A binder for a polyurethane concrete pavement for cold recycling of reclaimed asphalt pavement (RAP)

Abstract

The present invention provides a binder for a polyurethane concrete pavement used for cold recycling of reclaimed asphalt pavement (RAP). This binder belongs to one-component moisture-curing type and is prepared by reacting isocyanate, polyether polyol, recycled polyester polyol, compatible additives, stabilizer, etc. under certain temperature and specific synthesis process conditions. Compared with the existing one-component polyurethane binder, recycled polyester polyol is adopted, and the polyester polyol and polyether polyol can maintain a homogeneous state within 30 days under the action of the compatible additive; at the same time, the use of recycled polyester polyol can further reduce the cost of the polyurethane binder, while improving the bonding performance to RAP material, and the blending ratio of RAP reaches more than 80%. The polyurethane concrete pavement prepared by using this binder and high-proportion RAP has high strength, simple operation, and more environmental protection advantages, and has great application value for large-scale promotion.

Description

Technical Field

[0001] The present invention belongs to the technical field of road materials engineering, and particularly relates to a binder for a polyurethane concrete pavement used for cold recycling of asphalt mixture recycled materials (RAP). Background Art

[0002] As of 2019, the total mileage of highways in China was 5.0125 million kilometers, of which the expressway mileage was nearly 150,000 kilometers. Among them, the highway maintenance mileage reached 4.9531 million kilometers, accounting for 98.8% of the total highway mileage. The highway has entered the maintenance era, and the asphalt pavement mixture (RAP) generated by highway maintenance each year reaches 70 million - 90 million tons. Research on various asphalt pavement recycling technologies has become a hot topic in the industry. Although traditional plant - mix hot recycling, in - situ cold recycling and other methods can achieve a recycling rate of 80 - 100%, they can basically not be used for the original pavement surface layer structure, resulting in low added value of the high - quality surface layer RAP of the original pavement.

[0003] The structural strength of asphalt mixture depends to a large extent on the internal friction and cohesion of the mixture. However, its own cohesion is limited, which causes many limitations in using asphalt materials to recycle RAP to prepare mixtures. Moreover, when preparing high - grade pavements, the blending ratio of RAP is relatively low. Taking the most mature plant - mix hot - recycled asphalt mixture as an example, the blending ratio of RAP old materials is generally low, usually 10% - 30%, or even lower. It is necessary to perform secondary screening on PAR, and some PAR materials do not meet the requirements of the hot - mix recycling standard.

[0004] Polyurethane adhesives have excellent bonding properties with stone materials, and also have excellent mechanical strength, aging resistance, hydrolysis resistance, fatigue resistance and low - temperature resistance. They are widely used in steel bridge deck paving and highly elastic porous pavements. Since the polyurethane formula design is very flexible, diverse properties can be obtained through different formula designs.

[0005] The invention patent with the application number 201410424976.1 discloses a warm - mix recycled asphalt mixture, which is composed of warm - mix recycled asphalt, new aggregates and old asphalt mixture RAP. It reduces the high - temperature energy consumption of traditional hot - recycled asphalt mixtures. At the same time, the incorporation amount of old asphalt mixture is increased to 50%. For this warm - mix asphalt, the asphalt temperature still needs to be heated to above 100°C during the mixing process. Moreover, due to the mechanical property limitations of asphalt itself, the strength improvement of the prepared mixture is limited, and the addition ratio of asphalt mixture recycled materials (RAP) is also limited.

[0006] The invention patent with the application number CN 202010023942.7 discloses a polyether-type polyurethane concrete paving material. The polyether-type polyurethane binder is used to mix with aggregates at normal temperature to form polyether-type polyurethane concrete. The cold mixing and cold paving construction method is adopted, which has the advantages of extending the construction period and avoiding the emission of harmful gases during the mixing process. It has excellent road performance and anti-aging ability. However, during its use, a multi-functional oxazolidine latent curing agent is adopted. Although it reduces the problem of single-component curing bubbles, the oxazolidine latent curing agent has a high price, poor economy, and releases secondary pollution gases such as aldehydes and ketones during the curing process. Moreover, the strength of the polyether-type polyurethane binder is generally lower than that of the polyester-type binder, and the stone materials used are also new aggregates, which are still insufficient in terms of economy and environmental protection performance.

[0007] The invention patent with the application number 201910629418.1 discloses a polyurethane rubber porous mixture for concrete bridge deck paving. Utilizing the excellent bonding performance of the polyurethane binder, waste rubber particles are used in the bridge deck paving project, combined with new basalt aggregates, for concrete bridge deck paving, which can improve the road performance, reduce the density of the mixture, reduce the constant load of the bridge, and recycle waste rubber particles at the same time. However, this patent still needs to use new stone materials, and the selected polyurethane binder is a two-component, with relatively high costs and complex operations, which is not suitable for large-scale promotion. Summary of the Invention

[0008] To solve the problem of high-value recycling of reclaimed asphalt pavement (RAP), the present invention provides a one-component moisture-curing polyurethane binder and its preparation method. This binder has excellent bonding performance and strength, can recycle RAP at a high proportion to prepare pavements of all grades, and has the advantages of stable storage, simple operation, and use of recycled materials, creating conditions for high-value recycling and reuse of RAP.

[0009] The present invention provides a polyurethane binder prepared by mixing recycled aromatic polyester polyol and polyether. Through special additives, the polyester-polyether mixed system can be maintained in a homogeneous state without stratification and sedimentation within 30 days. If stratification occurs subsequently, it can be simply mixed to be uniform. At the same time, it has excellent bonding performance, and the proportion of recycled asphalt pavement (RAP) that can be recycled reaches more than 80%, meeting the application requirements of pavements of all grades.

[0010] To achieve the above objectives, the present invention adopts the following technical solutions:

[0011] The present invention provides a binder for a polyurethane concrete pavement for cold recycling of reclaimed asphalt pavement (RAP), which includes the following components in weight percentage:

[0012]

[0013] The viscosity (at 25°C) of the binder described in the present invention is 800 - 2500 mPa·s, preferably 1000 - 2000 mPa·s, and more preferably 1300 - 1500 mPa·s.

[0014] The polyether polyol A has a number average molecular weight of 1000 - 8000, preferably 1500 - 4000, a functionality of 2 - 4, a hydroxyl value of 20 - 80 mg KOH / g, and its dosage is 35% - 50%, preferably 35% - 45%, and more preferably 40% - 45%.

[0015] The polyester polyol B is a recycled aromatic polyester polyol, prepared from raw materials such as PET waste plastics recycled and degraded, or polyester waste, PTA residues, etc. and diethylene glycol, with a number average molecular weight of 200 - 5000, preferably 400 - 3000, a functionality of 2 - 4, a hydroxyl value of 20 - 300 mg KOH / g, and its dosage is 5% - 15%, preferably 5% - 12%, and more preferably 5% - 8%.

[0016] The isocyanate is one or more of diphenylmethane diisocyanate and polyphenylmethane polyisocyanate, and its dosage is 25% - 45%, preferably 30% - 40%, and more preferably 30% - 35%.

[0017] The auxiliary agent is an aromatic hydrocarbon heavy fraction, industrial grade, with a boiling point greater than 260°C, and its dosage is 10% - 25%, preferably 10% - 20%, and more preferably 10% - 15%.

[0018] The stabilizer is one or more of benzoyl chloride, adipoyl chloride, 3,5 - dimethylbenzoyl chloride, phosphoric acid, and oleic acid, and its dosage is 0.01% - 0.1%, preferably 0.02% - 0.08%, and more preferably 0.03% - 0.06%.

[0019] Through the action of the auxiliary agent, the present invention can ensure that the polyurethane binder prepared from recycled aromatic polyester polyol and polyether polyol remains in a homogeneous state within 30 days;

[0020] The present invention uses recycled polyester polyol, which can further reduce the cost of the polyurethane binder and improve the bonding performance to RAP material at the same time.

[0021] The preparation method of the polyurethane binder described in the present invention includes:

[0022] (1), Using recycled polyester polyol B as the hydroxyl component, isocyanate as the NCO group component, and adding an auxiliary agent, reacting at a certain temperature for a period of time to synthesize a terminal NCO group prepolymer;

[0023] (2) Maintain a certain temperature and stirring conditions, add polyether polyol A to the prepolymer, and continue to react with the free isocyanate in the prepolymer of the previous step to obtain a further reacted prepolymer;

[0024] (3) Add a stabilizer to the system, stir for a certain time, and mix evenly to obtain the binder;

[0025] In step (1), preferably, the reaction temperature is 65 - 75 °C, and the reaction time is 1 - 1.5 hours;

[0026] In step (2), preferably, the reaction temperature is 75 - 85 °C, and the reaction time is 3 - 4 hours.

[0027] The positive effects of the present invention are as follows:

[0028] 1. A new and economical idea is adopted to solve the problems of low utilization efficiency and low recycling value of recycled asphalt pavement (RAP). By designing the components of the binder and introducing a more economical and environmentally friendly regenerated polyester polyol, the bonding strength of the binder is improved, and the proportion of recycled asphalt pavement (RAP) that can be recycled reaches more than 80%, meeting the application requirements of various levels of road surfaces;

[0029] 2. The regenerated polyester used, and the polyurethane binder prepared by mixing with polyether, by adding a special additive system, significantly improves the compatibility of the polyester with strong polarity and the polyether system with weak polarity, solves the compatibility problem between polyester-based polyurethane prepolymers and polyether-based polyurethanes, can maintain a homogeneous state within 30 days, and if stratification occurs subsequently, it can also be mixed evenly by simple stirring and maintain the previous homogeneous state for more than 30 days;

[0030] 3. The polyurethane binder prepared by the present invention maintains a low viscosity state at room temperature, is easy to mix with aggregates, and is simple to construct. Specific Embodiments

[0031] The following further illustrates the present invention with specific embodiments, but the content of the present invention is not limited to the following embodiments, and should also include any other known changes within the scope of the rights required by the present invention.

[0032] Some raw material information in the embodiments is as follows:

[0033] LPS5005: A regenerated aromatic polyester polyol prepared from PTA (terephthalic acid) residue, with a functionality of 2, a hydroxyl value of 40 - 50 mgKOH / g, a molecular weight of about 2500, a viscosity of 50000 - 90000 mPa·s (25 °C), and a moisture content ≤ 0.15%; Manufacturer: Shanghai Liansheng Chemical Co., Ltd.;

[0034] CARPOL PES-240: A recycled aromatic polyester polyol prepared from recycled PET (polyethylene terephthalate), with a functionality of 2, a hydroxyl value of 240 - 260 mg KOH / g, a molecular weight of approximately 250, a viscosity of 6000 - 7000 mPa·s (25 °C), and a moisture content of ≤0.2%; Manufacturer: Carpenter Co.

[0035] CMA-254: A common aliphatic polyester polyol with a molecular weight of 2000, a functionality of 2, a hydroxyl value of 53 - 59 mg KOH / g, a viscosity of 6000 - 7000 mPa·s (25 °C), and a melting point of 30 - 40 °C; Manufacturer: Yantai Huada Chemical Industry Co., Ltd.

[0036] Wanol C2020: A PPG polyether polyol with a molecular weight of 2000, a functionality of 2, and a hydroxyl value of 54.5 - 57.5 mg KOH / g; Manufacturer: Wanhua Chemical Group Co., Ltd.

[0037] Wanol C2040D: A PPG polyether polyol with a molecular weight of 4000, a functionality of 2, and a hydroxyl value of 26.5 - 29.5 mg KOH / g; Manufacturer: Wanhua Chemical Group Co., Ltd.

[0038] Aromatic heavy fraction: Prepared from reformed C10 aromatic hydrocarbons through high-temperature rectification and separation, industrial grade, with a boiling point greater than 260 °C and not easily volatile; Manufacturer: Jiangsu Hualun Chemical Co., Ltd.

[0039] Propylene carbonate: Battery grade, with a propylene carbonate content of ≥99.7% and a moisture content of ≤0.05%; Manufacturer: Shandong Senjie Clean Technology Co., Ltd.

[0040] Example 1:

[0041] 1. Place a clean three-necked flask in an oil bath at 65 - 75 °C, introduce nitrogen, add 150 g of diphenylmethane diisocyanate, 250 g of polymethylene polyphenyl isocyanate, and 100 g of aromatic heavy fraction, and stir for 5 min to mix evenly; add 50 g of recycled aromatic polyester polyol B (LPS5005), and react at 65 - 75 °C under a nitrogen atmosphere for 1 h to obtain the first-step polyurethane prepolymer.

[0042] 2. While maintaining the temperature and stirring conditions, add 450 g of polyether polyol A (Wanol C2020), and continue to react at 75 - 85 °C under a nitrogen atmosphere for 3 h to obtain the second-step polyurethane prepolymer.

[0043] 3. Lower the temperature to 40°C, add 0.6 g of stabilizer benzoyl chloride, continue stirring for 20 min, and discharge to obtain a binder for a one-component moisture-curing polyurethane concrete pavement used for cold recycling of asphalt mixture recycled materials (RAP).

[0044] Example 2:

[0045] 1. Place a clean three-necked flask in an oil bath at 65 - 75°C, introduce nitrogen, add 150 g of diphenylmethane diisocyanate, 250 g of polymethylene polyphenyl isocyanate, and 150 g of aromatic hydrocarbon heavy fraction, and stir for 5 min to mix evenly; add 50 g of recycled aromatic polyester polyol B (LPS5005), and react at 65 - 75°C under a nitrogen atmosphere for 1.5 h to obtain the first-step polyurethane prepolymer.

[0046] 2. While maintaining the temperature and stirring conditions, add 400 g of polyether polyol A (Wanol C2020), and continue to react at 75 - 85°C under a nitrogen atmosphere for 3.5 h to obtain the second-step polyurethane prepolymer.

[0047] 3. Lower the temperature to 40°C, add 0.6 g of stabilizer benzoyl chloride, continue stirring for 20 min, and discharge to obtain a binder for a one-component moisture-curing polyurethane concrete pavement used for cold recycling of asphalt mixture recycled materials (RAP).

[0048] Example 3:

[0049] 1. Place a clean three-necked flask in an oil bath at 65 - 75°C, introduce nitrogen, add 200 g of diphenylmethane diisocyanate, 200 g of polymethylene polyphenyl isocyanate, and 100 g of aromatic hydrocarbon heavy fraction, and stir for 5 min to mix evenly; add 100 g of recycled aromatic polyester polyol B (LPS5005), and react at 65 - 75°C under a nitrogen atmosphere for 1.5 h to obtain the first-step polyurethane prepolymer.

[0050] 2. While maintaining the temperature and stirring conditions, add 400 g of polyether polyol A (Wanol C2020), and continue to react at 75 - 85°C under a nitrogen atmosphere for 3 h to obtain the second-step polyurethane prepolymer.

[0051] 3. Lower the temperature to 40°C, add 0.5 g of stabilizer benzoyl chloride, continue stirring for 20 min, and discharge to obtain a binder for a one-component moisture-curing polyurethane concrete pavement used for cold recycling of asphalt mixture recycled materials (RAP).

[0052] Example 4:

[0053] 1. Place a clean three-necked flask in an oil bath at 65 - 75 °C, introduce nitrogen, add 200 g of diphenylmethane diisocyanate, 150 g of polymethylene polyphenyl isocyanate, and 150 g of aromatic hydrocarbon heavy fraction, and stir for 5 min to mix evenly; add 50 g of recycled aromatic polyester polyol B (CARPOL PES-240), and react at 65 - 75 °C under a nitrogen atmosphere for 1.5 h to obtain the first-step polyurethane prepolymer;

[0054] 2. While maintaining the temperature and stirring conditions, add 450 g of polyether polyol A (Wanol C2040D), and continue to react at 75 - 85 °C under a nitrogen atmosphere for 4 h to obtain the second-step polyurethane prepolymer;

[0055] 3. Lower the temperature to 40 °C, add 0.6 g of stabilizer oleic acid, continue to stir for 20 min, and discharge to obtain a one-component moisture-curing polyurethane binder for cold recycling of asphalt mixture recycled materials (RAP) for concrete pavements.

[0056] Comparative Example 1:

[0057] 1. Place a clean three-necked flask in an oil bath at 65 - 75 °C, introduce nitrogen, add 150 g of diphenylmethane diisocyanate, 250 g of polymethylene polyphenyl isocyanate, and 100 g of aromatic hydrocarbon heavy fraction, and stir for 5 min to mix evenly; add 50 g of aliphatic polyester polyol (CMA254), and react at 65 - 75 °C under a nitrogen atmosphere for 1 h to obtain the first-step polyurethane prepolymer;

[0058] 2. While maintaining the temperature and stirring conditions, add 450 g of polyether polyol A (Wanol C2020), and continue to react at 75 - 85 °C under a nitrogen atmosphere for 3 h to obtain the second-step polyurethane prepolymer;

[0059] 3. Lower the temperature to 40 °C, add 0.6 g of stabilizer benzoyl chloride, continue to stir for 20 min, and discharge to obtain a one-component moisture-curing polyurethane binder for cold recycling of asphalt mixture recycled materials (RAP) for concrete pavements.

[0060] Comparative Example 2:

[0061] 1. Place a clean three-necked flask in an oil bath at 65 - 75 °C, introduce nitrogen, add 150 g of diphenylmethane diisocyanate, 250 g of polymethylene polyphenyl isocyanate, and 100 g of propylene carbonate, and stir for 5 min to mix evenly; add 50 g of recycled aromatic polyester polyol B (LPS5005), and react at 65 - 75 °C under a nitrogen atmosphere for 1 h to obtain the first-step polyurethane prepolymer;

[0062] 2. While maintaining the temperature and stirring conditions, add 450 g of polyether polyol A (Wanol C2020), and continue to react for 3 h at 75 - 85 °C under a nitrogen atmosphere to obtain the second-step polyurethane prepolymer;

[0063] 3. Lower the temperature to 40 °C, add 0.6 g of stabilizer benzoyl chloride, continue to stir for 20 min, and discharge to obtain a one-component moisture-curing binder for recycled asphalt pavement (RAP) cold recycling polyurethane concrete pavement.

[0064] Comparative Example 3:

[0065] 1. Place a clean three-necked flask in an oil bath at 65 - 75 °C, introduce nitrogen, add 167 g of diphenylmethane diisocyanate and 278 g of polymethylene polyphenyl isocyanate, stir for 5 min to mix evenly; add 50 g of recycled aromatic polyester polyol B (LPS5005), and react for 1 h at 65 - 75 °C under a nitrogen atmosphere to obtain the first-step polyurethane prepolymer;

[0066] 2. While maintaining the temperature and stirring conditions, add 505 g of polyether polyol A (Wanol C2020), and continue to react for 3 h at 75 - 85 °C under a nitrogen atmosphere to obtain the second-step polyurethane prepolymer;

[0067] 3. Lower the temperature to 40 °C, add 0.6 g of stabilizer benzoyl chloride, continue to stir for 20 min, and discharge to obtain a one-component moisture-curing binder for recycled asphalt pavement (RAP) cold recycling polyurethane concrete pavement.

[0068] Prepare film specimens of the binder body of the experimental examples, test the mechanical properties of the binder body, and test its storage stability. The test methods refer to GB / T 12009.3 - 2009 and GB / T 1040.3 - 2006. The test data are as follows:

[0069]

[0070] Adding recycled aromatic polyester polyol can significantly improve the mechanical properties of the binder. By adding a special compatible additive, aromatic hydrocarbon recombined components, while not reducing the mechanical properties, it can improve the compatibility of the polyester and polyether systems and maintain a homogeneous state within 30 days. Without adding special compatible additives, stratification occurs within a few hours of storage.

[0071] Mix the binder of the experimental example with the sieved recycled asphalt pavement (RAP) to prepare a mixture. Control the binder dosage at 5%, use the dense gradation of AC-13 type for design, control the dosage of the sieved recycled asphalt pavement (RAP) at 80%, and supplement the gradation with S95 grade mineral powder and new aggregates for the rest to fill the voids of the concrete. Compact the sample blocks on both sides 75 times, and then place them in an environment of 30°C / 80% for curing. All tests refer to the specifications: JTG E20-2011, JTG F40-2004, and prepare Marshall specimens for performance testing.

[0072]

[0073] For the mixture prepared with 80% recycled asphalt pavement (RAP) in the above-mentioned example, after testing by JTG E20-2011, the Marshall stability (KN) is between 21 and 34, far greater than the index requirement of >8 KN, and the immersion residual stability is greater than 85%, meeting the specification requirements of AC-13 mixture; the recycled asphalt pavement (RAP) using this binder has excellent road performance and durability, and the recycled asphalt pavement (RAP) can be recycled with high added value.

Claims

1. A binder for a polyurethane concrete pavement for cold recycling of asphalt mixture recycled materials, in terms of weight percentage, comprises the following components: Among them, The polyester polyol B is a recycled aromatic polyester polyol; The auxiliary agent is an aromatic hydrocarbon heavy fraction, industrial grade, with a boiling point greater than 260 °C.

2. The binder according to claim 1, characterized in that, The viscosity of the binder is 800 - 2500 mPa·s at 25 °C.

3. The binder according to claim 1, characterized in that, The polyether polyol A has a number average molecular weight of 1000 - 8000, a functionality of 2 - 4, and a hydroxyl value of 20 - 80 mgKOH / g.

4. The binder according to claim 3, characterized in that, The polyether polyol A has a number average molecular weight of 1500 - 4000.

5. The binder according to claim 1, characterized in that, The polyester polyol B is prepared from raw materials selected from PET waste plastic recycling and degradation, polyester waste, PTA residue and diethylene glycol.

6. The binder according to claim 1 or 5, characterized in that, The polyester polyol B has a number average molecular weight of 200 - 5000, a functionality of 2 - 4, and a hydroxyl value of 20 - 300 mgKOH / g.

7. The binder according to claim 6, characterized in that, The polyester polyol B has a number average molecular weight of 400 - 3000.

8. The binder according to claim 1, characterized in that, The isocyanate is one or more of diphenylmethane diisocyanate and polyphenylmethane polyisocyanate.

9. The binder according to claim 1, characterized in that, The stabilizer is one or more of benzoyl chloride, adipoyl chloride, 3,5 - dimethylbenzoyl chloride, phosphoric acid, and oleic acid.

10. A method for preparing the binder according to any one of claims 1 - 9, comprising: (1), The polyester polyol B and the isocyanate react in the presence of an auxiliary agent at a certain temperature for a period of time to synthesize an NCO - terminated prepolymer; (2), Add the polyether polyol A to the prepolymer and continue the reaction to obtain a further reacted prepolymer; (3), Add the stabilizer to the system and mix evenly to obtain the binder.

11. The method according to claim 10, wherein, In step (1), the reaction temperature is 65 - 75 °C and the reaction time is 1 - 1.5 hours; in step (2), the reaction temperature is 75 - 85 °C and the reaction time is 3 - 4 hours.

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