Large-breadth thermoplastic polyolefin impermeable geomembrane and preparation method thereof

Abstract

The invention relates to a large-breadth thermoplastic polyolefin impermeable geomembrane and a preparation method thereof, and the preparation method comprises the following steps: uniformly mixing a thermoplastic polyolefin composite material, feeding the thermoplastic polyolefin composite material into a screw extruder, melting and plasticizing the thermoplastic polyolefin composite material by the screw extruder, extruding the thermoplastic polyolefin composite material into a mold for molding at a low temperature, then pulling the thermoplastic polyolefin composite material to advance, and naturally cooling the thermoplastic polyolefin composite material in the advancing process to obtain the large-breadth thermoplastic polyolefin impermeable geomembrane. And enabling the material to complete partial crystallization process, and then entering a three-roller calender for thickness determination, thereby obtaining the large-breadth thermoplastic polyolefin impermeable geomembrane. The breadth of the prepared geomembrane is larger than or equal to 6 m, the transverse and longitudinal elongation difference is small, and the large-breadth thermoplastic polyolefin anti-seepage geomembrane can be suitable for the high-pressure water environment.

Description

Technical Field

[0001] The invention belongs to the technical field of geomembrane preparation, and in particular relates to a wide thermoplastic polyolefin anti-seepage geomembrane and a preparation method thereof. Background Art

[0002] Water conservancy and hydropower projects are livelihood projects, and water conservation, anti-seepage and loss reduction are the primary issues. However, my country has a vast territory and complex topography. The construction of water conservancy and hydropower projects depends on the actual engineering geological conditions, so anti-seepage is extremely difficult. Compared with mainstream reinforced concrete and asphalt concrete in the field of water conservancy and hydropower projects, anti-seepage geomembranes made of high molecular polymers have the advantages of good impermeability, strong seismic performance, simple construction, little impact from climate, short construction period, low cost, easy repair and replacement, etc., and have great development prospects in the anti-seepage application of hydraulic structures.

[0003] At present, the commonly used polymer geomembranes are mainly high-density polyethylene (HDPE) geomembranes, polyvinyl chloride (PVC) geomembranes and thermoplastic polyolefin elastomer (TPO) geomembranes. Among them, high-density polyethylene (HDPE) geomembranes have the disadvantages of high hardness and poor construction performance. In addition, their unidirectional elongation at break is as high as 900% or more, but their bidirectional elongation at break is only 90%, which makes it difficult to adapt to the settlement deformation and uneven base of hydraulic structures under high water pressure, and is prone to local tearing or large-area puncture, leading to concentrated leakage. Polyvinyl chloride (PVC) has excellent flexibility and good adhesion to the base layer. Its unidirectional elongation at break is only about 300%, but its bidirectional elongation at break can reach about 240%. Although its multidirectional deformation limit is more than 1 times higher than that of HDPE geomembranes, it still does not meet the requirement that the multidirectional deformation limit should exceed 650% (obtained by converting the depth-to-width ratio probability of the local depression of the cushion layer) under high water pressure. Therefore, it is not suitable for anti-seepage treatment under high water pressure environment. Thermoplastic polyolefin elastomer (TPO) geomembrane has attracted a lot of attention due to its excellent flexibility, deformation adaptability and durability. However, due to the limitation of extrusion process, its maximum width is only 3 meters at present. When the width increases, the geomembrane cloth will produce calendering orientation during three-roll calendering and thickness determination, resulting in a large difference in its horizontal and vertical elongation, and obvious horizontal unevenness. For example, when tested at position 1, the longitudinal elongation is 300-400% and the horizontal elongation is 700%, while when tested at another position, the longitudinal elongation will be 500-600% and the horizontal elongation will be 700%, showing serious unevenness. At present, the anti-seepage area of ​​water conservancy and hydropower projects is large, often hundreds of thousands of square meters. Therefore, it is urgent to develop a thermoplastic polyolefin elastomer (TPO) anti-seepage geomembrane with a large width, small difference in horizontal and vertical elongation, and suitable for high-pressure water environment to improve the efficiency of anti-seepage construction. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects in the prior art and provide a wide thermoplastic polyolefin anti-seepage geomembrane and a preparation method thereof, wherein the wide thermoplastic polyolefin anti-seepage geomembrane has a width greater than or equal to 6m, has a small difference in lateral and longitudinal elongation, and can be suitable for high-pressure water environments.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for preparing a wide-width thermoplastic polyolefin anti-seepage geomembrane comprises the following steps: After the thermoplastic polyolefin composite material is mixed evenly, it is sent to a screw extruder, melted and plasticized by the screw extruder, and extruded into a mold at a low temperature to form, and then pulled forward, cooled naturally during the process of moving, so that the material completes a partial crystallization process, and then enters a three-roll calender to determine the thickness, and a wide-width thermoplastic polyolefin anti-seepage geomembrane is obtained. The material of the present invention completes a partial crystallization process, which means that after the material is formed, before entering the three-roll calender, crystallization has begun, but complete crystallization has not yet been achieved, and therefore, it is called a partial crystallization process.

[0006] As a further technical solution, after the thickness is determined by a three-roll calender, it is necessary to perform trimming, cutting to a fixed length, and rolling to obtain a thermoplastic polyolefin anti-seepage geomembrane.

[0007] As a further technical solution, the thermoplastic polyolefin composite material includes a nucleating agent; As a further technical solution, the screw extruder adopts a vacuum double exhaust single screw extruder; As a further technical solution, the temperature of the vacuum double exhaust single screw extruder is set to 170-185°C, and the melt temperature of the vacuum double exhaust single screw extruder during extrusion is ≤200°C; As a further technical solution, the temperature of the mold is set to 170-185°C; As a further technical solution, the material is naturally cooled to 120-145°C during the process so that the crystallization process of the material is completed by 40-80%. Before the material of the present invention enters the three-roll calender, it is necessary to ensure that its crystallization process is carried out to 40-80%. If the crystallization process is too little, for example, in the traditional technology, the material does not start to crystallize before entering the three-roll calender, and its crystallization process will be completely realized in the thickness determination process of the three-roll calender, which will lead to large differences in the elongation at break in the transverse and longitudinal directions of the extruded anti-seepage geomembrane, and uneven elongation at break in various parts; and if the material is completely crystallized (all crystallization processes are completed) before entering the three-roll calender, it will not be able to be shaped during the calendering process, and thus thickness control cannot be performed.

[0008] As a further technical solution, the vacuum double exhaust type single screw extruder comprises a barrel mechanism, a feed port and a discharge port arranged on the barrel mechanism, a motor for rotating the extrusion screw arranged in the barrel mechanism, and a motor for driving the extrusion screw to rotate; The extrusion screw comprises a feeding section, a first compression section, a barrier section, an exhaust section, a second compression section and a homogenizing section which are sequentially arranged according to the traveling direction of the material.

[0009] As a further technical solution, two exhaust ports are arranged on the barrel mechanism at positions corresponding to the exhaust sections of the extrusion screw, and the exhaust ports are connected to a water ring vacuum pump.

[0010] As a further technical solution, the extrusion screw is provided with a plurality of ring pins at the middle and rear part of the first compression section and the homogenization section; As a further technical solution, in the homogenization section, adjacent circle pins are staggered; in the middle and rear part of the first compression section, several circle pins are positioned correspondingly in the radial direction and are distributed in rows.

[0011] As a further technical solution, the diameter of the extrusion screw is ≥180 mm, and the aspect ratio is ≥38.

[0012] As a further technical solution, the barrel mechanism includes a protective shell, a barrel arranged in the protective shell, a heating module sleeved on the barrel, and a cooling fan arranged outside the protective shell and used to cool the heating module.

[0013] As a further technical solution, the heating module includes a heating coil wound around the outer wall of the barrel; As a further technical solution, the air outlet of the heat dissipation fan is aligned with the heating coil of the corresponding heating module.

[0014] As a further technical solution, two exhaust ports are arranged on the barrel at positions corresponding to the exhaust sections of the extrusion screw, and the exhaust ports are connected to a water ring vacuum pump.

[0015] As a further technical solution, a cooling coil is provided outside the barrel at a position corresponding to the feeding section.

[0016] As a further technical solution, according to the direction of material travel, the discharge port is also provided with an automatic screen changer, a metering pump, a static mixer, a distributor and a wide-width mold in sequence.

[0017] As a further technical solution, the thermoplastic polyolefin composite material comprises the following raw materials in parts by weight: 45-75 parts of thermoplastic polyolefin resin, 10-30 parts of toughening resin, 10-30 parts of inorganic filler, 0.3-1.3 parts of antioxidant, 0.3-1.3 parts of light stabilizer, 0.1-2 parts of nucleating agent, and 0.3-3 parts of pigment.

[0018] As a further technical solution, before the thermoplastic polyolefin composite material is fed into the screw extruder, the inorganic filler, antioxidant, light stabilizer, nucleating agent and pigment are firstly mixed evenly to obtain a powder, and then the powder is mixed evenly with a part of the thermoplastic polyolefin resin, and then fed into a twin-screw extruder for shearing, blending, extrusion and granulation, and dried and homogenized to obtain a high-concentration powder thermoplastic polyolefin masterbatch; then the high-concentration powder thermoplastic polyolefin masterbatch, the remaining thermoplastic polyolefin resin and the toughening resin are fed into the screw extruder; Alternatively, before the thermoplastic polyolefin composite material is fed into the screw extruder, the inorganic filler, antioxidant, light stabilizer, nucleating agent and pigment are first mixed evenly to obtain powder, and the thermoplastic polyolefin resin and toughening resin are mixed evenly to obtain pellets; the powder and pellets are then fed into a twin-screw extruder for shear blending, extrusion and granulation, dried and homogenized to obtain thermoplastic polyolefin masterbatch, and then the thermoplastic polyolefin masterbatch is fed into the screw extruder.

[0019] As a further technical solution, the content of powder in the high-concentration powder thermoplastic polyolefin masterbatch is 40-80%.

[0020] As a further technical solution, the setting temperature of the twin-screw extruder is 165-190°C, and the melt temperature of the twin-screw extruder during extrusion is ≤230°C.

[0021] As a further technical solution, the thermoplastic polyolefin resin includes one or more of C3 / C2 / C4 terpolymer polypropylene (reaction grade TPO) and C3 / C2 binary copolymer polypropylene; As a further technical solution, the density of the thermoplastic polyolefin resin is 0.850-0.930 g / cm 3 , the melt index at 230°C / 2.16Kg is 0.3-3.5 g / 10min; such as LyondellBasell's Hifax CA 10A, AdflexQ300F, Dow Chemical's Versify 2300, ExxonMobil's Vistamaxx 6102, Yanshan Petrochemical's B9302, Sino-Korean Petrochemical's NS06, etc.; As a further technical solution, the density of the thermoplastic polyolefin resin is 0.87-0.89 g / cm 3 , the melt index at 230°C / 2.16Kg is 0.3-1.0 g / 10min; As a further technical solution, the toughening resin includes one or more of ethylene / α-octene random copolymer (POE), ethylene / α-butene random copolymer (POE), and ethylene / α-octene block copolymer (OBC); As a further technical solution, the density of the toughening resin is 0.855-0.905 g / cm 3 , the melt index at 190°C / 2.16Kg is 0.3-2.0; such as Dow Chemical's Engage 8842, Infuse 9010, etc.; As a further technical solution, the toughening resin has a density of 0.85-0.87 g / cm 3 g / cm 3 , ethylene / α-octene random copolymer having a melt index of 0.3-1.0 g / 10 min at 190°C / 2.16 kg and / or a density of 0.87-0.88 g / cm 3 g / cm 3 , a random copolymer of ethylene / α-butene having a melt index of 0.3-1.0 g / 10min at 190°C / 2.16Kg; As a further technical solution, the inorganic filler includes one or more of calcium carbonate, talc, calcined kaolin, and calcite. As a further technical solution, the calcium carbonate is preferably ultrafine active heavy calcium carbonate with a bulk density of 1-1.3 g / cm 3 The average particle size (D50) is between 4.0-6.0μm. For example, Omyacarb 6 from Omya Calcium; As a further technical solution, the antioxidant includes one or more of an organic phosphite (with low volatility and hydrolysis resistance) and a hindered phenol antioxidant; preferably, an antioxidant compounded with an organic phosphite and a hindered phenol antioxidant; for example, BASF's Irganox B 225; The light stabilizer is a block oligomeric hindered amine light stabilizer, such as Chimassorb 2020 from BASF; The nucleating agent is one or more of stearate nucleating agents, sorbitol nucleating agents, organic phosphate nucleating agents, aromatic amide nucleating agents, and carboxylic acid metal salt nucleating agents; preferably, a composite nucleating agent of stearate nucleating agents and carboxylic acid metal salt nucleating agents having an average particle size (D50) between 1.0 and 3.0 μm; As a further technical solution, the pigment includes one or more of titanium dioxide, carbon black, iron oxide, Prussian blue, lead silicate, monoazo, disazo, and phthalocyanine, preferably rutile TiO2.

[0022] The wide-width thermoplastic polyolefin anti-seepage geomembrane prepared by the preparation method has a width greater than or equal to 6m, a bidirectional elongation at break greater than or equal to 650% (preferably greater than or equal to 750%), a difference between the longitudinal and transverse elongation at break less than or equal to 200% (preferably less than or equal to 100%), and longitudinal and transverse tensile strengths both greater than or equal to 12MPa. Compared with the prior art, the present invention has the following beneficial effects:

[0023] In the preparation process of the TPO geomembrane of the present invention, the limitation of the traditional technology that the material is crystallized during the calendering and thickness determination process of the three-roll calender is broken, the crystallization temperature of the material is increased by adding a nucleating agent to the raw material, and the melt temperature during extrusion of the screw extruder is reduced by improving the structure of the screw extruder, so that most of the material is crystallized before entering the three-roll calender, avoiding the problem of excessive difference in longitudinal and transverse elongation at break of the large-width thermoplastic polyolefin anti-seepage geomembrane caused by material crystallization during the calendering and thickness determination process, reducing the difference in longitudinal and transverse elongation at break, and realizing the preparation of multi-deformation large-width thermoplastic polyolefin anti-seepage geomembrane, which can be suitable for large-width thermoplastic polyolefin anti-seepage geomembrane in high-pressure water environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic structural diagram of a single screw extruder for extruding a wide-width TPO geomembrane in one embodiment of the present invention; Figure 2 It is a structural schematic diagram of a barrel mechanism in one embodiment of the present invention; Figure 3 It is a schematic diagram of the structure of a barrel in one embodiment of the present invention; Figure 4 A schematic diagram of the structure of an extrusion screw in one embodiment of the present invention; Figure 5 for Figure 4 A magnified image of point A; Figure 6 It is a schematic diagram of the structure of the homogenizing section extrusion screw in one embodiment of the present invention; Figure 7 The cross-sectional appearance diagrams of the geomembrane products of Example 1 and Comparative Example 1; Figure 8 The surface appearance diagrams of the geomembrane products of Example 1 and Comparative Example 1; Fig. 9 The melting and crystallization temperature curves of the raw materials in Example 1 and Comparative Example 2 are shown; Fig.10 It is a fluctuation diagram of the unidirectional elongation at break of the geomembrane products of Example 1 and Comparative Example 1 at different positions; Fig.11It is a curve diagram of the biaxial tensile stress versus strain of the geomembrane products of Example 1, Comparative Example 2 and Comparative Example 5; Fig.12 This is a schematic diagram of the operation of using a biaxial / biaxial tensile tester to perform a biaxial elongation at break test.

[0025] exist Figure 1-2 In: 1. barrel mechanism, 2. cooling coil, 3. feed port, 4. discharge port, 5. extrusion screw, 6. motor, 7. feeding section, 8. first compression section, 9. barrier section, 10. exhaust section, 11. second compression section, 12. homogenization section, 13. exhaust port, 14. water ring vacuum pump, 15. pin, 16. protective shell, 17. barrel, 18. heating coil, 19. heating module, 20. cooling fan, 21. automatic screen changer, 22. metering pump, 23. static mixer, 24. distributor, 25. wide-width mold, 26. spiral groove, 27. temperature sensor. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0028] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The present invention is described in further detail below with reference to the accompanying drawings. Device Embodiment

[0030] Figure 1-6 An embodiment of a single screw extruder for wide-width TPO geomembrane extrusion of the present invention is shown, comprising a barrel mechanism 1, a feed port 3 and a discharge port 4 arranged on the barrel mechanism 1, an extrusion screw 5 rotatably arranged in the barrel mechanism 1, and a motor 6 driving the extrusion screw 5 to rotate; the extrusion screw 5 comprises a feeding section 7, a first compression section 8, a barrier section 9, an exhaust section 10, a second compression section 11 and a homogenizing section 12 arranged in sequence according to the direction of travel of the material. The present invention arranges an exhaust section 10 in the middle of the screw to discharge bubbles in the melt, and arranges a second compression section 11 after the exhaust section 10 to re-build pressure on the melt, thereby improving the uniformity and plasticizing effect of the melt. The present invention improves the structure of the extrusion screw, and arranges it to include a feeding section, a first compression section, a barrier section, an exhaust section, a second compression section and a homogenizing section arranged in sequence in the direction of material travel. After the material of the present invention is melted in the first compression section, it enters the exhaust section through the barrier section to discharge the gas in the melt, and then re-builds pressure in the second compression section and is homogenized in the homogenizing section before being discharged; wherein the functions of each section of the extrusion screw of the present invention are as follows: 1) the present invention arranges the first compression section to melt the material, 2) the barrier section in the traditional technology is usually arranged between the compression section and the homogenizing section, and is used to 1) The present invention sets a barrier section between the first compression section and the exhaust section to block the unmelted material, and the barrier section can promote the discharge of bubbles while blocking the unmelted material, improve the exhaust effect, and prevent the backflow of the exhaust section material; 2) The present invention sets an exhaust section to discharge bubbles in the melt, 3) The present invention sets a second compression section after the exhaust section to build up pressure on the material for the second time, which improves the plasticization effect of the material and improves the uniformity and plasticization effect of the melt, 4) The present invention sets a homogenization section to homogenize the melt before extrusion to provide uniformity of the melt. In addition, the present invention also sets a number of pins in the middle and rear part of the first compression section to mix and homogenize while compressing and plasticizing, so as to promote uniform mixing of the melt, so that the melt can be preliminarily homogenized before exhausting, and improve the uniformity and plasticization effect of the melt. In summary, the setting order of each section of the present invention greatly improves the uniformity and plasticization effect of the melt, so that it can meet the production needs of large-capacity materials.

[0031] As an embodiment of the single-screw extruder for extruding a wide-width TPO geomembrane of the present invention, the diameter of the extrusion screw is ≥180 mm, and the aspect ratio is ≥38.

[0032] As an embodiment of a single screw extruder for wide-width TPO geomembrane extrusion of the present invention, the diameter of the extrusion screw 5 is 180 mm, and the aspect ratio is 38; this parameter setting enables it to meet the demand for extrusion of wide-width TOP geomembranes of 6 m and above.

[0033] As an embodiment of a single-screw extruder for extruding a wide-width TPO geomembrane according to the present invention, the extrusion screw 5 is provided with a plurality of ring pins 15 at the middle and rear part of the first compression section 8 and on the homogenization section 12. The design of the pins 15 of the present invention, especially the setting of the pins in the first compression section, further improves the mixing and plasticizing effect of the melt.

[0034] As an embodiment of a single screw extruder for extruding a wide-width TPO geomembrane according to the present invention, in the homogenizing section, adjacent ring pins 15 are staggered.

[0035] As an embodiment of a single screw extruder for extruding a wide-width TPO geomembrane according to the present invention, in the middle and rear part of the first compression section 8, a plurality of circles of pins 15 are positioned correspondingly in the radial direction and are distributed in rows, and the spacing distance between adjacent circles is equal to the thread pitch of the extrusion screw of the first compression section.

[0036] As an embodiment of a single screw extruder for wide-width TPO geomembrane extrusion of the present invention, the barrel mechanism 1 includes a protective shell 16, a barrel 17 arranged in the protective shell 16, a heating module 19 sleeved on the barrel 17, and a cooling fan 20 arranged on the outside of the protective shell 16 and used to cool the heating module 19. The heating module 19 is used to heat the material, and the cooling fan 20 can cool the heating module 19 when the temperature of the barrel 17 exceeds the set temperature, thereby realizing temperature control of the material.

[0037] As an embodiment of a single-screw extruder for extruding a wide-width TPO geomembrane according to the present invention, the heating module 19 includes a heating coil 18 wound around the outer wall of the barrel 17 .

[0038] As an embodiment of a single-screw extruder for extruding a wide-width TPO geomembrane according to the present invention, a plurality of spiral grooves 26 are provided on the outer wall of the barrel 17 , and the heating coil 18 is wound around the outer wall of the barrel 17 along the spiral grooves 26 .

[0039] As an embodiment of a single-screw extruder for extruding a wide-width TPO geomembrane according to the present invention, the air outlet of the heat dissipation fan 20 is aligned with the heating coil 18 of the corresponding heating module 19 .

[0040] As an embodiment of a single screw extruder for extruding a wide TPO geomembrane of the present invention, two exhaust ports 13 are arranged on the barrel 17 at positions corresponding to the exhaust section 10 of the extrusion screw 5, and the exhaust port 13 is connected to a water ring vacuum pump 14. A conventional screw extruder, even if an exhaust section is provided, only has one exhaust port, while the present invention provides two exhaust ports on the barrel of the exhaust section, and a water ring vacuum pump is provided at the exhaust port. On the one hand, this design can provide a larger exhaust volume, accelerate the discharge of gas in the melt, and avoid defects such as pits in the product caused by residual bubbles. On the other hand, it can promote the cooling of the melt and solve the problem of melt temperature rise caused by shear force, thereby reducing the temperature during the extrusion of the wide TPO geomembrane. The two factors work together to greatly reduce the melt defects of the TPO filler system compared to the conventional single screw extruder that is simply scaled up.

[0041] As an embodiment of a single screw extruder for extruding a wide-width TPO geomembrane according to the present invention, a temperature sensor 27 is also provided on the barrel mechanism for detecting the temperature of the material.

[0042] As an embodiment of a single screw extruder for wide-width TPO geomembrane extrusion of the present invention, a cooling coil 2 is provided at a position corresponding to the feeding section outside the barrel 17. Since the material is usually fed by a conveyor, and the temperature of the material entering the extruder is too high due to shear heat generated by the conveyor during the material conveying process, the cooling coil 2 is provided at the feeding section of the extruder to cool the material entering the extruder, so as to avoid the temperature of the material entering the extruder being too high and affecting the temperature control of the barrel 17, thereby causing product defects.

[0043] As an embodiment of a single screw extruder for wide-width TPO geomembrane extrusion of the present invention, according to the direction of material travel, the discharge port 4 is also sequentially provided with an automatic screen changer 21, a metering pump 22, a static mixer 23, a distributor 24 and a wide-width mold 25.

[0044] As an embodiment of the single screw extruder for wide-width TPO geomembrane extrusion of the present invention, the width of the wide-width mold is greater than or equal to 6m.

[0045] In summary, the present invention adjusts the diameter and aspect ratio of the extrusion screw, the functions and order of each section of the screw, sets two exhaust ports, and sets a water ring vacuum pump. While the capacity of the single-screw extruder is greatly improved, the mixing and plasticizing effects of the melt are ensured, and the temperature of the melt during extrusion is reduced, so that it can be suitable for the extrusion of wide TPO geomembranes greater than or equal to 6m. In addition, it is also beneficial to the discharge of bubbles in the melt, avoiding product defects caused by residual bubbles in the melt. Example 1

[0046] A wide thermoplastic polyolefin anti-seepage geomembrane, comprising the following raw materials in parts by weight:

[0047] The preparation method comprises the following steps: Step 1: Preparation of high concentration powder thermoplastic polyolefin masterbatch: Firstly, the inorganic filler, antioxidant, light stabilizer, nucleating agent and pigment are mixed evenly to obtain powder, and then the powder is mixed evenly with part of thermoplastic polyolefin resin, and then sent to a twin-screw extruder for shear blending extrusion granulation to obtain a high-concentration powder thermoplastic polyolefin masterbatch (powder content is 50%); The setting temperature of the twin-screw extruder is 165-190°C, and the melt temperature of the twin-screw extruder during extrusion (when the material just leaves the screw, that is, the material at the discharge port) is ≤230°C.

[0048] Step 2: Preparation of geomembrane: The high-concentration powdered thermoplastic polyolefin masterbatch prepared in step 1, the remaining thermoplastic polyolefin resin and the toughening resin are fed into the vacuum double-exhaust single-screw extruder described in the equipment embodiment, melted and plasticized in the vacuum double-exhaust single-screw extruder, and extruded into a 6.5m wide flat extrusion die for forming, and then pulled forward, and naturally cooled to 120-145 degrees Celsius during the process of traveling, so that the crystallization of the material is carried out to 40-80%, and then enters a three-roll calender to determine the thickness, and then trims, cuts to a fixed length, rolls, and packages to obtain a wide-width thermoplastic polyolefin anti-seepage geomembrane (width 6m); The temperature of the vacuum double exhaust single screw extruder is set to 170-185°C, and the melt temperature of the vacuum double exhaust single screw extruder during extrusion (when the material just leaves the screw, that is, the material at the discharge port) is ≤200°C; the temperature of the mold is set to 170-185°C. Example 2

[0049] A wide thermoplastic polyolefin anti-seepage geomembrane, comprising the following raw materials in parts by weight:

[0050] The preparation method comprises the following steps: Step 1, preparation of thermoplastic polyolefin masterbatch: firstly, inorganic filler, antioxidant, light stabilizer, nucleating agent and pigment are uniformly mixed to obtain powder, thermoplastic polyolefin resin and toughening resin are uniformly mixed to obtain pellets; then the powder and pellets are sent to a twin-screw extruder for shearing, blending, extrusion and granulation, and dried and homogenized to obtain thermoplastic polyolefin masterbatch; Step 2: Geomembrane preparation: The thermoplastic polyolefin masterbatch prepared in step 1 is fed into the vacuum double exhaust type single screw extruder described in the equipment embodiment, melted and plasticized in the vacuum double exhaust type single screw extruder, and extruded into a flat extrusion die with a width of 6.5 m for forming, and then pulled forward, and naturally cooled to 120-145 degrees Celsius during the process of moving, so that the crystallization of the material is carried out to 40-80%, and then enters a three-roll calender to determine the thickness, and then trims, cuts to a fixed length, rolls, and packages to obtain a wide thermoplastic polyolefin anti-seepage geomembrane (width 6 m); The temperature of the vacuum double exhaust single screw extruder is set to 170-185°C, and the melt temperature of the vacuum double exhaust single screw extruder during extrusion (when the material just leaves the screw, that is, the material at the discharge port) is ≤200°C; the temperature of the mold is set to 170-185°C. Example 3

[0051] A wide thermoplastic polyolefin anti-seepage geomembrane, comprising the following raw materials in parts by weight:

[0052] The preparation method is the same as that of Example 1. Comparative Example 1

[0053] A wide thermoplastic polyolefin anti-seepage geomembrane, comprising the following raw materials in parts by weight: the same as in Example 1; The preparation method is the same as that in Example 1, except that, in the geomembrane preparation process of step 2, a separate single-screw extruder is used to replace the vacuum double-exhaust single-screw extruder of Example 1 for melt plasticization. The plasticization quality of TPO geomembrane extruded by the separate single-screw extruder is poor, and due to the lack of exhaust design, the air mixed in during the raw material mixing process cannot be discharged in time, and defects such as pores and cavities are easily formed inside the product. Comparative Example 2

[0054] A wide-width thermoplastic polyolefin anti-seepage geomembrane comprises the following raw materials in parts by weight: the same as Example 2, except that no nucleating agent is added; The preparation method is the same as that in Example 1.

[0055] Due to the removal of the nucleating agent in this comparative example, before the geomembrane reaches the three-roll calender, although the material temperature is the same as that in Example 2, the material does not begin to crystallize; instead, the material completes the main crystallization during the thickness determination process of the three-roll calender. Comparative Example 3

[0056] A wide thermoplastic polyolefin anti-seepage geomembrane (width 6m), comprising the following raw materials in parts by weight: the same as in Example 1; The preparation method is the same as that in Example 1, except that, in the step 2, during the preparation of the geomembrane, a conventional twin-screw extruder is used to replace the vacuum double-exhaust single-screw extruder in Example 1 for melt plasticization, wherein the barrel temperature of the twin-screw extruder is set to 165-190°C, and the temperature of the mold is set to 180-185°C. The melt temperature of the geomembrane raw material before entering the mold after shearing, plasticizing and conveying by the twin-screw extruder is about 30°C higher than that in Example 1, and is between 200-230°C; since the temperature of the material during extrusion is higher than that in Example 1, when the equipment spacing remains unchanged, the temperature of the geomembrane when it reaches the three-roll calender is also higher than that in Example 1, which is 150-175°C; at this time, the material has not begun to crystallize, and the crystallization process of the material is completed during the thickness setting process of the three-roll calender. Comparative Example 4

[0057] A wide-width thermoplastic polyolefin anti-seepage geomembrane (width 6m), comprising the following raw materials in parts by weight: the same as Example 1, except that no nucleating agent is added; The preparation method is the same as that in Example 1, except that, in the preparation process of the geomembrane in step 2, a twin-screw extruder is used to replace the vacuum double-exhaust single-screw extruder in Example 1 for melt plasticization, wherein the barrel temperature of the twin-screw extruder is set to 165-190°C, and the temperature of the mold is set to 180-185°C. The melt temperature of the geomembrane raw material before entering the mold after shearing, plasticizing and conveying by the twin-screw extruder is about 30°C higher than that in Example 1, and is between 200-230°C; since the temperature of the material during extrusion is higher than that in Example 1, when the equipment spacing remains unchanged, the temperature of the geomembrane when it reaches the three-roll calender is also higher than that in Example 1, which is 150-175°C; since no nucleating agent is added, the crystallization temperature of the material is about 20°C lower than that in Example 1; at this time, the material has not started to crystallize, and the main crystallization process of the material is completed during the thickness setting process of the three-roll calender. Comparative Example 5

[0058] Commercially available TPO homogeneous waterproof membrane for building roofs. Comparative Example 6

[0059] A polyolefin elastomer (POE) anti-seepage geomembrane, comprising the following raw materials in parts by weight:

[0060] The preparation method is the same as that of Example 1, except that the strength of the product is low due to excessive addition of POE. Comparative Example 7

[0061] Commercially available HDPE geomembrane. Comparative Example 8

[0062] Commercially available PVC geomembrane. Effect example 1: Appearance inspection

[0063] The geomembranes prepared in Example 1 and Comparative Example 1 were inspected for appearance. The surface and cross-section of the geomembranes were visually observed. The results are shown in Figure 7-8 ; from Figure 7-8 From the comparison, it can be seen that the vacuum double-exhaust single-screw extruder adopted in the present invention has good melt plasticization quality, and the prepared geomembrane has a smooth and flat surface, a dense cross-section and no pores; while the separation single-screw extruder in the traditional technology has poor plasticization quality for extruding TPO geomembrane, and due to its lack of exhaust design, the air mixed in during the raw material mixing process cannot be discharged in time, and defects such as pores and cavities are easily formed inside the product. Effect example 2: Crystallization temperature detection

[0064] The crystallization temperature of the raw materials used in Example 1 and Comparative Example 2 was tested, and the results are shown in Fig. 9 ; Crystallization temperature method: Use differential scanning calorimeter (DSC) for testing. Cut 5-10 mg of sample, place it in a standard aluminum crucible, and select nitrogen test atmosphere. Set up the heating and cooling experimental program, heat the sample to 200℃ and then cool it to 0℃, the heating and cooling rates are both 10℃ / min, and collect the heat flow curve during the cooling process. Read the exothermic peak temperature of the cooling process, which is the crystallization peak temperature.

[0065] from Fig. 9 It can be seen that under the conditions of the present invention, the peak temperature of the melting and crystallization of the raw material in a stress-free state is about 118 degrees, and under the conditions of comparative example 2, the peak temperature of the melting and crystallization of the raw material in a stress-free state is about 98°C. The addition of a nucleating agent in the present invention helps to increase the melting and crystallization temperature of the raw material, laying the foundation for achieving most of the crystallization of the material before entering the three-roll mill. Effect Example 3: Performance Testing

[0066] The performance of the geomembranes of the embodiments and comparative examples was tested, and the results are shown in Tables 1 and Figure 10-11 ; The testing indicators and methods are as follows: 1) Transverse or longitudinal elongation at break test: The test shall be conducted according to method B in GB / T 328.9-2007, using dumbbell type I specimens in accordance with GB / T 528-2009, and the tensile speed shall be (250±50) mm / min.

[0067] 2) Right-angle tear strength test: The test was conducted in accordance with GB / T 529-2008, using the non-cut right-angle tear method and a tensile speed of (250±50) mm / min.

[0068] 3) Bidirectional elongation at break test: Cut a 100mm×100mm square specimen and use Fig.12 The biaxial / biaxial tensile tester shown in the figure fixes the sample with four identical pneumatic clamps on two perpendicular axes and places it in the test center for biaxial elongation at break test. The width of the pneumatic clamp is 50 cm, the relative clamp spacing is 55 cm, and equibiaxial stretching (stretching in two perpendicular directions at the same rate) is adopted, and the stretching rate is (250±50) mm / min. The average value of the ratio of the clamp displacement / initial clamp spacing in the two directions is taken as the biaxial elongation at break.

[0069] 4) Fluctuation of unidirectional elongation at break at different positions in the product width direction: Several test points were taken at equal intervals under a width of 6 meters to measure the unidirectional elongation at break, and the fluctuation of the unidirectional elongation at break at each position was evaluated. The results are shown in Fig.10 ; 5) Comparison of biaxial tensile properties: Fig.11 The biaxial / biaxial tensile tester was used to test the biaxial elongation at break of the sample, and a biaxial tensile stress-biaxial tensile strain curve was drawn. The results are shown in Fig.11 .

[0070] 2. Results and Analysis Table 1

[0071] Note: / means not detected; From Table 1 and Figure 10-11 The data shows that:

[0072] 1) The geomembranes prepared in Examples 1-3 of the present invention have better performance in all aspects, with small differences in longitudinal / transverse elongation at break, and better tensile strength and bidirectional elongation at break than the comparative examples with the same width. This is because in the process of preparing wide-width geomembranes, the present invention increases the melting crystallization temperature of the raw materials by adding nucleating agents, and reduces the extrusion temperature of the materials by using a vacuum double-exhaust single-screw extruder, thereby ensuring that most of the materials are crystallized before entering the three-roll calendering and thickness setting machine without changing the distance between the extrusion die and the three-roll calendering and thickness setting machine, thereby providing the performance of the geomembrane of the present invention in all aspects, especially reducing the difference in longitudinal / transverse elongation at break.

[0073] 2) In Comparative Example 2, since no nucleating agent is added, the temperature of the raw material melting and crystallization is higher than that of Example 1, so that the material does not begin to crystallize before reaching the three-roll calender, but completes the main crystallization process during the thickness setting process of the three-roll calender, resulting in a large difference in the longitudinal / transverse elongation at break, and the unidirectional elongation at break of each part fluctuates greatly.

[0074] 3) In Comparative Example 3, the vacuum double-exhaust single-screw extruder of the present invention is replaced by a traditional twin-screw extruder. Since the shear temperature rise of the twin-screw is greater than that of the single-screw, the temperature of the twin-screw extruder during material extrusion is higher than that of the vacuum double-exhaust single-screw extruder of the present invention, resulting in a higher melt temperature during material extrusion, which is about 30°C higher than that of Example 1 and is between 200-230°C. The extrusion temperature is relatively high. On the one hand, the high temperature causes partial decomposition of the material, thereby reducing the strength (tensile strength, right-angle tear strength) of the product (see the comparison between Comparative Example 2 and Comparative Example 4). On the other hand, the defect is that since the temperature of the material during extrusion is higher than that of Example 1, when the equipment spacing remains unchanged, the temperature of the geomembrane when it reaches the three-roll calender is also higher than that of Example 1, which is 150-175°C. At this time, the material has not begun to crystallize, and the main crystallization process of the material is completed during the thickness setting process of the three-roll calender, resulting in a large difference in the elongation at break in the transverse and longitudinal directions of the product.

[0075] 4) In order to reduce the difference in longitudinal / transverse elongation at break of the product and improve the bidirectional elongation at break of the product, in Comparative Example 6, the amount of POE added in the formula was increased. However, the excessive amount of POE added resulted in a decrease in the strength of the product, making it impossible to prepare a geomembrane that met the requirements.

[0076] The above-described embodiments are only preferred embodiments of the present invention, and are not exhaustive of the feasible implementations of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a wide-width thermoplastic polyolefin anti-seepage geomembrane, characterized in that: The steps include: After the thermoplastic polyolefin composite material is evenly mixed, it is sent to a screw extruder, melted and plasticized by the screw extruder, and extruded into a mold at a low temperature for forming. It is then towed forward and naturally cooled during the process to allow the material to complete a partial crystallization process. It then enters a three-roll calender to determine the thickness, thereby obtaining a wide-width thermoplastic polyolefin anti-seepage geomembrane.

2. The method for preparing a wide-width thermoplastic polyolefin anti-seepage geomembrane according to claim 1, characterized in that: After the thickness is determined by the three-roll calender, it is necessary to trim, cut to length, and roll it up to obtain the thermoplastic polyolefin anti-seepage geomembrane.

3. The method for preparing a wide-width thermoplastic polyolefin anti-seepage geomembrane according to claim 1, characterized in that: The thermoplastic polyolefin composite material includes a nucleating agent; The screw extruder adopts a vacuum double exhaust single screw extruder; The temperature of the vacuum double exhaust single screw extruder is set to 170-185°C, and the melt temperature of the vacuum double exhaust single screw extruder during extrusion is ≤200°C; the temperature of the mold is set to 170-185°C; During the process of natural cooling, the material crystallization process is completed by 40-80%.

4. The method for preparing a wide-width thermoplastic polyolefin anti-seepage geomembrane according to claim 3, characterized in that: The vacuum double exhaust type single screw extruder comprises a barrel mechanism (1), a feed port (3) and a discharge port (4) arranged on the barrel mechanism (1), an extrusion screw (5) rotatably arranged in the barrel mechanism (1) and according to any one of claims 1 to 4, and a motor (6) for driving the extrusion screw (5) to rotate; The extrusion screw comprises a feeding section (7), a first compression section (8), a barrier section (9), an exhaust section (10), a second compression section (11) and a homogenizing section (12) which are arranged in sequence according to the direction of travel of the material; Two exhaust ports (13) are provided at positions on the barrel mechanism corresponding to the exhaust section (10) of the extrusion screw (5), and the exhaust ports (13) are connected to a water ring vacuum pump (14).

5. The method for preparing a wide-width thermoplastic polyolefin anti-seepage geomembrane according to claim 3, characterized in that: The extrusion screw (5) is provided with a plurality of ring pins (15) at the middle and rear part of the first compression section (8) and at the homogenization section (12); The diameter of the extrusion screw (5) is ≥180 mm, and the aspect ratio is ≥38.

6. The method for preparing a wide-width thermoplastic polyolefin anti-seepage geomembrane according to claim 1, characterized in that: The thermoplastic polyolefin composite material comprises the following raw materials in parts by weight: 45-75 parts of thermoplastic polyolefin resin, 10-30 parts of toughening resin, 10-30 parts of inorganic filler, 0.3-1.3 parts of antioxidant, 0.3-1.3 parts of light stabilizer, 0.1-2 parts of nucleating agent, and 0.3-3 parts of pigment.

7. The method for preparing a wide-width thermoplastic polyolefin anti-seepage geomembrane according to claim 6, characterized in that: Before the thermoplastic polyolefin composite material is fed into the screw extruder, the inorganic filler, antioxidant, light stabilizer, nucleating agent and pigment are firstly mixed evenly to obtain powder, and then the powder is mixed evenly with part of the thermoplastic polyolefin resin, and then fed into the twin-screw extruder for shearing, blending, extrusion and granulation, and dried and homogenized to obtain high-concentration powder thermoplastic polyolefin masterbatch; then the high-concentration powder thermoplastic polyolefin masterbatch, the remaining thermoplastic polyolefin resin and the toughening resin are fed into the screw extruder; Alternatively, before the thermoplastic polyolefin composite material is fed into the screw extruder, the inorganic filler, antioxidant, light stabilizer, nucleating agent and pigment are first mixed evenly to obtain powder, and the thermoplastic polyolefin resin and toughening resin are mixed evenly to obtain pellets; the powder and pellets are then fed into a twin-screw extruder for shear blending, extrusion and granulation, dried and homogenized to obtain thermoplastic polyolefin masterbatch, and then the thermoplastic polyolefin masterbatch is fed into the screw extruder.

8. The method for preparing a wide-width thermoplastic polyolefin anti-seepage geomembrane according to claim 7, characterized in that: The setting temperature of the twin-screw extruder is 165-190°C, and the melt temperature of the twin-screw extruder during extrusion is ≤230°C.

9. The method for preparing a wide-width thermoplastic polyolefin anti-seepage geomembrane according to claim 6, characterized in that: The thermoplastic polyolefin resin includes one or more of C3 / C2 / C4 terpolymer polypropylene and C3 / C2 binary copolymer polypropylene; The toughening resin includes one or more of ethylene / α-octene random copolymer, ethylene / α-butene random copolymer, and ethylene / α-octene block copolymer; The inorganic filler includes one or more of calcium carbonate, talc, calcined kaolin and calcite. The antioxidant includes one or more of organic phosphites and hindered phenol antioxidants; The light stabilizer is a block oligomeric hindered amine light stabilizer; The nucleating agent is one or more of stearate nucleating agents, sorbitol nucleating agents, organic phosphate nucleating agents, aromatic amide nucleating agents, and carboxylic acid metal salt nucleating agents; The pigment includes one or more of titanium dioxide, carbon black, iron oxide, Prussian blue, lead silicate, monoazo, disazo, and phthalocyanine.

10. A wide thermoplastic polyolefin anti-seepage geomembrane prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The width of the wide-width thermoplastic polyolefin anti-seepage geomembrane is greater than or equal to 6m.

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