High-oriented polypropylene product as well as preparation method and application thereof

Abstract

The invention relates to the field of polymers, and discloses an oriented polymer product and a preparation method and application thereof, and high oriented polypropylene has the following characteristics: (a) tensile strength is greater than or equal to 110 MPa; (b) the flexural modulus is greater than or equal to 6 GPa; and (c) the orientation degree of the oriented polypropylene matrix in the polypropylene product on the (040) crystal face is less than or equal to-0.45. The orientation degree of the polypropylene matrix on the (040) crystal face is less than or equal to-0.45, so that the polypropylene product has high tensile strength and high bending modulus.

Description

Technical Field

[0001] This invention relates to the field of polymers, and more specifically, to an oriented polymer article, its preparation method, and its application. Background Technology

[0002] Wood-plastic composites are widely used in construction, decoration, transportation, and other industries, with a huge market potential. Currently, the most common type is made with polyvinyl chloride (PVC) as the matrix and wood flour, plant straw powder, plant seed shells, and other wood-based powders as fillers. The development and widespread application of wood-plastic composites help mitigate plastic waste pollution and reduce environmental pollution from agricultural waste incineration.

[0003] CN111234444A discloses a wood-plastic composite material with acrylonitrile-butadiene-styrene and polyvinyl chloride as the matrix and nitrogen-grafted lignin as the filler, which can be used in the construction field. In this technology, the lignin is modified to ensure uniform dispersion within the matrix, thereby reducing its impact on the matrix properties. Additionally, CN108104423A discloses a waterproof PVC wood-plastic board. By incorporating a sealing film and a waterproof sealing plate within the wood-plastic board, the entire board becomes waterproof.

[0004] Regardless of whether the filler is modified, the overall properties of the material are affected after the addition of filler. GB1311885A discloses a solid-phase stretching processing method, which can orient the polymer molecular chains, significantly altering the morphology and properties of the material. Based on this technology, Dow Chemical and Eovations in the United States have developed a high-strength material by blending polypropylene with inorganic fillers such as talc, resulting in a low-density, high-strength wood substitute that has attracted widespread attention. Summary of the Invention

[0005] The purpose of this invention is to further improve the orientation degree of oriented polypropylene in polypropylene products and the mechanical properties of polypropylene products, and to provide a highly oriented polypropylene product and its preparation method and application. The oriented polypropylene matrix in the highly oriented polypropylene product has a high degree of orientation. Specifically, the orientation degree of the oriented polypropylene matrix on the (040) crystal plane is less than or equal to -0.45, so that the polypropylene product has high tensile strength and high flexural modulus.

[0006] The polypropylene product is prepared by die stretching. By controlling the process flow, process conditions, and temperature after stretching, the molecular chain movement is controlled, which further improves the orientation of the molecular chains in the polypropylene product. Therefore, the tensile strength and other properties of the polypropylene product are improved. This process is simple to control and easy to implement.

[0007] The first aspect of this invention provides a highly oriented polypropylene article, characterized in that the highly oriented polypropylene has the following features:

[0008] (a) Tensile strength greater than or equal to 110 MPa;

[0009] (b) Flexural modulus greater than or equal to 6 GPa;

[0010] (c) The orientation degree of the oriented polypropylene matrix in the (040) crystal plane of the polypropylene product is less than or equal to -0.45.

[0011] A second aspect of the present invention provides a method for preparing the above-mentioned highly oriented polypropylene article, characterized in that the preparation method includes:

[0012] (a) Orientable polypropylene and additives are mixed, granulated, and molded to obtain a pretreated sample; the orientable polypropylene is homopolymer polypropylene;

[0013] (b) The pretreated sample is subjected to die stretching and cooling treatment to obtain a highly oriented polypropylene product;

[0014] The cooling rate of the cooling process is greater than or equal to 5°C / min;

[0015] The cooling process begins at a distance of 0.1-30cm from the stretching die.

[0016] A third aspect of the present invention provides a highly oriented polypropylene product prepared by the above-described preparation method.

[0017] A fourth aspect of the present invention provides an application of the above-mentioned highly oriented polypropylene product in building decoration.

[0018] Through the above technical solutions, the highly oriented polypropylene products, their preparation methods, and applications provided by the present invention achieve the following beneficial effects:

[0019] In this invention, the oriented polypropylene matrix in the highly oriented polypropylene product has a high degree of orientation. Specifically, the degree of orientation of the oriented polypropylene matrix on the (040) crystal plane is less than or equal to -0.45, which makes the polypropylene product have high tensile strength and high flexural modulus.

[0020] Furthermore, in the preparation method of the highly oriented polypropylene product of the present invention, a die stretching method is used to stretch the sample containing oriented polypropylene, and a cooling treatment is performed at a specific cooling rate after stretching. This reduces the phenomenon of molecular chain entanglement and deorientation, and realizes the control of the orientation molecular chains in the oriented polypropylene, thereby further improving the orientation degree of the molecular chains in the polypropylene. This significantly improves the tensile strength and flexural modulus and other mechanical properties of the polypropylene product. In addition, this preparation method is simple and easy to implement. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The first aspect of this invention provides a highly oriented polypropylene article, characterized in that the highly oriented polypropylene article has the following features:

[0023] (a) Tensile strength greater than or equal to 110 MPa;

[0024] (b) Flexural modulus greater than or equal to 6 GPa;

[0025] (c) The orientation degree of the oriented polypropylene matrix in the (040) crystal plane of the polypropylene product is less than or equal to -0.45.

[0026] The highly oriented polypropylene products provided by this invention are prepared by die stretching. By controlling the process flow, process conditions, and temperature after stretching, the orientation of the molecular chains is controlled, thereby further improving the orientation degree of the molecular chains in the polypropylene products. This improves the tensile strength and other properties of the polypropylene products. The process is simple to control and easy to implement.

[0027] In this invention, the orientation degree of the oriented polypropylene matrix in the (040) crystal plane of the polypropylene product is tested by a wide-angle X-ray diffractometer and calculated according to the Hermans uniaxial orientation model.

[0028] In one specific embodiment of the present invention, the highly oriented polypropylene product has the following characteristics:

[0029] (a) Tensile strength greater than or equal to 120 MPa;

[0030] (b) Flexural modulus greater than or equal to 6.6 GPa;

[0031] (c) The orientation degree of the oriented polypropylene matrix in the (040) crystal plane of the polypropylene product is less than or equal to -0.46.

[0032] In one specific embodiment of the present invention, the oriented polymer article has the following characteristics:

[0033] (a) Tensile strength greater than or equal to 130 MPa;

[0034] (b) Flexural modulus greater than or equal to 6.7 GPa;

[0035] (c) The orientation degree of the oriented polypropylene matrix in the (040) crystal plane of the polypropylene product is less than or equal to -0.465.

[0036] According to the present invention, the polypropylene article comprises an oriented polypropylene matrix and additives;

[0037] Based on a total weight of 100 parts of polypropylene products, the content of the oriented polypropylene matrix is ​​98-99.9 parts, and the content of the additives is 0.1-2 parts.

[0038] Furthermore, based on 100 parts of the total weight of the polypropylene product, the content of the oriented polypropylene matrix is ​​99-99.9 parts, and the content of the additives is 0.1-1 parts.

[0039] In this invention, there is no particular limitation on the type of additives. They can be conventional additives used in the art to improve the performance of polypropylene products, such as antioxidants and UV stabilizers.

[0040] A second aspect of the present invention provides a method for preparing a highly oriented polymer article, characterized in that the preparation method includes the following steps:

[0041] (a) Orientable polypropylene and additives are mixed, granulated, and molded to obtain a pretreated sample; the orientable polypropylene is homopolymer polypropylene;

[0042] (b) The pretreated sample is subjected to die stretching and cooling treatment to obtain a highly oriented polypropylene product;

[0043] The cooling rate of the cooling process is greater than or equal to 5°C / min;

[0044] The cooling process begins at a distance of 0.1-30cm from the stretching die.

[0045] In this invention, the method for preparing highly oriented polypropylene products involves stretching a sample containing oriented polypropylene using a die stretching technique, followed by cooling at a specific rate. This ensures rapid fixation of the stretched oriented molecular chain segments, reducing molecular chain entanglement and deorientation. This allows for control over the oriented molecular chains in the oriented polypropylene, further enhancing the degree of molecular chain orientation and significantly improving the tensile strength and flexural modulus of the polypropylene products. Furthermore, this preparation method is simple and easy to implement.

[0046] In this invention, by further controlling the timing of the cooling process to meet the above requirements, the deorientation of the oriented polypropylene molecular chains can be further effectively controlled, thereby further improving the orientation degree of the oriented polypropylene in the polypropylene product, and thus further enhancing the tensile strength and flexural modulus of the polypropylene product.

[0047] In this invention, the inventors discovered that because copolymer polypropylene contains comonomers such as ethylene and butene, the oriented molecular chain segments formed during the stretching process are prone to movement, which leads to an unfavorable reduction in the orientation degree of the oriented polypropylene in the final polymer product. Therefore, in order to prepare polypropylene products with high orientation degree, the oriented polypropylene is homopolymer polypropylene.

[0048] In this invention, the distance from the stretching die refers to the distance between the polypropylene product and the die. Specifically, the distance from the die refers to the distance from the starting point of cooling to the point where the product leaves the stretching die.

[0049] In this invention, the cooling treatment reduces the temperature of the product after being stretched by the die from the stretching temperature to 70°C.

[0050] In this invention, the temperature of the product after being stretched by the die is reduced to 70°C, and then it is allowed to cool naturally to room temperature.

[0051] Furthermore, the cooling rate of the cooling process is 5-50℃ / min.

[0052] Furthermore, the cooling process is initiated at a distance of 0.5-20 cm from the stretching die.

[0053] In this invention, the cooling process is performed in the presence of tensile stress.

[0054] In this invention, the cooling process is carried out under tensile stress, which ensures continuous production and prevents the polypropylene products from disorienting.

[0055] In this invention, there is no particular limitation on the cooling method; conventional cooling methods in the art can be used, such as using refrigerant and / or physical cooling.

[0056] In this invention, the molding method of the pretreated sample includes, but is not limited to, extrusion molding, compression molding, injection molding, rotational molding, and other processing methods.

[0057] In this invention, there are no particular limitations on the mixing method and conditions of oriented polypropylene and additives. Conventional mixing equipment in the art, such as a twin-screw extruder, can be used to mix the materials. As for the mixing temperature, it is sufficient to ensure that the mixing temperature is above the softening point of oriented polypropylene.

[0058] According to the present invention, the stretching ratio of the die stretching is greater than or equal to 4 times, and the stretching temperature of the die stretching is 100-150℃.

[0059] In this invention, the stretching temperature refers to the temperature of the polymer product or pretreated sample during the stretching process. The stretching ratio is the ratio of the cross-sectional shape of the die used for stretching to the axial cross-sectional area of ​​the pretreated sample.

[0060] In this invention, during the die stretching process, the molecular chains of oriented polypropylene undergo orientation, which significantly improves the mechanical properties of the resulting polypropylene product. As the stretching ratio increases, the orientation degree of polypropylene increases, but this will cause the cross-sectional area of ​​the product to decrease and is prone to fiberization, which will have a great impact on the subsequent processing and application. Therefore, the stretching ratio should not be too high.

[0061] Specifically, when the stretching ratio and stretching temperature of the die stretching meet the above range, the resulting polypropylene product has a high degree of orientation, which in turn significantly improves the tensile strength and flexural modulus of the polypropylene product.

[0062] Furthermore, the stretching ratio of the die stretching is 4-20 times, and the stretching temperature of the die stretching is 100-145℃.

[0063] In this invention, there are no special requirements for the stretching rate, and it can be carried out according to the conventional stretching rate in the art. For example, the stretching rate of the die stretching is 25-1500 mm / min, preferably 50-1000 mm / min.

[0064] According to the present invention, based on 100 parts of the total weight of the highly oriented polypropylene product, the amount of the oriented polypropylene is 98-99.9 parts by weight, and the amount of the additive is 0.1-2 parts by weight.

[0065] Furthermore, based on a total weight of 100 parts of highly oriented polypropylene products, the amount of oriented polypropylene used is 99-99.9 parts, and the amount of additives used is 0.1-1 parts.

[0066] Furthermore, the melt flow index of the oriented polypropylene at 230°C and a load of 2.16 kg is 1-50 g / 10 min, preferably 3-50 g / 10 min.

[0067] In this invention, there is no particular limitation on the type of additives. They can be conventional additives used in the art to improve the performance of polypropylene products, such as antioxidants and UV stabilizers.

[0068] In one specific embodiment of the present invention, the adjuvant is an antioxidant.

[0069] In a preferred embodiment of the present invention, the adjuvant is antioxidant 1010 and antioxidant 168, wherein the mass ratio of antioxidant 1010 to antioxidant 168 is 1:0.1-3, preferably 1:0.5-2.

[0070] According to the present invention, the cross-sectional shape of the die for stretching is at least one of a circle, triangle, rectangle, rhombus, trapezoid, and polygon. The polygon can be of various shapes, such as I-shape, T-shape, etc.

[0071] In this invention, the minimum dimension of the die opening shape for die stretching is greater than or equal to 2 mm, preferably greater than or equal to 1.5 mm.

[0072] In this invention, the cross-sectional shape of the die head for stretching is the same as the cross-sectional shape perpendicular to the axial direction of the pretreated sample, and the two cross-sections are similar.

[0073] In this invention, the equipment used for die stretching includes: (a) a traction device, (b) a stretching die head, (c) a temperature control device, and (d) a cooling device.

[0074] The temperature control device is designed to ensure that the pretreated sample reaches the same temperature as the stretching die when it passes through the stretching die, and it has cooling or heating functions.

[0075] Cooling equipment: The function of the equipment is to cool the stretched product to below a specified temperature at a certain cooling rate.

[0076] A third aspect of the present invention provides an orientation polymer article prepared by the above-described preparation method.

[0077] A fourth aspect of the present invention provides the application of the above-mentioned oriented polymer article in building materials.

[0078] The present invention will be described in detail below through embodiments.

[0079] The experimental data for the examples and comparative examples were tested and calculated using the following methods:

[0080] (1) The density test method shall be carried out in accordance with GB / T 1033-1986 "Test Method for Density and Relative Density of Plastics".

[0081] (2) Tensile strength and tensile modulus were tested in accordance with GB / T1040-2006 "Determination of tensile properties of plastics".

[0082] (3) Bending strength and bending modulus were tested in accordance with GB / T9341-2008 "Determination of bending properties of plastics".

[0083] (4) Orientation degree: The orientation factor of the (040) crystal plane was calculated according to the Hermans uniaxial orientation model using a wide-angle X-ray diffractometer. This orientation factor represents the orientation degree of the crystal.

[0084] (5) Calculation of cooling rate: When the distance from the stretching die is 0.5 cm or less, the starting temperature of the product cooling is the temperature of the stretching die T, the time required for the product temperature to drop to 70℃ is t (min), and the cooling rate (℃ / min) = (T-70) / t; When the distance from the stretching die is more than 0.5 cm, the distance from the die is recorded as L (cm), the stretching rate is recorded as S (mm / min), the time required for the product temperature to drop to 70℃ is t1 (min), and the cooling rate (℃ / min) = (T-70) / (t1-L / S); In the comparative example without cooling treatment, the time required for the product temperature to drop to 70℃ is t2, the cooling rate (℃ / min) = (T-70) / t2, T (℃).

[0085] The experimental data for the examples and comparative examples were tested using the following instruments:

[0086] (1) Tensile strength, tensile modulus, flexural strength, flexural modulus: Instron universal testing machine, model 3366.

[0087] (2) D8 Discover wide-angle X-ray diffractometer from Bruker GmbH, Germany.

[0088] The raw material information for the examples and comparative examples is shown below:

[0089] Polypropylene A: K1008, homopolymer polypropylene, Yanshan Petrochemical, melt index 10g / 10min at 230℃ and load 2.16kg;

[0090] Polypropylene B: Y3700C, homopolymer polypropylene, Shanghai Petrochemical, melt index 37 g / 10 min at 230℃ and 2.16 kg load;

[0091] Polypropylene C: Y2600D, homopolymer polypropylene, Shanghai Petrochemical, melt index 26 g / 10 min at 230℃ and 2.16 kg load;

[0092] Polypropylene D: PPH-T03, homopolymer polypropylene, Zhenhai Refining & Chemical, melt index 3 g / 10 min at 230℃ and 2.16 kg load;

[0093] Polypropylene E: M800E, copolymer polypropylene, Shanghai Petrochemical, melt index 8 g / 10 min at 230℃ and 2.16 kg load;

[0094] Antioxidant: 1010, BASF;

[0095] Antioxidant: 168, BASF.

[0096] Example 1

[0097] (a) Orientable polypropylene matrix and additives were melt-mixed using a twin-screw extruder and then injection-molded to obtain a pretreated sample. The melt mixing temperature was 210°C and the rotation speed was 150 rpm. The sample contained 99.8 parts of orientable polypropylene matrix and 0.1 parts of additives (antioxidant 1010 and antioxidant 168). The injection molding conditions were: screw temperature 225°C, injection speed 15 mm / s, injection pressure 650 bar, holding time 60 s, and holding pressure 650 bar.

[0098] (b) The pretreated sample was subjected to die stretching and cooling treatment. After cooling to a surface temperature of 70°C, it was allowed to cool naturally to room temperature to obtain the highly oriented polypropylene product E1. The cooling rate and cooling method are shown in Table 1.

[0099] The types and amounts of oriented polypropylene matrix, and the amounts of antioxidant 1010 and antioxidant 168 are shown in Table 1. The process conditions for die stretching, the rate of cooling treatment, the distance from the die at the start of cooling, and the time required for the product temperature to drop to 70°C are shown in Table 2.

[0100] Example 2

[0101] Highly oriented polypropylene products were prepared according to the method of Example 1, except that the type and amount of oriented polypropylene matrix, and the amounts of antioxidant 1010 and antioxidant 168 were different from those in Example 1, as shown in Table 1.

[0102] The process conditions for die stretching, the rate of cooling treatment, the distance from the die at the start of cooling, and the time required for the product temperature to drop to 70°C are different from those in Example 1, as shown in Table 2.

[0103] High-curvature oriented polypropylene product E2 was obtained.

[0104] Example 3

[0105] Orientable polypropylene products were prepared according to Example 1, except that the type and amount of orientable polypropylene matrix, and the amounts of antioxidant 1010 and antioxidant 168 were different from those in Example 1, as shown in Table 1.

[0106] The process conditions for die stretching, the rate of cooling treatment, the distance from the die at the start of cooling, and the time required for the product temperature to drop to 70°C are different from those in Example 1, as shown in Table 2.

[0107] Example 4

[0108] High polypropylene product E4 was prepared according to the method of Example 1, except that polypropylene D was used instead of polypropylene A, and the amounts of polypropylene, antioxidant 1010 and antioxidant 168 were different from those in Example 1. For details, please refer to Table 1. The process conditions for die stretching, the rate of cooling treatment, the distance from the die at the beginning of cooling, and the time required for the product temperature to drop to 70°C are shown in Table 2.

[0109] Example 5

[0110] High polypropylene product E5 was prepared according to the method of Example 1, except that polypropylene D was used instead of polypropylene A, and the amounts of polypropylene, antioxidant 1010 and antioxidant 168 were different from those in Example 1. For details, please refer to Table 1. The process conditions for die stretching, the rate of cooling treatment, the distance from the die at the beginning of cooling, and the time required for the product temperature to drop to 70°C are shown in Table 2.

[0111] Comparative Example 1

[0112] Highly oriented polypropylene products were prepared according to the method of Example 1, except that the die stretching process conditions, the cooling rate, the distance from the die at the start of cooling, and the time required for the product temperature to drop to 70°C were different from those in Example 1, as shown in Table 2.

[0113] Oriented polypropylene product D1 was obtained.

[0114] Comparative Example 2

[0115] Oriented polymer article D2 was prepared according to the method of Example 1, except that polypropylene E was used instead of polypropylene A. Oriented polypropylene article D2 was obtained.

[0116] Comparative Example 3

[0117] Oriented polypropylene product D3 was prepared according to the method of Example 1, except that the distance from the die was 40 cm.

[0118] Table 1

[0119]

[0120]

[0121] Table 2

[0122]

[0123] * indicates that the starting point of cooling is 0cm away from where the product leaves the stretching die.

[0124] T 拉 -70℃ indicates that the product temperature has been reduced from the stretching temperature to 70℃.

[0125] The properties of the polypropylene products prepared in the examples and comparative examples were tested, and the results are shown in Table 3.

[0126] Table 3

[0127] Serial Number Tensile strength (MPa) Flexural modulus GPa Orientation E1 118 6.6 -0.455 E2 123 6.7 -0.465 E3 136 7.4 -0.468 E4 398 17.8 -0.475 E5 390 17.2 -0.471 E6 385 16.7 -0.470 E7 123 6.8 -0.466 D1 107 5.8 -0.431 D2 113 5.1 -0.447 D3 110 6.0 0.439

[0128] As can be seen from Tables 2 and 3, compared with Comparative Examples 1-3, the polypropylene products provided in Examples 1-7 of the present invention have high orientation, high tensile strength, and high flexural modulus. In Examples 1-7 of the present invention, when the orientable polypropylene is die-stretched, a specific cooling rate of 120717 is applied at an appropriate time.

[0129] I80136BHY

[0130] Cooling the polypropylene product at a certain temperature can result in a polypropylene product with high orientation, high tensile strength, and high flexural modulus.

[0131] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A highly oriented polypropylene product, characterized in that, The highly oriented polypropylene product has the following characteristics: (a) Tensile strength greater than or equal to 110 MPa; (b) Flexural modulus greater than or equal to 6 GPa; (c) The orientation degree of the oriented polypropylene matrix in the (040) crystal plane of the polypropylene product is less than or equal to -0.

45.

2. The highly oriented polypropylene product according to claim 1, wherein, The highly oriented polypropylene product has the following characteristics: (a) Tensile strength is greater than or equal to 120 MPa, preferably greater than or equal to 130 MPa; (b) Flexural modulus greater than or equal to 6.6 GPa, preferably greater than or equal to 6.7 GPa; (c) In polypropylene products, the orientation degree of the oriented polypropylene matrix on the (040) crystal plane is less than or equal to -0.46, preferably less than or equal to -0.

465.

3. The highly oriented polypropylene article according to claim 1 or 2, wherein, The polypropylene product comprises an oriented polypropylene matrix and additives; Based on 100 parts of the total weight of the polypropylene product, the content of the oriented polypropylene matrix is ​​98-99.9 parts, preferably 99-99.9 parts, and the content of the additives is 0.1-2 parts, preferably 0.1-1 parts.

4. A method for preparing a highly oriented polypropylene article according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: (a) Orientable polypropylene and additives are mixed and molded to obtain a pretreated sample; the orientable polypropylene is homopolymer polypropylene; (b) The pretreated sample is subjected to die stretching and cooling treatment to obtain a highly oriented polypropylene product; The cooling rate of the cooling process is greater than or equal to 5°C / min; The cooling process begins at a distance of 0.1-30cm from the stretching die.

5. The preparation method according to claim 4, wherein, The cooling rate of the cooling process is 5-50℃ / min; Preferably, the cooling process is started at a distance of 0.5-20 cm from the stretching die; Preferably, the cooling process is performed using a refrigerant and / or physical cooling.

6. The preparation method according to claim 4 or 5, wherein, The stretching ratio of the die is greater than or equal to 4 times, preferably 4-20 times; Preferably, the stretching temperature of the die stretching is 100-150℃, and more preferably 100-145℃.

7. The preparation method according to any one of claims 4-6, wherein, Based on 100 parts of the total weight of the highly oriented polypropylene product, the amount of the oriented polypropylene is 98-99.9 parts by weight, preferably 99-99.9 parts, and the amount of the additive is 0.1-2 parts by weight, preferably 0.1-1 parts. Preferably, the oriented polypropylene has a melt flow index of 1-50 g / 10 min at 230°C and a load of 2.16 kg, and more preferably 3-50 g / 10 min.

8. The preparation method according to any one of claims 4-7, wherein, The die opening shape for the stretching die is at least one of the following: circular, triangular, rectangular, rhomboid, trapezoidal, and polygonal.

9. A highly oriented polypropylene article prepared by the preparation method according to any one of claims 4-8.

10. The use of the highly oriented polypropylene product according to any one of claims 1-3 and 9 in building decoration.

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