HDPE masterbatch with both high strength and high thermal conductivity, its preparation method and application

Abstract

This invention relates to a high-strength and high-thermal-conductivity HDPE masterbatch, its preparation method, and its application, belonging to the field of polymer material processing technology. The HDPE masterbatch includes HDPE raw material, a composite thermally conductive filler, and an optional antioxidant. Based on a total mass of 100 wt% of the HDPE masterbatch, the content of the HDPE raw material is 65-75 wt%, the content of the composite thermally conductive filler is 25-35 wt%, and the content of the antioxidant is 0-0.3 wt%. Based on a total mass of 100 wt% of the composite thermally conductive filler, carbon-based fillers account for 50-90 wt%, and HDPE-g-MAH accounts for 10-50 wt%. The composite thermally conductive filler of this invention uses carbon-based fillers and HDPE-g-MAH as raw materials. Before filling with HDPE, it is assisted by ball milling force field exfoliation, dispersion, and modification. By compounding it with HDPE raw material in a certain ratio, the thermal conductivity is improved while further balancing the mechanical strength after filling with HDPE, resulting in an HDPE masterbatch with both high strength and high thermal conductivity.

Description

Technical Field

[0001] This invention belongs to the field of polymer material processing technology, and specifically relates to an HDPE masterbatch with both high strength and high thermal conductivity, its preparation method and application. Background Technology

[0002] High-density polyethylene (HDPE) is a commonly used thermoplastic polymer, widely used in pipe manufacturing due to its excellent physical and chemical properties, such as chemical resistance, abrasion resistance, low-temperature toughness, and processing performance. However, with the increasing demands on material performance from modern industry and infrastructure construction, traditional HDPE pipes have shown certain limitations in some high-temperature, high-pressure applications and applications requiring rapid heat dissipation. These limitations are mainly reflected in the following two aspects:

[0003] (1) Insufficient thermal conductivity: HDPE, as a typical polymer material, has low thermal conductivity. In some applications that require effective heat dissipation or temperature control, conventional HDPE pipes are difficult to meet the requirements. For example, in long-distance hot water pipelines or high-heat-flow process pipelines, low thermal conductivity may lead to local overheating of the material, thereby affecting the life and safety of the pipe.

[0004] (2) Limited mechanical strength: Although HDPE has good toughness, its tensile strength and rigidity are low. Especially under high temperature or high pressure environments, traditional HDPE pipes are prone to deformation or failure. Therefore, in engineering applications, HDPE often needs to be reinforced to improve its load-bearing capacity and stability.

[0005] In recent years, improving the performance of HDPE by adding fillers to the matrix has become a common and effective technique. For example, high thermal conductivity materials such as carbon nanotubes (CNTs), graphene, boron nitride (BN), and carbon fibers have been widely used to improve the thermal conductivity of HDPE.

[0006] Chinese patent document CN118006022A discloses a thermally conductive polyethylene pipe and its preparation method. The composite filler is obtained by compounding 10-12 parts of thermally conductive filler with 3-5 parts of reinforcing filler. The thermally conductive filler is prepared by modifying and combining flake graphite with carbon nanotubes using 1-butyl-3-methylimidazolium hexafluorophosphate. The reinforcing filler is cross-linked polyvinyl alcohol-modified silicon carbide crystals. However, the filler modification in this method requires the use of hazardous substances such as concentrated sulfuric acid, concentrated phosphoric acid, ammonium chloroplatinate, and potassium permanganate. In actual production, the operation is cumbersome, posing significant safety hazards and environmental pollution problems, making it difficult to achieve industrial-scale production.

[0007] Chinese patent document CN111320801A discloses a cross-linked polyethylene thermal conductive pipe and its preparation method. The polyethylene thermal conductive pipe comprises the following components: high-density polyethylene, carbon fiber, micron-sized carbon spheres, and polyethylene wax. However, the synergistic thermal conductivity between carbon fiber and micron-sized carbon spheres is not ideal. As shown in the examples, the material prepared from 10 parts by weight of carbon fiber (15 μm in diameter and 2 mm in length) and 10 parts by weight of carbon spheres (10 μm in diameter) has a thermal conductivity of only 0.6 W / m·K, which severely limits its heat dissipation performance during use.

[0008] Chinese patent document CN113736164A discloses a graphene-PE thermally conductive composite material, its preparation method, and its application. The PE thermally conductive composite material comprises 0.5–2 parts graphene, 87–92.5 parts high-density polyethylene, 3–5 parts grafting agent, 3–5 parts toughening agent, 0.3–0.6 parts antioxidant, and 0.3–0.6 parts lubricant. As can be seen from the examples, the thermal conductivity of the PE thermally conductive composite material is between 0.52 and 0.63 W / m·K, and the tensile strength is between 21 and 24 MPa. These performance characteristics are slightly insufficient and cannot meet the requirements for high-end thermally conductive pipes.

[0009] Achieving high thermal conductivity often requires the addition of a large amount of filler, but excessive filler can significantly reduce the mechanical strength of the material. Therefore, how to introduce functional fillers into the HDPE matrix to improve thermal conductivity while further balancing the material's mechanical strength has become an important research direction in the current technological field. Accordingly, developing an HDPE pipe masterbatch with both high strength and high thermal conductivity, and its preparation method, to meet the demands of modern industry for higher-performance composite materials, has significant practical application value and market potential. Summary of the Invention

[0010] To address the technical problems existing in the prior art, this invention provides an HDPE masterbatch, its preparation method, and its application. The raw materials for the composite thermally conductive filler of this invention are carbon-based fillers and HDPE-g-MAH. Before filling with HDPE, the filler is assisted by ball milling for exfoliation, dispersion, and modification. Then, it is compounded with HDPE raw materials in a certain ratio. This achieves improved thermal conductivity while further balancing mechanical strength after filling with HDPE, resulting in an HDPE masterbatch with both high strength and high thermal conductivity.

[0011] The first aspect of the present invention is to provide an HDPE masterbatch comprising HDPE raw material, composite thermally conductive filler and optional antioxidant;

[0012] Based on a total mass of 100wt% of the HDPE masterbatch, the content of the HDPE raw material is 65-75wt%, the content of the composite thermally conductive filler is 25-35wt%, and the content of the antioxidant is 0-0.3wt%.

[0013] The preparation method of the composite thermally conductive filler includes: ball milling raw materials including carbon-based fillers and HDPE-g-MAH to obtain the composite thermally conductive filler; based on the total mass of the composite thermally conductive filler of 100wt%, the carbon-based filler accounts for 50-90wt%, and the HDPE-g-MAH accounts for 10-50wt%.

[0014] This invention uses ball-milled carbon filler and HDPE-g-MAH polymer to obtain a composite thermally conductive filler, which is then compounded with HDPE raw materials in a specific ratio to obtain an HDPE masterbatch with both high mechanical properties and good thermal conductivity, achieving unexpected technical results.

[0015] This invention utilizes a continuous ball milling force field to induce a mechanochemical reaction between carbon-based fillers and HDPE-g-MAH during the ball milling process. This causes the carbon-based fillers to break down, peel off, modify, and disperse uniformly. The resulting composite thermally conductive filler is then compounded with HDPE raw materials in a specific ratio to obtain an HDPE masterbatch that combines high mechanical properties with good thermal conductivity, achieving unexpected technical results.

[0016] According to some preferred embodiments of the present invention, based on a total mass of 100wt% of the composite thermally conductive filler, carbon-based filler accounts for 65-75wt% and HDPE-g-MAH accounts for 25-35wt%.

[0017] According to some preferred embodiments of the present invention, based on 100wt% of the total mass of the HDPE masterbatch, the content of the composite thermally conductive filler is 25-35wt%, the content of the antioxidant is 0.1-0.3wt%, and preferably the balance is HDPE raw material; preferably,

[0018] Based on a total mass of 100wt% of the HDPE masterbatch, the content of the composite thermally conductive filler is 25-30wt%, the content of the antioxidant is 0.1-0.3wt%, and preferably the balance is HDPE raw material.

[0019] According to some preferred embodiments of the present invention, in the preparation method of the composite thermally conductive filler, the ball milling conditions include: the ratio of the mass of the grinding media in the ball mill to the total mass of all composite thermally conductive filler raw materials is (10-30):1, preferably (15-20):1.

[0020] According to some preferred embodiments of the present invention, in the preparation method of the composite thermally conductive filler, the ball milling time is 0.5 to 12 hours, preferably 3 to 10 hours.

[0021] According to some preferred embodiments of the present invention, in the preparation method of the composite thermally conductive filler, the ball milling speed is 200-600 rpm, preferably 300-500 rpm.

[0022] According to some preferred embodiments of the present invention, the carbon-based filler is selected from at least one of carbon fiber, carbon nanotube fiber, carbon nanotube, carboxylated carbon nanotube, natural graphite, graphene nanosheet, graphene, carbon black, and carbon sphere; preferably, the carbon-based filler is selected from one or more of natural graphite, carboxylated carbon nanotube, and carbon black.

[0023] While pursuing high strength, it is also crucial to achieve superior thermal conductivity. More suitable carbon-based fillers are selected from natural graphite, carboxylated carbon nanotubes, and carbon black. Preferably, the mass ratio of natural graphite, carboxylated carbon nanotubes, and carbon black is 1:(0.05-0.06):(0.05-0.06). This utilizes carbon-based fillers of different dimensions. Carbon-based fillers themselves possess extremely high intrinsic thermal conductivity, and the different dimensions of fillers easily overlap to form a three-dimensional point-line-plane thermal conductivity network, effectively improving thermal conductivity. Therefore, the combined use of carbon-based fillers of different dimensions can yield a masterbatch with higher thermal conductivity and balanced mechanical properties.

[0024] In pursuit of superior overall performance, natural graphite is a more preferred carbon-based filler.

[0025] According to some preferred embodiments of the present invention, the melt index of the HDPE-g-MAH (maleic anhydride-grafted high-density polyethylene) at 190°C and 2.16 kg is 0.3 to 0.6 g / 10 min; and / or the grafting rate of MAH (maleic anhydride) is 0.5% to 1.5%, based on an HDPE content of 100 wt%.

[0026] According to some preferred embodiments of the present invention, in the preparation method of the composite thermally conductive filler: the average particle size of the HDPE-g-MAH used for ball milling is 50-400 μm, preferably 100-300 μm; preferably, the HDPE-g-MAH used for ball milling is obtained by low-temperature pulverization of initial HDPE-g-MAH raw material, more preferably by ultra-low temperature cryogenic pulverization, and even more preferably by ultra-low temperature cryogenic pulverization in a machine equipped with liquid nitrogen freezing, wherein liquid nitrogen is continuously introduced during the pulverization process to achieve ultra-low temperature.

[0027] According to the present invention, the initial HDPE-g-MAH raw material is obtained by purchasing commercially available materials. As mentioned above, preferably, the initial HDPE-g-MAH raw material has the following characteristics: a melt index of 0.3 to 0.6 g / 10 min at 190°C and 2.16 kg; and / or, a MAH grafting rate of 0.5 wt% to 1.5 wt%, based on an HDPE content of 100 wt%.

[0028] The method for preparing the composite thermally conductive filler of the present invention includes:

[0029] The initial HDPE-g-MAH raw material is subjected to cryogenic pulverization treatment (in a machine equipped with liquid nitrogen freezing). After pulverization, the particle size range of HDPE-g-MAH for ball milling raw material is 50 to 400 μm, preferably 100 to 300 μm.

[0030] The raw materials, including HDPE-g-MAH, containing carbon-based fillers and ball milling raw materials, are ball-milled under a continuous ball milling force field to achieve peeling, dispersion, and modification. This ball milling method is also applicable to large-scale ball milling equipment used in industrial production. This composite thermally conductive filler features a simple process, high efficiency, low cost, and energy saving and environmental friendliness. The continuous ball milling force field in this invention facilitates continuous production and is suitable for large-scale industrial preparation of carbon-based thermally conductive fillers.

[0031] According to some preferred embodiments of the present invention, the HDPE raw material has a melt index of 0.20–0.5 g / 10 min at 190°C and 2.16 kg, and / or a density of 0.94–0.96 g / cm³. 3 .

[0032] According to some preferred embodiments of the present invention, the HDPE masterbatch has the following characteristics:

[0033] According to GB / T 1040.2-2022, the tensile strength of the HDPE masterbatch is above 26.9 MPa; and / or,

[0034] The transient heat source method was used to test the thermal conductivity of a circular HDPE masterbatch with a diameter of 30 mm and a thickness of 0.4 mm, which was above 2.3 W / m·k. Preferably, the transient planar heat source method in this invention was tested using a thermal conductivity meter (model and source: hot-disk, 2500-OT, Sweden).

[0035] A second aspect of the present invention is to provide a method for preparing the HDPE masterbatch described above, comprising:

[0036] The composite thermally conductive filler, HDPE raw material, and optional antioxidant are mechanically blended to obtain a premix. The premix is ​​then melt-extruded and granulated to obtain the HDPE masterbatch.

[0037] According to some preferred embodiments of the present invention, the melt extrusion is carried out in a twin-screw extruder; preferably,

[0038] The operating conditions of the twin-screw extruder include: a feeding section temperature of 160–190°C, a conveying section temperature of 200–230°C, a melting section temperature of 220–240°C, and a homogenization section temperature of 220–240°C.

[0039] According to the present invention, mechanical blending is a prior art and a conventional technique in the field of plastics preparation, and will not be described in detail here.

[0040] According to the present invention, the extrusion rate of the twin-screw extruder can also be selected within a wide range, and those skilled in the art can make conventional adjustments, which will not be elaborated here.

[0041] More preferably, the method for preparing the HDPE masterbatch of the present invention specifically includes the following steps:

[0042] (1) The HDPE-g-MAH raw material for ball milling and the carbon-based filler are mechanically ball-milled in a certain proportion to obtain a composite thermally conductive filler;

[0043] (2) The composite thermally conductive filler, HDPE and optional antioxidant obtained in step (1) are mechanically blended to obtain a premix. The premix is ​​then added to a twin-screw extruder and extruded and granulated to obtain the HDPE masterbatch.

[0044] The third aspect of the present invention is the application of the HDPE masterbatch described above or the HDPE masterbatch obtained by the preparation method described above in the preparation of pipes.

[0045] The HDPE masterbatch prepared by this invention can be diluted in different proportions according to the usage requirements to obtain a composition, thereby enabling the control of pipe performance.

[0046] Compared with the prior art, the present invention has the following advantages:

[0047] As mentioned above, this invention uses ball-milled carbon filler and HDPE-g-MAH polymer to obtain a composite thermally conductive filler, which is then compounded with HDPE raw materials in a specific ratio to obtain HDPE masterbatch. The thermal conductivity of the sample made of HDPE masterbatch of this invention is tested using the transient heat source method, and the tensile strength of the sample made of HDPE masterbatch of this invention is tested using GB / T1040.2-2022. It can be seen that the tensile strength of HDPE masterbatch of this invention is above 26.9 MPa, and the thermal conductivity tested by the transient heat source method is above 2.37 W / m·K, which has the characteristics of both high strength and high thermal conductivity.

[0048] The inventors of this invention believe that the reason for the above advantages is that the raw materials of the composite thermally conductive filler of this invention are carbon-based fillers and HDPE-g-MAH. Before filling HDPE, the filler is assisted by ball milling force field peeling, dispersion and modification, and then compounded with HDPE raw materials in a certain ratio. This achieves the improvement of thermal conductivity after filling HDPE while further balancing mechanical strength, resulting in HDPE masterbatch with both high strength and high thermal conductivity.

[0049] This invention utilizes the mechanical force of ball milling to achieve efficient miniaturization, exfoliation, and uniform dispersion of carbon-based fillers. During ball milling, oxygen in the air, under the mechanochemical action of the milling process, introduces more oxygen-containing functional groups to the surface of the carbon-based fillers, thus modifying their surface. This significantly improves the interfacial interaction between the carbon-based fillers and the polymer, which is beneficial for balancing the mechanical properties of the composite material. Furthermore, the HDPE-g-MAH used in this method is a solid polymer powder, and the ball milling process does not generate waste solvents, therefore this technology can be used for continuous and large-scale production. Detailed Implementation

[0050] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0051] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0052] 1. Detection Method

[0053] The testing instruments and conditions used in this embodiment are as follows:

[0054] Thermal conductivity testing: The thermal conductivity of the composite material was characterized using the transient heat source method (hot-disk thermal conductivity meter, 2500-OT, Sweden). The test specimens were circular samples with a diameter of 30 mm and a thickness of 0.4 mm.

[0055] Mechanical property testing: The tensile strength mechanical properties of the composite material were tested using a universal testing machine (CMT4104, MTS Systems, China) according to GB / T 1040.2-2022 as the testing standard. Five 5A type specimens were required for the test, and the average value was taken after the test.

[0056] 2. Raw materials

[0057] In the following examples and comparative examples, the HDPE used was PN049-030-122RTⅡ, sourced from Tianjin Petrochemical, with a melt flow index of 0.3 g / 10 min (190℃; 2.16 kg) and a density of 0.95 g / cm³. 3 ;

[0058] HDPE-g-MAH raw material, purchased from LyondellBasell, has a melt index of 0.3 g / 10 min at 190°C and 2.16 kg, and a MAH grafting rate of 1.2 wt%, based on an HDPE content of 100 wt%.

[0059] The ultra-high molecular weight polyethylene (UHMWPE) is UPE050, purchased from Nanjing Tengyi New Material Technology Co., Ltd., with a particle size of approximately 50 μm and a number-average molecular weight range of 2 million to 8 million.

[0060] The maleic anhydride-grafted styrene-butadiene-styrene block copolymer (SEBS-g-MAH) was 9901, purchased from Lee Chang Yung Chemical Co., Ltd., with a styrene-derived structural unit content of 30 wt% and a SEBS-g-MAH content of 100 wt%.

[0061] The particle size range of natural graphite is 10–15 μm.

[0062] Carboxylated carbon nanotubes have a length of 10–30 μm and a diameter of 50–15 nm.

[0063] The average particle size of carbon black is approximately 24 nm.

[0064] Example 1

[0065] This embodiment provides a composite thermally conductive filler, comprising the following components by mass percentage:

[0066] 70% natural graphite

[0067] HDPE-g-MAH 30%

[0068] Specifically, the preparation methods of composite thermally conductive fillers include:

[0069] HDPE-g-MAH raw material was subjected to cryogenic pulverization treatment (in a machine equipped with liquid nitrogen freezing) to obtain HDPE-g-MAH after pulverization. The average particle size of the pulverized HDPE-g-MAH was about 200 μm.

[0070] The mixture of pulverized HDPE-g-MAH and natural graphite in the above mass percentage ratio was used as the ball milling raw material. The ball milling was carried out at 300 rpm for 1.5 h with a ball-to-material mass ratio of 15:1. The mixture was then removed to obtain the composite thermally conductive filler.

[0071] Using the above-mentioned composite thermally conductive filler, this embodiment provides a masterbatch for HDPE pipes that combines high strength and high thermal conductivity, comprising the following raw material components by mass percentage:

[0072] HDPE 71.33%

[0073] Composite thermally conductive filler 28.57%

[0074] Antioxidant 0.1%

[0075] The above raw materials are mechanically blended to obtain a premix, which is then added to a twin-screw extruder. The specific extrusion conditions are: the temperature of the feeding section is 170°C, the temperature of the conveying section is 220°C, the temperature of the melting section is 225°C, and the temperature of the homogenization section is 230°C. The material is then extruded and granulated to obtain the HDPE pipe masterbatch.

[0076] The HDPE pipe masterbatch was hot-pressed into shape using a hot press. The molded sample was cut into 30mm diameter round pieces and 5A type tensile specimens for thermal conductivity and mechanical property testing. The results are shown in Table 1.

[0077] Example 2

[0078] Composite thermally conductive filler and HDPE pipe masterbatch with both high strength and high thermal conductivity were prepared according to the method of Example 1. The difference was that in the preparation method of composite thermally conductive filler, the ball milling time was changed to 3.0 h, while the rest was the same as in Example 1.

[0079] Example 3

[0080] Composite thermally conductive filler and HDPE pipe masterbatch with both high strength and high thermal conductivity were prepared according to the method of Example 1. The difference was that in the preparation method of composite thermally conductive filler, the ball milling time was changed to 4.5h, while the rest was the same as in Example 1.

[0081] Example 4

[0082] Composite thermally conductive filler and HDPE pipe masterbatch with both high strength and high thermal conductivity were prepared according to the method of Example 1. The difference was that in the preparation method of composite thermally conductive filler, the ball milling time was changed to 6.0 h, while the rest was the same as in Example 1.

[0083] Example 5

[0084] The composite thermally conductive filler and the HDPE pipe masterbatch with both high strength and high thermal conductivity were prepared according to the method of Example 2. The difference is that the composite thermally conductive filler includes the following components in the following mass percentages, while the others are the same as in Example 2.

[0085] 66.50% natural graphite

[0086] Carboxylated carbon nanotubes 3.50%

[0087] HDPE-g-MAH 30%

[0088] Example 6

[0089] The composite thermally conductive filler and the HDPE pipe masterbatch with both high strength and high thermal conductivity were prepared according to the method of Example 2. The difference is that the composite thermally conductive filler includes the following components in the following mass percentages, while the others are the same as in Example 2.

[0090]

[0091] Example 7

[0092] The composite thermally conductive filler and the HDPE pipe masterbatch with both high strength and high thermal conductivity were prepared according to the method of Example 2. The difference is that the HDPE pipe masterbatch with both high strength and high thermal conductivity includes the following components in mass percentage:

[0093] HDPE 67.9%

[0094] Composite thermally conductive filler 32.0%

[0095] Antioxidant 0.1%

[0096] Other conditions are the same as in Example 1.

[0097] Comparative Example 1

[0098] This comparative example uses only HDPE without any fillers.

[0099] Comparative Example 2

[0100] The preparation was carried out according to Example 1, except that the ball milling time of the composite thermally conductive filler was 0h, that is, no ball milling was performed, and the mixture obtained by directly mixing the pulverized HDPE-g-MAH and natural graphite was used as the thermally conductive filler.

[0101] Comparative Example 3

[0102] The composite thermally conductive filler and HDPE pipe masterbatch were prepared according to the method of Example 2, except that HDPE-g-MAH was replaced with ultra-high molecular weight polyethylene (UHMWPE), otherwise it was the same as Example 2.

[0103] Comparative Example 4

[0104] The composite thermally conductive filler and HDPE pipe masterbatch were prepared according to the method of Example 2, except that HDPE-g-MAH was replaced with maleic anhydride-grafted styrene-butadiene-styrene block copolymer (SEBS-g-MAH), otherwise the same as in Example 2.

[0105] Comparative Example 5

[0106] All the raw materials in Example 2 were ball-milled together, and the ball-milled material was then extruded and granulated to obtain HDPE pipe masterbatch.

[0107] Comparative Example 6

[0108] First, prepare the composite thermally conductive filler:

[0109] Composite thermally conductive filler comprises the following components in weight percentage:

[0110] 70% natural graphite

[0111] HDPE-g-MAH 30%

[0112] Specifically, the preparation methods of composite thermally conductive fillers include:

[0113] HDPE-g-MAH raw material was subjected to cryogenic pulverization, and the average particle size of the HDPE-g-MAH obtained after pulverization was about 200μm.

[0114] The mixture of pulverized HDPE-g-MAH and natural graphite in the above mass percentage ratio was used as the ball milling raw material. The ball milling was carried out at 300 rpm for 3.0 h with a ball-to-material mass ratio of 15:1. The mixture was then removed to obtain the composite thermally conductive filler.

[0115] Further preparation of HDPE pipe masterbatch with both high strength and high thermal conductivity:

[0116] HDPE pipe masterbatch, which combines high strength and high thermal conductivity, includes the following raw material components by weight percentage:

[0117] HDPE-g-MAH 71.33%

[0118] Composite thermally conductive filler 28.57%

[0119] Antioxidant 0.1%

[0120] Comparative Example 7

[0121] The composite thermally conductive filler and the HDPE pipe masterbatch with both high strength and high thermal conductivity were prepared according to the method of Example 2. The difference is that the HDPE pipe masterbatch with both high strength and high thermal conductivity includes the following components in mass percentage:

[0122] HDPE 79.9%

[0123] Composite thermally conductive filler 20.0%

[0124] Antioxidant 0.1%

[0125] Other conditions are the same as in Example 2.

[0126] Table 1

[0127]

[0128]

[0129] The thermal conductivity of the samples in the examples and comparative examples was tested using the transient heat source method, and the tensile strength of the samples in the examples and comparative examples was tested using GB / T1040.2-2022. The results are shown in Table 1. As can be seen from Table 1, the tensile strength of the HDPE masterbatch of the present invention is above 26.9 MPa, and the thermal conductivity tested by the transient heat source method is above 2.37 W / m·K, exhibiting both high strength and high thermal conductivity. In contrast, the comparative examples that did not use the HDPE masterbatch of the present invention either had significantly lower thermal conductivity than the examples of the present invention, or significantly lower tensile strength than the HDPE masterbatch of the present invention, or both were lower than the HDPE masterbatch of the present invention. It is evident that the present invention has achieved unexpected technical effects.

[0130] In this invention, the thermal conductivity of HDPE masterbatch was measured using a thermal conductivity meter (hot-disk, 2500-OT, Sweden). The Hot Disk method is an improved transient planar heat source method with significant advantages such as rapid measurement, wide applicability, and high accuracy. During the test, the planar heat source (probe) directly contacts the sample, acting as both a heating element and a temperature sensor. The thermal conductivity is calculated by recording the sample's temperature rise curve and using a three-dimensional thermal diffusion model. Because the heat flow diffuses in three dimensions, the measurement area is large, comprehensively reflecting the overall thermal conductivity of the material, thus more accurately characterizing the material's true thermal conductivity. Existing technologies also use the laser flash method to detect thermal conductivity. The principle of the laser flash method is to heat one side of the sample with a laser pulse, record the temperature change curve of the other side over time, calculate the thermal diffusivity based on the thermal diffusion equation, and further calculate the thermal conductivity using the sample density and specific heat capacity. This method is based on a one-dimensional thermal diffusion model, assuming that the heat flow passes perpendicularly through the sample and neglecting lateral thermal conductivity. This assumption may lead to biased results, especially when testing materials with anisotropic properties, where the error is more significant and not comparable to the thermal conductivity of the hot-disk test in this invention. From the perspective of thermal conductivity alone, the HDPE masterbatch in this invention has a thermal conductivity more than three times higher than that of HDPE material without any fillers (Comparative Example 1), demonstrating the high thermal conductivity of the HDPE masterbatch in this invention.

[0131] More specifically:

[0132] Comparative Example 1 is HDPE material without any fillers, and its thermal conductivity is worse than that of the example, indicating that the addition of ball-milled thermally conductive composite filler has a significant impact on enhancing the thermal conductivity of HDPE.

[0133] Comparative Example 2 shows HDPE masterbatch with unmilled thermally conductive composite filler. Its thermal conductivity is lower than that of Example 2, indicating that ball milling and exfoliation of graphite is beneficial to enhancing the thermal conductivity of HDPE masterbatch. Its tensile strength is significantly lower than that of Example 2, indicating that the ball milling, exfoliation, dispersion, and modification of filler in this invention is beneficial to enhancing the interfacial interaction between the filler and the polymer matrix, thereby improving the mechanical properties of the composite material.

[0134] A comparison of Comparative Example 1 and Comparative Example 2 shows that simply adding fillers without ball milling, dispersing, and modification significantly reduces the mechanical properties of polymer composites. However, using the method of this invention, although fillers are also added, the mechanical properties of the HDPE masterbatch are significantly improved compared to Comparative Example 2, achieving unexpected technical results.

[0135] In Comparative Example 3, the ball milling aid HDPE-g-MAH was replaced with UHMWPE. The mechanical and thermal conductivity properties were lower than in Example 2, but the mechanical properties were better. This indicates that UHMWPE, as a ball milling aid, can improve the mechanical properties of HDPE pipe masterbatch, but it cannot effectively remove graphite to enhance the thermal conductivity of the masterbatch. In contrast, this invention uses HDPE-g-MAH ball-milled together with carbon-based fillers, adding it as a composite thermally conductive filler to the HDPE masterbatch, resulting in a significant improvement in thermal conductivity. This demonstrates that unexpected technical effects have been achieved.

[0136] In Comparative Example 4, the ball milling aid HDPE-g-MAH was replaced with SEBS-g-MAH. The mechanical and thermal conductivity properties were lower than those of Example 2 and Comparative Example 2, but the thermal conductivity was very close to that of Comparative Example 2. This indicates that SEBS-g-MAH, as a ball milling aid, can exfoliate graphite to a certain extent, but SEBS-g-MAH and HDPE are incompatible, thus leading to poorer mechanical properties. In this invention, HDPE-g-MAH is ball-milled together with carbon-based fillers and added to the HDPE masterbatch as a composite thermally conductive filler. The mechanical properties are significantly improved compared to SEBS-g-MAH, demonstrating an unexpected technical effect.

[0137] In Comparative Example 5, all raw materials from Example 2 were mixed and ball-milled, then directly granulated by twin-screw extrusion to prepare masterbatch. Compared to Example 2, the mechanical properties of this masterbatch decreased significantly, while the improvement in thermal conductivity was not obvious. Moreover, ball milling all raw materials together was uneconomical. In contrast, this invention ball-mills raw materials including carbon-based fillers and HDPE-g-MAH to obtain the composite thermally conductive filler, which is then used as part of the raw material for HDPE masterbatch. The resulting HDPE masterbatch possesses both high strength and high thermal conductivity, achieving unexpected technical effects.

[0138] In Comparative Example 6, after replacing the HDPE matrix material with HDPE-g-MAH, its mechanical and thermal conductivity properties were significantly lower than those of Example 2. This indicates that using only graphite and HDPE-g-MAH is insufficient to prepare a high-performance pipe masterbatch. This invention, using HDPE raw materials, composite thermally conductive fillers, and optional antioxidants, has yielded an HDPE masterbatch possessing both high strength and high thermal conductivity, achieving unexpected technical results.

[0139] In Comparative Example 7, after reducing the content of the composite thermally conductive filler to 20%, the overall performance of the masterbatch showed a significant decline compared to Example 2. This indicates that reducing the content of the composite thermally conductive filler weakens the overall performance of the masterbatch. However, under the specific ratio of HDPE raw material and composite thermally conductive filler in this invention—based on a total mass of 100wt% of the HDPE masterbatch, with the content of the HDPE raw material being 65-75wt%, the content of the composite thermally conductive filler being 25-35wt%, and the content of the antioxidant being 0-0.3wt%—an HDPE masterbatch possessing both high strength and high thermal conductivity was obtained, achieving unexpected technical effects.

[0140] As can be seen from the above analysis, the present invention uses ball milled carbon filler and HDPE-g-MAH polymer to obtain a composite thermally conductive filler that is compounded with HDPE raw material in a specific ratio, resulting in an HDPE masterbatch with both high mechanical properties and good thermal conductivity, achieving unexpected technical effects.

[0141] In Examples 1-4, the thermal conductivity of the HDPE masterbatch increases with the extension of ball milling time, indicating that the natural graphite was successfully exfoliated by the HDPE-g-MAH powder during ball milling. Therefore, the preferred ball milling time is 3-10 hours, and more preferably 4-10 hours.

[0142] In Example 5, after replacing a certain amount of graphite with carbon nanotubes, its thermal conductivity was slightly lower than that of Example 2, indicating that the addition of a small amount of carbon nanotubes had little impact on the thermal conductivity of the HDPE pipe masterbatch. Its tensile strength was lower than that of Example 2, indicating that the addition of carbon nanotubes introduced more heterogeneous interfaces, which would affect the mechanical properties of the HDPE pipe masterbatch. However, using the preferred embodiment of this invention, where the carbon-based filler is selected from natural graphite, further achieves superior technical effects under the same conditions compared to using carbon nanotubes.

[0143] In Example 6, after replacing a certain amount of graphite with carboxylated carbon nanotubes and carbon black, its thermal conductivity was slightly higher than that of Example 2. This indicates that the addition of carboxylated carbon nanotubes and carbon black formed a three-dimensional thermally conductive network structure in HDPE, consisting of points (carbon black), lines (carbon nanotubes), and surfaces (exfoliated graphite). This is beneficial for improving the thermal conductivity of the HDPE pipe masterbatch. Its tensile strength was lower than that of Example 2, indicating that carbon black and carboxylated carbon nanotubes introduced more heterogeneous interfaces, thus affecting the mechanical properties of the HDPE pipe masterbatch. Therefore, while pursuing high strength, higher thermal conductivity is also desirable, and a more preferred carbon-based filler is natural graphite, carboxylated carbon nanotubes, and carbon black. Furthermore, for the pursuit of superior overall performance, natural graphite is an even more preferred carbon-based filler.

[0144] In Example 7, after increasing the content of the composite thermally conductive filler to 32 wt%, the thermal conductivity of the masterbatch was significantly improved compared to Example 2, while the mechanical properties decreased slightly. Therefore, to achieve a comprehensive balance between mechanical and thermal conductivity, it is more preferable to add 25 wt% to 30 wt% of the ball-milled composite thermally conductive filler.

[0145] As can be seen from the analysis of the above preferred embodiments, the present invention can achieve even better technical effects through further optimization, such as further screening of carbon-based fillers and further optimization of HDPE masterbatch raw material formulation.

[0146] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0147] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

[0148] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0149] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0150] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0151] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

[0152] Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or technical ideas shall be regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art believe that the combination is obviously unreasonable.

Claims

1. An HDPE masterbatch, comprising HDPE raw material, composite thermally conductive filler and optional antioxidant; Based on a total mass of 100wt% of the HDPE masterbatch, the content of the HDPE raw material is 65-75wt%, the content of the composite thermally conductive filler is 25-35wt%, and the content of the antioxidant is 0-0.3wt%. in, The preparation method of the composite thermally conductive filler includes: ball milling raw materials including carbon-based fillers and HDPE-g-MAH to obtain the composite thermally conductive filler, wherein the carbon-based filler accounts for 50-90 wt% and the HDPE-g-MAH accounts for 10-50 wt% based on the total mass of the composite thermally conductive filler of 100 wt%.

2. The HDPE masterbatch according to claim 1, characterized in that: Based on a total mass of 100 wt% for the composite thermally conductive filler, carbon-based fillers account for 65–75 wt%, HDPE-g-MAH accounts for 25–35 wt%; and / or, Based on a total HDPE masterbatch mass of 100 wt%, the content of the composite thermally conductive filler is 25-35 wt%, and the content of the antioxidant is 0.1-0.3 wt%; preferably, Based on a total mass of 100wt% of the HDPE masterbatch, the content of the composite thermally conductive filler is 25-30wt%, and the content of the antioxidant is 0.1-0.3wt%.

3. The HDPE masterbatch according to claim 1, characterized in that: In the preparation method of the composite thermally conductive filler, the ball milling conditions include: In the ball mill, the ratio of the mass of the grinding media to the total mass of all composite thermally conductive filler raw materials is (10–30):1, preferably (15–20):1; and / or, The ball milling time is 0.5–12 hours, preferably 3–10 hours; and / or, The ball mill speed is 200-600 rpm, preferably 300-500 rpm.

4. The HDPE masterbatch according to claim 1, characterized in that: The carbon-based filler is selected from at least one of carbon fiber, carbon nanotube fiber, carbon nanotube, carboxylated carbon nanotube, natural graphite, graphene nanosheets, graphene, carbon black, and carbon spheres; preferably, The carbon-based filler is selected from one or more of natural graphite, carboxylated carbon nanotubes, and carbon black; more preferably, The carbon-based filler is selected from natural graphite, or the carbon-based filler is selected from natural graphite, carboxylated carbon nanotubes and carbon black, preferably with a mass ratio of natural graphite, carboxylated carbon nanotubes and carbon black of 1:(0.05-0.06):(0.05-0.06).

5. The HDPE masterbatch according to claim 1, characterized in that: The melt index of the HDPE-g-MAH at 190℃ and 2.16kg is 0.3–0.6 g / 10min; and / or, the grafting rate of MAH is 0.5 wt%–1.5 wt%, based on an HDPE content of 100 wt%; and / or, In the preparation method of the composite thermally conductive filler: The average particle size of the HDPE-g-MAH used for ball milling is 50-400 μm, preferably 100-300 μm; preferably, the HDPE-g-MAH used for ball milling is obtained by low-temperature pulverization of initial HDPE-g-MAH raw material; more preferably, it is subjected to ultra-low temperature cryogenic pulverization treatment.

6. The HDPE masterbatch according to claim 1, characterized in that: The HDPE raw material has a melt flow index of 0.20–0.5 g / 10 min at 190°C and 2.16 kg, and / or a density of 0.94–0.96 g / cm³. 3 .

7. The HDPE masterbatch according to any one of claims 1 to 6, characterized in that: According to GB / T 1040.2-2022, the tensile strength of the HDPE masterbatch is above 26.9 MPa; and / or, The thermal conductivity of a circular HDPE masterbatch with a diameter of 30 mm and a thickness of 0.4 mm was found to be above 2.3 W / m·K using the transient heat source method.

8. A method for preparing HDPE masterbatch according to any one of claims 1 to 7, comprising: The composite thermally conductive filler, HDPE raw material, and optional antioxidant are mechanically blended to obtain a premix. The premix is ​​then melt-extruded and granulated to obtain the HDPE masterbatch.

9. The preparation method according to claim 8, characterized in that: The melt extrusion is carried out in a twin-screw extruder; preferably, it is performed in a twin-screw extruder. The operating conditions of the twin-screw extruder include: a feeding section temperature of 160–190°C, a conveying section temperature of 200–230°C, a melting section temperature of 220–240°C, and a homogenization section temperature of 220–240°C.

10. The application of an HDPE masterbatch according to any one of claims 1 to 7 or an HDPE masterbatch obtained by the preparation method according to claim 8 or 9 in the preparation of pipes.

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