Polyurethane rubber as well as preparation method and application thereof

Abstract

The invention discloses polyurethane rubber as well as a preparation method and application thereof, and belongs to the field of road engineering materials. The polyurethane rubber is prepared from the following components in parts by weight: 4 to 6 parts of polyether polyurethane adhesive, 90 to 96 parts of aggregate, 2 to 6 parts of mineral powder, 5 to 25 parts of rubber particles and 0.3 to 1.5 parts of calcium hydroxide, and the aggregate comprises coarse aggregate A with the particle size of 9.50 to 13.20 mm, coarse aggregate B with the particle size of 4.75 to 9.50 mm, coarse aggregate C with the particle size of 2.36 to 4.75 mm and fine aggregate with the particle size of less than 2.36 mm. The polyurethane rubber provided by the invention can achieve the effects of excellent noise reduction performance and excellent mechanical durability.

Description

TECHNICAL FIELD

[0001] The present application relates to road engineering materials, in particular to a polyurethane rubber and a preparation method and application thereof. BACKGROUND

[0002] Although asphalt pavement is widely used due to its convenience in construction and comfort in driving, it still has some common defects. On the one hand, the base layer of asphalt pavement has insufficient strength, and the flowability of asphalt mixture increases at high temperature, which leads to permanent deformation of the pavement under repeated rolling of vehicles. On the other hand, the traditional asphalt or concrete pavement has limited performance in reducing traffic noise.

[0003] Polyurethane is considered to be used in pavement materials due to its good elasticity and sound absorption performance as a high polymer material. The construction speed of polyurethane material is fast, and the setting time is short. In addition, the temperature required for polyurethane mixing is much lower than that of asphalt, which greatly reduces energy consumption. Moreover, the mechanical properties of polyurethane are better than those of asphalt, which can reduce energy consumption and material waste by reducing the frequency of pavement maintenance and reconstruction, achieve energy saving and emission reduction, and meet the requirements of sustainable development. However, the existing noise reduction pavement still needs to be improved in mechanical durability. SUMMARY

[0004] The purpose of the present application is to provide a polyurethane rubber with excellent noise reduction performance and excellent mechanical durability.

[0005] Another purpose of the present application is to provide a preparation method of the above-mentioned polyurethane rubber.

[0006] The third purpose of the present application is to provide an application of the above-mentioned polyurethane rubber.

[0007] Technical solution: The polyurethane rubber according to the present application comprises, by weight fraction, 4-6 parts of polyether polyurethane adhesive, 90-96 parts of aggregate, 2-6 parts of mineral powder, 5-25 parts of rubber particles, and 0.3-1.5 parts of calcium hydroxide. The aggregate comprises coarse aggregate A with a particle size of 9.50-13.20 mm, coarse aggregate B with a particle size of 4.75-9.50 mm, coarse aggregate C with a particle size of 2.36-4.75 mm, and fine aggregate with a particle size of <2.36 mm.

[0008] The preparation method of the polyurethane rubber according to the present application comprises the following steps:

[0009] (1) mixing coarse aggregate A, coarse aggregate B, coarse aggregate C, and fine aggregate and then standing to obtain a first mixture;

[0010] (2) pouring the polyether polyurethane adhesive into the first mixture, mixing and then standing to obtain a second mixture;

[0011] (3) Pouring rubber particles, calcium hydroxide and mineral powder into the second mixture, mixing, and standing to obtain polyurethane rubber.

[0012] Preferably, the mixing temperature in steps (1), (2) and (3) is room temperature.

[0013] Preferably, the mixing time in step (1) is 70-100s, and the standing time is 20-40s.

[0014] Preferably, the mixing time in step (2) is 70-100s, and the standing time is 10-30s.

[0015] Preferably, the mixing time in step (3) is 70-100s, and the standing time is 20-40s.

[0016] Preferably, the amount of calcium hydroxide is 1 part, and the amount of polyether polyurethane adhesive is 6 parts.

[0017] The polyurethane rubber of the present application is used as a pavement material, comprising the following steps: pouring the polyurethane rubber into a mold, compacting, treating with a milling cutter, and standing to obtain a polyurethane pavement material.

[0018] Preferably, the standing time is not less than 2h.

[0019] The present application aims to provide a polyurethane rubber with added calcium hydroxide to improve its mechanical strength. Rubber particles have elastic cushioning properties, but when used alone, they are prone to particle shedding due to stress concentration because the interfacial adhesion strength between the rubber particles and the aggregate and adhesive is weak. Calcium hydroxide powder can fill the micro voids between the rubber particles and the polyurethane adhesive, enhance the mechanical interlocking force of the two-phase interface through physical adsorption, and reduce the slip of the rubber particles under load. The calcium carbonate crystals generated by the reaction of calcium hydroxide and polyurethane foaming are uniformly distributed on the surface of the rubber particles and around them, forming rigid support points, which moderately increase the overall hardness of the composite system without significantly reducing the elasticity of the polyurethane rubber, thereby enhancing the pavement's resistance to deformation and wear resistance.

[0020] In addition, calcium hydroxide can absorb moisture from the environment and trace amounts of moisture left over from the polyurethane reaction, reducing the hydrolysis of the -NCO group by water; it can also capture CO2 that may be left over from the polyurethane foaming reaction, preventing material degradation caused by the reaction of CO2 with the urethane bond in polyurethane. Calcium hydroxide is a basic substance that can maintain the weak alkalinity of the microenvironment of the mixture, inhibit the erosion of acidic impurities (such as sulfides in automobile exhaust) on the polyurethane molecular chain, slow down the rate of material oxidation and aging, and indirectly improve the wear resistance of the pavement.

[0021] Beneficial effects: compared with the prior art, the present application has the following significant advantages: (1) by adding calcium hydroxide, the polyurethane rubber material prepared by the present application not only has noise reduction function, but also has strong wear resistance and crack resistance, the dynamic stability positively correlated with wear resistance is up to 33268 times / mm, which is increased by 12.5% compared with the material without adding calcium hydroxide, and the low temperature damage strain positively correlated with crack resistance is up to 12164 με, which is increased by 27.8% compared with the material without adding calcium hydroxide; (2) the polyurethane material has fast construction speed and short setting time, and the polyurethane adhesive can be mixed at room temperature, which greatly reduces energy consumption; (3) when the polyurethane rubber of the present application is used as pavement material, the mechanical properties of the pavement, including tensile strength, compressive strength, wear resistance and crack resistance, are effectively improved, thereby prolonging the service life of the pavement, realizing the double improvement of noise reduction and pavement strength and durability, and being able to resist deformation under the coupling action of load and high temperature; (4) in the present application, the polyurethane adhesive synergistically works with calcium hydroxide and rubber particles, and when the polyurethane rubber is used in pavement material, the bonding strength of the pavement can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 SEM image of the polyurethane rubber prepared in Example 1. DETAILED DESCRIPTION

[0023] The technical solutions of the present application will be further described below in combination with examples.

[0024] The polyether type polyurethane adhesive used in the present application is produced by Hebei Langfang Quanzhen Chemical Industry Development Co., Ltd., and the aggregate and mineral powder are provided by Jiangsu Maodi Group Co., Ltd.

[0025] Example 1

[0026] The polyurethane rubber described in the present application comprises, by weight fraction, 6 parts of polyether type polyurethane adhesive, 33 parts of coarse aggregate A (particle size 9.50-13.20 mm), 30 parts of coarse aggregate B (particle size 4.75-9.50 mm), 6 parts of coarse aggregate C (particle size 2.36-4.75 mm), 27 parts of fine aggregate (particle size <2.36 mm), 4 parts of mineral powder, 10 parts of styrene-butadiene rubber (SBR) particles and 0.3 parts of solid calcium hydroxide.

[0027] The main chemical components of coarse aggregate A are silicon dioxide (45%-55%), aluminum oxide (15%-20%) and iron oxide (8%-12%), and also contain a small amount of calcium oxide (5%-8%) and magnesium oxide (3%-5%).

[0028] The main chemical components of coarse aggregate B are silicon dioxide (65%-75%) and aluminum oxide (12%-18%), and also contain a small amount of iron oxide (1%-3%) and potassium oxide (3%-5%).

[0029] The coarse aggregate C mainly comprises calcium carbonate (content ≥ 90%), and further comprises a small amount of silicon dioxide (3%-5%) and aluminum oxide (1%-2%).

[0030] The fine aggregate mainly comprises silicon dioxide (≥ 85%), and further comprises a small amount of aluminum oxide (3%-5%) and iron oxide (1%-2%).

[0031] The mineral powder mainly comprises calcium carbonate (≥ 90%), and the free calcium oxide content is ≤ 1.0%.

[0032] The styrene-butadiene rubber is a synthetic rubber copolymerized by butadiene and styrene, and has good elasticity, wear resistance and aging resistance, and the Shore hardness is between 60-70A, the tensile strength is ≥ 18 MPa, and the elongation at break is ≥ 400%, which can be well matched with the polyurethane rubber system, and the elasticity and impact resistance of the material are improved. Mainly derived from waste styrene-butadiene rubber products recycling, such as waste styrene-butadiene rubber tires, sealing elements and the like. After the waste products are treated by crushing, screening, impurity removal and the like, particles meeting the particle size requirements are processed.

[0033] The preparation method of the polyurethane rubber comprises the following steps:

[0034] (1) 33 parts of coarse aggregate A, 30 parts of coarse aggregate B, 6 parts of coarse aggregate C and 27 parts of fine aggregate are mixed at room temperature for 90s, and then statically placed for 30s to obtain a first mixture.

[0035] (2) 6 parts of polyether type polyurethane adhesive are poured into the first mixture, mixed for 90s, and then statically placed for 10s to obtain a second mixture.

[0036] (3) 10 parts of rubber particles, 0.3 parts of solid calcium hydroxide and 4 parts of mineral powder are sequentially poured into the second mixture, mixed for 90s, and then statically placed for 30s to obtain the polyurethane rubber.

[0037] The application of the polyurethane rubber as a road surface material comprises the following steps:

[0038] The prepared polyurethane rubber is poured into a forming mold for compaction, and then treated with a milling cutter to make the road surface pores uniformly distributed and enhance the anti-skid performance, and the polyurethane road surface material can be obtained after being statically placed for 2h.

[0039] The polyurethane rubber prepared in the embodiment is subjected to scanning electron microscope test, and the microstructure is as shown in Figure 1The figure shows that the surface of the material presents irregular rough texture, and there are obvious concave-convex and pore structure. This porous and rough structure can increase the surface area of the material to some extent, which is beneficial to the interaction between interfaces. Calcium hydroxide is dispersed therein, and granular, rod-shaped and other morphological substances can be observed, which are combined with the polyurethane matrix and can fill part of the pores. On the one hand, the pores can buffer stress through deformation when stressed; on the other hand, calcium hydroxide as an inorganic phase forms a composite structure with the organic polyurethane matrix, and the interface is well combined, which can transmit stress and hinder crack propagation. The rod-shaped substances are closely combined with the matrix, which can play a "pinning" role to enhance the toughness and strength of the material.

[0040] Example 2

[0041] The same as between the present example and Example 1 will not be repeated, and the difference lies in that the addition amount of solid calcium hydroxide is 1 part.

[0042] Example 3

[0043] The same as between the present example and Example 1 will not be repeated, and the difference lies in that the addition amount of solid calcium hydroxide is 1.5 parts.

[0044] Example 4

[0045] The same as between the present example and Example 1 will not be repeated, and the difference lies in that the addition amount of rubber particles is 0 parts.

[0046] Example 5

[0047] The same as between the present example and Example 1 will not be repeated, and the difference lies in that the addition amount of polyether polyurethane adhesive is 4 parts, and the addition amount of rubber particles is 25 parts.

[0048] Example 6

[0049] The same as between the present example and Example 1 will not be repeated, and the difference lies in that the addition amount of polyether polyurethane adhesive is 5 parts, the addition amount of rubber particles is 5 parts, and the addition amount of solid calcium hydroxide is 0.5 parts.

[0050] Comparative Example 1

[0051] The same as between the present example and Example 1 will not be repeated, and the difference lies in that the addition amount of solid calcium hydroxide is 0 parts.

[0052] Comparative Example 2

[0053] The same as between the present example and Example 1 will not be repeated, and the difference lies in that the addition amount of solid calcium hydroxide is 2 parts.

[0054] The road surface materials obtained from each example and the comparative example were tested according to the Highway Engineering Asphalt and Asphalt Mixture Test Regulation (JTG E20-2011) and the Measurement of Sound Absorption Coefficient and Acoustic Impedance in Acoustic Impedance Tube Part 1: Standing Wave Ratio Method (GB / T 18696.1-2004), and the test items included dynamic stability, low-temperature failure strain, low-temperature bending tensile strength, low-temperature bending stiffness modulus, immersion residual stability, freeze-thaw splitting strength ratio, sound absorption coefficient, and A-weighted sound pressure level. In order to intuitively represent the differences and performance characterization results in each example and the comparative example, the experimental data are listed in Tables 1 and 2.

[0055] Table 1 Road performance of each sample

[0056]

[0057] Table 2 Sound absorption and noise reduction performance of each sample

[0058]

[0059] According to the data of Examples 1-3 and Comparative Examples 1-2 in the table, adding an appropriate amount of calcium hydroxide can improve the high-temperature stability, low-temperature crack resistance, strength, water stability, and sound absorption performance of the polyurethane road surface material, and excessive addition will result in a decrease in performance. This is because the curing of the polyether polyurethane adhesive depends on the crosslinking reaction of isocyanate groups and hydroxyl groups, and calcium hydroxide as an alkaline catalyst can provide OH ions to accelerate the reaction. An appropriate amount of calcium hydroxide can control the reaction rate to a moderate state, allowing the adhesive molecules to crosslink uniformly and form a complete and dense three-dimensional network structure. This structure can enhance the overall load-bearing capacity of the polyurethane road surface material, resulting in an increase in dynamic stability. At the same time, the moderate reaction avoids local overheating or premature curing, ensuring that the adhesive can fully wrap the aggregate and rubber particles and reducing interface defects to support low-temperature performance. At the same time, calcium hydroxide reacts with the silicon hydroxyl groups on the surface of basalt aggregate to form a chemical bond Ca-O-Si, bridging inorganic aggregate and organic adhesive, reducing water penetration at the interface; promoting chemical adsorption of the adhesive and rubber particles, preventing rubber particles from falling off in water or freeze-thaw cycles. The addition amount of calcium hydroxide in Examples 1-3 is within the preferred range, which can effectively improve the performance of the polyurethane road surface material, and the dynamic stability, low-temperature failure strain, low-temperature bending tensile strength, and low-temperature bending stiffness modulus are significantly better than those of Comparative Example 1 without the addition of calcium hydroxide. In Comparative Example 2, the addition amount of calcium hydroxide is too large, and the improvement effect on the performance of the polyurethane road surface material is not obvious, which indicates that the addition amount of calcium hydroxide increases to a certain extent, and the performance of the polyurethane road surface material reaches a plateau, and the excessive addition of calcium hydroxide will increase the cost and the performance-price ratio is not high. Therefore, the addition amount of calcium hydroxide is too low, which will result in poor performance of the prepared polyurethane road surface material, and the addition amount is too high, which will increase the cost and the performance-price ratio is low.

[0060] According to the data of Example 1, Example 4-6 in the table, the appropriate amount of rubber particles can balance the high-temperature stability and low-temperature toughness of the polyurethane pavement material, and excessive amount will lead to the decline of high-temperature stability and durability. This is because the rubber particles as an elastic organic filler, through the dual effects of elastic buffer and skeleton coordination in the polyurethane pavement material to achieve performance balance. The rubber particles have high elasticity and low modulus characteristics, and when added in appropriate amount, they can be uniformly dispersed in the skeleton of the polyurethane pavement material. In low-temperature environment, when the polyurethane pavement material is subjected to shrinkage stress, the rubber particles absorb stress through elastic deformation to avoid brittle fracture caused by stress concentration, showing that the low-temperature failure strain increases with the increase of the amount of rubber particles. At the same time, the rubber particles reduce the overall rigidity of the polyurethane pavement material, and the low-temperature bending stiffness modulus decreases with the increase of the amount of rubber particles. The appropriate amount of rubber particles can form a composite structure of "rigid skeleton-elastic filling" with aggregate and polyurethane adhesive: coarse aggregate constitutes the main bearing skeleton, rubber particles fill the gap between the skeleton, and are fully wrapped and bonded by polyurethane adhesive, forming a continuous stress system of "aggregate-adhesive-rubber". At high temperature, the elasticity of the rubber particles can inhibit the relative sliding between the aggregate particles, while the adhesion of the polyurethane adhesive limits the excessive deformation of the polyurethane pavement material, and the two can synergistically improve the anti-rutting ability, showing that the dynamic stability increases first and then decreases with the increase of the amount of rubber particles. In Example 1, the amount of rubber particles added is within the preferred range, which can effectively improve the performance of the polyurethane pavement material, improve the low-temperature toughness through elastic buffer, and enhance the high-temperature stability in coordination with the skeleton. In Example 4, without the addition of rubber particles, the sound absorption and noise reduction performance of the polyurethane pavement material will be deteriorated, the low-temperature toughness will be insufficient, and the high-temperature stability will be decreased, which cannot meet the design goal of durable noise reduction. In Example 5, the amount of rubber particles added is too high, the interfacial adhesion between the rubber particles and the rubber particles and the aggregate is insufficient, and the relative sliding and plastic deformation between the particles under high temperature due to vehicle load will lead to a sharp decline in anti-rutting ability. Excessive rubber particles occupy the space of aggregate, weaken the skeleton bearing effect of coarse aggregate, and make the overall structure more prone to compression deformation under high temperature. At the same time, too much elastomer makes the overall rigidity of the polyurethane pavement material insufficient.

[0061] In summary, the amount of calcium hydroxide and the amount of rubber particles have a significant impact on the performance of the polyurethane pavement material. Too low amount of calcium hydroxide and rubber particles will lead to poor results, and too high amount of calcium hydroxide and rubber particles will not necessarily significantly improve the performance of the polyurethane pavement material, but may increase the cost. Appropriate addition of calcium hydroxide and rubber particles can ensure the noise reduction performance of the material while providing the best durability and higher cost performance.

Claims

1. A polyurethane rubber, characterized in that: Calculated by weight, it includes 4-6 parts of polyether polyurethane adhesive, 90-96 parts of aggregate, 2-6 parts of mineral powder, 5-25 parts of rubber particles, and 0.3-1.5 parts of calcium hydroxide. The aggregate includes coarse aggregate A with a particle size of 9.50-13.20 mm, coarse aggregate B with a particle size of 4.75-9.50 mm, coarse aggregate C with a particle size of 2.36-4.75 mm, and fine aggregate with a particle size of less than 2.36 mm.

2. A method for preparing the polyurethane rubber according to claim 1, characterized in that: The following steps are involved: (1) Coarse aggregate A, coarse aggregate B, coarse aggregate C, and fine aggregate are mixed and allowed to stand to obtain a first mixture; (2) pouring a polyether polyurethane adhesive into the first mixture, stirring and then allowing to stand to obtain a second mixture; (3) Pour rubber particles, calcium hydroxide and mineral powder into the second mixture, mix and let stand to obtain polyurethane rubber.

3. The preparation method according to claim 2, characterized in that The mixing temperature in steps (1), (2) and (3) is room temperature.

4. The preparation method according to claim 2, characterized in that The mixing time in step (1) is 70-100s, and the standing time is 20-40s.

5. The preparation method according to claim 2, characterized in that The mixing time in step (2) is 70-100s, and the standing time is 10-30s.

6. The preparation method according to claim 2, characterized in that The mixing time in step (3) is 70-100s, and the standing time is 20-40s.

7. The preparation method according to claim 2, characterized in that The amount of calcium hydroxide added is 1 part, and the amount of polyether polyurethane adhesive added is 6 parts.

8. Use of the polyurethane rubber according to claim 1 as a pavement material.

9. The use according to claim 8, characterized in that The following steps are involved: The polyurethane rubber is poured into a mold and compacted, processed with a milling cutter and then allowed to stand to obtain the polyurethane pavement material.

10. The use according to claim 8, characterized in that The standing time is not less than 2 hours.

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