Low-temperature-cracking-resistant composite PPR pipe and preparation method thereof

Abstract

The invention discloses a low-temperature-cracking-resistant composite PPR pipe and a preparation method thereof. The nucleating agent composite master batch comprises the following components in parts by mass: basic master batch and magnetic master batch, the basic master batch comprises homo-polypropylene resin and a modified nucleating agent, and the content of the modified nucleating agent is 3-6 wt.%; the magnetic master batch comprises polypropylene random copolymer resin, magnetic fibers and a modified nucleating agent, the content of the modified nucleating agent is 3-6 wt.%, and the content of the magnetic fibers is 3-5 wt.%. According to the composite PPR pipe, the polypropylene random copolymer resin serves as a matrix, the nucleating agent composite master batch is added, the nucleating agent composite master batch can be enriched on the surface of the PPR pipe under the action of an external magnetic field in the machining process, the surface toughness of the PPR pipe is improved, meanwhile, a protective layer is formed, and therefore the low-temperature brittleness of the PPR pipe is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of PPR pipe processing, and more specifically, to a composite PPR pipe material resistant to low-temperature cracking and a preparation method thereof. Background Art

[0002] Random copolymer polypropylene (PPR) resin is one of the most commonly used raw materials in the production of plastic pipe materials. Due to the random distribution of the comonomer on the main chain of polypropylene, its molecular structure and crystallization characteristics are changed, so that the material has excellent physical and mechanical properties, molding and processing properties and good chemical stability; PPR pipes are widely used in the preparation of water supply pipes, fresh water transportation pipes, building heating pipes, chemical material transportation pipes, agricultural and forestry irrigation pipes and other fields.

[0003] However, PPR pipes generally have the disadvantage of low-temperature brittleness. They will show greater brittleness in environments with temperatures below zero, causing PPR pipes to easily break under external forces during use or installation. At present, most PPR pipes use the method of adding β-nucleating agents to improve their low-temperature brittleness. However, in actual applications, it is found that some PPR pipes that break in low-temperature environments are easily impacted by external forces to form gaps because the outer surface is not properly protected. The gap will become a stress concentration point. When the PPR pipe shows greater brittleness, cracks will spread from the gap, causing the PPR pipe to break; even if the gap is formed under higher ambient temperatures, the PPR pipe will also show greater brittleness when the ambient temperature is lower, and the PPR pipe may still break due to the gap.

[0004] Patent CN110343337A provides a low-temperature toughened PP-R pipe, which introduces a toughening agent into a random copolymer polypropylene (PP-R) resin, and the toughening agent also contains a layered double metal hydroxide loaded with a β nucleating agent. At the same time, the online nucleation and offline grain growth processes of the pipe are added, and the number and content of β crystals are increased to improve the low-temperature toughness of the pipe. At the same time, the temperature is lowered by a program, first slowly and then quickly, so that the pipe is cooled quickly while forming as many grains as possible, forming small and uniform grains, thereby reducing the stress formation of the pipe and controlling the grain size. However, in the above-mentioned PP-R pipe manufacturing process, although the pipe is subjected to online nucleation and offline grain growth treatment, so that the inside of the pipe is fully and massively nucleated, the density of the β crystal on the outer surface of the pipe is low, resulting in the outer surface being easily notched under the action of external force. When the ambient temperature is low, the notch will become a stress concentration point and form several cracks and spread, thereby causing the pipe to rupture. Therefore, it is necessary to protect the outer surface of the PPR pipe or improve the strength and toughness of its outer surface to avoid the rupture of the PPR pipe in a low temperature environment. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects and shortcomings of existing PPR pipes and provide a nucleating agent composite masterbatch, which can be enriched on the surface of the PPR pipe under the action of an external magnetic field during the processing process, improve the surface toughness of the PPR pipe, and form a protective layer at the same time, thereby improving the low-temperature brittleness of the PPR pipe.

[0006] Another object of the present invention is to provide a composite PPR pipe having good resistance to low temperature cracking.

[0007] Another object of the present invention is to provide a method for preparing a composite PPR pipe.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] The present invention protects a nucleating agent composite masterbatch, comprising the following components in parts by weight: 40-80 parts of a basic masterbatch, 20-60 parts of a magnetic masterbatch;

[0010] The base masterbatch comprises homopolymer polypropylene resin and modified nucleating agent, wherein the content of the modified nucleating agent is 3-6wt.%;

[0011] The magnetic masterbatch comprises random copolymerized polypropylene resin, magnetic fiber and modified nucleating agent, wherein the content of the modified nucleating agent is 3-6wt.%, and the content of the magnetic fiber is 3-5wt.%.

[0012] In the nucleating agent composite masterbatch of the present invention, the content of the modified nucleating agent in the masterbatch is controlled, which is conducive to improving the uniformity of the dispersion of the modified nucleating agent. At the same time, a specific amount of magnetic fiber is introduced, which can drive the modified nucleating agent to migrate and enrich toward the surface of the material under the action of an external magnetic field during melt blending, thereby increasing the density of the modified nucleating agent on the side close to the outer surface of the PPR pipe. As the modified nucleating agent induces the random copolymer polypropylene resin to nucleate in the β-crystal form, the density of the β-crystal form on the outer surface of the PPR pipe is increased, so that the outer surface of the PPR pipe has higher toughness. At the same time, the magnetic fibers are concentrated on the outer surface of the PPR pipe before shaping. After the PPR pipe is shaped, the magnetic fibers can form a fiber layer on the outer surface of the PPR pipe, thereby further improving the toughness of the outer surface of the PPR pipe and improving the low-temperature brittleness of the PPR pipe. In addition, the homopolymerized polypropylene resin is used as the matrix in the basic masterbatch, and the application in the PPR pipe can improve the high temperature resistance of the PPR.

[0013] In some embodiments, the modified nucleating agent is a β-nucleating agent modified by a silane coupling agent.

[0014] Specifically, the following preparation method is adopted: the β nucleating agent and acetone are stirred evenly to form a suspension, a silane coupling agent is added while the suspension is stirred, and the stirring is continued until the reaction is complete, and then the product is filtered, washed, and dried to obtain a modified nucleating agent.

[0015] Preferably, the mass ratio of the β-nucleating agent to the silane coupling agent is 100:(0.5-2).

[0016] After silane coupling modification, the β-nucleating agent can improve its compatibility and interfacial properties with random copolymer polypropylene resin, thereby improving the dispersion performance and stability of the β-nucleating agent; in addition, the silane coupling agent can make the bonding interface between the polymer and the nanofiber become a chemical bond, which significantly improves the reinforcement performance of the β-nucleating agent.

[0017] In some embodiments, the beta nucleating agent is selected from TMB-5 and / or NAB-83C.

[0018] The principle of β-nucleating agent to reduce the low-temperature brittleness of PPR material is to change the crystallization mode of the pipe by changing the cooling temperature of the pipe during the production process; when the above-mentioned preferred β-nucleating agent is added to the PPR material, the β-nucleating agent will interact with the PPR molecular chain, promote the orderly arrangement of the molecular chain, and make the molecular chain more evenly distributed during the cooling process. This will change the crystallization mode of the PPR pipe, making its crystal structure more fine and uniform, thereby improving the toughness, heat deformation temperature and other properties of the material, thereby reducing the low-temperature brittleness of the material.

[0019] In some embodiments, the magnetic fibers are composites of magnetic particles and nanofibers.

[0020] In some embodiments, the mass ratio of the magnetic particles to the nanofibers is 1:(1-3).

[0021] In some embodiments, the single fiber diameter of the magnetic fiber is 1-20 nm, preferably 3-12 nm.

[0022] In some embodiments, the nanofiber is selected from one or more of nano-polyamide fiber, nano-polyphenylene sulfide fiber, nano-polyimide fiber or nano-polyetheretherketone fiber.

[0023] Preferably, the magnetic particles are selected from at least one of nano iron oxide magnetic powder, nano chromium dioxide magnetic powder and nano cobalt-iron oxide magnetic powder.

[0024] Preferably, the average particle size of the magnetic particles is 10-40 nm.

[0025] The method for preparing the magnetic fiber of the present invention comprises the following steps:

[0026] 1) adding nanofibers into an organic solvent and stirring to form a uniform nanofiber dispersion;

[0027] 2) dispersing magnetic particles in the nanofiber dispersion to form a composite solution;

[0028] 3) Add methyl methacrylate to the composite solution, heat and stir, and after the reaction in the composite solution is complete, filter and separate to obtain magnetic fibers.

[0029] Optionally, the organic solvent is dimethyl sulfoxide.

[0030] Optionally, the mass ratio of the magnetic particles to the nanofibers is 1:(1-3).

[0031] Optionally, the methyl methacrylate is 10-100wt% of the nanofiber content, preferably 30-60wt%.

[0032] Optionally, the heating temperature is 50-100°C, preferably 60-85°C.

[0033] The preparation method of the magnetic fiber can combine the magnetic particles with the nanofibers, so that the magnetic particles are attached to the surface of the nanofibers to form magnetic fibers with magnetism.

[0034] Among them, methyl methacrylate can be chemically grafted to the fiber surface, allowing the magnetic particles to better adhere to the fiber surface.

[0035] The invention protects a composite PPR pipe, comprising the composite masterbatch of the nucleating agent.

[0036] In some embodiments, the following components are included in parts by weight: 92-97 parts of random copolymer polypropylene resin and 3-8 parts of nucleating agent composite masterbatch.

[0037] There is no particular limitation on the random copolymer polypropylene resin (PP-R) and homopolymer polypropylene resin (PP-H) of the present invention, and common materials in the art may be used.

[0038] Optionally, the PP-R has a melt flow rate of 0.1-10 g / 10 min at 230° C. and 2.16 kg.

[0039] Optionally, the PP-H has a melt flow rate of 1-20 g / 10 min at 230° C. and 2.16 kg.

[0040] The present invention provides a method for preparing a composite PPR pipe, comprising the following steps:

[0041] S1, uniformly mixing the modified nucleating agent and the homopolymerized polypropylene resin, and melt-extruding and granulating to obtain a basic masterbatch;

[0042] S2, uniformly mixing the modified nucleating agent, random copolymerized polypropylene resin and magnetic fiber, and melt-extruding and granulating to obtain a magnetic masterbatch;

[0043] S3, uniformly mixing the basic masterbatch in step S1 and the magnetic masterbatch in step S2 to obtain a nucleating agent composite masterbatch;

[0044] S4, uniformly mixing the nucleating agent composite masterbatch and the random copolymer polypropylene resin, melt-extruded under an external magnetic field, molded, and heat-treated to obtain the composite PPR pipe.

[0045] The preparation method of the composite PPR pipe of the present invention applies an external magnetic field during the melt blending process. On the one hand, the density of the modified nucleating agent on the side close to the outer surface of the PPR pipe can be increased. As the nucleating agent induces the random copolymerized polypropylene resin to nucleate in the β-crystal form, the density of the β-crystal form on the outer surface of the PPR pipe is increased, so that the outer surface of the PPR pipe has higher toughness. On the other hand, the magnetic fibers are concentrated and dispersed on the outer surface of the PPR pipe before shaping. After the PPR pipe is shaped, the magnetic fibers can form a fiber layer on the outer surface of the PPR pipe for protection, thereby further improving the toughness of the outer surface of the PPR pipe and improving the low-temperature brittleness of the PPR pipe.

[0046] In some embodiments, in step S1 and step S2, the extrusion temperature is 170-190° C. respectively.

[0047] In some embodiments, in step S4, the extrusion temperature is 190-220°C, and the temperature of the mold is 210-230°C.

[0048] In some of the embodiments, in step S4, the formed pipe is cooled and shaped by passing through water at a temperature of 15-30° C., and the vacuum degree during the cooling and shaping process is -0.03 MPa to -0.01 MPa.

[0049] In some embodiments, the heat treatment temperature is 80-120°C and the heat treatment time is 3-5 hours. Heat treatment can effectively reduce the intermolecular tension of each component in the PPR pipe, enhance the stability of the crystal structure, improve the dimensional stability, and make the crystal more perfect, the grains finer, and the impact resistance improved.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The present invention provides a nucleating agent composite masterbatch, which introduces a specific amount of magnetic fibers, and can drive the modified nucleating agent to migrate and enrich toward the material surface under the action of an external magnetic field during melt blending, thereby increasing the density of the modified nucleating agent on the side close to the outer surface of the PPR pipe, and as the modified nucleating agent induces the random copolymerized polypropylene resin to nucleate in the β crystal form, the density of the β crystal form on the outer surface of the PPR pipe is increased, so that the outer surface of the PPR pipe has higher toughness. At the same time, the magnetic fibers are concentrated on the outer surface of the PPR pipe before shaping. When the PPR pipe is shaped, the magnetic fibers can form a fiber layer on the outer surface of the PPR pipe, thereby further improving the toughness of the outer surface of the PPR pipe and improving the low-temperature brittleness of the PPR pipe.

[0052] The present invention provides a composite PPR pipe material, which takes random copolymer polypropylene resin as a matrix and is added with a nucleating agent composite masterbatch. The nucleating agent in the masterbatch can be enriched on the surface of the PPR pipe under the action of an external magnetic field during a processing process, so that the outer surface of the PPR pipe has higher toughness; at the same time, magnetic fibers are introduced to form a fiber layer on the outer surface of the PPR pipe, thereby improving the surface toughness of the PPR pipe and improving the low-temperature brittleness of the PPR pipe. DETAILED DESCRIPTION

[0053] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0054] The raw materials used in the following examples and comparative examples are as follows:

[0055] Random copolymer polypropylene resin (PP-R):

[0056] PP-R 1#: 230℃, melt flow rate is 0.23g / 10min under 2.16kg conditions; PA14D, Xuzhou Haitian Petrochemical Company.

[0057] PP-R 2#: 230°C, melt flow rate of 5.0 g / 10 min at 2.16 kg; PP-R0508, Kingfa Technology Co., Ltd.

[0058] Homopolymer polypropylene resin (PP-H):

[0059] PP-H 1#: 230℃, melt flow rate is 14g / 10min under 2.16kg conditions; HJ4012, Korea Petrochemical Corporation.

[0060] PP-H 2#: 230℃, melt flow rate 3.3g / 10min at 2.16kg; T30S, PetroChina.

[0061] β-nucleating agent: TMB-5, Shanxi Institute of Fine Chemicals.

[0062] Magnetic particles: Nano iron oxide magnetic powder, average particle size 20-30nm, F809544, Shanghai McLean Biochemical Technology Co., Ltd.

[0063] Nanofibers:

[0064] Nano polyamide fiber: single filament diameter 6nm, PA6 M2400, Guangdong Xinhui Dajinlun Company.

[0065] Nano polyimide fiber: single filament diameter 10 nm; SOP, Jiangsu Xiannuo New Materials Technology Co., Ltd.

[0066] Silane coupling agent: KH-550, KH-602, KH-792, Shandong Yousuo Chemical Technology Co., Ltd.; mass ratio is 1:1:1.

[0067] Example 1

[0068] A composite PPR pipe resistant to low temperature cracking comprises the following components by mass fraction: 95% of random copolymer polypropylene resin and 5% of nucleating agent composite masterbatch.

[0069] The nucleating agent composite masterbatch comprises the following components in terms of mass fraction: 60% of basic masterbatch and 40% of magnetic masterbatch.

[0070] The basic masterbatch comprises the following components by mass fraction: 95% homopolymer polypropylene resin and 5% modified nucleating agent.

[0071] The magnetic masterbatch comprises the following components by mass fraction: 91% of random copolymerized polypropylene resin, 5% of modified nucleating agent and 4% of magnetic fiber.

[0072] Among them, the random copolymer polypropylene resin is selected from PP-R 1#; and the homopolymer polypropylene resin is selected from PP-H 1#.

[0073] The method for preparing the composite PPR pipe resistant to low temperature cracking comprises the following steps:

[0074] (1) Preparation of modified β-nucleating agent: Add β-nucleating agent and appropriate amount of acetone into a reaction kettle and stir to form a suspension. Add silane coupling agent while stirring the suspension. The mass ratio of β-nucleating agent to silane coupling agent is 100:1. Continue stirring until the reaction is complete. Filter, wash and dry the product to obtain the modified nucleating agent.

[0075] (2) Preparation of magnetic fibers: Add nanofibers to an appropriate amount of dimethyl sulfoxide and stir to form a uniform nanofiber dispersion, wherein the nanofibers are selected from nano-polyamide fibers, and then disperse nano-iron oxide magnetic powder in the nanofiber dispersion to form a composite solution, wherein the mass ratio of nano-iron oxide magnetic powder to nanofiber is controlled to be 1:2, and methyl methacrylate is added to the composite solution in an amount of 45 wt % of the nanofibers, and heated and stirred at 75°C. After the reaction in the composite solution is complete, filter the solution, wash and dry the filtered product to obtain magnetic fibers for later use.

[0076] (3) preparing a basic masterbatch: uniformly mixing the modified nucleating agent and the homopolymerized polypropylene resin, then feeding the mixture into an extruder for mixing, extruding at 170-190° C., cooling, and cutting and granulating to obtain a basic masterbatch;

[0077] (4) preparing magnetic masterbatch: uniformly mixing the modified nucleating agent with the random copolymerized polypropylene resin and the magnetic fiber, then putting the mixture into an extruder for mixing, extruding at 170-190° C., cooling, and cutting and granulating to obtain the magnetic masterbatch;

[0078] (5) preparing a nucleating agent composite masterbatch: uniformly mixing the base masterbatch and the magnetic masterbatch to obtain a nucleating agent composite masterbatch;

[0079] (6) Processing and molding: the nucleating agent composite masterbatch is uniformly mixed with the random copolymer polypropylene resin, and then the mixture is put into a pipe extruder for mixing, extruded at 190-220° C., and molded through a mold at 210-230° C. The molded pipe is water-cooled and shaped (vacuum degree -0.03 MPa) to obtain a PPR pipe; wherein a magnetic cylinder with magnetic properties is arranged outside the barrel of the pipe extruder, and the magnetic cylinder extends to the extrusion nozzle of the pipe extruder; a magnetic plate with magnetic properties surrounding the mold cavity is arranged in the mold;

[0080] (7) Heat treatment: After the PPR pipe is cut into fixed lengths, it is heated to 100° C. for heat treatment for 4 hours, and the PPR pipe after heat treatment is naturally cooled and taken out.

[0081] Example 2

[0082] A composite PPR pipe resistant to low temperature cracking, which is different from Example 1 in that the random copolymer polypropylene resin is selected from PP-R 2#.

[0083] Example 3

[0084] A composite PPR pipe resistant to low temperature cracking, which is different from Example 1 in that the homopolymer polypropylene resin is selected from PP-H 2#.

[0085] Example 4

[0086] A composite PPR pipe resistant to low temperature cracking, which is different from Example 1 in that the nanofiber is selected from nano polyimide fiber.

[0087] Comparative Example 1

[0088] A composite PPR pipe is different from Example 1 in that it comprises the following components by mass fraction: 95% of random copolymer polypropylene resin and 5% of basic masterbatch.

[0089] The basic masterbatch comprises the following components by mass fraction: 95% homopolymer polypropylene resin and 5% modified nucleating agent.

[0090] The preparation method of the composite PPR pipe comprises the following steps:

[0091] (1) Preparation of modified β-nucleating agent: Add β-nucleating agent and appropriate amount of acetone into a reaction kettle and stir to form a suspension. Add silane coupling agent while stirring the suspension. The mass ratio of β-nucleating agent to silane coupling agent is 100:1. Continue stirring until the reaction is complete. Filter, wash and dry the product to obtain the modified nucleating agent.

[0092] (2) preparing a basic masterbatch: uniformly mixing the modified nucleating agent and the homopolymerized polypropylene resin, then feeding the mixture into an extruder for mixing, extruding at 170-190° C., cooling, and cutting and granulating to obtain a basic masterbatch;

[0093] (3) Processing and molding: the base masterbatch is uniformly mixed with the random copolymer polypropylene resin, and then the mixture is put into a pipe extruder for mixing, extruded at 190-220° C., and molded through a mold at 210-230° C. The molded pipe is water-cooled and shaped (vacuum degree -0.03 MPa) to obtain a PPR pipe;

[0094] (4) Heat treatment: After cutting the PPR pipe into fixed lengths, heat it to 100°C for 4 hours. After the heat-treated PPR pipe is naturally cooled, it is taken out.

[0095] Comparative Example 2

[0096] A composite PPR pipe is different from Example 1 in that it comprises the following components by mass fraction: 93% of random copolymer polypropylene resin, 5% of basic masterbatch, and 2% of magnetic fiber.

[0097] The basic masterbatch comprises the following components by mass fraction: 95% homopolymer polypropylene resin and 5% modified nucleating agent.

[0098] The preparation method of the composite PPR pipe comprises the following steps:

[0099] (1) Preparation of modified β-nucleating agent: Add β-nucleating agent and appropriate amount of acetone into a reaction kettle and stir to form a suspension. Add silane coupling agent while stirring the suspension. The mass ratio of β-nucleating agent to silane coupling agent is 100:1. Continue stirring until the reaction is complete. Filter, wash and dry the product to obtain the modified nucleating agent.

[0100] (2) Preparation of magnetic fibers: Add nanofibers to an appropriate amount of dimethyl sulfoxide and stir to form a uniform nanofiber dispersion, wherein the nanofibers are selected from nano-polyamide fibers, and then disperse nano-iron oxide magnetic powder in the nanofiber dispersion to form a composite solution, wherein the mass ratio of nano-iron oxide magnetic powder to nanofiber is controlled to be 1:2, and methyl methacrylate is added to the composite solution in an amount of 45 wt % of the nanofibers, and heated and stirred at 75°C. After the reaction in the composite solution is complete, filter the solution, wash and dry the filtered product to obtain magnetic fibers for later use.

[0101] (3) preparing a basic masterbatch: uniformly mixing the modified nucleating agent and the homopolymerized polypropylene resin, then feeding the mixture into an extruder for mixing, extruding at 170-190° C., cooling, and cutting and granulating to obtain a basic masterbatch;

[0102] (4) Processing and molding: the base masterbatch, magnetic fiber and random copolymer polypropylene resin are mixed uniformly, and then the mixture is put into a pipe extruder for mixing, extruded at 190-220°C and molded through a mold at 210-230°C. The molded pipe is water-cooled and shaped (vacuum degree -0.03MPa) to obtain a PPR pipe; wherein a magnetic cylinder with magnetic properties is arranged outside the barrel of the pipe extruder, and the magnetic cylinder extends to the extrusion nozzle of the pipe extruder; a magnetic plate with magnetic properties surrounding the mold cavity is arranged in the mold;

[0103] (5) Heat treatment: After the PPR pipe is cut into fixed lengths, it is heated to 100° C. for heat treatment for 4 hours, and the PPR pipe after heat treatment is naturally cooled and taken out.

[0104] Performance Testing

[0105] 1. Number of fractures in impact and drop tests

[0106] The PPR pipe samples (with a specification of 6 branches and a length of 1 m) prepared in the above-mentioned Examples 1-4 and Comparative Examples 1-2 were subjected to impact tests and drop tests, and the number of ruptures in the impact tests and drop tests was recorded as shown in Table 1.

[0107] The testing method of the impact experiment is: in a -30℃ environment, use an R10 hammer weighing 1kg to drop the PPR pipe from a height of 0.5m to observe whether the PPR pipe is broken. A total of 30 groups of experiments are carried out and the number of PPR pipe breaks is recorded.

[0108] The test method of the drop test is: after placing the PPR pipe in a -30℃ environment for 24 hours, the PPR pipe is freely dropped from a height of 2m to the ground to observe whether the PPR pipe is broken. A total of 30 groups of experiments are carried out and the number of PPR pipe breaks is recorded.

[0109] Table 1

[0110]

[0111] The results show that the PPR pipe produced by the technical solution of the present invention has no cracks in the impact test and the drop test in a -30°C environment, and the yield rate is 100%.

[0112] 2. Impact height test and drop height test

[0113] The PPR pipe samples of the above-mentioned Examples 1-4 and Comparative Examples 1-2 were subjected to an impact height test and a drop height test. The experimental results are shown in Table 2.

[0114] Impact height test: In a -30℃ environment, use an R10 hammer weighing 1kg to drop the PPR pipe from a certain height to observe and record the highest height at which the PPR pipe does not break after the impact. After a total of 30 sets of experiments, take the average value of the recorded data.

[0115] Drop height test: After placing the PPR pipe in a -30℃ environment for 24 hours, drop the PPR pipe freely from a certain height to the ground, observe and record the highest height at which the PPR pipe does not break after free falling. After conducting 30 sets of experiments, take the average value of the recorded data.

[0116] Table 2

[0117] PPR pipe Impact height test (m) Drop height test (m) Example 1 4.2 13.7 Example 2 4.5 15.1 Example 3 3.9 14.3 Example 4 4.4 13.9 Comparative Example 1 0.7 3.1 Comparative Example 2 1.1 4.5

[0118] The results show that the drop hammer impact height of the PPR pipe prepared by the present invention is above 3.9m, the drop height is above 13.7m, and the low-temperature toughness is excellent. It is proved that the PPR pipe prepared by the present invention can significantly improve the toughness of the outer surface of the PPR pipe by increasing the density of the modified nucleating agent on the side close to the outer surface of the PPR pipe, and forming a nanofiber layer on the outer surface of the PPR pipe through the magnetic fiber, thereby achieving the purpose of improving the low-temperature brittleness of the PPR pipe.

[0119] Comparative Example 1 does not contain magnetic fibers, and cannot form a fiber layer on the surface for protection. In addition, the modified nucleating agent in the PPR pipe is evenly dispersed in the entire PPR, resulting in the surface toughness failing to meet the requirements and being brittle at low temperatures.

[0120] In Comparative Example 2, the modified nucleating agent and magnetic fiber were not fully polymerized. Although a fiber layer was formed on the surface for protection, the density of the modified nucleating agent on the side close to the outer surface of the PPR pipe was not effectively increased, resulting in lower surface toughness of the PPR pipe.

[0121] 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 nucleating agent composite masterbatch, characterized in that: The composition comprises the following components in parts by weight: 40-80 parts of basic masterbatch and 20-60 parts of magnetic masterbatch; The base masterbatch comprises homopolymer polypropylene resin and modified nucleating agent, wherein the content of the modified nucleating agent is 3-6wt.%; The magnetic masterbatch comprises random copolymerized polypropylene resin, magnetic fiber and modified nucleating agent, wherein the content of the modified nucleating agent is 3-6wt.%, and the content of the magnetic fiber is 3-5wt.%.

2. The nucleating agent composite masterbatch according to claim 1, characterized in that: The modified nucleating agent is a beta nucleating agent modified by a silane coupling agent.

3. The nucleating agent composite masterbatch according to claim 2, characterized in that: The beta nucleating agent is selected from TMB-5 and / or NAB-83C.

4. The nucleating agent composite masterbatch according to claim 1, characterized in that: The magnetic fiber is a composite of magnetic particles and nanofibers.

5. The nucleating agent composite masterbatch according to claim 4, characterized in that: The mass ratio of the magnetic particles to the nanofibers is 1:(1-3).

6. The nucleating agent composite masterbatch according to claim 4 or 5, characterized in that: The nanofiber is selected from one or more of nano-polyamide fiber, nano-polyphenylene sulfide fiber, nano-polyimide fiber or nano-polyetheretherketone fiber.

7. A composite PPR pipe, characterized in that: The invention comprises the nucleating agent composite masterbatch as described in any one of claims 1 to 6.

8. The composite PPR pipe according to claim 7, characterized in that: The invention comprises the following components in parts by weight: 92-97 parts of random copolymerized polypropylene resin and 3-8 parts of nucleating agent composite masterbatch.

9. A method for preparing the composite PPR pipe according to claim 7 or 8, characterized in that: The following steps are involved: S1, uniformly mixing the modified nucleating agent and the homopolymerized polypropylene resin, and melt-extruding and granulating to obtain a basic masterbatch; S2, uniformly mixing the modified nucleating agent, random copolymerized polypropylene resin and magnetic fiber, and melt-extruding and granulating to obtain a magnetic masterbatch; S3, uniformly mixing the basic masterbatch in step S1 and the magnetic masterbatch in step S2 to obtain a nucleating agent composite masterbatch; S4, uniformly mixing the nucleating agent composite masterbatch and the random copolymer polypropylene resin, melt-extruded under an external magnetic field, molded, and heat-treated to obtain the composite PPR pipe.

10. The method for preparing the composite PPR pipe according to claim 9, characterized in that: The heat treatment temperature is 80-120° C. and the heat treatment time is 3-5 hours.

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