Phosphogypsum-based cellulose composite material and preparation method thereof

Abstract

The invention discloses an ardealite-based cellulose composite material and a preparation method thereof, and belongs to the field of preparation of building materials from ardealite, and the preparation method comprises the following steps: pretreating washed-calcined ardealite, modifying cellulose, mixing the pretreated ardealite, the modified cellulose and an additive according to a mass ratio, and carrying out twin-screw extrusion blending granulation; and preparing the ardealite-based cellulose composite material product by adopting hot press molding. By optimizing raw material pretreatment, a compounding process and a forming technology, the physical and mechanical properties, weather resistance and functionality of the material are improved, so that the problem that large-scale resource recycling of ardealite is difficult is solved. All performance indexes of the product are superior to national standard requirements of light partition wall battens for buildings, the density is reduced by 20% compared with that of a traditional gypsum board, and the product has the characteristics of light weight and high strength.

Description

Technical Field

[0001] The present invention relates to the field of preparing building materials from phosphogypsum, and particularly to a phosphogypsum-based cellulose composite material and a preparation method thereof. Background Art

[0002] With the rapid development of the global phosphochemical industry, the annual discharge of phosphogypsum has been continuously increasing. Long-term stockpiled phosphogypsum not only occupies a large amount of land resources, but also poses environmental risks such as heavy metal pollution and leakage of acidic wastewater. At the same time, cellulose, as a renewable polymer material with abundant reserves in nature, has good biocompatibility, degradability and processability. The composite preparation of phosphogypsum and cellulose to form a new functional material can not only achieve the high-value utilization of phosphogypsum, but also expand the application field of cellulose materials, which is in line with the concept of circular economy and green development. Summary of the Invention

[0003] The purpose of this research is to develop a phosphogypsum-based cellulose composite material. By optimizing the pretreatment of raw materials, the composite process and the forming technology, the physical and mechanical properties, weather resistance and functionality of the material are improved to solve the problem of difficult large-scale resource reuse of phosphogypsum.

[0004] To achieve the above object, the present invention adopts the following technical scheme: A phosphogypsum-based cellulose composite material is prepared by mixing modified phosphogypsum: modified cellulose: mixed additives in a mass percentage ratio of 7:2:1.

[0005] Preferably, the modified phosphogypsum is prepared by dissolving phosphogypsum in an oxalic acid aqueous solution with a mass fraction of 3-5% at 30-45°C, stirring, placing it in an ultrasonic device for ultrasonic treatment for 25-35 min, then filtering, washing with water, and drying at 30-40°C.

[0006] Preferably, the cellulose is softwood or cotton linter, with a degree of polymerization of 1500-2000 and a purity of ≥98%.

[0007] Preferably, the cellulose is pretreated by alkalization with a sodium carbonate solution at 20-25°C for 2-3 hours, then ultrasonically cleaned and filtered at 30-40°C for 0.5-1 hour, and then neutralized with citric acid at 20-25°C for 0.5-1 hour, and finally dried and processed.

[0008] Preferably, the additive is compounded by a coupling agent, a lubricant and a binder in a mass ratio of 6-7:1-2:1-2.

[0009] Preferably, the selected silane coupling agent is one or two of vinyltrimethoxysilane or vinyltriethoxysilane powder, the lubricant is stearic acid, and the binder is a starch-based adhesive.

[0010] A preparation method of a phosphogypsum-based cellulose composite material, comprising the following steps:

[0011] Modification pretreatment of phosphogypsum: Using a combined process of water washing and calcination, after removing soluble impurities by water washing, calcine at 180 °C for 2 h to activate the crystal surface. The phosphogypsum is taken from a phosphochemical enterprise in Guizhou, and its main chemical component is CaSO4·2H2O (content ≥ 85%), containing a small amount of residual phosphoric acid, fluoride and heavy metal impurities;

[0012] Modification of cellulose: Immerse the cellulose in a 3% by mass KH-550 ethanol solution, stir at 60 °C for 2 h, and dry for later use;

[0013] Composite process: Mix the pretreated phosphogypsum, modified cellulose and additive according to the mass ratio, and granulate by co-mixing through a twin-screw extruder at 140 - 160 °C and a screw speed of 120 r / min;

[0014] Hot pressing and forming: Prepare a phosphogypsum-based cellulose composite material product by hot pressing and forming.

[0015] Preferably, the hot pressing and forming process is at a pressure of 12 - 18 MPa, a temperature of 100 - 150 °C, and a pressure holding time of 8 - 12 min.

[0016] The beneficial effects of the present invention are:

[0017] 1. Composite technology innovation: Propose a three-step method of "surface activation - interface modification - gradient composite", which solves the problem of poor compatibility between phosphogypsum and cellulose.

[0018] 2. Functional integration innovation: Achieve multi-functional integration such as light weight, high strength, heat preservation, and sound insulation, expanding the application scenarios of phosphogypsum-based materials. All performance indicators of the product are better than the requirements of the "Lightweight Partition Boards for Building Use" (GB / T 23449-2009) standard. The density is 20% lower than that of traditional gypsum boards, and it has the characteristics of light weight and high strength.

[0019] 3. Process optimization innovation: Develop a continuous production process with low energy consumption and short process flow, which is 30% more energy-efficient than the traditional process and the production efficiency is increased by 40%. This product can be widely used in fields such as building partitions, ceilings, and insulation boards, replacing traditional gypsum products and organic insulation materials, with high economic value. Specific embodiments

[0020] To further understand the content of the present invention, the present invention will be further described below in conjunction with embodiments.

[0021] Example 1

[0022] A preparation method of a phosphogypsum-based cellulose composite material comprises the following steps: Phosphogypsum pretreatment: A combined process of water washing and calcination is adopted. Phosphogypsum is dissolved in an oxalic acid aqueous solution with a mass fraction of 4% at 40°C, stirred, placed in an ultrasonic device for ultrasonic treatment for 30 minutes, then filtered, washed with water, and dried at 40°C. After removing soluble impurities by water washing, it is calcined at 180°C for 2 hours to activate the crystal surface. The cellulose is softwood or cotton linter, with a degree of polymerization of 1500 - 2000 and a purity of ≥98%. Cellulose modification: The cellulose is immersed in a KH-550 ethanol solution with a mass fraction of 3%, stirred at 60°C for 2 hours, alkalized and pretreated with a sodium carbonate solution at 25°C for 2 - 3 hours, then ultrasonically cleaned and filtered at 40°C for 1 hour, followed by neutralization treatment with citric acid at 25°C for 1 hour, and finally dried and processed for standby. Composite process: The pretreated phosphogypsum, modified cellulose, and additive are mixed according to a mass ratio of 7:2:1, and compounded and granulated by a twin-screw extruder at 150°C with a screw speed of 120 r / min. The additive is compounded from a coupling agent, a lubricant, and a binder according to a mass ratio of 7:2:1. The silane coupling agent is vinyltriethoxysilane powder, the lubricant is selected as stearic acid, and the binder is selected as a starch-based adhesive. Hot pressing and forming: The phosphogypsum-based cellulose composite material product is prepared by hot pressing and forming at a pressure of 15 MPa, a temperature of 120°C, and a pressure holding time of 10 minutes. Performance testing, compressive strength: 19 MPa, the standard requirement is ≥15 MPa; flexural strength: 4.5 MPa, the standard requirement is ≥3.5 MPa; density: 1.2 g / cm 3 , the standard requirement is ≤1.3 g / cm 3 ; water absorption rate 8.2%, the standard requirement is ≤10%; heat insulation performance: the thermal conductivity is 0.081 W / (m·K), which is 68% lower than that of ordinary concrete materials; sound insulation performance: in the frequency range of 100 - 4000 Hz, the average sound insulation amount reaches 34 dB, which can effectively block medium and low-frequency noise. Durability performance: After 20 freeze-thaw cycles, the mass loss rate of the specimen is <1.1%, and the strength retention rate is >96%; after soaking in an acidic solution with pH = 3 for 72 hours, there is no obvious corrosion on the surface, proving that the product has good weather resistance and chemical stability.

[0023] Example 2

[0024] A preparation method of a phosphogypsum-based cellulose composite material includes the following steps: Phosphogypsum pretreatment: A combined process of water washing and calcination is adopted. Phosphogypsum is dissolved in an oxalic acid aqueous solution with a mass fraction of 3% at 40°C, stirred, placed in an ultrasonic device for ultrasonic treatment for 30 minutes, then filtered, washed with water, and dried at 40°C. After removing soluble impurities by water washing, it is calcined at 180°C for 2 hours to activate the crystal surface. The cellulose is softwood or cotton linter, with a degree of polymerization of 1500 - 2000 and a purity of ≥98%. Cellulose modification: The cellulose is immersed in a KH-550 ethanol solution with a mass fraction of 3%, stirred at 60°C for 2 hours, alkalized and pretreated with a sodium carbonate solution at 25°C for 3 hours, then ultrasonically cleaned and filtered at 40°C for 1 hour, followed by neutralization treatment with citric acid at 25°C for 1 hour, and finally dried and processed for standby. Composite process: The pretreated phosphogypsum, modified cellulose, and additive are mixed according to a mass ratio of 7:2:1, and granulated by a twin-screw extruder at 140 - 160°C with a screw speed of 120 r / min. The additive is compounded from a coupling agent, a lubricant, and a binder according to a mass ratio of 6:2:2. The silane coupling agent is one or both of vinyltrimethoxysilane or vinyltriethoxysilane powder. The lubricant is selected as stearic acid, and the binder is selected as a starch-based adhesive. Hot pressing and forming: The phosphogypsum-based cellulose composite material product is prepared by hot pressing and forming at a pressure of 12 MPa, a temperature of 150°C, and a pressure holding time of 12 minutes. Performance testing, compressive strength: 18.5 MPa, the standard requirement is ≥15 MPa; flexural strength: 4.2 MPa, the standard requirement is ≥3.5 MPa; density: 1.25 g / cm 3 , the standard requirement is ≤1.3 g / cm 3 ; water absorption rate: 8.7%, the standard requirement is ≤10%; heat insulation performance: the thermal conductivity is 0.085 W / (m·K), which is 65% lower than that of ordinary concrete materials; sound insulation performance: in the frequency range of 100 - 4000 Hz, the average sound insulation amount reaches 32 dB, which can effectively block medium and low-frequency noise. Durability performance: After 20 freeze-thaw cycles, the mass loss rate of the specimen is <1.2%, and the strength retention rate is >95%; immersed in an acidic solution with pH = 3 for 72 hours, there is no obvious corrosion on the surface, proving that the product has good weather resistance and chemical stability.

[0025] Example 3

[0026] A preparation method of a phosphogypsum-based cellulose composite material comprises the following steps: Phosphogypsum pretreatment: A combined process of water washing and calcination is adopted. Phosphogypsum is dissolved in an oxalic acid aqueous solution with a mass fraction of 3% and a temperature of 35°C, stirred, placed in an ultrasonic device for ultrasonic treatment for 30 minutes, then filtered, washed with water, and dried at 30°C. After removing soluble impurities by water washing, it is calcined at 180°C for 2 hours to activate the crystal surface. The cellulose is softwood or cotton linter, with a degree of polymerization of 1500 - 2000 and a purity of ≥98%. Cellulose modification: The cellulose is immersed in a KH-550 ethanol solution with a mass fraction of 3%, stirred at 60°C for 2 hours, alkalized and pretreated with a sodium carbonate solution at 20°C for 2 hours, then ultrasonically cleaned and filtered at 40°C for 0.5 hours, followed by neutralization treatment with citric acid at 20°C for 0.5 hours, and finally dried and processed for standby. Composite process: The pretreated phosphogypsum, modified cellulose, and additive are mixed according to a mass ratio of 7:2:1, and granulated by a twin-screw extruder at 160°C with a screw speed of 120 r / min. The additive is compounded from a coupling agent, a lubricant, and a binder according to a mass ratio of 7:1:2. The silane coupling agent is vinyltrimethoxysilane, the lubricant is stearic acid, and the binder is a starch-based adhesive. Hot pressing and forming: A phosphogypsum-based cellulose composite material product is prepared by hot pressing and forming at a pressure of 15 MPa, a temperature of 100°C, and a pressure holding time of 12 minutes. Performance testing, compressive strength: 18.2 MPa, the standard requirement is ≥15 MPa; flexural strength: 4.1 MPa, the standard requirement is ≥3.5 MPa; density: 1.26 g / cm 3 , the standard requirement is ≤1.3 g / cm 3 ; water absorption rate: 8.8%, the standard requirement is ≤10%; heat insulation performance: the thermal conductivity is 0.083 W / (m·K), which is 65% lower than that of ordinary concrete materials; sound insulation performance: in the frequency range of 100 - 4000 Hz, the average sound insulation amount reaches 30 dB, which can effectively block medium and low-frequency noise. Durability performance: After 20 freeze-thaw cycles, the mass loss rate of the specimen is <1.2%, and the strength retention rate is >95%; after soaking in an acidic solution with pH = 3 for 72 hours, there is no obvious corrosion on the surface, proving that the product has good weather resistance and chemical stability.

[0027] The above is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A phosphogypsum-based cellulose composite material, characterized in that, It includes modified phosphogypsum, modified cellulose, and a mixed additive prepared by mixing them in a ratio of 7:2:1 by mass percentage.

2. The phosphogypsum-based cellulose composite material according to claim 1, wherein The modified phosphogypsum is prepared by dissolving phosphogypsum in an oxalic acid aqueous solution with a mass fraction of 3-5% at 30-45°C, stirring, placing it in an ultrasonic device for ultrasonic treatment for 25-35 min, then filtering, washing with water, and drying at 30-40°C.

3. The phosphogypsum-based cellulose composite material according to claim 1, wherein The cellulose is softwood or cotton linter, with a degree of polymerization of 1500-2000 and a purity of ≥98%.

4. The phosphogypsum-based cellulose composite material according to claim 3, characterized in that, The cellulose is pretreated by alkalization with a sodium carbonate solution at 20-25°C for 2-3 hours, then ultrasonically cleaned and filtered at 30-40°C for 0.5-1 hour, and then neutralized with citric acid at 20-25°C for 0.5-1 hour, and finally dried and processed.

5. The phosphogypsum-based cellulose composite material according to claim 1, wherein The additive is compounded by a coupling agent, a lubricant, and a binder in a mass ratio of 6-7:1-2:1-2.

6. The phosphogypsum-based cellulose composite material according to claim 4, wherein The selected silane coupling agent is one or two of vinyltrimethoxysilane or vinyltriethoxysilane powder, the lubricant is stearic acid, and the binder is a starch-based adhesive.

7. The preparation method of a phosphogypsum-based cellulose composite material according to claim 1, characterized in that, It includes the following steps: Phosphogypsum pretreatment: Adopt a combined process of water washing and calcination. After removing soluble impurities by water washing, calcine at 180°C for 2 h to activate the crystal surface. Cellulose modification: Immerse the cellulose in a KH-550 ethanol solution with a mass fraction of 3%, stir at 60°C for 2 h, and dry for later use. Compound process: Mix the pretreated phosphogypsum, modified cellulose, and additive according to the mass ratio, and compound and granulate them by a twin-screw extruder at 140-160°C with a screw speed of 120 r / min. Hot pressing and forming: Prepare a phosphogypsum-based cellulose composite product by hot pressing and forming.

8. The preparation method of a phosphogypsum-based cellulose composite material according to claim 1, characterized in that, The hot pressing and forming process is at a pressure of 12-18 MPa, a temperature of 100-150°C, and a pressure holding time of 8-12 min.