Chlorinated polyvinyl chloride board and method for manufacturing the same

Abstract

The application provides a chlorinated polyvinyl chloride plate and a preparation method thereof, and belongs to the technical field of chlorinated polyvinyl chloride plates. The preparation method comprises the steps of chlorination, maleic anhydride pretreatment, preparation of reinforcing material, preparation of dry mixture and post-treatment. In the step of preparing the reinforcing material, the alkali immersion fiber is put into alumina sol, and then is left to stand for 20-25 min; after being taken out, the fiber is left to stand at room temperature; after being dried, the fiber is subjected to heat treatment, and is kept at 120-125 DEG C for 0.8-1.2 h, kept at 380-420 DEG C for 0.8-1.0 h, and kept at 590-600 DEG C for 1.8-2.0 h, so as to obtain the reinforcing material. The chlorinated polyvinyl chloride plate prepared by the method has high strength, good toughness, excellent impact resistance and excellent stability.

Description

Technical Field

[0001] This invention belongs to the technical field of chlorinated polyvinyl chloride (PVC) sheets, specifically relating to a chlorinated PVC sheet and its preparation method. Background Technology

[0002] Chlorinated polyvinyl chloride (CPVC) sheets are widely used in chemical, construction and other fields due to their high temperature resistance, corrosion resistance and flame retardancy. However, in China, the production process of CPVC, which is made from polyvinyl chloride through chlorination, is fragmented, with chlorination, formulation design and mixing processes being disconnected. This makes it impossible to consistently produce formulations that meet the processing needs of downstream product manufacturers, further restricting the large-scale and high-quality production of CPVC sheets.

[0003] Currently, the CPVC raw materials and related processes used in the preparation of CPVC sheets are mainly divided into three types, as follows: Firstly, some manufacturers directly use imported chlorination powder and process it themselves. This method not only suffers from high prices and unstable supply chains due to reliance on imported raw materials, but also from poor formula compatibility, unstable processing performance, and uneven mechanical properties of the products when manufacturers adjust the formula themselves because they lack professional mixing technology. In addition, the chlorination degree and molecular weight distribution of imported chlorination powder are not compatible with the characteristics of local equipment in China, which will also have an adverse effect on the production quality of CPVC sheets.

[0004] Secondly, product manufacturers use formulations provided by mixing plants for direct processing. The formulations provided by mixing plants are mostly general formulations, which are difficult to meet the special performance requirements such as high weather resistance and ultra-high toughness. Furthermore, after long-distance transportation or long-term storage, the additives in the formulations are prone to migration and precipitation, which leads to a decline in secondary processing performance and affects the quality of the final product.

[0005] Third, some manufacturers use the formula materials provided by the chlorination plant to process the products directly. Some chlorination plants with weak production process stability and imperfect quality control management will use a fixed formula to mix and package the products based on their own unstable CPVC chlorination powder, thereby providing downstream manufacturers with formula materials of unstable quality, increasing downstream production fluctuations, and affecting production efficiency and product qualification rate.

[0006] In addition, traditional domestic chlorination processes mostly use suspension PVC as raw material and carry out the chlorination reaction in the aqueous phase. The core defect of this process is that it is difficult to control the uniformity of chlorination, which can easily lead to uneven distribution of chlorine elements on the molecular chain of CPVC powder, thereby affecting the thermal stability, processing rheology and long-term mechanical properties of CPVC products. Meanwhile, the following two major problems exist in the processing and preparation of CPVC sheets: First, the processing window is narrow. The imbalance in the ratio of internal and external lubricants in traditional formulations, as well as the unreasonable combination of processing aids (ACR) and impact modifiers (MBS), can lead to premature or delayed plasticization of materials in the extruder, a narrow processing temperature range, and consequently, problems such as material degradation or poor plasticization. Second, the migration and precipitation of additives. In order to reduce costs, existing technologies typically use additives with low molecular weight or poor compatibility with CPVC. These additives are prone to migrate to the surface of the material during storage or heating, resulting in a decrease in secondary processing performance.

[0007] The various defects in the raw materials, processes, and processing mentioned above will directly affect the rheological behavior, thermal stability, and internal stress distribution of CPVC melt, ultimately resulting in quality problems such as warping, insufficient strength, and poor impact toughness of the sheets, which seriously limits the application range and market competitiveness of CPVC sheets.

[0008] Therefore, providing a chlorinated polyvinyl chloride (CPVC) sheet and its preparation method to overcome the defects of unstable CPVC powder quality in China, achieve a wider processing window, and significantly improve the rigidity and long-term heat resistance of the sheet while ensuring impact strength is an urgent technical problem to be solved. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a chlorinated polyvinyl chloride (CPVC) sheet and its preparation method, which overcomes the defect of unstable CPVC powder quality in China, and significantly improves the rigidity and long-term heat resistance of the sheet while ensuring impact strength, thus enhancing its stability.

[0010] To address the aforementioned technical problems, the present invention adopts the following technical solution: A method for preparing chlorinated polyvinyl chloride (PVC) sheets includes chlorination, maleic anhydride pretreatment, preparation of reinforcing material, preparation of dry mix, and post-treatment steps, as detailed below: 1. Chlorination (1) Preparation of chlorination auxiliaries Adjust the speed of the high-speed mixer to 750-820 rpm at room temperature and stir for 3-5 minutes. While stirring, add benzoyl peroxide, calcium stearate and fatty alcohol polyoxyethylene ether, and continue stirring for 15-20 minutes to obtain the chlorination auxiliary. The mass ratio of benzoyl peroxide, calcium stearate, and fatty alcohol polyoxyethylene ether is 1.4-1.6:1.0-1.3:0.3-0.5; (2) Chlorination reaction Add 4-5 wt% hydrochloric acid solution to the chlorination reactor. Under a nitrogen atmosphere, add polyvinyl chloride (PVC) while stirring at 75-85 rpm for 25-35 minutes. Then add the chlorination auxiliaries and stir for 15-25 minutes. After stirring, raise the temperature to 78-82℃ at a rate of 1.5-2.0℃ / min, and begin introducing chlorine gas, controlling the chlorine gas introduction efficiency at 0.8-1.0 g / min and the pressure at 0.05-0.10 MPa. Maintain this temperature for 1.4-1.6 hours, and then raise the temperature at a rate of 1.0-1.2℃ / min. The temperature was raised to 118-122℃, and the chlorine gas introduction efficiency was controlled at 1.2-1.5 g / min, the pressure at 0.10-0.15 MPa, and the temperature was maintained for 1.8-2.3 h. Then the chlorine gas introduction efficiency was reduced to 0.3-0.5 g / min, the pressure was controlled at 0.08-0.12 MPa, and the reaction was maintained at 118-122℃. During the holding process, the chlorine content was sampled every 20 min. When the chlorine content reached 65-67%, the chlorine gas introduction was immediately stopped, the heating was stopped, nitrogen gas was introduced for purging, and after cooling, the product was washed and dried to obtain chlorinated polyvinyl chloride. The degree of polymerization of the polyvinyl chloride is 1000-1200; The mass ratio of the hydrochloric acid solution, polyvinyl chloride, and chlorination auxiliaries is 2000:700-720:3.5-4.0.

[0011] 2. Maleic anhydride pretreatment Chlorinated polyvinyl chloride (PVC) is fed into the feeding section of a twin-screw extruder and melted at 165-175℃ for 5-8 minutes. Maleic anhydride, azobisisobutyronitrile (AIBN), and dibutyl phthalate (DBP) are then added. The temperature of the melting section is controlled at 180-190℃, the temperature of the grafting section at 185-195℃, and the temperature of the die head section at 180-185℃. The screw speed is 70-80 rpm. When the extrusion reaches the 8th minute, hydroquinone is added. The total melt extrusion time is controlled at 10-12 minutes. After cooling, the product is pelletized and dried to obtain pretreated chlorinated PVC. The mass ratio of chlorinated polyvinyl chloride, maleic anhydride, azobisisobutyronitrile, dibutyl phthalate, and hydroquinone is 1000:12-15:0.4-0.6:0.3-0.5:0.1-0.2.

[0012] 3. Preparation of reinforcing materials Basalt fibers are immersed in a 10-12 wt% sodium hydroxide solution (4-6 times their weight) at 60-64℃ for 1.0-1.2 hours. After removal, they are washed and dried to obtain alkali-impregnated fibers. The alkali-impregnated fibers are then immersed in alumina sol (6-8 times their weight) and allowed to stand for 20-25 minutes. After removal, they are allowed to stand at room temperature for 1.5-2.0 hours and dried. Then, they are subjected to heat treatment: first, the temperature is increased to 120-125℃ at a rate of 1.5-2.0℃ / min and held for 0.8-1.2 hours; then, the temperature is increased to 380-420℃ at a rate of 2.0-2.5℃ / min and held for 0.8-1.0 hours; finally, the temperature is increased to 590-600℃ at a rate of 3.5-4.0℃ / min and held for 1.8-2.0 hours. After natural cooling to room temperature, the reinforcing material is obtained. The basalt fibers have a length of 3-5 mm and a diameter of 10-15 μm; The alumina sol is prepared by adding 10-15g of aluminum isopropoxide to 90-100mL of isopropanol I, stirring at 58-60℃ until completely dissolved, then adding 2-4mL of acetylacetone, and continuing to stir for 0.8-1.0h to obtain an aluminum isopropoxide solution; mixing 6-10g of deionized water and 25-30mL of isopropanol II, stirring evenly, and then adding to the aluminum isopropoxide solution, continuing to stir for 1.8-2.0h, adding 8-10wt% nitric acid solution to adjust the pH to 3.5-4.5, and allowing to stand and age at room temperature for 20-24h to obtain the alumina sol; In the aluminum isopropoxide solution, the volume-to-mass ratio of isopropanol, aluminum isopropoxide, and acetylacetone is 90-100 mL: 10-15 g: 2-4 mL. The mass-to-volume ratio of the deionized water to isopropanol di is 6-10g:25-30mL; The mass ratio of deionized water to aluminum isopropoxide is 6-10:10-15.

[0013] 4. Preparation of dry mixture Pretreated chlorinated polyvinyl chloride, reinforcing material, methyl methacrylate-butadiene-styrene copolymer (MBS), methyl methacrylate copolymer, oxidized polyethylene wax, stearic acid, and titanium dioxide are added to a mixer and stirred at 700-800 rpm until homogeneous. The temperature is then raised to 106-110℃ and stirred for 5-6 minutes. The temperature is then lowered to 40-45℃ and stirred at 200-300 rpm for 10-15 minutes to obtain a dry chlorinated polyvinyl chloride mixture. The methyl methacrylate-butadiene-styrene copolymer MBS is manufactured by Kaneka Corporation of Japan, and its brand name is M-711. The methyl methacrylate copolymer is manufactured by Rohm and Haas and has the brand name K-400. The melting point of the oxidized polyethylene wax is 100-105℃; The mass ratio of the pretreated chlorinated polyvinyl chloride, reinforcing material, methyl methacrylate-butadiene-styrene copolymer (MBS), methyl methacrylate copolymer, oxidized polyethylene wax, stearic acid, and titanium dioxide is 100:12-18:4-5:1.8-2.3:1.2-1.5:0.8-1.0:1-2.

[0014] 5. Post-processing The dry-mixed chlorinated polyvinyl chloride (PVC) is added to a single-screw extruder, with the length-to-diameter ratio controlled at 24-26:1, the screw speed at 20-25 rpm, the feeding zone temperature at 164-166℃, the compression zone temperature at 173-177℃, the metering zone temperature at 182-186℃, and the die head temperature at 188-193℃. It then enters a three-roll calender for calendering, with the calender roll surface temperature controlled at 85-90℃. After cooling to 38-40℃, it is traction-cut, with the traction machine speed at 25-30 cm / min and the traction pressure at 0.10-0.15 MPa, to obtain chlorinated PVC sheets with a thickness of 4-8 mm.

[0015] A chlorinated polyvinyl chloride sheet is prepared using the aforementioned method.

[0016] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The chlorinated polyvinyl chloride sheet obtained by this invention has a thickness of 4-8 mm; 2. The chlorinated polyvinyl chloride sheet obtained by the present invention has a tensile strength of 55.6-67.4 MPa, a flexural strength of 112.5-134.7 MPa, and a flexural modulus of 2985-3554 MPa; 3. The chlorinated polyvinyl chloride sheet prepared by this invention has a notched impact strength of 12.4-17.9 kJ / m² for simply supported beams. 2 ; 4. The chlorinated polyvinyl chloride (PVC) sheet prepared by this invention was placed in an oven at 95°C and allowed to stand for 120 hours. After being removed and allowed to return to room temperature naturally, it was placed in a freezer at -25°C and allowed to stand for 120 hours. After being removed and allowed to return to room temperature naturally, it was allowed to stand for 24 hours. The tensile strength was measured again to be 53.0-64.7 MPa, the flexural strength to be 107.1-128.9 MPa, and the notched impact strength of a simply supported beam to be 11.9-17.3 kJ / m. 2 . Detailed Implementation

[0017] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0018] Example 1 1. Chlorination (1) Preparation of chlorination auxiliaries Adjust the speed of the high-speed mixer to 750 rpm at room temperature and stir for 3 minutes. While stirring, add 1.4 g of benzoyl peroxide, 1.0 g of calcium stearate and 0.3 g of fatty alcohol polyoxyethylene ether, and continue stirring for 15 minutes to obtain the chlorination auxiliary agent. (2) Chlorination reaction Add 2000g to the chlorination reactor 700g of polyvinyl chloride (PVC) was added to a 4wt% hydrochloric acid solution under a nitrogen atmosphere and stirred at 75 rpm for 25 min. Then, 3.5g of chlorination auxiliaries were added and stirred for 15 min. After stirring, the temperature was increased to 78℃ at a rate of 1.5℃ / min, and chlorine gas was introduced, with the chlorine gas introduction efficiency controlled at 0.8g / min and the pressure at 0.05MPa. The temperature was maintained for 1.4 h. Then, the temperature was increased to 118℃ at a rate of 1.0℃ / min, with the chlorine gas introduction efficiency controlled at 1.2g / min and the pressure at 0.10MPa. The temperature was maintained for 1.8 h. Then, the chlorine gas introduction efficiency was reduced to 0.3g / min, and the pressure was controlled at 0.08MPa. The reaction was maintained at 118℃. During the heat treatment, the chlorine content was measured every 20 min. When the chlorine content reached 65%, the chlorine gas introduction was immediately stopped, and the heating was stopped. Nitrogen gas was introduced for purging. After cooling, the product was washed and dried to obtain chlorinated polyvinyl chloride. The degree of polymerization of the polyvinyl chloride is 1000.

[0019] 2. Maleic anhydride pretreatment 1000g of chlorinated polyvinyl chloride was fed into the feeding section of a twin-screw extruder and melted at 165℃ for 5 minutes. Then, 12g of maleic anhydride, 0.4g of azobisisobutyronitrile, and 0.3g of dibutyl phthalate were added. The temperature of the melting section was controlled at 180℃, the temperature of the grafting section was controlled at 185℃, the temperature of the die head section was controlled at 180℃, and the screw speed was controlled at 70rpm. When the extrusion reached the 8th minute, 0.1g of hydroquinone was added, and the total melt extrusion time was controlled at 10 minutes. After cooling, the product was pelletized and dried to obtain pretreated chlorinated polyvinyl chloride.

[0020] 3. Preparation of reinforcing materials Basalt fibers were immersed in a 10wt% sodium hydroxide solution (4 times their weight) at 60°C for 1.0 h. After removal, they were washed and dried to obtain alkali-impregnated fibers. The alkali-impregnated fibers were then placed in alumina sol (6 times their weight) and allowed to stand for 20 min. After removal, they were allowed to stand at room temperature for 1.5 h and dried. Then, they were subjected to heat treatment: first, the temperature was increased to 120°C at a rate of 1.5°C / min and held for 0.8 h; then, the temperature was increased to 380°C at a rate of 2.0°C / min and held for 0.8 h; then, the temperature was increased to 590°C at a rate of 3.5°C / min and held for 1.8 h. After natural cooling to room temperature, the reinforcing material was obtained. The basalt fibers are 3 mm in length and 10 μm in diameter. The alumina sol is prepared by adding 10g of aluminum isopropoxide to 90mL of isopropanol, stirring at 58℃ until completely dissolved, adding 2mL of acetylacetone, and continuing to stir for 0.8h to obtain an aluminum isopropoxide solution; mixing 6g of deionized water and 25mL of isopropanol, stirring evenly, adding to the aluminum isopropoxide solution, and continuing to stir for 1.8h; adding 8wt% nitric acid solution to adjust the pH to 3.5; and allowing to stand and age at room temperature for 20h to obtain the alumina sol. The mass ratio of deionized water to aluminum isopropoxide is 6:10.

[0021] 4. Preparation of dry mixture 100g of pretreated chlorinated polyvinyl chloride, 12g of reinforcing material, 4g of methyl methacrylate-butadiene-styrene copolymer (MBS), 1.8g of methyl methacrylate copolymer, 1.2g of oxidized polyethylene wax, 0.8g of stearic acid, and 1g of titanium dioxide were added to a mixer and stirred at 700 rpm until homogeneous. The temperature was then raised to 106℃ and stirred for 5 minutes. The temperature was then lowered to 40℃ and stirred at 200 rpm for 10 minutes to obtain a dry mixture of chlorinated polyvinyl chloride. The methyl methacrylate-butadiene-styrene copolymer MBS is manufactured by Kaneka Corporation of Japan, and its brand name is M-711. The methyl methacrylate copolymer is manufactured by Rohm and Haas and has the brand name K-400. The melting point of the oxidized polyethylene wax is 100°C.

[0022] 5. Post-processing The dry-mixed chlorinated polyvinyl chloride (PVC) was added to a single-screw extruder, with the length-to-diameter ratio controlled at 24:1, the screw speed at 20 rpm, the temperature in the feeding zone at 164℃, the temperature in the compression zone at 173℃, the temperature in the metering zone at 182℃, and the die head temperature at 188℃. Then, it was fed into a three-roll calender for calendering, with the calender roll surface temperature controlled at 85℃. After cooling to 38℃, it was traction-cut with a traction machine speed of 25 cm / min and a traction pressure of 0.10 MPa to obtain chlorinated PVC sheets with a thickness of 4 mm.

[0023] Example 2 1. Chlorination (1) Preparation of chlorination auxiliaries Adjust the speed of the high-speed mixer to 800 rpm at room temperature and stir for 4 minutes. While stirring, add 1.5 g of benzoyl peroxide, 1.2 g of calcium stearate and 0.4 g of fatty alcohol polyoxyethylene ether, and continue stirring for 18 minutes to obtain the chlorination auxiliary agent. (2) Chlorination reaction Add 2000g to the chlorination reactor A 5wt% hydrochloric acid solution was added to 710g of polyvinyl chloride (PVC) under a nitrogen atmosphere and stirred at 80rpm. The mixture was stirred for 30min, followed by the addition of 3.8g of chlorination auxiliaries and stirring for 20min. After stirring, the temperature was increased to 80℃ at a rate of 1.8℃ / min, and chlorine gas was introduced at a rate of 0.9g / min and a pressure of 0.08MPa. The mixture was kept at this temperature for 1.5h. Then, the temperature was increased to 120℃ at a rate of 1.1℃ / min, and the chlorine gas introduction efficiency was controlled at 1.3g / min and a pressure of 0.12MPa. The mixture was kept at this temperature for 2.0h. Finally, the chlorine gas introduction efficiency was reduced to 0.4g / min, and the pressure was controlled at 0.10MPa. The mixture was kept at 120℃. During the heat treatment, the chlorine content was measured every 20min. When the chlorine content reached 66%, the chlorine gas introduction and heating were immediately stopped. Nitrogen gas was introduced to purge the mixture. After cooling, the mixture was washed and dried to obtain chlorinated polyvinyl chloride. The degree of polymerization of the polyvinyl chloride is 1100.

[0024] 2. Maleic anhydride pretreatment 1000g of chlorinated polyvinyl chloride was fed into the feeding section of a twin-screw extruder and melted at 170℃ for 7 minutes. Then, 14g of maleic anhydride, 0.5g of azobisisobutyronitrile, and 0.4g of dibutyl phthalate were added. The temperature of the melting section was controlled at 185℃, the temperature of the grafting section at 190℃, and the temperature of the die head section at 183℃. The screw speed was 75rpm. When the extrusion reached the 8th minute, 0.2g of hydroquinone was added. The total melt extrusion time was controlled at 11 minutes. After cooling, the product was pelletized and dried to obtain pretreated chlorinated polyvinyl chloride.

[0025] 3. Preparation of reinforcing materials Basalt fibers were immersed in an 11wt% sodium hydroxide solution (5 times their weight) at 62℃ for 1.1 hours. After removal, they were washed and dried to obtain alkali-impregnated fibers. The alkali-impregnated fibers were then placed in an alumina sol (7 times their weight) and allowed to stand for 23 minutes. After removal, they were allowed to stand at room temperature for 1.8 hours and dried. Then, they were subjected to heat treatment: first, the temperature was increased to 123℃ at a rate of 1.8℃ / min and held for 1.0 hour; then, the temperature was increased to 400℃ at a rate of 2.3℃ / min and held for 0.9 hours; then, the temperature was increased to 595℃ at a rate of 3.7℃ / min and held for 2.0 hours. After natural cooling to room temperature, the reinforcing material was obtained. The basalt fibers are 4 mm in length and 13 μm in diameter. The alumina sol is prepared by adding 13g of aluminum isopropoxide to 95mL of isopropanol, stirring at 60°C until completely dissolved, adding 3mL of acetylacetone, and continuing to stir for 1.0h to obtain an aluminum isopropoxide solution; mixing 8g of deionized water and 28mL of isopropanol, stirring evenly, adding to the aluminum isopropoxide solution, and continuing to stir for 2.0h; adding 10wt% nitric acid solution to adjust the pH to 4.0; and allowing to stand and age at room temperature for 22h to obtain the alumina sol. The mass ratio of deionized water to aluminum isopropoxide is 8:13.

[0026] 4. Preparation of dry mixture 100g of pretreated chlorinated polyvinyl chloride, 16g of reinforcing material, 5g of methyl methacrylate-butadiene-styrene copolymer (MBS), 2.0g of methyl methacrylate copolymer, 1.4g of oxidized polyethylene wax, 1.0g of stearic acid, and 2g of titanium dioxide were added to a mixer and stirred at 750 rpm until homogeneous. The temperature was then raised to 108℃ and stirred for 6 minutes. The temperature was then lowered to 42℃ and stirred at 250 rpm for 12 minutes to obtain a dry mixture of chlorinated polyvinyl chloride. The methyl methacrylate-butadiene-styrene copolymer MBS is manufactured by Kaneka Corporation of Japan, and its brand name is M-711. The methyl methacrylate copolymer is manufactured by Rohm and Haas and has the brand name K-400. The melting point of the oxidized polyethylene wax is 103°C.

[0027] 5. Post-processing The dry-mixed chlorinated polyvinyl chloride (PVC) was added to a single-screw extruder, with the length-to-diameter ratio controlled at 25:1, the screw speed at 23 rpm, the temperature in the feeding zone at 165℃, the temperature in the compression zone at 175℃, the temperature in the metering zone at 184℃, and the die head temperature at 190℃. Then, it was fed into a three-roll calender for calendering, with the calender roll surface temperature controlled at 88℃. After cooling to 40℃, it was traction-cut with the traction machine speed at 27 cm / min and the traction pressure at 0.12 MPa, resulting in a 6 mm thick chlorinated PVC sheet.

[0028] Example 3 1. Chlorination (1) Preparation of chlorination auxiliaries Adjust the speed of the high-speed mixer to 820 rpm at room temperature and stir for 5 minutes. While stirring, add 1.6 g of benzoyl peroxide, 1.3 g of calcium stearate and 0.5 g of fatty alcohol polyoxyethylene ether, and continue stirring for 20 minutes to obtain the chlorination auxiliary agent. (2) Chlorination reaction Add 2000g to the chlorination reactor A 5wt% hydrochloric acid solution was added to 720g of polyvinyl chloride (PVC) under a nitrogen atmosphere and stirred at 85rpm. The mixture was stirred for 35min, followed by the addition of 4.0g of chlorination auxiliaries and stirring for 25min. After stirring, the temperature was increased to 82℃ at a rate of 2.0℃ / min, and chlorine gas was introduced at a rate of 1.0g / min and a pressure of 0.10MPa. The mixture was kept at this temperature for 1.6h. Then, the temperature was increased to 122℃ at a rate of 1.2℃ / min, and the chlorine gas introduction efficiency was controlled at 1.5g / min and a pressure of 0.15MPa. The mixture was kept at this temperature for 2.3h. Finally, the chlorine gas introduction efficiency was reduced to 0.5g / min, and the pressure was controlled at 0.12MPa. The mixture was kept at 122℃. During the heat treatment, the chlorine content was measured every 20min. When the chlorine content reached 67%, the chlorine gas introduction and heating were immediately stopped. Nitrogen gas was introduced for purging. After cooling, the mixture was washed and dried to obtain chlorinated polyvinyl chloride. The degree of polymerization of the polyvinyl chloride is 1200.

[0029] 2. Maleic anhydride pretreatment 1000g of chlorinated polyvinyl chloride was fed into the feeding section of a twin-screw extruder and melted at 175℃ for 8 minutes. Then, 15g of maleic anhydride, 0.6g of azobisisobutyronitrile, and 0.5g of dibutyl phthalate were added. The temperature of the melting section was controlled at 190℃, the temperature of the grafting section at 195℃, and the temperature of the die head section at 185℃. The screw speed was 80rpm. When the extrusion reached the 8th minute, 0.2g of hydroquinone was added. The total melt extrusion time was controlled at 12 minutes. After cooling, the product was pelletized and dried to obtain pretreated chlorinated polyvinyl chloride.

[0030] 3. Preparation of reinforcing materials Basalt fibers were immersed in a 12wt% sodium hydroxide solution (6 times their weight) at 64℃ for 1.2 hours. After removal, they were washed and dried to obtain alkali-impregnated fibers. The alkali-impregnated fibers were then placed in an alumina sol (8 times their weight) and allowed to stand for 25 minutes. After removal, they were allowed to stand at room temperature for 2.0 hours and dried. Then, they were subjected to heat treatment: first, the temperature was increased to 125℃ at a rate of 2.0℃ / min and held for 1.2 hours; then, the temperature was increased to 420℃ at a rate of 2.5℃ / min and held for 1.0 hour; then, the temperature was increased to 600℃ at a rate of 4.0℃ / min and held for 2.0 hours. After natural cooling to room temperature, the reinforcing material was obtained. The basalt fibers are 5 mm in length and 15 μm in diameter. The alumina sol is prepared by adding 15g of aluminum isopropoxide to 100mL of isopropanol, stirring at 60℃ until completely dissolved, adding 4mL of acetylacetone, and continuing to stir for 1.0h to obtain an aluminum isopropoxide solution; mixing 10g of deionized water and 30mL of isopropanol, stirring evenly, adding to the aluminum isopropoxide solution, and continuing to stir for 2.0h; adding 10wt% nitric acid solution to adjust the pH to 4.5, and allowing to stand and age at room temperature for 24h to obtain the alumina sol. The mass ratio of deionized water to aluminum isopropoxide is 10:15.

[0031] 4. Preparation of dry mixture Add 100g of pretreated chlorinated polyvinyl chloride, 18g of reinforcing material, 5g of methyl methacrylate-butadiene-styrene copolymer (MBS), 2.3g of methyl methacrylate copolymer, 1.5g of oxidized polyethylene wax, 1.0g of stearic acid, and 2g of titanium dioxide to a mixer and stir at 800 rpm until homogeneous. Increase the temperature to 110℃ and continue stirring for 6 minutes. Decrease the temperature to 45℃ and stir at 300 rpm for 15 minutes to obtain a dry mixture of chlorinated polyvinyl chloride. The methyl methacrylate-butadiene-styrene copolymer MBS is manufactured by Kaneka Corporation of Japan, and its brand name is M-711. The methyl methacrylate copolymer is manufactured by Rohm and Haas and has the brand name K-400. The melting point of the oxidized polyethylene wax is 105°C.

[0032] 5. Post-processing The dry-mixed chlorinated polyvinyl chloride (PVC) material was added to a single-screw extruder, with the length-to-diameter ratio controlled at 26:1, the screw speed at 25 rpm, the temperature in the feeding zone at 166℃, the temperature in the compression zone at 177℃, the temperature in the metering zone at 186℃, and the die head temperature at 193℃. Then, it was fed into a three-roll calender for calendering, with the calender roll surface temperature controlled at 90℃. After cooling to 40℃, it was traction-cut with the traction machine speed at 30 cm / min and the traction pressure at 0.15 MPa, resulting in PVC sheets with a thickness of 8 mm.

[0033] Comparative Example 2-1 The changes made in Example 2 are as follows: The maleic anhydride pretreatment step is omitted. In the dry mix preparation step, the pretreated chlorinated polyvinyl chloride is replaced with an equal amount of untreated chlorinated polyvinyl chloride. The rest of the operations are exactly the same.

[0034] Comparative Example 2-2 The changes made in Example 2 are as follows: In the step of preparing the reinforcing material, the method for preparing the alumina sol is as follows: 10g of alumina nanopowder is added to 70g of deionized water and stirred at 200rpm for 30min to obtain alumina nanopowder. The alumina nanopowder has a particle size of 120 nm. The rest of the operations are exactly the same.

[0035] Performance testing The chlorinated polyvinyl chloride (PVC) sheets prepared in Examples 1-3, Comparative Example 2-1, and Comparative Example 2-2 were subjected to performance tests, as detailed below: 1. Basic performance

[0036] 2. Long-term heat resistance The chlorinated polyvinyl chloride (PVC) sheets prepared in Examples 1-3, Comparative Examples 2-1, and 2-2 were placed in an oven and heated to 95°C for 120 hours. After being removed and allowed to return to room temperature, they were placed in a freezer and cooled to -25°C for 120 hours. After being removed and allowed to return to room temperature for 24 hours, the tensile strength, flexural strength, and notched impact strength of the simply supported beam were tested again, as detailed below:

[0037] This invention first chlorinates polyvinyl chloride (PVC) to obtain chlorinated PVC with a high chlorine content. During the board preparation process, maleic anhydride is used to pretreat the chlorinated PVC. The pretreated chlorinated PVC possesses highly active anhydride groups, which enhances its compatibility with basalt fibers. In the preparation of the reinforcing material, basalt fibers and alumina sol are used as the reinforcing phases. Basalt fibers, as rigid inorganic fibers, possess high modulus and high strength, and can bear most of the load under stress. Specifically, the basalt fibers are first alkali-impregnated to create roughened sites and active groups on the fiber surface, then... Subsequently, alumina sol coating is applied, which can form a film layer on the fiber surface. The alumina sol contains a large number of hydroxyl groups, which can combine with the anhydride groups of the pretreated chlorinated polyvinyl chloride. The alumina transition layer can also alleviate stress concentration. After step-by-step high-temperature heat treatment, the alumina layer becomes more stable and dense. Combined with components such as methyl methacrylate-butadiene-styrene copolymer (MBS) and methyl methacrylate copolymer, the toughness of the product is enhanced. Ultimately, the chlorinated polyvinyl chloride sheet has high tensile strength, flexural strength, and flexural modulus, while also enhancing impact strength and ensuring stable performance.

[0038] Comparative Example 2-1 omitted the pretreatment of chlorinated polyvinyl chloride. Without maleic anhydride treatment, the molecular chain of chlorinated polyvinyl chloride is a weakly polar organic phase, while basalt fiber and alumina layer are strong polar inorganic phases. The large difference in polarity and poor compatibility result in a large number of interface defects, which will reduce the tensile strength and elasticity of the product. Furthermore, when subjected to load impact, cracks will spread rapidly along the interface gaps, making the board brittle and prone to breakage. After long-term high-temperature and low-temperature treatment, the strength drops sharply. Comparative Example 2-2 used maleic anhydride to pretreat chlorinated polyvinyl chloride, but directly combining alumina powder and basalt fiber resulted in alumina nanoparticles being discrete particles that could only loosely adhere to the fiber surface, failing to form a uniform and continuous coating layer. This led to severe particle agglomeration, resulting in poor bonding between the organic matrix and the fiber, poor product stability, and reduced strength performance.

[0039] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0040] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing chlorinated polyvinyl chloride (PVC) sheets, characterized in that, The process includes chlorination, maleic anhydride pretreatment, preparation of reinforcing material, preparation of dry mix, and post-treatment steps. The maleic anhydride pretreatment step is as follows: chlorinated polyvinyl chloride is fed into a twin-screw extruder and melted at 165-175℃ for 5-8 minutes. Maleic anhydride, azobisisobutyronitrile, and dibutyl phthalate are added. The temperature of the melting section is controlled at 180-190℃, the temperature of the grafting section at 185-195℃, and the temperature of the die head section at 180-185℃. The screw speed is 70-80 rpm. When the extrusion reaches the 8th minute, hydroquinone is added. The total melt extrusion time is controlled at 10-12 minutes. After cooling, the product is pelletized and dried to obtain pretreated chlorinated polyvinyl chloride. The steps for preparing the reinforcing material are as follows: alkali-impregnated fibers are placed in alumina sol and left to stand for 20-25 minutes. After being removed, the fibers are left to stand at room temperature, dried, and then subjected to heat treatment: 120-125℃ for 0.8-1.2 hours, 380-420℃ for 0.8-1.0 hours, and 590-600℃ for 1.8-2.0 hours to obtain the reinforcing material.

2. The method for preparing a chlorinated polyvinyl chloride sheet according to claim 1, characterized in that, The chlorination step includes the preparation of a chlorination auxiliary agent and a chlorination reaction; The steps for preparing the chlorination auxiliary are as follows: adjust the speed of the high-speed mixer to 750-820 rpm at room temperature, stir for 3-5 minutes, add benzoyl peroxide, calcium stearate and fatty alcohol polyoxyethylene ether while stirring, and continue stirring for 15-20 minutes to obtain the chlorination auxiliary. The mass ratio of benzoyl peroxide, calcium stearate, and fatty alcohol polyoxyethylene ether is 1.4-1.6:1.0-1.3:0.3-0.

5.

3. The method for preparing a chlorinated polyvinyl chloride sheet according to claim 2, characterized in that, The chlorination reaction steps are as follows: Add 4-5 wt% hydrochloric acid solution to the chlorination reactor. Under a nitrogen atmosphere and with stirring at 75-85 rpm, add polyvinyl chloride (PVC) and stir for 25-35 min. Then add the chlorination auxiliaries and stir for 15-25 min. After stirring, raise the temperature to 78-82℃ at a rate of 1.5-2.0℃ / min, begin introducing chlorine gas, controlling the chlorine gas introduction efficiency at 0.8-1.0 g / min and the pressure at 0.05-0.10 MPa. Maintain the temperature for 1.4-1.6 h, then reduce the chlorination rate to 1.0-1.2℃ / min. The temperature is increased to 118-122℃, with the chlorine gas introduction efficiency controlled at 1.2-1.5 g / min and the pressure at 0.10-0.15 MPa. The temperature is maintained for 1.8-2.3 h. Then, the chlorine gas introduction efficiency is reduced to 0.3-0.5 g / min and the pressure is controlled at 0.08-0.12 MPa. The reaction is maintained at 118-122℃. During the heat treatment, the chlorine content is sampled every 20 min. When the chlorine content reaches 65-67%, the chlorine gas introduction and heating are stopped immediately. Nitrogen gas is introduced to purge the mixture. After cooling, the mixture is washed and dried to obtain chlorinated polyvinyl chloride. The degree of polymerization of the polyvinyl chloride is 1000-1200; The mass ratio of the hydrochloric acid solution, polyvinyl chloride, and chlorination auxiliaries is 2000:700-720:3.5-4.

0.

4. The method for preparing a chlorinated polyvinyl chloride sheet according to claim 1, characterized in that, In the maleic anhydride pretreatment step, the mass ratio of chlorinated polyvinyl chloride, maleic anhydride, azobisisobutyronitrile, dibutyl phthalate, and hydroquinone is 1000:12-15:0.4-0.6:0.3-0.5:0.1-0.

2.

5. The method for preparing a chlorinated polyvinyl chloride sheet according to claim 1, characterized in that, In the step of preparing the reinforcing material, the method for preparing the alkali-impregnated fiber is as follows: basalt fiber is placed in a sodium hydroxide solution and soaked at 60-64℃ for 1.0-1.2 hours. After being taken out, it is washed and dried to obtain the alkali-impregnated fiber. The basalt fibers have a length of 3-5 mm and a diameter of 10-15 μm.

6. The method for preparing a chlorinated polyvinyl chloride sheet according to claim 1, characterized in that, In the step of preparing the reinforcing material, the alumina sol is prepared by adding 10-15g of aluminum isopropoxide to 90-100mL of isopropanol I, stirring at 58-60℃ until completely dissolved, adding 2-4mL of acetylacetone, and continuing to stir for 0.8-1.0h to obtain an aluminum isopropoxide solution; mixing 6-10g of deionized water and 25-30mL of isopropanol II, stirring evenly, and adding to the aluminum isopropoxide solution, continuing to stir for 1.8-2.0h, adding 8-10wt% nitric acid solution to adjust the pH to 3.5-4.5, and allowing to stand and age at room temperature for 20-24h to obtain the alumina sol; In the aluminum isopropoxide solution, the volume-to-mass ratio of isopropanol, aluminum isopropoxide, and acetylacetone is 90-100 mL: 10-15 g: 2-4 mL. The mass-to-volume ratio of the deionized water to isopropanol di is 6-10g:25-30mL; The mass ratio of deionized water to aluminum isopropoxide is 6-10:10-15.

7. The method for preparing a chlorinated polyvinyl chloride sheet according to claim 1, characterized in that, The dry mixture preparation step is as follows: pretreated chlorinated polyvinyl chloride, reinforcing material, methyl methacrylate-butadiene-styrene copolymer (MBS), methyl methacrylate copolymer, oxidized polyethylene wax, stearic acid, and titanium dioxide are added to a mixer and stirred evenly at 700-800 rpm. The temperature is then raised to 106-110℃ and stirred for 5-6 minutes. The temperature is then lowered to 40-45℃ and stirred at 200-300 rpm for 10-15 minutes to obtain the chlorinated polyvinyl chloride dry mixture.

8. The method for preparing a chlorinated polyvinyl chloride sheet according to claim 7, characterized in that, The methyl methacrylate-butadiene-styrene copolymer MBS is manufactured by Kaneka Corporation of Japan, and its brand name is M-711. The methyl methacrylate copolymer is manufactured by Rohm and Haas and has the brand name K-400. The melting point of the oxidized polyethylene wax is 100-105℃; The mass ratio of the pretreated chlorinated polyvinyl chloride, reinforcing material, methyl methacrylate-butadiene-styrene copolymer (MBS), methyl methacrylate copolymer, oxidized polyethylene wax, stearic acid, and titanium dioxide is 100:12-18:4-5:1.8-2.3:1.2-1.5:0.8-1.0:1-2.

9. The method for preparing a chlorinated polyvinyl chloride sheet according to claim 1, characterized in that, The post-processing step involves adding the dry chlorinated polyvinyl chloride (PVC) mixture into a single-screw extruder, controlling the length-to-diameter ratio at 24-26:1, the screw speed at 20-25 rpm, the feeding zone temperature at 164-166℃, the compression zone temperature at 173-177℃, the metering zone temperature at 182-186℃, and the die head temperature at 188-193℃. The mixture then enters a three-roll calender for calendering, controlling the calender roll surface temperature at 85-90℃. After cooling to 38-40℃, the mixture is traction-cut, with the traction machine speed at 25-30 cm / min and the traction pressure at 0.10-0.15 MPa, to obtain chlorinated PVC sheets with a thickness of 4-8 mm.

10. Chlorinated polyvinyl chloride sheet prepared by the preparation method according to any one of claims 1-9.

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