Manufacturing method of PET plastic steel belt special for geogrid

Abstract

This invention belongs to the field of PET plastic steel strip production technology. A method for manufacturing PET plastic steel strips specifically for geogrids results in products with high initial modulus, high elongation load, and particularly superior 1% and 2% modulus values, with a very significant difference in stress-strain curves. It also exhibits low creep and good dimensional stability. Wide-width geogrids, exceeding 6 meters in width, can be successfully produced. It can generate extremely high tensile modulus under low strain conditions, and the synergistic effect of longitudinal and transverse ribs fully leverages the geogrid's interlocking function with the soil. The resulting geogrid has a wide temperature resistance range, from -70 to 180℃. Furthermore, it possesses excellent resistance to ultraviolet radiation and microbial corrosion, and good resistance to acid, alkali, salt solutions, and oils, meeting the requirements of permanent engineering construction. This is determined by the inherent characteristics of PET as the raw material for geosynthetic materials.

Description

Technical Field

[0001] This invention relates to the field of PET plastic steel strip production technology, and in particular to a method for manufacturing a PET plastic steel strip for geogrids. Background Technology

[0002] Geotechnical materials have become the fourth largest building material internationally, after steel, cement, and wood. Currently, the global annual demand for geogrids is approximately 25 billion square meters. Geogrids can be used in civil engineering projects such as highways, railways, embankments, bridge abutments, construction access roads, docks, revetments, flood control dikes, dams, tidal flat management, freight yards, slag yards, airports, sports fields, environmentally friendly buildings, soft soil foundation reinforcement, retaining wall reinforcement, and high slope treatment, as well as in exposed hydraulic engineering projects. They possess high strength, low creep, and adaptability to various soil environments, fully meeting the requirements for high retaining walls in high-grade highways. They effectively improve the interlocking and bonding of the reinforced bearing surface, greatly enhance the bearing capacity of the foundation, effectively restrain lateral displacement of the soil, and enhance the stability of the foundation.

[0003] Polyethylene terephthalate (PET) has the chemical formula -OCH2-CH2OCOC6H4CO-. It is a milky white or light yellow, highly crystalline polymer with a smooth, glossy surface. Compared to traditional geogrids, PET geogrids offer superior strength, load-bearing capacity, corrosion resistance, aging resistance, high friction coefficient, uniform mesh size, ease of construction, and long service life. They are particularly suitable for deep-sea operations and embankment reinforcement, fundamentally solving the technical problems of low strength, poor corrosion resistance, and short service life caused by long-term seawater erosion when using other materials for gabions. PET also effectively prevents construction damage caused by machinery crushing or breaking the gabions during construction.

[0004] Existing geogrids generally have the following defects:

[0005] 1. It has disadvantages such as low strength, high tensile strength at break, and high creep coefficient.

[0006] 2. It has a relatively narrow temperature resistance range and poor resistance to ultraviolet radiation and microbial corrosion.

[0007] 3. The friction coefficient between the geogrid and the soil is relatively small, making it easy for them to slide relative to each other.

[0008] 4. The width of biaxial tensile welded geogrid is relatively small, making it difficult to achieve efficient and economical reinforcement.

[0009] 5. It is susceptible to corrosion from acid, alkali, and salt solutions, or oils; it is also susceptible to water dissolution or microbial attack, and therefore cannot meet the requirements for permanent engineering construction.

[0010] 6. Currently, the existing PET geogrid strips in China generally do not meet the requirements. Taking 012008 PET geogrid strip as an example, the current 1% constant elongation load strength is generally less than 890N, the 2% constant elongation load strength is generally less than 1750N, the 5% constant elongation load strength is generally less than 2940N, and the total breaking strength is generally less than 3900N. Summary of the Invention

[0011] Traditional PET plastic-steel strips used in the geogrid industry generally suffer from shortcomings such as low initial modulus, high elongation at break, and low strength. This invention prepares a suitable modified material and, through the coordination and optimization of die design, raw material modification, test temperature and speed control, and the selection of cooling and shaping processes, provides a high-quality PET plastic-steel strip specifically for geogrids.

[0012] This invention proposes a method for manufacturing a PET plastic-steel strip specifically for geogrids, comprising the following steps:

[0013] Step a: Physically and chemically modify the PET raw material by pre-crystallizing it at 160-180℃ for 0.3-0.6 hours to achieve a crystallinity of 25-35%. This increases the softening temperature of the material and prevents sticking during production. Simultaneously, it effectively reduces the moisture content of the raw material, keeping it below 1000 PPM, and reduces residual dust, keeping it below 0.03%.

[0014] Step b: Increase the relative molecular weight of the crystallized raw material to raise the target viscosity to 0.82-0.95 dl / g; during this process, in order to promote the polycondensation reaction to proceed more favorably in the positive direction, small molecules such as water, alcohol, and ether generated during the polycondensation process are continuously absorbed and processed;

[0015] Step c: After the required raw materials are prepared, they enter the main screw of the plastic steel belt production line. The screw temperature is set with a low front and high back design to improve melt uniformity while minimizing viscosity. The heating temperature at the front end of the screw is controlled between 280-300℃, and the temperature at the rear end is controlled between 258-275℃. The viscosity drop is controlled to be ≤0.09dl / g.

[0016] Step d: Control the die head heating temperature between 255-265℃, the die opening width between 3.0-5.3 times the bandwidth, the die opening thickness between 0.9-2.1mm during processing, the cavity structure is teardrop-shaped, the discharge pressure is designed to be within a reasonable range of 4-6Mpa, the melt flow channel length is controlled between 0.5-1.2 meters, and the melt filtration accuracy is controlled between 15-25um;

[0017] Step e: Control the temperature of the preform before it enters the preheating oven at 20-30℃, control the total stretch ratio at 5.2-6.7 times, the production speed at 190-250m / min, the temperature of the setting oven at 50-90℃, control the relaxation overfeed at 95-105%, control the setting tension at above 26000N, and adopt the embossing process in the production process with an embossing ratio of 105-125%.

[0018] Step f: Product quality control. Product strength is controlled above 420 MPa, width is within the range of M1 ± 0.6 mm, thickness is within the range of M2 ± 0.06 mm, deviation is ≤ 60 mm / 2000 mm, elongation at break is within the range of 5-7%, peel force is required to be ≥ 200 N; 1% elongation is ≥ 1025 N, 2% elongation is ≥ 1845 N, 5% elongation is ≥ 3280 N, and tensile strength is ≥ 4350 N.

[0019] Preferably, the reaction temperature for solid-phase thickening in step b is controlled between 200-235°C, and the reaction residence time is controlled at 24 hours.

[0020] Preferably, in step f, M1 is in the range of 9-32mm and M2 is in the range of 0.6-1.5mm.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. The product has a high initial modulus and a large load at a given elongation. In particular, the 1% and 2% values ​​are very superior, and the stress-strain curve comparison effect is very obvious.

[0023] 2. Low creep and good dimensional stability, enabling smooth production of wide-width grids, with widths reaching over 6 meters;

[0024] 3. It can generate extremely high tensile modulus under low strain capacity. The longitudinal and transverse ribs work together to fully utilize the interlocking effect of the grid on the soil.

[0025] 4. The geogrid produced has a wide temperature resistance range, reaching -70 to 180℃. It also exhibits excellent resistance to ultraviolet radiation and microbial corrosion, as well as good resistance to acid, alkali, salt solutions, and oils, meeting the requirements of permanent engineering construction. This is determined by the inherent characteristics of PET as the raw material for geotextiles.

[0026] 5. By treating the polyester surface during the production process, a rough pattern is pressed on, which enhances the roughness of the geogrid surface and increases the friction coefficient between the geogrid and the soil. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0028] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicating the orientation or positional relationship are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0029] A method for manufacturing a PET plastic-steel strip for geogrids includes the following steps:

[0030] First, the PET raw material undergoes physical and chemical modification. It is pre-crystallized at 160-180℃ for 0.3-0.6 hours to achieve a crystallinity of 25-35%, thereby increasing the softening temperature of the material and preventing adhesion during the production process. At the same time, it can effectively reduce the moisture content of the raw material, which can be controlled below 1000 PPM; and reduce the residual dust content, which can be controlled below 0.03%.

[0031] Secondly, the relative molecular weight of the crystallized raw material is increased to raise the target viscosity to 0.82-0.95 dl / g. During this process, in order to promote the polycondensation reaction to proceed more favorably in the positive direction, small molecules such as water, alcohol, and ether generated during the polycondensation process are continuously absorbed and processed. During this process, the reaction temperature for solid-phase thickening is controlled between 200-235℃, and the reaction residence time is controlled at 24 hours.

[0032] Next, after preparing the required raw materials, the main screw is produced using a plastic steel belt. The screw temperature is set with a lower temperature at the front and a higher temperature at the back to improve melt uniformity while minimizing viscosity. The heating temperature at the front end of the screw is controlled between 280-300℃, and the temperature at the rear end is controlled between 258-275℃, with a viscosity reduction of ≤0.09dl / g. The die head heating temperature is controlled between 255-265℃, the die width is controlled between 3.0-5.3 times the bandwidth, the die thickness is processed within the range of 0.9-2.1mm, the cavity structure is teardrop-shaped, the discharge pressure is designed within the reasonable range of 4-6Mpa, the melt flow channel length is controlled between 0.5-1.2m, and the melt filtration accuracy is controlled between 15-25um.

[0033] Next, control the temperature of the blank before it enters the preheating oven at 20-30℃, control the total stretch ratio at 5.2-6.7 times, the production speed at 190-250m / min, the temperature of the setting oven at 50-90℃, control the relaxation overfeed at 95-105%, control the setting tension at above 26000N, and use the embossing process in the production process with an embossing ratio of 105-125%.

[0034] The most crucial aspect is product quality control. Product strength must be above 420 MPa, width within ±0.6 mm, thickness within ±0.06 mm, deviation ≤60 mm / 2000 mm, elongation at break within 5-7%, peel force ≥200 N; 1% elongation ≥1025 N, 2% elongation ≥1845 N, 5% elongation ≥3280 N, and tensile strength ≥4350 N.

[0035] The PET geogrid special plastic steel strip produced by the above preparation method can completely replace imported products, fill the domestic gap, has high added value, large market demand, and good economic and social efficiency.

[0036] The above description is only 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 method for manufacturing a PET plastic-steel strip specifically for geogrids, comprising, Includes the following steps: Step a: Physically and chemically modify the PET raw material by pre-crystallizing it at 160-180℃ for 0.3-0.6 hours to achieve a crystallinity of 25-35%. This increases the softening temperature of the material and prevents sticking during production. Simultaneously, it effectively reduces the moisture content of the raw material, keeping it below 1000 PPM, and reduces residual dust, keeping it below 0.03%. Step b: Increase the relative molecular weight of the crystallized raw material to raise the target viscosity to 0.82-0.95 dl / g; during this process, in order to promote the polycondensation reaction to proceed more favorably in the positive direction, small molecules such as water, alcohol, and ether generated during the polycondensation process are continuously absorbed and processed; Step c: After the required raw materials are prepared, they enter the main screw of the plastic steel belt production line. The screw temperature is set with a low front and high back design to improve melt uniformity while minimizing viscosity. The heating temperature at the front end of the screw is controlled between 280-300℃, and the temperature at the rear end is controlled between 258-275℃. The viscosity drop is controlled to be ≤0.09dl / g. Step d: Control the die head heating temperature between 255-265℃, the die opening width between 3.0-5.3 times the bandwidth, the die opening thickness between 0.9-2.1mm during processing, the cavity structure is teardrop-shaped, the discharge pressure is designed to be within a reasonable range of 4-6Mpa, the melt flow channel length is controlled between 0.5-1.2 meters, and the melt filtration accuracy is controlled between 15-25um; Step e: Control the temperature of the preform before it enters the preheating oven at 20-30℃, control the total stretch ratio at 5.2-6.7 times, the production speed at 190-250m / min, the temperature of the setting oven at 50-90℃, control the relaxation overfeed at 95-105%, control the setting tension at above 26000N, and adopt the embossing process in the production process with an embossing ratio of 105-125%. Step f: Product quality control. Product strength is controlled above 420 MPa, width is within the range of M1 ± 0.6 mm, thickness is within the range of M2 ± 0.06 mm, deviation is ≤ 60 mm / 2000 mm, elongation at break is within the range of 5-7%, peel force is required to be ≥ 200 N; 1% elongation is ≥ 1025 N, 2% elongation is ≥ 1845 N, 5% elongation is ≥ 3280 N, and tensile strength is ≥ 4350 N.

2. The method for manufacturing a PET plastic-steel strip for geogrids according to claim 1, characterized in that, In step b, the reaction temperature for solid-phase thickening is controlled between 200-235℃, and the reaction residence time is controlled at 24 hours.

3. The method for manufacturing a PET plastic-steel strip for geogrids according to claim 1, characterized in that, In step f, M1 is in the range of 9-32mm, and M2 is in the range of 0.6-1.5mm.