Brown color master batch used for PBT base material and capable of improving product color difference and preparation method of brown color master batch

Abstract

The invention provides a brown color master batch used for a PBT substrate and capable of improving product color difference and a preparation method of the brown color master batch, belongs to the technical field of high polymer materials, and aims to solve the technical problem that color difference easily occurs in the injection molding process of a brown plastic product. The brown color master batch comprises the following raw material components: 238.5-241.5 permillage of a brown inorganic pigment; a dispersing auxiliary agent: 145.5 to 155.5 per mill; and the balance of PBT. The total mass of the raw materials is 1000%. The surface of the pigment is anchored through MAH-g-PE chemical bonds and coated through EMA hydrogen bonds to form a bimolecular layer barrier, uniform dispersion processing of the pigment is achieved, delta E is smaller than 3.0, and the color difference problem of products is effectively solved.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a brown masterbatch. Background Art

[0002] In automotive electrical systems, connectors are key components for circuit connection. The color consistency of their sheaths is crucial for ensuring assembly efficiency and maintenance convenience. With the development of intelligent and modular vehicles, automakers have increased their color accuracy requirements for connector sheaths to ΔE ≤ 3.0. This is particularly true for PBT sheaths in darker tones, such as brown, where color variation has become a key bottleneck limiting product yield.

[0003] In the existing technology, solutions to the color difference problem of injection molded products mainly focus on three dimensions: material modification, process optimization, and equipment improvement. At the material level, the method of improving the compatibility of the masterbatch with the substrate is usually adopted, such as using maleic anhydride grafted PBT (PBT-g-MAH) as a masterbatch carrier, or surface silane treatment of the pigment to improve dispersibility. In terms of process control, the industry generally adopts segmented temperature control (such as barrel temperature gradient setting) and multi-stage injection pressure mode, attempting to uniformly distribute the masterbatch by precisely controlling the melt flow state. Equipment improvement often involves screw structure optimization (such as using barrier screws to enhance shear mixing) and mold flow channel modification (such as the application of hot runner systems) to reduce the agglomeration of masterbatch during processing.

[0004] However, the existing technology still has significant limitations in practical applications. Although the material modification scheme can improve compatibility, the addition of a high proportion of masterbatch (brown usually requires more than 3%) will still lead to a surge in melt viscosity, resulting in deterioration of processing fluidity, especially when molding complex structure sheaths, which is prone to insufficient filling defects; in terms of process optimization, the traditional temperature-pressure control strategy is difficult to dynamically adapt to PBT crystallization rate fluctuations (such as mold temperature drift caused by ambient temperature changes), and the problem of "color drift between batches" often occurs. The more prominent problem is that the existing technology has failed to systematically solve the inherent contradiction between PBT substrate and brown masterbatch: on the one hand, iron oxide-based brown pigments (density 5.24g / cm 3 ) and PBT (1.31g / cm 3) results in a gradient color difference (lighter at the top, darker at the bottom) in the masterbatch during the melt cooling phase of the injection molding process due to gravity settling. Furthermore, PBT's semi-crystalline nature makes its crystallinity extremely sensitive to cooling rate. Local temperature differences in the mold (such as those exceeding 5°C due to improper cooling channel design) can trigger variations in crystallinity, leading to inconsistent light reflectivity and visible "light and dark streaks." These issues are particularly prominent in large, flat sheaths (such as connector housings with a length greater than 100mm). Traditional solutions struggle to control local color differences within the range of ΔE ≤ 3.0, severely impacting production efficiency and cost control.

[0005] Furthermore, existing technologies lack dynamic monitoring of the mechanisms that cause color variability. Traditional offline color variability testing (e.g., hourly sampling) provides no real-time feedback on the masterbatch dispersion status during production. By the time color variability exceeds the specified limit, batch defects have often already occurred. Existing technologies addressing the color variability issue in brown PBT sheaths face multiple challenges, including material compatibility, process stability, equipment costs, and testing timeliness. A systematic solution is urgently needed that balances dispersion efficiency, process adaptability, and cost control. Summary of the Invention

[0006] In order to solve the technical problem that brown plastic products are prone to color difference during the injection molding process, the present invention provides a brown masterbatch for PBT substrate that can improve product color difference and a preparation method thereof.

[0007] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0008] A brown masterbatch for PBT substrates capable of improving product color difference, comprising the following raw material components:

[0009] Brown inorganic pigment: 238.5-241.5‰;

[0010] Dispersing agent: 145.5~155.5‰;

[0011] The balance is PBT; the total mass of the raw materials is 1000‰.

[0012] Preferably, the brown inorganic pigment includes black pigment, inorganic zinc iron yellow and iron oxide red.

[0013] Preferably, the black pigment is carbon black.

[0014] The proportions of each raw material component are as follows:

[0015] Black pigment: 3.5~6.5‰;

[0016] Inorganic zinc iron yellow: 83.5~86.5‰;

[0017] Iron oxide red: 148.5~151.5‰;

[0018] Dispersing agent: 145.5~155.5‰;

[0019] The balance is PBT; the total mass of raw materials is 1000‰.

[0020] The dispersing aid consists of maleic anhydride grafted polyethylene and ethylene-methyl acrylate.

[0021] Preferably, the maleic anhydride grafted polyethylene (MAH-g-PE) is prepared by introducing polar maleic anhydride groups into the polyethylene molecular chain. It is often prepared by a melt grafting method, for example, polyethylene, maleic anhydride (MAH) and an initiator are mixed and then heated to react to produce MAH-g-PE.

[0022] Preferably, the ethylene-methyl acrylate copolymer (EMA) is a thermoplastic elastomer with excellent performance, which combines the chemical resistance of polyethylene with the polarity and flexibility of acrylate, and is prepared by copolymerization of ethylene and methyl acrylate (MA) via a free radical initiator.

[0023] The maleic anhydride grafted polyethylene accounts for 95.5-100.5‰ of the total mass of the raw material components, and the ethylene-methyl acrylate accounts for 50-55‰ of the total mass of the raw material components.

[0024] Preferably, the maleic anhydride grafted polyethylene accounts for 95.5 to 100.5‰ of the total mass of the raw material components, and the ethylene-methyl acrylate accounts for 50 to 55‰ of the total mass of the raw material components.

[0025] A method for preparing a brown masterbatch for a PBT substrate capable of improving product color difference comprises the following steps:

[0026] (1) brown inorganic pigment, dispersing aid and PBT are mixed according to proportion;

[0027] (2) The mixed raw materials are melted and extruded in an extruder, cooled, and then granulated in a pelletizer to obtain brown masterbatch.

[0028] The temperature of the melt extrusion is 230-250°C.

[0029] Beneficial effects of the present invention:

[0030] (1) The present invention uses the anhydride groups in maleic anhydride to chemically react with the hydroxyl groups (—OH) and metal ions on the surface of the inorganic pigment to form ester bonds or ionic bonds, so that MAH-g-PE is firmly anchored on the pigment surface. The non-polar polyethylene main chain of MAH-g-PE has similar polarity to the fatty chain segments (butanediol units) in PBT, and physical compatibility is achieved through molecular chain entanglement. Secondly, the long chain structure of MAH-g-PE wraps around the pigment particles, forming a physical barrier to prevent the inorganic pigment from re-aggregating due to van der Waals forces. The acrylate groups form hydrogen bonds or dipole-dipole interactions with the polar groups (such as —OH) on the surface of the inorganic pigment to achieve strong adsorption, while the ethylene segments are compatible with the non-polar PBT segments, acting as a "bridge" to connect the pigment and PBT. Through the strong interaction between the polar groups and the inorganic pigment, as well as the compatibility with the non-polar PBT segments, a stable "pigment-additive-PBT" interface layer is constructed, ultimately achieving high dispersion of the masterbatch.

[0031] (2) MAH-g-PE chemical bonds anchor the pigment surface, while EMA hydrogen bonds coat it, forming a bilayer barrier that enables uniform pigment dispersion and processing. MAH-g-PE long chains entangle to prevent reagglomeration under strong shear, while EMA reduces melt viscosity, improves fluidity, and resolves product color variation. Furthermore, by utilizing MAH-g-PE chemical bond bridging and the toughening effect of EAA, the notched impact strength retention rate of the PBT substrate is ≥95%, and the tensile strength retention rate is ≥95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 This is a front view of an injection molded part prepared with the brown masterbatch prepared in Example 1.

[0034] Figure 2 This is a back view of an injection molded part prepared with the brown masterbatch prepared in Example 1.

[0035] Figure 3 This is a front view of an injection molded part prepared with the brown masterbatch prepared in Comparative Example 1.

[0036] Figure 4 This is the back view of the injection molded part prepared by adding the brown masterbatch of Comparative Example 1.

[0037] Figure 5 This is a front view of an injection molded part prepared with the brown masterbatch prepared in Comparative Example 2.

[0038] Figure 6 The back view of the injection molded part prepared by adding the brown masterbatch of Comparative Example 2.

[0039] Figure 7 This is a front view of an injection molded part prepared by adding the brown masterbatch of Comparative Example 3.

[0040] Figure 8 This is a back view of an injection molded part made with brown masterbatch prepared in Comparative Example 3. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0042] Example 1

[0043] A brown masterbatch for PBT substrates capable of improving product color difference, comprising the following raw materials in the following mass proportions:

[0044] Carbon black: 5‰;

[0045] Inorganic zinc iron yellow: 85‰;

[0046] Iron oxide red: 150‰;

[0047] Maleic anhydride grafted polyethylene: 100‰;

[0048] Ethylene-methyl acrylate: 50‰;

[0049] PBT: 610‰; total raw material amount is 1000‰.

[0050] The preparation method of brown masterbatch comprises the following steps:

[0051] (1) PBT, carbon black, inorganic zinc iron yellow, iron oxide red, maleic anhydride grafted polyethylene, and ethylene-methyl acrylate are mixed in a high-speed mixer according to a certain proportion;

[0052] (2) The raw materials mixed in step (1) are fed into a twin-screw extruder, melt-mixed at 250° C. under strong shear force, pigment agglomerates are crushed, and the dispersant-coated particles are uniformly dispersed at the microscopic level. After the reaction is completed, the melt is extruded through a die head and then cooled and granulated.

[0053] (3) Cooling and drying the granules obtained in step (2) to obtain a brown masterbatch.

[0054] Example 2

[0055] A brown masterbatch for PBT substrates capable of improving product color difference, comprising the following raw materials in the following mass proportions:

[0056] Carbon black: 5‰;

[0057] Inorganic zinc iron yellow: 85‰;

[0058] Iron oxide red: 150‰;

[0059] Maleic anhydride grafted polyethylene: 100.5‰;

[0060] Ethylene methyl acrylate: 55‰;

[0061] PBT: 610‰; total raw material amount is 1000‰.

[0062] The preparation method of brown masterbatch comprises the following steps:

[0063] (1) PBT, carbon black, inorganic zinc iron yellow, iron oxide red, maleic anhydride grafted polyethylene, and ethylene-methyl acrylate are mixed in a high-speed mixer according to a certain proportion;

[0064] (2) The raw materials mixed in step (1) are fed into a twin-screw extruder, melt-mixed at 250° C. under strong shear force, pigment agglomerates are crushed, and the dispersant-coated particles are uniformly dispersed at the microscopic level. After the reaction is completed, the melt is extruded through a die head and then cooled and granulated.

[0065] (3) Cooling and drying the granules obtained in step (2) to obtain a brown masterbatch.

[0066] Example 3

[0067] A brown masterbatch for PBT substrates capable of improving product color difference, comprising the following raw materials in the following mass proportions:

[0068] Carbon black: 5‰;

[0069] Inorganic zinc iron yellow: 85‰;

[0070] Iron oxide red: 150‰;

[0071] Maleic anhydride grafted polyethylene: 95.5‰;

[0072] Ethylene-methyl acrylate: 50‰;

[0073] PBT: 610‰; total raw material amount is 1000‰.

[0074] The preparation method of brown masterbatch comprises the following steps:

[0075] (1) PBT, carbon black, inorganic zinc iron yellow, iron oxide red, maleic anhydride grafted polyethylene, and ethylene-methyl acrylate are mixed in a high-speed mixer according to a certain proportion;

[0076] (2) The raw materials mixed in step (1) are fed into a twin-screw extruder, melt-mixed at 250° C. under strong shear force, pigment agglomerates are crushed, and the dispersant-coated particles are uniformly dispersed at the microscopic level. After the reaction is completed, the melt is extruded through a die head and then cooled and granulated.

[0077] (3) Cooling and drying the granules obtained in step (2) to obtain a brown masterbatch.

[0078] Example 4

[0079] A brown masterbatch for PBT substrates capable of improving product color difference, comprising the following raw materials in the following mass proportions:

[0080] Carbon black: 3.5‰;

[0081] Inorganic zinc iron yellow: 86.5‰;

[0082] Iron oxide red: 148.5‰;

[0083] Maleic anhydride grafted polyethylene: 100‰;

[0084] Ethylene-methyl acrylate: 50‰;

[0085] PBT: 610‰; total raw material amount is 1000‰.

[0086] The preparation method of brown masterbatch comprises the following steps:

[0087] (1) PBT, carbon black, inorganic zinc iron yellow, iron oxide red, maleic anhydride grafted polyethylene, and ethylene-methyl acrylate are mixed in a high-speed mixer according to a certain proportion;

[0088] (2) The raw materials mixed in step (1) are fed into a twin-screw extruder, melt-mixed at 240° C. under strong shear force, pigment agglomerates are crushed, and the dispersant-coated particles are dispersed uniformly at the microscopic level. After the reaction is completed, the melt is extruded through a die head and then cooled and granulated.

[0089] Example 5

[0090] A brown masterbatch for PBT substrates capable of improving product color difference, comprising the following raw materials in the following mass proportions:

[0091] Carbon black: 6.5‰;

[0092] Inorganic zinc iron yellow: 83.5‰;

[0093] Iron oxide red: 151.5‰;

[0094] Maleic anhydride grafted polyethylene: 100‰;

[0095] Ethylene methyl acrylate: 52‰;

[0096] PBT: 610‰; total raw material amount is 1000‰.

[0097] The preparation method of brown masterbatch comprises the following steps:

[0098] (1) PBT, carbon black, inorganic zinc iron yellow, iron oxide red, maleic anhydride grafted polyethylene, and ethylene-methyl acrylate are mixed in a high-speed mixer according to a certain proportion;

[0099] (2) The raw materials mixed in step (1) are fed into a twin-screw extruder, melt-mixed at 230° C. under strong shear force, pigment agglomerates are crushed, and the dispersant-coated particles are dispersed uniformly at the microscopic level. After the reaction is completed, the melt is extruded through a die head and then cooled and granulated.

[0100] Comparative Example 1

[0101] A brown masterbatch comprising the following raw materials in the following proportions by mass:

[0102] Carbon black: 5‰;

[0103] Inorganic zinc iron yellow: 85‰;

[0104] Iron oxide red: 150‰;

[0105] Maleic anhydride grafted polyethylene: 150‰;

[0106] PBT: 610‰; total raw material amount is 1000‰.

[0107] The preparation method of brown masterbatch comprises the following steps:

[0108] (1) PBT, carbon black, inorganic zinc iron yellow, iron oxide red, and maleic anhydride grafted polyethylene are mixed in a high-speed mixer according to a certain proportion;

[0109] (2) The raw materials mixed in step (1) are fed into a twin-screw extruder, melt-mixed at 250° C. under strong shear force, pigment agglomerates are crushed, and the dispersant-coated particles are uniformly dispersed at the microscopic level. After the reaction is completed, the melt is extruded through a die head and then cooled and granulated.

[0110] (3) Cooling and drying the granules obtained in step (2) to obtain a brown masterbatch.

[0111] Comparative Example 2

[0112] A brown masterbatch comprising the following raw materials in the following proportions by mass:

[0113] Carbon black: 5‰;

[0114] Inorganic zinc iron yellow: 85‰;

[0115] Iron oxide red: 150‰;

[0116] Ethylene methyl acrylate: 150‰;

[0117] PBT: 610‰; total raw material amount is 1000‰.

[0118] The preparation method of brown masterbatch comprises the following steps:

[0119] (1) PBT, carbon black, inorganic zinc iron yellow, iron oxide red, maleic anhydride grafted polyethylene, and ethylene-methyl acrylate are mixed in a high-speed mixer according to a certain proportion;

[0120] (2) The raw materials mixed in step (1) are fed into a twin-screw extruder, melt-mixed at 250° C. under strong shear force, pigment agglomerates are crushed, and the dispersant-coated particles are uniformly dispersed at the microscopic level. After the reaction is completed, the melt is extruded through a die head and then cooled and granulated.

[0121] (3) Cooling and drying the granules obtained in step (2) to obtain a brown masterbatch.

[0122] Comparative Example 3

[0123] A brown masterbatch for PBT substrates capable of improving product color difference, comprising the following raw materials in the following mass proportions:

[0124] Carbon black: 5‰;

[0125] Inorganic zinc iron yellow: 85‰;

[0126] Iron oxide red: 150‰;

[0127] Polyethylene low molecular weight wax: 150‰;

[0128] PBT: 610‰; total raw material amount is 1000‰.

[0129] The preparation method of brown masterbatch comprises the following steps:

[0130] (1) PBT, carbon black, inorganic zinc iron yellow, iron oxide red, and polyethylene low molecular weight wax are mixed in a high-speed mixer according to a certain proportion;

[0131] (2) The raw materials mixed in step (1) are fed into a twin-screw extruder, melt-mixed at 250° C. under strong shear force, pigment agglomerates are crushed, and the dispersant-coated particles are uniformly dispersed at the microscopic level. After the reaction is completed, the melt is extruded through a die head and then cooled and granulated.

[0132] (3) Cooling and drying the granules obtained in step (2) to obtain a brown masterbatch.

[0133] Comparative Example 4

[0134] A brown masterbatch for PBT substrates capable of improving product color difference, comprising the following raw materials in the following mass proportions:

[0135] Carbon black: 5‰;

[0136] Inorganic zinc iron yellow: 85‰;

[0137] Iron oxide red: 150‰;

[0138] Copolymer polyethylene wax: 150‰;

[0139] PBT: 610‰; total raw material amount is 1000‰.

[0140] The preparation method of brown masterbatch comprises the following steps:

[0141] (1) PBT, carbon black, inorganic zinc iron yellow, iron oxide red, and copolymerized polyethylene wax are mixed in a high-speed mixer according to a certain proportion;

[0142] (2) The raw materials mixed in step (1) are fed into a twin-screw extruder, melt-mixed at 250° C. under strong shear force, pigment agglomerates are crushed, and the dispersant-coated particles are uniformly dispersed at the microscopic level. After the reaction is completed, the melt is extruded through a die head and then cooled and granulated.

[0143] (3) Cooling and drying the granules obtained in step (2) to obtain a brown masterbatch.

[0144] Comparative Example 5

[0145] A brown masterbatch for PBT substrates capable of improving product color difference, comprising the following raw materials in the following mass proportions:

[0146] Carbon black: 5‰;

[0147] Inorganic zinc iron yellow: 85‰;

[0148] Iron oxide red: 150‰;

[0149] Maleic anhydride grafted polyethylene: 70‰;

[0150] Ethylene-methyl acrylate: 30‰;

[0151] PBT: 660‰; total raw material amount is 1000‰.

[0152] The preparation method of brown masterbatch comprises the following steps:

[0153] (1) PBT, carbon black, inorganic zinc iron yellow, iron oxide red, and copolymerized polyethylene wax are mixed in a high-speed mixer according to a certain proportion;

[0154] (2) The raw materials mixed in step (1) are fed into a twin-screw extruder, melt-mixed at 250° C. under strong shear force, pigment agglomerates are crushed, and the dispersant-coated particles are uniformly dispersed at the microscopic level. After the reaction is completed, the melt is extruded through a die head and then cooled and granulated.

[0155] (3) Cooling and drying the granules obtained in step (2) to obtain a brown masterbatch.

[0156] The brown masterbatch prepared in Example 1 and Comparative Examples 1-4 was added to PBT resin and parts were prepared by injection molding. Taking the preparation of the brown masterbatch in Example 1 as an example, the preparation method of the injection molded parts includes the following steps:

[0157] (1) Production method of substrate: Polybutylene terephthalate (26092-94-2), ethylene-butyl acrylate-glycidyl methacrylate (6683-19-8), pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (115-83-3) and other additives are mixed and evenly dispersed in a mass ratio of 90:5:5. The mixed material is stably and accurately fed into the first zone (feeding section) of the extruder through the main feeder. The processing temperature is 240-250°C. The temperature of the feeding section is slightly lower at 240°C to prevent bridging. The temperature of the melting section and homogenizing section is higher at 250°C to ensure melt plasticization. The melted and evenly blended material is extruded into strips through the extruder die head and then water-cooled and pelletized.

[0158] (2) Injection molding process of parts: The masterbatch is uniformly mixed in the base material at a ratio of 3wt%, and the mixture is melted and sheared by the rotation of the screw of the injection molding machine. The masterbatch is evenly dispersed in the melt and then injected into the mold cavity at high speed. After cooling, the mold is opened to obtain the parts.

[0159] First, the mechanical properties of the injection molded parts containing the masterbatch prepared in Example 1 were tested and compared with those without the masterbatch. The results are shown in Table 1. After adding the masterbatch, the notched impact strength retention rate of the PBT substrate was 96%, and the tensile strength retention rate was 96%.

[0160] Table 1 Comparison of material properties

[0161]

[0162] According to the above method, parts with the brown masterbatch prepared in Comparative Examples 1-4 were prepared in sequence. The optical images of the parts prepared in Example 1 and Comparative Examples 1-4 were as follows: Figure 1-8As shown, it can be seen with the naked eye that there are blocks of different shades and stripes on the front and back sides and the same side of the corresponding parts of Examples 1-4, with obvious color differences. Subsequently, a spectrophotometer was used to test the L, a, and b values ​​of different parts produced with masterbatches containing different dispersing additives, and the color difference ΔE was compared with the standard color number RAL8002. The test results are shown in Table 2

[0163] Table 2 ΔE comparison table of different dispersing additives and standard color numbers

[0164] L a b ΔE RAL8002 37.33 16.90 16.57 / Example 1 37.20 14.34 17.20 2.80 Example 2 36.44 15.34 17.02 1.85 Example 3 38.33 17.59 18.23 2.05 Comparative Example 1 40.35 14.36 17.33 3.33 Comparative Example 2 33.93 17.57 18.74 4.08 Comparative Example 3 40.95 18.25 17.58 3.99 Comparative Example 4 34.21 18.26 13.28 4.01 Comparative Example 5 40.35 18.23 20.33 4.37

[0165] As shown in Table 2 above, the ΔE values ​​of Examples 1, 2, and 3 compared to RAL8002 are all less than 3, and significantly lower than those of the comparative example. Optical photographs clearly demonstrate that the example masterbatches improve product color variation. Comparative Examples 1, 2, 3, and 4 adjust the type of dispersing aid while maintaining the same content. Comparative Example 5, while maintaining the same type and content of dispersing aid, exhibits significant color variation, making it difficult to address the product color variation issue.

[0166] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A brown masterbatch for PBT substrates that can improve product color difference, characterized in that: The raw material components include: Brown inorganic pigment: 238.5-241.5‰; Dispersing agent: 145.5~155.5‰; The balance is PBT; the total mass of the raw materials is 1000‰.

2. The brown masterbatch for improving product color difference for PBT substrate according to claim 1, characterized in that: The brown inorganic pigments include black pigment, inorganic zinc iron yellow and iron oxide red.

3. The brown masterbatch for improving product color difference for PBT substrate according to claim 2, characterized in that: The black pigment is carbon black.

4. The brown masterbatch for improving product color difference for PBT substrate according to claim 3, characterized in that: The proportions of each raw material component are as follows: Black pigment: 3.5~6.5‰; Inorganic zinc iron yellow: 83.5~86.5‰; Iron oxide red: 148.5~151.5‰; Dispersing agent: 145.5~155.5‰; The balance is PBT; the total mass of the raw materials is 1000‰.

5. The brown masterbatch for improving product color difference for PBT substrate according to any one of claims 1 to 4, characterized in that: The dispersing aid consists of maleic anhydride grafted polyethylene and ethylene-methyl acrylate.

6. The brown masterbatch for improving product color difference for PBT substrate according to claim 5, characterized in that: The maleic anhydride grafted polyethylene accounts for 95.5 to 100.5‰ of the total mass of the raw material components.

7. The brown masterbatch for improving product color difference for PBT substrate according to claim 6, characterized in that: The ethylene-methyl acrylate accounts for 50-55‰ of the total mass of the raw material components.

8. The brown masterbatch for improving product color difference for PBT substrate according to claim 7, characterized in that: The maleic anhydride grafted polyethylene accounts for 100.5‰ of the total mass of the raw material components, and the ethylene-methyl acrylate accounts for 55‰ of the total mass of the raw material components.

9. The method for preparing the brown masterbatch for PBT substrate capable of improving product color difference according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) brown inorganic pigment, dispersing aid and PBT are mixed according to proportion; (2) The mixed raw materials are melted and extruded in an extruder, cooled, and then granulated in a pelletizer to obtain brown masterbatch.

10. The method for preparing the brown masterbatch for PBT substrate capable of improving product color difference according to claim 9, characterized in that: The temperature of the melt extrusion is 230-250°C.

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