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Elastomer-modified bituminous compositions

a technology of elastomer and bituminous composition, which is applied in the direction of building components, building insulation, construction, etc., can solve the problems of low mw elastomers that do not offer significant improvement in properties, phase separation, and bituminous compositions

Inactive Publication Date: 2003-02-13
LIANG ZHI ZHONG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The process enables the use of high molecular weight elastomers at high loadings, improving the performance and stability of bituminous compositions while maintaining workable viscosity, suitable for diverse industrial applications like paving and roofing, with a cost-effective balance.

Problems solved by technology

However, low MW elastomers do not offer significantly improved properties when compared with those resulting from the use of high molecular weight elastomers as bitumen modifiers, unless the low MW rubber chains are expanded and strengthened using a cross-linking agent, such as elemental sulfur.
Unfortunately, compositions prepared from the high MW elastomers, in most cases, give rise to compatibility problems for the elastomer in the bitumen, resulting in phase separation when the bituminous compositions are stored.
However, the processes described in the prior art result in severe limitations on the proportions of sulfur and / or elastomer which can be reacted in the bitumen before the composition forms an un-processible gel.
However, these additives are so expensive that they have not, in general, been used commercially.
However with these higher MW elastomers, poor storage stability and relatively high viscosity can result in difficult material handling (processing, pumping, polymer separation and reblending), even at high temperatures.
However, these compositions show sub-optimal performance, high cost or both.
However, all examples given in WO 97 / 45488 are limited to sulfur loading which do not exceed 4% by wt, based on the total amount of elastomers, otherwise the viscosity is too high to permit workability of the asphalt-polymer mix.
However, to achieve this result represents a challenging combination of requirements.
Usually, even at a fixed level of sulfur, as the concentration of the elastomer is increased, the viscosity of the asphalt mixture increases rapidly due to gellation and phase separation of the asphalt and elastomer may occur because of excessive inter-polymer cross-linking.
Therefore, it is generally considered difficult to incorporate high MW elastomer into bitumen at higher loadings, especially for the situation in which the proportion of sulfur is also increased proportional to the increased load of elastomer.
In addition, the limitation on the load level of elastomer which can be vulcanized into asphalt has restricted the application of the reactive process in important industrial applications, such as roofing, crack filler and so on.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example a

[0045] Example A

[0046] This Examples describes the results of a first set of experiments using bitumen AC-20-1 from AASTO Materials Reference Laboratory (Grade: AC-20, MRL asphalt code: ABF).

[0047] In this first set of experiments, the elastomer used was a styrene-butadiene-styrene tri-block copolymer (SBS), a commercially-available thermoplastic elastomer with the trade-name Enichem-161B. The elastomer has an average molecular weight of 278,300 and a styrene / butadiene ratio of 30:70.

[0048] In such experiments, the polymer and sulfur, when used, were dispersed into the bitumen with a high shear mixer (Brinkman Polytron Mixer) at a temperature of 180.degree. C. Certain properties of the resulting compositions are listed, using ASTM Standard procedures.

[0049] The results obtained in this first set of experiments is shown in Table I below. There are four experiments reported in Table 1, labelled Control, Comparative Example 1, Comparative Example 2 and Inventive Example 1, following Pr...

example b

[0059] Example B

[0060] This Example describes the results of a second set of experiments using bitumen AC-20-2 from the Huntway Refinery, California, USA. This bitumen grade is a typical AC-20 grade from this region. In this second set of experiments, the elastomer employed was the same as that used in Example A.

[0061] The results obtained in this second set of experiments are shown in Table 2. There are eight experiments reported in Table 2, labelled Control, Comparative Example 1, Comparative Example 2, Inventive Example 2, Inventive Example 3, Inventive Example 4, Inventive Example 5 and Inventive Example 6.

[0062] The Control Example in Table II indicated that the SBS used was also incompatible with the bitumen (AC-20-2). Polymer separation can be seen in the Table.

[0063] The first two Comparative Examples (Sample Nos. 1 and 2) were prepared using the conventional procedure in attempts to produce homogeneous compositions of modified bitumen with SBS elastomer at load levels of 4%...

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Abstract

Polymer modified bituminous compositions which are stable against phase separation are provided at greater levels of incorporation of elastomeric polymer having a conjugated diene structure, such as styrene-butadiene rubbers, and / or cross-linking agent, specifically sulfur, by incremental addition of elastomeric polymer and / or cross-linking agent into the bitumen at elevated temperatures of about 150° to about 220° C.

Description

[0001] The present invention is concerned with the preparation of bituminous compositions with high performance characteristics, particularly compositions containing bitumen and high molecular weight elastomer(s). The bituminous compositions provided herein have numerous commercial uses, including road paving, roofing, asphalt emulsions and crack fillers.BACKGROUND TO THE INVENTION[0002] Bituminous compositions for various applications are known to contain elastomers, such as natural rubber (NR), styrene-butadiene rubber latex (SBR), Neoprene latex and styrene-butadiene block copolymers (SB). The SB copolymers having a conjugated diene structure are most commonly used to provide improved properties in specific applications. These elastomers improve the mechanical properties of the bitumen and hence their incorporation is desirable.[0003] In general, low molecular weight (MW) elastomers, those having a MW of less than about 70,000, are readily dispersed in bitumen to form a compatibl...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C08J3/24C08J3/20C08L21/00C08L95/00
CPCC08L95/00C08L53/00C08L2666/08
Inventor LIANG, ZHI-ZHONG
Owner LIANG ZHI ZHONG