MODIFIED BITUMINOUS BINDER EMULSION

Abstract

The invention relates to a process for the preparation of a bituminous binder emulsion for making layers and/or coatings for road construction and/or civil engineering, comprising mixing a dispersing aqueous phase and a bituminous binder comprising an initial bitumen in the presence of at least one emulsifying agent, and obtaining a bituminous binder emulsion comprising a final bitumen with a decreased penetration grade, wherein at least 0.5% by weight of an oxidizing agent, which is neither dioxygen nor ozone, is mixed with the dispersing aqueous phase or the bituminous binder before or during the mixing step, or is added in the mixture after said mixing step has been initiated. The invention also relates to a composition for preparing a modified emulsion and its use for making tack coats having a trackless finish.

Claims

1-14. (canceled)

15. A process for the preparation of a bituminous binder emulsion for making layers and/or coatings for road construction and/or civil engineering, comprising: a) mixing a dispersing aqueous phase and a bituminous binder comprising an initial bitumen in the presence of at least one emulsifying agent, b) obtaining a bituminous binder emulsion comprising a final bitumen, characterized in that: at least one oxidizing agent, which is neither dioxygen nor ozone, is mixed with in the dispersing aqueous phase or the bituminous binder before or during mixing step a), or is added in the mixture after mixing step a) has been initiated and before step b), and said at least one oxidizing agent is present in an amount of at least 0.5% by weight, relative to the emulsion total weight, the penetration grade of the final bitumen is decreased by at least one grade as defined in the EN-12591 standard as compared to the initial bitumen.

16. The process of claim 1, wherein the at least one oxidizing agent is a peroxide.

17. The process of claim 2, wherein said peroxide is hydrogen peroxide or a salt thereof.

18. The process of claim 1, wherein the at least one oxidizing agent is added as an aqueous solution.

19. The process of claim 1, wherein the at least one oxidizing agent is added in the dispersing aqueous phase comprising said at least one emulsifying agent, and then the dispersing aqueous phase is mixed with the bituminous binder.

20. The process of claim 1, wherein the at least one oxidizing agent is added to a bituminous binder emulsion obtained after step a), and before step b).

21. The process of claim 1, wherein the at least one oxidizing agent is added in the bituminous binder before mixing step a), and mixing step a) is initiated before the initial bitumen penetration grade has been decreased by more than one grade as defined in the EN-12591 standard.

22. The process of claim 1, wherein the at least one oxidizing agent is present in an amount ranging from 0.5 to 20% by weight, relative to the emulsion total weight.

23. The process of claim 1, wherein the bituminous binder is present in an amount ranging from 10 to 80% by weight, relative to the emulsion total weight.

24. The process of claim 1, wherein the bituminous binder contains a bitumen that represents from 25 to 100% of the bituminous binder total weight.

25. The process of claim 24, wherein the bituminous binder contains a bitumen that represents from 65 to 90% of the bituminous binder total weight.

26. The process of claim 1, wherein the emulsifying agent is present in an amount ranging from 0.05 to 5% by weight, relative to the emulsion total weight.

27. The process of claim 1, wherein the layers and/or coatings for road construction and/or civil engineering are trackless tack coats.

28. The process of claim 1, wherein the emulsion is a cationic emulsion.

29. A bituminous binder composition for making layers and/or coatings for road construction and/or civil engineering, comprising a dispersing aqueous phase, at least one emulsifying agent, a bituminous binder and at least one oxidizing agent that is neither dioxygen nor ozone.

30. A process for improving the trackless nature of a bituminous binder emulsion comprising a dispersing aqueous phase, at least one emulsifying agent and a bituminous binder, comprising the use of a use of an oxidizing agent that is neither dioxygen nor ozone.

Description

EXAMPLES

I. Materials and Methods

[0071] Bitumen with a penetration grade of 70/100 has been used as base material for the emulsion. Hydrogen peroxide was used as an oxidizing agent. It is a colorless liquid that is slightly more viscous than water in its pure form. For safety reasons, it was used as a 50% by weight aqueous solution. A mixture of Redicote E-4819 and Redicote E-11 was used as an emulsifier. Redicote E-4819 is a fatty amine derivative blend and was obtained from AkzoNobel. Redicote E-11 is a quaternary ammonium salt and was obtained from AkzoNobel.

[0072] Penetration of the bituminous materials was determined according to the ASTM D5 test method. Higher values of penetration indicate softer consistency.

[0073] The softening point of the bituminous materials was determined according to the ASTM D36 test method, using a Ring-and-Ball Apparatus.

[0074] The high temperature in the performance grading (PG) system of the bituminous materials was determined according to the method defined in AASHTO standard M 320. An increase in this upper performance grade of bituminous binder helps a road resist rutting.

[0075] The aging of the bituminous materials was studied using the rolling thin film oven test (RTFOT) according to the EN 12607-1 standard. In this test, a thin film of bitumen is continuously rotated around the inner surface of a glass jar at 163 C. for 75 minutes with an injection of hot air into the jar every 3 to 4 seconds.

II. Preparation of the Emulsions and Results

[0076] The following cationic emulsions were prepared in a colloidal mill by direct mixing of bitumen (maintained at 130-140 C.) and the dispersing aqueous phase (maintained at 40-50 C.) containing the emulsifier, hydrogen peroxide and acid (HCI) to adjust the pH (examples 1, 2) or by adding hydrogen peroxide to the mixture comprising the other ingredients at 60-80 C., preferably 75-80 C. (examples C1, 3, 4). The preparation time was typically 30 minutes. The emulsions were then stored for 3 hours in an oven at 160 C. so as to obtain residues that were submitted to the tests. CaCl.sub.2 can be used in the present invention to improve the emulsion stability (examples C1, 3, 4).

TABLE-US-00001 Example 1 2 C1 3 4 Bitumen 70/100 (wt. %) 60 60 63 63 63 Redicote E-4819/ 0.25/0.6 0.25/0.6 0/0.6 0/0.8 0/1.0 Redicote E-11 (wt. %) Acid (wt. %) 0.3 0.3 0.1 0.1 0.1 CaCl.sub.2 (wt. %) 0 0 0.2 0.2 0.2 H.sub.2O.sub.2 solution (wt. %) 5 10 0 5 10 Water (wt. %) Rest Rest Rest Rest Rest

[0077] The results of the tests that were performed before and after modification with hydrogen peroxide are shown in the table below.

TABLE-US-00002 Emul- Emul- Emul- Emul- Emul- sion sion sion sion sion Base residue residue residue residue residue bitumen exam- exam- exam- exam- exam- Properties 70/100 ple 1 ple 2 ple C1 ple 3 ple 4 Penetration 85-92 40 25 79 25 23 at 25 C. ( 1/10 mm) Softening 42-43 56 65 46 53 59 Point ( C.)

[0078] It can be seen that the ring & ball softening temperature increases while the penetration decreases with the amount of hydrogen peroxide added, which means that hydrogen peroxide causes hardening of the binder. The use of hydrogen peroxide allowed to convert the initial 70/100 bitumen into a 35/50 bitumen or a 20/30 bitumen meeting all specifications as per EN-12591. Comparative example C1 clearly demonstrates the beneficial effects of using hydrogen peroxide in the emulsions. It can be noted that the process and the drying for 3 hours at 160 C. lead to a residue with almost the same penetration and softening point as the initial bitumen in example C1).

[0079] The performance grading of the residues of the bitumen emulsions modified with hydrogen peroxide were also evaluated, as well as base bitumen. The results are as follows.

TABLE-US-00003 G*/sin delta Temperature C. (Rutting parameter) Specification Base bitumen 70/100 46 8.3 kPa Minimum 1 kPa for 25 52 3.6 kPa mm plate, 1 mm gap at 58 1.67 kPa 10 rad/sec 64 0.7 kPa After aging (RTFOT test) 58 6.75 kPa Minimum 2.2 kPa for 25 mm plate, 1 mm gap at 10 rad/sec

TABLE-US-00004 G*/sin delta Temperature C. (Rutting parameter) Specification Example 1 58 9.2 kPa Minimum 1 kPa for 25 64 4.5 kPa mm plate, 1 mm gap at 70 1.9 kPa 10 rad/sec 73 0.9 kPa After aging (RTFOT test) 70 5.5 kPa Minimum 2.2 kPa for 25 mm plate, 1 mm gap at 10 rad/sec

TABLE-US-00005 G*/sin delta Temperature C. (Rutting parameter) Specification Example 2 64 15.7 kPa Minimum 1 kPa for 25 70 11.22 kPa mm plate, 1 mm gap at 76 5.15 kPa 10 rad/sec 82 2.06 kPa 83 1.46 kPa After aging (RTFOT test) 82 4.4 kPa Minimum 2.2 kPa for 25 mm plate, 1 mm gap at 10 rad/sec

[0080] The temperature at which G*/sin delta less than 1.0 kPa was identified was 61.7 C. (Fail temperature) for base bitumen. Hence, the high temperature in the PG system for base bitumen was 58 C. The temperature at which G*/sin delta less than 1.0 kPa was identified was 72 C. (Fail temperature) for example 1. Hence, the high temperature in the PG system for example 1 was 70 C. The temperature at which G*/sin delta less than 1.0 kPa was identified was 83.2 C. (Fail temperature) for example 2. Hence, the high temperature in the PG system for example 2 was 82 C.

[0081] It can be seen from the above tables that increasing the amount of hydrogen peroxide added to the bitumen emulsion resulted in improving the high temperature PG grade of the emulsion residue, which means a better resistance to rutting.

[0082] Tack coats were also prepared from the emulsions of example 1 and from unmodified base bitumen 70/100 to evaluate the trackless nature of said layers.

[0083] To replicate the field conditions with consistency, a tough sand paper of uniform consistency was identified. The sand as well as consistent granularity of sand enabled uniform evaluation. A sand paper roll of 2 width was cut into standard lengths, and a measured quantity of emulsions was applied on the sand paper. The treated sand papers were dried for 15 minutes at a temp of 40 C. and humidity of 50% in a humidity chamber. The so conditioned sand papers were fixed onto a loaded wheel tester comprising a roller and 25 cycles were repeated for both specimens treated with base bitumen or a hydrogen peroxide-added emulsion (example 1).

[0084] As can be seen on FIG. 1, it was observed that the roller has picked up bitumen from the specimen obtained from base bitumen 70/100 (not treated with peroxide) (photo on the left), whereas no bitumen pick up observed from specimens treated with hydrogen peroxide added emulsion even after 1000 passes (example 1, photo on the right). This clearly establishes that emulsions according to the invention allow for the preparation of tack coats with a trackless finish:

TABLE-US-00006 Tack coat obtained Tack coat obtained from the emulsion from bitumen 70/100 of example 1 Bitumen picked up Yes No after 25 cycles Bitumen picked up Yes No after 1000 cycles