Coal gangue with low oil absorption value and preparation method thereof

Abstract

The invention discloses coal gangue with a low oil absorption value and a preparation method thereof, and belongs to the technical field of polymer composite material functional assistants, and the coal gangue is prepared from the following raw materials in parts by weight: 70-85 parts of coal gangue, 3-4 parts of palmitic acid, 2-4 parts of stearic acid, 2-5 parts of polyethylene wax, 3-7 parts of polypropylene wax and 5-10 parts of linear low density polyethylene powder. The preparation method comprises the following steps: mixing the raw materials, stirring, heating, and extruding in a single screw extruder after stirring to obtain the coal gangue with low oil absorption value. Through a multi-layer filling modification technology, the coal gangue is gradually filled and modified by the low-viscosity-high-viscosity auxiliary agent, and the modified coal gangue which is low in oil absorption value, low in gas displacement and high in compatibility is obtained. In addition, the raw materials are easy to obtain, and the preparation method is simple and convenient to popularize and apply.

Description

Technical Field

[0001] This invention belongs to the field of functional additives for polymer composite materials, and particularly relates to a low oil absorption value coal gangue and its preparation method. Background Technology

[0002] Coal gangue is a solid waste generated during coal mining and washing. It is a dark gray rock associated with coal seams during coal formation, with low carbon content (generally <20%) and a hardness higher than coal. Currently, the comprehensive utilization of coal gangue mainly involves its use as a raw material for traditional cement and concrete aggregates, or as a filling material for coal mine subsidence areas. For example, CN201811394537.5 discloses a new type of energy-saving and environmentally friendly wall material containing 10-15 parts of coal gangue; CN201510218909.9 discloses a highly elastic, cold-resistant thermoplastic rubber band and its preparation method, containing 5-7 parts of coal gangue powder. However, the application of coal gangue in the above-mentioned existing technologies suffers from low product added value and low application efficiency. Expanding the application scope of coal gangue can further promote its consumption and reduce the use of expensive carbon black. However, the main problems with the application of coal gangue in polymers are: its large internal specific surface area, high oil absorption value (>160mL / 100g), and the generation of a large amount of gas when heated; the large amount of carbon elements on the surface, low surface energy, and weak bonding force with the composite matrix, which greatly limit its appearance and performance as a color masterbatch filler in polymer products.

[0003] Current methods for solving the above problems mainly focus on matrix stiffness-toughness balance control (e.g., CN202210991845.6) and surface modification (e.g., CN201910939080.X), but still cannot solve the coal gangue exhaust problem, resulting in poor surface gloss, poor compatibility, and poor mechanical properties of composite materials under high filling amounts.

[0004] Therefore, how to provide a modified coal gangue with low oil absorption value, low exhaust volume, and high compatibility is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a low oil absorption value coal gangue and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A low oil absorption value coal gangue comprises the following raw materials in parts by weight: 70-85 parts coal gangue, 3-4 parts palmitic acid, 2-4 parts stearic acid, 2-5 parts polyethylene wax, 3-7 parts polypropylene wax, and 5-10 parts linear low-density polyethylene powder.

[0007] Preferably, the raw materials include the following parts by weight: 70 parts coal gangue, 4 parts palmitic acid, 4 parts stearic acid, 5 parts polyethylene wax, 7 parts polypropylene wax, and 10 parts linear low-density polyethylene powder.

[0008] Preferably, the particle size of the coal gangue is 800-1250 mesh.

[0009] Preferably, the linear low-density polyethylene powder has a particle size of 100-200 mesh and a melting point of 110-125℃.

[0010] Beneficial Effects: This invention utilizes the different melting points, hardnesses, and compatibility of palmitic acid, stearic acid, polyethylene wax, polypropylene wax, and linear low-density polyethylene to exert different functions within the powder. Specifically, palmitic acid has a melting point of 60-65℃, stearic acid 67-72℃, polyethylene wax 90-120℃, and polypropylene wax (PP wax) 155-165℃. Palmitic acid melts preferentially during heating, and its low viscosity ensures good wettability, making it easier to penetrate into the coal gangue and displace internal air. The high-melting-point polyethylene wax and polypropylene wax not only have high rigidity but also high compatibility with the composite resin matrix, significantly improving the interfacial compatibility of the composite material. Linear low-density polyethylene can coat the surface of the coal gangue, acting as a sealant and adhesive; its large molecular weight helps the coal gangue to agglomerate.

[0011] A method for preparing low oil absorption value coal gangue includes the following steps: The raw materials are mixed, stirred, and heated. After stirring, the mixture is fed into a single-screw extruder for extrusion to obtain the low oil absorption value coal gangue.

[0012] Preferably, the heating temperature is 125°C and the heating time is 10-30 minutes.

[0013] Preferably, the single-screw extruder rotates at a speed of 20 rpm.

[0014] Preferably, the extrusion temperature is 120-185°C.

[0015] Preferably, during the extrusion process, the temperatures of zones one through four of the single-screw extruder are 120°C, 150°C, 180°C, and 185°C, respectively.

[0016] Beneficial effects: After high-speed stirring modification, the above structure will not be fully formed. More of it requires extrusion, heating and compression by a single screw extruder. Therefore, the extrusion process is an important factor in the formation of the structure described in this invention.

[0017] Compared with the prior art, the present invention has the following advantages and technical effects: This invention utilizes a multi-layer filling modification technique, taking advantage of the differences in melting point, hardness, and compatibility of palmitic acid, stearic acid, polyethylene wax, polypropylene wax, and linear low-density polyethylene, to modify coal gangue through melt wetting, interface reinforcement, and surface coating. Simultaneously, a single-screw extrusion process is employed to form an effective structure through heating and compression, achieving a gradient filling modification of coal gangue with low-viscosity to high-viscosity additives, resulting in modified coal gangue with low oil absorption, low exhaust volume, and high compatibility. Furthermore, the raw materials provided by this invention are readily available, the preparation method is simple, and it is easy to promote and apply. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 These are photographs and microscopic images of the low oil absorption value coal gangue obtained in Example 5 of the present invention. Among them, (a) is a photograph of coal gangue, and (b) is the morphology of coal gangue under an optical microscope (magnification of 5x); Figure 2 This is a structural mechanism diagram of the low oil absorption value coal gangue obtained in this invention; Figure 3 The images are scanning electron microscope (SEM) images of the coal gangue raw material and the resulting low oil absorption value coal gangue in Example 1 of the present invention. Among them, (a)-(c) are coal gangue raw materials; (d)-(f) are coal gangue with low oil absorption value. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] This invention provides a low oil absorption value coal gangue, comprising the following raw materials in parts by weight: 70-85 parts coal gangue, 3-4 parts palmitic acid, 2-4 parts stearic acid, 2-5 parts polyethylene wax, 3-7 parts polypropylene wax, and 5-10 parts linear low-density polyethylene powder.

[0022] In a preferred embodiment, the low oil absorption value coal gangue comprises the following raw materials in parts by weight: 70 parts coal gangue, 4 parts palmitic acid, 4 parts stearic acid, 5 parts polyethylene wax, 7 parts polypropylene wax, and 10 parts linear low-density polyethylene powder.

[0023] In a preferred embodiment, the coal gangue has a particle size of 800-1250 mesh.

[0024] In a preferred embodiment, the linear low-density polyethylene powder has a particle size of 100-200 mesh and a melting point of 110-125°C.

[0025] This invention also provides a method for preparing low oil absorption value coal gangue, comprising the following steps: The raw materials are mixed, stirred, and heated. After stirring, the mixture is fed into a single-screw extruder for extrusion to obtain the low oil absorption value coal gangue.

[0026] In a preferred embodiment, the heating temperature is 125°C and the heating time is 10-30 minutes.

[0027] In a preferred embodiment, the single-screw extruder rotates at 20 rpm.

[0028] In a preferred embodiment, the extrusion temperature is 120-185°C.

[0029] In a preferred embodiment, during the extrusion process, the temperatures of zones one through four of the single-screw extruder are 120°C, 150°C, 180°C, and 185°C, respectively.

[0030] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels; The coal gangue was purchased from a coal mine base in Inner Mongolia. The polyethylene wax was purchased from Qingdao Sainuo New Materials Co., Ltd., with a softening point of 110-115℃ and a viscosity of 900-1200cps at 140℃. The polypropylene wax was purchased from Qingdao Sainuo New Materials Co., Ltd., with a softening point of 150-160℃ and a viscosity of 200-500 cps at 140℃. The linear low-density polyethylene powder was purchased from the Guangzhou branch of China Petroleum & Chemical Corporation, and its grade is 7042.

[0031] Unless otherwise specified, room temperature or normal temperature in the embodiments of the present invention refers to 25±3℃.

[0032] Example 1 A low oil absorption value coal gangue comprises the following raw materials in parts by weight: 85 parts coal gangue (800 mesh particle size), 3 parts palmitic acid, 3 parts stearic acid, 2 parts polyethylene wax, 3 parts polypropylene wax, and 5 parts linear low-density polyethylene powder (100 mesh particle size).

[0033] A method for preparing low oil absorption value coal gangue includes the following steps: After mixing the raw materials according to the above mass proportions, the mixture was added to a high-speed mixer and stirred, then gradually heated to 125℃ and held for 10 minutes. The resulting mixture was then removed and extruded in a single-screw extruder at a screw speed of 20 rpm. The temperatures in zones one through four were 120℃, 150℃, 180℃, and 185℃, respectively, to obtain low-oil-absorption coal gangue. The structural mechanism diagram of the obtained low-oil-absorption coal gangue is shown below. Figure 2 As shown, during the modification process, low-melting-point and high-flow-point additives first penetrate into the coal gangue. As the temperature gradually increases, medium-melting-point and moderately flow-point additives then penetrate into the coal gangue. Meanwhile, high-rigidity and high-melting-point additives such as polyethylene wax and polypropylene wax penetrate into the coal gangue last, or act as adhesives with LLDPE to agglomerate the coal gangue to a certain extent, thereby avoiding dust and reducing environmental pollution during transportation and processing.

[0034] Example 2 A low oil absorption value coal gangue comprises the following raw materials in parts by weight: 85 parts coal gangue (800 mesh particle size), 2 parts palmitic acid, 3 parts stearic acid, 3 parts polyethylene wax, 3 parts polypropylene wax, and 4 parts linear low-density polyethylene powder (100 mesh particle size).

[0035] A method for preparing low oil absorption value coal gangue includes the following steps: After mixing the raw materials according to the above mass proportions, they were put into a high-speed mixer and stirred, and the temperature was gradually raised to 125℃ and kept at 10 min. Then the resulting mixture was taken out and put into a single screw extruder for extrusion. The screw speed was 20 rpm, and the temperatures of the first to fourth zones were 120℃, 150℃, 180℃ and 185℃, respectively, to obtain coal gangue with low oil absorption value.

[0036] Example 3 A low oil absorption value coal gangue comprises the following raw materials in parts by weight: 80 parts coal gangue (800 mesh particle size), 3 parts palmitic acid, 3 parts stearic acid, 3 parts polyethylene wax, 4 parts polypropylene wax, and 7 parts linear low-density polyethylene powder (100 mesh particle size).

[0037] A method for preparing low oil absorption value coal gangue includes the following steps: After mixing the raw materials according to the above mass proportions, they were put into a high-speed mixer and stirred, and the temperature was gradually raised to 125℃ and kept at 10 min. Then the resulting mixture was taken out and put into a single screw extruder for extrusion. The screw speed was 20 rpm, and the temperatures of the first to fourth zones were 120℃, 150℃, 180℃ and 185℃, respectively, to obtain coal gangue with low oil absorption value.

[0038] Example 4 A low oil absorption value coal gangue comprises the following raw materials in parts by weight: 75 parts coal gangue (800 mesh particle size), 3 parts palmitic acid, 3 parts stearic acid, 4 parts polyethylene wax, 5 parts polypropylene wax, and 10 parts linear low-density polyethylene powder (100 mesh particle size).

[0039] A method for preparing low oil absorption value coal gangue includes the following steps: After mixing the raw materials according to the above mass proportions, they were put into a high-speed mixer and stirred, and the temperature was gradually raised to 125℃ and kept at 10 min. Then the resulting mixture was taken out and put into a single screw extruder for extrusion. The screw speed was 20 rpm, and the temperatures of the first to fourth zones were 120℃, 150℃, 180℃ and 185℃, respectively, to obtain coal gangue with low oil absorption value.

[0040] Example 5 A low oil absorption value coal gangue comprises the following raw materials in parts by weight: 70 parts coal gangue (800 mesh particle size), 4 parts palmitic acid, 4 parts stearic acid, 5 parts polyethylene wax, 7 parts polypropylene wax, and 10 parts linear low-density polyethylene powder (100 mesh particle size).

[0041] A method for preparing low oil absorption value coal gangue includes the following steps: After mixing the raw materials according to the above mass proportions, they were put into a high-speed mixer and stirred, and the temperature was gradually raised to 125℃ and kept at 10 min. Then the resulting mixture was taken out and put into a single screw extruder for extrusion. The screw speed was 20 rpm, and the temperatures of the first to fourth zones were 120℃, 150℃, 180℃ and 185℃, respectively, to obtain coal gangue with low oil absorption value.

[0042] Physical photographs and microscopic morphology of the obtained low oil absorption value coal gangue are as follows: Figure 1 As shown in the image, a is a photograph of coal gangue, and b is the morphology of coal gangue under an optical microscope (magnification of 5x). It can be seen that the modified coal gangue is in block form, bound together by the polymer.

[0043] Comparative Example 1 Use coal gangue with a particle size of less than 800 mesh.

[0044] Comparative Example 2 Use coal gangue with a particle size of less than 1250 mesh.

[0045] Comparative Example 3 A low oil absorption value coal gangue comprises the following raw materials in parts by weight: 89 parts coal gangue (800 mesh particle size), 3 parts palmitic acid, 3 parts stearic acid, 2 parts polyethylene wax and 3 parts polypropylene wax.

[0046] A method for preparing low oil absorption value coal gangue includes the following steps: After mixing the raw materials according to the above mass proportions, they were put into a high-speed mixer and stirred, and the temperature was gradually raised to 125℃ and kept at 10 min. Then the resulting mixture was taken out and put into a single screw extruder for extrusion. The screw speed was 20 rpm, and the temperatures of the first to fourth zones were 120℃, 150℃, 180℃ and 185℃, respectively, to obtain coal gangue with low oil absorption value.

[0047] Comparative Example 4 A low oil absorption value coal gangue comprises the following raw materials in parts by weight: 86 parts coal gangue (800 mesh), 3 parts palmitic acid, 3 parts stearic acid, 3 parts polypropylene wax, and 5 parts linear low-density polyethylene powder (100 mesh).

[0048] A method for preparing low oil absorption value coal gangue includes the following steps: After mixing the raw materials according to the above mass proportions, they were put into a high-speed mixer and stirred, and the temperature was gradually raised to 125℃ and kept at 10 min. Then the resulting mixture was taken out and put into a single screw extruder for extrusion. The screw speed was 20 rpm, and the temperatures of the first to fourth zones were 120℃, 150℃, 180℃ and 185℃, respectively, to obtain coal gangue with low oil absorption value.

[0049] Comparative Example 5 A low oil absorption value coal gangue comprises the following raw materials in parts by weight: 87 parts of coal gangue (800 mesh), 3 parts of palmitic acid, 2 parts of polyethylene wax, 3 parts of polypropylene wax, and 5 parts of linear low-density polyethylene powder (100 mesh).

[0050] A method for preparing low oil absorption value coal gangue includes the following steps: After mixing the raw materials according to the above mass proportions, they were put into a high-speed mixer and stirred, and the temperature was gradually raised to 125℃ and kept at 10 min. Then the resulting mixture was taken out and put into a single screw extruder for extrusion. The screw speed was 20 rpm, and the temperatures of the first to fourth zones were 120℃, 150℃, 180℃ and 185℃, respectively, to obtain coal gangue with low oil absorption value.

[0051] Comparative Example 6 A low oil absorption value coal gangue comprises the following raw materials in parts by weight: 91 parts coal gangue (800 mesh particle size), 3 parts palmitic acid, 3 parts stearic acid and 3 parts polypropylene wax.

[0052] A method for preparing low oil absorption value coal gangue includes the following steps: After mixing the raw materials according to the above mass proportions, they were put into a high-speed mixer and stirred, and the temperature was gradually raised to 125℃ and kept at 10 min. Then the resulting mixture was taken out and put into a single screw extruder for extrusion. The screw speed was 20 rpm, and the temperatures of the first to fourth zones were 120℃, 150℃, 180℃ and 185℃, respectively, to obtain coal gangue with low oil absorption value.

[0053] Comparative Example 7 A modified coal gangue, with the same raw materials and addition amounts as in Example 1.

[0054] A method for preparing modified coal gangue, differing from Example 1 only in that it does not include a single-screw extrusion step, and specifically includes the following steps: After mixing the raw materials according to the above mass proportions, put them into a high-speed mixer and stir, and gradually heat them to 125℃ and keep them at that temperature for 10 minutes. Then take out the resulting mixture to obtain modified coal gangue.

[0055] Comparative Example 8 A low oil absorption value coal gangue comprises the following raw materials in parts by weight: 70 parts coal gangue (800 mesh particle size), 4 parts palmitic acid, 4 parts stearic acid, 5 parts polyethylene wax, 7 parts polypropylene wax, and 10 parts linear low-density polyethylene powder (100 mesh particle size).

[0056] A method for preparing low oil absorption value coal gangue includes the following steps: After mixing the raw materials according to the above mass proportions, put them into a high-speed mixer and stir, and gradually heat them to 125℃ and keep them at that temperature for 10 minutes. Then take out the resulting mixture to obtain low oil absorption value coal gangue.

[0057] Technical effects: 1. Performance Characterization Figure 3 These are scanning electron microscope (SEM) images of the coal gangue raw material and the resulting low oil absorption value coal gangue in Example 1 of the present invention; wherein, (a)-(c) are the coal gangue raw material; (d)-(f) are the low oil absorption value coal gangue. It can be seen that the coal gangue raw material has a small particle size, a high surface roughness, and many pores, while the low oil absorption value coal gangue obtained after modification has an increased particle size (agglomerated by LLDPE) and polymer adhesion on the surface.

[0058] 2. The oil absorption value and torque of the coal gangue obtained in Examples 1-5 and Comparative Examples 1-8 were tested.

[0059] Oil absorption value test: 1g of coal gangue obtained in Examples 1-5 and Comparative Examples 1-8 were accurately weighed, and oil acid was added dropwise while stirring and the mixture was ground until a non-loose agglomerate was formed. The amount of oil consumed was recorded and the oil absorption value was calculated. Oil absorption value = amount of oil consumed (g) / mass of powder (g).

[0060] Torque test: 25g of coal gangue obtained in Examples 1-5 and Comparative Examples 1-8 were weighed and mixed with 25g of linear low-density polyethylene. The mixture was then placed in a torque converter and processed at 200℃ and 60rpm for 1min. The torque data were recorded.

[0061] The results are shown in Table 1.

[0062] Table 1 As shown in Table 1, the oil absorption value of the modified coal gangue in Examples 1-5 decreased significantly, and further decreased with increasing additive content, reaching a minimum of 85-87 g / g. Furthermore, the torque of the 50% filled masterbatch gradually decreased with increasing additive content, indicating optimized processing performance. Additionally, Comparative Example 8, which does not include a single-screw extrusion step, showed a significantly higher oil absorption value compared to Example 1, demonstrating that the extrusion process is indispensable in this invention.

[0063] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A low oil absorption value coal gangue, characterized in that, The ingredients include the following parts by weight: 70-85 parts coal gangue, 3-4 parts palmitic acid, 2-4 parts stearic acid, 2-5 parts polyethylene wax, 3-7 parts polypropylene wax, and 5-10 parts linear low-density polyethylene powder.

2. The low oil absorption value coal gangue according to claim 1, characterized in that, The ingredients include the following parts by weight: 70 parts coal gangue, 4 parts palmitic acid, 4 parts stearic acid, 5 parts polyethylene wax, 7 parts polypropylene wax, and 10 parts linear low-density polyethylene powder.

3. A low oil absorption value coal gangue according to claim 1 or 2, characterized in that, The particle size of the coal gangue is 800-1250 mesh.

4. A low oil absorption value coal gangue according to claim 1 or 2, characterized in that, The linear low-density polyethylene powder has a particle size of 100-200 mesh and a melting point of 110-125℃.

5. A method for preparing low oil absorption value coal gangue as described in any one of claims 1-4, characterized in that, Includes the following steps: The raw materials are mixed, stirred, and heated. After stirring, the mixture is fed into a single-screw extruder for extrusion to obtain the low oil absorption value coal gangue.

6. The preparation method according to claim 5, characterized in that, The heating temperature is 125℃ and the time is 10-30 minutes.

7. The preparation method according to claim 5, characterized in that, The single-screw extruder operates at a speed of 20 rpm.

8. The preparation method according to claim 5, characterized in that, The extrusion temperature is 120-185℃.

9. The preparation method according to claim 8, characterized in that, During the extrusion process, the temperatures of zones one through four of the single-screw extruder are 120°C, 150°C, 180°C, and 185°C, respectively.

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