MPP pipe with enhanced tensile strength and preparation method thereof

Abstract

The invention relates to the technical field of MPP pipes, in particular to a tensile strength enhanced MPP pipe and a preparation method thereof.The tensile strength enhanced MPP pipe is prepared from, by weight, 80-99 parts of polypropylene, 10-25 parts of composite elastomer, 20-42 parts of polypropylene fiber, 2-5 parts of heat stabilizer, 1-2 parts of antioxidant, 1-4 parts of lubricant and 0.5-1 part of coupling agent. The invention aims to optimize the formula of the MPP pipe and enhance the performance of the MPP pipe by using fibers, so that the MPP pipe has good mechanical properties, especially tensile strength and the like, and thus the MPP pipe has a wider application range.

Description

Technical Field

[0001] The invention relates to the technical field of MPP pipes, and in particular to an MPP pipe with enhanced tensile strength and a preparation method thereof. Background Art

[0002] MPP pipe, or modified polypropylene pipe, is a special pipe material with excellent performance. Its unique properties, such as excellent electrical insulation, high temperature resistance, corrosion resistance, wear resistance and aging resistance, make MPP pipe widely used in many fields, such as power systems, municipal engineering, communications industry, trenchless construction, transportation systems and other industries.

[0003] In some fields such as transportation systems and trenchless construction, when using MPP pipes, it is not only required to have electrical insulation, high temperature resistance, corrosion resistance, and aging resistance, but also good flexibility, pressure resistance, and impact resistance. At present, the MPP pipes on the market are generally above 15MPa. Some standards require that the tensile strength at (23±2)℃ should be greater than 24.0MPa, the tensile strength at 70℃ should also be maintained at around 18.0MPa, and the bending strength at (23±2)℃ should not be less than 37.0MPa. The long-term use temperature range of MPP pipes is generally between -5℃ and 70℃. Although it can be applied to a variety of climatic conditions, in some construction fields such as subways, highways, tunnels, bridges, and trenchless construction, the requirements for the tensile strength, bending strength, and flexibility of MPP pipes are higher. Some MPP pipe manufacturers are actively exploring these aspects, but it is still necessary to explore some to provide more possibilities. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide an MPP pipe with enhanced tensile strength and a preparation method thereof. By optimizing the formula of the MPP pipe and adopting the performance of the fiber-reinforced MPP pipe, the MPP pipe has good mechanical properties, especially tensile strength and other properties, so that the MPP pipe has a wider range of uses.

[0005] The present invention solves the above technical problems by the following technical means: An MPP pipe with enhanced tensile strength comprises the following raw materials in parts by weight: 80-99 parts of polypropylene, 10-25 parts of composite elastomer, 20-42 parts of polypropylene fiber, 2-5 parts of heat stabilizer, 1-2 parts of antioxidant, 1-4 parts of lubricant and 0.5-1 part of coupling agent.

[0006] According to the above technical means, by adding composite elastomers and polypropylene fibers to polypropylene, the mechanical properties of polypropylene, especially tensile strength, bending strength, flexibility and other properties, can be effectively enhanced, and the prepared MPP pipe can be suitable for a variety of environments and have a wide range of applications. By adding additives, the performance of the MPP pipe can be further enhanced.

[0007] Preferably, the polypropylene includes copolymer polypropylene and grafted polypropylene, the melt index of the copolymer polypropylene is 1.5-2.8 g / 10 min; the grafted polypropylene is at least one of ethylene grafted polypropylene, styrene grafted polypropylene and methyl methacrylate grafted polypropylene.

[0008] More preferably, the addition ratio of copolymerized polypropylene and grafted polypropylene is 10:(1-2.5).

[0009] More preferably, the grafted polypropylene is styrene grafted polypropylene, and the grafting rate is 2-3%.

[0010] According to the above technical means, by adopting a mixture of copolymer polypropylene and grafted polypropylene, the tensile strength, impact strength and bonding strength with other materials of the product can be improved, and by controlling the addition ratio and the grafting rate, the tensile strength and impact strength of the product can be further improved, and the processing performance can be effectively improved.

[0011] Preferably, the composite elastomer comprises EPDM rubber, silicone oil, nanofibers and ethylene-vinyl acetate copolymer.

[0012] More preferably, the nanofiber is at least one of carbon nanofiber, polypropylene nanofiber and ceramic nanofiber.

[0013] More preferably, the silicone oil is methyl silicone oil.

[0014] According to the above technical means, a composite elastomer is formed by using EPDM rubber, silicone oil, nanofibers and ethylene-vinyl acetate copolymer. On the one hand, the mechanical properties of EPDM rubber can be enhanced through the mutual coordination of these raw materials. On the other hand, a three-dimensional network structure can be formed in EPDM rubber through the coordination of silicone oil, nanofibers and ethylene-vinyl acetate copolymer. Moreover, through the dispersion and cross-linking effect of methyl silicone oil, when mixed with polypropylene, it can be better compatible and form a cross-linked network, thereby being more evenly distributed to improve the performance of polypropylene.

[0015] Preferably, the preparation of the composite elastomer comprises the following steps: Put EPDM rubber and ethylene-vinyl acetate copolymer in a mixing device, stir for 5-10 minutes at 120-140°C, add silicone oil and nanofiber, continue stirring for 10-30 minutes, transfer to an extruder, extrude and granulate to obtain a composite elastomer.

[0016] According to the above technical means, by first melt-mixing EPDM rubber and ethylene-vinyl acetate copolymer and then adding nanofibers and silicone oil, the nanofibers can be fully dispersed in the molten mixture and cross-linked to a certain extent, and under the action of ethylene-vinyl acetate copolymer, a cross-linked three-dimensional network structure is formed.

[0017] Preferably, the polypropylene fiber includes at least one of polypropylene short fiber, polypropylene long fiber and polypropylene chip fiber.

[0018] More preferably, the polypropylene fibers are polypropylene staple fibers.

[0019] Further preferably, the polypropylene staple fibers are mineral-filled polypropylene staple fibers.

[0020] By using mineral-filled polypropylene short fibers, not only the dimensional stability of the polypropylene fibers can be improved, but also their temperature resistance can be improved, which is beneficial to the preparation of polypropylene short fibers in polypropylene pipes.

[0021] More preferably, the mineral in the mineral-filled polypropylene staple fibers is one or more combinations of talc, calcium carbonate, silicon dioxide, and glass fiber.

[0022] More preferably, the mineral is talc.

[0023] By adding talcum powder filled polypropylene staple fibers, not only the impact resistance and flexibility of the pipe can be enhanced, but also the heat resistance of the pipe can be increased. During the adding process, the polypropylene staple fibers can be well compatible with polypropylene, which can achieve better results while reducing the use of additives, thereby saving costs.

[0024] Preferably, the heat stabilizer is one or more combinations of barium salt heat stabilizers, cadmium salt heat stabilizers, calcium salt heat stabilizers, stearate heat stabilizers, organic tin heat stabilizers and auxiliary heat stabilizers.

[0025] More preferably, the heat stabilizer is a calcium-zinc composite stabilizer.

[0026] Preferably, the antioxidant is at least one of antioxidant 1076, antioxidant 1010, antioxidant 264, antioxidant CA, and antioxidant DNP.

[0027] More preferably, the antioxidant is antioxidant 264.

[0028] Preferably, the lubricant is at least one of oxidized polyethylene wax, fatty acid amide, polyethylene wax, polyurethane lubricant, and oleic acid amide.

[0029] Further preferably, the lubricant is a mixture of oxidized polyethylene wax and oleic acid amide, and the addition ratio of oxidized polyethylene wax to oleic acid amide is 1:1.

[0030] Preferably, the coupling agent is at least one of a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent.

[0031] More preferably, the coupling agent is a silane coupling agent.

[0032] The present application also discloses a method for preparing an MPP pipe with enhanced tensile strength, using the above raw materials, comprising the following steps: S1. Place polypropylene in a mixer, stir for 5-10 minutes at 110-130°C, add a heat stabilizer and an antioxidant, continue stirring for 5-10 minutes, then add a composite elastomer, polypropylene fiber, a lubricant and a coupling agent, raise the temperature to 160-180°C, stir for 3-6 minutes, and obtain a mixture; S2. The mixed material treated in step S1 is transferred to a twin-screw extruder, and after extrusion by the twin-screw extruder, it is shaped by spraying a vacuum shaping box to obtain an MPP tube; S3. Heat-treating the MPP tube in step S2 to obtain an MPP tube with enhanced tensile properties.

[0033] According to the above technical means, the tensile properties of the MPP pipe can be further enhanced by performing a subsequent heat treatment after the pipe is prepared.

[0034] Preferably, in the step S3, during the heat treatment, the MPP tube is placed in a drying tunnel and baked at 35-42° C. During the baking process, the rotation speed of the MPP tube is 10-20 r / min and the residence time is 30-50 s.

[0035] According to the above technical means, by controlling the temperature, rotation speed and baking time of the MPP tube in the drying tunnel, the tensile properties of the MPP tube can be improved without affecting the performance of the MPP tube.

[0036] The present application adopting the above scheme has the following advantages: 1. By adding composite elastomer and polypropylene fiber to polypropylene, the mechanical properties of polypropylene, especially tensile strength, bending strength, flexibility and other properties, can be effectively enhanced, and the prepared MPP pipe can be applied to a variety of environments and has a wide range of applications. Additives can be added to further enhance the performance of the MPP pipe; 2. In the composite elastomer, by using EPDM rubber, silicone oil, nanofibers and ethylene-vinyl acetate copolymer, on the one hand, the mechanical properties of EPDM rubber can be enhanced through the mutual coordination of these raw materials, and on the other hand, a three-dimensional network structure can be formed in EPDM rubber through the coordination of silicone oil, nanofibers and ethylene-vinyl acetate copolymer, so that when mixed with polypropylene, it can be better compatible and form a cross-linked network, so as to be more evenly distributed, so as to improve the performance of polypropylene; 3. In the present application, after the MPP pipe is prepared, the tensile properties of the pipe can be further enhanced through a subsequent heat treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present application may be further illustrated by non-limiting examples given in the accompanying drawings; Figure 1 is a schematic diagram of the structure of the MPP pipe with enhanced tensile strength in an embodiment of the present application; Among them, 1. MPP tube. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention: Example 1, Preparation method of MPP tube with enhanced tensile strength In this embodiment, the raw materials used are as follows: copolymerized polypropylene, with a melt index of 1.5-2.8 g / 10 min; grafted polypropylene, with a grafting rate of 2-3%; the addition ratio of copolymerized polypropylene to grafted polypropylene is 10:1. EPDM rubber, methyl silicone oil, polypropylene nanofiber, ethylene-vinyl acetate copolymer; talc-filled polypropylene short fiber; calcium zinc composite stabilizer; antioxidant 264; oxidized polyethylene wax and oleic acid amide; silane coupling agent.

[0039] Preparation of composite elastomer 100 parts by weight of EPDM rubber and 56 parts by weight of ethylene-vinyl acetate copolymer are placed in a mixing device, stirred at 135°C for 10 minutes, then 5 parts by weight of methyl silicone oil and 34 parts by weight of polypropylene nanofibers are added, and stirring is continued for 20 minutes. The mixture is transferred to an extruder, extruded and granulated at a head temperature of 185-190°C to obtain a composite elastomer.

[0040] Preparation of MPP pipe with enhanced tensile strength S1. 90 parts by weight of copolymerized polypropylene and 9 parts by weight of grafted polypropylene were placed in a mixer, stirred at 120°C for 10 min, 4.5 parts by weight of calcium-zinc composite stabilizer and 2 parts by weight of antioxidant 264 were added, stirring was continued for 8 min, 18 parts by weight of composite elastomer, 20 parts by weight of talc-filled polypropylene staple fibers, 1.2 parts by weight of oxidized polyethylene wax, 1.2 parts by weight of oleic acid amide and 0.8 parts by weight of silane coupling agent were added, the temperature was raised to 175°C, stirred for 5 min, and a mixture was obtained; S2. The mixed material treated in step S1 is transferred to a twin-screw extruder. After extrusion by the twin-screw extruder, the process parameters of the twin-screw extruder are: zone 1 is 200-220°C, zone 2 is 190-200°C, zone 3 is 180-195°C, zone 4 is 170-185°C, zone 5 is 165-175°C, the head temperature is 180°C-190°C, and the mixed material is shaped by spraying a vacuum shaping box, the water cooling temperature of the spraying vacuum shaping box is 17±1°C, and the pulling speed is 2.5m / min to obtain an MPP tube; S3. The MPP tube in step S2 is heat treated. During the heat treatment, the MPP tube is placed in a drying oven and baked at 42° C. During the baking process, the rotation speed of the MPP tube is 20 r / min and the residence time is 40 s, thereby obtaining an MPP tube 1 with enhanced tensile properties.

[0041] Example 2, Preparation method 2 of MPP tube with enhanced tensile strength In the examples of the present application, the raw materials used are the same as those in Example 1, except that the addition ratio of copolymerized polypropylene and grafted polypropylene is 10:2.

[0042] Preparation of composite elastomer 100 parts by weight of EPDM rubber and 56 parts by weight of ethylene-vinyl acetate copolymer are placed in a mixing device, stirred at 135°C for 10 minutes, then 5 parts by weight of methyl silicone oil and 34 parts by weight of polypropylene nanofibers are added, and stirring is continued for 20 minutes. The mixture is transferred to an extruder, extruded and granulated at a head temperature of 185-190°C to obtain a composite elastomer.

[0043] Preparation of MPP pipe with enhanced tensile strength S1. 77.5 parts by weight of copolymerized polypropylene and 15.5 parts by weight of grafted polypropylene were placed in a mixer, stirred at 120°C for 10 min, 3.6 parts by weight of calcium-zinc composite stabilizer and 1.2 parts by weight of antioxidant 264 were added, stirring was continued for 8 min, 22 parts by weight of composite elastomer, 26 parts by weight of talc-filled polypropylene staple fibers, 1.6 parts by weight of oxidized polyethylene wax, 1.6 parts by weight of oleic acid amide and 1 part by weight of silane coupling agent were added, the temperature was raised to 175°C, stirred for 5 min, and a mixture was obtained; S2. The mixed material treated in step S1 is transferred to a twin-screw extruder. After extrusion by the twin-screw extruder, the process parameters of the twin-screw extruder are: zone 1 is 200-220°C, zone 2 is 190-200°C, zone 3 is 180-195°C, zone 4 is 170-185°C, zone 5 is 165-175°C, the head temperature is 180°C-190°C, and the mixed material is shaped by spraying a vacuum shaping box, the water cooling temperature of the spraying vacuum shaping box is 17±1°C, and the pulling speed is 2.5m / min to obtain an MPP tube; S3. The MPP tube in step S2 is heat treated. During the heat treatment, the MPP tube is placed in a drying oven and baked at 42° C. During the baking process, the rotation speed of the MPP tube is 20 r / min and the residence time is 40 s, thereby obtaining an MPP tube 1 with enhanced tensile properties.

[0044] Example 3, Preparation method of MPP tube with enhanced tensile strength In this embodiment, the raw materials used are the same as those in Embodiment 1, except that the addition ratio of copolymerized polypropylene and grafted polypropylene is 10:2.5.

[0045] Preparation of composite elastomer 100 parts by weight of EPDM rubber and 56 parts by weight of ethylene-vinyl acetate copolymer are placed in a mixing device, stirred at 135°C for 10 minutes, then 5 parts by weight of methyl silicone oil and 34 parts by weight of polypropylene nanofibers are added, and stirring is continued for 20 minutes. The mixture is transferred to an extruder, extruded and granulated at a head temperature of 185-190°C to obtain a composite elastomer.

[0046] Preparation of MPP pipe with enhanced tensile strength S1. 64 parts by weight of copolymerized polypropylene and 16 parts by weight of grafted polypropylene were placed in a mixer, stirred at 120°C for 10 min, 2 parts by weight of calcium-zinc composite stabilizer and 1 part by weight of antioxidant 264 were added, stirring was continued for 6 min, 25 parts by weight of composite elastomer, 42 parts by weight of talc-filled polypropylene staple fibers, 1.8 parts by weight of oxidized polyethylene wax, 1.8 parts by weight of oleic acid amide and 1 part by weight of silane coupling agent were added, the temperature was raised to 175°C, stirred for 6 min, and a mixture was obtained; S2. The mixed material treated in step S1 is transferred to a twin-screw extruder. After extrusion by the twin-screw extruder, the process parameters of the twin-screw extruder are: zone 1 is 200-220°C, zone 2 is 190-200°C, zone 3 is 180-195°C, zone 4 is 170-185°C, zone 5 is 165-175°C, the head temperature is 180°C-190°C, and the mixed material is shaped by spraying a vacuum shaping box, the water cooling temperature of the spraying vacuum shaping box is 17±1°C, and the pulling speed is 2.5m / min to obtain an MPP tube; S3. The MPP tube in step S2 is heat treated. During the heat treatment, the MPP tube is placed in a drying oven and baked at 42° C. During the baking process, the rotation speed of the MPP tube is 20 r / min and the residence time is 40 s, thereby obtaining an MPP tube 1 with enhanced tensile properties.

[0047] Example 4, MPP tube preparation method 4 In this embodiment, the raw materials used are the same as those in Example 2, except that the raw materials of the composite elastomer are directly added without being prepared in advance, as follows: S1. 77.5 parts by weight of copolymerized polypropylene and 15.5 parts by weight of grafted polypropylene are placed in a mixer, stirred at 120°C for 10 min, 3.6 parts by weight of calcium-zinc composite stabilizer and 1.2 parts by weight of antioxidant 264 are added, stirring is continued for 8 min, 11 parts by weight of ethylene propylene rubber, 1 part by weight of methyl silicone oil, 5 parts by weight of polypropylene nanofibers, 5 parts by weight of ethylene-vinyl acetate copolymer, 26 parts by weight of talc-filled polypropylene staple fibers, 1.6 parts by weight of oxidized polyethylene wax, 1.6 parts by weight of oleic acid amide and 1 part by weight of silane coupling agent are added, the temperature is raised to 175°C, stirred for 5 min, and a mixture is obtained; S2. The mixed material treated in step S1 is transferred to a twin-screw extruder. After extrusion by the twin-screw extruder, the process parameters of the twin-screw extruder are: zone 1 is 200-220°C, zone 2 is 190-200°C, zone 3 is 180-195°C, zone 4 is 170-185°C, zone 5 is 165-175°C, the head temperature is 180°C-190°C, and the mixed material is shaped by spraying a vacuum shaping box, the water cooling temperature of the spraying vacuum shaping box is 17±1°C, and the pulling speed is 2.5m / min to obtain an MPP tube; S3. The MPP tube in step S2 is heat treated. During the heat treatment, the MPP tube is placed in a drying oven and baked at 42° C. During the baking process, the rotation speed of the MPP tube is 20 r / min and the residence time is 40 s, thereby obtaining an MPP tube 1 with enhanced tensile properties.

[0048] Example 5, MPP tube preparation method 5 In this embodiment, the raw materials used are the same as those in Example 2, except that no composite elastomer is added, as follows: S1. 77.5 parts by weight of copolymerized polypropylene and 15.5 parts by weight of grafted polypropylene were placed in a mixer, stirred at 120°C for 10 min, 3.6 parts by weight of calcium-zinc composite stabilizer and 1.2 parts by weight of antioxidant 264 were added, stirring was continued for 8 min, 26 parts by weight of talc-filled polypropylene staple fibers, 1.6 parts by weight of oxidized polyethylene wax, 1.6 parts by weight of oleic acid amide and 1 part by weight of silane coupling agent were added, the temperature was raised to 175°C, stirred for 5 min, and a mixture was obtained; S2. The mixed material treated in step S1 is transferred to a twin-screw extruder. After extrusion by the twin-screw extruder, the process parameters of the twin-screw extruder are: zone 1 is 200-220°C, zone 2 is 190-200°C, zone 3 is 180-195°C, zone 4 is 170-185°C, zone 5 is 165-175°C, the head temperature is 180°C-190°C, and the mixed material is shaped by spraying a vacuum shaping box, the water cooling temperature of the spraying vacuum shaping box is 17±1°C, and the pulling speed is 2.5m / min to obtain an MPP tube; S3. The MPP tube in step S2 is heat treated. During the heat treatment, the MPP tube is placed in a drying oven and baked at 42° C. During the baking process, the rotation speed of the MPP tube is 20 r / min and the residence time is 40 s, thereby obtaining an MPP tube 1 with enhanced tensile properties.

[0049] Example 6, MPP tube preparation method 6 In this embodiment, the raw materials used are the same as those in Example 2, except that EPDM rubber is added instead of the composite elastomer, as follows: S1. 77.5 parts by weight of copolymerized polypropylene and 15.5 parts by weight of grafted polypropylene were placed in a mixer, stirred at 120°C for 10 min, 3.6 parts by weight of calcium-zinc composite stabilizer and 1.2 parts by weight of antioxidant 264 were added, stirring was continued for 8 min, 22 parts by weight of ethylene propylene rubber, 26 parts by weight of talc-filled polypropylene staple fibers, 1.6 parts by weight of oxidized polyethylene wax, 1.6 parts by weight of oleic acid amide and 1 part by weight of silane coupling agent were added, the temperature was raised to 175°C, stirred for 5 min, and a mixture was obtained; S2. The mixed material treated in step S1 is transferred to a twin-screw extruder. After extrusion by the twin-screw extruder, the process parameters of the twin-screw extruder are: zone 1 is 200-220°C, zone 2 is 190-200°C, zone 3 is 180-195°C, zone 4 is 170-185°C, zone 5 is 165-175°C, the head temperature is 180°C-190°C, and the mixed material is shaped by spraying a vacuum shaping box, the water cooling temperature of the spraying vacuum shaping box is 17±1°C, and the pulling speed is 2.5m / min to obtain an MPP tube; S3. The MPP tube in step S2 is heat treated. During the heat treatment, the MPP tube is placed in a drying oven and baked at 42° C. During the baking process, the rotation speed of the MPP tube is 20 r / min and the residence time is 40 s, thereby obtaining an MPP tube 1 with enhanced tensile properties.

[0050] Example 7, MPP tube preparation method 7 In this embodiment, the raw materials used are the same as those in Example 2, except that, instead of adding a composite elastomer, polypropylene nanofibers are added, and the amount of polypropylene nanofibers used is 22 parts by weight. The remaining steps are the same as those in Example 6.

[0051] Example 8, MPP tube preparation method eight In this embodiment, the raw materials used are the same as those in Example 2, except that, instead of adding a composite elastomer, ethylene-vinyl acetate copolymer is added, and the amount of ethylene-vinyl acetate copolymer used is 22 parts by weight. The remaining steps are the same as those in Example 6.

[0052] Example 9, Preparation Method of MPP Tube In this embodiment, the raw materials used are the same as those in Example 2, except that, instead of adding a composite elastomer, EPDM rubber and polypropylene nanofibers are added, and the added amounts of EPDM rubber and polypropylene nanofibers are both 11 parts by weight. The remaining steps are the same as those in Example 6.

[0053] Example 10, MPP tube preparation method 10 In this embodiment, the raw materials used are the same as those in Example 2, except that, instead of adding a composite elastomer, EPDM rubber and ethylene-vinyl acetate copolymer are added, and the added amounts of EPDM rubber and ethylene-vinyl acetate copolymer are both 11 parts by weight. The remaining steps are the same as those in Example 6.

[0054] Example 11, MPP tube preparation method 11 In this embodiment, the raw materials used are the same as those in Example 2, except that, instead of adding a composite elastomer, polypropylene nanofibers and ethylene-vinyl acetate copolymer are added, and the added amounts of the polypropylene nanofibers and ethylene-vinyl acetate copolymer are both 11 parts by weight. The remaining steps are the same as those in Example 6.

[0055] Example 12, MPP tube preparation method 12 In this embodiment, the raw materials used are the same as those in Example 2, except that the composite elastomer and talcum powder are not added to fill the polypropylene short fibers, specifically as follows: S1. 77.5 parts by weight of copolymerized polypropylene and 15.5 parts by weight of grafted polypropylene were placed in a mixer, stirred at 120°C for 10 min, 3.6 parts by weight of calcium zinc composite stabilizer and 1.2 parts by weight of antioxidant 264 were added, stirring was continued for 8 min, 1.6 parts by weight of oxidized polyethylene wax, 1.6 parts by weight of oleic acid amide and 1 part by weight of silane coupling agent were added, the temperature was raised to 175°C, stirred for 5 min, and a mixture was obtained; S2. The mixed material treated in step S1 is transferred to a twin-screw extruder. After extrusion by the twin-screw extruder, the process parameters of the twin-screw extruder are: zone 1 is 200-220°C, zone 2 is 190-200°C, zone 3 is 180-195°C, zone 4 is 170-185°C, zone 5 is 165-175°C, the head temperature is 180°C-190°C, and the mixed material is shaped by spraying a vacuum shaping box, the water cooling temperature of the spraying vacuum shaping box is 17±1°C, and the pulling speed is 2.5m / min to obtain an MPP tube; S3. The MPP tube in step S2 is heat treated. During the heat treatment, the MPP tube is placed in a drying oven and baked at 42° C. During the baking process, the rotation speed of the MPP tube is 20 r / min and the residence time is 40 s, thereby obtaining an MPP tube 1 with enhanced tensile properties.

[0056] Example 13, MPP tube preparation method 13 In this embodiment, the raw materials used are the same as those in Example 2, except that the MPP tube is not subjected to heat treatment, as follows: S1. 77.5 parts by weight of copolymerized polypropylene and 15.5 parts by weight of grafted polypropylene were placed in a mixer, stirred at 120°C for 10 min, 3.6 parts by weight of calcium-zinc composite stabilizer and 1.2 parts by weight of antioxidant 264 were added, stirring was continued for 8 min, 22 parts by weight of composite elastomer, 26 parts by weight of talc-filled polypropylene staple fibers, 1.6 parts by weight of oxidized polyethylene wax, 1.6 parts by weight of oleic acid amide and 1 part by weight of silane coupling agent were added, the temperature was raised to 175°C, stirred for 5 min, and a mixture was obtained; S2. The mixed material treated in step S1 is transferred into a twin-screw extruder. After extrusion by the twin-screw extruder, the process parameters of the twin-screw extruder are: zone 1 is 200-220°C, zone 2 is 190-200°C, zone 3 is 180-195°C, zone 4 is 170-185°C, zone 5 is 165-175°C, the head temperature is 180°C-190°C, and the mixed material is shaped by spraying a vacuum shaping box. The water cooling temperature of the spraying vacuum shaping box is 17±1°C, and the pulling speed is 2.5m / min to obtain an MPP tube.

[0057] The MPP prepared in Examples 1-3 was subjected to performance tests, and the tensile strength, bending strength, notched impact strength, and ring stiffness of the MPP pipe were tested, wherein the tensile strength was tested in accordance with the national standard GB / T 1040-92; the notched impact strength was tested by simply supported beam impact strength, and the ring stiffness was tested in accordance with the national standard DL / T 802.1; the test results are shown in Table 1:

[0058] According to the data in Table 1, in this application, the MPP pipes prepared in Examples 1-3 have good tensile strength, bending strength, notched impact strength and ring stiffness. Among them, the tensile strength at 23°C is about 2 times higher than the 20MPa of the conventional MPP pipe, and relative to the standard, it is increased by about 33.8%, especially Example 2, which is increased by 35%; there is a significant improvement; and at 70°C, relative to the standard, it is increased by about 34.8%, especially Example 2, which is increased by 35.5%, which is a significant improvement. Therefore, the raw materials and preparation methods used in this application can significantly improve the tensile strength of the MPP pipe.

[0059] The bending strength is increased by about 17.8% relative to the standard, and the bending strength of Example 2 is increased by 18.3%. Therefore, the bending strength is also significantly improved. The simply supported beam impact strength is increased by 29.3% relative to the standard; and the ring stiffness SN40 is increased by 16.7% relative to the standard, indicating that the raw materials and preparation methods used in this application can not only improve the ring stiffness of the MPP pipe, but also improve the tensile strength.

[0060] The MPP pipes prepared in Examples 4-13 were subjected to the same performance tests as above, using the same test methods, and the test results are shown in Table 2:

[0061] According to the data in Table 2, when the raw materials of the composite elastomer are directly added to the MPP pipe, the tensile strength, bending strength, and notched impact strength of the MPP pipe are significantly reduced, but the ring stiffness is not significantly reduced, indicating that the pre-preparation of the composite elastomer can improve the tensile strength, bending strength, and notched impact strength of the MPP pipe to a certain extent. When the composite elastomer is not added to the MPP pipe, the tensile strength, bending strength, notched impact strength, and ring stiffness of the MPP pipe are significantly reduced, indicating that the addition of the composite elastomer can improve the tensile strength, bending strength, notched impact strength, and ring stiffness of the MPP pipe.

[0062] According to the data in Table 2, when only one or two raw materials of the composite elastomer are added to the MPP pipe, the tensile strength, bending strength, notched impact strength and ring stiffness of the MPP pipe are greatly reduced. When EPDM rubber, polypropylene nanofiber and ethylene-vinyl acetate copolymer are added separately, ethylene-vinyl acetate copolymer has a greater improvement on the tensile and bending properties of the MPP pipe; and in terms of simply supported beam impact strength, polypropylene nanofiber has a more obvious improvement on the performance of the MPP pipe, but in terms of ring stiffness, the three perform similarly.

[0063] Compared with adding any two of the three alone, the tensile strength, flexural strength, notched impact strength and ring stiffness are improved by adding any two of EPDM rubber, polypropylene nanofiber, and ethylene-vinyl acetate copolymer. However, at 70°C, the improvement in tensile performance is not very obvious, indicating that the synergistic performance of any two materials, although improved compared to a single one, is not as obvious as when the three materials are pre-prepared.

[0064] According to the data in Table 2, when the composite elastomer and talcum powder are not added to fill the polypropylene short fibers, the tensile strength, bending strength, notched impact strength and ring stiffness of the MPP pipe are significantly lower than those of the conventional MPP pipe. This is because no filler is added to the MPP pipe at this time. This shows that the addition of composite elastomer and talcum powder to fill the polypropylene short fibers can not only play the role of fillers, but also synergistically improve the tensile strength, bending strength, notched impact strength and ring stiffness of the MPP pipe.

[0065] According to the data in Table 2, when the MPP pipe is not heat treated, the tensile strength is reduced compared with the heat treated MPP pipe, especially at 23°C, the tensile strength is reduced by about 6%, and the tensile strength at 70°C is reduced, but it is about 4.3%, indicating that heat treatment can effectively improve the tensile properties of MPP pipes at room temperature. However, the influence on bending strength, simply supported beam impact strength and ring stiffness is not very obvious.

[0066] The above is a detailed introduction to an MPP tube with enhanced tensile strength and a preparation method thereof provided by the present invention. The description of the specific embodiment is only used to help understand the method and its core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0067] It should be noted that if no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be purchased commercially.

[0068] The above examples are intended to provide a better understanding of the present invention, and are not intended to be limiting of the best implementation mode described herein, nor are they intended to limit the content and protection scope of the present invention. Any product identical or similar to the present invention that is derived by anyone under the inspiration of the present invention or by combining the present invention with features of other prior arts shall fall within the protection scope of the present invention.

Claims

1. An MPP pipe with enhanced tensile strength, characterized in that: The invention comprises the following raw materials in parts by weight: 80-99 parts of polypropylene, 10-25 parts of composite elastomer, 20-42 parts of polypropylene fiber, 2-5 parts of heat stabilizer, 1-2 parts of antioxidant, 1-4 parts of lubricant and 0.5-1 parts of coupling agent.

2. The MPP pipe with enhanced tensile strength according to claim 1, characterized in that: The polypropylene includes copolymerized polypropylene and grafted polypropylene. The melt index of the copolymerized polypropylene is 1.5-2.8 g / 10 min. The grafted polypropylene is at least one of ethylene grafted polypropylene, styrene grafted polypropylene and methyl methacrylate grafted polypropylene.

3. The MPP pipe with enhanced tensile strength according to claim 1, characterized in that: The composite elastomer comprises EPDM rubber, silicone oil, nanofiber and ethylene-vinyl acetate copolymer.

4. The MPP pipe with enhanced tensile strength according to claim 3, characterized in that: The preparation of the composite elastomer comprises the following steps: Put EPDM rubber and ethylene-vinyl acetate copolymer in a mixing device, stir for 5-10 minutes at 120-140°C, add silicone oil and nanofiber, continue stirring for 10-30 minutes, transfer to an extruder, extrude and granulate to obtain a composite elastomer.

5. The MPP pipe with enhanced tensile strength according to claim 1, characterized in that: The polypropylene fiber includes at least one of polypropylene short fiber, polypropylene long fiber and polypropylene chip fiber.

6. The MPP pipe with enhanced tensile strength according to claim 1, characterized in that: The heat stabilizer is one or more combinations of a barium salt heat stabilizer, a cadmium salt heat stabilizer, a calcium salt heat stabilizer, a stearate heat stabilizer, an organic tin heat stabilizer and an auxiliary heat stabilizer.

7. The MPP pipe with enhanced tensile strength according to claim 1, characterized in that: The antioxidant is at least one of antioxidant 1076, antioxidant 1010, antioxidant 264, antioxidant CA, and antioxidant DNP.

8. The MPP pipe with enhanced tensile strength according to claim 1, characterized in that: The lubricant is at least one of oxidized polyethylene wax, fatty acid amide, polyethylene wax, polyurethane lubricant, and oleic acid amide; The coupling agent is at least one of a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent.

9. A method for preparing an MPP pipe with enhanced tensile strength according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Place polypropylene in a mixer, stir for 5-10 minutes at 110-130°C, add a heat stabilizer and an antioxidant, continue stirring for 5-10 minutes, then add a composite elastomer, polypropylene fiber, a lubricant and a coupling agent, raise the temperature to 160-180°C, stir for 3-6 minutes, and obtain a mixture; S2. The mixed material treated in step S1 is transferred to a twin-screw extruder, and after extrusion by the twin-screw extruder, it is shaped by spraying a vacuum shaping box to obtain an MPP tube; S3. Heat-treating the MPP tube in step S2 to obtain an MPP tube with enhanced tensile properties.

10. The preparation method according to claim 9, characterized in that: In the step S3, during the heat treatment, the MPP tube is placed in a drying tunnel and baked at 35-42° C. During the baking process, the rotation speed of the MPP tube is 10-20 r / min and the residence time is 30-50 s.

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