WO2017058002A1

WO2017058002A1 - Method for preparing coagulated latex and cuplump rubber-based modified bitumen

Info

Publication number: WO2017058002A1
Application number: PCT/MY2016/000038
Authority: WO
Inventors: Mohd Akbar Bin MD SAID; Zairossani Bin MOHD NOR; Nazirah Bt AHMAD; Mazlina Bt MUSTAFA KAMAL; Azhar Bin AHMAD; Muhammad Umar Bin ZULKEFLI; Mahirah Bt MOHD IDRIS; Kamarularifin Bin HADITHON; Mohd Khairulniza MANSOR; Suhawati Bt IBRAHIM; Ruhida ABD RAHIM
Original assignee: Lembaga Getah Malaysia
Priority date: 2015-09-30
Filing date: 2016-06-30
Publication date: 2017-04-06
Also published as: MY175944A

Abstract

The present invention provides a method for preparing coagulated latex and cuplump rubber-based modified bitumen, the method includes (a) preparing and mixing a cuplump natural rubber and/or synthetic rubber in an internal mixer prior mixing with an additional rubber chemical for compounding of filler, activator and accelerator to form a compound, (b) adding a predetermined amount of bitumen into the internal mixer as temperature of the compound reaches at least 60°C, (c) adding a further predetermined amount of bitumen in the internal mixer as soon as temperature of the compound reaches at least 80°C and dumping the compound as soon as temperature of the compound reaches at least 90°C, wherein compound includes 100phr natural rubber, 0-100phr bitumen, 0-50phr of a carbon material such as carbon black, carbon nanotube or graphene and 0-50phr stearic acid.

Description

METHOD FOR PREPARING COAGULATED LATEX AND CUPLUMP RUBBER-BASED

MODIFIED BITUMEN

FIELD OF INVENTION

The present invention relates generally to a method for preparing coagulated latex and cuplump rubber-based modified bitumen.

BACKGROUND OF INVENTION

Bitumen has been used in the construction of asphalt pavements for more than a century. As a viscoelastic material, bitumen plays a prominent role in determining many aspects of road performance. For example, a bituminous mixture needs to be flexible enough at low service temperatures to prevent pavement cracking and to be stiff enough at high service temperatures to prevent rutting. However, because of continuously increasing traffic volumes and axle loads, bituminous mixtures containing conventional bitumen would not always perform as expected. Consequently, for certain applications, properties of bitumen need to be improved with regard to performance-related properties, such as resistance to permanent deformation, low temperature cracking, load-associated fatigue and wear, stripping and ageing.

The first way of achieving better asphalt pavement is to use a better arrangement of aggregates, binder and void contents. When all these parameters are adequately selected, the second step is to use a better binder with higher performance than neat bitumen. Such an enhanced binder is often a Polymer Modified Bitumen (PMB) obtained by the incorporation of a polymer in the bitumen using mechanical mixing and/or chemical reaction. The properties of PMBs are dependent on polymer characteristics and content, bitumen nature, as well as the blending process. Despite the large number of polymeric products, mostly two classes of polymers are suitable and typically used in bitumen modification, elastomers and plastomers. Styrene-butadiene-styrene (SBS) is the most commonly known thermoplastic elastomer that can improve the rheological properties of bitumen. Furthermore, SBS increases binder elasticity at high temperatures and improves flexibility at low temperatures. This improvement led to increase the resistance to asphalt rutting at high temperatures, and decrease cracking at low temperatures.

In addition, other types of additives have also been used as modifiers, such as styrene isoprene styrene (SIS), styrene ethylene butadiene styrene (SEBS), ethylene-propylene- diene-terpolymer (EPDM), isobutene-isoprene-copolymer (ΠΡ), crumb-rubber, polybutadiene (PBD), polyisoprene and natural rubber (NR). Study showed that 6% by weight of Ribbed Smoked Sheet (RSS) in asphalt developed, low penetration, softening point, penetration index, ductility, torsional recovery and high toughness.

In some cases, the rubbers have been used in a vulcanized state, e.g., crumb-rubber, but are difficult to disperse throughout the bitumen. Ineffective dispersion requires high temperatures and long mixing times and can yield a heterogeneous binder, with the rubber acting mainly as flexible filler. However, crumb rubber is a combination of mainly natural rubber (improves the elasticity of the compound), carbon black and synthetic rubber (both of which materials improve the thermal stability properties). In addition, crumb-rubber has been found to improve rutting resistance and to decrease reflective cracking. However, it is found that natural rubber shows better reactivity compared to crumb rubber. The reacted particles become tacky and improve adhesion properties. The cohesion between aggregates, thus holding the aggregate together, is one advantage of using natural rubber to modify bitumen. However scarce information can be obtained on the cup lump modified bitumen. FR 783041 A discloses a method for preparing asphalt mixes or asphalt bitumens with finely divided rubber. Accordingly, this invention provides a process for preparing mixtures of asphalt or asphalt bitumen with finely pulverized rubber; the method being characterized in that the rubber is being suspended in a finely divided liquid rubber and this rubber suspension is mixed with asphalts or asphaltic bitumen in the molten state. The liquid used for the suspension being completely miscible with asphalt or asphalt bitumen used, and the liquid does not dissolve rubber, or dissolving slowly enough for the suspension of the rubber was prepared and thoroughly mixed with asphalt. CN 103086651 A discloses a bituminous mixture. Accordingly, this invention relates to a bituminous mixture containing natural rubber. As the natural rubber with high tensile strength and low elongation is mixed in bituminous concrete, the original performance of the bituminous concrete can be changed, so that the bituminous mixture has the characteristics of high temperature stability, low temperature crack resistance, good flexibility, long service life and the like.

WO 2012169891 Al discloses a bituminous binder composition comprising bitumen, an elastomer, and a cross-linkable vegetable oil, wherein the bituminous binder composition has a dynamic viscosity at 80°C of about 0.5Pa.s to about 12Pa.s according to test method NEN-EN 13302-2010. The invention also provides a process for repairing the surface of an asphalt road construction, wherein the bituminous binder composition is employed. The process is in particular suitable for repairing the surface of very open asphalt.

FR 2567447 Al discloses a process for compounding a bitumen-rubber mixture, wherein bitumen-rubber mixture is held at a temperature very close to 150°C for compounding, storing and regeneration of bitumen-rubber mixtures used for road surfacing. US 2921105 A discloses a process for rubberizing bitumen by interblending rubber latex with molten bitumen. Accordingly, this invention provides a process for the manufacture of rubberized bitumen such as, for example, asphalt, tar and the like, and more particularly to such processes as are designed to manufacture of rubberized bitumen by the interblending of an aqueous latex into a bitumen. The process comprising introducing the latex into a confined body of the molten bitumen moving under pressure through an enclosed zone, the latex being introduced into the molten bitumen at a point within the molten body where the temperature of the bitumen is sufficiently high to evaporate the water of the latex and moving the resultant mixture as a confined body beyond the point of latex introduction for a time period sufficient to obtain vaporization of the water out of the latex to form steam and to obtain dispersion of the rubber throughout the bitumen and discharging the mixture from 1 the enclosed zone for release of the steam.

US 3803066 A discloses modifying bitumens wherein it relates to a process for the production of a modified bitumen binding agent, and to the product obtained thereby. More especially, the invention relates to a process for producing a rubber modified bitumen binding agent. Accordingly, the process for preparation of a rubber-modified bitumen comprising the steps of: a) blending a rubber and bitumen by intimately admixing a powder or latex of a natural or a synthetic rubber, in an amount giving up a certain percentage by weight of rubber based on weight of bitumen, either into an aqueous bitumen emulsion which emulsion is thereafter broken and water removed, or into bitumen which is at a temperature from about 145°C to about 185°C; b) adjusting the temperature of the bitumen-rubber mix to within the range of about 125°C to about 160°C; c) intimately blending into the mix an amount of sulphur such that the weight ratio of sulphur to rubber is between about 0.3 and about 0.9; d] adding a catalytic quantity of a free-radical vulcanisation-accelerator; and e) maintaining the mix within the temperature range of about 125°C to about 160°C to effect co-vulcanisation of the rubber and the bitumen. In view of this and other inadequacies, it would be advantageous to provide a method for preparing coagulated latex and cuplump rubber based modified bitumen which is cost- effective, sustainable benefits on trafficked road and is able to quantify the functional properties of asphalt pavements.

SUMMARY OF THE INVENTION

Therefore, the present invention a method for preparing coagulated latex and cuplump rubber-based modified bitumen, the method includes (a) preparing and mixing a cuplump natural rubber and/or synthetic rubber in an internal mixer prior mixing with an additional rubber chemical for compounding of filler, activator and accelerator to form a compound, (b] adding a predetermined amount of bitumen into the internal mixer as temperature of the compound reaches at least 60°C, (c) adding a further predetermined amount of bitumen in the internal mixer as soon as temperature of the compound reaches at least 80°C and (d) dumping the compound as soon as temperature of the compound reaches at least 90°C wherein compound includes lOOphr natural and/or synthetic rubber, 0-lOOphr bitumen, 0- 50phr of a filler material such as carbon black, carbon nanotube or graphene and 0-50phr activator and accelerator.

The present invention consists of several novel features and a combination of parts hereinafter fully described and illustrated in the accompanying description and drawings, it being understood that various changes in the details may be made without departing from the scope of the invention or sacrificing any of the advantages of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a method for preparing coagulated latex and cuplump rubber based modified bitumen. Hereinafter, this specification will describe the present invention according to the preferred embodiments or exemplary of the present invention. However, it is to be understood that limiting the description to the preferred embodiments or exemplary of the invention is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications and equivalents without departing from the scope of the appended claims.

The present invention generally provides rubberised bitumen, a binder in hot mix asphalt that results from the proper addition of rubber to hot bitumen and then left in a heated state to react. It should be noted that the present invention is adapted to provide many advantages and benefits, including reduced long-term road maintenance and expense, significant noise reductions, improved traction and reduced accident rates in wet road conditions. Accordingly, results showed that the addition of cuplump rubber based modified bitumen increased viscosity, stiffness and has potential to increase rutting resistance. Generally, the present invention provides a method for preparing coagulated latex and cuplump rubber-based modified bitumen, the method includes:

(a) preparing and mixing a cuplump natural rubber and/or synthetic rubber in an internal mixer prior mixing with an additional rubber chemical for compounding of filler, activator, accelerator, anti oxidant, and anti ozonant agent to form a compound;

(b) adding a predetermined amount of bitumen into the internal mixer as temperature of the compound reaches at least 60°C; (c) adding a further predetermined amount of bitumen in the internal mixer as soon as temperature of the compound reaches at least 80°C; and

(d) dumping the compound as soon as temperature of the compound reaches at least 90°C

wherein compound includes lOOphr natural rubber, 0-lOOphr bitumen, 0-50phr of a carbon material such as carbon black, carbon nanotube or graphene and 0-50phr stearic acid.

Preferably, in step (a), the cuplump natural rubber and/or synthetic rubber is based with Mooney viscosity of 30 to 100 ML (1+4) and is being mixed in the internal mixer for 5-10 minutes with rotor speed of 15-30 rpm.

Preferably, in step (a), the compound is being mixed in the internal mixer for 15-45 minutes.

Preferably, in step (b), a rotor speed is increased to 30-50 rpm immediately after the bitumen is added into the mixer in order to maintain the high temperature of 60-150 °C.

Preferably, the mixing parameter includes 0.78-1.0 fill factor, temperature of 50°C-150°C and rotor speed of 20-50 rpm.

Preferably, 5%-20% of the compound is incubated in bitumen for 24 hours at 130-160°C to obtain cuplump modified binder (CMB) with and without additive such as anti-stripping agent.

Preferably, the average Mooney viscosity of the coagulated latex and cup lump rubber- based modified bitumen is 6-20ML (1+4). The invention will now be described in detail based on the compound formulation, mixing condition and cycle is shown in the following tables. It should be noted that the average of the final compound Mooney viscosity was about 6-20ML (1+4). Example

This study was conducted to present a laboratory evaluation of base bitumen and cup lump modified bitumen in terms of bitumen properties, premix properties and performance test. In future, work on modified bitumen will cover on blend of cup lump with other rubber too. In order to determine whether it is cost-effective to use cup lump modified binder (CMB) and to assess its sustainable benefits on trafficked road, a test road was built in Stesen Penyelidikan of Rubber Research Institute of Malaysia (RRIM) in ota Tinggi, Johor, Malaysia in December 2014. The objective of constructing such a test road is also to validate if binder tests can quantify the functional properties of asphalt pavements. The test road is being monitored continuously by Malaysian Rubber Board and IKRAM QA Services Sdn. Bhd.

Preparation

Step 1: The compound was prepared and mixed in internal mixer within 15 -45 minutes. Initially cup lump natural rubber based with Mooney viscosity of 30 to 100 ML (1+4) or a blend of cup lump natural rubber and synthetic rubber such as SBR, BR, Polyurethane is mixed in internal mixer for 5 -10 minutes with rotor speed of 15-30rpm prior mixing with additional rubber chemical for compounding such as any type of filler, activator and accelerator, anti oxidant and anti ozonant agent.

Step 2: Later, half of the bitumen was added to the mixer as temperature of the mixing reached 60-150°C. Immediate after adding the bitumen, the rotor speed was increased to

30-50rpm in order to maintain high temperature. Step 3: The mixing was continued with adding another half of bitumen once the temperature achieves 80-150°C.

Step 4: The process was continued for a few minutes before dumping and reaching to 90- 150°C, as the additional of bitumen in the mixture in general would affect the mixing temperature.

The compound formulation, mixing condition and cycle is shown in Tables 1, 2 and 3 respectively. The average of the final compound Mooney viscosity was about 6-20ML ( 1+4).

Table 1: Bituminous cup lump formulation

Table 2: Bituminous cup lump formulation

Table 3: Mixing parameter

Time (s) /Temperature Material

0 Rubber

300 Stearic Acid, Carbon Black/Carbon nanotube/Graphi

60-150°C ½ Bitumen

80-150°C ½ Bitumen

90-150°C Dump

Table 4: Mixing cycle for cup lump based natural rubber bitumen 5%-20% of the compound was later incubated in bitumen for 24 hours at 130-160°C (CMB).

Result

Effect of cuplump based natural rubber in bitumen

Commercial grade of bitumen penetration grade 60/70 or 80/100 is used in the experiment. The base and the modified binder (CMB) are then tested for bitumen test, premix test and performance test.

The results are reported in table below:

Table 4: Bitumen properties of Bitumen Grade 60/70 or 80/100 bitumen and CMB

Table 5: Premix properties of Bitumen Grade 60/70 or 80/100 bitumen

and CMB according to AC14 premix design

Test Bitumen Cup Lump

Table 6: Performance properties of Bitumen Penetration Grade 60/70 or 80/100 and CMB

These results illustrate on the effect of addition of 5%-20% natural rubber, which allows improving the properties of commercial grade of Bitumen Penetration Grade 60/70 or 80/100.

It will be appreciated that study was conducted to investigate the effect of cuplump based natural rubber on the conventional properties. Based on penetration and softening point results, the mechanism of modification of CMBs seemed to entail a stiffening of the base bitumen. It should be noted that cup lump provides polymeric modification by means of a highly elastic network within the bitumen and this elastic network increases the viscosity, stiffness and elastic behavior of the CMB. In addition, based on the rutting parameters, adding cup lump decreased the rutting for the binder modified bitumen.

It is to be understood that both the set forth examples and detailed description are exemplary and explanatory only, and are not restrictive of the invention. As such, the set forth examples and detailed description, including methodology, compounds, compositions, materials, and its contents or any other parameters such as mixing parameters or factors, times, temperatures, rotor speeds or other approaches as described above should not be construed as limiting, but as the best mode contemplated by the inventor for carrying out the invention. The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the principle and scope of the invention, and all such modifications as would obvious to one skilled in the art intended to be included within the scope of following claims.

Claims

1. A method for preparing coagulated latex and cuplump rubber-based modified bitumen, the method includes:

(a) preparing and mixing a cuplump natural rubber and/or synthetic rubber in an internal mixer prior mixing with an additional rubber chemical for compounding of filler, activator and accelerator to form a compound;

(b) adding a predetermined amount of bitumen into the internal mixer as temperature of the compound reaches at least 60°C;

(c) adding a further predetermined amount of bitumen in the internal mixer as soon as temperature of the compound reaches at least 80°C; and

wherein compound includes lOOphr natural and/or synthetic rubber, 0-lOOphr bitumen, 0-50phr of a filler material such as carbon black, carbon nanotube or graphene and 0-50phr activator and accelerator.

2. The method according to Claim I, wherein in step (a), the cuplump natural rubber and/or synthetic rubber is based with Mooney viscosity of 30 to 100 ML (1+4) and is being mixed in the internal mixer for 5-10 minutes with rotor speed of 15-30 rpm.

3. The method according to Claim 1, wherein in step (a), the compound is being mixed in the internal mixer for 15-45 minutes.

4. The method according to Claim 1, wherein in step (b), a rotor speed is increased to 30-50 rpm immediately after the bitumen is added into the mixer in order to maintain the high temperature of 60-150 °C.

5. The method according to Claim 1, wherein mixing parameter includes 0.78-1.0 fill factor, temperature of 50°C -150°C and rotor speed of 20-50 rpm.

6. The method according to Claim 1, wherein 5%-20% of the compound is incubated in bitumen for at least 100°C with and without additive such as anti-stripping agent to obtain cup lump modified binder (CMB).

7. The method according to Claim 1, wherein average Mooney viscosity of the coagulated latex and cup lump rubber-based modified bitumen is 6-20ML (1+4).