Modification method and application of thermoplastic elastomer particles for polyurethane runway

Abstract

The invention discloses a modification method of thermoplastic elastomer particles for a polyurethane runway. The modification method comprises the following operation steps: S1, preparing the thermoplastic elastomer particles with proper particle sizes; s2, maleic anhydride pretreatment: maleic anhydride is subjected to drying treatment, so that the water content of maleic anhydride is smaller than or equal to 0.1 wt%; s3, premixing: uniformly mixing the thermoplastic elastomer particles, maleic anhydride and bis (tert-butylperoxy) dicumyl peroxide according to a certain proportion to prepare a mixture; s4, reactive extrusion: adding the mixture into a twin-screw extruder with L / D greater than or equal to 40 for gradient grafting, and outputting a kneaded block from a discharge end of the twin-screw extruder; s5, granulation and post-treatment: the kneaded blocks are cut into particles underwater, and the cut particles are subjected to passivation treatment; the invention also provides a polyurethane composite material runway. According to the modification method disclosed by the invention, the interface bonding strength of the TPE and the polyurethane material can be remarkably improved through the surface gradient grafting modification of the TPE particles by the maleic anhydride (MAH).

Description

Technical Field

[0001] The present invention relates to the technical field of surface modification of polymer materials, in particular to a modification method of thermoplastic elastomer particles for polyurethane runways and applications thereof. Background Art

[0002] The interfacial peel strength between conventional thermoplastic elastomer (TPE) particles (e.g., SEBS-based) and the polyurethane matrix is less than 2.5 N / mm (ASTM D903 standard). Particles will detach after 6-12 months of use in a hot and humid environment (temperature ≥40°C, humidity ≥80%). While several interfacial modification methods, such as silane coupling agent treatment, have been developed, these technologies suffer from the following drawbacks: 1. The modified layer suffers from poor water resistance, with silane bonds easily hydrolyzing and a ≥40% decrease in bond strength after 500 hours of hot and humid aging; 2. The process is complex, requiring a multi-step impregnation-drying process and increasing energy consumption by 30%-50%. Therefore, there is an urgent need for a simple, weather-resistant method for modifying the polarity of thermoplastic elastomer surfaces to overcome the conflict between interfacial bonding strength and processing stability. Summary of the Invention

[0003] To solve the above technical problems, the present invention provides a method for modifying thermoplastic elastomer particles for polyurethane runways and its application. It can significantly improve the interfacial bonding strength between TPE and polyurethane materials by gradient grafting maleic anhydride (MAH) on the surface of thermoplastic elastomer (TPE) particles.

[0004] The technical solutions provided by the present invention are as follows: A method for modifying thermoplastic elastomer particles for polyurethane runways comprises the following steps: S1. Prepare thermoplastic elastomer particles with a particle size of 2 to 5 mm; S2. Maleic anhydride pretreatment: drying the maleic anhydride to make its moisture content ≤0.1wt%; S3, premixing: mixing thermoplastic elastomer particles, maleic anhydride, and di-tert-butyl dicumyl peroxide in a certain ratio to obtain a mixture; S4, reactive extrusion: the mixed material is added to a twin-screw extruder with an L / D of ≥40 for gradient grafting, including i) a melt mixing section at 160-165°C, ii) a reaction section at 170-175°C, and iii) a homogenization section at 168-172°C. The decomposition rate of maleic anhydride is controlled to be ≤3%, the surface grafting depth is 10-50 μm, and a kneading block is output from the discharge end of the twin-screw extruder; S5. Granulation and post-processing: The kneaded block is pelletized underwater, and the pellets are passivated.

[0005] Preferably, the thermoplastic elastomer particles in step S1 include the following components in parts by mass: Styrene-ethylene-butylene-styrene block copolymer 100-190 phr, Polypropylene (PP, melt index 5g / 10min~20g / 10min) 20~40 phr, White oil 90~130 phr, Modified light calcium carbonate 150~300 phr, Iron oxide red 0~30 phr, Antioxidant 2.5~4.5 phr, UV absorber 1.5~3 phr, Nano-silicon dioxide 50-200phr.

[0006] Preferably, the mixing process in step S3 is carried out in an inert gas protection atmosphere, and the humidity in the mixing environment is ≤30%RH.

[0007] Preferably, in step S3, thermoplastic elastomer particles (TPE), maleic anhydride (MAH), and di-tert-butyl dicumyl peroxide (BIPB) are mixed in a weight ratio of 100:2-2.5:0.5-0.6.

[0008] Preferably, the correlation equation between the screw speed and residence time of the twin-screw extruder in step S4 is t=0.015L / D·n⁻¹, where t is the residence time / min and n is the speed / rpm.

[0009] Preferably, the screw assembly in the melt mixing section of step S4 contains at least two forward conveying elements. The core function of these forward conveying elements (such as single- or double-threaded elements) is to directional transport the material, ensuring axial flow along the extruder. The presence of at least two forward conveying elements serves the following purposes: 1. Segmented flow control: This creates a pressure gradient between the melting section (160-165°C) and the reaction section (170-175°C) to prevent melt backflow; and 2. Stabilizes the residence time: This, in conjunction with the rotational speed formula (t = 0.015 × (L / D) × n⁻¹), ensures a controllable maleic anhydride grafting reaction time of 90-120 seconds. The provision of at least two forward conveying elements has the following advantages: 1. Preventing material retention: Avoiding the accumulation of unreacted materials and reducing the generation of impurities (such as maleic anhydride decomposition gas); 2. Improving process stability: Experiments have shown that insufficient forward elements will lead to a decrease in grafting depth; 3. Enhancing mixing uniformity: Cooperating with the kneading block to achieve efficient dispersion in the melt section (such as improving the compatibility of SEBS and PP).

[0010] Preferably, the reaction section in step S4 contains at least three sets of kneading blocks arranged in a 30° / 60° staggered pattern, with a residence time of 90 to 120 seconds. In practice, this can be expanded to 3 to 5 sets depending on screw length and reaction requirements. For example, a short screw (L / D = 40): 3 sets; a long screw (L / D ≥ 60): 4 to 5 sets. The 30° / 60° staggered arrangement involves alternating helical angles of 30° and 60°, respectively (e.g., 30° → 60° → 30°). The 30° kneading blocks provide high shear forces, promoting material melting and dispersion; the 60° kneading blocks reduce shear forces, extend residence time, and promote grafting reactions. The purpose of the 30° / 60° staggered arrangement is to optimize reaction efficiency by combining kneading blocks at different angles to achieve staged melting, mixing, and reaction. The 30° / 60° staggered arrangement can reduce heat accumulation, prevent premature decomposition of maleic anhydride (decomposition rate ≤ 3%), improve grafting uniformity (surface grafting rate ≥ 60%), reduce side reactions (such as thermal degradation), and retain matrix toughness (elongation at break ≥ 400%).

[0011] Preferably, the vacuum degree in the homogenization section of step S4 is ≤-0.08 MPa to remove by-products (maleic anhydride decomposition gas).

[0012] Preferably, the water temperature in step S5 is 20-30° C., and the particle size of the cut particles is 2-4 mm. The passivation treatment specifically comprises: hot air drying at 70-90° C. for 0.5-2 h or ultraviolet irradiation treatment to eliminate residual anhydride activity.

[0013] A polyurethane composite material runway, the materials used for which include thermoplastic elastomer particles prepared by the above-mentioned modification method of thermoplastic elastomer particles for polyurethane runways and polyurethane.

[0014] The present invention has the following advantages over the prior art: The present invention achieves maleic anhydride grafting only at a depth of 10 to 50 μm on the surface of thermoplastic elastomer particles (XPS depth profiling data) by matching the half-life of a di-tert-butyl peroxide initiator (BIPB) with the temperature zone of a twin-screw extruder. The grafting rate on the surface is ≥60% (FTIR quantitative analysis), while the grafting rate inside the matrix is ≤5%. The bulk toughness of the thermoplastic elastomer particles is retained (elongation at break ≥400%), and the interfacial bonding strength between TPE and polyurethane materials can be significantly improved.

[0015] This invention utilizes a kneading block angle design to balance grafting efficiency and material properties through gradient shear and staged reaction. Furthermore, by rationally configuring the number of forward conveying elements, material flow stability is ensured, enabling precise control of process parameters (temperature, rotational speed, and vacuum level). By specifically improving each step of the modification method, this invention effectively addresses the issues of low interfacial bonding strength and poor weather resistance found in existing conventional processes. DETAILED DESCRIPTION

[0016] To help those skilled in the art better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0017] Example 1: S1. Raw material preparation: Thermoplastic elastomer particles are prepared, the composition of which is as follows by mass: Styrene-ethylene-butylene-styrene block copolymer (SEBS) 100 phr, Polypropylene (PP, melt index 10 g / 10 min) 35 phr, White oil 100 phr, Modified light calcium carbonate 250 phr, Iron oxide red 20 phr, Antioxidant 3 phr, UV absorber 2 phr, Nanosilicon dioxide 50phr; S2. Maleic anhydride pretreatment: The maleic anhydride was dried to a moisture content of ≤ 0.1 wt%; S3. Premix: Under inert gas protection (humidity ≤ 30% RH), mix the raw materials in the following proportions: Thermoplastic elastomer granules 100 kg, Maleic anhydride (MAH) 2.5 kg, Diisopropylbenzene ditert-butylperoxide (BIPB) 0.6 kg; S4, reactive extrusion: The mixture was added to a twin-screw extruder with L / D=40 and the grafting reaction was carried out according to the following temperature gradient: Zone 1: 160°C (melting and mixing section, including two forward conveying elements), Zone 2: 170°C (initiator activation zone), Zone 3: 175°C (grafting reaction section, containing three sets of 30° / 60° staggered kneading blocks, residence time 100 s), Zone 4: 170°C (homogenization section, vacuum degree ≤ -0.08 MPa), The decomposition rate of maleic anhydride was controlled to be ≤ 3%, and the surface grafting depth was 10~50 μm; S5, granulation and post-processing: Underwater pelletizing (water temperature 25°C, particle size 3 mm); Passivation treatment: hot air drying at 80℃ for 1 h.

[0018] A polyurethane composite material runway, the materials used for which include thermoplastic elastomer particles prepared by adopting the modification method of thermoplastic elastomer particles for polyurethane runways and polyurethane.

[0019] Example 2: S1. Raw material preparation: The composition of the thermoplastic elastomer particles is calculated by mass: Styrene-ethylene-butylene-styrene block copolymer (SEBS) 100 phr, PP (melt index 20 g / 10 min) 40 phr, White oil 100 phr, Modified heavy calcium carbonate (silane coupling agent modified, particle size 5 μm) 300 phr, Iron oxide red 30 phr, Antioxidant (1010+168) 4.5 phr, UV absorber (UV-326) 3 phr, Nano-silicon dioxide 100phr; S2. Maleic anhydride pretreatment: Same as Example 1.

[0020] S3. Premix: Mixing ratio: Thermoplastic elastomer granules 100 kg, MAH 3.5 kg, BIPB 0.8 kg, Process conditions: nitrogen protection (dew point ≤ -40℃), humidity ≤ 30% RH; S4, reactive extrusion: Temperature zone setting: Zone 1: 165°C, Zone 2: 175°C, Zone 3: 180°C (including three sets of 45° / 90° kneading blocks, increased shear strength, residence time 120 s), Zone 4: 175°C (vacuum degree ≤ -0.08 MPa), Screw speed: 500 rpm; S5, granulation and post-processing: The pelletizing conditions are the same as in Example 1; Passivation treatment: 80℃ hot air drying for 1.5 h + UV irradiation (wavelength 254 nm, intensity 50 mW / cm², time 30 min).

[0021] A polyurethane composite material runway, the materials used for which include thermoplastic elastomer particles prepared by adopting the modification method of thermoplastic elastomer particles for polyurethane runways and polyurethane.

[0022] Example 3: S1. Raw material preparation: The composition of the thermoplastic elastomer particles is calculated by mass: Styrene-ethylene-butylene-styrene block copolymer (SEBS) 100 phr, PP (melt index 5 g / 10 min) 20 phr, White oil 100 phr, Modified light calcium carbonate (particle size 3 μm) 200 phr, Nanosilica (silane coated, particle size 20 nm) 150 phr, Antioxidant (1076) 2.5 phr; UV absorber (UV-326) 2.5 phr; S2. Maleic anhydride pretreatment: Same as Example 1; S3. Premix: Mixing ratio: Thermoplastic elastomer granules 100 kg, MAH 1.8 kg, BIPB 0.4 kg, Process conditions: vacuum premixing (pressure ≤ -0.095 MPa, time 30 min); S4, reactive extrusion: Temperature zone setting: Zone 1: 155°C (reverse conveying element to reduce shear degradation), Zone 2: 165°C, Zone 3: 170°C (including two sets of 60° kneading blocks), Zone 4: 165°C (vacuum degree ≤ -0.08 MPa), Screw speed: 400 rpm, residence time 90 s; S5, granulation and post-processing: The pelletizing conditions are the same as in Example 1; Passivation treatment: vacuum drying at 60°C (pressure ≤ -0.08 MPa, time 2 h).

[0023] A polyurethane composite material runway, the materials used for which include thermoplastic elastomer particles prepared by adopting the modification method of thermoplastic elastomer particles for polyurethane runways and polyurethane.

[0024] Table 1 below compares the performance of the polyurethane composite runways produced in Examples 1-3. Peel strength was measured according to ASTM D903, Standard Test Method for Peel Strength of Adhesives; yellowing index (ΔY / Y0) was measured according to GB / T 16422; and tensile strength and elongation at break were measured according to GB / T 10654-2001.

[0025] Table 1 Performance comparison of the polyurethane composite runway prepared in Examples 1-3

[0026] Table 1 shows that the polyurethane composite runway prepared in Example 2 exhibited the highest interfacial peel strength (4.5 N / mm), and both tensile strength (25 MPa) and elongation at break (450%) were superior to those of the other examples. This was primarily due to the high polypropylene (PP) content (50 phr) and nano-silica addition (100 phr) in the formulation, which enhanced the synergistic effect of material rigidity and toughness. The polyurethane composite runway prepared in Example 3 exhibited the highest elongation at break (550%), but slightly lower interfacial peel strength (3.8 N / mm), likely due to its lower PP content (20 phr) and reduced amount of light calcium carbonate, resulting in improved matrix flexibility but slightly weaker interfacial bonding. The yellowing index (ΔY / Y0) of the polyurethane composite runway prepared in Examples 1-3 was all ≤9%, meeting weatherability requirements. The polyurethane composite runway prepared in Example 2 exhibited the best weatherability (Grade 1), attributed to its high UV absorber content (3 phr) and enhanced passivation process (hot air drying + UV irradiation).

[0027] Comparative Example 1: Comparison without adding maleic anhydride (MAH), Objective: To verify the necessity of MAH grafting on interfacial bonding performance.

[0028] Component adjustment: The composition of the thermoplastic elastomer particles is the same as that of Example 1 (containing SEBS, PP matrix, filler, etc.).

[0029] No MAH or BIPB added.

[0030] Process parameters: The reaction extrusion temperature was the same as that in Example 1 (160-175° C.), but without the initiator activation step.

[0031] A polyurethane composite material runway, the materials used for which include thermoplastic elastomer particles and polyurethane prepared by the above method.

[0032] Comparative Example 2: Using unmodified light calcium carbonate filler, Purpose: To verify the effect of filler surface modification on dispersibility and interfacial properties.

[0033] Component adjustment: In the thermoplastic elastomer particles, the modified light calcium carbonate was replaced by unmodified light calcium carbonate (particle size 3 μm).

[0034] The other components are the same as those in Example 1.

[0035] Process parameters: Completely consistent with Example 1.

[0036] A polyurethane composite material runway, the materials used for which include thermoplastic elastomer particles and polyurethane prepared by the above method.

[0037] Comparative Example 3: The MAH / BIPB ratio is too low at 5:1. Objective: To verify the critical value of the ratio of MAH to initiator on reaction efficiency.

[0038] Component adjustment: The addition amount of MAH was 0.5 kg (0.5% of the total formula), and the addition amount of BIPB was 0.1 kg (0.1% of the total formula).

[0039] The other components are the same as those in Example 1.

[0040] Process parameters: The temperature of the reaction section was lowered to 165°C and the reaction time was prolonged to compensate for the inadequate initiator.

[0041] A polyurethane composite material runway, the materials used for which include thermoplastic elastomer particles and polyurethane prepared by the above method.

[0042] Comparative Example 4: Using a common initiator (benzoyl peroxide BPO), Objective: To verify the effect of BIPB initiator on reaction selectivity and grafting effect.

[0043] Component adjustment: BIPB was replaced by dibenzoyl peroxide (BPO), and the amount of MAH added remained at 2.5 kg (the same as in Example 1).

[0044] Process parameters: The temperature of the reaction zone is raised to 180°C (suitable for the decomposition temperature of BPO).

[0045] A polyurethane composite material runway, the materials used for which include thermoplastic elastomer particles and polyurethane prepared by the above method.

[0046] Comparative Example 5: No passivation treatment was performed. Purpose: To verify the effect of passivation treatment on particle surface stability and weather resistance.

[0047] Component adjustment: The components are exactly the same as in Example 1.

[0048] Process parameters: The passivation treatment step is omitted after granulation (no hot air drying and ultraviolet irradiation).

[0049] A polyurethane composite material runway, the materials used for which include thermoplastic elastomer particles and polyurethane prepared by the above method.

[0050] Comparative Example 6: The screw speed is set too high (for example: 800 rpm), Purpose: To verify the negative effect of screw speed on reaction residence time and grafting depth.

[0051] Component adjustment: The components are exactly the same as in Example 1.

[0052] Process parameters: The screw speed was increased to 800 rpm and the residence time was shortened to 50 s.

[0053] A polyurethane composite material runway, the materials used for which include thermoplastic elastomer particles prepared by the above method and polyurethane.

[0054] Table 2 below compares the performance of the polyurethane composite runway materials produced in Example 1 and Comparative Examples 1-6. Peel strength was measured according to ASTM D903, Standard Test Method for Peel Strength of Adhesives; yellowing index (ΔY / Y0) was measured according to GB / T 16422; and tensile strength and elongation at break were measured according to GB / T 10654-2001.

[0055] Table 2 Performance comparison of the polyurethane composite runway prepared in Example 1 and Comparative Examples 1-6

[0056] As can be seen from Table 2: the interfacial peel strength of the runway obtained in Comparative Example 1 (no MAH added) dropped sharply to 1.5 N / mm, confirming the necessity of maleic anhydride grafting to improve the interfacial bonding strength; the peel strength (2.5 N / mm) of the runway obtained in Comparative Example 2 (unmodified light calcium carbonate) was significantly lower than the peel strength (4.0 N / mm) of the runway obtained in Example 1, indicating that filler surface modification plays a decisive role in dispersibility and interfacial bonding; in Comparative Example 3 (MAH / BIPB ratio is too low) the grafting reaction is insufficient due to insufficient initiator, and the interfacial peel strength (2.0 N / mm) and tensile strength (17 MPa) decreased, verifying the critical value of the initiator ratio in this application; in Comparative Example 4 (using BPO initiator), the grafting depth of the resulting runway was unevenly distributed (10-40 μm) and the yellowing index increased (12%) due to the mismatch between the initiator decomposition temperature and the process, indicating that BIPB is more suitable for the temperature control requirements of gradient grafting; in Comparative Example 5 (no passivation treatment), the material yellowed (ΔY / Y0 increased to 14%) and the interfacial performance deteriorated, with a significant decrease in weather resistance (ΔE=3.0 after QUV3000h, weatherability rating of level 4). The interfacial peel strength (3.2 N / mm) was lower than that of Example 1 (4.0 N / mm), demonstrating that passivation treatment can eliminate surface active groups and improve interfacial bonding stability; in Comparative Example 6 (excessive screw speed) the residence time was insufficient (50 s), resulting in a grafting depth of only 6 μm and a significantly decreased interfacial strength (2.8 N / mm), highlighting the importance of process synergy between screw speed and residence time.

[0057] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for modifying thermoplastic elastomer particles for polyurethane runways, characterized in that: The steps are as follows: S1. Prepare thermoplastic elastomer particles of appropriate particle size; S2. Maleic anhydride pretreatment: drying the maleic anhydride to make its moisture content ≤0.1wt%; S3. Premixing: Evenly mixing the thermoplastic elastomer particles, maleic anhydride, and di-tert-butyl dicumyl peroxide in a certain ratio to prepare a mixture; S4, reactive extrusion: the mixed material is added to a twin-screw extruder with an L / D ≥ 40 for gradient grafting, including i) a melt mixing section at 160-165°C, ii) a reaction section at 170-175°C, and iii) a homogenization section at 168-172°C. The decomposition rate of maleic anhydride is controlled to be ≤3%, the surface grafting depth is 10-50 μm, and a kneading block is output from the discharge end of the twin-screw extruder. S5. Granulation and post-processing: The kneaded block is pelletized underwater, and the pellets are passivated.

2. The method for modifying thermoplastic elastomer particles for polyurethane runway according to claim 1, characterized in that: The thermoplastic elastomer particles in step S1 include the following components in parts by mass: Styrene-ethylene-butylene-styrene block copolymer 100-190 phr, Polypropylene 20-40 phr, White oil 90~130 phr, Modified light calcium carbonate 150~300 phr, Iron oxide red 0~30 phr, Antioxidant 2.5~4.5 phr, UV absorber 1.5~3 phr, Nano-silicon dioxide 50-200phr.

3. The method for modifying thermoplastic elastomer particles for polyurethane runway according to claim 1, characterized in that: The mixing process in step S3 is carried out in an inert gas protection atmosphere, and the humidity in the mixing environment is ≤30%RH.

4. The method for modifying thermoplastic elastomer particles for polyurethane runway according to claim 1, characterized in that: In step S3, the thermoplastic elastomer particles, maleic anhydride, and di-tert-butyl dicumyl peroxide are mixed in a weight ratio of 100:2-2.5:0.5-0.

6.

5. The method for modifying thermoplastic elastomer particles for polyurethane runway according to any one of claims 1 to 4, characterized in that: The correlation equation between the screw speed and residence time of the twin-screw extruder in step S4 is t=0.015L / D·n⁻¹, where t is the residence time / min and n is the speed / rpm.

6. The method for modifying thermoplastic elastomer particles for polyurethane runways according to any one of claims 1 to 4, characterized in that: The screw assembly in the melt mixing section of step S4 contains at least two forward conveying elements.

7. The method for modifying thermoplastic elastomer particles for polyurethane runway according to any one of claims 1 to 4, characterized in that: The reaction section in step S4 contains at least three groups of kneading blocks arranged in a 30° / 60° staggered manner, with a residence time of 90 to 120 seconds.

8. The method for modifying thermoplastic elastomer particles for polyurethane runway according to any one of claims 1 to 4, characterized in that: The vacuum degree in the homogenization section of step S4 is ≤-0.08 MPa.

9. The method for modifying thermoplastic elastomer particles for polyurethane runways according to any one of claims 1 to 4, characterized in that: In step S5, the water temperature is 20-30° C., and the particle size of the cut particles is 2-4 mm. The passivation treatment is specifically: hot air drying at 70-90° C. for 0.5-2 h or ultraviolet irradiation treatment.

10. A polyurethane composite runway, characterized in that: The materials used include thermoplastic elastomer particles and polyurethane prepared by the modification method of thermoplastic elastomer particles for polyurethane runways according to claims 1 to 9.

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