Composite polymer materials based on modified phosphogypsum and their preparation methods

Abstract

This invention discloses a composite polymer material based on modified phosphogypsum and its preparation method. The composite polymer material includes a polymer matrix, ettringite, TPU compatibilizer, plasticizer, calcium-zinc stabilizer, and PE wax. The preparation method includes the preparation of the TPU compatibilizer, the preparation of ettringite, the mixing and dehydration of the polymer matrix / ettringite, the mixing and preparation of the composite polymer, and granulation. This invention produces ettringite through modification of phosphogypsum. Utilizing the synergistic effect of ettringite with the polymer matrix and TPU compatibilizer, the tensile strength, flexural strength, and other mechanical properties of the material are significantly improved while ensuring good processing fluidity. ettringite improves the rigidity of the material, while the TPU compatibilizer improves the compatibility between ettringite and the polymer matrix, and enhances the toughness and impact resistance of the material. This enables the large-scale utilization of phosphogypsum while avoiding the problem of hydrophilic aging of phosphogypsum in existing phosphogypsum-based polymer composites.

Description

Technical Field

[0001] This invention relates to the field of solid waste and polymer blending application technology, and particularly to composite polymer materials based on modified phosphogypsum and their preparation methods. Background Technology

[0002] Phosphogypsum is a solid waste generated during the wet-process phosphoric acid production process.

[0003] According to the "Action Plan for Comprehensive Utilization of Phosphogypsum", efforts will be made to promote the production of roadbed materials such as water-stabilized base course materials, roadbed fillers, roadbed reinforcement materials, slope greening spraying materials, cemented slope protection materials, sound barriers, filling materials, soil improvement and ecological restoration materials, etc., using phosphogypsum as raw material.

[0004] Currently, the application of phosphogypsum powder as a filler in polymer materials faces several problems, including poor compatibility between phosphogypsum and PVC leading to substandard mechanical properties of phosphogypsum composite polymer materials, and acidic impurities in phosphogypsum causing corrosion of molds by phosphogypsum composite polymer materials.

[0005] In addition, phosphogypsum is prone to hydration, and may even leach soluble phosphorus and soluble fluorine. During the hydration process, eutectic phosphorus precipitates from the crystal lattice and becomes soluble HPO42-. The PO43- ionized from HPO42- combines with Ca2+ in the solution to form insoluble Ca3(PO4)2. The insoluble calcium phosphate covers the surface of the crystal, hindering further hydration of the gypsum and causing a decrease in gypsum strength. When used underwater for a long time (such as polymer / phosphogypsum composite pipes used as sewage pipes), the surface of the polymer / phosphogypsum composite material may also show powdering and blooming, reducing strength and eventually causing irreversible aging or even cracking. Improvements are urgently needed. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a composite polymer material based on modified phosphogypsum and its preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention first proposes a composite polymer material based on modified phosphogypsum, comprising the following components in parts by weight:

[0009] 100 parts of polymer substrate: PVC, PP or PE;

[0010] 20-40 parts of ettringite: prepared by mixing and reacting phosphogypsum, calcium oxide, calcium aluminate (CA) and pure water;

[0011] 20-30 parts of TPU compatibilizer;

[0012] 15-20 parts plasticizer;

[0013] 1-3 parts calcium-zinc stabilizer;

[0014] 1.2-2.5 parts of PE wax;

[0015] The preparation process of the TPU compatibilizer is as follows:

[0016] 1) Preparation of polyurethane prepolymer: After polybutylene adipate melts at 110℃, it is sealed and stirred, and dehydrated under vacuum for 2 hours. Heating is stopped and vacuum is maintained. When the reaction temperature drops to 80℃, the vacuum pump is turned off and nitrogen gas is introduced into the reaction flask. Isophorone diisocyanate and dibutyltin dilaurate are added dropwise, and the reaction is carried out at 80℃ for 3 hours to obtain a clear polyurethane prepolymer (i.e., IP-PBA). The reaction formula is as follows:

[0017]

[0018] 2) Preparation of polyurethane elastomer: After the prepolymerization reaction is completed, 4,4-diaminodiphenylmethane is added under nitrogen protection, and after mixing, the chain extension reaction is carried out at 80°C for 2 hours.

[0019] 3) Crosslinking preparation of TPU compatibilizer: Stop heating the reaction solution obtained in 2), add acetone solution with a concentration of 0.03 g / ml boric acid, stir and mix, pour the resulting mixture into a polytetrafluoroethylene mold, heat to 80℃ and seal to cure for 10 h, cool to room temperature, remove from the mold, and obtain TPU compatibilizer containing acetone (i.e., IP-PBA-BA).

[0020] The cross-linking reaction is shown in the following formula:

[0021]

[0022] By prepolymerizing the terminal hydroxyl groups of polybutylene adipate with the terminal isocyanate groups of isophorone diisocyanate, and then extending the chain with diamine, a thermoplastic polyurethane elastomer with terminal isocyanate groups is formed. Then, by crosslinking boric acid with the terminal isocyanate groups of the thermoplastic polyurethane elastomer, an acetone gel with self-healing borate ester groups is obtained. After the borate ester groups break, they quickly repair the crosslinked network upon contact with water and block further penetration of water molecules, thereby avoiding the destructive effects of water penetration.

[0023] Preferably, in the preparation of the TPU compatibilizer, the molar ratio of polybutylene adipate, isophorone diisocyanate, dibutyltin dilaurate, 4,4-diaminodiphenylmethane and boric acid is approximately 1:2:0.0016:0.48:0.49.

[0024] Preferably, the 4,4-diaminodiphenylmethane added in step 2) is specifically an acetone solution of 4,4-diaminodiphenylmethane with a concentration of 0.2 g / ml.

[0025] Preferably, the boric acid added in step 3) is an acetone solution with a concentration of 0.03 g / ml boric acid, and the resulting TPU compatibilizer contains acetone.

[0026] Preferably, the preparation process of ettringite is as follows:

[0027] Phosphogypsum (a solid waste product from a nearby wet-process phosphoric acid plant, containing 82.1% calcium sulfate dihydrate CaSO4·2H2O and 5.4% free water), calcium oxide (98% purity, Langfang Qianyao Technology Co., Ltd.), and pure water were mixed in a weight ratio of 5:1:5. Calcium aluminate (CA) (amorphous calcium aluminate, 200-250 mesh, purity >99%, light gray-green granular powder, Zhengzhou Shengbowei New Material Co., Ltd., smelted in an electric furnace using high-quality bauxite and lime in a certain proportion; amorphous calcium aluminate has higher reactivity than crystalline products, achieving higher reactivity and efficiency) was added. The molar ratio of CA to CaO was controlled at 1:2.05-2.1, and the mixture was stirred at 500 r / min for 2 hours to obtain ettringite. CaO is used in slight excess. Furthermore, based on the molar ratio of CaSO4·2H2O:CaO:H2O = 3:2:24, both phosphogypsum and pure water are used in excess, with phosphogypsum in approximately 13% excess.

[0028] In the presence of CaSO4 and CaO, CA generates the main product of the swelling agent—ettringite C3A·3CaSO4·32H2O, as shown in the following reaction formula:

[0029] CA+3CaSO4+2CaO+32H20=C3A·3CaS04·32H2O;

[0030] The exothermic reaction of quicklime (CaO) and water is used to rapidly hydrate CaO, producing highly expandable and fully hydrated ettringite.

[0031] This invention also proposes a method for preparing the aforementioned composite polymer material based on modified phosphogypsum, comprising the following steps:

[0032] S1. Mixing and dehydration of polymer substrate / ettringite:

[0033] The polymer substrate and ettringite were mixed and then fed into an internal mixer. The temperature was raised to 130°C within 30 minutes and the mixture was stirred at 130°C for 1 hour. The temperature was then rapidly raised to 185°C and stirred at 185°C for 2 hours. At the high temperature of 185°C, most of the water of crystallization in the ettringite was removed (possibly leaving 4-6 molecules of water of crystallization), resulting in a polymer substrate / ettringite mixture with a moisture content of 3.57%.

[0034] According to previous research, during the dehydration process, ettringite gradually decreases in volume. Under the action of intensive mixing, the polymer substrate softens and gradually penetrates into the dehydration sites, forming a fully and uniformly distributed polymer phase and inorganic phase.

[0035] When exposed to temperatures below 200°C for an extended period, ettringite gradually dehydrates, leaving only 4-6 molecules of water of crystallization. At this point, the crystal lattice transforms, and the volume collapses and shrinks. Studies have shown that when reacting at temperatures above 200°C for an extended period (generally about one day), the hydrated layers of ettringite completely lose water, and the crystals transform into a more disordered state, eventually forming a structure that no longer exhibits the characteristics of hydrated minerals. This transformation leads to the disintegration of the crystals, greatly weakening the stability of the entire crystal structure and potentially causing a sharp decline in its physical strength.

[0036] S2. Preparation of composite polymers through compounding:

[0037] TPU compatibilizer was added to the polymer matrix / ettringite obtained in S1, and the mixture was continuously intensively mixed at 185°C for 3 hours to obtain a composite polymer. Acetone was evaporated and excess water of crystallization was removed by azeotropic distillation. At 185°C, the borate ester bonds in the TPU compatibilizer were broken. However, due to the presence of water of crystallization in the vicinity of the ettringite, the repair of the borate ester bonds was rapidly promoted. This caused the crosslinking network nodes of the TPU elastomer to move closer to the ettringite. At the same time, the molecular chains of the TPU elastomer that were dissociated from crosslinking became entangled with the polymer matrix, further expanding the entanglement and uniform distribution of the organic and inorganic phases, thereby improving the overall structural strength.

[0038] S3, Granulation:

[0039] The composite polymer, plasticizer, PE wax, and calcium-zinc stabilizer are placed in a high-speed and low-speed mixer in a certain proportion and stirred and mixed. The mixing speed is 1500 r / min for 15 min and 500 r / min for 10 min. The mixture is then fed into a twin-screw extruder for extrusion and granulation. The temperature of the twin-screw extruder is 120℃-170℃, the feeding frequency is 20-25 Hz, the main extruder speed is 80-100 r / min, and a 100-mesh filter is added to the die head. After hot cutting, cooling by a fan, conveying, and packaging, the finished composite polymer material is obtained.

[0040] Preferably, the ettringite in S1 is ground and sieved through a 150-mesh sieve before use.

[0041] Preferably, volatile gases are emitted during the internal mixing process of S1. These volatile gases are collected and filtered by alkaline solution. The volatile gases are mainly water vapor, CO2, HCl and HF, which are residual acidic substances in the system.

[0042] Preferably, volatile gases are emitted during the mixing process of S2. These volatile gases are collected by condensation and are mainly acetone and trace amounts of water. After being collected and filtered with alkaline solution, the volatile gases are mainly water vapor, CO2, HCl and HF, which are residual acidic substances in the system.

[0043] Preferably, the temperature of the twin-screw extruder in S4 is set in the following ways: When the polymer substrate is PVC or PP, the temperature of the feeding zone of the twin-screw extruder is 50-60℃, the temperature of the melting and plasticizing zone is 160℃-170℃, and the temperature of the die head is 190℃-200℃.

[0044] When the polymer substrate is PE, the feed zone temperature of the screw extruder is 40-50℃, the melt plasticizing zone temperature is 120℃-130℃, and the die head temperature is 160℃-170℃.

[0045] Compared with the prior art, the beneficial effects of the present invention are:

[0046] 1. This invention first utilizes phosphogypsum, a solid waste from wet-process phosphoric acid plants, by converting it into ettringite and applying it to composite polymer materials. This fixes the free phosphorus and fluoride ions in the phosphogypsum, enabling large-scale utilization of phosphogypsum, reducing the land resources occupied by phosphogypsum stockpiling and the risk of environmental pollution, and has significant environmental and economic benefits. At the same time, it overcomes the problem of phosphogypsum's easy hydrophilic aging in existing phosphogypsum-based polymer composite materials.

[0047] 2. This invention prepares a TPU compatibilizer based on borate ester self-crosslinking. Through intensive mixing, the water-repairing properties of borate ester and the crystal water on the surface of ettringite are utilized to bring the crosslinking network nodes of the TPU elastomer closer to ettringite. At the same time, the molecular chains of the TPU elastomer that have dissociated from crosslinking become entangled with the polymer matrix, further expanding the entanglement and uniform distribution of the organic and inorganic phases, thereby improving the overall structural strength. In addition, the borate ester groups can quickly repair the crosslinking network after breakage when exposed to water, which can prevent further penetration of water molecules, thereby effectively avoiding damage to the material caused by water penetration and improving the water resistance of the material.

[0048] 3. Through the synergistic effect of the polymer substrate and components such as ettringite and TPU compatibilizer, the mechanical properties of the material, such as tensile strength and flexural strength, are significantly improved while ensuring good processing fluidity. The addition of ettringite improves the rigidity of the material, while the TPU compatibilizer enhances the toughness and impact resistance of the material.

[0049] Meanwhile, the synergistic effect of ettringite and TPU compatibilizer enables the material to maintain good structural stability at high temperatures and is not prone to thermal decomposition or deformation; in addition, the alumina in ettringite has a certain flame retardant effect.

[0050] 4. In summary, the product of this invention can be used as a pipe material in aquatic environments, such as sewage pipes, and as a pipe material in fields such as power and communication pipes that require waterproofing. Detailed Implementation

[0051] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0052] I. Formulation screening of composite polymer materials based on modified phosphogypsum:

[0053] The composite polymer material based on modified phosphogypsum comprises the following components in parts by weight:

[0054] 100 parts of polymer substrate: PVC, PP or PE;

[0055] 20-40 parts of ettringite: prepared by mixing and reacting phosphogypsum, calcium oxide, calcium aluminate (CA) and pure water;

[0056] 20-30 parts of TPU compatibilizer;

[0057] 15-20 parts of plasticizer (V-276 plasticizer, Wuxi Jiasheng High-tech Modified Materials);

[0058] 1-3 parts of calcium-zinc stabilizer (calcium-zinc composite stabilizer A-310, Mizusawa, Japan);

[0059] 1.2-2.5 parts of PE wax (Honeywell polyethylene wax A-C6A, as a lubricant).

[0060] Preparation Example 1:

[0061] Reference: Preparation and properties of self-healing polyurethane elastomers based on multiple reversible effects, Sheng Yeming et al., Journal of Chemistry of Chinese Universities, 3-41, 2020.03, 275-281.

[0062] Reagents used: Polybutylene adipate (PBA-2000, industrial grade, Shandong Jining Huakai Resin Co., Ltd.); Boric acid (BA), trimethylolpropane (TMP), isophorone diisocyanate (IPDI), 4,4-diaminodiphenylmethane (MDA), and dibutyltin dilaurate (DBTDL), all analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.; Acetone, analytical grade, Guangzhou Chemical Reagent Factory.

[0063] The preparation process of the TPU compatibilizer is as follows:

[0064] 1) Preparation of polyurethane prepolymer: After polybutylene adipate melts at 110℃, it is sealed and stirred, and dehydrated under vacuum for 2 hours. Heating is stopped and vacuum is maintained. When the reaction temperature drops to 80℃, the vacuum pump is turned off and nitrogen is introduced into the reaction flask. Isophorone diisocyanate and dibutyltin dilaurate are added dropwise. The reaction is carried out at 80℃ for 3 hours to obtain a clear polyurethane prepolymer.

[0065] 2) Preparation of polyurethane elastomer: After the prepolymerization reaction is completed, under nitrogen protection, an acetone solution of 4,4-diaminodiphenylmethane with a concentration of 0.2 g / ml is added, mixed, and then the chain extension reaction is carried out at 80°C for 2 h.

[0066] 3) Crosslinking preparation of TPU compatibilizer: Stop heating the reaction solution obtained in 2), add acetone solution with a concentration of 0.03 g / ml boric acid, stir and mix, pour the resulting mixture into a polytetrafluoroethylene mold, heat to 80℃ and seal to cure for 10 h, cool to room temperature, remove from the mold, and obtain TPU compatibilizer containing acetone (i.e., IP-PBA-BA).

[0067] By prepolymerizing the terminal hydroxyl groups of polybutylene adipate with the terminal isocyanate groups of isophorone diisocyanate, and then extending the chain with diamine, a thermoplastic polyurethane elastomer with terminal isocyanate groups is formed. Then, by crosslinking boric acid with the terminal isocyanate groups of the thermoplastic polyurethane elastomer, an acetone gel with self-healing borate ester groups is obtained. After the borate ester groups break, they quickly repair the crosslinked network upon contact with water and block further penetration of water molecules, thereby avoiding the destructive effects of water penetration.

[0068] In the preparation of the above TPU compatibilizer, the molar ratio of polybutylene adipate, isophorone diisocyanate, dibutyltin dilaurate, 4,4-diaminodiphenylmethane and boric acid is approximately 1:2:0.0016:0.48:0.49.

[0069] Comparative preparation example 1:

[0070] The preparation process is as follows: A polyurethane elastomer is used instead of the TPU compatibilizer obtained in Preparation Example 1, and mixed into a composite polymer material based on modified phosphogypsum.

[0071] 1) Preparation of polyurethane prepolymer: After polybutylene adipate melts at 110℃, it is sealed and stirred, and dehydrated under vacuum for 2 hours. Heating is stopped and vacuum is maintained. When the reaction temperature drops to 80℃, the vacuum pump is turned off and nitrogen is introduced into the reaction flask. Isophorone diisocyanate and dibutyltin dilaurate are added dropwise. The reaction is carried out at 80℃ for 3 hours to obtain a clear polyurethane prepolymer.

[0072] 2) Preparation of polyurethane elastomer: After the prepolymerization reaction is completed, under nitrogen protection, an acetone solution of 4,4-diaminodiphenylmethane with a concentration of 0.2 g / ml is added. After mixing, the chain extension reaction is carried out at 80℃ for 2 h. After evaporation and drying, the mixture is pulverized to 150 mesh to obtain polyurethane elastomer.

[0073] Preparation Example 2:

[0074] The preparation process of ettringite is as follows:

[0075] Reference: Development of a High-Efficiency Expansive Agent for Concrete Using Phosphogypsum (Unpublished), Wang Yong;

[0076] Phosphogypsum (a solid waste product from a nearby wet-process phosphoric acid plant, containing 82.1% calcium sulfate dihydrate CaSO4·2H2O and 5.4% free water), calcium oxide (98% purity, Langfang Qianyao Technology Co., Ltd.), and pure water were mixed in a weight ratio of 5:1:5. Calcium aluminate (CA, non-crystalline calcium aluminate, 200-250 mesh, purity >99%, light gray-green granular powder, Zhengzhou Shengbowei New Materials Co., Ltd.) was then added. High-quality bauxite and lime were mixed in a... It is smelted in a fixed proportion in an electric furnace. The non-crystalline calcium aluminate has higher reactivity than the crystalline product, achieving higher reactivity and efficiency. The molar ratio of CA to CaO is controlled at 1:2.05-2.1, and the reaction is stirred at 500 r / min for 2 hours to obtain ettringite. CaO is slightly in excess. In addition, according to the molar ratio CaSO4·2H2O:CaO:H2O=3:2:24, phosphogypsum and pure water are used in excess, with phosphogypsum in excess by about 13%.

[0077] In the presence of CaSO4 and CaO, CA generates ettringite (C3A·3CaSO4·32H2O), the main product of the expanding agent. The exothermic reaction of quicklime (CaO) and water is used to rapidly hydrate CA, producing highly expandable and fully hydrated ettringite.

[0078] Comparative preparation example 2:

[0079] Modified phosphogypsum was obtained by mixing phosphogypsum (a solid waste product from a nearby wet-process phosphoric acid plant, containing 82.1% calcium sulfate dihydrate CaSO4·2H2O and 5.4% free water) and calcium oxide (98% purity, from Langfang Qianyao Technology Co., Ltd.) at a weight ratio of 5:1, controlling the temperature at 110℃-130℃, and reacting for 0.5-1 hours.

[0080] Comparative preparation example 3:

[0081] The phosphogypsum (a solid waste from a nearby wet-process phosphoric acid plant, containing 82.1% calcium sulfate dihydrate CaSO4·2H2O and 5.4% free water) was dehydrated at 120°C for 1 hour and then used to replace the ettringite obtained in Example 2, and was mixed into the composite polymer material based on the modified phosphogypsum.

[0082] II. Preparation of Composite Polymer Materials: Example Group:

[0083] S1. Mixing and dehydration of polymer substrate / ettringite:

[0084] Before use, ettringite is ground and sieved through a 150-mesh sieve. The polymer matrix and ettringite are mixed and then fed into an internal mixer. The temperature is raised to 130℃ within 30 minutes and the mixture is stirred at 130℃ for 1 hour. The temperature is then rapidly raised to 185℃ and stirred at 185℃ for 2 hours. At the high temperature of 185℃, most of the water of crystallization in the ettringite is removed (possibly leaving 4-6 molecules of water of crystallization), resulting in a polymer matrix / ettringite mixture with a moisture content of 3.57%.

[0085] According to previous research, during the dehydration process, ettringite gradually decreases in volume. Under the action of intensive mixing, the polymer substrate softens and gradually penetrates into the dehydration sites, forming a fully and uniformly distributed polymer phase and inorganic phase.

[0086] Tests were conducted to ensure uniform distribution of the polymer substrate / ettringite.

[0087] 1) Take a polymer substrate / ettling stone and make a cube with a side length of 1cm in a mold. After cooling and molding, place it in dichloromethane at 60℃ and dissolve it completely for 1h to obtain a porous block similar to an ant hole. The porosity of the porous block is as high as 75.4%, indicating that the ettling stone is uniformly distributed in the polymer network in a network.

[0088] 2) When the same polymer matrix / phosphogypsum composite material is fully dissolved in dichloromethane at 60°C for 1 hour, only particles are obtained, indicating that phosphogypsum is distributed in the polymer network in a granular form. When the amount of phosphogypsum is increased to the same as that of the polymer matrix, it can be distributed in the polymer network in a network form. However, the composite material at this time has poor water resistance and aging resistance.

[0089] S2. Preparation of composite polymers through compounding:

[0090] TPU compatibilizer was added to the polymer matrix / ettringite obtained in S1, and the mixture was continuously intensively mixed at 185°C for 3 hours to obtain a composite polymer. Acetone was evaporated and excess water of crystallization was removed by azeotropic distillation. At 185°C, the borate ester bonds in the TPU compatibilizer were broken. However, due to the presence of water of crystallization in the vicinity of the ettringite, the repair of the borate ester bonds was rapidly promoted. This caused the crosslinking network nodes of the TPU elastomer to move closer to the ettringite. At the same time, the molecular chains of the TPU elastomer that were dissociated from crosslinking became entangled with the polymer matrix, further expanding the entanglement and uniform distribution of the organic and inorganic phases, thereby improving the overall structural strength.

[0091] Set up a sedimentation test for ettringite modified with TPU elastomer:

[0092] 1) Blank test: only ettringite, which settled immediately after stirring;

[0093] 2) Comparative test: Electret was intensively mixed at 130℃ for 1 hour, then heated to 185℃ and intensively mixed for 2 hours. TPU compatibilizer was added, and TPU compatibilizer and ettringite were mixed at a weight ratio of 1:1. The mixture was intensively mixed at 185℃ for 3 hours. The resulting mixture was dissolved in acetone solution for 30 minutes, filtered, and rinsed three times with acetone. The filter residue was then added to acetone. The sedimentation time was tested to be more than 12 hours (sediment was generally found after one day, suspended matter and sediment each accounted for a portion after two days, and complete sedimentation was achieved after 5 days, indicating that the bonding was a relatively weak hydrogen bond or ionic bond structure). This was significantly better than the blank test, indicating that water of crystallization is conducive to the approach of the cross-linking nodes—boronic acid esters—in the TPU compatibilizer.

[0094] S3, Granulation:

[0095] The composite polymer, plasticizer, PE wax, and calcium-zinc stabilizer are placed in a high-speed and low-speed mixer in a certain proportion and stirred and mixed. The mixing speed is 1500 r / min for 15 min and 500 r / min for 10 min. The mixture is then fed into a twin-screw extruder for extrusion granulation. The twin-screw extruder temperature is 120℃-170℃, the feeding frequency is 20-25 Hz, the main extruder speed is 80-100 r / min, and a 100-mesh filter is added to the die head. After hot cutting, cooling by a fan, conveying, and packaging, the finished composite polymer material is obtained.

[0096] The temperature of the twin-screw extruder is set in the following ways: When the polymer substrate is PVC or PP, the temperature of the feeding zone of the twin-screw extruder is 50-60℃, the temperature of the melting and plasticizing zone is 160℃-170℃, and the temperature of the die head is 190℃-200℃.

[0097] When the polymer substrate is PE, the feed zone temperature of the screw extruder is 40-50℃, the melt plasticizing zone temperature is 120℃-130℃, and the die head temperature is 160℃-170℃.

[0098] Detection and treatment of volatile matter in internal mixing:

[0099] 1) Volatile gases emitted during the internal mixing process of S1: The volatile gases are collected and filtered by alkaline solution. The volatile gases are mainly water vapor, CO2, HCl and HF, which are residual acidic substances in the system.

[0100] 2) Volatile gases emitted during the mixing process of S2: The volatile gases are collected by condensation, mainly consisting of acetone and trace amounts of water. After collection and filtration with alkaline solution, the volatile gases are mainly water vapor, CO2, HCl and HF, which are residual acidic substances in the system.

[0101] The formulations of each embodiment and comparative example are shown in Table 1 below:

[0102] Table 1. Formulation of composite polymer materials with modified phosphogypsum

[0103]

[0104] It should be noted that the PVC in Table 1 was purchased from Foshan Xianghu New Material Co., Ltd. (XH-BY11 type injection molding PVC granules), the PP was purchased from Dongguan Shengli New Material Co., Ltd. (SH-8535 type injection molding PP granules), the PE was purchased from Zibo Aole Plastics Co., Ltd. (TR480 type PE granules), the plasticizer (V-276 plasticizer, Wuxi Jiasheng High-tech Modified Materials), the calcium-zinc stabilizer (industrial grade calcium-zinc stabilizer, 99% content, light yellow liquid, Shandong Yueyang New Material Co., Ltd., labeled as: composite heat stabilizer for PVC plastic pipes), and the PE wax (Honeywell polyethylene wax A-C6A, as a lubricant).

[0105] Meanwhile, to verify the effects of ettringite and TPU compatibilizer, a comparative example 9 was set up as uncomposite PVC particles for comparison.

[0106] In addition, to verify the correctness of the process, the following comparative experiments were set up:

[0107] Comparative Example 10:

[0108] The formulations of each component are the same as in Example 2, except for the operational differences, as detailed below:

[0109] S1. Mixing and dehydration of polymer substrate / ettringite:

[0110] Before use, ettringite is ground and sieved through a 150-mesh sieve. The polymer matrix and ettringite are mixed and then fed into an internal mixer. The temperature is raised to 130°C within 30 minutes, and the mixture is kneaded at 130°C for 3 hours to obtain the polymer matrix / ettringite mixture. The moisture content is 13.15%.

[0111] S2. Preparation of composite polymers through compounding:

[0112] The TPU compatibilizer was added to the polymer substrate / ettringite obtained in S1, and the mixture was continuously kneaded at 185°C for 3 hours to obtain the composite polymer.

[0113] S3, Granulation:

[0114] The composite polymer, plasticizer, PE wax, and calcium-zinc stabilizer are placed in a high-speed and low-speed mixer in a certain proportion and stirred and mixed. The mixing speed is 1500 r / min for 15 min and 500 r / min for 10 min. The mixture is then fed into a twin-screw extruder for extrusion granulation. The twin-screw extruder temperature is 160℃-170℃, the feeding frequency is 20-25 Hz, the main extruder speed is 80-100 r / min, and a 100-mesh filter is added to the die head. After hot cutting, cooling by a fan, conveying, and packaging, the finished composite polymer material is obtained.

[0115] Comparative Example 11:

[0116] The formulations of each component are the same as in Example 2, except for the operational differences, as detailed below:

[0117] S1. Mixing and dehydration of polymer substrate / ettringite:

[0118] Before use, ettringite is ground and sieved through a 150-mesh sieve. The polymer matrix and ettringite are mixed and then fed into an internal mixer. The temperature is rapidly raised to 185°C and the mixture is kneaded at 185°C for 3 hours. At the high temperature of 185°C, most of the water of crystallization in ettringite is removed (there may still be 4-6 molecules of water of crystallization remaining), resulting in polymer matrix / ettringite. The water content is 5.24%, indicating that pre-dehydration at 130°C is beneficial for the removal of water of crystallization in the phase region.

[0119] S2. Preparation of composite polymers through compounding:

[0120] The TPU compatibilizer was added to the polymer substrate / ettringite obtained in S1, and the mixture was continuously kneaded at 185°C for 3 hours to obtain the composite polymer.

[0121] S3, Granulation:

[0122] The composite polymer, plasticizer, PE wax, and calcium-zinc stabilizer are placed in a high-speed and low-speed mixer in a certain proportion and stirred and mixed. The mixing speed is 1500 r / min for 15 min and 500 r / min for 10 min. The mixture is then fed into a twin-screw extruder for extrusion granulation. The twin-screw extruder temperature is 160℃-170℃, the feeding frequency is 20-25 Hz, the main extruder speed is 80-100 r / min, and a 100-mesh filter is added to the die head. After hot cutting, cooling by a fan, conveying, and packaging, the finished composite polymer material is obtained.

[0123] III. Performance Testing:

[0124] 1. Sample preparation:

[0125] The PVC-based composite polymer materials obtained in each embodiment and comparative example were added to an extruder with a screw temperature of 130-150°C. After being shaped by a spray sizing box, they were cut into PVC sewage pipes and subjected to various performance tests.

[0126] 2. Performance testing standards:

[0127] 1) According to the requirements of GB-T 5836.1-2018 "Rigid Polyvinyl Chloride (PVC-U) Pipes for Building Drainage", the specific tests include:

[0128] Ring stiffness: Refer to GB / T9647-2015 "Determination of ring stiffness of thermoplastic pipes", the ring stiffness is required to be ≥50 kN / m2;

[0129] Drop hammer test: The test shall be conducted in accordance with GB / T14152-2001. The hammer head shall be of type d90, the test temperature shall be (0±1)℃, and the sample length shall be 195±15mm. It is required that no cracks shall appear in the drop hammer impact test of 9 / 10 and above samples.

[0130] Tensile properties: According to GB / T8804.2-2003 "Determination of tensile properties of thermoplastic pipes - Part 2: Rigid polyvinyl chloride (PYC-U), chlorinated polyvinyl chloride (PVC-C) and high-impact polyvinyl chloride (PVC-HI) pipes", the axial tensile strength is required to be ≥42MPa;

[0131] Heat resistance: Tested according to GB / T8802-2001, the Vicat softening temperature should be ≥79 °C;

[0132] In addition, Examples 4 and 5 were also verified by the same standard, but the above-mentioned acceptable range was not used as the condition for acceptance.

[0133] 2) The flame retardant performance test is conducted in accordance with the DIN 4102-1 fire test standard. The flame retardant levels are A1 (extremely non-combustible), A2 (non-combustible), B1 (not easily combustible), B2 (combustible) and B3 (flammable).

[0134] 3) Salt spray test for corrosion resistance:

[0135] Referring to the salt spray test conditions, test methods, and evaluation criteria for test results specified in GB / T 2423.17, and using the copper ion accelerated acetic acid spray test (CASS test), the test temperature is 50℃ to strongly induce corrosion. Its corrosion rate is approximately 8 times that of the NSS test, and the corrosion severity decreases sequentially from level 1 (severe corrosion) to level 10 (no corrosion). The salt spray test can prove the role of the self-healing cross-linked polyurethane elastomer in the product of this invention.

[0136] 3. Test Results:

[0137] Table 2. Test properties of PVC-based composite polymer materials

[0138]

[0139] As shown in Table 1, compared with Comparative Examples 1-2 and Examples 1-3, the impact resistance of the substrate is PVC < PP < PE, and the rigidity of the substrate is PE < PP < PVC. With the increase of the relative content of ettringite, the rigidity, heat resistance, and flame resistance are all improved. Compared with Comparative Examples 3-4 and Examples 1-3, with the increase of the relative content of TPU compatibilizer, the impact resistance, toughness, and weather resistance are all improved. And Examples 1-3 have a comprehensive improvement in performance compared with Comparative Example 9.

[0140] Compared with Example 2, Comparative Examples 5-8 showed that the use of borate-free ester repair resulted in a decrease in impact resistance, toughness, and weather resistance, which may be attributed to the uneven distribution of the organic and inorganic phase networks. The use of modified phosphogypsum or phosphogypsum instead of ettringite slightly reduced the flame retardant performance, but significantly reduced the weather resistance.

[0141] Compared with Example 2, Comparative Examples 10-11 show some changes in the mixing process. Among them, Comparative Example 10 shows a significant decrease in performance, possibly because its high water content makes it easy to form hydrogel blocks, resulting in a slightly uneven distribution of the organic and inorganic phase networks.

[0142] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A composite polymer material based on modified phosphogypsum, characterized in that, Includes the following components by weight: 100 parts of polymer substrate: PVC, PP or PE; 20-40 parts of ettringite: prepared by mixing and reacting phosphogypsum, calcium oxide, calcium aluminate (CA) and pure water; 20-30 parts of TPU compatibilizer; 15-20 parts plasticizer; 1-3 parts calcium-zinc stabilizer; And 1.2-2.5 parts of PE wax; The preparation process of the TPU compatibilizer is as follows: 1) Preparation of polyurethane prepolymer: After polybutylene adipate melts at 110℃, it is sealed and stirred, and dehydrated under vacuum for 2 hours. Heating is stopped and vacuum is maintained. When the reaction temperature drops to 80℃, the vacuum pump is turned off and nitrogen is introduced into the reaction flask. Isophorone diisocyanate and dibutyltin dilaurate are added dropwise. The reaction is carried out at 80℃ for 3 hours to obtain a clear polyurethane prepolymer. 2) Preparation of polyurethane elastomer: After the prepolymerization reaction is completed, 4,4-diaminodiphenylmethane is added under nitrogen protection, and after mixing, the chain extension reaction is carried out at 80°C for 2 hours. 3) Crosslinking preparation of TPU compatibilizer: Stop heating the reaction solution obtained in 2), add acetone solution with a concentration of 0.03 g / ml boric acid, stir and mix, pour the resulting mixture into a polytetrafluoroethylene mold, heat to 80℃ and seal to cure for 10 h, cool to room temperature, remove from the mold, and obtain TPU compatibilizer containing acetone. The preparation method of the composite polymer material based on modified phosphogypsum includes the following steps: S1. Mixing and dehydration of polymer substrate / ettringite: The polymer substrate and ettringite were mixed and fed into an internal mixer. The temperature was raised to 130°C within 30 minutes and the mixture was stirred at 130°C for 1 hour. The temperature was then rapidly raised to 185°C and stirred at 185°C for 2 hours to obtain the polymer substrate / ettringite. S2. Preparation of composite polymers through compounding: The TPU compatibilizer was added to the polymer matrix / ettringite obtained in S1, and the mixture was continuously kneaded at 185°C for 3 hours to obtain the composite polymer. S3, Granulation: The composite polymer, plasticizer, PE wax, and calcium-zinc stabilizer are placed in a high-speed and low-speed mixer in a certain proportion and stirred and mixed. The mixing speed is 1500 r / min for 15 min and 500 r / min for 10 min. The mixture is then fed into a twin-screw extruder for extrusion and granulation. The temperature of the feed zone of the twin-screw extruder is 40-60℃, the temperature of the melt plasticizing zone is 120℃-170℃, the die head temperature is 160℃-200℃, the feeding frequency is 20-25Hz, the main extruder speed is 80-100 r / min, and a 100-mesh filter screen is added to the die head. After hot cutting, cooling by a fan, conveying, and packaging, the finished composite polymer material is obtained.

2. The composite polymer material based on modified phosphogypsum according to claim 1, characterized in that, In the preparation of the TPU compatibilizer, the molar ratio of polybutylene adipate, isophorone diisocyanate, dibutyltin dilaurate, 4,4-diaminodiphenylmethane and boric acid is 1:2:0.0016:0.48:0.

49.

3. The composite polymer material based on modified phosphogypsum according to claim 1, characterized in that, The 4,4-diaminodiphenylmethane added in step 2) is specifically an acetone solution of 4,4-diaminodiphenylmethane with a concentration of 0.2 g / ml.

4. The composite polymer material based on modified phosphogypsum according to claim 1, characterized in that, The preparation process of the ettringite is as follows: Phosphogypsum, calcium oxide, and pure water were mixed in a weight ratio of 5:1:

5. Calcium aluminate (CA) was added, and the molar ratio of CA to CaO was controlled at 1:2.05-2.

1. The mixture was stirred at 500 r / min for 2 h to obtain ettringite.

5. The composite polymer material based on modified phosphogypsum according to claim 1, characterized in that, The ettringite in S1 is ground and sieved through a 150-mesh screen before use.

6. The composite polymer material based on modified phosphogypsum according to claim 1, characterized in that, During the mixing process of S1, volatile gases are emitted and are collected and filtered by alkaline solution.

7. The composite polymer material based on modified phosphogypsum according to claim 1, characterized in that, Volatile gases are emitted during the mixing process of S2, and these gases are collected by condensation.

8. The composite polymer material based on modified phosphogypsum according to claim 1, characterized in that, The temperature of the twin-screw extruder in S3 is set in the following ways: when the polymer substrate is PVC or PP, the temperature of the feeding zone of the twin-screw extruder is 50-60℃, the temperature of the melting and plasticizing zone is 160℃-170℃, and the temperature of the die head is 190℃-200℃. When the polymer substrate is PE, the feed zone temperature of the screw extruder is 40-50℃, the melt plasticizing zone temperature is 120℃-130℃, and the die head temperature is 160℃-170℃.

Images