Polypropylene material for asphalt reinforcement and process for the preparation thereof

Abstract

The application discloses a polypropylene material for reinforcing asphalt and a preparation method thereof. The polypropylene material is prepared through a skin-core composite extrusion process and has a skin-core structure. The skin layer structure comprises high-rigidity homopolymer polypropylene, GPPS, grafted modified SBS, AC type foaming agent, antioxidant, light stabilizer and lubricant. The core layer structure comprises high-impact copolymer polypropylene, antioxidant, light stabilizer and lubricant. The polypropylene material has excellent mechanical properties and excellent compatibility with asphalt material, and can be used for preparing modified asphalt material and repairing defects such as pits and cracks of asphalt pavement.

Description

TECHNICAL FIELD

[0001] The present application relates to polypropylene materials, in particular to polypropylene materials for asphalt reinforcement. BACKGROUND

[0002] As one of the five general resins, polypropylene resin is one of the largest production, consumption and application of polymer materials in the world. Polypropylene has the advantages of small density, high strength, heat resistance, good insulation, low dielectric constant, low dielectric loss, low price and excellent chemical stability, and is favored in the fields of household appliances, automobiles, electronics, medical treatment, etc.

[0003] Asphalt pavement is widely used in road construction in China. More than 80% of the expressways built in China use asphalt pavement. Asphalt pavement has many advantages such as good driving stability, short construction period, convenient maintenance and repair, etc. However, asphalt is a typical viscoelastic material, which is sensitive to temperature. In extremely high or low temperature environment, it is easy to cause cracks, potholes and other pavement damages, thereby affecting the safety of high-speed driving. For the asphalt pavement diseases that have occurred, timely repair is needed. However, the main problem in the process of repairing asphalt pavement diseases is that the compactness, deformation resistance and bonding force of the repaired asphalt are not good, which leads to the easy falling off and cracking of the repaired potholes and cracks, and repeated repair is needed. However, it is found that the traditional polypropylene material has poor compatibility with asphalt and obvious segregation phenomenon, which is not suitable for modifying asphalt alone.

[0004] Patent CN115746546A uses high-temperature flame spray gun to melt polypropylene-based pavement repair material for pothole repair. The components do not have good compatibility with asphalt pavement, resulting in poor bonding capacity with the pavement, and the use of open flame in the construction process can easily cause fire accidents.

[0005] Patent CN115044219A uses DCP to degrade polypropylene to prepare polypropylene modified asphalt. Peroxide degradation of polypropylene can reduce the strength and rigidity of polypropylene, resulting in poor high-temperature resistance of the modified asphalt.

[0006] Patent CN105037948A uses PE&PS alloy and PP to modify asphalt. First, the compatibility of PE and PS is poor, and no compatibilizer is added, resulting in poor comprehensive performance of the alloy. Second, the compatibility of PP and asphalt is poor, which can easily lead to segregation.

[0007] Therefore, it is necessary to develop a polypropylene material with excellent compatibility with asphalt material for preparing modified asphalt material to solve the technical deficiencies of existing repair materials. SUMMARY

[0008] The present application aims at providing a polypropylene material with excellent compatibility with asphalt material to overcome the drawbacks in the prior art. The present application controls the skin-core structure of the material, fully utilizes the porous structure of the skin layer resin to adsorb light components of asphalt, improves the hardening speed of asphalt, the benzene ring structure of polystyrene in the skin layer resin forms π-π interaction with the ring aromatic hydrocarbon in the asphalt component, improves the interaction with asphalt material, the skin layer resin has excellent rigidity and heat resistance, and the high-impact copolymerized polypropylene in the core layer structure has excellent toughness, which improves the high-temperature resistance of asphalt material.

[0009] To achieve the above-mentioned application purposes, the present application adopts the following technical solutions:

[0010] A polypropylene material for reinforcing asphalt, which is a skin-core double-layer structure, wherein

[0011] The skin layer structure resin comprises the following raw materials in mass fraction:

[0012] High-rigidity homopolymerized polypropylene: 40-70 parts

[0013] GPPS: 20-40 parts

[0014] Graft-modified SBS: 5-15 parts

[0015] AC type foaming agent: 2-5 parts

[0016] Antioxidant: 0.2-1 part

[0017] Light stabilizer: 0.2-0.5 parts

[0018] Lubricant: 0.2-0.5 parts

[0019] The core layer structure resin comprises the following raw materials in mass fraction:

[0020] High-impact copolymerized polypropylene: 98-99 parts

[0021] Antioxidant: 0.2-1 part

[0022] Light stabilizer: 0.2-0.5 parts

[0023] Lubricant: 0.2-0.5 parts

[0024] The total mass of the skin layer structure resin and the core layer structure resin is 100%, wherein the skin layer structure resin accounts for 30-50% of the total mass of the material, and the core layer structure resin accounts for 50-70% of the total mass of the material.

[0025] The graft-modified SBS in the present application comprises the following raw materials in mass fraction:

[0026] SBS: 95-98 copies

[0027] Acrylate ionic crosslinking agent: 2-5 parts.

[0028] In this invention, the styrene content of the SBS is 20-40% by mass, the melt index is ≥1.5g / 10min, and the test conditions are 200℃ and 5kg.

[0029] In this invention, the acrylate ion crosslinking agent of the skin structure resin is a zinc dimethacrylate ion crosslinking agent.

[0030] The preparation method of grafted modified SBS in this invention includes the following steps: grafting modification of SBS with acrylate ionic crosslinking agent by internal mixing reaction, wherein the internal mixing reaction time is 15-30 min, the internal mixer temperature is 210-230℃, and the rotation speed is 20-40 r / min.

[0031] In this invention, the melt index of the high-rigidity homopolymer polypropylene of the skin structure resin is 5-20 g / 10 min, and the test conditions are 230℃ and 2.16 kg; HDT>105℃, and the test conditions are 0.45 MPa.

[0032] In this invention, the melt index of GPPS in the skin structure resin is ≥5g / 10min, and the test conditions are 200℃ and 5kg.

[0033] In this invention, the decomposition temperature range of the AC-type foaming agent in the skin structure resin is 220-240℃.

[0034] In this invention, the antioxidant in the skin structure resin is one or more of hindered phenolic antioxidants, phosphite antioxidants, and thioester antioxidants.

[0035] In this invention, the light stabilizer in the skin structure resin is a hindered amine light stabilizer.

[0036] In this invention, the lubricant in the skin structure resin is one or more of zinc stearate and ethylene bis-stearamide.

[0037] In this invention, the high-impact copolymer polypropylene in the core layer structure resin has a melt index of 3-30 g / 10 min, and is tested at 230°C with a weight of 2.16 kg; the notched impact strength of the cantilever beam at 23°C is >30 KJ / m. 2 .

[0038] In this invention, the antioxidant in the core layer structure resin is one or more of hindered phenolic antioxidants, phosphite antioxidants, and thioester antioxidants.

[0039] In this invention, the light stabilizer of the core layer structure resin is a hindered amine light stabilizer.

[0040] In this invention, the lubricant in the core layer structure resin is one or more of zinc stearate and ethylene bis-stearamide.

[0041] In this invention, the method for preparing the polypropylene material includes the following steps:

[0042] (1) The raw material of the outer layer is placed in a twin-screw extruder and subjected to high-temperature melt dispersion extrusion granulation to obtain the outer layer resin;

[0043] (2) The raw material of the outer layer is placed in a twin-screw extruder for high-temperature melt dispersion extrusion granulation to obtain the inner layer resin;

[0044] (3) The skin resin and core resin are respectively placed in two single-screw extruders for plasticization, and the polypropylene material for asphalt reinforcement is prepared by stretching and pelletizing through co-extrusion die head. The polypropylene material has a diameter of 1-2 mm and a length of 10 mm.

[0045] In this invention, the twin-screw extruder in steps (1) and (2) has a screw length-to-diameter ratio of (40-52):1, a screw speed of 100-300 r / min, and an extrusion temperature of 190-200℃.

[0046] In this invention, the screw length-to-diameter ratio of the single screw extruder in step (3) is (25-35):1, the screw speed is 100-300 r / min, and the extrusion temperature is 220-240℃.

[0047] The technical solution of this invention has the following advantages over existing technical solutions:

[0048] (1) The polypropylene material in this invention adopts a core-skin structure. The skin layer uses high-rigidity homopolymer polypropylene and GPPS as the main resin, which has excellent rigidity and heat resistance, and improves the high temperature resistance of the asphalt material. Graft-modified SBS is used as a compatibilizer, which can improve the compatibility between polypropylene and GPPS. At the same time, through ionic cross-linking, it only swells during the mixing process with asphalt, avoiding the dissolution of uncross-linked SBS by the light components of asphalt, thereby affecting the compatibility between polypropylene and GPPS.

[0049] (2) The polypropylene material in this invention adopts a core-skin structure. The skin layer uses AC foaming agent to form a porous structure during co-extrusion. The resulting porous structure adsorbs the light components of asphalt, increases the speed of asphalt hardness establishment, and improves construction efficiency. The benzene ring structure in the polystyrene and SBS resin of the skin layer establishes π-π interaction with the cyclic aromatic hydrocarbons in the asphalt components, which improves its compatibility with asphalt materials and solves the segregation phenomenon caused by the poor compatibility between traditional polypropylene materials and asphalt, thereby improving the splitting strength of polypropylene-reinforced asphalt materials.

[0050] (3) The polypropylene material in this invention adopts a core-skin structure. The high-impact copolymer polypropylene used in the core layer has excellent toughness, which improves the low-temperature toughness of the asphalt material. Detailed Implementation

[0051] To better understand the technical solution of the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments. Unless otherwise specified, the raw materials used in the embodiments or comparative examples are commercially available raw materials.

[0052] The apparatus and main raw material sources used in the embodiments and comparative examples of this invention are as follows:

[0053] Twin-screw extruder: Model SK-26, screw length-to-diameter ratio 50:1; Nanjing Keya Chemical Complete Equipment Co., Ltd.

[0054] Single-screw co-extrusion equipment: Model HRJSJ-35, screw length-to-diameter ratio 28:1, Foshan Hairuijia Precision Extrusion Machinery Co., Ltd.;

[0055] Internal mixer: Model RX 5-10L, Ruian Rixin Rubber & Plastic Machinery Co., Ltd.;

[0056] High-strength homopolymer polypropylene: 6012, melt index 12g / 10min, China Petroleum & Chemical Corporation;

[0057] GPPS resin: GPPS2601, melt index 11g / 10min, test conditions 200℃, 5kg, INEOS Styrene Group Co., Ltd.

[0058] SBS resin: YH-796, styrene mass fraction 38%, melt index 2g / 10min, test conditions 200℃, 5kg;

[0059] Acrylate ionic crosslinking agent: DYMALINK 9200, Total Chemicals Ltd.;

[0060] AC type foaming agent: DGH-2, foaming temperature 230℃, Wuhan Deguan New Material Technology Co., Ltd.;

[0061] High-impact copolymer polypropylene: SP179P, melt index 10g / 10min, test conditions 230℃, 2.16kg;

[0062] The notched impact strength of the cantilever beam at 23℃ is 45 KJ / m. 2 China Petroleum & Chemical Corporation (Sinopec);

[0063] Lubricant: Zinc stearate, FARKS GmbH, Italy;

[0064] Main antioxidant: 1010, from a rising star in chemistry;

[0065] Co-antioxidant: 168, a rising star in chemistry;

[0066] Light stabilizer: 5585, a rising star in the chemical industry;

[0067] All other raw materials were commercially available and of analytical grade.

[0068] The performance characterization method of the polypropylene material of the present invention is as follows:

[0069] Polypropylene reinforced asphalt material preparation process: Add asphalt raw materials to a heating tank and heat to 150°C, stir and mix for 30 minutes, add 5% by weight of polypropylene material to the asphalt and stir and mix for 10 minutes to prepare polypropylene reinforced asphalt material.

[0070] The softening point, ductility, splitting strength at room temperature (15℃), and splitting strength at low temperature (-10℃) of polypropylene reinforced asphalt were tested in accordance with the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTGE20-2011).

[0071] Surface drying time of polypropylene reinforced bitumen: Tested according to GB / T13477.5-2002, and the time it takes for the sample to no longer adhere to the fingers is recorded.

[0072] Examples 1-3

[0073] Graft-modified SBS was prepared according to the raw materials and dosages in Table 1.

[0074] Preparation method of grafted modified SBS: Weigh each raw material according to the weight ratio, then put them into a high-speed mixer and mix for 3 minutes. Then, put them into an internal mixer for internal mixing. The mixing temperature is 220℃ and the speed is 40r / min. After 15 minutes of internal mixing, grafted modified SBS is obtained.

[0075] Table 1. Raw material usage in Examples 1-3

[0076] S1 S2 S3 YH-796 98 97 95 DYMALINK 9200 2 3 5

[0077] Examples 4-7 (i.e., S4-7) and Comparative Examples 1-9 (i.e., D1-9) were prepared according to the raw materials and amounts in Table 2.

[0078] The preparation method of the outer layer resin is as follows: weigh each raw material according to the weight ratio, then put it into a high-speed mixer and mix for 3 minutes. Then feed it from the main feed port of the twin-screw extruder. The screw speed is 300 r / min and the extrusion temperature is 190℃. After high-temperature melting and dispersion, the outer layer resin is obtained by extrusion granulation.

[0079] The preparation method of the core layer resin is as follows: weigh each raw material according to the weight ratio, then put it into a high-speed mixer and mix for 3 minutes. Then feed it from the main feed port of the twin-screw extruder. The screw speed is 300 r / min and the extrusion temperature is 190℃. After high-temperature melting and dispersion, the inner layer resin is obtained by extrusion granulation.

[0080] The preparation method of polypropylene material is as follows: the skin layer resin and the core layer resin are respectively placed in two single-screw extruders for plasticization, and the polypropylene material for asphalt reinforcement is prepared by stretching and pelletizing through a co-extrusion die. The polypropylene material has a diameter of 1.5 mm and a length of 10 mm.

[0081] Table 2. Raw material usage and properties of Examples 4-7 and Comparative Examples 1-9

[0082]

[0083]

[0084] Table 2 shows that the polypropylene materials in Examples 4-7 adopt a core-skin structure. The skin layer uses high-rigidity homopolymer polypropylene and GPPS as the main resins, which have excellent rigidity and heat resistance, improving the high-temperature resistance of the asphalt material and giving it a higher softening point. Graft-modified SBS is used as a compatibilizer, which can improve the compatibility between polypropylene and GPPS. At the same time, through ionic cross-linking, it only swells during the mixing process with asphalt, avoiding the dissolution of uncross-linked SBS by the light components of asphalt, thus preventing the compatibility between polypropylene and GPPS from being affected. This results in polypropylene-reinforced asphalt having excellent ductility. Meanwhile, AC foaming agent is used in the skin layer. The resulting porous structure adsorbs the light components of asphalt, which can reduce the surface drying time of polypropylene-reinforced asphalt and increase the asphalt hardness build-up speed, thereby improving construction efficiency. The π-π interaction between the benzene ring structure in the polystyrene and SBS resins in the skin layer and the cyclic aromatic hydrocarbons in the asphalt components improves their compatibility with the asphalt material, solving the segregation phenomenon caused by the poor compatibility between traditional polypropylene materials and asphalt, and improving the splitting strength of polypropylene-reinforced asphalt materials. The high-impact copolymer polypropylene with a polypropylene core structure has excellent toughness, which improves the low-temperature splitting performance of asphalt materials.

[0085] Compared to Example 4, Comparative Example 1 did not add GPPS to the skin resin, resulting in a weaker interaction between the polypropylene material and the asphalt, leading to poorer ductility and splitting strength of the prepared asphalt.

[0086] Compared to Example 4, Comparative Example 2 did not add grafted modified SBS to the skin resin, resulting in poor compatibility between polypropylene and GPPS in the skin, leading to poor ductility and splitting strength of the prepared asphalt material.

[0087] Compared to Example 4, Comparative Example 3 did not include AC foaming agent in the skin resin, and the skin resin could not form a porous structure, resulting in a longer surface drying time for the prepared asphalt material.

[0088] Compared to Example 4, Comparative Example 4 did not prepare grafted modified SBS by mixing the acrylate ionic crosslinking agent with SBS in advance during the preparation of the skin resin. As a result, the ionic crosslinking agent was prone to grafting reaction with PP and GPPS during the extrusion process, resulting in a lower SBS grafting rate in the final system. This made it easier for the SBS in the skin to be dissolved by the light components of the asphalt during the mixing process with asphalt, affecting the compatibility of polypropylene and GPPS, and resulting in poor ductility and splitting strength of polypropylene-reinforced asphalt.

[0089] Compared to Example 4, Comparative Example 5 used SBS that was not subjected to intensive grafting modification, which made the SBS in the skin layer easily dissolved by the light components of the asphalt during the mixing process with asphalt, affecting the compatibility of polypropylene and GPPS, resulting in poor ductility and splitting strength of polypropylene-reinforced asphalt.

[0090] Compared to Example 4, Comparative Example 6 has a lower mass ratio of skin resin, which reduces the content of foam cells formed after foaming, thereby reducing the adsorption of light asphalt components and prolonging the surface drying time of polypropylene reinforced asphalt.

[0091] Compared to Example 4, Comparative Example 7 has a lower mass ratio of core resin, which affects the low-temperature toughness of polypropylene reinforced asphalt material, resulting in poor low-temperature splitting strength and brittle fracture.

[0092] Compared to Example 4, Comparative Example 8 does not contain core layer resin, which affects the low-temperature toughness of the polypropylene reinforced asphalt material, resulting in poor low-temperature splitting strength and brittle fracture.

[0093] Compared to Example 4, Comparative Example 9 does not contain skin resin, which results in poor compatibility between the polypropylene material and the asphalt material, and thus poor splitting strength of the material.

[0094] The above description of the embodiments is intended to enable those skilled in the art to understand and apply the present invention. Those skilled in the art can readily make various modifications to the embodiments and apply the general principles described herein to other embodiments without inventive effort. Therefore, the present invention is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A polypropylene material for asphalt reinforcement, which is a skin-core double-layer structure, wherein the skin layer structure resin comprises the following raw materials in mass fraction: high-rigid homopolymer polypropylene: 40-70 parts GPPS: 20-40 parts graft-modified SBS: 5-15 parts AC type foaming agent: 2-5 parts antioxidant: 0.2-1 part light stabilizer: 0.2-0.5 part lubricant: 0.2-0.5 part; the core layer structure resin comprises the following raw materials in mass fraction: high-impact copolymer polypropylene: 98-99 parts antioxidant: 0.2-1 part light stabilizer: 0.2-0.5 part lubricant: 0.2-0.5 part wherein the skin layer structure resin accounts for 30-50% of the total mass of the material, and the core layer structure resin accounts for 50-70% of the total mass of the material, based on the total mass of the skin layer structure resin and the core layer structure resin being 100%; the graft-modified SBS comprises the following raw materials in mass fraction: SBS: 95-98 parts acrylate ionic crosslinking agent: 2-5 parts; the SBS is graft-modified by mixing and reacting the SBS and the acrylate ionic crosslinking agent through a banbury mixer. The method for preparing the graft-modified SBS comprises the following steps: the mass fraction of styrene in the SBS is 20-40%, and the melt index is ≥1.5 g / 10 min under the test condition of 200℃ and 5 kg.

2. The material of claim 1, wherein, the acrylate ionic crosslinking agent is a dimethyl zinc acrylate ionic crosslinking agent.

3. The material of claim 1, wherein the high-rigid homopolymer polypropylene in the skin layer structure resin has a melt index of 5-20 g / 10 min under the test condition of 230℃ and 2.16 kg, and a HDT > 105℃ under the test condition of 0.45 MPa.

4. The material of claim 1, wherein, the GPPS in the skin layer structure resin has a melt index ≥5 g / 10 min under the test condition of 200℃ and 5 kg.

5. The material of claim 1, wherein the AC type foaming agent in the skin layer structure resin has a decomposition temperature range of 220-240℃.

6. The material of claim 1, wherein 8. A preparation method of the material according to any one of claims 1-7, comprising the following steps:

7. The material of claim 1, wherein The high impact copolymerized polypropylene in the core layer structure resin has a melt index of 3-30 g / 10 min, a test condition of 230 °C, 2.16 kg, and a cantilever beam notched impact strength at 23 °C > 30 KJ / m 2 . (1) placing the raw materials of the skin layer into a double-screw extruder to perform high-temperature melt dispersion extrusion and granulation to obtain a skin layer resin; (2) placing the raw materials of the core layer into a double-screw extruder to perform high-temperature melt dispersion extrusion and granulation to obtain a core layer resin; (3) placing the skin layer resin and the core layer resin into two single-screw extruders respectively to perform plasticization, and then performing co-extrusion through a die drawing and cutting to obtain a polypropylene material for asphalt reinforcement, wherein the diameter of the polypropylene material is 1-2 mm, and the length is 10 mm. ​

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