to the amount of alicyclic hydrocarbon resin contained in the base layer 30. However, since alicyclic hydrocarbon resins are relatively hard resins, an excessive amount in the base layer 30 may cause the film to become brittle. Therefore, from the perspective of ensuring the rigidity of the film, it is considered appropriate to set the upper limit of the amount of alicyclic hydrocarbon resin contained in the base layer 30 to 25.0%. By adding an appropriate amount of alicyclic hydrocarbon resin to the base layer 30, it is possible to appropriately improve water vapor barrier properties while suppressing a decrease in rigidity due to thinning.

[0054] Examples of alicyclic hydrocarbon resins that can be added to the unstretched polypropylene film 10 include C5 petroleum resins, C9 petroleum resins, C5-C9 copolymer petroleum resins, dicyclopentadiene petroleum resins, coumarone-indene resins, terpene resins, and rosin resins. Hydrogenated alicyclic hydrocarbon resins are particularly preferred. Hydrogenated alicyclic hydrocarbon resins are hydrogenated alicyclic hydrocarbon resins that exhibit good compatibility when mixed with polypropylene resins. Examples of hydrogenated alicyclic hydrocarbon resins include hydrogenated C5 petroleum resins, hydrogenated C9 petroleum resins, hydrogenated C5-C9 copolymer petroleum resins, hydrogenated dicyclopentadiene petroleum resins, hydrogenated coumarone-indene resins, hydrogenated terpene resins, and hydrogenated rosin resins.

[0055] The alicyclic hydrocarbon resin added to the unstretched polypropylene film 10 preferably has a softening point of 90 to 140°C. If the softening point of the alicyclic hydrocarbon resin is too low, it may bleed out to the film surface, impairing anti-blocking performance, while if the softening point is too high, it may become less compatible with the polypropylene resin of the base layer 30, resulting in a decrease in transparency. By using an alicyclic hydrocarbon resin with the above-mentioned appropriate softening point, it is possible to more appropriately improve the water vapor barrier property without deteriorating the physical properties of the film.

[0056] In the non-stretched polypropylene film 10 of the present invention, the higher the water vapor barrier property, the better, and the water vapor permeability is used as an index of this property. 2 ·day) is a value that indicates the amount of water vapor permeation measured under conditions of a temperature of 40°C and a relative humidity of 90% (90% RH) using a measurement method in accordance with JIS K 7129-2 (2019). The lower the value, the higher the water vapor barrier properties. The preferred water vapor permeability is 14.5 g / m 2 ·day or less, preferably 12.0 g / m 2 ·day or less, more preferably 10.0 g / m 2 ·day or less.

[0057] Furthermore, the non-stretched polypropylene film 10 of the present invention preferably has good tensile properties. The tensile properties can be used as an index of processability. Examples of evaluation items for the tensile properties include the tensile modulus (GPa).

[0058] The tensile modulus (GPa) is used as an index of film rigidity and is measured based on the test method for plastic tensile properties in accordance with JIS K 7127 (1999). In the non-stretched polypropylene film 10 of the present invention, the sum of the tensile modulus in the machine direction (MD) and the tensile modulus in the transverse direction (TD) (MD+TD) is preferably 1.5 to 3.0 GPa. It is more preferable that the tensile modulus in the machine direction (MD) is 0.75 to 1.5 GPa, and the tensile modulus in the transverse direction (TD) is 0.75 to 1.5 GPa. If the tensile modulus is insufficient, the film may not be appropriately reduced in volume. If the tensile modulus is excessive, the impact strength of the film may be reduced.

[0059] The non-oriented polypropylene film 10 of the present invention preferably has the transparency required for applications such as packaging films. The transparency of the film is expressed by the haze (%) measured in accordance with JIS K 7136 (2000). The preferred haze for the film is 10.0% or less. If the haze is too high, the transparency generally required for packaging films and the like will be insufficient, which is undesirable.

[0060] As described above, the non-stretched polypropylene film 10 of the present invention, which contains an alicyclic hydrocarbon resin in the base layer 30, can improve the low water vapor barrier properties inherent to non-stretched films without relying on lamination or coating, thereby ensuring good water vapor barrier properties, and can also suppress a decrease in water vapor barrier properties due to film volume reduction while suppressing a decrease in film rigidity. Therefore, the non-stretched polypropylene film 10 of the present invention can maintain the performance of a non-stretched polypropylene film while reducing the amount of polypropylene resin used, thereby contributing to a reduction in the environmental load.

[0061] The unstretched polypropylene film 10 of the present invention is suitably used for various packaging materials (packaging bags) for foods such as bread and fresh noodles, detergents, cosmetics, other pharmaceutical products, etc. In particular, since the film can contribute to reducing the environmental load by reducing the volume while maintaining good water vapor barrier properties, it can be suitably used as a unstretched polypropylene film for packaging breads such as bread. [Example]

[0062] [Preparation of unstretched polypropylene film] In producing the unstretched polypropylene films of Prototype Examples 1 to 4 and Comparative Example 1, the materials described below were fed into an extrusion device, melted and kneaded, and extruded into three layers, a surface layer, a base layer, and a sealant layer, using a T-die method to produce a film with an overall thickness (total thickness) of 30 μm. The layer thickness (layer ratio) of each layer relative to the total thickness was adjusted to 1:4:1. After film production, the surface layer was subjected to a surface treatment using a corona discharge treatment. In Prototype Examples 1 to 4 and Comparative Example 1, the resin content of each layer was 100% by weight. Additives such as antiblocking agents were omitted.

[0063] [Materials used] The following resins were used as the resin materials for the surface layer, base layer and sealant layer. The resin compositions of each layer for the unstretched polypropylene films of Prototype Examples 1 to 4 and Comparative Example 1 are shown in Table 1 below.

[0064] PP1: Propylene-ethylene-butene random copolymer, MFR7, Tm: 140℃ CA1: Alicyclic hydrocarbon resin; a petroleum resin masterbatch based on homopolypropylene (MFR 1.9, Tm 165°C) containing 24% by weight of hydrogenated dicyclopentadiene petroleum resin with a softening point of 140°C.

[0065] [Prototype 1] Prototype example 1 is an unstretched polypropylene film that contains 100.0 wt% PP1 as the surface layer, 91.6 wt% PP1 and 8.4 wt% CA1 as the base layer, and 100.0 wt% PP1 as the sealant layer, with the amount of alicyclic hydrocarbon resin in the base layer being 2.0%.

[0066] [Prototype 2] Prototype 2 is an unstretched polypropylene film similar to Prototype 1, except that the base layer contains 79.1 wt % PP1 and 20.9 wt % CA1, and the amount of alicyclic hydrocarbon resin in the base layer is 5.0%.

[0067] [Prototype 3] Prototype 3 is an unstretched polypropylene film similar to Prototype 1, except that the base layer contained 60.0 wt% PP1 and 40.0 wt% CA1, and the amount of alicyclic hydrocarbon resin in the base layer was 9.6%.

[0068] [Prototype 4] Prototype 4 is a non-stretched polypropylene film similar to Prototype 1 except that the base layer was made of 100% by weight of CA1 and the amount of alicyclic hydrocarbon resin in the base layer was 24.0%.

[0069] [Comparative Example 1] Comparative Example 1 is an unstretched polypropylene film that is the same as Prototype Example 1 except that the base layer contains 100% by weight of PP1 and the amount of alicyclic hydrocarbon resin in the base layer is 0.0%.

[0070] [Table 1]

[0071] The unstretched polypropylene films of Prototype Examples 1 to 4 and Comparative Example 1 were evaluated for water vapor barrier properties by water vapor permeability (g / m 2 ·day) was measured. In addition, transparency and tensile properties were evaluated as other film performances. For transparency, haze (%) was measured, and for tensile properties, tensile modulus (GPa) was measured. The results of each measurement are shown in Table 2 below.

[0072] [Water vapor permeability measurement] Water vapor permeability (g / m 2 The water vapor barrier property (water vapor permeability) was measured at a temperature of 40°C and a relative humidity of 90% (90% RH) using a water vapor transmission rate measuring device (MOCON's "PERMATRAN-W (registered trademark) 3 / 33 G+") in accordance with JIS K 7129-2 (2019). The measurement result for water vapor barrier property (water vapor permeability) was 14.5 g / m 2 A period of 0.5 days or less was judged to be good.

[0073] [Haze measurement] Haze (%) was measured in accordance with JIS K 7136 (2000) using a haze meter ("Haze Meter NDH-4000" manufactured by Nippon Denshoku Industries Co., Ltd.) Transparency (haze) was judged to be good when the measurement result was 10% or less.

[0074] [Measurement of tensile modulus] The tensile modulus (GPa) was measured in both the machine direction (MD) and the transverse direction (TD) using a tensile testing machine (ORIENTEC Co., Ltd.; "RTF-1310") based on the test method for plastic tensile properties in accordance with JIS K 7127 (1999). For tensile properties (tensile modulus), a measurement result of 1.5 to 3.0 GPa for the sum of the machine direction tensile modulus and the transverse direction tensile modulus (MD + TD) was judged to be good.

[0075] [Table 2]

[0076] [Results and Discussion] As shown in Table 2, Prototypes 1, 2, 3, and 4, which contained an alicyclic hydrocarbon resin in the base layer, had lower water vapor permeability and improved water vapor barrier properties compared to Comparative Example 1. Furthermore, a comparison of Prototypes 1, 2, 3, and 4 showed that the films with a higher amount of alicyclic hydrocarbon resin in the base layer had even more improved water vapor barrier properties. In other words, since the inclusion of an alicyclic hydrocarbon resin in the base layer improves water vapor barrier performance, it can be understood that even when a non-oriented polypropylene film is made thinner, it is possible to ensure water vapor barrier properties by itself, without lamination or coating.

[0077] Next, other film properties of the films of Prototype Examples 1 to 4 will be examined. It was shown that the transparency (haze) of all of Prototype Examples 1 to 4 was improved compared to Comparative Example 1. It was also shown that the transparency generally improved as the amount of alicyclic hydrocarbon resin in the base layer of the film increased. Meanwhile, in terms of tensile properties (tensile modulus), when the amount of alicyclic hydrocarbon resin in the base layer was small (Prototype Example 1), the performance was comparable to that of Comparative Example 1. However, when the amount of alicyclic hydrocarbon resin in the base layer was a certain amount or more (for example, 5% or more), as in Prototype Examples 2 to 4, the tensile properties of the film increased as the amount added increased.

[0078] From this, it was understood that adding an appropriate amount of alicyclic hydrocarbon resin to the base layer of a non-oriented polypropylene film has a favorable effect on the physical properties of the film other than the water vapor barrier property. In other words, for a non-oriented polypropylene film that is expected to be used alone, adding an appropriate amount of alicyclic hydrocarbon resin to the base layer not only improves the water vapor barrier property but also improves the transparency and tensile properties, and greatly contributes to suppressing the deterioration of various physical properties when the film is made thinner. [Industrial Applicability]

[0079] As described above, the non-oriented polypropylene film of the present invention improves on the low water vapor barrier properties inherent to non-oriented films and can suppress the deterioration of water vapor barrier properties that tend to occur when volume reduction is attempted, and therefore can be made into a film with physical properties that can withstand use alone without lamination or coating. Furthermore, since it has excellent transparency and tensile properties and can suppress the decrease in rigidity due to volume reduction, it can suppress the decrease in various physical properties due to volume reduction of the film and can contribute to reducing the environmental load, making it a promising alternative to conventional non-oriented polypropylene films. [Explanation of symbols]

[0080] 10. Unstretched polypropylene film 20 Surface layer 30 base layer 40 Sealant Layer

Claims

1. It consists of at least three or more layers, including a surface layer, a base layer, and a sealant layer, An unstretched film body mainly made of polypropylene resin, in which the surface layer, the base layer, and the sealant layer are laminated in this order, The base layer contains 2.0% or more of an alicyclic hydrocarbon resin. A non-oriented polypropylene film characterized by:

2. 2. The non-oriented polypropylene film according to claim 1, wherein the alicyclic hydrocarbon resin is a hydrogenated alicyclic hydrocarbon resin.

3. 3. The non-oriented polypropylene film according to claim 1, wherein the softening point of the alicyclic hydrocarbon resin is 90 to 140°C.

4. 3. The unstretched polypropylene film according to claim 1, wherein the base layer contains 25.0% or less of an alicyclic hydrocarbon resin.

5. The unstretched polypropylene film according to claim 3, wherein the base layer contains 25.0% or less of an alicyclic hydrocarbon resin.

6. 3. The non-oriented polypropylene film according to claim 1, wherein the sum of the tensile modulus in the machine direction (MD) and the tensile modulus in the transverse direction (TD) (MD+TD) is 1.5 to 3.0 GPa.

7. The non-oriented polypropylene film according to claim 3, wherein the sum of the tensile modulus in the machine direction (MD) and the tensile modulus in the transverse direction (TD) (MD+TD) is 1.5 to 3.0 GPa.

8. The non-stretched polypropylene film according to claim 4, wherein the sum of the tensile modulus in the machine direction (MD) and the tensile modulus in the transverse direction (TD) (MD+TD) is 1.5 to 3.0 GPa.

9. The non-oriented polypropylene film according to claim 5, wherein the sum of the tensile modulus in the machine direction (MD) and the tensile modulus in the transverse direction (TD) (MD+TD) is 1.5 to 3.0 GPa.

10. 3. A non-oriented polypropylene film for packaging bread, wherein the non-oriented polypropylene film according to claim 1 or 2 is used for packaging bread.

11. 4. A non-oriented polypropylene film for packaging bread, wherein the non-oriented polypropylene film according to claim 3 is used for packaging bread.

12. 5. A non-oriented polypropylene film for packaging bread, wherein the non-oriented polypropylene film according to claim 4 is used for packaging bread.

13. 6. A non-oriented polypropylene film for packaging bread, wherein the non-oriented polypropylene film according to claim 5 is used for packaging bread.

14. 7. A non-oriented polypropylene film for packaging bread, wherein the non-oriented polypropylene film according to claim 6 is used for packaging bread.

15. 8. A non-oriented polypropylene film for packaging bread, wherein the non-oriented polypropylene film according to claim 7 is used for packaging bread.

16. 9. A non-oriented polypropylene film for packaging bread, wherein the non-oriented polypropylene film according to claim 8 is used for packaging bread.

17. 10. A non-oriented polypropylene film for packaging bread, wherein the non-oriented polypropylene film according to claim 9 is used for packaging bread.

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