Enhanced polypropylene spiral fiber as well as preparation method and application thereof

Abstract

The invention relates to the technical field of building materials, and discloses a reinforced polypropylene spiral fiber which is of a continuous spiral structure and is made of a modified polypropylene material. The diameter of the fiber ranges from 0.2 mm to 0.4 mm, the length of the fiber ranges from 15 mm to 40 mm, the spiral pitch of the fiber ranges from 3 mm to 8 mm, and the number of spiral turns of a single fiber ranges from 2 to 5. According to the reinforced polypropylene spiral fiber and the preparation method and application thereof, the spiral structure greatly increases the contact area and bond stress of the fiber and concrete, the dispersity of the fiber in the concrete is remarkably improved, the reduction rate of the anti-cracking area of the concrete is larger than or equal to 60%, the 28-day breaking strength is larger than or equal to 8.0 MPa, shrinkage cracks and temperature cracks of the concrete in a water environment are effectively inhibited, and the service life of the concrete is prolonged. And the structural toughness and the bearing capacity are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to an enhanced polypropylene spiral fiber, its preparation method, and its application. Background Technology

[0002] In concrete structures that are in long-term contact with water, such as swimming pools, fountains, or landscape ponds, traditional reinforced concrete has significant drawbacks:

[0003] Steel reinforcement corrosion problem: Chloride ions and moisture in the water environment penetrate into the concrete, causing the internal steel reinforcement to corrode and expand, leading to concrete cracking and spalling, and severely shortening the structural life.

[0004] Insufficient crack resistance of concrete: In a water environment, concrete shrinkage and temperature stress can easily cause cracks, which in turn aggravate water penetration and steel corrosion, forming a vicious cycle.

[0005] To address the above problems, existing technologies have attempted to use fiber-reinforced concrete, but limitations remain:

[0006] Steel fibers: Although they can improve crack resistance, they are prone to corrosion, increase the structural weight, and their bond strength with concrete decreases over time.

[0007] Ordinary polypropylene straight fiber: low density and corrosion resistant, but due to its linear structure, it has poor dispersion and insufficient bond strength in concrete, making it difficult to effectively inhibit crack propagation.

[0008] Therefore, there is an urgent need for a fiber material that is corrosion-resistant, has good dispersibility, and strong bond strength to meet the long-term performance requirements of concrete in water environments such as swimming pools and fountains. Summary of the Invention

[0009] (a) Technical problems to be solved

[0010] To address the shortcomings of existing technologies, this invention provides an enhanced polypropylene spiral fiber, its preparation method, and its application, which can solve the aforementioned problems.

[0011] (II) Technical Solution

[0012] To achieve the above objectives, the present invention provides the following technical solution: a reinforced polypropylene spiral fiber, wherein the fiber has a continuous spiral structure and is made of modified polypropylene material;

[0013] The fiber has a diameter of 0.2–0.4 mm, a length of 15–40 mm, a helical pitch of 3–8 mm, and a single fiber has 2–5 helical turns.

[0014] Preferably, the modified polypropylene material comprises an anti-ultraviolet agent, an antioxidant, a phosphite antioxidant, and polypropylene.

[0015] The UV stabilizer is a benzotriazole UV stabilizer, UV-531 or UV-327, added at a rate of 0.8-1.5% of the mass of polypropylene.

[0016] The antioxidant is a compound system of hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a total addition amount of 0.5 to 0.8% of the mass of polypropylene, and the mass ratio of 1010 to 168 is 2:1.

[0017] Preferably, the fiber has a breaking strength ≥500MPa, an elastic modulus ≥3.5GPa, and a strength retention rate ≥90% after soaking in hot water at 80℃ for 72h.

[0018] The method for preparing the reinforced polypropylene spiral fiber as described above is characterized by comprising the following steps:

[0019] S1. Raw material pretreatment: Dry the polypropylene resin at 80-100℃ for 3-5 hours;

[0020] S2. Raw material mixing: The dried polypropylene resin is mixed with UV stabilizer and antioxidant in proportion, and then mixed in a high-speed mixer at a speed of 800-1200 r / min for 10-15 min to obtain a uniform mixture;

[0021] S3. Melt extrusion: The mixture is fed into a twin-screw extruder with a screw length-to-diameter ratio of 30:1 to 40:1. The temperatures of each zone of the extruder are 180℃, 200℃, 220℃, 230℃, and 220℃ respectively. The extrusion rate is 20 to 30 kg / h to obtain continuous polypropylene filaments.

[0022] S4. Spiral forming: Polypropylene filaments are introduced into a spiral forming mold. The filaments are formed into a continuous spiral shape by the differential rotation of the traction roller and the mold. The linear speed of the traction roller is 1.2 to 1.5 times that of the mold.

[0023] S5. Shaping and cutting: After the spiral fiber is shaped by air cooling, it is cut into reinforced polypropylene spiral fibers of the length described in claim 1 by a cutting device.

[0024] Preferably, the spiral forming mold in step S4 is made of chrome-plated alloy steel with a surface roughness Ra≤0.8μm.

[0025] Preferably, the blade rotation speed of the cutting device in step S5 is 1500-2000 r / min, and the cutting error is ≤ ±0.5 mm.

[0026] The application of the reinforced polypropylene spiral fiber described above in ready-mixed concrete, which is used to construct indoor constant temperature swimming tubs, outdoor open-air fountain tubs or landscape pools.

[0027] The fiber content in commercial concrete is 1.0–1.8 kg / m³.

[0028] Preferably, the concrete design strength grade of the indoor constant temperature swimming bath is C30 to C40, and the impermeability grade is ≥P10; the concrete design strength grade of the outdoor open-air water spray bath is C35 to C45, and the frost resistance grade is ≥F200.

[0029] Preferably, the mix proportions of the commercial concrete are as follows: 350-420 kg / m³ of P.O42.5 grade cement, 1050-1150 kg / m³ of continuously graded crushed stone (5-20 mm), 650-750 kg / m³ of medium sand (fineness modulus 2.6-3.0), 160-180 kg / m³ of tap water, 1.0-1.8% of the cement mass of polycarboxylate high-performance water-reducing agent (solid content 20%), and 1.0-1.8 kg / m³ of reinforced polypropylene spiral fiber.

[0030] Preferably, the ready-mixed concrete has a 28-day flexural strength ≥8.0MPa, an early crack area reduction rate ≥60%, and a chloride ion diffusion coefficient that decreases by ≥50% after soaking in a 5% NaCl solution for 180 days.

[0031] (III) Beneficial Effects

[0032] Compared with the prior art, the present invention provides a reinforced polypropylene spiral fiber, its preparation method and application, which has the following beneficial effects:

[0033] 1. The reinforced polypropylene spiral fiber, its preparation method and application: The spiral structure significantly increases the contact area and bond strength between the fiber and concrete, significantly improves the fiber dispersion in concrete, reduces the crack-resistant area of ​​concrete by ≥60%, and achieves a 28-day flexural strength of ≥8.0MPa. It effectively inhibits drying shrinkage cracks and temperature cracks in concrete under water conditions, and significantly improves the structural toughness and load-bearing capacity.

[0034] 2. This reinforced polypropylene spiral fiber, its preparation method, and its application. The polypropylene material is water-resistant and chemically resistant. With the modification design of anti-ultraviolet agents and antioxidants, after soaking in 5% NaCl solution for 180 days, the chloride ion diffusion coefficient of concrete is reduced by ≥50%, which completely solves the corrosion problem of traditional reinforced concrete and extends the service life of water environment structures such as swimming pools and fountains by more than 50%.

[0035] 3. The reinforced polypropylene spiral fiber, its preparation method, and its application have a fiber density much lower than that of steel, do not increase the self-weight of concrete, and are easy to transport and construct. The preparation process is simple and easy to industrialize and mass-produce. When applied, the dosage is only 1.0 to 1.8 kg / m³, and the overall cost is lower than that of traditional steel fiber reinforcement schemes. At the same time, it reduces the maintenance costs caused by cracking and corrosion in the later stage, and has significant economic and social benefits. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] A reinforced polypropylene spiral fiber, wherein the fiber has a continuous spiral structure and is made of modified polypropylene material;

[0038] The fiber diameter is 0.2–0.4 mm, the length is 15–40 mm, the helical pitch is 3–8 mm, and the number of helical turns of a single fiber is 2–5.

[0039] Modified polypropylene materials consist of UV stabilizers, antioxidants, phosphite antioxidants, and polypropylene.

[0040] The UV stabilizer is a benzotriazole UV stabilizer, UV-531 or UV-327, added at a rate of 0.8-1.5% of the mass of polypropylene.

[0041] The antioxidant is a compound system of hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a total addition amount of 0.5 to 0.8% of the mass of polypropylene, and the mass ratio of 1010 to 168 is 2:1.

[0042] The fiber has a tensile strength ≥500MPa, an elastic modulus ≥3.5GPa, and a strength retention rate ≥90% after soaking in hot water at 80℃ for 72h.

[0043] A method for preparing reinforced polypropylene spiral fibers includes the following steps:

[0044] S1: Raw material pretreatment: Dry the polypropylene resin at 80-100℃ for 3-5 hours to remove moisture;

[0045] S2: Raw material mixing: The dried polypropylene resin is mixed with UV stabilizer and antioxidant in proportion, and then mixed in a high-speed mixer at a speed of 800-1200 r / min for 10-15 min to obtain a uniform mixture.

[0046] S3: Melt extrusion: The mixture is fed into a twin-screw extruder (screw length-to-diameter ratio 30:1 to 40:1), the temperatures of each zone of the extruder are 180℃, 200℃, 220℃, 230℃ and 220℃ respectively, and the extrusion rate is 20 to 30 kg / h to obtain continuous polypropylene filaments.

[0047] S4: Spiral forming: Polypropylene filaments are introduced into a chrome-plated alloy steel spiral forming die (surface roughness Ra≤0.8μm). By the differential rotation of the traction roller and the die (the linear speed of the traction roller is 1.2 to 1.5 times the linear speed of the die), the filaments are formed into a continuous spiral shape.

[0048] S5: Shaping and Cutting: After being air-cooled and shaped, the spiral fiber filaments are cut into reinforced polypropylene spiral fibers with a length of 15-40 mm by a blade cutting device with a rotation speed of 1500-2000 r / min, with a cutting error of ≤±0.5 mm.

[0049] An application of reinforced polypropylene spiral fiber in ready-mixed concrete, which is used to construct indoor constant temperature swimming tubs, outdoor open-air fountain tubs, or landscape pools.

[0050] Dosage and mix proportion:

[0051] Fiber content: 1.0~1.8kg / m³ (can be adjusted according to structural strength and crack resistance requirements);

[0052] Concrete mix proportions (taking C35 to C45 as an example): P.O4 2.5 grade cement 350 to 420 kg / m³, medium sand (fineness modulus 2.6 to 3.0) 650 to 750 kg / m³, continuously graded crushed stone (5 to 20 mm) 1050 to 1150 kg / m³, tap water 160 to 180 kg / m³, polycarboxylate superplasticizer (solid content 20%) is 1.0 to 1.8% of cement mass, and reinforced polypropylene spiral fiber 1.0 to 1.8 kg / m³;

[0053] Performance advantages:

[0054] Crack resistance: Early crack area reduction rate ≥60%, effectively inhibiting concrete drying shrinkage and temperature cracks in a water environment;

[0055] Durability: Water-resistant and chemically resistant; after immersion in 5% NaCl solution for 180 days, the chloride ion diffusion coefficient decreases by ≥50%.

[0056] Mechanical properties: 28-day flexural strength ≥8.0MPa, with significantly improved toughness, capable of withstanding loads such as water flow impact and human activity.

[0057] Example 1: Application of Indoor Heated Swimming Bath:

[0058] Fiber parameters: diameter 0.25mm, length 20mm, helical pitch 4mm, number of helical turns 3; modified polypropylene contains 1.0% UV-531, 0.3% 1010, and 0.2% 168;

[0059] Preparation steps:

[0060] S1. Raw material pretreatment: Polypropylene resin is dried at 90℃ for 4 hours;

[0061] S2. Raw material mixing: Mix polypropylene, UV-531, 1010, and 168 at a mass ratio of 98.5:1.0:0.3:0.2 and stir at 1000 r / min for 12 min using a high-speed mixer;

[0062] S3. Melt extrusion: The temperature of each zone of the twin-screw extruder is 180℃, 200℃, 220℃, 230℃, and 220℃, and the extrusion rate is 25kg / h to obtain polypropylene filaments.

[0063] S4, Spiral Forming: A spiral filament is formed by using a chrome-plated die with a pitch of 4mm and a speed difference ratio of 1.3 between the traction roller and the die.

[0064] S5. Shaping and cutting: After air cooling and shaping, the fibers are cut into 20mm long fibers with a blade at 1800r / min.

[0065] Concrete mix proportion: C35 concrete, cement 380kg / m³, sand 700kg / m³, crushed stone 1100kg / m³, water 170kg / m³, polycarboxylate superplasticizer 1.2%, fiber content 1.2kg / m³;

[0066] Performance testing: 28-day flexural strength 8.5 MPa, impermeability grade P12, early crack area reduction rate 65%.

[0067] Example 2: Application of outdoor open-air water bath:

[0068] Fiber parameters: diameter 0.35mm, length 30mm, helical pitch 6mm, number of helical turns 4; modified polypropylene contains 1.5% UV-327, 0.4% 1010, and 0.2% 168;

[0069] Preparation steps:

[0070] S1. Raw material pretreatment: Polypropylene resin is dried at 100℃ for 3 hours;

[0071] S2. Raw material mixing: Polypropylene, UV-327, 1010, and 168 are mixed in a mass ratio of 97.9:1.5:0.4:0.2 and stirred in a high-speed mixer at 1200 rpm for 10 minutes.

[0072] S3. Melt extrusion: The temperature of each zone of the twin-screw extruder is 185℃, 205℃, 225℃, 235℃, and 225℃, and the extrusion rate is 30kg / h to obtain polypropylene filaments;

[0073] S4, Spiral Forming: A spiral filament is formed by using a chrome-plated die with a pitch of 6mm and a speed difference ratio of 1.4 between the traction roller and the die.

[0074] S5. Shaping and cutting: After air cooling and shaping, the fibers are cut into 30mm long fibers with a 2000r / min blade.

[0075] Concrete mix proportion: C40 concrete, cement 400kg / m³, sand 650kg / m³, crushed stone 1150kg / m³, water 180kg / m³, polycarboxylate superplasticizer 1.5%, fiber content 1.5kg / m³;

[0076] Performance testing: 28-day flexural strength 9.2 MPa, freeze resistance grade F200, chloride ion diffusion coefficient decreased by 55% after soaking in 5% NaCl solution for 180 days.

[0077] 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.

Claims

1. A reinforced polypropylene spiral fiber, characterized in that, The fiber has a continuous helical structure and is made of modified polypropylene material; The fiber has a diameter of 0.2–0.4 mm, a length of 15–40 mm, a helical pitch of 3–8 mm, and a single fiber has 2–5 helical turns.

2. The reinforced polypropylene spiral fiber according to claim 1, characterized in that, The modified polypropylene material comprises UV stabilizers, antioxidants, phosphite antioxidants, and polypropylene. The UV stabilizer is a benzotriazole UV stabilizer, UV-531 or UV-327, added at a rate of 0.8-1.5% of the mass of polypropylene. The antioxidant is a compound system of hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a total addition amount of 0.5 to 0.8% of the mass of polypropylene, and the mass ratio of 1010 to 168 is 2:

1.

3. The reinforced polypropylene spiral fiber according to claim 1, characterized in that, The fiber has a tensile strength ≥500MPa, an elastic modulus ≥3.5GPa, and a strength retention rate ≥90% after soaking in hot water at 80℃ for 72h.

4. A method for preparing reinforced polypropylene spiral fibers as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Raw material pretreatment: Dry the polypropylene resin at 80-100℃ for 3-5 hours; S2. Raw material mixing: The dried polypropylene resin is mixed with UV stabilizer and antioxidant in proportion, and then mixed in a high-speed mixer at a speed of 800-1200 r / min for 10-15 min to obtain a uniform mixture; S3. Melt extrusion: The mixture is fed into a twin-screw extruder with a screw length-to-diameter ratio of 30:1 to 40:

1. The temperatures of each zone of the extruder are 180℃, 200℃, 220℃, 230℃, and 220℃ respectively. The extrusion rate is 20 to 30 kg / h to obtain continuous polypropylene filaments. S4. Spiral forming: Polypropylene filaments are introduced into a spiral forming mold. The filaments are formed into a continuous spiral shape by the differential rotation of the traction roller and the mold. The linear speed of the traction roller is 1.2 to 1.5 times that of the mold. S5. Shaping and cutting: After the spiral fiber is shaped by air cooling, it is cut into reinforced polypropylene spiral fibers of the length described in claim 1 by a cutting device.

5. The method for preparing reinforced polypropylene spiral fibers according to claim 4, characterized in that, The spiral forming mold mentioned in step S4 is made of chrome-plated alloy steel with a surface roughness Ra≤0.8μm.

6. The method for preparing reinforced polypropylene spiral fibers according to claim 4, characterized in that, The blade rotation speed of the cutting device in step S5 is 1500-2000 r / min, and the cutting error is ≤ ±0.5 mm.

7. The application of the reinforced polypropylene spiral fiber as described in any one of claims 1-3 in ready-mixed concrete, characterized in that, The commercial concrete is used to construct indoor constant temperature swimming tubs, outdoor open-air fountain tubs, or landscape pools. The fiber content in commercial concrete is 1.0–1.8 kg / m³.

8. The application according to claim 7, characterized in that, The indoor constant temperature swimming tub has a concrete design strength grade of C30 to C40 and a permeability grade of ≥P10; the outdoor open-air water spray tub has a concrete design strength grade of C35 to C45 and a frost resistance grade of ≥F200.

9. The application according to claim 7 or 8, characterized in that, The mix proportions of the commercial concrete are as follows: 350-420 kg / m³ of P.O42.5 grade cement, 1050-1150 kg / m³ of continuously graded crushed stone (5-20 mm), 650-750 kg / m³ of medium sand (fineness modulus 2.6-3.0), 160-180 kg / m³ of tap water, 1.0-1.8% of the cement mass of polycarboxylate high-performance water-reducing agent (solid content 20%), and 1.0-1.8 kg / m³ of reinforced polypropylene spiral fiber.

10. The application according to claim 9, characterized in that, The commercial concrete has a 28-day flexural strength ≥8.0MPa, an early crack area reduction rate ≥60%, and after soaking in 5% NaCl solution for 180 days, the chloride ion diffusion coefficient of the concrete decreases by ≥50%.