Polybetaines as asphalt emulsifiers

Details Polybetaines as asphalt emulsifiers Polybetaines as asphalt emulsifiers

2001-03-20

2003-04-01

Lovering, Richard D. (Department: 1712)

Compositions: coating or plastic

Coating or plastic compositions

Bituminous material or tarry residue

C106S283000, C516S043000, C516S045000, C516S914000, C516S916000

Reexamination Certificate

active

06540822

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to the use of polybetaines as asphalt emulsifiers. More particularly, the invention concerns an improved process for stabilizing an asphalt in water emulsion using certain polybetaines as an asphalt emulsifier.
BACKGROUND OF THE INVENTION
Asphalt in water emulsions are used for road construction and repair, as well as in the construction industry as coatings and sealers. The asphalt properties are obtained after the emulsions set or cure, when the droplets of asphalt coalesce and adhere to the substrate and water is removed.
The rate of this setting process depends on the reactivity of the emulsion and the reactivity of the substrate. Emulsions are classified as rapid, medium and slow-setting types depending on their reactivity. Slow-setting emulsions find use in applications, such as cold mix, where the emulsion is mixed with aggregate and the mixture is used to pave a roadway.
Emulsions can be classified into cationic or anionic types depending on the charge on the asphalt droplets. Cationic emulsions are used for siliceous aggregates, like quartz, since such aggregates have negatively charged surfaces. The cured film from cationic emulsions generally adheres much better to siliceous aggregates than does the cured film from anionic emulsions. Generally, different emulsifiers are used for cationic emulsions than are used for anionic emulsions.
Nonionic emulsifiers, such as ethoxylated nonylphenols, can be used as part of an emulsifier or alone in both cationic and anionic slow-setting emulsions. However, at use levels comparable to the inventive emulsifier, the anionic and cationic slow-setting emulsions of ethoxylated nonylphenols are deficient in quality. Additionally, films of asphalt derived from such emulsions tend to strip off the aggregate when soaked in water.
The asphalt residues (i.e. after curing of the emulsion) from slow-setting asphalt emulsions, especially slow-setting anionic emulsions, show poor adhesion to aggregates such as quartzite. The result is poor durability of road materials prepared using these emulsions. Moreover it is necessary to use different chemicals to produce anionic and cationic slow setting asphalt emulsions.
The asphalt residues from slow-setting emulsions prepared from the polybetaine emulsifiers of the invention, however, show good adhesion and have particularly better adhesion than the residues derived from slow-setting cationic, anionic or nonionic emulsions prepared with the commonly-used nonylphenolethoxylate emulsifiers.
SUMMARY OF THE INVENTION
The present invention,generally relates to a method of emulsifying asphalt using a novel asphalt emulsifier, an asphalt emulsion containing the novel asphalt emulsifier, and a cold mix of the asphalt emulsion containing the novel asphalt emulsifier. The method emulsifies a mixture of asphalt and water by adding an emulsifying effective amount of a novel asphalt emulsifier of at least one polyamine polybetaine.
The invention is especially useful in slow setting emulsions, since lower use levels are required when using the inventive emulsifier and the emulsifier can be used for either anionic or cationic slow setting emulsions depending on whether an acid or alkaline water phase is used. Both the cationic and anionic slow setting asphalt emulsions are of good quality and meet the requirements of slow setting grades at low use levels. The cured asphalt residue from emulsions made with the inventive emulsifier adhere better to aggregates than the asphalt residue from emulsions prepared with nonionic nonylphenolethoxylate emulsifiers.
Further, the emulsions of the present invention can be used for cold mix, where they exhibit advantages compared with a conventional cationic mixing grade emulsifier. Additionally, the inventive asphalt emulsifiers are compatible with both cationic and anionic co-emulsifiers, especially when combined with co-emulsifiers conventionally used for medium and rapid-setting emulsions. It is, thus, very economical to use the inventive asphalt emulsifiers, since lower use levels are required and it is only necessary to stock a single emulsifier for both anionic and cationic emulsions and for slow setting emulsions.
These and other objects of the invention are readily apparent from the following disclosure.
DETAILED DESCRIPTION OF THE INVENTION
The present invention utilizes one or more polyamine polybetaines, preferably dibetaines derived from N-alkyl-1,3-propylene diamines as asphalt emulsifiers or co-emulsifiers. The emulsions formed using the inventive process meet the requirements for slow setting emulsions specified by the American Society for Testing and Materials (ASTM) and others, as demonstrated by the examples herein.
The asphalt emulsifiers of the present invention can be represented by the following formula I. It is understood that when representing the chemical structure of the (poly)betaines in the present specification that such structures implicitly include protonated or partially protonated acid salt(s) of the betaines formed when the betaine is acidified, as well as unprotonated forms.
wherein R is a C
8
-C
24
hydrocarbon radical, preferably a C
8
-C
22
alkyl, alkenyl or mixture thereof, or a group of the formula R
4
—O—CH
2
CH
2
CH
2
, where R
4
is a C
6
-C
20
hydrocarbon radical, preferably a C
8
-C
18
alkyl or alkenyl group; R
1
, R
2
and R
3
are, independently, a C
1
-C
6
alkyl or alkanol, preferably methyl, ethyl, ethanol, propanol, polyethoxyethanol, carboxyethyl or carboxymethyl in any combination, and more preferably methyl, ethanol, or polyethoxyethanol in any combination; x is an integer equal to or greater than 1; and y is an integer equal to or greater than 1, with y+1 indicating the number of quaternized nitrogen atoms in the polyamine; and z is an integer equal or greater than 1.
It is also preferable that R is a C
8
-C
18
hydrocarbon radical, including C
18
unsaturated alkyl chains or their mixtures. Additionally, it is preferred that R is derived from natural fats and oils, such as tallow, rapeseed(canola), soya, tall oil, etc., giving an alkyl chain range of C
12
-C
18
, including unsaturated alkyl chains, and, more preferably, R is tallow alkyl or hydrogenated tallow alkyl. It is also preferable that R
1
, R
2
, and R
3
are, independently, methyl, ethan-2-ol, propan-2-ol, polyoxyethylene, and are, more preferably, methyl or ethan-2-ol. Preferably, x=1-6, more preferably, x=2 or 3 and, even more preferably, x=3.
The novel asphalt emulsifier of the present invention can be prepared by various methods within the knowledge of one of ordinary skill in the art. For example, they can preferably be derived from a diaminopropane such as N,N′,N′trimethyl-N-tallow-1,3-propylene diamine reacted with sodium monochloroacetate (SMCA). Other polybetaines useful in the context of the present invention include but are not limited to:
dibetaines prepared from N,N′,N′tis(2-hydroxyethyl)-N-tallow-1,3 diaminopropane.
polybetaines derived from tallow polytertiaryamines such as R—[N(CH
3
)CH
2
CH
2
CH
2
]
a
—N(CH
2
)
2
where a is an integer greater than 1.
dibetaines or polybetaines prepared from other monohalocarboxylic acid salts such as X[CH
2
]
b
COONa where X=Cl, Br or I and b is an integer equal to or greater than 1.
betaines by other routes such as alkylation of carboxymethylated polyamines.
betaines prepared from ether polyamines.
compounds having more than one carboxyalkyl group per nitrogen atom, and the like.
Preferred polyamine polybetaines include but are not limited to
Amines, N,N,N′-trimethyl-N′-tallowalkyl trimethylenedi-, N,N′-dicarboxymethyl, hydroxides, inner salt.
R=tallow, R
1
=R
2
=R
3
=methyl, x=3, y=1, z=1.
Amines, N,N,N′-triethanol-N′-tallowalkyl trimethylenedi-, N,N′-dicarboxymethyl, hydroxides, inner salt.
R=tallow, R
1
=R
2
=R
3
=CH
2
CH
2
OH, x=3, y=1, z&eq

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