Filter screen material for capillary drainage blind ditch and application of filter screen material in blind ditch construction

Abstract

The invention relates to a filter screen material for a capillary drainage blind ditch and application of the filter screen material in blind ditch construction, and belongs to the technical field of drainage materials. According to the filter screen material for the capillary drainage blind ditch, the additive is prepared by utilizing click reaction among the active polyvinyl chloride with azide groups, the modified calcium sulfate whiskers with branched alkynyl and the modified chrysotile fibers, and the additive and the polyvinyl chloride are mixed to prepare the filter screen material for the capillary drainage blind ditch. The filter screen material has good mechanical performance, acid and alkali resistance and self-cleaning performance, a filter screen made of the material can not be damaged in a complex geological environment and in a long-term use process, normal operation of a drainage function is ensured, corrosion of acid and alkali can be resisted, and the service life of the filter screen is prolonged. And the use requirements of chemical industrial parks and other environments needing to discharge acid-alkali wastewater are met. The capillary drainage plate made of the filter screen material for the capillary drainage blind ditch has good soil covering water passing capacity, filtering capacity and anti-clogging capacity.

Description

Technical Field

[0001] This invention relates to a filter screen material for capillary drainage blind drains and its application in blind drain construction, belonging to the field of drainage material technology. Background Technology

[0002] Capillary drainage blind drain filters can be categorized into capillary drainage pipes, capillary drainage belts, or capillary drainage boards. Capillary drainage filters utilize gravity to allow soil particles to settle naturally, while water molecules are forced upwards into the capillaries due to head pressure, thus achieving soil-water separation. Simultaneously, surface tension causes water to automatically form a sealed water film over the narrow channels, preventing backflow. When water begins to enter the belt, capillary action draws moisture from the soil until the capillary material is filled and sealed. Then, under gravity, the water flows towards the outlet. Upon reaching the outlet, the drop in elevation creates a siphon effect within the drainage channel, further generating negative pressure within the soil, allowing for automatic drainage and significantly increasing drainage efficiency.

[0003] Capillary drainage filters are typically made of composite soft plastic with excellent acid and alkali resistance. The plastic sheet is 2-2.5mm thick and 200-250mm wide. At regular intervals along its width, guide holes with a diameter of 1-1.2mm are made in the center. Below each hole, a groove with a width of 0.2-0.3mm is made, connecting to the hole and forming a capillary channel. In cross-section, each hole and the connecting groove form an "Ω"-shaped water absorption channel, wider at the inside and narrower at the outside. This unique structure combines four natural physical phenomena of water—capillary action, siphon, gravity, and surface tension—forming the unique filtration and drainage mechanism of the capillary drainage filter.

[0004] To cope with the combined effects of various complex stresses and environmental factors (such as acidic wastewater, alkaline wastewater, and wastewater containing silt), capillary drainage filter materials need to possess excellent mechanical properties, acid and alkali resistance, and self-cleaning properties to adapt to various working conditions and provide long-term, stable drainage, seepage prevention, and protection functions. Currently, capillary drainage filter materials typically use polyvinyl chloride (PVC) composite materials. To improve the overall performance of PVC, a large amount of inorganic solid filler is usually added. However, inorganic solid fillers are generally hydrophilic and have poor affinity with the oleophilic PVC resin, resulting in poor dispersibility and binding of the inorganic solid fillers, which affects the mechanical properties, acid and alkali resistance, and self-cleaning properties of the composite material. Summary of the Invention

[0005] The purpose of this invention is to provide a filter material for capillary drainage blind drains and its application in blind drain construction, so as to solve the problem that the poor dispersion and binding of inorganic solid fillers in the current polyvinyl chloride composite material for capillary drainage filter screens affect the mechanical properties, acid and alkali resistance and self-cleaning properties of the composite material.

[0006] This invention provides a filter screen material for capillary drainage blind drains, which is prepared by a method comprising the following steps:

[0007] (1) Hydroxylated calcium sulfate whiskers were modified with a functional silane coupling agent to obtain functional modified calcium sulfate whiskers; serpentine fibers were modified with a functional silane coupling agent to obtain functional modified serpentine fibers; the chemical structure of the functional silane coupling agent is as follows:

[0008] ;

[0009] (2) Polyvinyl chloride is subjected to an azide reaction to obtain azide-based polyvinyl chloride; the temperature of the azide reaction is 50~55℃ and the time is 3~4h;

[0010] (3) The azide groups in the azide-modified polyvinyl chloride are reacted with the alkynyl groups in the functional modified calcium sulfate whiskers and the functional modified serpentine fiber to obtain the functional additive.

[0011] (4) Polyvinyl chloride and functional additives are melt-extruded and granulated to obtain filter screen material for capillary drainage blind drain.

[0012] Preferably, the method for modifying hydroxylated calcium sulfate whiskers with a functional silane coupling agent is as follows: Hydroxylated calcium sulfate whiskers, ethanol, and water are mixed in a mass ratio of 3:45~50:5~7, and then acetic acid and the functional silane coupling agent are added sequentially. The mixture is reacted at 50~60℃ for 5~7 hours to obtain functionally modified calcium sulfate whiskers; the mass ratio of acetic acid to ethanol is 1:12~15, and the mass ratio of the functional silane coupling agent to hydroxylated calcium sulfate whiskers is 1.2~1.5:1. The preparation method of the hydroxylated calcium sulfate whiskers is as follows: Sodium hydroxide, sodium sulfate, calcium sulfate whiskers, and water are mixed to obtain a reaction solution. The concentration of sodium hydroxide in the reaction solution is 1~1.2 mol / L, the concentration of sodium sulfate is 0.1~0.2 mol / L, and the mass fraction of calcium sulfate whiskers is 10~13%. The mixture is stirred at room temperature for 3~4 hours to obtain hydroxylated calcium sulfate whiskers.

[0013] Preferably, the calcium sulfate whiskers have an average length of 20-30 μm and an average diameter of 1-3 μm.

[0014] Preferably, the method for modifying serpentine fiber with a functional silane coupling agent is as follows: serpentine fiber with a mass ratio of 2.5:45~50:5~7 is mixed evenly, and then acetic acid and functional silane coupling agent are added sequentially. The mixture is reacted at 50~60℃ for 5~7h to obtain functionally modified serpentine fiber.

[0015] Preferably, the serpentine fiber has an average length of 6-8 μm and an average diameter of 20-35 nm.

[0016] Preferably, the method for performing an azide reaction on polyvinyl chloride is as follows: polyvinyl chloride, sodium azide, and tetrabutylammonium bromide are mixed and reacted in a solvent, wherein the mass ratio of polyvinyl chloride, sodium azide, and tetrabutylammonium bromide is 1:1.2~1.3:0.2~0.3.

[0017] Preferably, the number average molecular weight of the polyvinyl chloride in steps (2) and (4) is independently 60,000 to 70,000.

[0018] Preferably, the click reaction method is as follows: Azide-modified polyvinyl chloride, functionally modified calcium sulfate whiskers, and functionally modified serpentine fibers are mixed in a solvent, then cuprous bromide and pentamethyldiethylenetriamine are added, and the mixture is reacted at room temperature for 12-15 hours to obtain the functional additive; the mass ratio of the functionally modified calcium sulfate whiskers to the functionally modified serpentine fibers is 1-2:3-5, the ratio of the sum of the molar amounts of alkynyl groups in the functionally modified calcium sulfate whiskers and functionally modified serpentine fibers to the molar amounts of azido groups in the azide-modified polyvinyl chloride is 1:1, and the molar amounts of azido groups, cuprous bromide, and pentamethyldiethylenetriamine in the azide-modified polyvinyl chloride are 1:0.5-0.6:0.5-0.6.

[0019] Preferably, the mass ratio of polyvinyl chloride to functional additives in step (4) is 100:30~40, and the melt extrusion temperature is 190~200℃.

[0020] The present invention also provides the application of the filter screen material for capillary drainage blind drains as described above in the construction of blind drains.

[0021] Preferably, the application includes the following steps: making a capillary drainage board from the filter mesh material of the capillary drainage blind ditch, and then using the capillary drainage board as a drainage material in the construction of the blind ditch.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The filter material for capillary drainage blind drains of the present invention is made by synthesizing active polyvinyl chloride with azide groups and modified calcium sulfate whiskers and modified serpentine fibers with branched alkyne groups, and by using a click reaction to bond the calcium sulfate whiskers and serpentine fibers together with the polyvinyl chloride molecular chain through triazole groups, forming a functional additive with calcium sulfate whiskers, serpentine fibers and polyvinyl chloride molecular chains. The functional additive is added to the polyvinyl chloride main resin. The polyvinyl chloride molecular chains in the functional additive can improve its affinity with the polyvinyl chloride main resin and improve the dispersion uniformity of calcium sulfate whiskers and serpentine fibers in the mixture. Moreover, the calcium sulfate whiskers and serpentine fibers in the functional additive are chemically bonded to the polyvinyl chloride molecular chain, which can further improve the orderly distribution of calcium sulfate whiskers and serpentine fibers. The uniform and firmly dispersed calcium sulfate whiskers and serpentine fibers in the composite material can effectively improve the mechanical strength and acid and alkali resistance of the polyvinyl chloride resin. In addition, the organosilicon segments and triazole groups bonded to the surfaces of calcium sulfate whiskers and serpentine fibers can effectively improve the mechanical strength and acid and alkali resistance of the composite material. Furthermore, the branched alkyl groups in the silane coupling agent bonded to the surfaces of calcium sulfate whiskers and serpentine fibers can effectively improve the hydrophobicity of the material, thereby improving its acid and alkali resistance and self-cleaning properties.

[0024] (2) In the filter material for capillary drainage blind drain of the present invention, since the functional modified calcium sulfate whiskers and the functional modified serpentine fibers have different lengths and diameters, the two can be used in combination to more uniformly and densely graft polyvinyl chloride molecular chains, and the prepared functional additives can better improve the comprehensive performance of the composite material.

[0025] (3) The filter screen material for capillary drainage blind drains of the present invention has good mechanical properties, acid and alkali resistance, and self-cleaning properties. The filter screen made of this material can remain undamaged in complex geological environments and during long-term use, ensuring the normal operation of the drainage function. It can also resist acid and alkali corrosion, meeting the usage requirements of chemical industrial parks and other environments that require the discharge of acid and alkali wastewater. The capillary drainage board made of the filter screen material for capillary drainage blind drains of the present invention has good soil covering and water passage capacity, filtration capacity, and anti-clogging capacity. Attached Figure Description

[0026] Figure 1 The 1H NMR spectrum of the dichlorosiloxane compound prepared in Example 1 of this invention;

[0027] Figure 2 The above is the 1H NMR spectrum of the functional silane coupling agent prepared in Example 1 of this invention. Detailed Implementation

[0028] The following examples are intended to further illustrate the content of the present invention, rather than to limit the scope of protection of the present invention.

[0029] Example 1

[0030] The filter material for the capillary drainage blind ditch in this embodiment is prepared by a method including the following steps:

[0031] (1) Diethylchlorosilane was added to toluene and stirred until homogeneous to obtain a 12% (w / w) diethylchlorosilane solution; 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane was added to toluene and stirred until homogeneous to obtain a 15% (w / w) 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane solution; the diethylchlorosilane solution was added to a reaction vessel, nitrogen gas was introduced into the reaction vessel, and then a solid platinum catalyst was added to the reaction vessel. The temperature was raised to 85°C, and the 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane solution was added dropwise to the reaction vessel under stirring. After the addition was completed, the reaction was stirred for 4 hours. The solvent was removed by pressure distillation to obtain a concentrated solution. The concentrated solution was purified by column chromatography using petroleum ether and ethyl acetate in a volume ratio of 4:5 to obtain a dichlorosiloxane compound. The molar ratio of 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane to diethylchlorosilane was 1:2.1. The mass ratio of platinum to diethylchlorosilane in the solid platinum catalyst was 0.0001:1. The solid platinum catalyst was prepared as follows: 5g of dried 4A molecular sieve was added to 2mL of 0.05mol / L isopropanol solution of chloroplatinic acid, stirred evenly, and the solvent was removed by vacuum distillation. After drying, a solid platinum catalyst with a platinum mass fraction of 0.4% was obtained.

[0032] The chemical structure of diethylchlorosilane is shown below:

[0033] ;

[0034] The 1H NMR spectrum of dichlorosiloxane compounds is shown below. Figure 1 As shown, the chemical structure is as follows:

[0035] .

[0036] (2) Add alkynyl alcohols and toluene in a mass ratio of 1:4 to a reaction vessel, then introduce nitrogen gas into the reaction vessel and heat to 75°C. Under stirring, add a 15% (w / w) toluene solution of dichlorosiloxane compound to the reaction vessel dropwise. After the addition is complete, add triethylamine to the reaction vessel and continue stirring for 8 hours. Filter the solution and remove toluene by vacuum distillation to obtain a concentrated solution. Purify the concentrated solution by column chromatography using petroleum ether, ethyl acetate and dichloromethane in a volume ratio of 4:5:3 to obtain a functional silane coupling agent. Among them, the alkynyl alcohol is dimethylhexynyl alcohol, and the molar ratio of alkynyl alcohol, dichlorosiloxane compound and triethylamine is 2.2:1:2.8. The chemical structure of dimethylhexynyl alcohol is as follows:

[0037] .

[0038] The 1H NMR spectrum of the functional silane coupling agent is shown below. Figure 2 As shown, the chemical structure is as follows:

[0039] .

[0040] (3) Sodium hydroxide, sodium sulfate and calcium sulfate whiskers (the average length of calcium sulfate whiskers is 20 μm and the average diameter is 1 μm) are added to the reaction vessel, and then deionized water is added to the reaction vessel to obtain a reaction solution. The concentration of sodium hydroxide in the reaction solution is 1 mol / L, the concentration of sodium sulfate is 0.1 mol / L, and the mass fraction of calcium sulfate whiskers is 10%. The reaction is stirred at room temperature for 3 h, filtered, and the filter cake is washed with deionized water until the washing solution is neutral. After drying, hydroxylated calcium sulfate whiskers are obtained.

[0041] Hydroxylated calcium sulfate whiskers, ethanol, and deionized water in a mass ratio of 3:45:5 were added to a reaction vessel and stirred until homogeneous. Then, acetic acid (acetic acid to ethanol in a mass ratio of 1:12) was added, followed by the addition of a functional silane coupling agent (functional silane coupling agent to hydroxylated calcium sulfate whiskers in a mass ratio of 1.2:1). After stirring until homogeneous, the mixture was heated to 50°C and stirred for 5 hours. The mixture was then filtered, and the filter cake was washed successively with toluene and ethanol. After drying, functionalized calcium sulfate whiskers were obtained.

[0042] (4) Add serpentine fiber (average length of 6 μm and average diameter of 20 nm), ethanol and deionized water in a mass ratio of 2.5:45:5 to a reaction vessel and stir evenly. Then add acetic acid (mass ratio of acetic acid to ethanol is 1:12) and then add functional silane coupling agent (mass ratio of functional silane coupling agent to serpentine fiber is 1.8:1). After stirring evenly, heat to 50°C and stir for 5 h. Filter and wash the filter cake with toluene and ethanol in sequence. After drying, functional modified serpentine fiber is obtained.

[0043] (5) Add polyvinyl chloride powder (the number average molecular weight of polyvinyl chloride is 60,000) and anhydrous tetrahydrofuran to a reaction vessel and stir until the polyvinyl chloride is fully dissolved to obtain a polyvinyl chloride solution. Then add sodium azide and tetrabutylammonium bromide to the reaction vessel, stir evenly, heat to 50°C, stir and react for 3 hours. Then pour the material in the reaction vessel into a mixed solvent of methanol and water with a volume ratio of 2:1, stir for 30 minutes, filter, wash the filter cake with deionized water and methanol in turn, and dry to obtain azide-based polyvinyl chloride. The mass ratio of polyvinyl chloride to tetrahydrofuran is 1:12, and the mass ratio of polyvinyl chloride, sodium azide and tetrabutylammonium bromide is 1:1.2:0.2.

[0044] (6) Add azido-modified polyvinyl chloride and anhydrous tetrahydrofuran in a mass ratio of 1:30 to a reaction vessel and stir until the azido-modified polyvinyl chloride is fully dissolved. Then, introduce nitrogen gas into the reaction vessel, add functional modified calcium sulfate whiskers and functional modified serpentine fibers to the reaction vessel, stir evenly, add cuprous bromide and pentamethyldiethylenetriamine to the reaction vessel, stir and react at room temperature for 12 hours, filter, wash the filter cake with deionized water, ethanol and tetrahydrofuran respectively, and dry to obtain functional additives; wherein, the mass ratio of functional modified calcium sulfate whiskers and functional modified serpentine fibers is 1:3, the ratio of the sum of the molar amounts of alkynyl groups in functional modified calcium sulfate whiskers and functional modified serpentine fibers to the molar amounts of azido groups in azido-modified polyvinyl chloride is 1:1, and the molar amounts of azido groups, cuprous bromide and pentamethyldiethylenetriamine in azido-modified polyvinyl chloride are 1:0.5:0.5. In this embodiment, the molar content of alkynyl groups per unit mass of functionally modified calcium sulfate whiskers and functionally modified serpentine fibers was determined by elemental analysis, and the molar content of azido groups per unit mass of azide-modified polyvinyl chloride was determined by infrared analysis.

[0045] (7) After mixing polyvinyl chloride powder (the number average molecular weight of polyvinyl chloride is 60,000) and functional additives at a mass ratio of 100:30, add them to a twin-screw extruder and melt-extrude and granulate at 190°C to obtain a filter screen material for capillary drainage blind drain.

[0046] Example 2

[0047] The filter material for the capillary drainage blind ditch in this embodiment is prepared by a method including the following steps:

[0048] (1) Diethylchlorosilane was added to toluene and stirred until homogeneous to obtain a 13% (w / w) diethylchlorosilane solution; 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane was added to toluene and stirred until homogeneous to obtain a 16% (w / w) 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane solution; the diethylchlorosilane solution was added to a reaction vessel, nitrogen gas was introduced into the reaction vessel, and then a solid platinum catalyst was added to the reaction vessel. The temperature was raised to 88°C, and the 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane solution was added dropwise to the reaction vessel under stirring. After the addition was completed, the reaction was stirred for 5 hours. The solvent was removed by pressure distillation to obtain a concentrated solution. The concentrated solution was purified by column chromatography using petroleum ether and ethyl acetate in a volume ratio of 4:5 to obtain a dichlorosiloxane compound. The molar ratio of 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane to diethylchlorosilane was 1:2.2. The mass ratio of platinum to diethylchlorosilane in the solid platinum catalyst was 0.0002:1. The solid platinum catalyst was prepared as follows: 5g of dried 4A molecular sieve was added to 2mL of 0.05mol / L isopropanol solution of chloroplatinic acid, stirred evenly, and the solvent was removed by vacuum distillation. After drying, a solid platinum catalyst with a platinum mass fraction of 0.4% was obtained.

[0049] The structure of diethylchlorosilane is shown below:

[0050] ;

[0051] The chemical structure of dichlorosiloxane compounds is as follows:

[0052] .

[0053] (2) Add alkynyl alcohols and toluene in a mass ratio of 1:5 to a reaction vessel, then introduce nitrogen gas into the reaction vessel and heat to 77°C. Under stirring, add a 16% (w / w) toluene solution of dichlorosiloxane compound to the reaction vessel dropwise. After the addition is complete, add triethylamine to the reaction vessel and continue stirring for 9 hours. Filter the solution and remove toluene by vacuum distillation to obtain a concentrated solution. Purify the concentrated solution by column chromatography using petroleum ether, ethyl acetate and dichloromethane in a volume ratio of 4:5:3 to obtain a functional silane coupling agent. Among them, the alkynyl alcohol is dimethylhexynyl alcohol, and the molar ratio of alkynyl alcohol, dichlorosiloxane compound and triethylamine is 2.3:1:2.9. The chemical structure of dimethylhexynyl alcohol is as follows:

[0054] .

[0055] The chemical structure of the functional silane coupling agent is as follows:

[0056] .

[0057] (3) Sodium hydroxide, sodium sulfate and calcium sulfate whiskers (the average length of calcium sulfate whiskers is 25 μm and the average diameter is 2 μm) are added to the reaction vessel, and then deionized water is added to the reaction vessel to obtain a reaction solution. The concentration of sodium hydroxide in the reaction solution is 1.1 mol / L, the concentration of sodium sulfate is 0.1 mol / L, and the mass fraction of calcium sulfate whiskers is 12%. The reaction is stirred at room temperature for 4 h, filtered, and the filter cake is washed with deionized water until the washing solution is neutral. After drying, hydroxylated calcium sulfate whiskers are obtained.

[0058] Hydroxylated calcium sulfate whiskers, ethanol, and deionized water in a mass ratio of 3:48:6 were added to a reaction vessel and stirred until homogeneous. Then, acetic acid (acetic acid to ethanol in a mass ratio of 1:13) was added, followed by the addition of a functional silane coupling agent (functional silane coupling agent to hydroxylated calcium sulfate whiskers in a mass ratio of 1.3:1). After stirring until homogeneous, the mixture was heated to 55°C and stirred for 6 hours. The mixture was then filtered, and the filter cake was washed successively with toluene and ethanol. After drying, functionalized calcium sulfate whiskers were obtained.

[0059] (4) Add serpentine fiber (average length of 7 μm and average diameter of 30 nm), ethanol and deionized water in a mass ratio of 2.5:48:6 to a reaction vessel and stir until homogeneous. Then add acetic acid (mass ratio of acetic acid to ethanol is 1:13) and add functional silane coupling agent (mass ratio of functional silane coupling agent to serpentine fiber is 1.9:1) to the reaction vessel. After stirring until homogeneous, heat to 55 °C and stir for 6 h. Filter and wash the filter cake with toluene and ethanol in sequence. After drying, functional modified serpentine fiber is obtained.

[0060] (5) Add polyvinyl chloride powder (the number average molecular weight of polyvinyl chloride is 65,000) and anhydrous tetrahydrofuran to the reactor and stir until the polyvinyl chloride is fully dissolved to obtain a polyvinyl chloride solution. Then add sodium azide and tetrabutylammonium bromide to the reactor, stir evenly, heat to 52°C, stir and react for 4 hours. Then pour the material in the reactor into a mixed solvent of methanol and water with a volume ratio of 2:1, stir for 30 minutes and filter. Wash the filter cake with deionized water and methanol in turn, and dry to obtain azide-based polyvinyl chloride. The mass ratio of polyvinyl chloride to tetrahydrofuran is 1:13, and the mass ratio of polyvinyl chloride, sodium azide and tetrabutylammonium bromide is 1:1.2:0.3.

[0061] (6) Add azido-modified polyvinyl chloride and anhydrous tetrahydrofuran in a mass ratio of 1:32 to a reaction vessel and stir until the azido-modified polyvinyl chloride is fully dissolved. Then, introduce nitrogen gas into the reaction vessel, add functional modified calcium sulfate whiskers and functional modified serpentine fibers to the reaction vessel, stir evenly, add cuprous bromide and pentamethyldiethylenetriamine to the reaction vessel, stir and react at room temperature for 13 hours, filter, wash the filter cake with deionized water, ethanol and tetrahydrofuran respectively, and dry to obtain functional additives; wherein, the mass ratio of functional modified calcium sulfate whiskers and functional modified serpentine fibers is 2:3, the ratio of the sum of the molar amounts of alkynyl groups in functional modified calcium sulfate whiskers and functional modified serpentine fibers to the molar amounts of azido groups in azido-modified polyvinyl chloride is 1:1, and the molar amounts of azido groups, cuprous bromide and pentamethyldiethylenetriamine in azido-modified polyvinyl chloride are 1:0.6:0.5.

[0062] (7) After mixing polyvinyl chloride powder (the number average molecular weight of polyvinyl chloride is 70,000) and functional additives at a mass ratio of 100:35, add them to a twin-screw extruder and melt-extrude and granulate at 195°C to obtain a filter screen material for capillary drainage blind drain.

[0063] Example 3

[0064] The filter material for the capillary drainage blind ditch in this embodiment is prepared by a method including the following steps:

[0065] (1) Diethylchlorosilane was added to toluene and stirred until homogeneous to obtain a 14% (w / w) diethylchlorosilane solution; 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane was added to toluene and stirred until homogeneous to obtain an 18% (w / w) 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane solution; the diethylchlorosilane solution was added to a reaction vessel, nitrogen gas was introduced into the reaction vessel, and then a solid platinum catalyst was added to the reaction vessel. The temperature was raised to 90°C, and the 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane solution was added dropwise to the reaction vessel under stirring. After the addition was completed, the reaction was stirred for 6 hours. The solvent was removed by pressure distillation to obtain a concentrated solution. The concentrated solution was purified by column chromatography using petroleum ether and ethyl acetate in a volume ratio of 4:5 to obtain a dichlorosiloxane compound. The molar ratio of 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane to diethylchlorosilane was 1:2.3. The mass ratio of platinum to diethylchlorosilane in the solid platinum catalyst was 0.0003:1. The solid platinum catalyst was prepared as follows: 5g of dried 4A molecular sieve was added to 2mL of 0.05mol / L isopropanol solution of chloroplatinic acid, stirred evenly, and the solvent was removed by vacuum distillation. After drying, a solid platinum catalyst with a platinum mass fraction of 0.4% was obtained.

[0066] The chemical structure of diethylchlorosilane is shown below:

[0067] ;

[0068] The chemical structure of dichlorosiloxane compounds is as follows:

[0069] .

[0070] (2) Add alkynyl alcohols and toluene in a mass ratio of 1:5 to a reaction vessel, then introduce nitrogen gas into the reaction vessel and heat to 80°C. Under stirring, add a toluene solution of 18% dichlorosiloxane compound by mass dropwise to the reaction vessel. After the addition is complete, add triethylamine to the reaction vessel and continue stirring for 10 hours. Filter the solution and remove toluene by vacuum distillation to obtain a concentrated solution. Purify the concentrated solution by column chromatography using petroleum ether, ethyl acetate and dichloromethane in a volume ratio of 4:5:3 to obtain a functional silane coupling agent. Among them, the alkynyl alcohol is dimethylhexynyl alcohol, and the molar ratio of alkynyl alcohol, dichlorosiloxane compound and triethylamine is 2.5:1:3. The chemical structure of dimethylhexynyl alcohol is as follows:

[0071] .

[0072] The chemical structure of the functional silane coupling agent is as follows:

[0073] .

[0074] (3) Sodium hydroxide, sodium sulfate and calcium sulfate whiskers (the average length of calcium sulfate whiskers is 30 μm and the average diameter is 3 μm) were added to the reaction vessel, and then deionized water was added to the reaction vessel to obtain a reaction solution. The concentration of sodium hydroxide in the reaction solution was 1.2 mol / L, the concentration of sodium sulfate was 0.2 mol / L, and the mass fraction of calcium sulfate whiskers was 13%. The reaction was stirred at room temperature for 4 h, filtered, and the filter cake was washed with deionized water until the washing solution was neutral. After drying, hydroxylated calcium sulfate whiskers were obtained.

[0075] Hydroxylated calcium sulfate whiskers, ethanol, and deionized water in a mass ratio of 3:50:7 were added to a reaction vessel and stirred until homogeneous. Then, acetic acid (acetic acid to ethanol in a mass ratio of 1:15) was added, followed by the addition of a functional silane coupling agent (functional silane coupling agent to hydroxylated calcium sulfate whiskers in a mass ratio of 1.5:1). After stirring until homogeneous, the mixture was heated to 60°C and stirred for 7 hours. The mixture was then filtered, and the filter cake was washed successively with toluene and ethanol. After drying, functionalized calcium sulfate whiskers were obtained.

[0076] (4) Add serpentine fiber (average length of serpentine fiber is 8 μm and average diameter is 35 nm) in a mass ratio of 2.5:50:7, ethanol and deionized water to a reaction vessel and stir evenly. Then add acetic acid (mass ratio of acetic acid to ethanol is 1:15) and then add functional silane coupling agent (mass ratio of functional silane coupling agent to serpentine fiber is 2:1). After stirring evenly, heat to 60°C and stir for 7 h. Filter and wash the filter cake with toluene and ethanol in sequence. After drying, functional modified serpentine fiber is obtained.

[0077] (5) Add polyvinyl chloride powder (the number average molecular weight of polyvinyl chloride is 70,000) and anhydrous tetrahydrofuran to a reaction vessel and stir until the polyvinyl chloride is fully dissolved to obtain a polyvinyl chloride solution. Then add sodium azide and tetrabutylammonium bromide to the reaction vessel, stir evenly, heat to 55°C, stir and react for 4 hours. Then pour the material in the reaction vessel into a mixed solvent of methanol and water with a volume ratio of 2:1, stir for 30 minutes and filter. Wash the filter cake with deionized water and methanol in turn, and dry to obtain azide-based polyvinyl chloride. The mass ratio of polyvinyl chloride to tetrahydrofuran is 1:14, and the mass ratio of polyvinyl chloride, sodium azide and tetrabutylammonium bromide is 1:1.3:0.3.

[0078] (6) Add azido-modified polyvinyl chloride and anhydrous tetrahydrofuran in a mass ratio of 1:35 to a reaction vessel and stir until the azido-modified polyvinyl chloride is fully dissolved. Then, introduce nitrogen gas into the reaction vessel, add functional modified calcium sulfate whiskers and functional modified serpentine fibers to the reaction vessel, stir evenly, add cuprous bromide and pentamethyldiethylenetriamine to the reaction vessel, stir and react at room temperature for 15 h, filter, wash the filter cake with deionized water, ethanol and tetrahydrofuran respectively, and dry to obtain functional additives; wherein, the mass ratio of functional modified calcium sulfate whiskers and functional modified serpentine fibers is 2:5, the ratio of the sum of the molar amounts of alkynyl groups in functional modified calcium sulfate whiskers and functional modified serpentine fibers to the molar amounts of azido groups in azido-modified polyvinyl chloride is 1:1, and the molar amounts of azido groups, cuprous bromide and pentamethyldiethylenetriamine in azido-modified polyvinyl chloride are 1:0.6:0.6.

[0079] (7) After mixing polyvinyl chloride powder (the number average molecular weight of polyvinyl chloride is 70,000) and functional additives at a mass ratio of 100:40, add them to a twin-screw extruder and melt-extrude and granulate at 200°C to obtain a filter screen material for capillary drainage blind drain.

[0080] Comparative Example 1

[0081] The only difference between the capillary drainage blind drain filter material of this comparative example and the capillary drainage blind drain filter material of Example 1 is that in step (1) of the preparation of the capillary drainage blind drain filter material of this comparative example, diethylchlorosilane is replaced with dimethylchlorosilane.

[0082] Comparative Example 2

[0083] The only difference between the capillary drainage blind drain filter material of this comparative example and the capillary drainage blind drain filter material of Example 1 is that the alkynol compound in step (2) of the preparation of the capillary drainage blind drain filter material of this comparative example is 3-methyl-1-pentyn-3-ol, and the chemical structure of 3-methyl-1-pentyn-3-ol is as follows:

[0084] .

[0085] Comparative Example 3

[0086] The only difference between the capillary drainage blind drain filter material of this comparative example and the capillary drainage blind drain filter material of Example 1 is that the alkynol compound in step (2) of the preparation of the capillary drainage blind drain filter material of this comparative example is propynol propoxylate, and the chemical structure of propynol propoxylate is as follows:

[0087] .

[0088] Comparative Example 4

[0089] The only difference between the capillary drainage blind drain filter material of this comparative example and the capillary drainage blind drain filter material of Example 1 is that the alkynyl alcohol compound in step (2) of the preparation of the capillary drainage blind drain filter material of this comparative example is 6-heptynol, and the chemical structure of 6-heptynol is as follows:

[0090] .

[0091] Comparative Example 5

[0092] The only difference between the capillary drainage blind drain filter material of this comparative example and the capillary drainage blind drain filter material of Example 1 is that the amount of functional modified calcium sulfate whiskers used in step (6) of the preparation of the capillary drainage blind drain filter material of this comparative example is 0.

[0093] Comparative Example 6

[0094] The only difference between the capillary drainage blind drain filter material of this comparative example and the capillary drainage blind drain filter material of Example 1 is that the amount of functional modified serpentine fiber used in step (6) of the preparation of the capillary drainage blind drain filter material of this comparative example is 0.

[0095] Comparative Example 7

[0096] The only difference between the capillary drainage blind drain filter material of this comparative example and the capillary drainage blind drain filter material of Example 1 is that the preparation method of the functional additive in step (6) of the preparation of the capillary drainage blind drain filter material of this comparative example is as follows:

[0097] Add azido-modified polyvinyl chloride (PVC) and anhydrous tetrahydrofuran in a mass ratio of 1:30 to a reaction vessel and stir until the PVC is fully dissolved. Then, nitrogen gas is introduced into the reaction vessel, followed by the addition of functionally modified calcium sulfate whiskers. After stirring evenly, cuprous bromide and pentamethyldiethylenetriamine are added to the reaction vessel and stirred at room temperature for 12 hours. The mixture is then filtered, and the filter cake is washed with deionized water, ethanol, and tetrahydrofuran, respectively. After drying, additive A is obtained. The molar ratio of alkynyl groups in the functionally modified calcium sulfate whiskers to the molar ratio of azido groups in the PVC is 1:1, and the molar ratio of azido groups, cuprous bromide, and pentamethyldiethylenetriamine in the PVC is 1:0.5:0.5.

[0098] Add azido-modified polyvinyl chloride (PVC) and anhydrous tetrahydrofuran in a mass ratio of 1:30 to a reaction vessel and stir until the PVC is fully dissolved. Then, nitrogen gas is introduced into the reaction vessel, followed by the addition of functionally modified serpentine fiber. After stirring evenly, cuprous bromide and pentamethyldiethylenetriamine are added to the reaction vessel and stirred at room temperature for 12 hours. The mixture is then filtered, and the filter cake is washed with deionized water, ethanol, and tetrahydrofuran, respectively. After drying, additive B is obtained. The molar ratio of alkynyl groups in the functionally modified serpentine fiber to the molar ratio of azido groups in the PVC is 1:1, and the molar ratio of azido groups, cuprous bromide, and pentamethyldiethylenetriamine in the PVC is 1:0.5:0.5.

[0099] Additive A and Additive B are stirred evenly to obtain functional additives; wherein, the mass ratio of the functional modified calcium sulfate whiskers used in preparing Additive A to the mass ratio of the functional modified serpentine fiber used in preparing Additive B is 1:3.

[0100] Comparative Example 8

[0101] The only difference between the capillary drainage blind drain filter material of this comparative example and the capillary drainage blind drain filter material of Example 1 is that the chemical structure of the functional silane coupling agent in steps (3) and (4) of the preparation of the capillary drainage blind drain filter material of this comparative example is as follows:

[0102] ;

[0103] The preparation method of the functional silane coupling agent in this comparative example is as follows: magnesium powder, tetrahydrofuran, and chlorotrimethoxysilane are added to a reaction vessel, nitrogen gas is introduced into the reaction vessel, and after stirring evenly, (4-bromophenylethynyl)trimethylsilane is added. The mixture is heated to 45°C, stirred and mixed for 24 hours, filtered, and the filtrate is distilled under reduced pressure to obtain the intermediate. The molar ratio of magnesium powder, chlorotrimethoxysilane, and (4-bromophenylethynyl)trimethylsilane is 1.5:1.5:1, and the mass ratio of magnesium powder to tetrahydrofuran is 1:90.

[0104] Potassium hydroxide, methanol, and an intermediate were added to a reaction vessel and stirred and mixed at room temperature for 12 hours. After the reaction was completed, the mixture was filtered, and the filtrate was distilled under reduced pressure and dried to obtain a functional silane coupling agent. The molar ratio of potassium hydroxide to magnesium powder was 1:3, and the mass ratio of potassium hydroxide to methanol was 1:60.

[0105] In addition to changing the chemical structure of the functional silane coupling agent, this comparative example also adjusts the amount of functional silane coupling agent so that the alkynyl content (molar amount of alkynyl group per unit mass of functional modified calcium sulfate whiskers) of the functional modified calcium sulfate whiskers prepared in step (3) is the same as the alkynyl content of the functional modified calcium sulfate whiskers prepared in step (3) of Example 1, and the alkynyl content (molar amount of alkynyl group per unit mass of functional modified serpentine fiber) of the functional modified serpentine fiber prepared in step (4) is the same as the alkynyl content of the functional modified serpentine fiber prepared in step (4) of Example 1, thereby eliminating the influence caused by the change in alkynyl content.

[0106] Comparative Example 9

[0107] The only difference between the capillary drainage blind drain filter material of this comparative example and the capillary drainage blind drain filter material of Example 1 is that the stirring reaction time in step (5) of the preparation of the capillary drainage blind drain filter material of this comparative example is adjusted from 3h to 1h.

[0108] Comparative Example 10

[0109] The only difference between the capillary drainage blind drain filter material of this comparative example and the capillary drainage blind drain filter material of Example 1 is that the stirring reaction time in step (5) of the preparation of the capillary drainage blind drain filter material of this comparative example is adjusted from 3h to 6h.

[0110] Comparative Example 11

[0111] The only difference between the capillary drainage blind drain filter material in this comparative example and the capillary drainage blind drain filter material in Example 1 is that, in step (7) of the preparation of the capillary drainage blind drain filter material in this comparative example, the functional additive is replaced with calcium sulfate whiskers and serpentine fibers in a mass ratio of 1:3. The calcium sulfate whiskers used in this comparative example are the same as those in step (3) of Example 1, and the serpentine fibers used in this comparative example are the same as those in step (4) of Example 1.

[0112] Experimental Example

[0113] To examine the basic properties of the filter screen materials for capillary drainage blind drains in each embodiment and comparative example, the tensile properties, impact resistance, tear resistance, acid and alkali resistance, and self-cleaning properties of the filter screen materials for capillary drainage blind drains in each embodiment and comparative example were tested.

[0114] Tensile strength and elongation at break were tested according to the provisions of standard GB / T 1040.1-2018 "Determination of Tensile Properties of Plastics"; impact strength was tested according to the provisions of standard GB / T 1043-1-2008 "Determination of Impact Properties of Plastic Supports"; right-angle tear strength was tested according to the provisions of standard QB / T 1130-1991 "Test Method for Right-Angle Tear Properties of Plastics"; the acid resistance test method is as follows: the capillary drainage blind drains of each embodiment and comparative example were made into samples of the same size using filter mesh material, and then the samples were immersed in dilute sulfuric acid with pH=1, sealed and left to stand for 200 days, then washed with distilled water, and naturally dried before testing the impact strength K2 of the samples. The change rate of impact strength before and after immersion in dilute sulfuric acid was calculated using the formula (K1-K2) / K1×100, where K1 is the impact strength of the sample before immersion in dilute sulfuric acid; the alkali resistance test method is as follows: the capillary drainage blind drains of each embodiment and comparative example were made into samples of the same size using filter mesh material. The sample was then immersed in a sodium hydroxide solution with pH=14, sealed and left to stand for 200 days. After removal, it was washed with distilled water and air-dried. The impact strength K2 of the sample was then tested, and the rate of change of impact strength before and after immersion in the sodium hydroxide solution was calculated. The calculation formula is (K1-K2) / K1×100, where K1 is the impact strength of the sample before immersion in the sodium hydroxide solution. The self-cleaning performance test method is as follows: The capillary drainage blind drains of each embodiment and comparative example were made into test plates with the same size and surface condition using filter screen material. The surface of each test plate was divided into two parts with equal left and right areas, named part X and part Y, respectively. A layer with a density of 0.1 g / cm³ was covered on the surface of part X. 2The chalk dust was then removed, and the test board was tilted at a 5-degree angle. Water mist was then sprayed vertically and evenly downwards from a distance of 20cm from the top of the test board. Both the X and Y sections of the test board surface were sprayed with water mist in the same manner to simulate drainage washing the surface. The test board was then placed horizontally in a drying oven for drying. After drying, the reflectance coefficients of the X and Y sections of the test board surface were measured, and the values ​​were f0 and f1 respectively. X and f Y Calculate (f) Y -f X ) / F Y The rate of change of the reflection coefficient is obtained, and the rate of change of the reflection coefficient is used to characterize the self-cleaning performance of the material.

[0115] The test results of tensile properties, impact resistance, tear resistance, acid and alkali resistance and self-cleaning properties of the filter screen materials for capillary drainage blind drains in each embodiment and comparative example are shown in Table 1.

[0116] Table 1. Comprehensive Performance of Filter Screen Materials for Capillary Drainage Drains

[0117] Filter material Tensile strength (MPa) Elongation at break (%) <![CDATA[Impact strength (kJ / m 2 )]]> Right-angle tear strength (kN / m) Acid resistance (%) Alkali resistance (%) Self-cleaning performance (%) Example 1 58.4 259.7 15.6 81.4 3.5 4.7 1.4 Example 2 56.9 255.6 14.8 80.7 4.1 4.9 1.7 Example 3 57.5 252.4 15.4 81.1 3.7 4.5 1.5 Comparative Example 1 34.1 163.8 8.2 58.5 27.2 29.8 7.2 Comparative Example 2 29.7 159.6 6.6 61.3 31.1 34.9 7.9 Comparative Example 3 31.8 178.4 7.1 62.7 36.8 34.7 7.6 Comparative Example 4 30.6 182.1 6.9 60.9 33.4 36.1 8.8 Comparative Example 5 29.5 173.5 6.6 57.1 29.6 31.5 6.7 Comparative Example 6 32.4 177.1 7.3 56.8 31.4 32.8 7.1 Comparative Example 7 31.2 175.8 7.0 57.3 30.5 31.9 7.2 Comparative Example 8 27.6 145.2 6.4 54.3 36.3 39.4 9.0 Comparative Example 9 32.7 179.7 7.7 61.9 21.5 25.3 7.8 Comparative Example 10 33.4 183.2 8.0 58.6 23.1 27.0 8.2 Comparative Example 11 24.8 152.0 5.5 49.6 38.5 42.6 8.0

[0118] As shown in Table 1, the filter screen material for capillary drainage blind drains of the present invention possesses excellent mechanical properties, acid and alkali resistance, and self-cleaning properties. Therefore, the filter screen made from the filter screen material for capillary drainage blind drains of the present invention can remain undamaged in complex geological environments and during long-term use, ensuring the normal operation of the drainage function. Furthermore, it can resist acid and alkali corrosion, meeting the usage requirements of environments such as chemical industrial parks that require the discharge of acidic and alkaline wastewater.

[0119] As can be seen from Example 1 and Comparative Example 1, when diethylchlorosilane used in the preparation of functional silane coupling agents is replaced with dimethylchlorosilane, the branched alkyl chains in the coupling agent are reduced, resulting in a decrease in steric hindrance and hydrophobicity of the functional silane coupling agent, which in turn leads to changes in the properties of the material.

[0120] As can be seen from Example 1 and Comparative Examples 2-4, when the alkynyl alcohols used in the preparation of functional silane coupling agents are replaced with straight-chain alcohols or alcohols containing ether bonds, the branched alkyl chains in the coupling agent are reduced or ether bonds with poor stability are introduced, resulting in a decrease in the acid and alkali resistance and self-cleaning performance of the material.

[0121] As can be seen from Example 1 and Comparative Examples 5-7, when functional modified calcium sulfate whiskers or functional modified serpentine fibers are used alone, the overall performance of the composite material decreases. This is because functional modified calcium sulfate whiskers and functional modified serpentine fibers have different lengths and diameters. When used in combination, they can more uniformly and densely graft polyvinyl chloride molecular chains, and the prepared functional additives can better improve the overall performance of the composite material.

[0122] As can be seen from Example 1 and Comparative Example 8, when using unbranched alkynyl silane coupling agents, although the alkynyl content of functional modified calcium sulfate whiskers and functional modified serpentine fibers remains unchanged by adjusting the amount of coupling agent, the unbranched structure makes it easy for the grafted polyvinyl chloride molecular chains to become physically entangled and the steric hindrance to decrease. This leads to a decrease in the uniformity of distribution of calcium sulfate whiskers and serpentine fibers in the functional additives, thus affecting the material properties.

[0123] As can be seen from Example 1 and Comparative Examples 9-10, when adjusting the PVC azide content by changing the PVC azide reaction time, when the azide content is too low, the content of PVC grafted calcium sulfate whiskers and serpentine fibers is too low, resulting in an insignificant improvement in the additive's performance. When the azide content is too high, the content of PVC grafted calcium sulfate whiskers and serpentine fibers is too high, resulting in poor uniformity of calcium sulfate whiskers and serpentine fibers in the additive, excessive crosslinking, high brittleness, and low cohesion, thus causing a decline in the composite material's performance.

[0124] As can be seen from Example 1 and Comparative Example 11, when polyvinyl chloride (PVC) as the main resin and calcium sulfate whiskers and serpentine fibers are used, the calcium sulfate whiskers and serpentine fibers are not pre-bonded to the PVC molecular chain through chemical bonds, and there is a lack of traction from the PVC molecular chain. This results in poor affinity between the calcium sulfate whiskers and serpentine fibers and the main resin, as well as poor distribution in the composite material, leading to a deterioration in the performance of the composite material.

[0125] Example of effect

[0126] To evaluate the actual capillary drainage effect of the filter materials for capillary drainage blind drains in each embodiment and comparative example, the filter materials for capillary drainage blind drains in each embodiment and comparative example were made into single-sided capillary drainage boards (one side is the drainage surface, and the other side is the anti-slip surface) using the same process (extrusion molding followed by perforation). The capillary drainage board had a thickness of 2.5 mm, a water collection trough width of 0.7 mm, a water collection trough partition width of 1.4 mm, a drainage hole diameter of 1 mm, and a hole bottom plate thickness of 0.9 mm. According to the standard QCR549 62017 "Railway Engineering Geosynthetics Part 6: Drainage Materials", the soil cover water flow capacity of the capillary drainage board was tested using a soil cover water flow capacity tester. During the test, a constant water head of 15 cm above the top soil layer was ensured. The soil cover water flow q1 in the first 30 minutes of the experiment, the average cement and sand content w in the first 30 minutes of the experiment, and the soil cover water flow q2 in the last 30 minutes of the experiment were recorded and calculated. The results are shown in Table 2.

[0127] Table 2. Actual capillary drainage effect of filter screen material used in capillary drainage blind drains.

[0128] Filter material <![CDATA[q1(L / h)]]> w(%) <![CDATA[q2(L / h)]]> Example 1 108.3 0.15 106.1 Example 2 104.1 0.18 101.2 Example 3 106.7 0.16 102.8 Comparative Example 1 99.4 0.73 69.2 Comparative Example 2 105.8 0.77 75.1 Comparative Example 3 102.4 0.76 72.3 Comparative Example 4 98.5 0.80 67.5 Comparative Example 5 103.9 0.69 73.6 Comparative Example 6 100.6 0.73 69.8 Comparative Example 7 104.1 0.74 73.1 Comparative Example 8 101.6 0.81 72.0 Comparative Example 9 99.8 0.76 68.6 Comparative Example 10 100.3 0.79 71.1 Comparative Example 11 103.5 0.78 72.4

[0129] As shown in Table 2, the capillary drainage boards made from the filter mesh materials of the capillary drainage blind drains in all embodiments and comparative examples have good soil covering and water permeability. However, the soil covering and water permeability of the capillary drainage boards made from the filter mesh materials of Examples 1-3 is slightly stronger than that of the capillary drainage boards made from the filter mesh materials of Comparative Examples 1-11. Furthermore, because the filter mesh materials of the capillary drainage blind drains in Examples 1-3 have better self-cleaning properties, they exhibit better filtration capabilities, significantly reduced sediment content, and minimal change in soil covering and water permeability before and after the test, demonstrating good anti-clogging capabilities.

Claims

1. A filter screen material for capillary drainage blind drains, characterized in that, Prepared by a method including the following steps: (1) Hydroxylated calcium sulfate whiskers were modified with a functional silane coupling agent to obtain functional modified calcium sulfate whiskers; serpentine fibers were modified with a functional silane coupling agent to obtain functional modified serpentine fibers; the chemical structure of the functional silane coupling agent is as follows: ； (2) Polyvinyl chloride is subjected to an azide reaction to obtain azide-based polyvinyl chloride; the temperature of the azide reaction is 50~55℃ and the time is 3~4h; (3) The azide groups in the azide-modified polyvinyl chloride are reacted with the alkynyl groups in the functional modified calcium sulfate whiskers and the functional modified serpentine fiber to obtain the functional additive. (4) Polyvinyl chloride and functional additives are melt-extruded and granulated to obtain filter screen material for capillary drainage blind drain.

2. The filter screen material for capillary drainage blind drains as described in claim 1, characterized in that, The method for modifying hydroxylated calcium sulfate whiskers with a functional silane coupling agent is as follows: Hydroxylated calcium sulfate whiskers, ethanol, and water are mixed in a mass ratio of 3:45~50:5~7, and then acetic acid and the functional silane coupling agent are added sequentially. The mixture is reacted at 50~60℃ for 5~7 hours to obtain functionally modified calcium sulfate whiskers. The mass ratio of acetic acid to ethanol is 1:12~15, and the mass ratio of the functional silane coupling agent to hydroxylated calcium sulfate whiskers is 1.2~1.5:

1. The preparation method of the hydroxylated calcium sulfate whiskers is as follows: Sodium hydroxide, sodium sulfate, calcium sulfate whiskers, and water are mixed to obtain a reaction solution. The concentration of sodium hydroxide in the reaction solution is 1~1.2 mol / L, the concentration of sodium sulfate is 0.1~0.2 mol / L, and the mass fraction of calcium sulfate whiskers is 10~13%. The mixture is stirred at room temperature for 3~4 hours to obtain hydroxylated calcium sulfate whiskers.

3. The filter screen material for capillary drainage blind drains as described in claim 2, characterized in that, The average length of the calcium sulfate whiskers is 20-30 μm, and the average diameter is 1-3 μm.

4. The filter screen material for capillary drainage blind drains as described in claim 1, characterized in that, The method for modifying serpentine fiber with functional silane coupling agent is as follows: serpentine fiber with a mass ratio of 2.5:45~50:5~7 is mixed evenly, and then acetic acid and functional silane coupling agent are added in sequence. The mixture is reacted at 50~60℃ for 5~7h to obtain functionally modified serpentine fiber.

5. The filter screen material for capillary drainage blind drains as described in claim 4, characterized in that, The average length of the serpentine fiber is 6~8μm and the average diameter is 20~35nm.

6. The filter screen material for capillary drainage blind drains as described in claim 1, characterized in that, The method for azidating polyvinyl chloride is as follows: polyvinyl chloride, sodium azide, and tetrabutylammonium bromide are mixed and reacted in a solvent, with the mass ratio of polyvinyl chloride, sodium azide, and tetrabutylammonium bromide being 1:1.2~1.3:0.2~0.

3.

7. The filter screen material for capillary drainage blind drains as described in claim 1 or 6, characterized in that, The number-average molecular weight of the polyvinyl chloride in steps (2) and (4) is independently 60,000 to 70,000.

8. The filter screen material for capillary drainage blind drains as described in any one of claims 1-6, characterized in that, The click reaction method is as follows: Azide-modified polyvinyl chloride, functionally modified calcium sulfate whiskers, and functionally modified serpentine fibers are mixed in a solvent, then cuprous bromide and pentamethyldiethylenetriamine are added, and the mixture is reacted at room temperature for 12-15 hours to obtain the functional additive; the mass ratio of the functionally modified calcium sulfate whiskers to the functionally modified serpentine fibers is 1-2:3-5, the ratio of the sum of the molar amounts of alkynyl groups in the functionally modified calcium sulfate whiskers and functionally modified serpentine fibers to the molar amounts of azido groups in the azide-modified polyvinyl chloride is 1:1, and the molar amounts of azido groups, cuprous bromide, and pentamethyldiethylenetriamine in the azide-modified polyvinyl chloride are 1:0.5-0.6:0.5-0.

6.

9. The filter screen material for capillary drainage blind drains as described in any one of claims 1-6, characterized in that, In step (4), the mass ratio of polyvinyl chloride to functional additives is 100:30~40, and the melt extrusion temperature is 190~200℃.

10. The application of a filter screen material for capillary drainage blind drains as described in any one of claims 1-9 in the construction of blind drains.

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