Polypropylene composition as well as preparation method and application thereof

Abstract

The invention relates to a polypropylene composition as well as a preparation method and application thereof. The polypropylene composition comprises 39-66 parts of polypropylene resin, 2-6 parts of a compatilizer, 3-8 parts of a bamboo fiber filler, 5-13 parts of a glass fiber filler and 0-5 parts of a processing aid. The polypropylene composition is suitable for being co-extruded with nylon to prepare a pipe, and the interlayer binding force between the polypropylene composition and a nylon interface is effectively improved by utilizing the characteristic that hydroxyl groups of the bamboo fiber filler in the polypropylene composition and nylon form hydrogen bonds and matching of the glass fiber filler.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and more specifically, to a polypropylene composition and a preparation method and application thereof. Background Art

[0002] Polypropylene is widely used in industrial and consumer products due to its good chemical resistance, mechanical properties and thermal properties. Polypropylene composite is a material composed of polypropylene and various additives, which is commonly used to manufacture various products such as plastic containers, pipes and automotive parts.

[0003] When producing a fuel filler pipe, if a polypropylene composition and nylon are co-extruded, the bonding force at the interface of the polypropylene composition and nylon is weak due to the large difference in polarity between the polypropylene composition and nylon, resulting in the formation of an interface layer between the polypropylene composition and nylon, thereby reducing the performance of the fuel filler pipe. In order to overcome this problem, it is usually necessary to add an intermediate layer material, such as polyethylene grafted maleic anhydride or polypropylene grafted maleic anhydride compatibilizer. These compatibilizers have high polarity and can effectively combine the polypropylene composition and nylon, thereby improving the performance of the fuel filler pipe.

[0004] In addition, there are also studies on using compatibilizers to modify polymers to improve the bonding strength of polypropylene and nylon (polyamide), such as the Chinese patent titled "A modified polyamide composite film and its preparation method", which discloses a method for preparing a modified polyamide, which improves the interlayer bonding strength of polyamide and polypropylene composite films. However, when the polypropylene composition is used to co-extrude with nylon to prepare pipes, the bonding strength of the two still needs to be improved. Summary of the invention

[0005] The primary purpose of the present invention is to overcome the problem that the bonding strength between the interface of the polypropylene composition and nylon used for co-extrusion with nylon to prepare pipes still needs to be improved, and to provide a polypropylene composition.

[0006] A further object of the present invention is to provide a method for preparing the above polypropylene composition.

[0007] A further object of the present invention is to provide the use of the above polypropylene composition in the preparation and co-extrusion processing of nylon.

[0008] A further object of the present invention is to provide a tube.

[0009] The above-mentioned object of the present invention is achieved by the following technical solutions:

[0010] A polypropylene composition comprises the following components by weight: 39-66 parts of polypropylene resin, 2-6 parts of compatibilizer, 3-8 parts of bamboo fiber filler, 5-13 parts of glass fiber filler and 0-5 parts of processing aid.

[0011] Polypropylene composition of the present invention comprises polypropylene resin, compatibilizer, bamboo fiber filler, glass fiber filler and processing aid, and the polypropylene composition is used for preparing pipe by coextrusion with nylon, and can effectively improve the bonding force of polypropylene composition and nylon interface, and then improve the durability of pipe. Wherein, bamboo fiber filler contains thick-walled fiber and fine fiber, and its microfibril is horizontally arranged into several layers, has higher strength and wear resistance, and can increase the mechanical properties (such as tensile and impact resistance) of polypropylene composition. Under high temperature and high pressure conditions, bamboo fiber filler can still maintain good stability, and in the coextrusion process of polypropylene composition and nylon, the addition of bamboo fiber filler can improve the fluidity and forming performance of polypropylene composition, makes the coextrusion process smoother, thereby makes the bonding between polypropylene composition and nylon interface more stable. Bamboo fiber filler also contains abundant hydroxyl, and the hydroxyl of bamboo fiber filler can form hydrogen bond with nylon, and this hydrogen bonding effect helps to improve the bonding force of polypropylene composition and nylon interface. Moreover, since the hydroxyl groups of the bamboo fiber filler have been fully acted upon by nylon, the water absorption of the bamboo fiber filler is greatly reduced, which is beneficial to reducing the water absorption of the pipe and improving the durability of the refueling pipe.

[0012] At the same time, too much bamboo fiber filler and glass fiber filler will cause the polypropylene composition to become hard and brittle, affecting the processing and flow properties, and further affecting the good bonding between the polypropylene composition and nylon; too little filler may not provide sufficient reinforcement effect, resulting in a decrease in the overall strength of the polypropylene composition, affecting the bonding between the polypropylene composition and nylon.

[0013] The applicant has found that if the content of bamboo fiber filler and glass fiber filler in the polypropylene composition is too low, the bonding force between the polypropylene composition and nylon will be reduced. If the content of polypropylene resin is too low, the processing stability will be affected, so that more gaps are formed between the bonding interface of the polypropylene composition and nylon, resulting in a reduction in contact area and a reduction in the bonding force between the polypropylene composition and nylon.

[0014] The amount of the polypropylene resin can be 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, or 65 parts.

[0015] Preferably, in the present invention, the polypropylene resin is used as the main resin, and its content accounts for 55 wt % of the polypropylene composition.

[0016] Preferably, the melt flow rate of the polypropylene resin measured at 230° C. and 2.16 kg is 0.3 to 5 g / 10 min.

[0017] In the present invention, the melt flow rate of the polypropylene resin can be measured according to ISO 1133-1:2011.

[0018] Preferably, the polypropylene resin is homopolypropylene or a mixture of homopolypropylene and random copolymer polypropylene.

[0019] More preferably, the polypropylene resin is a mixture of homopolypropylene and random copolymer polypropylene, and the mass ratio of the homopolypropylene to the random copolymer polypropylene is 1:(0.2-0.4).

[0020] Compared with other polypropylene resins, random copolymer polypropylene has higher flexibility and can be used to manufacture pipes that require better strength and durability. Adding some random copolymer polypropylene as part of the polypropylene resin can make the polypropylene composition have better processing performance during the co-extrusion production process.

[0021] More preferably, the ethylene content in the random copolymer polypropylene is below 3 wt % (eg, 1 to 3 wt %).

[0022] Preferably, the compatibilizer is a maleic anhydride grafted compatibilizer.

[0023] More preferably, the grafting rate of maleic anhydride in the maleic anhydride grafted compatibilizer is 0.5 to 2 wt%.

[0024] The grafting rate of maleic anhydride in the maleic anhydride grafted compatibilizer can be measured by acid-base titration.

[0025] More preferably, the compatibilizer is at least one of polyethylene grafted maleic anhydride or polypropylene grafted maleic anhydride.

[0026] Further preferably, the mass ratio of the polyethylene grafted maleic anhydride to the polypropylene grafted maleic anhydride is (0.5-1):1.

[0027] The maleic anhydride functional group in the compatibilizer can interact with the surface of the polypropylene resin and the filler to form a bond, effectively improving the compatibility of the polypropylene resin and the filler, enhancing the adhesion and miscibility of the two, thereby achieving a good combination of the polypropylene composition and the nylon interface and improving the durability of the pipe. The composite use of polyethylene grafted maleic anhydride and polypropylene grafted maleic anhydride can make the bonding between the polypropylene composition and the nylon interface better.

[0028] The amount of the bamboo fiber filler can be 3 parts, 4 parts, 5 parts, 6 parts, 7 parts or 8 parts.

[0029] Preferably, the average cross-sectional diameter of the bamboo fiber filler is 70-150 μm.

[0030] In the present invention, the average diameter of the cross section of the bamboo fiber filler can be measured by optical microscopy.

[0031] More preferably, the average cross-sectional diameter of the bamboo fiber filler is 100-130 μm. By selecting the bamboo fiber filler with this average diameter, the obtained polypropylene composition has better bonding strength when co-extruded with nylon.

[0032] The amount of the glass fiber filler can be 5 parts, 7 parts, 9 parts, 11 parts, or 13 parts.

[0033] Preferably, the glass fiber filler is an alkali-free glass fiber filler.

[0034] Preferably, the average cross-sectional diameter of the glass fiber filler is 5 to 15 μm.

[0035] In the present invention, the average cross-sectional diameter of the glass fiber filler can be measured by optical microscopy.

[0036] Bamboo fiber fillers with larger average diameters can provide more filling volume, which helps improve the shock absorption and impact resistance of the fuel filler pipe. At the same time, glass fiber fillers with smaller average diameters can provide good strength and rigidity, enhancing the tensile strength and wear resistance of the fuel filler pipe. The combination of fillers with different average diameters can achieve a complementary effect between fillers, making the fuel filler pipe perform better in terms of mechanical properties, durability and engineering applications.

[0037] Preferably, the average length of the glass fiber filler is 3.0-4.0 mm.

[0038] In the present invention, the average length of the glass fiber filler can be measured by optical microscopy.

[0039] Preferably, the average length of the bamboo fiber filler is 4.0-6.0 mm.

[0040] In the present invention, the average length of the bamboo fiber filler can be measured by optical microscopy.

[0041] Preferably, the moisture content of the bamboo fiber filler is ≤5wt%, for example, it may be 5wt%, 3wt%, 1wt%, 0.5wt%, 0.15wt%, 0.1wt%, 0.05wt% and the like.

[0042] More preferably, the moisture content of the bamboo fiber filler is ≤0.15wt%.

[0043] The commercially available bamboo fiber filler can meet the bonding strength requirement of the polypropylene composition of the present invention for co-extrusion with nylon to prepare pipes. Further drying the commercially available bamboo fiber filler to reduce the moisture content of the bamboo fiber filler can effectively improve the bonding between the bamboo fiber filler and the polymer matrix, prevent the bamboo fiber filler from absorbing water, and enable the polypropylene composition and nylon interface to form a stronger bonding strength.

[0044] In the present invention, the test method of the moisture content of the bamboo fiber filler is as follows: randomly select a certain amount of samples from the bamboo fiber filler after drying treatment to ensure that the samples are representative, and record the initial mass m1 of the samples; put the samples into an oven preheated to the corresponding drying treatment temperature, and dry them until the mass of the samples is constant (that is, the mass difference between two consecutive weighings does not exceed the specified value, such as 0.001g); take the dried samples out of the oven, put them into a dryer and cool them to room temperature; use an electronic balance to weigh the mass m2 of the cooled samples; and calculate the moisture content by the following formula: moisture content = [(m1-m2) / m1]×100%.

[0045] Preferably, the processing aid comprises a lubricant and / or a β-crystal nucleating agent.

[0046] More preferably, the amount of the lubricant is 2 to 4 parts, and the amount of the β-crystal nucleating agent is 1 to 2 parts.

[0047] More preferably, the lubricant is at least one of zinc stearate, calcium stearate or polypropylene wax.

[0048] More preferably, the processing aid further comprises phosphoric acid. More preferably, the phosphoric acid is present in an amount of 0.5 to 1.8 parts.

[0049] By adding an appropriate amount of phosphoric acid to the polypropylene composition, the flame retardant properties of the pipe prepared therefrom can be significantly improved, and the burning speed and flame propagation speed of the pipe can be reduced. This is particularly important for products that need to be used in high temperature or flammable environments, and can improve the safety and reliability of the product. In addition, phosphoric acid, as a processing aid, can not only improve the fluidity and solubility of the polypropylene composition, but also improve the processing properties of the polypropylene composition. Adding an appropriate amount of phosphoric acid can reduce the melting temperature and viscosity of the polypropylene composition, reduce the friction resistance of the melt during extrusion, and in the co-extrusion process of the polypropylene composition and nylon, make the bonding interface of the polypropylene composition and nylon contact more fully, thereby improving the bonding force of the polypropylene composition and the nylon interface. Moreover, phosphoric acid also has a certain reinforcing agent effect, which can improve the strength of the polypropylene composition, improve the overall performance of the refueling pipe prepared therefrom, make the tensile strength and impact resistance of the refueling pipe better, and improve the service life and stability of the refueling pipe.

[0050] The method for preparing the polypropylene composition comprises the following steps:

[0051] The polypropylene resin and the compatibilizer are mixed evenly to obtain a first premix; the bamboo fiber filler, the glass fiber filler and the processing aid are added to the first premix and mixed evenly to obtain a second premix; the second premix is ​​added to the main feed port of the extrusion equipment, and the polypropylene composition is obtained through melt blending, extrusion granulation and drying.

[0052] Preferably, the extrusion temperature of the extrusion equipment is 200-240°C.

[0053] The use of the above polypropylene composition in the preparation of a fuel filler pipe also falls within the protection scope of the present invention.

[0054] A tube comprises a first layer and a second layer arranged adjacent to each other, wherein the first layer and the second layer are formed by a co-extrusion process, the first layer is nylon, and the second layer is the above-mentioned polypropylene composition.

[0055] Preferably, the pipe is a refueling pipe.

[0056] Preferably, the nylon is at least one of nylon 6 or nylon 12.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] The polypropylene composition of the present invention comprises polypropylene resin, compatibilizer, bamboo fiber filler, glass fiber filler and processing aid. The polypropylene composition is used for preparing pipes by co-extrusion with nylon. The characteristics of the hydroxyl groups of the bamboo fiber filler in the polypropylene composition forming hydrogen bonds with nylon and the combination of the glass fiber filler are utilized to effectively improve the bonding force of the interface between the polypropylene composition and nylon, and eliminate the need for the intermediate layer material in the co-extrusion process of the fuel pipe; in addition, the full effect of the bamboo fiber filler and nylon is conducive to reducing the water absorption of the overall material, thereby improving the durability of the fuel pipe. DETAILED DESCRIPTION

[0059] In order to more clearly and completely describe the technical solution of the present invention, the present invention is further described in detail through specific embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention. Various changes can be made within the scope of the rights of the present invention.

[0060] Some of the reagents selected in the embodiments and comparative examples of the present invention are described as follows:

[0061] 1. Polypropylene resin

[0062] Homopolymer polypropylene 1: Model: PPH-T03, melt flow rate (230℃ / 2.16kg): 3.0g / 10min, manufacturer: Sinochem Refining & Chemical.

[0063] Homopolymer polypropylene 2: Model: B1101, melt flow rate (230°C / 2.16kg): 0.5g / 10min, manufacturer: Formosa Chemical Corporation.

[0064] Random copolymer polypropylene: model is SM 198, melt flow rate (230°C / 2.16kg) is 1.6g / 10min, and the manufacturer is Lotte of South Korea.

[0065] 2. Compatibilizer

[0066] Polypropylene grafted maleic anhydride (PP-g-MAH): model CMG9801, manufacturer Jiayirong, grafting rate 0.5-1.0%.

[0067] Polyethylene grafted maleic anhydride (PE-g-MAH): model CMG5804, manufacturer Jiayirong, grafting rate 0.5-1.0%.

[0068] 3. Bamboo fiber filler

[0069] Bamboo fiber filler 1: Model is ZX85, moisture content is 3-5wt%, average diameter is 85μm, manufacturer is Yunding.

[0070] Bamboo fiber filler 2: model is ZX125, moisture content is 3-5wt%, average diameter is 125μm, manufacturer is Yunding.

[0071] Bamboo fiber filler 3: The bamboo fiber filler 1 is dried, with an average diameter of 85 μm and a moisture content of 0.1 wt%.

[0072] Bamboo fiber filler 4: model is ZX95, moisture content is 3-5wt%, average diameter is 95μm, manufacturer is Yunding.

[0073] 4. Glass fiber filler

[0074] Glass fiber filler 1: Model is BF2515, average diameter is 7μm, manufacturer is Jushi.

[0075] Glass fiber filler 2: Model is BF6045, average diameter is 12μm, manufacturer is Jushi.

[0076] 5. Processing aids

[0077] β-crystal nucleating agent: model is NP-328, manufacturer is Ji Haichuan.

[0078] Lubricant: Zinc stearate, manufactured by Huijinchuan Chemical.

[0079] Phosphoric acid: The manufacturer is Yongsheng Chemical.

[0080] 6. Other raw materials

[0081] Other plant fibers: pine wood powder, 80 mesh, moisture content 1wt%, manufactured by Lingshou County Yongshun Mineral Products Processing Plant;

[0082] Other fillers: talcum powder, 1250 mesh, Guangxi Longsheng Golden Monkey brand;

[0083] The preparation method of the polypropylene composition of each embodiment and comparative example of the present invention comprises the following steps:

[0084] The polypropylene resin and the compatibilizer are mixed uniformly by weight to obtain a first premix; the bamboo fiber filler, the glass fiber filler and the processing aid are added to the first premix and mixed uniformly to obtain a second premix; the second premix is ​​added to the main feed port of the extrusion equipment, and the polypropylene composition is obtained through melt blending, extrusion granulation and drying; wherein the extrusion temperature of the extrusion equipment is 200-240°C.

[0085] Examples 1 to 12

[0086] This embodiment provides a series of polypropylene compositions, and the weight proportions of the components in the formulations are shown in Tables 1 and 2.

[0087] Table 1 Formulas of Examples 1 to 7 (parts)

[0088] Example 1 2 3 4 5 6 7 Homopolymer polypropylene 1 55 / 55 55 55 55 55 Homopolymer polypropylene 2 / 55 / / / / / Random copolymer polypropylene / / / / / / / PP-g-MAH 4.5 4.5 / 4.5 4.5 4.5 4.5 PE-g-MAH / / 4.5 / / / / Bamboo fiber filling1 6 6 6 / / / 6 Bamboo fiber filling 2 / / / 6 / / / Bamboo fiber filling 3 / / / / 6 / / Bamboo fiber filling 4 / / / / / 6 / Glass fiber filler 1 9 9 9 9 9 9 / Glass fiber filler 2 / / / / / / 9 Lubricants 2 2 2 2 2 2 2 β-crystal nucleating agent 2 2 2 2 2 2 2 Phosphoric acid / / / / / / /

[0089] Table 2 Formulations of Examples 8 to 12 (parts)

[0090]

[0091]

[0092] Comparative Examples 1 to 8

[0093] This comparative example provides a series of polypropylene compositions, and the weight proportions of the components in the formulations are shown in Table 3.

[0094] Table 3 Formulas of Comparative Examples 1 to 8 (parts)

[0095] Comparative Example 1 2 3 4 5 6 7 8 Homopolymer polypropylene 1 55 55 55 55 55 55 55 55 PP-g-MAH 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 Bamboo fiber filling1 15 1 / 6 6 6 6 / Other plant fibers / / / / / / / 6 Glass fiber filler 1 9 9 9 18 2 / / 9 Other fillers / / / / / / 9 / Lubricants 2 2 2 2 2 2 2 2 β-crystal nucleating agent 2 2 2 2 2 2 2 2

[0096] Performance Testing

[0097] The polypropylene compositions of Examples 1 to 12 and Comparative Examples 1 to 8 were respectively used to co-extrude with nylon (PA6, Lotte, BL5400H) to prepare fuel filler pipes. The polypropylene compositions of each example and comparative example and the fuel filler pipes were tested according to the following performance test methods and standards. The test results are shown in Table 4.

[0098] The inner layer of the refueling pipe is nylon, and the outer layer is the polypropylene composition of Examples 1 to 12 and Comparative Examples 1 to 8, respectively. The pipe diameter is 15 mm, the outer layer thickness is 1.0 mm, and the inner layer thickness is 0.8 mm.

[0099] (1) Tensile strength: tested in accordance with ISO 527-2-2016 standard, with a tensile speed of 50 mm / min;

[0100] (2) Izod notched impact strength: tested in accordance with ISO 180-2000;

[0101] (3) Water absorption rate of the fuel filler pipe: The inside of the fuel filler pipe is sealed, and only the outside is exposed to the outside, and then immersed in water at 23°C for 20 days; water absorption rate (%) = (M1-M0) / M0×100%, where M0 is the mass before immersion and M1 is the mass after immersion;

[0102] (4) Bonding strength of the inner and outer layers of the fuel filler pipe: Cut the fuel filler pipe into two parts, use a tool to pry the inner and outer layers apart, clamp the pried apart parts with the fixture of a universal tensile testing machine, and gradually apply tensile force at a stretching speed of 5 mm / min. Record the tensile force as the bonding strength of the inner and outer layers of the fuel filler pipe.

[0103] Table 4 Performance test results of various embodiments and comparative examples

[0104]

[0105] As can be seen from Table 4, the polypropylene compositions prepared in Examples 1 to 12 of the present invention all have high mechanical properties, and the refueling tubes prepared by co-extrusion with nylon all have low water absorption and high bonding strength. The amount of bamboo fiber filler in the polypropylene composition of Comparative Example 1 is too much, and the water absorption of the refueling tube prepared therefrom is high and the bonding strength is low; the amount of bamboo fiber filler in the polypropylene composition of Comparative Example 2 is too little, and the tensile strength of the polypropylene composition is lower than that of Example 1, and the bonding strength of the refueling tube prepared therefrom is low; the polypropylene composition of Comparative Example 3 does not contain bamboo fiber filler, and the tensile strength of the polypropylene composition is lower than that of Example 1, and the bonding strength of the refueling tube prepared therefrom is low.

[0106] In Comparative Example 4, the amount of glass fiber filler used in the polypropylene composition is too much, and the tensile strength of the polypropylene composition is high, but the water absorption rate of the fuel filler pipe made therefrom is high and the bonding strength is low; in Comparative Example 5, the amount of glass fiber filler used in the polypropylene composition is too little, and the tensile strength of the polypropylene composition is low, and the bonding strength of the fuel filler pipe made therefrom is low; in Comparative Example 6, no glass fiber filler is added to the polypropylene composition, and the tensile strength of the polypropylene composition is low, and the bonding strength of the fuel filler pipe made therefrom is low.

[0107] In Comparative Example 7, other inorganic fillers are used to replace glass fiber fillers, and the water absorption rate of the refueling pipe made of the obtained polypropylene composition is higher, and the bonding force is lower. In Comparative Example 8, other plant fibers are used to replace bamboo fiber fillers, and the water absorption rate of the refueling pipe made of the obtained polypropylene composition is higher, and the bonding force is lower.

[0108] It is shown that the polypropylene composition of the present invention is used for co-extrusion with nylon to prepare a fuel filler pipe. By combining a certain proportion of bamboo fiber filler and glass fiber filler, the bonding strength of the interface between the polypropylene composition and nylon is effectively improved, eliminating the need for an intermediate layer material in the fuel filler pipe co-extrusion process; in addition, the full effect of the bamboo fiber filler and nylon is conducive to reducing the water absorption of the overall material, thereby improving the durability of the fuel filler pipe.

[0109] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A polypropylene composition, characterized in that The invention comprises the following components in parts by weight: 39-66 parts of polypropylene resin, 2-6 parts of compatibilizer, 3-8 parts of bamboo fiber filler, 5-13 parts of glass fiber filler and 0-5 parts of processing aid.

2. The polypropylene composition according to claim 1, characterized in that The polypropylene resin is homopolypropylene or a mixture of homopolypropylene and random copolymer polypropylene.

3. The polypropylene composition according to claim 1, characterized in that: The compatibilizer is a maleic anhydride grafted compatibilizer.

4. The polypropylene composition according to claim 1, characterized in that: The average cross-sectional diameter of the bamboo fiber filler is 70-150 μm.

5. The polypropylene composition according to claim 1, characterized in that: The moisture content of the bamboo fiber filler is ≤5wt%.

6. The polypropylene composition according to claim 1, characterized in that: The processing aid comprises a lubricant and a β-crystal nucleating agent.

7. The polypropylene composition according to claim 6, characterized in that: The processing aid also includes phosphoric acid.

8. The method for preparing the polypropylene composition according to any one of claims 1 to 7, characterized in that: The steps include: The polypropylene resin and the compatibilizer are mixed evenly to obtain a first premix; the bamboo fiber filler, the glass fiber filler and the processing aid are added to the first premix and mixed evenly to obtain a second premix; the second premix is ​​added to the main feed port of the extrusion equipment, and the polypropylene composition is obtained through melt blending, extrusion granulation and drying.

9. Use of the polypropylene composition according to any one of claims 1 to 7 in co-extrusion processing with nylon.

10. A tube, characterized in that The invention comprises a first layer and a second layer arranged adjacent to each other, wherein the first layer and the second layer are formed by a co-extrusion process, the first layer is nylon, and the second layer is the polypropylene composition according to any one of claims 1 to 7.

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