Polypropylene composition, process for its preparation and use thereof

Abstract

The present application relates to a kind of polypropylene composition and its preparation method and application.The polypropylene composition includes polypropylene resin 39-66 parts, compatible agent 2-6 parts, bamboo fiber filler 3-8 parts, glass fiber filler 5-13 parts and processing aid 0-5 parts.The polypropylene composition is suitable for and nylon co-extrusion preparation pipe material, utilizes the characteristics that the hydroxyl of bamboo fiber filler in polypropylene composition forms hydrogen bond with nylon and the cooperation of glass fiber filler, effectively improves the interlaminar binding force between polypropylene composition and nylon interface.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, and more specifically, to a polypropylene composition, its preparation method, and its application. Background Technology

[0002] Polypropylene possesses excellent chemical resistance, mechanical properties, and thermal properties, making it widely used in both industrial and consumer goods sectors. Polypropylene compositions are materials composed of polypropylene and various additives, commonly used in the manufacture of various products such as plastic containers, pipes, and automotive parts.

[0003] When manufacturing fuel filler hoses, if a polypropylene composition and nylon are co-extruded, the significant difference in polarity between the two materials results in weak interfacial bonding, leading to the formation of an interfacial layer that degrades the hose's performance. To overcome this issue, an intermediate layer material, such as polyethylene grafted with maleic anhydride or polypropylene grafted with maleic anhydride compatibilizer, is typically added. These compatibilizers have high polarity and can effectively bond the polypropylene composition and nylon, thereby improving the fuel filler hose's performance.

[0004] In addition, some studies have used compatibilizers to modify polymers and improve the bonding strength between polypropylene and nylon (polyamide). For example, a Chinese patent entitled "A Modified Polyamide Composite Film and Its Preparation Method" discloses a method for preparing modified polyamide, which improves the interlayer bonding strength of the polyamide and polypropylene composite film. However, when polypropylene compositions are used to co-extrude with nylon to prepare pipes, the bonding strength between the two still needs to be improved. Summary of the Invention

[0005] The primary objective of this invention is to overcome the problem that the bonding strength between the polypropylene composition and the nylon interface in existing polypropylene compositions used for co-extrusion of pipes with nylon 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-described polypropylene composition.

[0007] A further object of the present invention is to provide the application of the above-described 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 objective of the present invention is achieved through the following technical solution:

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

[0011] The polypropylene composition of this invention comprises polypropylene resin, a compatibilizer, bamboo fiber filler, glass fiber filler, and processing aids. This polypropylene composition is used for co-extrusion with nylon to prepare pipes, effectively improving the bonding strength between the polypropylene composition and the nylon interface, thereby enhancing the durability of the pipe. The bamboo fiber filler contains thick-walled fibers and fine fibers, with its microfibers arranged horizontally in several layers, exhibiting high strength and abrasion resistance, and increasing the mechanical properties of the polypropylene composition (such as tensile and impact resistance). Under high temperature and high pressure conditions, the bamboo fiber filler maintains good stability. During the co-extrusion process of the polypropylene composition and nylon, the addition of the bamboo fiber filler improves the flowability and molding properties of the polypropylene composition, making the co-extrusion process smoother, thus resulting in more stable adhesion between the polypropylene composition and the nylon interface. The bamboo fiber filler also contains abundant hydroxyl groups, which can form hydrogen bonds with nylon. This hydrogen bonding helps to improve the bonding strength between the polypropylene composition and the nylon interface. Furthermore, since the hydroxyl groups of the bamboo fiber filler have been fully utilized by the nylon, the water absorption of the bamboo fiber filler is greatly reduced, which helps to reduce the water absorption of the pipe and improve the durability of the refueling pipe.

[0012] Meanwhile, excessive bamboo fiber and glass fiber fillers can cause the polypropylene composition to become hard and brittle, affecting processing and flow properties, and consequently affecting the good bonding between the polypropylene composition and nylon; insufficient fillers may not provide enough reinforcement, resulting in a decrease in the overall strength of the polypropylene composition and affecting the bonding force between the polypropylene composition and nylon.

[0013] The applicant discovered that if the content of bamboo fiber filler and glass fiber filler in the polypropylene composition is too low, it will reduce the bonding strength between the polypropylene composition and nylon. If the content of polypropylene resin is too low, it will affect the processing stability, resulting in more gaps at the bonding interface between the polypropylene composition and nylon, leading to a reduction in the contact area and thus reducing the bonding strength between the polypropylene composition and nylon.

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

[0015] Preferably, in this invention, 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 0.3–5 g / 10 min.

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

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

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

[0020] Compared to other polypropylene resins, random copolymer polypropylene exhibits higher flexibility, making it suitable for manufacturing pipes requiring superior strength and durability. Adding a portion of random copolymer polypropylene as part of the polypropylene resin composition can enhance the processing performance of the polypropylene composition during co-extrusion production.

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

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

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

[0024] The grafting rate of maleic anhydride in maleic anhydride-grafted compatibilizers can be determined by acid-base titration.

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

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

[0027] The maleic anhydride functional groups in the compatibilizer can interact with the surfaces of polypropylene resin and fillers to form bonds, effectively improving the compatibility of polypropylene resin and fillers, enhancing their adhesion and miscibility, thereby achieving a good bond between the polypropylene composition and the nylon interface and improving the durability of the pipe. The combined use of polyethylene grafted with maleic anhydride and polypropylene grafted with maleic anhydride can further enhance the bonding strength between the polypropylene composition and the nylon interface.

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

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

[0030] In this 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. Selecting bamboo fiber filler with this average diameter results in better bonding strength between the resulting polypropylene composition and nylon during co-extrusion.

[0032] The amount of 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 glass fiber filler has an average cross-sectional diameter of 5–15 μm.

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

[0036] Bamboo fiber fillers with a larger average diameter can provide more filling volume, helping to improve the shock absorption and impact resistance of the refueling hose. Meanwhile, glass fiber fillers with a smaller average diameter provide good strength and rigidity, enhancing the tensile strength and wear resistance of the refueling hose. Combinations of fillers with different average diameters can achieve complementary effects, resulting in superior performance in mechanical properties, durability, and engineering applications for the refueling hose.

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

[0038] In this 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 to 6.0 mm.

[0040] In this 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%, such as 5wt%, 3wt%, 1wt%, 0.5wt%, 0.15wt%, 0.1wt%, 0.05wt%, etc.

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

[0043] Commercially available bamboo fiber fillers can meet the bonding strength requirements of the polypropylene composition of this invention for co-extruding with nylon to prepare pipes. Further drying the commercially available bamboo fiber fillers to reduce their moisture content can effectively improve the bonding between the bamboo fiber fillers and the polymer matrix, prevent water absorption by the bamboo fiber fillers, and enable a stronger bonding force to form between the polypropylene composition and the nylon interface.

[0044] In this invention, the method for testing the moisture content of bamboo fiber filler is as follows: a certain amount of sample is randomly selected from the dried bamboo fiber filler to ensure that the sample is representative, and the initial mass m1 of the sample is recorded; the sample is placed in an oven preheated to the corresponding drying temperature and dried until the sample mass is constant (i.e., the difference in mass between two consecutive weighings does not exceed a specified value, such as 0.001g); the dried sample is taken out of the oven and placed in a desiccator to cool to room temperature; the mass m2 of the cooled sample is weighed using an electronic balance; the moisture content is calculated using the following formula: Moisture content = [(m1-m2) / m1] × 100%.

[0045] Preferably, the processing aids include lubricants and / or β-crystal nucleating agents.

[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 includes phosphoric acid. More preferably, the amount of phosphoric acid is 0.5 to 1.8 parts.

[0049] Adding an appropriate amount of phosphoric acid to a polypropylene composition can significantly improve the flame retardant properties of the resulting pipes, reducing their combustion rate and flame propagation speed. This is particularly important for products used in high-temperature or flammable environments, enhancing their safety and reliability. Furthermore, phosphoric acid, as a processing aid, not only improves the flowability and melt properties of the polypropylene composition but also enhances its processing performance. Adding an appropriate amount of phosphoric acid can lower the melt temperature and viscosity of the polypropylene composition, reducing frictional resistance during extrusion. In the co-extrusion process of polypropylene and nylon, this allows for more thorough contact at the interface, thereby improving the bonding strength between the two. Moreover, phosphoric acid also acts as a reinforcing agent, increasing the strength of the polypropylene composition and improving the overall performance of the resulting fuel filler hose. This results in superior tensile strength and impact resistance, extending the hose's service life and stability.

[0050] The method for preparing the above-mentioned polypropylene composition includes the following steps:

[0051] Polypropylene resin and compatibilizer are mixed evenly to obtain a first premix; bamboo fiber filler, glass fiber filler and processing aids 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 after melt blending, extrusion granulation and drying, the polypropylene composition is obtained.

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

[0053] The application of the above-mentioned polypropylene composition in the preparation of refueling pipes is also within the scope of protection of this invention.

[0054] A tube includes a first layer and a second layer disposed adjacent to each other, the first layer and the second layer being formed by a co-extrusion process, the first layer being nylon and the second layer being the aforementioned 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 beneficial effects of the present invention are:

[0058] The polypropylene composition of this invention comprises polypropylene resin, a compatibilizer, bamboo fiber filler, glass fiber filler, and processing aids. This polypropylene composition is used for co-extrusion with nylon to prepare pipes. Utilizing the characteristic of the hydroxyl groups of the bamboo fiber filler forming hydrogen bonds with nylon, and the synergistic effect of the glass fiber filler, the bonding strength at the interface between the polypropylene composition and nylon is effectively improved, eliminating the need for an intermediate layer material in the co-extrusion process of fuel filler pipes. Furthermore, the full interaction between the bamboo fiber filler and nylon helps reduce the overall water absorption of the material, thereby improving the durability of the fuel filler pipe. Detailed Implementation

[0059] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0060] The reagents used in the various embodiments and comparative examples of this invention are described below:

[0061] 1. Polypropylene resin

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

[0063] Homopolymer polypropylene 2: Model B1101, melt flow rate (230℃ / 2.16kg) is 0.5g / 10min, manufacturer is Formosa Plastics.

[0064] Random copolymer polypropylene: model number SM 198, melt flow rate (230℃ / 2.16kg) is 1.6g / 10min, manufacturer is Lotte Korea.

[0065] 2. Compatibilizer

[0066] Polypropylene grafted with maleic anhydride (PP-g-MAH): Model number CMG9801, manufacturer: Jia Yi Rong, grafting rate 0.5-1.0%.

[0067] Polyethylene grafted with maleic anhydride (PE-g-MAH): Model CMG5804, manufactured by Jia Yirong, grafting rate 0.5-1.0%.

[0068] 3. Bamboo fiber filler

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

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

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

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

[0073] 4. Glass fiber filler

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

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

[0076] 5. Processing aids

[0077] β-crystal nucleating agent: Model NP-328, manufacturer: Jihaichuan.

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

[0079] Phosphoric acid: manufactured by 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: Talc powder, 1250 mesh, Guangxi Longsheng Golden Monkey brand;

[0083] The preparation methods of the polypropylene compositions in the embodiments and comparative examples of the present invention include the following steps:

[0084] By weight, polypropylene resin and compatibilizer are mixed evenly to obtain a first premix; bamboo fiber filler, glass fiber filler and 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 after melt blending, extrusion granulation and drying, a polypropylene composition is obtained; wherein, the extrusion temperature of the extrusion equipment is 200-240℃.

[0085] Examples 1-12

[0086] This embodiment provides a series of polypropylene compositions, the weight parts of each component in the formulation of which are shown in Tables 1 and 2.

[0087] Table 1. Formulations (in portions) for Examples 1-7

[0088] 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 filler 1 6 6 6 / / / 6 Bamboo fiber filler 2 / / / 6 / / / Bamboo fiber filler 3 / / / / 6 / / Bamboo fiber filler 4 / / / / / 6 / Fiberglass filler 1 9 9 9 9 9 9 / Fiberglass filler 2 / / / / / / 9 lubricant 2 2 2 2 2 2 2 β-crystal nucleating agent 2 2 2 2 2 2 2 Phosphoric acid / / / / / / /

[0089] Table 2. Formulations (in portions) for Examples 8-12

[0090]

[0091]

[0092] Comparative Examples 1-8

[0093] This comparative example provides a series of polypropylene compositions, the weight parts of each component in which are shown in Table 3.

[0094] Table 3 shows the formulations (in portions) for Comparative Examples 1–8.

[0095] 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 filler 1 15 1 / 6 6 6 6 / Other plant fibers / / / / / / / 6 Fiberglass filler 1 9 9 9 18 2 / / 9 Other packings / / / / / / 9 / lubricant 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 1-12 and Comparative Examples 1-8 were 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 a polypropylene composition of Examples 1-12 and Comparative Examples 1-8, 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 according to ISO 527-2-2016 standard, with a tensile speed of 50 mm / min;

[0100] (2) Notched impact strength of cantilever beam: tested according to ISO 180-2000 standard;

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

[0102] (4) Bonding force of the inner and outer layers of the refueling pipe: Cut the refueling pipe into two parts, use a tool to pry open the inner and outer layers, use the clamps of a universal tensile testing machine to hold and fix the pried parts, gradually apply tensile force, the tensile speed is 5mm / min, and record the tensile force as the bonding force of the inner and outer layers of the refueling pipe.

[0103] Table 4 Performance test results of each embodiment and comparative example

[0104]

[0105] As can be seen from Table 4, the polypropylene compositions prepared in Examples 1-12 of this invention all have high mechanical properties, and the fuel filler tubes prepared by co-extrusion with nylon all have low water absorption and high bonding strength. In Comparative Example 1, the amount of bamboo fiber filler in the polypropylene composition was too high, resulting in a fuel filler tube with high water absorption and low bonding strength. In Comparative Example 2, the amount of bamboo fiber filler in the polypropylene composition was too low, resulting in a polypropylene composition with lower tensile strength than Example 1, and a fuel filler tube with low bonding strength. In Comparative Example 3, no bamboo fiber filler was added to the polypropylene composition, resulting in a polypropylene composition with lower tensile strength than Example 1, and a fuel filler tube with low bonding strength.

[0106] In Comparative Example 4, the polypropylene composition contained too much glass fiber filler, resulting in high tensile strength, but the resulting fuel filler pipe had high water absorption and low bonding strength. In Comparative Example 5, the polypropylene composition contained too little glass fiber filler, resulting in low tensile strength and low bonding strength in the resulting fuel filler pipe. In Comparative Example 6, no glass fiber filler was added, resulting in low tensile strength and low bonding strength in the resulting fuel filler pipe.

[0107] Comparative Example 7, using other inorganic fillers instead of glass fiber fillers, resulted in a polypropylene composition that produced a fuel filler pipe with higher water absorption and lower bonding strength. Comparative Example 8, using other plant fibers instead of bamboo fiber fillers, also resulted in a polypropylene composition that produced a fuel filler pipe with higher water absorption and lower bonding strength.

[0108] This invention demonstrates that the polypropylene composition of the present invention is used in co-extrusion with nylon to prepare fuel filler pipes. By combining a certain proportion of bamboo fiber filler and glass fiber filler, the bonding force between the polypropylene composition and the nylon interface is effectively improved, eliminating the need for intermediate layer materials in the co-extrusion process of fuel filler pipes. In addition, the full interaction of bamboo fiber filler and nylon helps to reduce 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 implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A pipe, characterized in that, It includes a first layer and a second layer arranged adjacent to each other, the first layer and the second layer being formed by a co-extrusion process, the first layer being nylon and the second layer being a polypropylene composition; The polypropylene composition comprises the following components in parts by weight: 55 parts polypropylene resin, 4.5-6 parts compatibilizer, 5-6 parts bamboo fiber filler, 7-9 parts glass fiber filler, 0.5-1.8 parts phosphoric acid, and 0-5 parts processing aid. The compatibilizer is polypropylene grafted with maleic anhydride; the average cross-sectional diameter of the glass fiber filler is 5-7 μm; the melt flow rate of the polypropylene resin measured at 230℃ and 2.16 kg is 3-5 g / 10 min; the polypropylene resin is homopolymer polypropylene resin. The moisture content of the bamboo fiber filler is ≤5wt%.

2. The pipe according to claim 1, characterized in that, The average diameter of the cross-section of the bamboo fiber filler is 70~150μm.

3. The pipe according to claim 1, characterized in that, The processing aids include lubricants and β-crystal nucleating agents.

4. The pipe according to claim 1, characterized in that, The method for preparing the polypropylene composition includes the following steps: Polypropylene resin and compatibilizer are mixed evenly to obtain a first premix; bamboo fiber filler, glass fiber filler and processing aids 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 after melt blending, extrusion granulation and drying, the polypropylene composition is obtained.

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