Polypropylene-based packaging materials

Abstract

To provide a packaging material having all of low-temperature drop impact resistance, blocking resistance, slipperiness, and flavor properties.SOLUTION: A polypropylene-based packaging material comprises an ethylene / propylene block copolymer having a phase dispersion structure in which a resin comprising polypropylene as a main component constitutes a matrix and a spindle-shaped polypropylene-based elastomer constitute domains.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polypropylene-based packaging material, and more particularly, to a polypropylene-based packaging material having impact resistance, blocking resistance, slipperiness, and flavor properties, and being suitably used for food packaging.

Background Art

[0002] Packaging materials made of propylene-based polymers can exhibit heat sealability and are excellent in heat resistance, hygiene, and flavor properties, and thus are widely used as packaging materials for containing various foods. In recent years, from the viewpoints of weight reduction and economy, the thickness of packaging containers has been decreasing, and impact resistance at low temperatures (impact resistance) is also required to cope with use in cold regions, etc., and higher impact resistance is demanded. As such polypropylene having high impact resistance, a propylene block copolymer also called impact polypropylene is used for packaging materials.

[0003] Another performance required for packaging materials is blocking resistance. That is, it is necessary that blocking hardly occurs when films are overlapped. However, films made of the above propylene block copolymer have poor blocking resistance because a soft rubber component is blended, and it is desired to be further modified. In order to improve such properties as impact resistance and blocking resistance, for example, Patent Document 1 below proposes a propylene-based resin composition obtained by blending an ethylene-α-olefin copolymer with a propylene block copolymer.

[0004] Also, Patent Document 2 below proposes a multilayer film using a polypropylene block copolymer and having a surface layer in which substantially spherical elastomer particles are dispersed.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2006-161033 [Patent Document 2] Japanese Patent Publication No. 2006-198977 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] For containers such as trays and cups, container molding, filling and sealing, and packaging are performed continuously while the containers are transported on a conveyor line. Therefore, it is required that the containers have good transportability, i.e., smoothness, to prevent container jams on the line, and polypropylene-based packaging materials also need to have excellent smoothness. Furthermore, especially in food applications, it is important that the containers do not impair the flavor of the contents. However, the packaging materials using propylene block copolymers described in Patent Documents 1 and 2 above have been insufficient to fully satisfy all requirements for drop impact resistance, blocking resistance, and slipperiness under low-temperature conditions. Furthermore, it has been difficult to provide a packaging material that possesses these properties along with desirable appearance and flavor characteristics.

[0007] Therefore, the objective of the present invention is to provide a polypropylene-based packaging material that possesses all of the following qualities: resistance to drop impact, resistance to blocking, slipperiness, and flavor properties under low-temperature conditions. [Means for solving the problem]

[0008] According to the present invention, an ethylene-propylene block copolymer having a phase dispersion structure in which a resin mainly composed of polypropylene is the matrix and spindle-shaped polypropylene elastomers are the domains, The following is a compound containing 1 to 30 parts by mass of the polypropylene-based elastomer per 100 parts by mass of the resin mainly composed of polypropylene:The provided polypropylene packaging material is characterized in that the aspect ratio of the domain is in the range of 1.2 to 9.0, the minor axis of the domain is in the range of 0.2 to 4.0 μm and the major axis is in the range of 0.5 to 5.0 μm, the weight-average molecular weight (Mw) of the polypropylene elastomer is 500,000 to 1,000,000, the number-average molecular weight (Mn) is 10,000 to 300,000, and the slipperiness, which is the drag resistance value (23℃ 50%RH) measured at a speed of 100 mm / min with a 600 g weight loaded using a friction measuring instrument, is less than 3.0 N.

[0009] In the packaging material of the present invention, 1.before The resin, primarily composed of polypropylene, has a weight-average molecular weight (Mw) of 300,000 to 800,000, and a number-average molecular weight (Mn) of 10,000 to 300,000. 2 The ethylene-propylene block copolymer contains 1 to 40 parts by mass of homopolypropylene per 100 parts by mass. 3 It must be one of the following: a sheet, film, tray, or cup. This is preferable. [Effects of the Invention]

[0010] The packaging material of the present invention has a matrix of polypropylene-based resin, with a dispersed structure in which spindle-shaped polypropylene elastomers form domains. By controlling the shape and size of these spindle-shaped domains, it is possible to achieve excellent drop impact resistance, slipperiness, and blocking resistance simultaneously. Furthermore, by using specific polypropylene-based elastomers, it is possible to achieve excellent flavor properties. [Brief explanation of the drawing]

[0011] [Figure 1] This figure illustrates the domain shape in the packaging material of the present invention. [Modes for carrying out the invention]

[0012] (Polypropylene-based packaging materials) As described above, a key feature of the packaging material of the present invention is that it has a phase dispersion structure in which a resin mainly composed of polypropylene forms the matrix and spindle-shaped polypropylene elastomers form the domains. In this invention, spindle-shaped domains made of polypropylene elastomer are dispersed in a matrix made of a resin mainly composed of polypropylene, thereby further improving drop impact resistance. Furthermore, by controlling the particle size of these rubber component domains, it is possible to achieve not only drop impact resistance but also a balance of slipperiness and blocking resistance. In other words, in packaging materials using propylene block copolymers, in order to exhibit excellent drop impact resistance even at low temperatures, it is preferable that the rubber component (polypropylene elastomer) content is high, and that the domains (dispersed particles) consisting of this rubber component are finely dispersed not only in terms of drop impact resistance but also in terms of appearance characteristics. On the other hand, in order to improve blocking resistance and slipperiness, it is preferable that the rubber component content is low, and that the dispersed particles consisting of this rubber component are large enough to form irregularities on the surface. From this perspective, the present invention has found that by having a dispersed structure in which spindle-shaped domains made of polypropylene-based elastomer are formed in a matrix made of a resin mainly composed of polypropylene, it is possible to achieve excellent drop impact resistance, blocking resistance, and slipperiness simultaneously.

[0013] In this invention, in order to exhibit excellent drop impact resistance by domains made of polypropylene elastomer, it is preferable that the spindle-shaped domains have an aspect ratio in the range of 1.2 to 9.0, 1.2 to 8.0, 1.9 to 8.0, and particularly 1.9 to 5.0. A larger aspect ratio tends to result in better drop impact resistance but poorer slipperiness. Furthermore, it is preferable that such domains have a short axis in the range of 0.2 to 4.0 μm, particularly 0.2 to 2.0 μm, and a long axis in the range of 0.5 to 5.0 μm, particularly 0.5 to 3.0 μm. The method for measuring the short and long axes of the domains will be described later. Further, the domain size equivalent to a circle is preferably in the range of 0.5 μm to 5.0 μm, particularly 0.5 μm to 1.0 μm. If the domain size is too small, surface irregularities are not formed and the slipperiness is poor. If it is too large, irregularities are formed, the slipperiness is good, but the drop impact resistance tends to be poor.

[0014] The control of the domain shape and size described above is determined by the resin manufacturing method such as the molecular weight, composition, and kneading of the resin mainly composed of polypropylene as the matrix and the polypropylene-based elastomer. In the packaging material of the present invention, the polypropylene-based elastomer is preferably contained in an amount of 1 to 30 parts by mass, particularly 5.0 to 25 parts by mass, with respect to 100 parts by mass of the resin mainly composed of polypropylene. If the amount of the polypropylene-based elastomer is less than the above range, there is a possibility that the drop impact resistance cannot be sufficiently improved compared to the case within the above range. On the other hand, if the amount of the polypropylene-based elastomer is more than the above range, not only the blocking resistance and slipperiness decrease compared to the case within the above range, but also the flavor property decreases, and the surface irregularities become large and the appearance characteristics deteriorate.

[0015] [Resin mainly composed of polypropylene] In the packaging material of the present invention, the resin mainly composed of polypropylene serving as the matrix is a homo- or random polypropylene obtained by polymerizing a monomer mainly composed of propylene. The resin mainly composed of polypropylene preferably has a weight average molecular weight (Mw) in the range of 300,000 to 800,000, particularly 300,000 to 600,000, and a number average molecular weight (Mn) in the range of 10,000 to 300,000, particularly 50,000 to 200,000. If the molecular weight of the resin mainly composed of polypropylene is smaller than the above range, there is a possibility that the drop impact resistance decreases and the hygiene property is impaired compared to the case within the above range. On the other hand, if it is larger than the above range, there is a possibility that the moldability decreases due to abnormal resin pressure compared to the case within the above range. In addition, from the viewpoints of heat resistance and moldability, it is preferable that the resin mainly composed of polypropylene has a mesopentad fraction ([mmmm]), which is an index of stereoregularity, in the range of 95 to 99.

[0016] [Polypropylene-based elastomer] In the packaging material of the present invention, examples of the polypropylene-based elastomer constituting the spindle-shaped domain include propylene-ethylene-based elastomers. As the propylene-ethylene-based elastomer, a random copolymer of propylene and ethylene, and a copolymer in which the mass ratio of ethylene units to propylene units is in the range of 15:85 to 50:50 is preferable. Further, if necessary, an elastomer copolymerized with an α-olefin or the like may be used to improve compatibility and impact resistance. The polypropylene-based elastomer desirably has a weight average molecular weight (Mw) in the range of 500,000 to 1,000,000, preferably 650,000 to 1,000,000, more preferably 700,000 to 1,000,000, and particularly preferably 700,000 to 900,000, and a number average molecular weight (Mn) in the range of 10,000 to 300,000, preferably 20,000 to 200,000, and particularly preferably 100,000 to 200,000. When the molecular weight is smaller than the above range, the domain shape becomes streak-like, the particle size becomes small and finely dispersed, the surface unevenness of the container becomes smooth, and there is a risk that the blocking resistance and slipperiness cannot be satisfied. On the other hand, when the molecular weight is larger than the above range, the domain shape becomes substantially spherical, the particle size becomes large and sparsely dispersed, and there is a risk of inferior impact resistance. Furthermore, the flavor tends to decrease. Therefore, by controlling the mass ratio and molecular weight of ethylene units and propylene units of the polypropylene-based elastomer and the molecular weight of the resin mainly composed of polypropylene, the domain of the polypropylene-based elastomer can be extended to a spindle shape having the above-described aspect ratio, the compatibility between the two can be improved, and it becomes possible to be finely dispersed in the above-described size, and both impact resistance and blocking resistance and slipperiness can be achieved.

[0017] The following inferences are made regarding the spindle shape of the polypropylene elastomer of the present invention. In the case of a fabricated film or sheet, or a container that has undergone secondary processing such as a cup or tray, the resin is stretched in the direction of extrusion (molding). Therefore, the domain shape in the resin also follows, and the tip in the extrusion direction tapers, resulting in a spindle shape as shown in Figure 1. However, it is possible that the domain shape differs depending on the difference in molecular weight between the matrix and the domains, the molecular weight of the domains themselves, and the compatibility between the matrix and the domains. For example, if the molecular weight of the domains is low and the compatibility with the matrix is ​​high, it is presumed that they will be striated, resulting in poor slipperiness due to low surface roughness and smoothness. On the other hand, if the molecular weight of the domains is high and the compatibility with the matrix is ​​low, they will be approximately spherical, resulting in poor resistance to drop impact. Note that compatibility is affected by the composition of the polypropylene elastomer and the addition of ethylene-α-olefin copolymers, etc.

[0018] [Ethylene-propylene block copolymer] For ethylene-propylene block copolymers having a phase dispersion structure in which a resin mainly composed of polypropylene forms the matrix and spindle-shaped polypropylene elastomers form the domains, the MFR (at 230°C, 2.16 kg load) is preferably in the range of 0.1 to 10 g / 10 min, particularly 0.2 to 5 g / 10 min, from a molding perspective. Furthermore, the raw materials or part of the raw materials for resins mainly composed of polypropylene or polypropylene-based elastomers may be not only petroleum-derived, but also ethylene-propylene block copolymers manufactured from materials chemically recycled from waste plastics through monomerization technologies such as gasification or oil conversion, or from biomass materials such as plant-derived materials. The biomass content can be measured by radiocarbon concentration measurement, etc. Moreover, when manufacturing resins mainly composed of polypropylene or polypropylene-based elastomers, from the perspective of reducing environmental impact, SVHC substances such as phthalate ester compounds (as defined in the European Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) regulations) may be used during the polymerization stage from the raw materials. S ubstance of Very H igh C It is preferable to manufacture using a catalyst system that does not use oncern.

[0019] [Other ingredients] In the packaging material of the present invention, in addition to the ethylene-propylene block copolymer described above, it is preferable to incorporate homopolypropylene as a viscosity modifier. In other words, resin compositions consisting mainly of polypropylene and polypropylene-based elastomers tend to have high molecular weight polypropylene-based elastomers to achieve both drop impact resistance and slipperiness, resulting in high viscosity and sometimes poor moldability. By incorporating homopolypropylene, the viscosity can be adjusted and the extrusion properties of the molten resin can be improved, thereby improving moldability (workability) without compromising the drop impact resistance of the packaging material. From the viewpoint of viscosity adjustment, the MFR (Mass Fiber Refining Rate) of homopolypropylene (230°C, 2.16 kg load) is preferably in the range of 0.5 to 20 g / 10 min. Homopolypropylene is preferably added in an amount of 1 to 40 parts by mass, particularly 1 to 30 parts by mass, per 100 parts by mass of ethylene-propylene block copolymer.

[0020] Furthermore, in the packaging material of the present invention, rubber components such as ethylene-α-olefin copolymers such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene, as well as elastomers and plastomers, may be added to further improve drop impact resistance. In addition, lubricants such as calcium stearate and antiblocking agents such as silica particles may be added to improve slipperiness, and these may also be used in combination with the rubber components mentioned above. Small amounts of known additives, such as antioxidants, may also be added as needed. In light of the growing environmental concerns in recent years, it is important to incorporate materials that have been chemically recycled from waste plastics through monomerization technologies such as gasification and oil conversion, or biomass materials derived from plants, as part of efforts to reduce plastic use.

[0021] (Preparation of polypropylene-based packaging materials) The packaging material of the present invention can be prepared by known methods, such as melt extrusion or melt kneading these pellets in a kneader. In the present invention, it is necessary to melt-knead the polypropylene elastomer so that the domains are dispersed in a spindle shape with the aforementioned size and aspect ratio, and it is necessary to adjust the kneading conditions as appropriate according to the viscosity of the resin used. There are no particular restrictions on the temperature conditions during melt mixing, but it is preferable to carry it out in the range of 170 to 270°C. At temperatures lower than this range, mixing may not be efficient, and at temperatures higher than this range, resin degradation may occur.

[0022] The packaging material of the present invention can be molded into desired shapes such as films, sheets, and tubes by known manufacturing methods such as extrusion molding or injection molding of a melt-kneaded resin, or the obtained sheet can be molded into shapes such as cups and trays by thermoforming. The packaging material of the present invention preferably has a surface roughness (Sa) in the range of 0.15 to 1.0 μm. This allows for excellent blocking resistance and slipperiness without impairing the appearance characteristics. Surface roughness (Sa) is a parameter that extends the arithmetic mean height of a line (Ra) to a surface, and is defined in ISO 25178 as the average of the absolute differences in height of each point relative to the average plane of the surface.

[0023] Furthermore, the packaging material of the present invention may be a molded article having a single layer structure of the resin composition made of the ethylene-propylene block copolymer described above, but it may also have a multilayer structure with other layers. In the case of such a multilayer structure, the layer of the resin composition made of the ethylene-propylene block copolymer described above is preferably the surface layer (outermost or innermost layer) because it has excellent blocking resistance and slipperiness, and is particularly desirable to be the outermost layer. Other layers, though not limited to these, include known layers conventionally used in polypropylene-based multilayer packaging materials, such as gas barrier layers, oxygen-absorbing layers, regrinding layers, easily peelable layers, and adhesive layers. Furthermore, in the case of a multilayer structure, it is desirable that the resin or resin composition constituting the other layers has a thermal shrinkage rate similar to that of the ethylene-propylene block copolymer. This suppresses winding misalignment caused by differences in the shrinkage rates of the laminated sheets, thereby preventing the occurrence of molding defects. [Examples]

[0024] The present invention will be further explained by experimental examples, but the present invention is not limited thereto. (Experimental Examples 1-5) Using a multilayer sheet molding machine with 6 types and 7 layers, each resin was melted and kneaded in a single-screw extruder, extruded from the T-die at a T-die temperature of 230°C, solidified by contact with a cooling roll, and then wound up to form a multilayer sheet with a thickness of 500 μm. The layer structure from the outside is: outermost PP layer / regrind layer / adhesive layer / barrier layer / adhesive layer / oxygen scavenger layer / inner PP layer / easy-adhesion layer. For the outermost and inner PP layers, pellets of ethylene-propylene block copolymer consisting mainly of polypropylene resin and polypropylene elastomer having the composition and molecular weight shown in Table 1, along with a white coloring resin, were used. For the regrind layer, 44 parts by mass of the ethylene-propylene block copolymer shown in Table 1 were mixed with 100 parts by mass of scrap obtained by crushing a portion of the multilayer sheet, trim, and sheet skeleton generated during this test, and a compatibilizer and white coloring resin were added. For the adhesive layer, maleic anhydride-modified polypropylene was used, and for the oxygen scavenger layer, a resin composition was used prepared by kneading 29 parts by mass of an iron-based oxygen absorber (a mixture of 100 parts by mass of reduced iron powder, 2 parts by mass of sodium chloride, and 1 part by mass of calcium hydroxide) with 71 parts by mass of random polypropylene at an MFR of 0.6 g / 10 min. For the easy-adhesion layer, a resin dry-blended from polypropylene or polyethylene was used. Furthermore, the obtained multilayer sheet was heated to 145°C and a flanged multilayer tray was formed by vacuum pressure forming with plug assist. The dimensions of the container were as follows: flange outer diameter: long axis: 155mm x short axis: 120mm, opening diameter: long axis: 135mm x short axis: 100mm, bottom outer diameter: long axis: 115mm x short axis: 90mm, height: 35mm.

[0025] (Experimental Example 6) A multilayer tray was molded in the same manner as in Experimental Example 1, except that the resin used was a dry-blended mixture of 17.7 parts by mass of homopolypropylene with an MFR of 2.0 g / 10 min (230°C, 2.16 kg load) per 100 parts by mass of resin for the outermost PP layer and the inner PP layer.

[0026] The various measurement methods are as follows: <Structural analysis of ethylene-propylene block copolymer> In the ethylene-propylene block copolymers used in Experimental Examples 1-5, the blending ratio and molecular weight of the polypropylene-based resin (PP component) and the polypropylene-based elastomer (rubber component) were determined. 13 The components were determined by 13C-NMR (JEOL) and GPC (Agilent). As a pretreatment of the measurement samples, the resin was dissolved under reflux in xylene, cooled, and then separated into solid and liquid components. The xylene-soluble portion was reprecipitated with methanol, the precipitate was filtered and dried, and the mass was measured to determine the amount of rubber component. The xylene-insoluble portion was redissolved and reprecipitated with methanol, filtered, and dried resin, which was used as the PP component. Experimental Example 6 is a calculated value because it is a dry blend of homopolypropylene.

[0027] (1) Dispersion state (domain shape and size) The bottom of the obtained multilayer tray was cut parallel to the take-up direction during sheet manufacturing, and the cross-section was observed using a transmission electron microscope (TEM) (Hitachi, Ltd.). As a pretreatment, the sample cut from the multilayer tray was bonded to a cryogenic support, and the surface was prepared using a Leica ultramicrotome (Leica) equipped with a diamond knife in a cryogenic system, followed by vapor staining with metal oxides to prepare ultrathin sections. From the obtained TEM images (20 μm x 20 μm square), all domains of the polypropylene elastomer in the outermost PP layer of the multilayer tray were measured using image analysis particle size distribution software (Mac-View, manufactured by Mountec). The short and long axes of each domain were measured, and the aspect ratio and the domain size equivalent to a circle were calculated. The average value was calculated from the measurement results of the total number of domains.

[0028] (2) Surface roughness Sa (unit: μm) A 10mm x 10mm sample piece was cut from the bottom of the obtained multilayer tray. The shape of the outer surface of the container was measured using a non-contact surface shape analyzer (Zygo). MetroPro (Ver. 9.1.4 64-bit) was used as the application for measurement and image analysis. A range of 282μm x 212μm was measured, and from the obtained raw data, wavelengths below 1.326μm were cut to remove noise and obtain the measurement data. The average value was calculated from N=5.

[0029] (3) Slipperiness (unit: N) The sliding properties of the obtained multilayer trays were measured using a friction measuring instrument (manufactured by Toyo Seiki). The drag resistance value was determined by using the load applied to the load cell during measurement as the dynamic friction force. Measurements were taken at a speed of 100 mm / min with the multilayer tray placed on a SUS plate and a 600 g weight applied in an environment of 23°C and 50% RH. The average value was calculated from a sample size of 5. The evaluation criteria are as follows. ○: Less than 2.5N △: 2.5N or more and less than 3.0N ×: 3.0N or higher

[0030] (4) Drop impact resistance The resulting multilayer trays were filled with 200g of distilled water, heat-sealed with a lid, boiled at 95°C for 30 minutes, and then stored at 5°C for 24 hours. After storage, the drop resistance of the multilayer trays was assessed by dropping them from a height of 150cm in a 5°C environment. The sample size was 20. The evaluation criteria were as follows. ○: Items with 3 or fewer cracks. △: Items with fewer than 10 cracks ×: More than 10 broken pieces

[0031] (5) Flavor 200g of distilled water was placed in the resulting multilayer tray, heat-sealed with a lid, and sterilized by boiling at 95°C for 30 minutes. After storage, it was stored at room temperature for 24 hours. After storage, a sensory evaluation was conducted by 10 panelists using a 4-point scale, and the average score was calculated. The evaluation criteria were as follows: 0 is tasteless, and 4 is a level where the taste is very noticeable. ○: Less than 2.5 △: 2.5 or higher and less than 3.5 ×: 3.5 or higher

[0032] The results showed that in Experimental Examples 1 and 6, the spindle-shaped polypropylene elastomer provided a good balance of slipperiness and drop impact resistance, and Experimental Example 6, in particular, had low resin viscosity and excellent film-forming properties. In Experimental Example 2, the drop impact resistance was somewhat low, which is thought to be due to the small amount of polypropylene elastomer used. In Experimental Examples 3 and 5, the drop impact resistance was also somewhat low, which is thought to be due to the shape or particle size of the polypropylene elastomer. Furthermore, the flavor properties were poor, which is presumed to be due to the molecular weight of the polypropylene elastomer. In Experimental Example 4, the drop impact resistance was good, but the slipperiness was poor. This is thought to be because the striated shape of the polypropylene elastomer and high aspect ratio resulted in a smooth surface with a large contact area.

[0033] [Table 1] [Industrial applicability]

[0034] The packaging material of the present invention has excellent resistance to drop impact, blocking, and flavor, as well as excellent slipperiness, making it ideal for transport on production lines. For this reason, it is suitable for use as packaging material for mass-produced foods, particularly containers for rice and other foods where flavor is important. Furthermore, because it is made of a propylene polymer with excellent heat resistance, it can also be suitable for use as packaging material for pouches and other items subjected to retort sterilization.

Claims

1. An ethylene-propylene block copolymer having a phase dispersion structure in which a resin mainly composed of polypropylene is the matrix and spindle-shaped polypropylene elastomers form the domains, The following is a compound containing 1 to 30 parts by mass of the polypropylene-based elastomer per 100 parts by mass of the resin mainly composed of polypropylene: The aspect ratio of the domain is in the range of 1.2 to 8.0, the minor axis of the domain is in the range of 0.2 to 4.0 μm, and the major axis is in the range of 0.5 to 5.0 μm. The weight-average molecular weight (Mw) of the aforementioned polypropylene elastomer is 500,000 to 1,000,000, and the number-average molecular weight (Mn) is 10,000 to 300,000. A polypropylene-based packaging material characterized by having a slipperiness of less than 3.0 N, which is the drag resistance value (23°C, 50% RH) measured at a speed of 100 mm / min with a 600 g weight loaded using a friction measuring machine.

2. The polypropylene-based packaging material according to claim 1, wherein the resin mainly composed of polypropylene has a weight-average molecular weight (Mw) of 300,000 to 800,000 and a number-average molecular weight (Mn) of 10,000 to 300,000.

3. The polypropylene-based packaging material according to claim 1 or 2, wherein it contains 1 to 40 parts by mass of homopolypropylene per 100 parts by mass of the ethylene-propylene block copolymer.

4. A polypropylene-based packaging material according to any one of claims 1 to 3, which is a sheet, film, tray, or cup.

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