A polyolefin composition having a ptc effect, a process for its production and an article

Abstract

The application provides a polyolefin composition with PTC effect, a preparation method thereof and an article, and belongs to the technical field of polymer thermal sensitive materials, and the composition comprises the following components in parts by weight: 100 parts of polyolefin resin, 3.0-6.0 parts of carbon black, 2.0-4.0 parts of hydrotalcite-coated modified carbon nanotube, 3.0-5.0 parts of toughening agent, 0.3-0.4 parts of antioxidant and 0.02-0.04 parts of processing aid. The hydrotalcite is used to coat and modify the carbon nanotube, and the modified carbon nanotube is used in cooperation with acetylene carbon black, so that the produced polyethylene composition has a persistent PTC effect, and the strength of the composition is high and the composition is easy to be processed and molded.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high molecular heat-sensitive materials, in particular to a polyolefin composition for producing self-limiting temperature material, a preparation method thereof and an article containing the same. BACKGROUND

[0002] The conductive material with PTC (Positive Temperature Coefficient) effect is one of the functional high molecular materials which is developing rapidly at present. The resistance of the material increases with the increase of temperature, and the passing current can be reduced or even cut off when the temperature increases, and the circuit is restored when the temperature decreases, preventing the circuit from overheating and overcurrent, and achieving the effect of automatic temperature control. The PTC material can be widely used in the fields of self-limiting temperature, overcurrent protection components and devices such as petroleum and chemical fluid conveying pipelines, heating floors and heat tracing bands.

[0003] At present, the PTC material mainly includes ceramic-based and polymer-based two types. The polymer-based PTC material is mainly composed of resin polymer and conductive additive, and has the advantages of light weight, low cost and easy forming, among which the polyolefin / carbon black type PTC material is most widely used.

[0004] The polyolefin / carbon black type PTC material uses carbon black as a conductive additive. In order to make the material have PTC effect, the current addition amount of carbon black is usually high, generally more than 15% by weight. The high filling amount makes the performance of the PTC material decrease obviously, and the processing is difficult due to the increase of the viscosity of the system. In addition, the high content of carbon black also leads to poor quality stability of the material, and the PTC effect will decay or even disappear after a period of use. SUMMARY

[0005] The present application provides a polyolefin composition with persistent PTC effect, which has excellent performance and is very easy to process and form.

[0006] One of the objects of the present application is to provide a polyolefin composition with PTC effect.

[0007] The second object of the present application is to provide a preparation method of the polyolefin composition with PTC effect.

[0008] The third object of the present application is to provide an article containing the polyolefin composition with PTC effect.

[0009] In order to achieve the above objects of the present application, the following technical solutions are adopted:

[0010] In a first aspect, the present application provides a polyolefin composition with PTC effect, comprising the following components in parts by weight: 100 parts of polyolefin resin, 3.0-6.0 parts of carbon black, 2.0-4.0 parts of hydrotalcite-coated modified carbon nanotube, 3.0-5.0 parts of toughening agent, 0.3-0.4 parts of antioxidant, and 0.02-0.04 parts of processing aid.

[0011] The components are described in detail as follows:

[0012] The source of the polyolefin resin is not particularly limited and can be commercially available or prepared by known methods in the art.

[0013] Preferably, the polyolefin resin can include but is not limited to polyethylene, polypropylene, poly-1-butene, ethylene-vinyl acetate copolymer, etc., and preferably is a high-density polyethylene (HDPE) resin; preferably, the high-density polyethylene (HDPE) resin has a melt flow rate of 10.0-15.0 g / 10 min (190°C, 21.6 kg), such as HDPE DGDB2480 from Qilu Petrochemical Company, but is not limited thereto.

[0014] The polyolefin resin is added in an amount of 100 parts.

[0015] The carbon black can include but is not limited to acetylene black, pigment black, reinforcing black, etc., and preferably is acetylene black; preferably, the acetylene black has a particle size of 40-50 nm and an oil absorption value of 3.0 mL / g, such as acetylene black from Zhejiang Chun'an Chemical Factory, but is not limited thereto.

[0016] The carbon black is added in an amount of 3-6 parts, for example, 3 parts, 4 parts, 5 parts, or 6 parts, but is not limited thereto.

[0017] The hydrotalcite-coated modified carbon nanotube is obtained by activating and modifying carbon nanotubes (CNT) and coating with hydrotalcite.

[0018] Preferably, the hydrotalcite-coated modified carbon nanotube is prepared by the following method:

[0019] The carbon nanotubes are treated in a strong acid solution to obtain modified carbon nanotubes, which are dispersed in an aqueous phase by washing to neutral to obtain dispersion 1;

[0020] The hydrotalcite is dispersed in an aqueous phase, and benzoic acid is added to obtain dispersion 2;

[0021] Dispersion 2 is added to dispersion 1 and mixed thoroughly to obtain the hydrotalcite-coated modified carbon nanotube.

[0022] Specifically, the hydrotalcite-coated modified carbon nanotube is prepared by the following method:

[0023] The carbon nanotubes are added to concentrated nitric acid (concentration of 80% to 85%) in an amount of 10% to 15% by weight of the carbon nanotubes, heated to 85°C to 90°C, constant temperature stirring for 45 min to 50 min, cooling to room temperature, water washing to neutral, and dispersed in the aqueous phase to obtain dispersion 1;

[0024] Polyoxyethylene sorbitan monostearate (Tween-60) is added to the aluminum magnesium hydrotalcite in deionized water in an amount of 2% to 3% by weight, heated to 60°C to 70°C, the aluminum magnesium hydrotalcite is further dispersed in the aqueous phase to form dispersion 2, benzoic acid is added in an amount of 5% to 8% by weight of the aluminum magnesium hydrotalcite, after 30 min of reaction, sodium hydroxide is added to adjust the pH value to 7.5 to 8.0, and the temperature is cooled to room temperature to obtain dispersion 2.

[0025] Dispersion 2 (solid content of 8% to 10% of the solid content of dispersion 1) is added dropwise to dispersion 1, stirred thoroughly for 10 min, centrifuged and dehydrated, and dried at 130°C to 140°C to obtain the hydrotalcite-coated modified carbon nanotubes.

[0026] The amount of hydrotalcite-coated modified carbon nanotubes added is 2 to 4 parts, for example, it can be 2 parts, 2.5 parts, 3 parts, 3.5 parts, or 4 parts, but is not limited thereto.

[0027] The toughening agent can be a toughening resin known in the art, including but not limited to POE, EVA, and PU.

[0028] Preferably, the toughening agent is a POE resin, and the Shore A hardness is 52 ～ 60, such as POE ENGAGE 8842 of Dow Chemical Company, but is not limited thereto.

[0029] The amount of toughening agent added is 3 to 5 parts, for example, it can be 3 parts, 4 parts, or 5 parts, but is not limited thereto.

[0030] The antioxidant can be an antioxidant known in the art, including but not limited to hindered phenolic antioxidants and hindered amine antioxidants.

[0031] Preferably, the antioxidant is tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester, such as antioxidant Irganox 1010 of BASF Company, but is not limited thereto.

[0032] The amount of antioxidant added is 0.3 to 0.4 parts, for example, it can be 0.3 parts, 0.32 parts, 0.35 parts, 0.38 parts, or 0.4 parts, but is not limited thereto.

[0033] The processing aid can be an aid known in the art, including but not limited to silicone processing aids and fluorine-containing organic processing aids.

[0034] Preferably, the processing aid is a fluorine-containing aid, such as LANPOLY PPA2800 of Lu Poly Polymer Technology Co., Ltd., but is not limited thereto.

[0035] The processing aid is added in an amount of 0.02-0.04 parts, for example, 0.02 parts, 0.03 parts, 0.04 parts, but is not limited thereto.

[0036] In a second aspect, the present application provides a preparation method of the polyolefin composition with PTC effect, comprising the following steps: mixing the above-mentioned polyolefin composition with PTC effect to form a special material for polyolefin composition.

[0037] Specifically, the preparation method comprises:

[0038] The polyolefin resin, carbon black, hydrotalcite-coated modified carbon nanotube, toughening agent, antioxidant, and processing aid are added to a banbury mixer, plasticized at 190°C for 10-12 min, sheeted through a two-roll mill, and pelletized through a pelletizer to form a special material.

[0039] In a third aspect, the present application provides an article containing the polyolefin composition with PTC effect.

[0040] The article can be a self-limiting temperature product such as a heat trace or a heating floor.

[0041] Advantages

[0042] The present application uses hydrotalcite with etching to modify carbon nanotubes, which is used in combination with acetylene carbon black to produce a polyethylene composition with persistent PTC effect, and the composition has high strength and is easy to process and form.

[0043] The present application has been described in detail above, but the above-mentioned embodiments are only illustrative in nature and are not intended to limit the present application. In addition, the present application is not limited by any theory described in the foregoing prior art or summary of the application or in the following examples. DETAILED DESCRIPTION

[0044] The present application will be further described below in conjunction with examples, and it should be noted that the following examples are provided only for illustrative purposes and do not constitute a limitation on the scope of the present application.

[0045] Unless otherwise specified, the raw materials, reagents, and methods used in the examples are conventional raw materials, reagents, and methods in the art.

[0046] The raw materials involved in the examples and comparative examples are as follows:

[0047] The high-density polyethylene (HDPE) resin was HDPE DGDB2480 from Qilu Petrochemical Company, with a melt flow rate of 10.0-12.0 g / 10 min (190°C, 21.6 kg).

[0048] The carbon black was acetylene carbon black from Zhejiang Chun'an Chemical Factory, with a particle size of 40-50 nm and an oil absorption value of 3.0 mL / g.

[0049] The toughening agent was POE ENGAGE 8842 from Dow Chemical Company, with a Shore A hardness of 54.

[0050] The antioxidant was antioxidant Irganox 1010 from BASF Company.

[0051] The processing aid was LANPOLY PPA2800 from Lu Poly Polymer Technology Company.

[0052] Example 1:

[0053] Preparation of modified carbon nanotubes:

[0054] 1. 200 g of carbon nanotubes were added to 85% concentrated nitric acid at a concentration of 12% of the weight of the carbon nanotubes, heated to 85°C, stirred at a constant temperature for 50 min, cooled to room temperature, washed with water to neutral, and then dispersed in water again to obtain an aqueous dispersion 1 (solid content of 35%).

[0055] 2. 500 g of deionized water was added to 2.5% of the weight of aluminum-magnesium hydrotalcite polyoxyethylene sorbitan monostearate (Tween-60), heated to 65°C, and then 100 g of aluminum-magnesium hydrotalcite was added and dispersed in the aqueous phase to form a dispersion, 6% of the weight of aluminum-magnesium hydrotalcite was added, and after 30 min of reaction, sodium hydroxide was added to adjust the pH value to 7.8, and then cooled to room temperature to obtain dispersion 2 (solid content of 18%, with water loss).

[0056] 3. Dispersion 2 (solid content weight was 9% of the total solid content of dispersion 1) was added dropwise to dispersion 1, stirred thoroughly for 10 min, then centrifuged and dehydrated, and dried at 135°C to obtain the modified carbon nanotubes.

[0057] The polyethylene composition with a persistent PTC effect was composed of the following components (by weight, the same below):

[0058] 100 parts of high-density polyethylene (HDPE) resin, 5.0 parts of carbon black, 3.0 parts of modified carbon nanotubes, 4.0 parts of toughening agent, 0.3 parts of antioxidant, and 0.02 parts of processing aid.

[0059] Preparation method of the polyethylene composition with a persistent PTC effect:

[0060] HDPE resin and various additives were added into a mixing mill, plasticized at 190°C for 10 minutes, sheeted by a double roll mill, and pelletized by a pelletizer to form a special material.

[0061] Performance test method:

[0062] The special material was pressed into standard samples by a molding machine, and then each performance was tested.

[0063] Tensile strength and elongation at break: tested according to GB / T 1040-2008.

[0064] Volume resistivity: tested according to GB / T 1410-2006.

[0065] PTC strength: the resistance value of the sample at different temperatures was tested by a direct current double-arm bridge, the logarithmic value of the resistivity was plotted against the temperature to obtain the resistivity-temperature curve of the sample, and the PTC strength was equal to the logarithmic value of the ratio of the maximum resistivity in the curve to the resistivity at room temperature.

[0066] Endurance test: the resistivity change was tested after continuous power supply for 10 days.

[0067] The performance test results are shown in Table 1.

[0068] Example 2:

[0069] Preparation of modified carbon nanotubes:

[0070] 1. 200 g of carbon nanotubes were added into 82% concentrated nitric acid with a concentration of 15% of the weight of the carbon nanotubes, heated to 90°C, stirred at a constant temperature for 45 min, cooled to room temperature, washed to neutral, and then dispersed in water to obtain water dispersion 1 (solid content of 35%).

[0071] 2. 500 g of deionized water was added with 3.0% of polyoxyethylene sorbitan monostearate (Tween-60) of the weight of the aluminum-magnesium hydrotalcite, heated to 65°C, and then the aluminum-magnesium hydrotalcite was added and dispersed in the water phase to form a dispersion, 7% of benzoic acid of the weight of the aluminum-magnesium hydrotalcite was added, reacted for 30 min, and then sodium hydroxide was added to adjust the pH value to 8.0, and then cooled to room temperature to obtain dispersion 2 (solid content of 20%, with water loss).

[0072] 3. Dispersion 2 (solid content weight was 10% of the total solid content of dispersion 1) was added dropwise into dispersion 1, stirred for 10 min, centrifuged and dehydrated, and then dried at 140°C to obtain the modified carbon nanotubes.

[0073] The polyethylene composition with persistent PTC effect was composed of the following components (by weight, the same below):

[0074] High density polyethylene (HDPE) resin 100 parts, carbon black 6.0 parts, modified carbon nanotube 2.0 parts, toughening agent 3.0 parts, antioxidant 0.3 parts, processing aid 0.04 parts.

[0075] Preparation method of polyethylene composition with persistent PTC effect:

[0076] HDPE resin and various additives are added to a banbury mixer, plasticized at 190℃ for 10 minutes, sheeted through a two-roll mill, and pelletized through a pelletizer to form a special material.

[0077] The performance testing method is the same as in Example 1, and the performance test results are shown in Table 1.

[0078] Example 3:

[0079] Preparation of modified carbon nanotube:

[0080] 1. 200g of carbon nanotube is added to 80% concentrated nitric acid with a concentration of 10% of the weight of the carbon nanotube, heated to 85℃, stirred at a constant temperature for 45 minutes, cooled to room temperature, washed to neutral with water, and dispersed in water again to obtain water dispersion 1 (solid content 35%).

[0081] 2. Add 2.0% of polyoxyethylene sorbitan monostearate (Tween-60) to deionized water, heat to 60℃, then add aluminum magnesium hydrotalcite to the water phase to form a dispersion, add 6% of benzoic acid based on the weight of aluminum magnesium hydrotalcite, add sodium hydroxide to adjust the pH to 7.5 after 30 minutes of reaction, and cool to room temperature to obtain dispersion 2 (solid content 18%, with water loss).

[0082] 3. Add dispersion 2 (solid content weight is 8% of the total solid content of dispersion 1) dropwise to dispersion 1, stir thoroughly for 10 minutes, centrifuge and dehydrate, and dry at 130℃ to obtain modified carbon nanotube.

[0083] The polyethylene composition with persistent PTC effect is composed of the following components (weight parts, the same below):

[0084] High density polyethylene (HDPE) resin 100 parts, carbon black 6.0 parts, modified carbon nanotube 2.0 parts, toughening agent 3.0 parts, antioxidant 0.3 parts, processing aid 0.04 parts.

[0085] Preparation method of polyethylene composition with persistent PTC effect:

[0086] HDPE resin and various additives are added to a banbury mixer, plasticized at 190℃ for 12 minutes, sheeted through a two-roll mill, and pelletized through a pelletizer to form a special material.

[0087] The performance test method is the same as that of Example 1, and the performance test results are shown in Table 1.

[0088] Example 4:

[0089] Preparation of modified carbon nanotubes:

[0090] 1. 200 g of carbon nanotubes were added to 13% of the weight of the carbon nanotubes of 85% concentrated nitric acid, heated to 90°C, stirred at constant temperature for 48 min, cooled to room temperature, washed with water to neutral, and then dispersed in water again to obtain an aqueous dispersion 1 (solid content of 35%).

[0091] 2. 2.5% of the weight of the aluminum-magnesium hydrotalcite of polyoxyethylene sorbitan monostearate (Tween-60) was added to deionized water, heated to 65°C, and then the aluminum-magnesium hydrotalcite was added and dispersed in the aqueous phase to form a dispersion, 5% of the weight of the aluminum-magnesium hydrotalcite of benzoic acid was added, reacted for 30 min, and then sodium hydroxide was added to adjust the pH value to 7.5, and then cooled to room temperature to obtain a dispersion 2 (solid content of 20%, with water loss).

[0092] 3. The dispersion 2 (solid content weight of 9% of the total solid content of the dispersion 1) was added dropwise to the dispersion 1, stirred for 10 min, and then centrifuged and dehydrated, and then dried at 130°C to obtain the modified carbon nanotubes.

[0093] The polyethylene composition with a persistent PTC effect is composed of the following components (parts by weight, the same below):

[0094] 100 parts of high-density polyethylene (HDPE) resin, 4.0 parts of carbon black, 3.5 parts of modified carbon nanotubes, 4.0 parts of toughening agent, 0.4 parts of antioxidant, and 0.02 parts of processing aid.

[0095] Preparation method of the polyethylene composition with a persistent PTC effect:

[0096] The HDPE resin and various additives were added to a banbury mixer, plasticized at 190°C for 10 min, sheeted through a double-roller mill, and then pelletized through a pelletizer to form a special material.

[0097] The performance test method is the same as that of Example 1, and the performance test results are shown in Table 1.

[0098] Example 5:

[0099] Preparation of modified carbon nanotubes:

[0100] 1. 200 g of carbon nanotubes were added to 14% of the weight of the carbon nanotubes of 82% concentrated nitric acid, heated to 90°C, stirred at constant temperature for 46 min, cooled to room temperature, washed with water to neutral, and then dispersed in water again to obtain an aqueous dispersion 1 (solid content of 35%).

[0101] 2. Add 2.0% by weight of polyoxyethylene sorbitan monostearate (Tween-60) to deionized water, heat to 60°C, then add aluminum-magnesium hydrotalcite to disperse in the aqueous phase to form a dispersion, add 6% by weight of benzoic acid to aluminum-magnesium hydrotalcite, react for 30 min, add sodium hydroxide to adjust the pH to 7.7, cool to room temperature, and obtain dispersion 2 (solid content is 19%, with water loss).

[0102] 3. Add dispersion 2 (with a solid content of 10% of the total solid content of dispersion 1) dropwise to dispersion 1, stir thoroughly for 10 minutes, centrifuge to remove water, and dry at 135℃ to obtain modified carbon nanotubes.

[0103] The polyethylene composition with a sustained PTC effect consists of the following components (parts by weight, the same below):

[0104] 100 parts high-density polyethylene (HDPE) resin, 5.0 parts carbon black, 2.5 parts modified carbon nanotubes, 3.5 parts toughening agent, 0.3 parts antioxidant, and 0.03 parts processing aid.

[0105] Method for preparing polyethylene compositions with persistent PTC effect:

[0106] HDPE resin and various additives are added to an internal mixer and mixed and plasticized at 190°C for 10 minutes. The mixture is then sheeted through a two-roll mill and granulated by a granulator to form a special material.

[0107] The performance testing method is the same as in Example 1, and the performance test results are shown in Table 1.

[0108] Table 1 Performance Test Results

[0109] Test item Example 1 Example 2 Example 3 Example 4 Example 5 Tensile strength, MPa 26.5 26.6 27.2 26.9 26.8 Elongation at break, % 684 680 704 695 695 Volume resistivity, Ω-m 850 876 838 844 862 Volume resistivity after durability test, Ω-m 854 879 842 851 867 Change rate of volume resistivity after durability test, % 0.5 0.3 0.5 0.8 0.6 PTC strength 5.2 5.5 4.9 5.1 5.3

[0110] Comparative Example 1:

[0111] Preparation of modified carbon nanotubes: Same as in Example 1.

[0112] The polyethylene composition comprises the following components (parts by weight, the same below):

[0113] 100 parts high-density polyethylene (HDPE) resin, 8.0 parts modified carbon nanotubes, 4.0 parts toughening agent, 0.3 parts antioxidant, and 0.02 parts processing aid.

[0114] Preparation method of polyethylene composition:

[0115] HDPE resin and various additives are added to an internal mixer and mixed and plasticized at 190°C for 10 minutes. The mixture is then sheeted through a two-roll mill and granulated by a granulator to form a special material.

[0116] The performance testing method is the same as in Example 1, and the performance test results are shown in Table 2.

[0117] Comparative Example 2:

[0118] The polyethylene composition comprises the following components (parts by weight, the same below):

[0119] 100 parts high-density polyethylene (HDPE) resin, 5.0 parts carbon black, 3.0 parts carbon nanotubes, 4.0 parts toughening agent, 0.3 parts antioxidant, and 0.02 parts processing aid.

[0120] Preparation method of polyethylene composition:

[0121] HDPE resin and various additives are added to an internal mixer and mixed and plasticized at 190°C for 10 minutes. The mixture is then sheeted through a two-roll mill and granulated by a granulator to form a special material.

[0122] The performance testing method is the same as in Example 1, and the performance test results are shown in Table 2.

[0123] Comparative Example 3:

[0124] The polyethylene composition comprises the following components (parts by weight, the same below):

[0125] 100 parts high-density polyethylene (HDPE) resin, 8.0 parts carbon black, 4.0 parts toughening agent, 0.3 parts antioxidant, and 0.02 parts processing aid.

[0126] Preparation method of polyethylene composition:

[0127] HDPE resin and various additives are added to an internal mixer and mixed and plasticized at 190°C for 10 minutes. The mixture is then sheeted through a two-roll mill and granulated by a granulator to form a special material.

[0128] The performance testing method is the same as in Example 1, and the performance test results are shown in Table 2.

[0129] Comparative Example 4:

[0130] The polyethylene composition comprises the following components (parts by weight, the same below):

[0131] 100 parts high-density polyethylene (HDPE) resin, 23.0 parts carbon black, 4.0 parts toughening agent, 0.3 parts antioxidant, and 0.02 parts processing aid.

[0132] Preparation method of polyethylene composition:

[0133] HDPE resin and various additives are added to an internal mixer and mixed and plasticized at 190°C for 10 minutes. The mixture is then sheeted through a two-roll mill and granulated by a granulator to form a special material.

[0134] The performance testing method is the same as in Example 1, and the performance test results are shown in Table 2.

[0135] Table 2 Performance Test Results

[0136] Test item Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Tensile strength, MPa 26.9 26.7 26.7 22.4 Elongation at break, % 682 684 688 490 Volume resistivity, Ω-m 286 584 3.2 x 10 5 ]]> 1206 Volume resistivity after durability test, Ω-m － － － 1358 Change rate of volume resistivity after durability test, % － － － 12.6 PTC strength None None None None 4.1

[0137] - Indicates that it has not been tested.

[0138] Comparative Example 1 used modified carbon nanotubes as the conductive agent, with the remaining components the same as in Example 1; Comparative Example 2 used unmodified carbon nanotubes and acetylene black synergistically as the conductive agent, with the remaining components the same as in Example 1; Comparative Example 3 used only acetylene black as the conductive agent, and none of these results in the material exhibiting the PTC effect, thus it could not be used as a PTC material. Comparative Example 4 required 23 parts of acetylene black to produce the PTC effect, and the PTC effect durability of the material was poor.

[0139] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.

Claims

1. A polyolefin composition exhibiting a PTC effect, characterized in that, The following components are included by weight: 100 parts polyolefin resin, 3.0 to 6.0 parts carbon black, 2.0 to 4.0 parts hydrotalcite-coated modified carbon nanotubes, 3.0 to 5.0 parts toughening agent, 0.3 to 0.4 parts antioxidant, and 0.02 to 0.04 parts processing aid. The hydrotalcite-coated modified carbon nanotubes were prepared by the following method: Carbon nanotubes were added to concentrated nitric acid at a weight of 10%–15% of the carbon nanotubes, heated to 85°C–90°C, stirred at a constant temperature for 45–50 minutes, cooled to room temperature, and washed with water until neutrally dispersed in the aqueous phase to obtain dispersion 1. Add 2%–3% by weight of polyoxyethylene sorbitan monostearate to deionized water, heat to 60℃–70℃, then add aluminum magnesium hydrotalcite to disperse in the aqueous phase to form a dispersion, add 5%–8% by weight of benzoic acid to aluminum magnesium hydrotalcite, react for 30 min, adjust the pH to 7.5–8.0, cool to room temperature, and obtain dispersion 2; Dispersion 2 was added dropwise to dispersion 1. The solid content of dispersion 2 was 8% to 10% of the solid content of dispersion 1. After stirring thoroughly for 10 minutes, the mixture was centrifuged to remove water and dried at 130℃ to 140℃ to obtain hydrotalcite-coated modified carbon nanotubes.

2. The polyolefin composition with PTC effect according to claim 1, characterized in that, The polyolefin resin is selected from one or more of polyethylene, polypropylene, poly-1-butene, and ethylene-vinyl acetate copolymer.

3. The polyolefin composition with PTC effect according to claim 2, characterized in that, The polyethylene is high-density polyethylene resin.

4. The polyolefin composition with PTC effect according to claim 3, characterized in that, The high-density polyethylene resin has a melt flow rate of 10.0 to 15.0 g / 10 min at 190°C and 21.6 kg.

5. The polyolefin composition with PTC effect according to claim 1, characterized in that, The carbon black is selected from acetylene black or pigment black.

6. The polyolefin composition with PTC effect according to claim 5, characterized in that, The acetylene carbon black has a particle size of 40-50 nm and an oil absorption value of 2.0-4.0 mL / g.

7. The polyolefin composition with PTC effect according to claim 1, characterized in that, The toughening agent is selected from one or more of POE resin, EVA resin and PU resin.

8. The polyolefin composition with PTC effect according to claim 7, characterized in that, The Shore A hardness of the POE resin is 52-60.

9. The polyolefin composition with PTC effect according to claim 1, characterized in that, The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid].

10. The polyolefin composition with PTC effect according to claim 1, characterized in that, The processing aid is a fluorine-containing aid.

11. A method for preparing a polyolefin composition with a PTC effect, characterized in that, The process includes the following steps: mixing and molding the polyolefin composition with PTC effect as described in any one of claims 1-10 to obtain a special material for the polyolefin composition.

12. An article, characterized in that, The article comprises the polyolefin composition with PTC effect as described in any one of claims 1-10.

13. The article of claim 12, characterized in that, The products include heat tracing tape or heated flooring.