Asphalt compositions

Details Asphalt compositions Asphalt compositions

2001-10-03

2004-07-06

Lipman, Bernard (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S069000, C524S070000, C524S071000

Reexamination Certificate

active

06759453

ABSTRACT:

INTRODUCTION
Asphalt is used in a variety of applications, but by far the major use is in road construction and maintenance. Although it is a versatile material, the physical properties of asphalt may limit its usefulness in this and other applications. For quite a number of years researchers have demonstrated that the addition of certain polymers~3 to about 8 wt. % or more can enhance the properties of asphalt. These include:
Increased toughness and tenacity
Increased tack, elasticity and improved impact resistance
Resistance to deformation at low temperatures, and
Resistance to deformation at high temperatures.
While a number of thermoplastics can confer the above properties to asphalt to a surprisingly high degree, there remains a serious problem, which the polymer generally does not address. This involves the interfacial surface energy between the aggregate, about 95 wt. %, and the bitumen, about 5 wt. %. Usually, a polymer is added to the above asphalt composite from about 5 to 25 wt. % based on the bitumen. The aggregate is highly hydrophilic while most polymers tend to be very hydrophobic. The result is delamination of the materials, particularly during freeze-thaw cycles, high temperatures and the exposure to salt, oil, gasoline, water etc.
This invention will describe methods of circumventing this very serious problem. The methods will be economically viable based on the utility of inexpensive raw materials and high production rate processes. The disclosure is also versatile in that it can be used with most of the current polyolefins presently being used to modify asphalt.
Other benefits are also inherent with this invention, such as the ease of dispersing the polymers with the asphalt. This is a particularly difficult and costly problem for polyolefins, most times requiring special high energy mixing equipment. The added expense can negate using this technology due to budgetary problems confronted by many states.
BEHAVIOR OF POLYMER MODIFIED ASPHALT
At low temperatures asphalt can turn brittle and crack: at high temperatures, it can soften when under the weight of heavy trucks passing over it. A road may be 80-100° F. hotter than it is in winter; and for every 100° F. rise in temperature, asphalt is a million times softer. Though it never actually runs off the road, it does creep into ridges and ruts that make driving dangerous. An asphalt road would hold up better with more built-in sturdiness.
Polymers work by creating a kind of support matrix within the asphalt. A seminal paper by JEW et al (J. Appl. Polym. Sci, 31,2685-2704 (1986)) confirmed that 8 wt. % polyethylene in a bitumen mixture possessed:
Increased flexural strength
Increased flexural modulus
Increased elongation
Increased fracture energy
These investigators concluded that a polyethylene in hot-mix paving materials can extend service temperature range at both high and low temperatures, thereby simultaneously reducing both pavement distortion (rutting) and low temperature cracking so that pavement lifetimes can be more than doubled.
These investigators also suggest the use of Kraton G (tri-block polymer) to control the stability of the mixture, particle size and compatibility of the dispersed polyethylene phase. However, this approach is not economically feasible due to the high weight percent of the polymers used and the costs for processing the asphalt-polymer blend.
FIELD OF THE INVENTION
The invention relates to polymers, which have been functionalized so as to contain one or more functional groups selected from the group consisting of amino, imino, imido and imidazloyl groups as well as processes for preparing such functionalized polymers. The functionalized polymer, when mixed with bitumen and aggregate provides for an excellent paving composition with improved physical properties and enhanced anti-stripping properties.
Many commodity polymers upon modification using the technology of this invention can be utilized. These include plastomers and elastomers whose compositions consist of polyolefins, styrene-alpha olefins, and polydienes.
Specifically, modified polyethylene, polypropylene, polyethylene-polypropylene copolymers or terpolymers, styrene-ethylene interpolymers, chlorosulfonated polyethylene, or polyisoprene. These are the preferred modified polymers.
This invention teaches the reaction of polyamines or polyether amines with the before described preferred polymers as being high desired polymer asphalt modifiers. There are basically two chemical reactions in which this invention modifies the desired polymers with polyamines. These are classified as amidation and amination.
Amidation involves the reaction of a carboxylic acid or an anhydride—with a polyamine, while amination involves either a grafting of a polyamine to the polymer backbone or by reacting a polyamine with a carbonyl functionality in the polymer or with a tertiary or secondary carbon atom in the polymer macromolecule. U.S. Pat. Nos. 4,068,056; 4,068,057; and 4,068,058 describe amination of polyolefins.
This invention also teaches methods in preparing the modified polymers, and subsequent blending with the asphalt. The compositions of value as polymer asphalt modifiers can be prepared by chemical solution reactions, intensive mixing devices, or in-situ in the presence of hot asphalt. Obviously, where appropriate the in-situ process offers considerable costs advantage over the other methods. Nevertheless, extrusion, single or twin screw, is also an economical viable process. Chemical solution modified is not preferred due to the considerable costs associated with this procedure.
DETAILED DESCRIPTION OF THE INVENTION
The first embodiment of the invention relates to polymers, which have been functionalized so as to contain one or more functional groups selected from the group consisting of amino, amido, imino, imido and imidazloyl groups as well as processes for preparing such functionalized polymers. Typically, the polymer prior to functionalization will have a number average molecular weight of 5,000 to about 500,000.
Subsequent to functionalization, the functionalized polymer will have a nitrogen content of about 0.05 to about 4.50 wt. %, based on the weight of the functionalized polymer. Suitable polymers for functionalization include polyolefins, elastomers, thermoplastic elastomers, and styrene-alpha olefin interpolymers.
Typically, the polyolefin will be a homopolymer of a C
2
-C
8
olefin, a copolymer of two or more C
2
-C
8
olefins; a copolymer of one or more C
2
-C
8
olefins and a polymerizable monomer or a graft copolymer of one or more C
2
-C
8
olefins and a polymerizable monomer. Suitable C
2
-C
8
olefins include ethylene; propylene; a mixture of ethylene and propylene; butylenes; isoprene; and butadiene. Preferably the homopolymer is a polyethylene or a polypropylene. Suitable polyethylenes include low-density polyethylene, high-density polyethylene, linear low-density polyethylene, linear high-density polyethylene and metallocene polyethylene. Suitable polypropylenes include isotactic, syndiotactic and/or atactic polypropylene.
Preferably, the copolymer of two or more C
2
-C
8
olefins comprises an amorphous or elastomeric copolymer of ethylene and propylene wherein the molar ratio of ethylene to propylene is the range of about 0.2:1 to about 3:1.
In the case of the polymer being a copolymer of one or more C
2
-C
8
olefins and a polymerizable monomer, a suitable copolymer comprises an ethylene-propylene-diene monomer terpolymer, wherein the diene monomer is selected from the group consisting of 1,4-hexadiene; dicyclopentadiene; and ethylidene norbomene.
Suitably, the polymerizable monomer is selected from the group consisting of styrene C
3
-C
15
(meth) acrylates, vinyl acetates, vinyl carboxylic acids and vinyl carboxylic acid anhydrides. Preferably, the C
2
-C
8
olefins are selected from the group consisting of ethylene, propylene, a mixture of ethylene and propylene, and butylenes, and the polymerizable monomer comprising styrene.
In the case of the polymer being a graft polymer, suitable graft polymers i

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