Process for preparing foamed polymer-modified bitumen compositions
The invention relates to a process for preparing foamed polymer-modified bitumen compositions and to the use thereof for the production of asphalt. The invention also relates to foamed polymer-modified bitumen compositions obtainable by this process. Furthermore, the invention relates to a process for producing an asphalt composition and to the use thereof in road applications. The process for the preparation of the foamed polymer-modified bitumen composition comprises the following steps: i) Heating and pressurizing a bitumen to obtain a hot flowing bitumen stream, ii) Injecting under pressure an aqueous polymer dispersion into the hot flowing bitumen stream obtained in step i), to obtain a pressurized flowing mixed stream of the bitumen and the aqueous polymer dispersion; iii) Expanding the flowing mixed stream, in particular to atmospheric pressure, such that the water contained in the aqueous polymer dispersion vaporizes and foams the mixed stream to obtain a foamed polymer-modified bitumen.
1 . A process for the preparation of a foamed polymer-modified bitumen composition comprising the steps:
i) heating and pressurizing a bitumen to obtain a hot flowing bitumen stream;
ii) injecting under pressure an aqueous polymer dispersion into the hot flowing bitumen stream obtained in step i), to obtain a pressurized hot flowing mixed stream of the bitumen and the aqueous polymer dispersion;
iii) expanding the flowing mixed stream, such that at least a majority of the water contained in the aqueous polymer dispersion vaporizes and foams the mixed stream to obtain a foamed polymer-modified bitumen;
wherein a vulcanizing agent is injected into the flowing bitumen stream concomitantly with the aqueous polymer dispersion.
2 . The process according to claim 1 , where the amount of aqueous polymer dispersion, which is injected into the flowing bitumen stream, is such that the amount of water in the pressurized flowing mixed stream is in the range from 0.5 to 8.0% by weight, based on the total weight of the bitumen.
3 . The process according to claim 1 , where the amount of aqueous polymer dispersion injected into the flowing bitumen is such that the resulting amount of polymer of the polymer dispersion in the flowing mixed stream is in the range from 0.5 to 7.0% by weight, based on the total weight of the bitumen, results.
4 . The process according to claim 1 , wherein the aqueous polymer dispersion is an aqueous dispersion of butadiene-styrene copolymer.
5 . The process according to claim 4 , wherein the butadiene-styrene copolymer, the weight ratio of styrene to butadiene is in the range from 20:80 to 80:20.
6 . The process according to claim 1 , wherein the water, which is introduced into the flowing bitumen stream by injecting the aqueous polymer dispersion contributes at least 20% to the total amount of water contained in the flowing mixed bitumen stream prior to the expansion of step iii).
7 . The process according to claim 1 , where in step i) the bitumen is heated to a temperature of at least 105° C.
8 . The process according to claim 1 , where in step i) the bitumen is pressurized to a pressure of at least 1 bar above the atmospheric pressure.
9 . The process according to claim 1 , wherein the polymer dispersion is injected into the flowing bitumen in a mixing chamber to obtain the pressurized flowing mixed stream, which is discharged from the mixing chamber through an orifice and thereby expanded.
10 . The process according to claim 1 , wherein the step ii) is performed without dynamic mixing.
11 . The process according to claim 1 , wherein the aqueous polymer dispersion is injected into the flowing bitumen stream at an angle of >90°, with respect to the flow direction of the flowing bitumen stream.
12 . The process according to claim 1 , where the amount of aqueous polymer dispersion, which is injected into the flowing bitumen stream, is such that the amount of water in the pressurized flowing mixed stream is in the range from 1.0 to 5.0% by weight, based on the total weight of the bitumen.
13 . The process according to claim 1 , where the amount of aqueous polymer dispersion injected into the flowing bitumen is such that the resulting amount of polymer of the polymer dispersion in the flowing mixed stream is in the range from 1.0 to 5.0% by weight, based on the total weight of the bitumen, results.
14 . The process according to claim 1 , where in step i) the bitumen is heated to a temperature in the range from above 110 to 230° C.
15 . The process according to claim 1 , wherein in step iii) the flowing mixed stream is expanded to atmospheric pressure.