A modified waste rubber and its preparation method and cement-based composite material

Abstract

The present invention provides a modified waste rubber and its preparation method and a cement-based composite material, belonging to the technical field of building materials. By microwave heating, the surface of the waste rubber is softened, and then active mineral fine powder is attached, which can improve the adhesion at the contact interface between the rubber particles and the cement material, and solve the compatibility problem between the rubber particles and the cement substrate. With little influence on the bulk density, thermal conductivity and fluidity of the cement material, the mechanical properties of the cement material are improved; at the same time, the problem of waste rubber treatment can be solved, which is more environmentally friendly. The results of the examples show that when the modified waste rubber prepared by the present invention is added to the cement material, the bulk density of the material is 1.73 - 1.87 g / cm<supgt;3< / supgt;, the spread is 185 - 200 mm, the thermal conductivity is 0.47 - 0.52 W / (m·k), the flexural strength is 9.76 - 10.33 MPa, and the compressive strength is 29.90 - 32.41 MPa.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly relates to a modified waste rubber, a preparation method thereof, and a cement-based composite material. Background Art

[0002] With the rapid development of industries such as the automotive industry in China, the amount of rubber consumed in China every year is huge, and a large amount of waste rubber is generated accordingly. The traditional treatment methods mainly include incineration and landfill, but they will cause serious environmental pollution. Therefore, the recycling and reuse of rubber have received increasing attention.

[0003] Currently, the main recycling and reuse method is to modify waste rubber and then reuse it. Common surface modification methods include chemical oxidation methods, such as using acidified NaClO solution for oxidation treatment to increase the number of surface groups of rubber; graft modification methods, such as using polar monomer maleic anhydride to graft-modify the surface of waste rubber powder with benzoyl peroxide as an initiator under non-oxygen isolation conditions to graft hydrophilic groups; or radiation modification methods. However, the above methods require the use of organic solvents and the process is relatively complex with high energy consumption. The conventional mechanical modification method is to crush waste rubber and then add it to plastic or other matrix materials, but this method will cause a significant reduction in the performance of the matrix.

[0004] Therefore, how to simplify the modification process of waste rubber and at the same time make the composite material prepared from the modified waste rubber have excellent performance has become a difficult problem in the prior art. Summary of the Invention

[0005] The purpose of the present invention is to provide a modified waste rubber, a preparation method thereof, and a cement-based composite material. The preparation method provided by the present invention is simple, and the prepared modified waste rubber can improve the mechanical properties of the cement base material with less influence on the bulk density, thermal conductivity, and fluidity of the cement base material when added to the cement base material.

[0006] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a preparation method of a modified waste rubber, comprising the following steps:

[0008] (1) Microwave heat the waste rubber particles to obtain treated rubber;

[0009] (2) Cover the treated rubber obtained in the step (1) with active mineral fine powder to obtain modified waste rubber.

[0010] Preferably, the particle size of the waste rubber particles in the step (1) is 0.5 - 20 mm.

[0011] Preferably, in the step (1), the power of microwave heating is 2.8 kW to 3.5 kW, and the frequency of microwave heating is 2 GHz to 2.5 GHz.

[0012] Preferably, in the step (1), the time of microwave heating is 30 min to 60 min.

[0013] Preferably, in the step (2), the active mineral fine powder includes one or more of silica fume, mineral powder, steel slag powder, fly ash, active glass powder and bauxite.

[0014] Preferably, in the step (2), the particle size of the active mineral fine powder is 50 nm to 2 μm.

[0015] Preferably, in the step (2), the mass ratio of the active mineral fine powder to the waste rubber particles in the step (1) is (0.5 - 1):1.

[0016] The present invention provides the modified waste rubber prepared by the preparation method described in the above technical solution.

[0017] The present invention also provides a cement-based composite material, which includes the modified waste rubber, cement, water and admixture described in the above technical solution.

[0018] Preferably, the mass ratio of the modified waste rubber, cement, water and admixture is (20 - 80):(20 - 45):(20 - 80):(0.1 - 0.5).

[0019] The present invention provides a preparation method of modified waste rubber, which includes the following steps: (1) microwave heating waste rubber particles to obtain treated rubber; (2) covering the treated rubber obtained in the step (1) with active mineral fine powder to obtain modified waste rubber. The present invention uses microwave heating to soften the surface of waste rubber, and then wraps active mineral fine powder, which can improve the adhesion of the rubber particles to the contact interface of cement materials, improve the compatibility between the rubber particles and cement substrates, and improve the mechanical properties of cement materials with little influence on the bulk density, thermal conductivity and fluidity of cement materials; at the same time, it can solve the problem of waste rubber treatment and is more environmentally friendly. The results of the examples show that when the modified waste rubber prepared by the present invention is added to cement materials, the bulk density of the materials is 1.87 g / cm 3 , the spread is 200 mm, the thermal conductivity is 0.47 W / (m·k), the flexural strength is 10.33 MPa, the compressive strength is 32.41 MPa, compared with the cement material added with unmodified waste rubber (the bulk density is 1.80 g / cm 3, compared with those having a bulk density of 195 mm, a thermal conductivity of 0.78 W / (m·k), a flexural strength of 8.06 MPa, and a compressive strength of 24.32 MPa), the bulk density, thermal conductivity, and spread of the material change little, but the flexural strength and compressive strength are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 FIG. 1 is a schematic structural view of a cement-based composite material prepared from modified waste rubber according to the present invention, wherein: 1 is a waste rubber particle, 2 is an active mineral fine powder, 3 is the contact surface between the active mineral fine powder and the cement substrate, and 4 is the contact surface between the waste rubber particle and the active mineral fine powder. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention provides a method for preparing modified waste rubber, comprising the following steps:

[0022] (1) Microwave heating of waste rubber particles to obtain treated rubber;

[0023] (2) Covering the treated rubber obtained in step (1) with active mineral fine powder to obtain modified waste rubber.

[0024] Unless otherwise specified, the present invention does not have special limitations on the sources of the various components, and commercially available products well-known to those skilled in the art can be used.

[0025] The present invention subjects waste rubber particles to microwave heating to obtain treated rubber.

[0026] The present invention does not have special limitations on the source of the waste rubber particles, and waste rubber well-known to those skilled in the art can be used. In the present invention, the waste rubber particles preferably include one or more of natural rubber, styrene-butadiene rubber, silicone rubber, cis-1,4-polybutadiene rubber, and isoprene rubber.

[0027] In the present invention, the apparent density of the waste rubber is preferably 950 - 1600 kg / m 3 , more preferably 1000 - 1500 kg / m 3 , most preferably 1100 - 1300 kg / m 3 .

[0028] In the present invention, the particle size of the waste rubber particles is preferably 0.5 - 20 mm, more preferably 1 - 15 mm, and most preferably 5 - 10 mm. By limiting the particle size of the waste rubber particles within the above range, the waste rubber particles can have a larger specific surface area, wrap more active mineral fine powder, be more compatible with the cement substrate, and further improve the cement performance.

[0029] When the particle size of the waste rubber particles is not within the above range, the present invention preferably crushes the waste rubber particles. The present invention has no special limitation on the operation of the crushing, and adopts the crushing technical solutions well-known to those skilled in the art, as long as the particle size of the crushed waste rubber particles is within the above range.

[0030] In the present invention, the waste rubber particles are preferably cleaned and dried before use.

[0031] The present invention has no special limitation on the operations of the cleaning and drying, and the technical solutions of cleaning and drying well-known to those skilled in the art can be adopted.

[0032] In the present invention, the power of the microwave heating is preferably 2.8 kW to 3.5 kW, more preferably 3.0 kW to 3.5 kW; the frequency of the microwave heating is preferably 2 GHz to 2.5 GHz, more preferably 2.2 GHz to 2.3 GHz; the time of the microwave heating is preferably 30 min to 60 min, more preferably 45 min to 55 min. The present invention limits the power, frequency and time of the microwave heating within the above ranges, which can fully soften the surface of the waste rubber particles to adhere the active mineral fine powder.

[0033] After obtaining the treated rubber, the present invention covers the treated rubber with the active mineral fine powder to obtain the modified waste rubber.

[0034] In the present invention, the active mineral fine powder preferably includes one or more of silica fume, ore powder, steel slag powder, fly ash, active glass powder and bauxite. In the present invention, the active mineral fine powder can improve the adhesion at the contact interface between the rubber particles and the cement material, improve the compatibility problem between the rubber particles and the cement base material, and further improve the performance of the cement material.

[0035] In the present invention, the particle size of the active mineral fine powder is preferably 50 nm to 2 μm, more preferably 100 nm to 1.5 μm, and most preferably 0.5 to 1 μm. The present invention limits the particle size of the active mineral fine powder within the above ranges, which can make the active mineral fine powder have a larger specific surface area, contact more fully with the cement base material, further improve the compatibility between the rubber particles and the cement base material, and improve the performance of the cement material.

[0036] In the present invention, the mass ratio of the active mineral fine powder to the waste rubber particles is preferably (0.5 to 1):1, more preferably (0.6 to 0.9):1, and most preferably (0.7 to 0.8):1. The present invention limits the mass ratio of the active mineral fine powder to the waste rubber particles within the above ranges, which can make the modified waste rubber contain more active mineral fine powder, improve the compatibility with the cement base material, and further improve the performance of the cement material.

[0037] The present invention has no special limitation on the covering technical solution, and the well-known covering technical solution in the art can be adopted. In the present invention, microwave heating softens the waste rubber particles, and during the covering process, the softened waste rubber particles adhere to the active mineral micropowder.

[0038] The present invention uses microwave heating to soften the waste rubber particles, then wraps them with active mineral micropowder, and controls process parameters such as the particle size of the waste rubber particles, the power and time of microwave heating, the particle size and dosage of the active mineral micropowder, etc., which can improve the compatibility between the modified waste rubber particles and the cement matrix, and further improve the performance of the cement material.

[0039] The present invention provides the modified waste rubber prepared by the preparation method described in the above technical solution.

[0040] The modified waste rubber provided by the present invention has good compatibility with the cement matrix, and adding it to the cement matrix can improve the mechanical properties of the cement material.

[0041] The present invention also provides a cement-based composite material, which includes the modified waste rubber, cement, water and admixture described in the above technical solution.

[0042] In the present invention, the cement preferably includes one or more of portland cement, aluminate cement, sulphoaluminate cement, and ferroaluminate cement.

[0043] In the present invention, the admixture preferably includes one or more of water-reducing agent, air-entraining agent, early-strength agent and expansive agent. The present invention has no special limitation on the types of the water-reducing agent, air-entraining agent, early-strength agent and expansive agent, and the well-known water-reducing agent, air-entraining agent, early-strength agent and expansive agent in the art can be adopted.

[0044] In the present invention, the mass ratio of the modified waste rubber, cement, water and admixture is preferably (20-80):(20-45):(20-80):(0.1-0.5), and more preferably (40-60):(30-40):(40-60):(0.2-0.3). The present invention limits the mass ratio of the modified waste rubber, cement, water and admixture within the above range, which can further improve the mechanical properties of the cement material with less influence on the cement bulk density and spread.

[0045] The present invention has no special limitation on the preparation method of the cement, and the well-known preparation method of the cement in the art can be adopted.

[0046] The structural schematic diagram of the cement-based composite material prepared by the modified waste rubber of the present invention is preferably as Figure 1As shown in the figure, where: 1 is waste rubber particles, 2 is active mineral fine powder, 3 is the contact surface between the active mineral fine powder and the cement substrate, and 4 is the contact surface between the waste rubber particles and the active mineral fine powder.

[0047] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0048] Example 1

[0049] (1) Take waste rubber particles with a particle size of 1 - 5 mm (the waste rubber particles are waste natural rubber, and the apparent density is 1600 kg / m 3 ) After cleaning and drying, then perform microwave heating with a microwave power of 3.0 kW, a frequency of 2 GHz, and a time of 35 min to obtain treated rubber;

[0050] (2) Uniformly mix the obtained treated rubber and silica fume (the mass ratio of silica fume to waste rubber particles is 0.6:1, the particle size of silica fume is 0.1 - 0.3 μm, the density is 5 g / cm 3 , and the activity index ≥ 105%) to cover its surface with silica fume to obtain modified waste rubber.

[0051] Example 2

[0052] (1) Take waste rubber particles with a particle size of 2 - 6 mm (the waste rubber particles are waste silicone rubber, and the apparent density is 1300 kg / m 3 ) After cleaning and drying, then perform microwave heating with a microwave power of 3.3 kW, a frequency of 2.3 GHz, and a time of 40 min to obtain treated rubber;

[0053] (2) Uniformly mix the obtained treated rubber and fly ash (the mass ratio of fly ash to waste rubber particles is 0.5:1, and the particle size of fly ash is 0.1 - 0.3 μm) to cover its surface with fly ash to obtain modified waste rubber.

[0054] Example 3

[0055] (1) Take waste rubber particles with a particle size of 0.5 - 6 mm (the waste rubber particles are waste styrene - butadiene rubber, and the apparent density is 1450 kg / m 3 ) After cleaning and drying, then perform microwave heating with a microwave power of 3.5 kW, a frequency of 2.5 GHz, and a time of 55 min to obtain treated rubber;

[0056] (2) The obtained treated rubber and active glass powder (the mass ratio of active glass powder to waste rubber particles is 0.8:1, and the particle size of the active glass powder is 0.1 - 0.3 μm) are uniformly mixed so that the surface is covered with the active glass powder, and the modified waste rubber is obtained.

[0057] Example 4

[0058] The modified waste rubbers of Examples 1 - 3 are respectively mixed with portland cement, water, and high - efficiency polycarboxylate water - reducing agent according to a mass ratio of 55:40:20:0.2, uniformly stirred for 5 min, then poured into a mold of 40 mm × 40 mm × 160 mm. After demolding 24 h later, test blocks are obtained. The obtained test blocks are placed in a curing chamber at a temperature of 20 ± 2 °C and a relative humidity of 90 ± 3%, and after curing for 28 d (days), relevant performance tests are carried out on the test blocks. The results are listed in Table 1. Among them, the control specimen is a specimen containing unmodified waste rubber, and the unmodified waste rubber, portland cement, water, and high - efficiency polycarboxylate water - reducing agent are mixed according to a mass ratio of 50:40:20:0.2.

[0059] Table 1 Performance of cement test blocks prepared from the modified waste rubbers of Examples 1 - 3

[0060]

[0061] As can be seen from Table 1, compared with the cement material added with unmodified waste rubber, the bulk density, thermal conductivity, and spread of the cement material added with the modified waste rubber of the present invention change little, but the flexural strength and compressive strength are greatly improved. After surface - modifying the waste rubber of the present invention and compounding it with the cement - based material, the strength of the material can be significantly improved with little influence on the bulk density, thermal conductivity, and spread.

[0062] The above - mentioned are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of modified waste rubber, comprising the following steps: (1) Microwave heating is carried out on waste rubber particles to obtain treated rubber; in the step (1), the power of microwave heating is 2.8 kW to 3.5 kW, the frequency of microwave heating is 2 GHz to 2.5 GHz; the time of microwave heating in the step (1) is 30 min to 60 min; the particle size of the waste rubber particles in the step (1) is 0.5 to 20 mm; (2) The treated rubber obtained in the step (1) is covered with active mineral fine powder to obtain modified waste rubber; in the step (2), the active mineral fine powder includes one or more of silica fume, ore powder, steel slag powder, fly ash, active glass powder and bauxite; the particle size of the active mineral fine powder in the step (2) is 50 nm to 2 μm; the mass ratio of the active mineral fine powder in the step (2) to the waste rubber particles in the step (1) is (0.5 to 1):1.

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