Needleless ultrasonic composite geotextile multi-layer composite process

Abstract

This invention discloses a multi-layer composite process for needle-free ultrasonic composite geotextile. This invention belongs to the field of geosynthetic materials technology. Specifically, it includes the following steps: (1) forming a geotextile base layer by opening, combing, web-laying, and needle punching short fibers; (2) composited at least one functional intermediate layer on the base layer surface; (3) covering the outermost surface with a geotextile surface layer; (4) performing hot-melt welding composite of the layered materials using an ultrasonic welding head with a dot-matrix or continuous line welding trajectory, causing the fiber molecular chains of each layer to melt and interpenetrate due to frictional heat at the welding point, forming needle-free welded joints after cooling; (5) performing secondary welding on the overlapping edges and stress-bearing parts; (6) winding after tension leveling and cooling. This invention uses ultrasonic hot-melt welding to replace the traditional needle punching / sewing process, fundamentally eliminating needle-hole defects, and requiring no adhesives, making it environmentally friendly and pollution-free.

Description

Technical Field

[0001] This invention belongs to the field of geosynthetic materials technology, specifically referring to a multi-layer composite process for non-porous ultrasonic composite geotextiles and its application method. Background Technology

[0002] Composite geotextiles are a new type of geosynthetic material made by combining two or more geotextile materials (such as geotextiles, geomembranes, geogrids, etc.) through a specific process. They are widely used in highway and railway subgrade reinforcement, water conservancy seepage prevention projects, landfill covering, tailings dam seepage prevention and control, coastal protection, and other scenarios. Composite geotextiles have multiple functions such as filtration, drainage, isolation, reinforcement, and seepage prevention, making them an indispensable functional material in modern geotechnical engineering.

[0003] Currently, the main composite processes for composite geotextiles in industry include the following:

[0004] (1) Needle-punching composite method: This method involves puncturing multiple layers of material with needles, and achieving interlayer bonding through fiber entanglement. The disadvantage of this method is that the needle-punching process leaves needle holes in the composite material, which become leakage channels and seriously affect the impermeability of the composite geotextile. Especially in water conservancy projects and seepage prevention projects, leakage problems caused by needle holes may lead to engineering accidents.

[0005] (2) Hot melt bonding method: multi-layer materials are hot-pressed and bonded together by heating rollers. This method requires a high processing temperature, which can easily cause thermal damage, deformation or even melting through heat-sensitive intermediate layers such as geomembranes. In addition, the use of adhesives increases costs and environmental burden.

[0006] (3) Adhesive bonding method: The layers are bonded together using adhesives. This method has the problem of interlayer delamination due to adhesive aging, and the adhesive may pollute the water environment, which does not meet environmental protection requirements.

[0007] (4) Sewing composite method: The layers are sewn together with sewing thread. This method will also leave needle holes.

[0008] In summary, existing composite processes all have varying degrees of defects: needle punching and sewing methods produce pinholes that affect impermeability; hot-melt methods easily damage heat-sensitive materials; and adhesive bonding methods suffer from aging and environmental problems. Therefore, developing a composite process that can achieve pinhole-free bonding, minimize damage to each layer of material, achieve high interlayer bonding strength, and is environmentally friendly is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] This invention proposes a multi-layer composite process for needle-free ultrasonic composite geotextiles, which effectively solves the problems of needle-punching / sewing composites causing pinholes that reduce impermeability, hot-melt composites that easily damage heat-sensitive materials, and adhesive composites that pose a risk of aging and detachment.

[0010] The technical solution adopted in this invention is as follows: This invention proposes a multi-layer composite process for needle-free ultrasonic composite geotextiles, including the following steps:

[0011] (1) Base layer preparation: short fibers are opened, combed, laid and pre-needled to form an initial fiber web, and then the geotextile base layer is formed by the main needle punching process. The surface density of the geotextile base layer is 150~600g / m².

[0012] (2) Intermediate layer composite: At least one functional intermediate layer is composited on the upper and lower surfaces of the geotextile base layer, wherein the functional intermediate layer is selected from one or more of geomembrane, geogrid, bentonite waterproof blanket, and drainage mesh core;

[0013] (3) Surface covering: A geotextile surface layer is covered on the outermost surface of the composite material, and the surface density of the surface layer is 80~400g / m²;

[0014] (4) Ultrasonic pinhole-free welding composite: The laminated material obtained in step (3) is fed into an ultrasonic welding device. The laminated material is hot melt welded and composited by the ultrasonic welding head in a dot matrix or continuous line welding trajectory. The fiber molecular chains of each layer of material melt and interpenetrate due to frictional heat at the welding point. After cooling, a pinhole-free welding joint is formed.

[0015] (5) Perform secondary welding on the lap joints and stress-bearing parts;

[0016] (6) Tension leveling and winding: The welded composite material is leveled by tension rollers to eliminate internal stress, and then wound up after being shaped by cooling rollers to obtain the finished product of needle-free ultrasonic composite geotextile.

[0017] Furthermore, the composite geotextile has a multi-layer structure, comprising at least one geotextile base layer, at least one functional intermediate layer, and at least one geotextile surface layer, with each layer connected by ultrasonic welding joints to achieve a pinhole-free composite connection.

[0018] Further, in step (1), the short fiber is at least one of polyester fiber, polypropylene fiber, polyethylene fiber, polyamide fiber or polypropylene / polyester bicomponent fiber, and the fineness of the short fiber is 2~22 dtex and the length is 38~76 mm.

[0019] Further, in step (1), the needle density of the main needle punching process is 200~800 needles / cm², the needle punching depth is 6~18mm, the thickness of the geotextile base layer is 1.5~8mm, the longitudinal tensile strength is ≥8kN / m, and the transverse tensile strength is ≥6kN / m.

[0020] Further, in step (2), when the functional intermediate layer is a geomembrane, the geomembrane is one or more of high-density polyethylene film, low-density polyethylene film, linear low-density polyethylene film or EVA film.

[0021] Furthermore, the thickness of the geomembrane is 0.2~2.0 mm.

[0022] Furthermore, in step (2), when geomembrane and geogrid are used as functional intermediate layers at the same time, the geogrid is first attached to the surface of the geotextile base layer, and then the geomembrane is covered on the outside of the geogrid to form a multi-layer structure of "base layer + geogrid + membrane".

[0023] Furthermore, in step (4), the welding trajectory arrangement of the ultrasonic welding head is one or more of the following: dot matrix arrangement, continuous line arrangement, and edge reinforcement arrangement.

[0024] Furthermore, the dot-matrix arrangement of welding points is uniformly distributed in a square or rhomboid dot matrix; the continuous line arrangement of welding lines is distributed in straight segments, broken segments, or wavy segments, with a spacing of 5~30mm between adjacent welding lines and a width of 0.8~4mm for a single welding line; the edge reinforcement arrangement of the material has a welding point density within a 50~150mm range on the edge area that is greater than that in the center area, and the area ratio of welding points in the edge area is 1.5~3 times that in the center area.

[0025] Furthermore, in step (4), during the welding process, the ultrasonic frequency is controlled at 20~40kHz, the amplitude at 30~80μm, the welding pressure at 0.3~1.5MPa, the welding speed at 5~30m / min, the center-to-center distance between adjacent welding points is 2~15mm, the diameter of a single welding point is 0.5~3mm, and the area of ​​the welding joint accounts for 3%~25% of the total composite area.

[0026] Furthermore, in step (5), the ultrasonic power of the secondary welding is increased by 10% to 30% compared with the primary welding in step (4).

[0027] Furthermore, in step (6), the tension of the tension roller group is controlled at 50~500N / m, the temperature of the cooling roller is controlled at 5~25℃, the winding tension during winding is 30~300N / m, and the flatness deviation of the finished product after winding is ≤3mm / m.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] (1) No pinhole design, excellent seepage prevention performance: Ultrasonic welding does not require physical puncture, and the composite process does not produce any pinholes or needle holes in the material. Tests show that the composite geotextile prepared by this invention remains leak-proof for 24 hours under 0.5MPa water pressure, with a seepage resistance pressure ≥0.3MPa, far superior to needle-punched composite products. This is of great significance for applications requiring high sealing performance, such as water conservancy seepage prevention projects and landfill covering.

[0030] (2) High interlayer bonding strength: Ultrasonic welding enables molecular-level melting and interpenetration of materials at the bonding point, rather than simple mechanical entanglement or surface bonding. The measured interlayer peel strength is ≥0.8kN / m, which is significantly higher than that of adhesive composite products (usually 0.3~0.5kN / m), and there is no risk of adhesive aging and peeling.

[0031] (3) Minimal damage to heat-sensitive materials: Ultrasonic welding involves localized, instantaneous heating (millisecond level), with heat concentrated in a small area at the welding point. The overall material temperature rise is small (<5℃), unlike hot melt rollers which can cause large-area thermal deformation or melt-through of the geomembrane. This allows the present invention to safely laminate heat-sensitive geomembranes such as HDPE and EVA.

[0032] (4) Environmentally friendly and pollution-free: The entire composite process does not require any adhesives, solvents or other chemical additives. It is a purely physical welding process with no VOC emissions, which meets the requirements of green manufacturing.

[0033] (5) The process parameters are highly adjustable and have a wide range of applications: By adjusting the ultrasonic frequency, amplitude, pressure, speed and welding trajectory pattern, it can adapt to the composite requirements of different thicknesses and material combinations, and is suitable for various product types such as one cloth and one film, two cloth and one film, cloth and film grid composite.

[0034] (6) High production efficiency: Ultrasonic welding speed is fast (5~30m / min), suitable for continuous large-scale production, and the unit energy consumption is lower than that of hot melt composite process. Attached Figure Description

[0035] Figure 1 This is an overall flow chart of a needle-free ultrasonic composite geotextile multilayer composite process proposed in this invention.

[0036] Figure 2 This is a schematic cross-sectional view of the finished product of the multi-layer composite process of needle-free ultrasonic composite geotextile proposed in this invention (taking two fabrics and one membrane as an example), wherein ① geotextile surface layer - polyester / polypropylene short fiber needle-punched nonwoven fabric, providing surface protection and puncture resistance; ② HDPE geomembrane - high-density polyethylene impermeable layer; ③ geotextile base layer - polyester short fiber needle-punched nonwoven fabric, providing main mechanical support.

[0037] Figure 3This is a schematic diagram of three trajectory arrangements for the ultrasonic welding joints in a multi-layer composite process of needle-free ultrasonic composite geotextile proposed in this invention, wherein (a) dot matrix (square); (b) dot matrix (rhombus); and (c) continuous line (wavy line).

[0038] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] Two-layer geotextile with one-layer membrane

[0042] Base layer: Polyester staple fiber (6.7 dtex fineness, 54 mm length), areal density 350 g / m²

[0043] Intermediate layer: HDPE geomembrane, 0.8mm thick

[0044] Surface layer: Polypropylene short fibers (11 dtex fineness, 64 mm length), areal density 200 g / m²

[0045] Process steps: (1) The polyester short fibers are opened by an opening machine, combed by a carding machine, cross-laid by a web laying machine, pre-needled (120 needles / cm², depth 8mm) and main needled (450 needles / cm², depth 12mm) to obtain a geotextile base layer with a thickness of 4.2mm. The longitudinal tensile strength is measured to be 12.5kN / m and the transverse tensile strength is 9.8kN / m.

[0046] (2) Cover the surface of the base layer with HDPE geomembrane and flatten and adhere it by guide roller.

[0047] (3) Cover the upper surface of the geomembrane with a polypropylene surface layer.

[0048] (4) The ultrasonic welding device is used. The parameters are set as follows: frequency 28kHz, amplitude 50μm, welding pressure 0.8MPa, welding speed 12m / min. A square dot matrix is ​​used, with a center distance of 8mm between adjacent welding points, a single point diameter of 1.5mm, and a welding area ratio of 11%. The welding head end face is covered with a grid texture with a depth of 0.1mm.

[0049] (5) The overlapping edges, each 100mm wide, are reinforced by secondary welding, increasing the power by 30%;

[0050] (6) Leveling by tension roller group (tension 200N / m) → Shaping by cooling roller (15℃) → winding (winding tension 100N / m).

[0051] Test results:

[0052] Interlayer peel strength: 1.21 kN / m; Water pressure resistance: 0.52 MPa; Permeability coefficient: 2.3 × 10⁻ 1 ²cm / s; 0.5MPa water pressure 24h pressure holding test: no leakage; longitudinal tensile strength: 13.2kN / m; transverse tensile strength: 10.1kN / m; flatness deviation: 1.8mm / m; weld appearance: no obvious pinholes.

[0053] Example 2

[0054] Two-layer geotextile, one-membrane, one-grid composite geotextile

[0055] Base layer: Polypropylene short fibers (11 dtex fineness, 64 mm length), areal density 400 g / m²

[0056] Intermediate layer 1: Biaxially oriented polypropylene geogrid (longitudinal and transverse node strength ≥30kN / m)

[0057] Intermediate layer 2: LLDPE geomembrane, 0.5mm thick

[0058] Outer layer: Polyester staple fiber (6.7 dtex, 54 mm in length), areal density 250 g / m²

[0059] Process steps: (1) Polypropylene short fibers are opened, combed, laid, pre-needled, and main needled (500 needles / cm², depth 14mm) to obtain a base layer with a thickness of 5.0mm, a longitudinal breaking strength of 15.2kN / m, and a transverse breaking strength of 11.3kN / m.

[0060] (2) First, attach the geogrid to the upper surface of the base layer, and then cover the geogrid with an LLDPE geomembrane to form a "base layer + geogrid + membrane" structure.

[0061] (3) Covered with polyester surface layer.

[0062] (4) Ultrasonic welding parameters: frequency 35kHz, amplitude 40μm, welding pressure 1.0MPa, welding speed 8m / min. A rhomboid dot matrix arrangement is adopted, the center distance of the welding points is 6mm, the diameter of a single point is 1.2mm, and the welding area accounts for 9%.

[0063] (5) The overlapping edges, each 100mm wide, are reinforced by secondary welding, increasing the power by 20%.

[0064] (6) Tension leveling (300 N / m) → Cooling (12℃) → Winding (150 N / m).

[0065] Test results:

[0066] Interlayer peel strength: 1.45 kN / m; Peel strength of overlapping area: 1.82 kN / m (25.5% higher than that of the first welded area); Water pressure resistance: 0.48 MPa; 24-hour pressure holding at 0.5 MPa: no leakage; Tear strength: longitudinal 0.85 kN, transverse 0.72 kN; CBR burst strength: 3.2 kN.

[0067] Example 3

[0068] Composite geotextile with one fabric layer and one membrane layer (simplified structure)

[0069] Base layer and surface layer: Polyester / polypropylene bicomponent fiber (fineness 8 dtex, length 60 mm), areal density 300 g / m²

[0070] Intermediate layer: EVA geomembrane, 0.4mm thick

[0071] Process steps: (1) The bicomponent fibers are opened, combed, laid out and needled (380 needles / cm², 10mm depth) to obtain a single-layer substrate with a thickness of 3.0mm.

[0072] (2) Cover one side of the substrate with an EVA film.

[0073] (3) The other side is no longer covered with a separate surface layer (the base layer also serves as the surface layer).

[0074] (4) Ultrasonic welding parameters: frequency 20kHz, amplitude 70μm, welding pressure 0.5MPa, welding speed 25m / min. A continuous wavy line welding trajectory is adopted, with a spacing of 15mm between adjacent welding lines and a line width of 2.0mm.

[0075] (5) Perform secondary reinforcement welding on the 100mm wide overlap edges on both sides, increasing the power by 10%;

[0076] (6) Tension leveling (80 N / m) → Cooling (20℃) → Winding (60 N / m).

[0077] Test results:

[0078] Interlayer peel strength: 0.89 kN / m; Water pressure resistance: 0.35 MPa; 24-hour water pressure test at 0.5 MPa: no leakage; Permeability coefficient: 5.6 × 10⁻ 1 ³cm / s.

[0079] Example 4

[0080] Three-layer geotextile with two-layer membrane (high-end seepage prevention application)

[0081] Base layer: Polyester staple fiber, areal density 500g / m²

[0082] Intermediate layer 1: HDPE geomembrane, 1.0mm thick

[0083] Intermediate reinforcing layer: Polyester needle-punched felt, areal density 200g / m²

[0084] Intermediate layer 2: HDPE geomembrane, 1.0mm thick

[0085] Top layer: Polypropylene short fibers, surface density 300g / m²

[0086] Process steps: (1)~(3) Stack the layers one by one in the above order.

[0087] (4) Ultrasonic welding parameters: frequency 40kHz, amplitude 35μm, welding pressure 1.2MPa, welding speed 6m / min. An edge-reinforced arrangement is adopted, with the welding area within 100mm of the edge accounting for 22% and the welding area in the center area accounting for 10%. The welding head end face adopts a radial texture.

[0088] (5) All four edges are reinforced by secondary welding, increasing the power by 30%.

[0089] (6) Tension leveling (400 N / m) → Cooling (8℃) → Rewinding (250 N / m).

[0090] Test results:

[0091] Interlayer peel strength: 1.68 kN / m; Peel strength in edge reinforced zone: 2.10 kN / m; Water pressure resistance: 0.78 MPa; 72-hour pressure test at 0.5 MPa: no leakage; Permeability coefficient: 8.5 × 10⁻ 14 cm / s

[0092] Comparative Example 1

[0093] Traditional acupuncture composite technique

[0094] The same raw material ratio as in Example 1 was used, but the composite process was changed to the traditional needle-punching composite method:

[0095] Needle density: 350 needles / cm², needle depth: 15mm, other steps are the same.

[0096] Test results:

[0097] Interlayer peel strength: 0.65kN / m; water pressure resistance: 0.08MPa; obvious leakage occurs after 2 hours under 0.3MPa water pressure; pinhole density test: approximately 350 pinholes / cm².

[0098] Comparative Example 2

[0099] Adhesive bonding process

[0100] Using the same raw material ratio as in Example 1, the composite process was changed to polyurethane adhesive bonding: adhesive coating amount: 80g / m²; curing temperature: 80℃, curing time: 5min.

[0101] Test results:

[0102] Initial interlayer peel strength: 0.78 kN / m; peel strength after accelerated aging test (70℃×720h): 0.31 kN / m; water pressure resistance: 0.22 MPa; CODcr test of adhesive leachate: 185 mg / L.

[0103] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0104] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A multi-layer composite process for needle-free ultrasonic composite geotextile, characterized in that, Includes the following steps: (1) Base layer preparation: short fibers are opened, combed, laid and pre-needled to form an initial fiber web, and then the geotextile base layer is formed by the main needle punching process. The surface density of the geotextile base layer is 150~600g / m². (2) Intermediate layer composite: At least one functional intermediate layer is composited on the upper and lower surfaces of the geotextile base layer, wherein the functional intermediate layer is selected from one or more of geomembrane, geogrid, bentonite waterproof blanket, and drainage mesh core; (3) Surface covering: A geotextile surface layer is covered on the outermost surface of the composite material, and the surface density of the surface layer is 80~400g / m²; (4) Ultrasonic pinhole-free welding composite: The laminated material obtained in step (3) is fed into an ultrasonic welding device. The laminated material is hot melt welded and composited by the ultrasonic welding head in a dot matrix or continuous line welding trajectory. The fiber molecular chains of each layer of material melt and interpenetrate due to frictional heat at the welding point. After cooling, a pinhole-free welding joint is formed. (5) Perform secondary welding on the lap joints and stress-bearing parts; (6) Tension leveling and winding: The welded composite material is leveled by tension rollers to eliminate internal stress, and then wound up after being shaped by cooling rollers to obtain the finished product of needle-free ultrasonic composite geotextile.

2. The multi-layer composite process for needle-free ultrasonic composite geotextile according to claim 1, characterized in that: The composite geotextile has a multi-layer structure, comprising at least one geotextile base layer, at least one functional intermediate layer, and at least one geotextile surface layer. The layers are connected by ultrasonic welding at the joints to achieve a pinhole-free composite connection.

3. The multi-layer composite process for needle-free ultrasonic composite geotextile according to claim 1, characterized in that: In step (1), the short fiber is at least one of polyester fiber, polypropylene fiber, polyethylene fiber, polyamide fiber or polypropylene / polyester bicomponent fiber, and the short fiber has a fineness of 2~22 dtex and a length of 38~76 mm.

4. The multi-layer composite process for needle-free ultrasonic composite geotextile according to claim 1, characterized in that: In step (1), the needle density of the main needle punching process is 200~800 needles / cm², the needle punching depth is 6~18mm, the thickness of the resulting geotextile base layer is 1.5~8mm, the longitudinal tensile strength is ≥8kN / m, and the transverse tensile strength is ≥6kN / m.

5. The multi-layer composite process for needle-free ultrasonic composite geotextile according to claim 1, characterized in that: In step (2), when the functional intermediate layer is a geomembrane, the geomembrane is one or more of high-density polyethylene film, low-density polyethylene film, linear low-density polyethylene film or EVA film.

6. The multi-layer composite process for needle-free ultrasonic composite geotextile according to claim 1, characterized in that: In step (2), when geomembrane and geogrid are used as functional intermediate layers at the same time, the geogrid is first attached to the surface of the geotextile base layer, and then the geomembrane is covered on the outside of the geogrid to form a multi-layer structure of "base layer + geogrid + membrane".

7. The multi-layer composite process for needle-free ultrasonic composite geotextile according to claim 1, characterized in that: In step (4), the welding trajectory arrangement of the ultrasonic welding head is one or more of the following: dot matrix arrangement, continuous line arrangement, and edge reinforcement arrangement.

8. The multi-layer composite process for needle-free ultrasonic composite geotextile according to claim 1, characterized in that: In step (4), the welding head end face of the ultrasonic welding head is provided with a textured structure, which is a grid pattern, annular pattern or radial pattern, and the texture depth is 0.05~0.3mm, which is used to increase the welding contact area and guide the flow of molten fibers.

9. The multi-layer composite process for needle-free ultrasonic composite geotextile according to claim 1, characterized in that: In step (5), the ultrasonic power of the secondary welding is increased by 10% to 30% compared with the primary welding in step (4).

10. The multi-layer composite process for needle-free ultrasonic composite geotextile according to claim 1, characterized in that: In step (6), the tension of the tension roller group is controlled at 50~500N / m, the temperature of the cooling roller is controlled at 5~25℃, the winding tension during winding is 30~300N / m, and the flatness deviation of the finished product after winding is ≤3mm / m.

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