A special color masterbatch for PE heat-resistant pipes and fittings and its preparation method

Abstract

This invention discloses a special color masterbatch for PE heat-resistant pipes and fittings and its preparation method, belonging to the field of color masterbatch technology. The color masterbatch, by weight, consists of 40-65 parts carrier resin, 8-25 parts opacifier, 1.5-2.5 parts modified composite pigment, and 0-2 parts functional additives. First, the functional material is reacted with a silane compound in an alkaline ethanol solution to form a coating solution. Then, the composite pigment is subjected to ultrasonic-assisted mechanical stirring, followed by drying and ball milling to obtain the modified composite pigment. Finally, the pigment is mixed with the carrier resin, opacifier, antioxidant, light stabilizer, etc., in stages, and then melt-extruded and granulated to obtain the finished product. Compared with the prior art, this invention significantly improves the pigment's dispersibility, interfacial bonding strength, and weather resistance and abrasion resistance. The resulting color masterbatch has uniform coloring and excellent stability, making it particularly suitable for high-performance PE heat-resistant pipes and fittings.

Description

Technical Field

[0001] This invention relates to the field of color masterbatch technology, and in particular to a color masterbatch for PE heat-resistant pipes and fittings and its preparation method. Background Technology

[0002] As an indispensable coloring and functional masterbatch in the modern plastics industry, the performance of color masterbatch directly determines the appearance quality, performance, and service life of the final plastic products. Especially in the field of polyethylene high-temperature resistant pipes and fittings, the requirements for specialized color masterbatches are far higher than those for general-purpose products. These pipes serve in complex environments such as underground and outdoors for extended periods, needing to withstand not only mechanical stresses such as internal pressure and external impacts, but also long-term thermo-oxidative aging, ultraviolet radiation, diurnal temperature cycles, and the continuous action of fluids within the pipe. Therefore, an ideal specialized color masterbatch must achieve a balance of multiple technical objectives: ensuring ultrafine and stable dispersion of pigments in the polymer matrix to present uniform and vibrant colors; imparting excellent weather resistance to resist color fading; possessing excellent wear resistance to maintain surface integrity; and maintaining long-term physicochemical stability under high-temperature processing and use conditions. However, traditional masterbatches suffer from poor compatibility between pigments and resin matrices, which can easily lead to pigment particle aggregation and migration. This not only causes a decrease in coloring power and uneven color, but also becomes a stress concentration point, accelerating the environmental aging and failure of the material. This has become a key technical bottleneck restricting the development of high-performance PE pipes.

[0003] To overcome the aforementioned bottlenecks, existing technologies have undergone numerous explorations, but limitations and applicability boundaries still exist. For example, Chinese Patent Publication No. CN119708906A discloses a toluidine red pigment for architectural coatings, which significantly improves weather resistance and dispersibility in coating systems by introducing nano-oxides and organosilicon modifiers. However, this technical solution targets the coating film-forming system, and its pigment carrier, application interface, and performance evaluation standards are fundamentally different from those of masterbatches that need to be melt-dispersed in PE resin and subjected to high-temperature shearing processing. Its technical effects are difficult to directly transfer to the field of plastic coloring. Chinese Patent Publication No. CN119955326A provides a method for preparing an acid and alkali resistant permanent red pigment, which enhances the chemical stability of the pigment through silica coating and hydrophobic treatment with fluorinated silanes. However, its technical focus is on improving the pigment's resistance to acid and alkali corrosion. For key mechanical properties and long-term durability indicators, such as wear resistance, UV aging resistance, and interfacial bonding with macromolecular polyolefins, which are particularly critical for PE pipes, this patent does not provide effective solutions. In addition, Chinese patent publication number CN120137221A relates to a high-performance color masterbatch for automotive engineering plastics, which uses polypropylene as the main carrier and emphasizes mechanical and UV resistance properties. However, polypropylene and polyethylene have very different molecular structures, crystallization behaviors and processing rheological properties. The color masterbatch formulation and process conditions using polypropylene as the carrier cannot be directly applied to PE pressure piping systems that have strict requirements for environmental stress cracking resistance. Furthermore, this solution does not adequately consider the long-term thermal stability required for the pipe material.

[0004] Current technology reveals a lack of a dedicated integrated masterbatch solution for the specific applications of PE high-temperature resistant pipes and fittings. The core challenge lies in the fact that existing solutions primarily address single issues, such as dispersibility or chemical resistance, or are limited to specific application systems, such as coatings or certain engineering plastics. They fail to address the systemic design and innovation from multiple dimensions, including the inherent compatibility of the pigment-resin interface, the synergistic effect of functional components, and resistance to complex service environments. Therefore, the industry urgently needs an innovative technological approach that can simultaneously overcome the challenges of long-term stable pigment dispersion in the PE matrix, enhanced interfacial bonding, and synergistic improvement of macroscopic wear resistance, weather resistance, and heat resistance. This would allow for the development of dedicated masterbatch products with superior overall performance that meet the long-life requirements of high-end PE pipes and fittings. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a special color masterbatch for PE heat-resistant pipes and fittings that significantly improves wear resistance and weather resistance through synergistic compounding of functional materials and multi-scale reinforced structural design, as well as its preparation method.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A color masterbatch for PE heat-resistant pipes and fittings comprises the following components in parts by weight: 40-65 parts carrier resin, 8-25 parts opacifier, 1.5-2.5 parts modified composite pigment, and 0-2 parts functional additives.

[0007] The carrier resin is composed of high-density polyethylene and linear low-density polyethylene in a mass ratio of 3-4:1-2.

[0008] The light-blocking agent is titanium dioxide.

[0009] The functional additive is at least one of antioxidants, light stabilizers, and high-efficiency dispersants.

[0010] Preferably, the functional additives are composed of antioxidants, light stabilizers, and high-efficiency dispersants in a mass ratio of 0.4-0.8:0.1-0.3:0.3-0.8.

[0011] The antioxidant is at least one of antioxidant 1010, antioxidant 168 and antioxidant 1076.

[0012] The light stabilizer is one or more of the following: (2,2,6,6-tetramethyl-4-hydroxypiperidine) benzoate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2,6-di-tert-butyl-p-cresol, propyl gallate, 6-tert-butyl-m-cresol, 6-tert-butyl-2,4-dimethylphenol, and 2,6-di-tert-butyl-4-methylphenol.

[0013] The high-efficiency dispersant is at least one of zinc stearate, fatty acid amide, and polyethylene wax.

[0014] The preparation method of the modified composite pigment is as follows: S1. The functional material is added to anhydrous ethanol and ultrasonically treated to obtain a dispersion; the silane compound is added to an ethanol aqueous solution, the pH of the system is adjusted with ammonia, and then mixed with the dispersion, heated and stirred to obtain a modified coating solution. S2. Add the composite pigment to the modified coating solution prepared in step S1, and perform mechanical stirring under ultrasonic assistance. After centrifugation, drying, ball milling and sieving, the modified composite pigment is obtained.

[0015] Preferably, the modified composite pigment is prepared by the following method, in parts by weight: S1. Add 0.2-0.35 parts of functional material to 20-40 parts of anhydrous ethanol, and treat with ultrasound at 100-300W for 10-30 minutes to obtain a dispersion; then, add 0.1-0.2 parts of silane compound to 10-30 parts of 70-80wt% ethanol aqueous solution, adjust the pH of the system to 7.5-9 with 20-27wt% ammonia water, and then mix with the aforementioned dispersion; stir continuously at 50-70℃ for 1-3 hours to obtain a modified coating solution; S2. Add 2-3.5 parts of composite pigment to the modified coating solution prepared in step S1, and treat it for 1-3 hours under ultrasonic-assisted mechanical stirring at 100-300W. After centrifugation and vacuum drying at 40-60℃ for 5-20 hours, the product is ball-milled and passed through a 200-300 mesh sieve to obtain the modified composite pigment.

[0016] The composite pigment is composed of titanium yellow, ultramarine blue, iron oxide, and carbon black in a mass ratio of 1-1.5:0.5-1:0.05-0.1:0.03-0.1.

[0017] The functional material is at least one of titanium dioxide, nano zinc oxide, nano cerium dioxide, nano silicon dioxide, nano aluminum oxide, nano zirconium oxide, nano indium tin oxide, nano hydroxyapatite, and calcium sulfate whiskers.

[0018] Preferably, the functional material is composed of nano-hydroxyapatite and nano-cerium dioxide in a mass ratio of 4-6:1-3.

[0019] More preferably, the functional material is composed of nano-hydroxyapatite, nano-cerium dioxide and calcium sulfate whiskers in a mass ratio of 4-6:1-3:0.5-2.

[0020] The silane compound is at least one of methyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, tetramethoxysilane, octyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, trifluoropropyltrimethoxysilane, and tridecafluorooctyltrimethoxysilane.

[0021] Preferably, the silane compound is a combination of methyltrimethoxysilane and tridecafluorooctyltrimethoxysilane in a mass ratio of 3-5:0.5-2.

[0022] The preparation method of the special color masterbatch for PE heat-resistant pipes and fittings is as follows: Modified composite pigments and high-efficiency dispersants are premixed in a high-speed mixer at room temperature for 5-10 minutes to prepare a uniform pigment concentrate. Next, a segmented hot-mixing kneading process is performed, where the carrier resin and opacifier are placed in a mixer and mixed at 80-95°C for 3-10 minutes. The material is then cooled to 50-60°C, and the aforementioned pigment concentrate, antioxidant, and light stabilizer are added. Mixing continues at 50-60°C for another 3-10 minutes to obtain a uniformly mixed material. Finally, melt extrusion granulation is performed: the resulting material... The material is melt-extruded through a parallel co-rotating twin-screw extruder. The extruder feed port temperature is controlled to be below 150℃, the temperatures of zones 1 to 9 of the extruder body are each independently 150-210℃, the die head and grinding head temperatures are 170-180℃, and the screw speed is 180-200 rpm. After being melted and plasticized, the material is filtered through a double-stage filter screen consisting of three layers of 60-100 mesh and two layers of 80-120 mesh. After being stretched, cooled by water, granulated, dehydrated, and screened, it is homogenized for 5-10 minutes to finally obtain the special color masterbatch.

[0023] The design concept of this invention follows a strategy of step-by-step optimization and functional synergy. First, a blend of high-density polyethylene and linear low-density polyethylene is selected as the carrier resin to balance the rigidity and toughness of the material, providing basic mechanical properties for the masterbatch. Then, addressing the core issues of pigment agglomeration and poor compatibility with the resin, a functional coating layer is designed to be constructed on the surface of the composite pigment. Through the hydrolytic condensation of silane compounds, the selected functional materials are firmly bonded to the pigment surface. This coating layer acts as a bridge, significantly enhancing the interfacial bonding between the pigment and the resin, and also acts as a barrier, physically isolating external mechanical wear and UV aging factors. Furthermore, for… Breaking through the performance limits of single-function materials, a compound synergistic design is adopted, combining nano-hydroxyapatite, which provides mechanical reinforcement, with nano-cerium dioxide, which provides UV shielding, to achieve a synergistic effect on wear resistance and weather resistance. Furthermore, micron-scale reinforcements such as calcium sulfate whiskers are introduced to form a multi-scale reinforcement network with nanomaterials, achieving another breakthrough in wear resistance. Finally, through precise segmented mixing, low-temperature kneading, and controllable twin-screw extrusion processes, the uniform dispersion of each component, sufficient interfacial reaction, and avoidance of high-temperature degradation are ensured, thereby ultimately producing a special masterbatch with high coloring power, excellent weather resistance, superior wear resistance, and good processing stability.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects: 1) This invention significantly improves the dispersion stability and interfacial bonding of pigments in the resin matrix through a unique surface modification technology, thereby effectively improving the color uniformity and color brightness of the masterbatch.

[0025] 2) The color masterbatch prepared by this invention has excellent weather resistance and wear resistance, which can significantly delay the color fading and surface wear of products in harsh outdoor environments and greatly extend their service life.

[0026] 3) The preparation process of the present invention improves production efficiency and product quality stability by optimizing segmented processing and temperature control, while ensuring that the components are fully integrated and perform well. Detailed Implementation

[0027] Some material parameters and their sources: High-density polyethylene, grade: DMDA8920, manufacturer (origin): Dow Chemical, USA.

[0028] Linear low-density polyethylene, grade: LL 1201BS, brand: ExxonMobil.

[0029] Titanium dioxide, product specifications: 0.4µm, active ingredient content: ≥93%, crystal form: rutile, pH value: 7.9, density: 4.0g / cm³ 3 Brand: DuPont, USA.

[0030] Nano zinc oxide, average particle size: 50nm, purity: 99.9%, color: white.

[0031] Nano-cerium dioxide, average particle size: 50nm, purity: 99.9%, specific surface area (m²) 2 / g): 30, bulk density (g / cm³) 3 : 0.47, density (g / cm³) 3 ): 7.1, Crystal form: spherical, Color: white.

[0032] Nano-silica, particle size: 50nm, purity: 99.9%, crystal morphology: spherical.

[0033] Nano-alumina, crystal form: α phase, particle size (nm): 30nm, content (%): 99.99, specific surface area (m / g): 20-50.

[0034] Nano-zirconia, average particle size 50nm, purity (%): 99.9, crystal phase: tetragonal, color: white.

[0035] Nano-sized indium tin oxide, average particle size: 50nm, purity %: 99.9%, microstructure: spherical, color: light yellow.

[0036] Nano-hydroxyapatite, average particle size: 30nm, purity %: 99, color and appearance: white powder.

[0037] Calcium sulfate whiskers, appearance: white flocculent powder, Mohs hardness: 2-4, whiteness: ≥95%, chemical composition: CaSO4, purity: ≥98%, heat resistance: 1000℃, melting point: 1450℃, moisture: <1.5%, density: 2.69 g / cm³ 3Shape: needle-like fiber, diameter: 1-4μm, length: 10-300μm, aspect ratio: 40-80 (90%).

[0038] All other raw materials used in the embodiments and comparative examples of this invention are commercially available products.

[0039] Example 1 The preparation method of a special color masterbatch for PE heat-resistant pipes and fittings is as follows, in parts by weight: 2.13 parts of modified composite pigment and 0.5 parts of zinc stearate were premixed in a high-speed mixer at room temperature for 8 minutes to prepare a uniform pigment concentrate. Next, a segmented hot-mixing process was performed. 60 parts of a carrier resin composed of high-density polyethylene and linear low-density polyethylene in a mass ratio of 3.5:1.5 and 15 parts of titanium dioxide were placed in a mixer and mixed at 90°C for 6 minutes. The material was then cooled to 55°C, and the aforementioned pigment concentrate, along with 0.3 parts of antioxidant 1010, 0.3 parts of antioxidant 168, and 0.2 parts of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, were added. Mixing continued at 55°C. After mixing for 6 minutes, a uniformly mixed material is obtained. Finally, melt extrusion granulation is performed: the obtained material is melt-extruded through a parallel co-rotating twin-screw extruder. The extruder feed port temperature is controlled at 130℃, the temperatures of zones 1 to 9 of the extruder body are 150℃, 180℃, 180℃, 180℃, 180℃, 180℃, 175℃, 175℃, and the die head and grinding head temperature is 175℃. The screw speed is 190 rpm. After being melt-plasticized, the material is filtered through a double-stage filter screen with three layers of 80 mesh and two layers of 100 mesh. After being stretched, cooled by water, granulated, dehydrated, and screened, it is homogenized for 8 minutes to finally obtain the special color masterbatch.

[0040] The preparation method of the modified composite pigment is as follows, in parts by weight: S1. Add 0.28 parts of functional material to 30 parts of anhydrous ethanol and treat with ultrasound at 200W for 20 minutes to obtain a dispersion; then, add 0.15 parts of silane compound to 20 parts of 75wt% ethanol aqueous solution, adjust the pH of the system to 8 with 25wt% ammonia water, and then mix with the aforementioned dispersion; stir continuously at 60℃ for 2 hours to obtain a modified coating solution. S2. Add 2.13 parts of composite pigment to the modified coating solution prepared in step S1, and treat it for 2 hours under ultrasonic-assisted mechanical stirring at 250W. After centrifugation and vacuum drying at 50℃ for 12 hours, the product is ball-milled and passed through a 300-mesh sieve to obtain the modified composite pigment.

[0041] The composite pigment is composed of titanium yellow, ultramarine blue, iron oxide and carbon black in a mass ratio of 1.2:0.8:0.08:0.05.

[0042] The functional material is titanium dioxide.

[0043] The silane compound is composed of methyltrimethoxysilane and tridecafluorooctyltrimethoxysilane in a mass ratio of 4:1.

[0044] Example 2 The preparation method of a special color masterbatch for PE heat-resistant pipes and fittings is basically the same as that in Example 1, except that the functional material in the preparation method of the modified composite pigment is nano zinc oxide.

[0045] Example 3 The preparation method of a special color masterbatch for PE heat-resistant pipes and fittings is basically the same as that in Example 1, except that the functional material in the preparation method of the modified composite pigment is nano-cerium dioxide.

[0046] Example 4 The preparation method of a special color masterbatch for PE heat-resistant pipes and fittings is basically the same as that in Example 1, except that the functional material in the preparation method of the modified composite pigment is nano-silica.

[0047] Example 5 The preparation method of a special color masterbatch for PE heat-resistant pipes and fittings is basically the same as that in Example 1, except that the functional material in the preparation method of the modified composite pigment is nano-alumina.

[0048] Example 6 The preparation method of a special color masterbatch for PE heat-resistant pipes and fittings is basically the same as that in Example 1, except that the functional material in the preparation method of the modified composite pigment is nano-zirconia.

[0049] Example 7 The preparation method of a special color masterbatch for PE heat-resistant pipes and fittings is basically the same as that in Example 1, except that the functional material in the preparation method of the modified composite pigment is nano-indium tin oxide.

[0050] Example 8 The preparation method of a special color masterbatch for PE heat-resistant pipes and fittings is basically the same as that in Example 1, except that the functional material in the preparation method of the modified composite pigment is nano-hydroxyapatite.

[0051] Example 9 The preparation method of a special color masterbatch for PE heat-resistant pipes and fittings is basically the same as that in Example 1, except that the functional material in the preparation method of the modified composite pigment is composed of nano hydroxyapatite and nano cerium dioxide in a mass ratio of 5:2.

[0052] Example 10 The preparation method of a special color masterbatch for PE heat-resistant pipes and fittings is basically the same as that in Example 1, except that the functional material in the preparation method of the modified composite pigment is composed of nano-silica and nano-alumina in a mass ratio of 5:2.

[0053] Example 11 The preparation method of a special color masterbatch for PE heat-resistant pipes and fittings is basically the same as that in Example 1, except that the functional material in the preparation method of the modified composite pigment is composed of titanium dioxide and nano zinc oxide in a mass ratio of 5:2.

[0054] Example 12 The preparation method of a special color masterbatch for PE heat-resistant pipes and fittings is basically the same as that in Example 1, except that the functional material in the preparation method of the modified composite pigment is composed of nano hydroxyapatite, nano cerium dioxide and calcium sulfate whiskers in a mass ratio of 5:2:1.

[0055] Comparative Example 1 The preparation method of a special color masterbatch for PE heat-resistant pipes and fittings is basically the same as that in Example 1, except that the modified composite pigment is replaced with an equal amount of composite pigment.

[0056] The composite pigment is the same as in Example 1.

[0057] Test Example 1 Abrasion resistance test: Refer to the relevant methods in GB / T 1768-2006 "Determination of Abrasion Resistance of Paints and Varnishes".

[0058] The color masterbatches prepared in each embodiment and comparative example were mixed with PE base material at a fixed weight ratio of 9%, and injection molded into smooth plastic specimens with standard dimensions of 100mm × 100mm × 2mm using an injection molding machine at a melt temperature of 220℃. The specimen was fixed on a Taber abrasion tester, and a 1000g load was applied using a CS-10 grinding wheel. After rotating the specimen 1000 times, it was removed. The mass loss (mg) of the specimen before and after abrasion was accurately measured. The smaller the mass loss, the better the abrasion resistance.

[0059] The test results are shown in Table 1.

[0060] Table 1 Test Example 2 Weather resistance test: This indicator directly verifies the material's ability to retain color under long-term ultraviolet irradiation, and is key to proving the core function of cerium dioxide and its synergistic effect with the overall structure.

[0061] A smooth plastic sample was prepared according to the method in Test Example 1. The sample was then placed in a xenon lamp aging test chamber, and the irradiation intensity was set to 60 ± 2 W / m². 2 (In the 300nm-400nm ultraviolet band), blackboard temperature: 63±3℃, chamber temperature: 45±3℃, relative humidity: 50±5%, spraying cycle: spraying for 18 minutes after every 102 minutes of light exposure, total test duration: 500 hours.

[0062] After the test, remove the color plates. Use a colorimeter to measure the color change of the color plates before and after aging, expressed as the total color difference ΔE. The smaller the ΔE value, the better the color stability and the better the weather resistance.

[0063] The relevant test data are summarized in Table 2.

[0064] Table 2 The possible mechanism by which the modified composite pigments of this invention improve performance lies in constructing a robust functional material coating layer on the pigment surface using silane compounds. This coating layer improves the compatibility and interfacial bonding between the pigment and the PE resin matrix, and physically isolates the internal pigment core from direct attacks by external factors such as mechanical friction and UV aging. This results in the superior performance of Examples 1-8 compared to the unmodified Comparative Example 1. Among single functional materials, nano-hydroxyapatite exhibits the best wear resistance due to its unique nanowire structure forming a dense network reinforcement layer; while nano-cerium dioxide, as a UV absorber, delays the photo-oxidative aging of the matrix, exhibiting the best weather resistance. When nano-hydroxyapatite and nano-cerium dioxide are combined, they produce a significant synergistic effect. The physical reinforcement provided by hydroxyapatite and the chemical protection provided by cerium dioxide complement each other, and the dense network formed by the former promotes the uniform distribution of cerium dioxide, while the latter ensures the durability of the reinforcement network, achieving a leapfrog improvement in overall performance. In contrast, silicon dioxide and alumina have overlapping functions, and titanium dioxide and zinc oxide lack sufficient synergy. Further, calcium sulfate whiskers were introduced to form a ternary system, constructing a multi-scale synergistic reinforcement network. Hydroxyapatite nanowires form the basic framework, while micron-sized calcium sulfate whiskers intertwine with it as a rigid reinforcement, much like a composite structure of steel bars and fine mesh. This achieves another breakthrough in wear resistance on the basis of the long-term stability guaranteed by cerium dioxide.

Claims

1. A special color masterbatch for PE heat-resistant pipes and fittings, characterized in that, Includes the following components by weight: 40-65 parts carrier resin, 8-25 parts opacifier, 1.5-2.5 parts modified composite pigment, and 0-2 parts functional additives; The preparation method of the modified composite pigment is as follows: S1. The functional material is added to anhydrous ethanol and ultrasonically treated to obtain a dispersion; the silane compound is added to an ethanol aqueous solution, the pH of the system is adjusted with ammonia, and then mixed with the dispersion, heated and stirred to obtain a modified coating solution. S2. Add the composite pigment to the modified coating solution prepared in step S1, and perform mechanical stirring under ultrasonic assistance. After centrifugation, drying, ball milling and sieving, the modified composite pigment is obtained. The functional material is composed of nano-hydroxyapatite and nano-cerium dioxide in a mass ratio of 4-6:1-3; The silane compound is composed of methyltrimethoxysilane and tridecafluorooctyltrimethoxysilane in a mass ratio of 3-5:0.5-2.

2. The color masterbatch for PE heat-resistant pipes and fittings as described in claim 1, characterized in that, The carrier resin is composed of high-density polyethylene and linear low-density polyethylene in a mass ratio of 3-4:1-2; the light-blocking agent is titanium dioxide; and the functional additive is at least one of antioxidant, light stabilizer, and high-efficiency dispersant.

3. The color masterbatch for PE heat-resistant pipes and fittings as described in claim 1 or 2, characterized in that, The functional additives are composed of antioxidants, light stabilizers, and high-efficiency dispersants in a mass ratio of 0.4-0.8:0.1-0.3:0.3-0.

8. The antioxidants are at least one of antioxidant 1010, antioxidant 168, and antioxidant 1076. The light stabilizers are one or more of benzoic acid (2,2,6,6-tetramethyl-4-hydroxypiperidine), bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2,6-di-tert-butyl-p-cresol, propyl gallate, 6-tert-butyl-m-cresol, 6-tert-butyl-2,4-dimethylphenol, and 2,6-di-tert-butyl-4-methylphenol. The high-efficiency dispersants are at least one of zinc stearate, fatty acid amide, and polyethylene wax.

4. The color masterbatch for PE heat-resistant pipes and fittings as described in claim 1, characterized in that, The preparation method of the modified composite pigment is as follows, in parts by weight: S1. Add 0.2-0.35 parts of functional material to 20-40 parts of anhydrous ethanol, and treat with ultrasound at 100-300W for 10-30 minutes to obtain a dispersion. Subsequently, 0.1-0.2 parts of the silane compound were added to 10-30 parts of a 70-80 wt% aqueous ethanol solution, and the pH of the system was adjusted to 7.5-9 with 20-27 wt% ammonia solution. The mixture was then mixed with the aforementioned dispersion. The mixture was stirred continuously at 50-70°C for 1-3 hours to obtain the modified coating solution. S2. Add 2-3.5 parts of composite pigment to the modified coating solution prepared in step S1, and treat it for 1-3 hours under ultrasonic-assisted mechanical stirring at 100-300W. After centrifugation and vacuum drying at 40-60℃ for 5-20 hours, the product is ball-milled and passed through a 200-300 mesh sieve to obtain the modified composite pigment.

5. The color masterbatch for PE heat-resistant pipes and fittings as described in claim 1, characterized in that, The composite pigment is composed of titanium yellow, ultramarine blue, iron oxide, and carbon black in a mass ratio of 1-1.5:0.5-1:0.05-0.1:0.03-0.

1.

6. The color masterbatch for PE heat-resistant pipes and fittings as described in claim 1, characterized in that, The functional material can also be composed of nano-hydroxyapatite, nano-cerium dioxide and calcium sulfate whiskers in a mass ratio of 4-6:1-3:0.5-2.

7. A method for preparing a special color masterbatch for PE heat-resistant pipes and fittings as described in any one of claims 1-6, characterized in that, The method is as follows: Modified composite pigments and high-efficiency dispersants are premixed in a high-speed mixer at room temperature for 5-10 minutes to prepare a uniform pigment concentrate. Next, a segmented hot-mixing kneading process is performed, where the carrier resin and opacifier are placed in a mixer and mixed at 80-95°C for 3-10 minutes. The material is then cooled to 50-60°C, and the aforementioned pigment concentrate, antioxidant, and light stabilizer are added. Mixing continues at 50-60°C for another 3-10 minutes to obtain a uniformly mixed material. Finally, melt extrusion granulation is performed: the resulting material... The material is melt-extruded through a parallel co-rotating twin-screw extruder. The extruder feed port temperature is controlled to be below 150℃, the temperatures of zones 1 to 9 of the extruder body are each independently 150-210℃, the die head and grinding head temperatures are 170-180℃, and the screw speed is 180-200 rpm. After being melted and plasticized, the material is filtered through a double-stage filter screen consisting of three layers of 60-100 mesh and two layers of 80-120 mesh. After being stretched, cooled by water, granulated, dehydrated, and screened, it is homogenized for 5-10 minutes to finally obtain the special color masterbatch.

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