A textured plastic film

Abstract

The application discloses a rough-surface plastic film and belongs to the technical field of geosynthetic materials. The rough-surface plastic film is a blow-molded integral film body, at least one side surface of the film body is provided with a rough surface formed by protrusions of incompletely fused particles; the particles are embedded in the surface layer of the film body and are integrally fused with the base material of the film body, and there is no interface separation between the particles and the base material of the film body. The rough-surface plastic film can be a single-layer film or a composite film, the composite film comprises a rough-surface layer and a smooth-surface layer, and the rough-surface layer and the smooth-surface layer are integrally formed in an in-mold composite structure. The particles of the product are stably and durably combined with the base material, the film body is dense and free of foamed micropores, the rough-surface parameters are uniform and controllable, the friction performance is excellent, and the mechanical performance is comprehensive, so that the rough-surface plastic film is suitable for seepage prevention projects such as waste landfill sites, tailing ponds and water conservancy dams.

Description

Technical Field

[0001] This invention relates to the field of plastic film technology, specifically to a textured plastic film, particularly suitable for textured geomembranes (including high-density polyethylene (HDPE) geomembranes, linear low-density polyethylene (LLDPE) geomembranes, etc.), and belongs to the field of geosynthetic materials technology. Background Technology

[0002] Textured geomembranes, as an important geosynthetic material, are widely used in engineering fields such as landfill seepage control, tailings dam seepage control, hydraulic dam seepage control, chemical solid waste disposal site seepage control, and environmental remediation. Their textured surface significantly improves the membrane-soil interface friction coefficient, effectively inhibiting slippage and instability of seepage control structures under conditions such as steep slopes and high water pressure. They are a core seepage control material ensuring the safe and stable operation of seepage control projects. With increasingly stringent national environmental protection requirements and the continuous improvement of the national standard GB / T 17643 "Geosynthetic Materials - Polyethylene Geomembrane", the market demand for high-quality textured geomembranes is constantly growing.

[0003] Currently, textured geomembranes in the industry are mainly prepared using the following two processes: I. Roughened Geomembrane Prepared by Post-Turning Process The spray roughening process, also known as the secondary spray roughening process, refers to the process of spraying hot-melt polyethylene particles or modified materials onto the surface of a pre-formed smooth geomembrane through an independent spraying production line. After the particles cool and solidify, they adhere to the membrane surface to form a rough structure.

[0004] The textured geomembrane products prepared using this process have textured particles that adhere to the geomembrane surface only through physical bonding; the particles do not achieve molecular-level fusion and anchoring with the membrane substrate. This product type has the following inherent defects: First, the interfacial bonding between the particles and the substrate is weak. Under complex service conditions such as long-term immersion in water, membrane-soil interface friction, and alternating high and low temperatures, the sprayed particles are prone to detachment and peeling of the membrane surface, leading to a decrease in the product's friction performance and affecting the long-term service safety of the project.

[0005] Secondly, the pits and defects formed on the membrane surface after the particles fall off not only reduce the seepage prevention performance, but may also cause stress concentration, accelerating the aging and damage of the geomembrane.

[0006] Third, since the particles only adhere to the surface, the surface of the product has poor durability. As the service time increases, the coefficient of friction gradually decreases, making it difficult to meet the needs of long-term seepage prevention projects.

[0007] II. Roughened Geomembrane Prepared by Nitrogen Foaming and Roughening Process Nitrogen foaming and roughening process involves injecting high-pressure nitrogen into the molten polymer layer during multi-layer co-extrusion blow molding. The nitrogen escapes from the film surface, creating an irregular, textured surface. This process is a one-step molding method, requiring no secondary processing.

[0008] Although the rough surface of the textured geomembrane product prepared using this process is an integral structure with the substrate, the product contains a large number of closed microbubbles and broken pores inside and on the surface, resulting in the following inherent defects: First, the presence of numerous microporous structures within the geomembrane compromises its compactness, resulting in a significant reduction in the product's tensile strength, puncture resistance, tear resistance, and impermeability, making it difficult to meet the performance requirements for high-end seepage control projects in the GB / T 17643 standard.

[0009] Secondly, the size and uniformity of microbubble distribution are difficult to control precisely, resulting in poor batch stability of the product's surface roughness. If the bubbles are too small, the surface roughness will be insufficient and the friction coefficient will not meet the standards. If the bubbles are too large, they will form interconnected pores or rupture defects, affecting the seepage prevention performance.

[0010] III. Other forms of textured geomembranes In addition to the two product forms mentioned above, the industry also produces textured geomembranes through embossing / roll pressing processes. This involves pressing the membrane surface with rollers bearing textured surfaces to create a textured finish. However, products prepared using this method are only suitable for thicker sheets or plates. For blown films, the embossing process can easily cause the membrane surface to stretch and thin, or even break. Furthermore, the textured structure formed by roll pressing is easily flattened during subsequent winding and laying processes, resulting in poor surface durability.

[0011] In summary, among existing textured geomembrane products, there is a lack of a product that simultaneously possesses stable and durable textured bonding, a dense matrix free of microporous defects, and uniform and controllable texture parameters. Therefore, developing a novel textured plastic membrane product to overcome the shortcomings of existing products has significant industrial application value and engineering practical significance. Summary of the Invention

[0012] (a) Purpose of the invention To address the technical shortcomings of existing roughened geomembrane preparation processes, such as easy detachment of particles and weak interfacial bonding, as well as the presence of numerous micropores and significantly reduced mechanical properties in roughened geomembranes prepared by nitrogen foaming and roughening processes, this invention provides a roughened plastic membrane. The aim is to provide a roughened plastic membrane product with stable and durable bonding between the roughened particles and the matrix, a dense matrix free of micropore defects, and uniform and controllable roughness parameters.

[0013] (II) Technical Solution To achieve the above-mentioned objectives, the present invention provides the following technical solution: A textured plastic film, wherein the textured plastic film is a blow-molded integral film body, and at least one side surface of the film body has a textured surface formed by incompletely melted particle protrusions; the particles are embedded in the surface layer of the film body and integrally fused with the substrate of the film body, and there is no interface separation between the particles and the substrate of the film body.

[0014] Furthermore, the particles are uniformly distributed on the surface of the membrane; the composition of the particles may be the same as or different from the composition of the substrate of the membrane.

[0015] When the particle composition is the same as the substrate composition, the particles and the substrate are selected from one of high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a mixture of any two or three.

[0016] When the particle composition differs from the substrate composition, the particles and the substrate are each independently selected from one of high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a mixture of any two or three.

[0017] Furthermore, the height of the particles protruding from the substrate is 8% to 50% of the substrate thickness.

[0018] Furthermore, the textured plastic film is a single-layer film or a composite film; both sides of the single-layer film have the textured surface, or only one side has the textured surface and the other side is smooth; the composite film includes a textured layer and a smooth layer, the textured layer is located on at least one outer surface of the composite film, the particles are embedded in the textured layer, and the textured layer and the smooth layer are an in-mold composite integral molding structure.

[0019] Furthermore, the composite membrane has a three-layer composite structure, including two roughened layers and a smooth layer sandwiched between the two roughened layers. The two roughened layers are located on the outer surfaces of both sides of the composite membrane, and the particles are embedded in the two roughened layers and protrude from the outer surfaces of the roughened layers to form a double-sided roughened surface.

[0020] The above-mentioned rough-surfaced plastic film is made using the following method: S1 Preparation of blown film equipment: The blown film equipment includes a primary extruder, a pellet conveying device, a secondary extruder, and a die head; S2 Substrate Preparation and Particle Conveying: Start the primary extruder to heat, melt, and plasticize the plastic raw material to form a melt of the substrate, which is then conveyed to the feed inlet of the secondary extruder; simultaneously, start the particle conveying device to feed the particles into the feed inlet of the secondary extruder; the particle size is preferably 2mm to 5mm; S3 Secondary mixing and conveying: The secondary extruder receives the mixture of the substrate and the particles, and mixes and kneads it to make the particles evenly dispersed in the melt. The temperature is controlled by an independent zone temperature control module so that only the surface of the particles melts while the main body retains a solid form. S4 Film Formation: The mixture is extruded through a die and inflated to form a bubble-like film. The substrate is completely melted and deformed, while the particles are not completely melted. After inflation, the substrate thickness of the film is reduced, and the particles protrude from the substrate surface, forming a rough surface. The height of the particles protruding from the substrate is 8% to 50% of the substrate thickness. S5 Cooling and Shaping: Cooling the blown-up bubble; S6 Folding Traction: The cooled membrane bubble is folded into a flat sheet film by the herringbone plate guide, and then pulled out by the traction roller.

[0021] The speed of the particle conveying device can be adjusted to control the amount of particles fed per unit time, thereby controlling the distribution density of the rough particles; the temperature of the secondary extruder can be controlled by the independent zone temperature control module, thereby adjusting the degree of particle melting and controlling the final protrusion size of the particles.

[0022] The temperature of the primary extruder is controlled at 170℃~220℃, and the temperature of the secondary extruder is controlled at 160℃~200℃.

[0023] When a composite die is used, the textured layer melt containing particles is transported through the textured layer melt channel, and the smooth layer melt is transported through the smooth layer melt channel. The two are pressed together at the pressing channel to form a composite film structure integrating the textured and smooth layers. The composite die can prepare two-layer composite films (single-sided textured) or three-layer composite films (double-sided textured).

[0024] (III) Beneficial Effects Compared with existing product forms, the present invention has the following advantages: 1. The rough-textured particles have a stable and long-lasting bond, resulting in stable friction performance over a long period.

[0025] In the textured plastic membrane of this invention, particles are embedded in the membrane surface and integrally fused with the substrate. There is no interface separation between the particles and the substrate, which is different from the physical bonding interface of products produced by spraying. A molecular-level bond and anchoring are formed between the particles and the substrate. Under complex service conditions such as long-term immersion in water, membrane-soil interface friction, and alternating high and low temperatures, the particles are not easy to fall off, the membrane surface does not peel off, the product's friction performance is stable over a long period of time, and the service life of the engineering project is significantly extended.

[0026] 2. The membrane is dense and free of bubbles, fully preserving its mechanical properties.

[0027] The product of this invention does not require nitrogen foaming and roughening processes; the membrane has a dense internal structure, free of microbubbles and broken pores. Compared with nitrogen-foamed and roughened products, the roughened plastic membrane of this invention fully retains the inherent tensile strength, puncture resistance, tear resistance, and impermeability of the substrate, and can fully meet the performance requirements for high-end seepage prevention projects in GB / T 17643 standard.

[0028] 3. The surface roughness parameters are uniform and controllable, resulting in good product consistency.

[0029] In the product of this invention, the particles are uniformly distributed on the membrane surface, and the height (8%–50%) of the particles protruding from the substrate and their distribution density can be precisely controlled through temperature control and metering during the preparation process. Compared with nitrogen-foamed products where the size and distribution of microbubbles are difficult to control precisely, the surface roughness parameters of the product of this invention have good consistency and batch stability.

[0030] 4. The product offers flexible and diverse forms to meet the engineering needs of various scenarios.

[0031] The product of this invention can be a single-layer membrane or a composite membrane, and can achieve a single-sided or double-sided rough surface, making it suitable for various seepage prevention engineering scenarios such as landfills, tailings ponds, water conservancy dams, and chemical solid waste storage sites. In particular, the three-layer composite double-sided rough surface structure can meet the engineering requirements of high slopes, landfill closures, and other projects that require good friction performance on both sides. Attached Figure Description

[0032] The present invention will now be described in further detail with reference to the accompanying drawings.

[0033] Figure 1 This is a schematic diagram of the overall system structure of the rough plastic film preparation device of the present invention; Figure 2 This is a schematic diagram of the extrusion screw of the present invention; Figure 3 This is a cross-sectional schematic diagram of the internal structure of the textured plastic film (single layer) of the present invention; Figure 4 This is a cross-sectional schematic diagram of the internal structure of the rough-surfaced plastic film (composite double layer) of the present invention; Figure 5 This is a cross-sectional schematic diagram of the internal structure of the textured plastic film (composite three layers) of the present invention; The meanings of the markings in the diagram are as follows: 1—Primary extruder; 2—Secondary extruder; 3—Particle conveying device (precision particle metering unit); 4—Die head; 401—Textured layer melt flow channel; 402—Smooth layer melt flow channel; 403—Compression channel; 404—Spiral distribution channel; 5—Extrusion screw; 501—Feeding section; 502—Compression section; 503—Metering section; 504—Mixing section; 504a—Shearing teeth; 504b—Mixing tank; 6—Membrane body; 7—Particles; 8—Substrate; 9—Textured layer; 10—Smooth layer; 11—Cooling mechanism; 12—Hinge plate; 13—Traction roller. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the implementation of the present invention is not limited thereto.

[0035] I. Specific Implementation Methods of the Product Structure See Figures 3 to 5 The present invention provides a textured plastic film, which is a blow-molded one-piece film.

[0036] (a) Single-layer rough plastic film See Figure 3 The textured plastic film is a single-layer film structure, and the film body is composed of a substrate 8. The interior of the substrate 8 has a dense structure without foamed micropores. At least one side surface of the film body has a textured surface formed by incompletely melted particles 7 protruding.

[0037] Particle 7 is embedded in the surface layer of substrate 8 and is integrally fused with substrate 8, with no interface separation between particle 7 and substrate 8. "No interface separation" means that there is no physical bonding interface between particle 7 and substrate 8, as is present between particles and film surfaces in spray-textured products; instead, they are bonded and anchored at the molecular level, forming a unified whole. Particle 7 protrudes from the surface of substrate 8, forming a textured surface structure.

[0038] Particles 7 are uniformly distributed on the film surface to ensure uniformity of the rough surface friction performance. The composition of particles 7 can be the same as or different from that of the substrate 8. When the compositions of particles 7 and substrate 8 are the same, better fusion and anchoring can be achieved between particles 7 and substrate 8; when the compositions of particles 7 and substrate 8 are different, the differences in melting points or compatibility between different materials can be used to control the size and shape of the particle protrusions. The compositions of particles 7 and substrate 8 are independently selected from one of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE), or a mixture of any two or three.

[0039] The particle size of the particles 7 is preferably 2mm to 5mm, more preferably 2mm to 4mm, and most preferably 2mm to 3mm. When the particle size is less than 2mm, the protrusion height of the particles after inflation is insufficient, making it difficult to form an effective rough surface friction structure; when the particle size is greater than 5mm, the particles protrude too high, making them easy to be crushed or fall off during winding and laying, and may affect the overall mechanical properties of the membrane.

[0040] The height of particle 7 protruding from the surface of substrate 8 is 8% to 50% of the thickness of substrate 8. Within this range, the product has both a sufficient interfacial friction coefficient and ensures a strong bond between the particle and the substrate. Preferably, the protrusion height is 10% to 40% of the substrate thickness, more preferably 15% to 35%. When the protrusion height is less than 8% of the substrate thickness, the improvement in the surface friction coefficient is not significant; when the protrusion height is greater than 50% of the substrate thickness, the bonding area between the particle and the substrate is relatively reduced, and the particle is prone to breakage or detachment under stress.

[0041] The distribution density of particles 7 on the membrane surface can be precisely controlled by the rotation speed of the particle conveying device during the preparation process, and the preferred particle distribution density is 10 to 15 particles / cm².

[0042] Both sides of a single-layer textured plastic film have textured surfaces (i.e., double-sided textured surfaces).

[0043] (ii) Composite double-layer textured plastic film See Figure 4 The textured plastic film is a composite film structure, comprising a textured layer 9 and a smooth layer 10. The textured layer 9 is located on at least one outer surface of the composite film, and the smooth layer 10 is an inner layer or an outer layer on the other side of the composite film. The textured layer 9 and the smooth layer 10 are integrally molded in-mold, with no separation gap between the two layers, resulting in a strong bond.

[0044] The roughened layer 9 contains incompletely fused particles 7, which are embedded within and integrally fused with the substrate of the roughened layer 9, with no interface separation between the particles 7 and the substrate of the roughened layer 9. The particles 7 protrude from the outer surface of the roughened layer 9, forming a rough surface. The smooth layer 10 remains smooth and dense, playing a major role in waterproofing and mechanical load-bearing.

[0045] The particle size, protrusion height, distribution density, and composition selection of particles 7 are the same as those of the monolayer membrane, and will not be repeated here.

[0046] The composite double-layer textured plastic film can achieve a textured surface on one side (only one outer surface has a textured layer 9, and the other outer surface has a smooth layer 10).

[0047] (III) Composite three-layer textured plastic film See Figure 5The textured plastic film has a three-layer composite structure, including two textured layers 9 and a smooth layer 10 sandwiched between the two textured layers 9. The two textured layers 9 are located on the outer surfaces of the composite film on both sides, and the particles 7 are embedded in the two textured layers 9 and protrude from the outer surfaces of the textured layers 9, forming a double-sided textured surface. The smooth layer 10 is located in the middle layer and remains smooth and dense. The textured layers 9 and the smooth layer 10 are integrally molded in-mold, with no gaps between the layers, resulting in a strong bond.

[0048] The particle size of the particles 7 in the two rough surface layers 9 can be the same or different; the protrusion height of the particles 7 in the two rough surface layers 9 can be the same or different; the distribution density of the particles 7 in the two rough surface layers 9 can be the same or different. By independently adjusting the rough surface parameters on both sides, differentiated bilateral friction performance can be achieved to meet the needs of different engineering scenarios (such as one side contacting the soil and the other side contacting the cushion layer or cover layer).

[0049] It is understood that the composite membrane is not limited to the aforementioned three-layer structure, but can also be a multi-layer composite structure with three or more layers, including two textured layers and two or more smooth layers sandwiched between the two textured layers. The two textured layers are located on the outer surfaces of both sides of the composite membrane, with particles embedded within the two textured layers and protruding from their outer surfaces, forming a double-sided textured surface. The smooth layers and the smooth layers and textured layers are all integrally molded structures within the mold, with no interlayer gaps, ensuring a strong bond. By setting multiple smooth layers, the mechanical load-bearing capacity and impermeability of the membrane can be further improved, meeting the needs of higher-level seepage prevention projects.

[0050] Materials and compatibility specifications It should be noted that the materials used for the “substrate”, “particles”, “rough layer” and “smooth layer” mentioned in the above and below embodiments of the present invention are not limited to HDPE or LLDPE, but may also be other thermoplastic plastics and their blends that can meet the requirements of blow molding process.

[0051] This invention is applicable to a variety of thermoplastic plastic systems, including but not limited to: polyethylene (PE) materials, such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), etc.; polypropylene (PP) materials, such as homopolymer polypropylene (homogeneous polypropylene), random copolymer polypropylene (random copolymer PP), block copolymer polypropylene (block copolymer PP), etc.; ethylene-vinyl acetate copolymer (EVA); polyamide (PA, commonly known as nylon); polyvinyl chloride (PVC); thermoplastic polyolefin (TPO); and blends formed from any two or more of the above materials.

[0052] All of the above-mentioned materials can be used to prepare textured plastic films using the apparatus and method of this invention. The principle is as follows: the core of this invention lies in utilizing the difference in the melting state of materials at different melting stages—by controlling the temperature of the secondary extruder, only the surface of the particles melts while the main body remains in a solid state, thus causing the inflated particles to protrude from the substrate surface to form a textured surface. Therefore, any material that can be processed by blow molding can be used as a candidate material for the substrate, not limited to specific types of thermoplastic resins.

[0053] Based on the inventive concept of this invention, the selection of the substrate and particles is not strictly limited by specific chemical compositions, as long as the following conditions are met: the substrate can form a stable melt at the processing temperature and has good blow molding properties; the particles maintain a semi-molten state with a molten surface and a solid core at the processing temperature; and the substrate and particles are compatible. The compatibility between the substrate and particles can be determined by methods known in the art, including but not limited to: determining compatibility through the difference in solubility parameters (Hildebrand parameter or Hansen parameter)—when the difference in solubility parameters between the substrate and particles is less than 1.0 (J / cm³)^(1 / 2), it indicates good compatibility; or determining the interfacial tension of the blend—the smaller the interfacial tension, the better the compatibility; or predicting the thermodynamic compatibility of the blend, such as the Flory-Huggins interaction parameter χ value method. The quality of compatibility directly affects whether the particles and substrate can form an integrated fusion structure with "interface-free separation," which is the basis for achieving the particle embedding and anchoring effect in this invention.

[0054] When the substrate and particles are selected from different types of polymers, as long as they are compatible, the technical effect of "integrated fusion of particles and substrate with no interface separation" in this invention can be achieved. For example, the preparation of textured plastic films can be achieved by adjusting the processing temperature and process parameters between HDPE and LLDPE, HDPE and LDPE, and LLDPE and LDPE.

[0055] Therefore, after reading this application, those skilled in the art can extend the technical solution of this invention to other thermoplastic systems without creative effort, and these extended solutions all fall within the protection scope of this application.

[0056] II. Detailed Implementation Method of Preparation This invention also provides a method for preparing the above-mentioned textured plastic film, using... Figure 1 and Figure 2 The preparation apparatus shown includes the following steps: Preparation of S1 blown film device: The blown film device includes a primary extruder 1, a pellet conveying device 3, a secondary extruder 2, and a die head 4. The primary extruder 1 and the secondary extruder 2 are arranged in series along the material conveying direction. The feed port of the secondary extruder 2 receives the material conveyed by the primary extruder 1 and the pellet conveying device 3, and the discharge port is connected to the die head 4. The die head 4 can be a single die head or a compound die head.

[0057] The primary extruder 1 is used to heat, melt, and plasticize the plastic raw material to form a homogeneous melt of substrate 8 with constant pressure and stable flow rate. The secondary extruder 2 is used to knead and mix the melt of substrate 8 with the granules 7, so that the granules 7 are uniformly dispersed in the melt, and the temperature is controlled so that only the surface of the granules 7 melts while the main body remains solid. The mixture is then conveyed to the die head 4 at a constant pressure and quantity. The granule conveying device 3 is preferably a granule metering conveying device, used to continuously and quantitatively convey the granules 7 to the feed port of the secondary extruder 2.

[0058] S2 Substrate Preparation and Particle Delivery: Start the primary extruder 1 and feed plastic raw materials (such as HDPE, LLDPE, etc.) into the feed port of the primary extruder 1. After being heated, melted and plasticized, the melt of the base material 8 is formed and continuously conveyed to the feed port of the secondary extruder 2 through the discharge port of the primary extruder 1.

[0059] Simultaneously, the particle conveying device 3 is activated to continuously and quantitatively feed particles 7 into the feed inlet of the secondary extruder 2. The particle size of particles 7 is preferably 2mm to 5mm, more preferably 2mm to 4mm. The composition of particles 7 can be the same as or different from that of the base material 8. The composition of particles 7 and base material 8 is independently selected from one of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE), or a mixture of any two or three.

[0060] By adjusting the variable frequency speed of the particle conveying device 3, the amount of particles 7 fed per unit time can be controlled, thereby controlling the distribution density of the rough particles. When the speed of the particle conveying device 3 is zero, the particle supply stops, and the device can switch to smooth geomembrane production.

[0061] S3 Secondary Mixing Conveyor: The secondary extruder 2 receives a mixture of substrate 8 melt from the primary extruder 1 and granules 7 from the granule conveying device 3. When the secondary extruder 2 is started, the extrusion screw 5 inside rotates, and through the multi-stage shearing and mixing structure of the feeding section 501, compression section 502, metering section 503 and mixing section 504, the two-phase materials are subjected to forced shearing, dispersion and kneading.

[0062] During this process, under the alternating action of the shearing teeth 504a and the mixing tank 504b of the mixing section 504, the melt of the substrate 8 and the particles 7 are thoroughly dispersed and evenly distributed within the melt, preventing particle agglomeration and localized segregation. Simultaneously, the temperature of each section of the secondary extruder 2 is precisely controlled by an independent zone temperature control module, ensuring that only the surface of the particles 7 melts while the main body remains solid, forming semi-molten particles with a "molten surface and solid core." After the surface melting, the particle size of the remaining solid core portion is one-tenth to one-quarter of the initial particle size of the particles 7.

[0063] The temperature of the primary extruder 1 is controlled at 170℃~220℃, and the temperature of the secondary extruder 2 is controlled at 160℃~200℃. The temperature of the primary extruder 1 is relatively high to ensure that the plastic raw material is fully melted and plasticized; the temperature of the secondary extruder 2 is relatively low to control that only the surface of the granules 7 melts, while the main body remains solid. When the temperature of the secondary extruder 2 is higher than 200℃, the granules 7 may over-melt, resulting in insufficient protrusion height after inflation; when the temperature of the secondary extruder 2 is lower than 160℃, the granules 7 may not melt at all, failing to form effective fusion and anchoring with the substrate 8, affecting the bonding stability of the granules.

[0064] S4 Membrane formation: The mixture is extruded through the die head 4 and blown to form a bubble-like film 6.

[0065] When die 4 is a single die, the composite melt containing particles is extruded from the die orifice through a single fluid channel and inflated under air pressure to form a single-layer film 6. During this process, the substrate 8 is completely melted and deforms rapidly; the particles 7 are not completely melted and deform slowly. After inflation, the thickness of the substrate 8 of the film 6 decreases. When the particle size of the particles 7 is larger than the thickness of the substrate of the film 6, the particles 7 protrude from the surface of the substrate 8, forming a rough surface.

[0066] When the die head 4 is a composite die head and a single-sided roughened composite film is being prepared, the roughened layer melt containing particles 7 is conveyed through the roughened layer melt channel 401, and the smooth layer melt is conveyed through the smooth layer melt channel 402. The two are combined and pressed together at the pressing channel 403 to form a double-layer composite melt in which the roughened layer 9 and the smooth layer 10 are tightly bonded. Then, they are extruded together through the same die. The composite melt is blown up under air pressure to form the composite film 6. During this process, the particles 7 in the roughened layer 9 do not completely melt. After blowing, the particles 7 protrude from the outer surface of the roughened layer 9, forming a rough surface, while the smooth layer 10 remains smooth and dense.

[0067] When the die head 4 is a composite die head and a double-sided roughened composite film is prepared, the two roughened layer melts are respectively transported through the two roughened layer melt channels 401 to both sides of the smooth layer melt channel 402, and merged and pressed with the smooth layer melt at the pressing channel 403 to form a three-layer composite structure of roughened layer-smooth layer-roughened layer, which is then extruded together through the same die. The composite melt is blown up under air pressure to form a three-layer composite film 6. During this process, the particles 7 in the two roughened layers do not completely melt. After blowing, the particles 7 protrude from the outer surfaces of both sides of the film 6, forming a double-sided roughened surface, while the middle smooth layer 10 remains smooth and dense.

[0068] When the die head 4 is provided with a spiral groove annular distribution structure 404, the composite melt containing particles is evenly distributed along the circumference of the die head through the spiral groove annular distribution structure 404 to form an annular homogeneous rough surface layer melt, which further ensures that the thickness of the material output and the particle distribution density of the entire die head remain consistent.

[0069] In step S4, the protrusion height of particle 7 protruding from the surface of substrate 8 is 8% to 50% of the thickness of substrate 8. The protrusion height can be controlled in the following ways: (1) the temperature is controlled by the independent zone temperature control module of the secondary extruder 2 to adjust the melting degree of particle 7, thereby controlling the final protrusion size of particle 7; (2) by selecting the initial particle size of particle 7, the larger the particle size, the greater the final protrusion height; (3) by adjusting the blow-up ratio, the larger the blow-up ratio, the more the substrate thickness is reduced, and the greater the relative protrusion height of the particle.

[0070] S5 Cooling and Shaping: The membrane 6 moves upward under traction. When it passes the cooling mechanism 11 located above the die head 4, the cooling mechanism 11 blows air or sprays cooling water onto the surface of the membrane 6, causing the membrane 6 to cool and solidify rapidly, forming a stable rough surface structure. The cooling and solidification temperature and time can be adjusted appropriately according to the material and thickness of the membrane 6.

[0071] S6 Folding Traction: After cooling and setting, the film 6 continues to move upwards, guided and folded into a flat sheet by the herringbone plate 12, and then pulled out by the traction roller 13 to the subsequent winding device. By adjusting the rotation speed of the traction roller 13, the traction speed of the film 6 and the final thickness of the film can be controlled.

[0072] Generality of blown film process It is understood that the blow molding method of the present invention is not limited to the bottom-blowing water-cooling process; the top-blowing air-cooling process can also be used, as long as the blow molding can be achieved and a rough surface structure can be obtained. The choice of blow molding process mainly affects the cooling rate and crystallization behavior of the film bubble, but does not affect the realization of the core principle of "incomplete melting of particles - blow molding and protrusion - formation of rough surface" in the present invention. Regardless of whether top-blowing air-cooling or bottom-blowing water-cooling is used, as long as the conditions of complete melting of the substrate and incomplete melting of the particles are met, the one-time molding of the rough surface structure can be achieved. Therefore, the embodiments of the present invention are described using bottom-blowing water-cooling as an example, but this is not intended to limit the blow molding method of the present invention.

[0073] III. Product Structure Verification The core structural features of the rough-surfaced plastic film described in this invention can be verified through the following methods: (I) Verification of the particle-embedded fusion structure The cross-section of the textured plastic film of this invention was observed using a scanning electron microscope (SEM). In the SEM image, particles 7 are visible embedded within the surface layer of the substrate 8, with no clear boundary between particles 7 and the substrate 8; they are fused together, and there are no gaps or voids at the interface. In contrast, in the SEM cross-sectional image of the spray-textured product, there is a clear boundary line or interface gap between the particles and the film surface.

[0074] (ii) Verification of membrane compactness Cross-sectional SEM observation or density testing was used. The product of this invention exhibits a uniform and dense structure in the cross-sectional SEM image, without microbubbles or pores. In contrast, the product produced by the nitrogen-foamed roughening process shows numerous microbubbles and broken pores in the cross-sectional SEM image. Density testing revealed that the density of the product of this invention is close to the theoretical density of the substrate, while the density of the nitrogen-foamed product is significantly lower than the theoretical density of the substrate.

[0075] (iii) Measurement of particle protrusion height The surface of the product of this invention can be measured using a surface roughness meter or a three-dimensional profilometer to determine the height of the particles 7 protruding from the surface of the substrate 8; or the measurement can be performed according to the national standard GB / T17643-2025 for measuring roughness. The particle protrusion height of the product of this invention is 8% to 50% of the substrate thickness, with uniform protrusion height and small fluctuation range. In contrast, the roughness height of nitrogen-foamed products fluctuates greatly, and the particle protrusion height of spray-polished products is inconsistent and prone to detachment.

[0076] IV. Examples Example 1 Preparation of a single-layer textured HDPE geomembrane.

[0077] Raw materials: The base material 8 is made of HDPE (high-density polyethylene, melt index MI = 0.3 g / 10 min, density ρ = 0.949 g / cm³), and the granules 7 are made of HDPE granules with the same composition as the base material 8, with a particle size of 2 mm to 3 mm.

[0078] Equipment parameters: Single die head is used. The primary extruder 1 and the secondary extruder 2 are arranged in series. The rated melt delivery flow rate of the secondary extruder 2 is 32% greater than that of the primary extruder 1. The secondary extruder 2 is equipped with an extrusion screw 5. The mixing section 504 of the screw 5 is composed of staggered shearing teeth 504a and mixing grooves 504b.

[0079] Process parameters: The temperature of the primary extruder 1 is controlled at 190℃~210℃, and the temperature of the secondary extruder 2 is controlled at 170℃~185℃. The rotation speed of the pellet conveying device 3 is set to the standard speed, and the pellet distribution density is approximately 10~12 pellets / cm². The blow-up ratio is controlled at 1.5:1~4:1, and the traction speed is controlled at 8~12m / min. The cooling air temperature is 20℃~30℃.

[0080] Product Performance: The prepared single-layer textured HDPE geomembrane has uniformly protruding particles on its surface, with a protrusion height of approximately 15%–30% of the substrate thickness. The particles are embedded within the substrate surface, integrally fused with it without interface separation. The membrane has a dense internal structure without foamed micropores. The product has a coefficient of friction ≥0.45 (tested according to GB / T 17643), tensile strength ≥25MPa, and puncture resistance ≥400N, fully meeting the requirements of GB / T 17643 standard.

[0081] Example 2 Prepare a composite double-layer textured HDPE geomembrane (single-sided textured).

[0082] Raw materials: The rough surface layer 9 substrate is made of HDPE and LLDPE blend (HDPE:LLDPE=80:20), the granules 7 are made of HDPE granules with a particle size of 3mm to 5mm; the smooth surface layer 10 is made of HDPE raw material.

[0083] Device parameters: A composite die head is used, with a rough-surface melt flow channel 401 and a smooth-surface melt flow channel 402 inside the die head. The two flow channels converge at the pressing channel 403.

[0084] Process parameters: The temperature of the primary extruder 1 is controlled at 180℃~200℃, and the temperature of the secondary extruder 2 is controlled at 160℃~175℃. The speed of the pellet conveying device 3 is set to high speed, and the pellet distribution density is approximately 13~15 pellets / cm². The blow-up ratio is controlled at 2.5:1~3.5:1, and the traction speed is controlled at 6~10m / min.

[0085] Product Performance: The prepared composite double-layer textured HDPE geomembrane has a textured layer 9 located on the outer surface of the membrane. The protruding height of the particles is approximately 20%–40% of the thickness of the textured layer, with a high particle density and an interfacial friction coefficient ≥0.55. The smooth layer 10 remains smooth and dense, playing a major role in seepage prevention and mechanical load-bearing. The particles are embedded within the textured layer, integrally fused with the textured layer substrate, without interfacial separation. The membrane is dense and free of pores. It is suitable for seepage prevention projects with stringent requirements for resisting slippage, such as high slopes and tailings dams.

[0086] Example 3 Prepare a composite three-layer textured HDPE geomembrane (with textured surfaces on both sides).

[0087] Raw materials: The two textured layers 9 are made of HDPE and LLDPE blends (HDPE:LLDPE = 70:30), and the granules 7 are made of HDPE granules with a particle size of 2mm to 4mm; the middle smooth layer 10 is made of HDPE raw material. The raw material formulations of the two textured layers are the same.

[0088] Equipment parameters: A composite die head is used, with two rough-surface melt channels 401 and one smooth-surface melt channel 402 inside the die head. The two rough-surface melt channels 401 are located on both sides of the smooth-surface melt channel 402. The two rough-surface layers are fed by two independent primary extruders 1 and 2, and a pellet conveying device 3, respectively.

[0089] Process parameters: The temperatures of both primary extruders 1 are controlled at 180℃~200℃, and the temperatures of both secondary extruders 2 are controlled at 165℃~180℃. The particle conveying devices 3 on both sides rotate at the same speed, and the particle distribution density is approximately 10~13 particles / cm². The blow-up ratio is controlled at 2.5:1~3.5:1, and the traction speed is controlled at 6~10m / min.

[0090] Product Performance: The prepared three-layer composite textured HDPE geomembrane has a structure of "textured layer-smooth layer-textured layer". Both outer surfaces have a uniform textured structure, with particle protrusion height approximately 18%–35% of the thickness of each textured layer. The friction coefficient on both sides is ≥0.50. The middle smooth layer remains smooth and dense. The three layers are integrally molded in-mold without delamination gaps, resulting in a strong bond. The membrane is dense internally, without foamed micropores. The product has a high interfacial friction coefficient on both sides, making it suitable for seepage prevention projects such as high slopes and landfill closures where both sides require high friction performance.

[0091] Example 4 Prepare a composite three-layer textured LLDPE geomembrane (with textured surfaces on both sides and different parameters on each side).

[0092] Raw materials: The two rough surface layers 9 are made of LLDPE (melt index MI = 1.0 g / 10 min, density ρ = 0.920 g / cm³), and the granules 7 are made of HDPE granules (different from the composition of the base material). The particle size of the rough surface layer on the left is 2 mm to 3 mm, and the particle size of the rough surface layer on the right is 3 mm to 4 mm. The middle smooth surface layer 10 is made of LLDPE raw material.

[0093] Device parameters: Same as in Example 3, using a composite die head, with the two roughened layers respectively supplied by two independent primary extruder 1, secondary extruder 2 and particle conveying device 3.

[0094] Process parameters: The temperature of both primary extruders 1 is controlled at 170℃~190℃; the temperature of the left secondary extruder 2 is controlled at 170℃~180℃, and the temperature of the right secondary extruder 2 is controlled at 175℃~185℃; the rotation speed of the two particle conveying devices 3 is independently set, with the left side at a low speed (particle density of approximately 2~4 particles / cm²) and the right side at a high speed (particle density of approximately 6~9 particles / cm²). The blow-up ratio is controlled at 2:1~2.5:1, and the traction speed is controlled at 8~12m / min.

[0095] Product Performance: The prepared three-layer composite textured LLDPE geomembrane has different particle protrusion sizes and distribution densities on both sides of the textured surface. The left side has particle protrusions approximately 20%–30% of the substrate thickness, with a sparser distribution and a friction coefficient ≥0.40; the right side has particle protrusions approximately 30%–50% of the substrate thickness, with a denser distribution and a friction coefficient ≥0.55. The particles are embedded within the textured layer and integrally fused with the substrate, without interface separation. The membrane is dense internally, without foamed micropores. This product can be configured with different sides to correspond to different working conditions (e.g., one side in contact with soil, the other side in contact with the cushion layer) to achieve differentiated friction performance configurations according to engineering needs.

[0096] Example 5 Preparation of single-layer textured LLDPE geomembrane (with different particle and substrate compositions).

[0097] Raw materials: The base material 8 is LLDPE (melt index MI = 1.0 g / 10 min, density ρ = 0.920 g / cm³), and the granules 7 are HDPE granules (different from the base material composition, HDPE has a higher melting point than LLDPE), with a particle size of 2 mm to 4 mm.

[0098] Device parameters: Same as in Example 1.

[0099] Process parameters: The temperature of the primary extruder 1 is controlled at 170℃~190℃, and the temperature of the secondary extruder 2 is controlled at 160℃~180℃. The speed of the pellet conveying device 3 is set to low speed, and the pellet distribution density is approximately 10~12 pellets / cm². The blow-up ratio is controlled at 3.5:1~4.5:1, and the traction speed is controlled at 10~15m / min.

[0100] Product Performance: The prepared single-layer textured LLDPE geomembrane, due to the use of HDPE material in granules 7, has a higher melting point than the LLDPE substrate. The granules exhibit lower melting degree and greater protrusion height at the secondary extrusion temperature, approximately 30%–50% of the substrate thickness. Although the granules and substrate have different compositions, they are both polyethylene materials and possess good compatibility, fusing together at the interface without separation. The membrane is dense internally, free of foamed micropores, and exhibits excellent mechanical properties, making it suitable for seepage control projects in low-temperature environments.

[0101] V. Comparative Examples Comparative Example 1 (Product with spray coating process) Textured HDPE geomembranes are prepared using a traditional spray-texturing post-processing technique. First, smooth HDPE geomembranes are prepared using a conventional blown film process. Then, HDPE granules in a hot-melt state are sprayed onto the surface of the smooth geomembrane using an independent spraying production line. After the granules cool and solidify, a textured surface is formed.

[0102] Compared with Example 1 of the present invention, the rough geomembrane prepared in Comparative Example 1 has the following problems: (1) The particles and the membrane surface are only physically bonded together, and there is a clear interface boundary line. After the friction test, the particle shedding rate is significantly higher than that of the present invention (the shedding rate after 1000 friction cycles is >20%, while that of the present invention is <1%); (2) After the particles fall off, the membrane surface forms pit defects, and the friction performance is severely degraded; (3) The product friction performance gradually decreases with the extension of service time, making it difficult to meet the requirements of long-term seepage prevention projects.

[0103] Comparative Example 2 (Products produced using nitrogen foaming process) Textured HDPE geomembranes are prepared using a traditional nitrogen foaming and roughening process. During the multi-layer co-extrusion blow molding process, high-pressure nitrogen is injected into the molten polymer on the surface, and the irregular uneven surface is formed when the nitrogen escapes from the membrane surface.

[0104] Compared with Example 1 of the present invention, the rough geomembrane prepared in Comparative Example 2 has the following problems: (1) There are a large number of microporous structures inside and on the surface of the membrane (microbubbles with a diameter of 5 to 50 μm can be seen in the cross-sectional SEM image), the tensile strength is reduced by 20% to 30% compared with the present invention, and the puncture resistance is reduced by 25% to 35% compared with the present invention; (2) The size and distribution uniformity of microbubbles are difficult to control precisely, the fluctuation range of the roughness height is ±40%, while the fluctuation range of the roughness height of the present invention is ±10%; (3) The broken bubbles affect the seepage prevention performance, the water vapor transmission rate is 2 to 3 times higher than that of the present invention, and it is difficult to meet the requirements of high-level seepage prevention projects.

[0105] Comparative Example 3 (embossed products) Textured HDPE films are prepared using an embossing / roll pressing process. The HDPE film surface is pressed using rollers with raised or recessed textures to create the textured surface.

[0106] Compared with the present invention, the product prepared in Comparative Example 3 has the following problems: (1) The embossing process causes the membrane surface to be stretched and thinned locally at the concave and convex textures, resulting in poor thickness uniformity (thickness deviation > ±15%); (2) The rough surface structure formed by roller pressing is easily flattened during subsequent winding and laying, resulting in poor rough surface durability and significantly reduced friction performance as storage and laying time increases; (3) Roller pressing causes local molecular orientation, which seriously affects the uniformity of the overall mechanical properties of the geomembrane and causes internal stress, which has a negative impact on aging resistance and stress cracking resistance.

[0107] VI. Industrial Application Prospects The textured plastic film product of this invention has excellent properties such as stable and durable particle bonding, dense and non-porous film, and uniform and controllable texture parameters, and can be widely used in the following fields: (1) Landfill seepage prevention project: As a seepage prevention liner for the bottom and side walls of the landfill, the rough surface structure provides sufficient interfacial friction resistance to prevent the seepage prevention layer from slipping under the load of the landfill.

[0108] (2) Tailings dam seepage prevention project: During the tailings storage process, the rough surface geomembrane provides stable friction performance to ensure the long-term safe operation of the tailings dam.

[0109] (3) Water conservancy dam seepage prevention project: used for seepage prevention core wall or panel of dam, rough surface structure enhances the interaction between membrane and upstream and downstream cushion materials.

[0110] (4) Seepage prevention project for chemical solid waste storage sites: In chemical solid waste storage sites, rough geomembrane provides a reliable seepage barrier and friction stability.

[0111] (5) Environmental remediation engineering: In projects such as contaminated site isolation and site closure, the double-sided rough surface structure provides frictional resistance at the upper and lower interfaces, ensuring the overall stability of the covering system.

[0112] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A textured plastic film, characterized in that: The rough plastic film is a blow-molded integral film (6), and at least one side surface of the film (6) has a rough surface formed by incompletely melted particles (7). The particles (7) are embedded in the surface layer of the membrane and are integrally fused with the substrate (8) of the membrane. There is no interface separation between the particles (7) and the substrate (8) of the membrane.

2. The textured plastic film according to claim 1, characterized in that: The particles (7) are uniformly distributed on the surface of the membrane; the composition of the particles (7) may be the same as or different from the composition of the substrate of the membrane.

3. The textured plastic film according to claim 2, characterized in that: The composition of the particles is the same as that of the substrate of the membrane, which is one of high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a mixture of any two or three of them.

4. The textured plastic film according to claim 2, characterized in that: The composition of the particles is different from that of the substrate of the membrane, and the composition of the particles and the substrate of the membrane are one of high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a mixture of any two or three of them.

5. The textured plastic film according to claim 1, characterized in that: The height of the particle (7) protruding from the substrate is 8% to 50% of the substrate thickness.

6. The textured plastic film according to claim 1, characterized in that: The rough plastic film is a single-layer film or a composite film; both sides of the single-layer film have the rough surface; the composite film includes a rough layer (9) and a smooth layer (10); the rough layer (9) is located on at least one outer surface of the composite film; the particles (7) are embedded in the rough layer (9); the rough layer (9) and the smooth layer (10) are an in-mold composite integral molding structure.

7. The textured plastic film according to claim 1, characterized in that: It is made using the following method: S1 blown film device preparation: The blown film device includes a primary extruder (1), a pellet conveying device (3), a secondary extruder (2), and a die head (4); S2 Substrate Preparation and Particle Conveying: Start the primary extruder (1) to heat and melt the plastic raw material to form a melt of the substrate and convey it to the feed port of the secondary extruder (2); at the same time, start the particle conveying device (3) to feed the particles (7) into the feed port of the secondary extruder (2); S3 Secondary mixing and conveying: The secondary extruder (2) receives the mixture of the substrate and the particles (7), and mixes and kneads it so that the particles (7) are evenly dispersed in the melt, and controls the temperature so that only the surface of the particles (7) melts and the main body retains a solid form. S4 Membrane formation: The mixture is extruded through the die (4) and blown to form a bubble-like membrane (6). The substrate is completely melted and deformed, while the particles (7) are not completely melted. After blowing, the substrate thickness of the membrane (6) is reduced, and the particles (7) protrude from the substrate surface to form a rough surface.

8. The textured plastic film according to claim 7, characterized in that: In step S2, the particle size of the particle (7) is 2 mm to 5 mm; in step S4, the height of the particle (7) protruding from the substrate is 8% to 50% of the substrate thickness.

9. The textured plastic film according to claim 7, characterized in that: The die head (4) is a single die head or a composite die head. The single die head is provided with a single fluid channel, and the composite die head is provided with a pressing channel (403), at least one rough melt channel (401) and at least one smooth melt channel (402). The pressing channel (403) is used to press the film layer formed by the rough melt channel (401) and the smooth melt channel (402) to form a composite film. In step S2, the particle feeding amount per unit time is controlled by adjusting the rotation speed of the particle conveying device (3), thereby controlling the particle distribution density of the rough surface (7). In step S3, the temperature of the secondary extruder (2) is controlled by the independent zone temperature control adjustment module to adjust the melting degree of the particles (7), thereby controlling the final protrusion size of the particles (7); After step S3, the process also includes: S4 cooling and shaping: cooling the blown bubble; S5 Folding Traction: The cooled film bubble is folded into a flat sheet film by the herringbone plate guide, and then pulled out by the traction roller.

10. The textured plastic film according to claim 7, characterized in that: In steps S1 and S2, the composition of the particles and the substrate composition of the membrane are one or any two or a mixture of three of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE); the temperature of the primary extruder (1) is controlled at 170℃-220℃, and the temperature of the secondary extruder (2) is controlled at 160℃-200℃.

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