Compositions: coating or plastic – Coating or plastic compositions – Bituminous material or tarry residue
Patent
1993-11-26
1995-04-11
Bell, Mark L.
Compositions: coating or plastic
Coating or plastic compositions
Bituminous material or tarry residue
1062731, 106278, 1062843, 10628403, 2523115, C08L 9500
Patent
active
054054397
DESCRIPTION:
BRIEF SUMMARY
This invention relates to bitumen emulsions, especially emulsions having a relatively high viscosity, and to a method for preparing such emulsions.
Bitumen emulsions are used, for example, in road surfacing and repairing. They have advantages over conventional bitumen compositions in that they can be applied at lower temperatures by spraying or other coating techniques. After being applied to the road surface the emulsion breaks and the water present in the emulsion evaporates leaving a coating of bitumen. Thus emulsions provide few environmental problems and can be used on site without the danger of exposing the roadworkers to burns and toxic fumes.
The viscosity of a conventional bitumen emulsion depends largely on the amount of bitumen present. Typically the viscosity is relatively low, ranging from 30 cSt at 60 weight percent bitumen to 400 cSt at 70 weight percent bitumen. Low viscosity emulsions have the disadvantage that, after they have been sprayed onto the road surface, the emulsion tends to flow towards the side of the road due to the camber of the road surface, and the bitumen layer has an uneven thickness across the width of the road.
U.S. Pat. No. 3,728,278 gives examples of bitumen emulsions which consist of 67 or 69% bitumen (asphalt), 0.30% amine emulsifying agent, 0.19% hydrochloric acid, 0.05% calcium chloride, with water making up the remainder of the compositions, the percentage being by weight based on the total weight of the emulsion. The emulsions have a Saybolt Furol Viscosity of 55 seconds (120 cSt), i.e. a typical viscosity for a bitumen emulsion.
The viscosity of bitumen emulsion can be increased by increasing the bitumen content of the emulsion, but this has the disadvantage of reducing the stability of the emulsion. This instability can be countered by adding more emulsifying agent but this then results in an increase in the time taken for the emulsion to break after it has been applied to the road surface. Instead of increasing the bitumen content, high molecular weight compounds can be added to the emulsion, such as high molecular weight water soluble polymers. However these have the disadvantage that they are expensive.
The present invention provides, in one aspect, a bitumen emulsion having a viscosity of at least 200 centiStokes at 25.degree. C. comprising by weight based on the total weight of the emulsion: potassium, magnesium, calcium and aluminium; and
The emulsion according to the invention has the advantage that it has a relatively high viscosity without having an increased proportion of bitumen and without the addition of high molecular weight viscosifying agents. Thus it retains the beneficial properties of lower viscosity emulsions, such as stability and fast breaking, is relatively inexpensive to manufacture, and has the advantage that when the emulsion is applied to a road surface the high viscosity limits the flow of the emulsion towards the sides of the road, and provides a bitumen layer of good uniform thickness.
The bitumen employed in the emulsion may be any well-known commercially available bitumen (also known as asphalt) provided it has a penetration at 25.degree. C. of 20 to 500 according to ASTM D946-74. Preferably the bitumen has a penetration of 100 to 300, more preferably 150 to 250; and a Ring and Ball softening point of 35.degree. to 100.degree. C., more preferably 35.degree. to 60.degree. C. The preferred amount of bitumen contained in the emulsion is 64 to 75%, with 66 to 70% being especially preferred. The mean particle diameter of the bitumen in the prepared emulsion is generally in the range of 0.5 to 10 microns, usually 2 to 7 microns.
The emulsifying agent employed is typically a cationic emulsifying agent. Cationic emulsifying agents are well known for use in bitumen emulsions, and suitable examples include amine propane alkyldiamine and modified alkyl diamines. Preferably the amount of emulsifier used is 0.04 to 1.0%, more preferably 0.05 to 0.5%.
The inorganic acid employed is preferably hydrochloric acid. The preferred amount used in 0.
REFERENCES:
patent: 3695152 (1972-10-01), Graf
patent: 3728278 (1973-04-01), Tramelli
patent: 4370170 (1983-01-01), Tolonen et al.
patent: 4496474 (1985-01-01), Reck
Patent Abstracts of Japan, vol. 12, No. 2223, C507, abstract of JP 63-17960, published Jan. 25, 1988 (KAO Corp).
Bell Mark L.
Esso Societe Anonyme Francaise
Marcheschi Michael
Takemoto James H.
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