Polymer-modified Bitumen, Method of Production and Use Thereof for Asphalt

Abstract

The present invention relates to polymer-modified bitumen, to a process for production thereof and to the use thereof for asphalt.

Claims

1. Polymer-modified bitumen obtainable when one or more styrene-butadiene copolymers, optionally dissolved in oil, are admixed with the bitumen at temperatures of at least 150° C. and subsequently the dialkyl polysulfides of formula (I)
R.sup.1—S.sub.(x)—R.sup.2  (I), in which R.sup.1 and R.sup.2 are identical or different and represent a linear or branched C.sub.7-C.sub.8-alkyl radical and x represents numbers from 3 to 8, are admixed.

2. The polymer-modified bitumen according to claim 1, wherein R.sup.1 and R.sup.2 in the dialkyl polysulfides of formula (I) represent a linear or branched C.sub.8-alkyl radical and x represents numbers from 3 to 8.

3. The polymer-modified bitumen according to claim 1, wherein the one or more styrene-butadiene copolymers are composed of 40-99% by weight of 1,3-butadiene and 1-60% by weight of styrene.

4. The polymer-modified bitumen according to claim 1, wherein the one or more styrene-butene copolymers are styrene-butadiene-styrene (SBS) block copolymers.

5. The polymer-modified bitumen according to claim 1, wherein the dialkyl polysulfide of formula (I) is employed in an amount of 0.1% to 1% by weight, based on the amount of the one or more styrene-butadiene copolymers.

6. The polymer-modified bitumen according to claim 1, wherein the one or more styrene-butadiene copolymers are dissolved in at least one mineral oil before they are mixed with the bitumen.

7. The polymer-modified bitumen according to claim 6, wherein the at least one mineral oil is a naphthenic oil.

8. The polymer-modified bitumen according to claim 6, wherein the weight ratio of oil to styrene-butadiene copolymer is 9:1 to 1:1.

9. A process for producing polymer-modified bitumen, comprising admixing at least one styrene-butadiene copolymer, optionally dissolved in oil, with the bitumen at temperatures of at least 150° C. and subsequently admixing the dialkyl polysulfides of formula (I)
R.sup.1—S.sub.(x)—R.sup.2  (I), wherein R.sup.1 and R.sup.2 are identical or different and represent a linear or branched C.sub.7-C.sub.8-alkyl radical and x represents numbers from 3 to 8.

10. The process according to claim 9, further comprising incorporating aggregate.

11. Asphalt comprising the polymer-modified bitumen according to claim 1.

12. A roofing membrane comprising the polymer-modified bitumen according to claim 1.

13. A coating for protecting steel against corrosion comprising the polymer-modified bitumen according to claim 1.

14. The polymer-modified bitumen according to claim 1, wherein the one or more styrene-butadiene copolymers are admixed with the bitumen at temperatures ranging from 160° C. to 250° C.

15. The polymer-modified bitumen according to claim 5, wherein the dialkyl polysulfide of formula (I) is employed in an amount of 0.2% to 0.8% by weight, based on the amount of the one or more styrene-butadiene copolymers.

16. The polymer-modified bitumen according to claim 8, wherein the weight ratio of oil to styrene-butadiene copolymer is 7:1 to 3:1.

17. The process according to claim 9, wherein the at least one styrene-butadiene copolymer is admixed with the bitumen at temperatures ranging from 160° C. to 250° C.

Description

WORKING EXAMPLES

[0046] Materials employed: [0047] SBS, Kraton® D1101, a linear unhydrogenated SBS/SB block copolymer from Kraton Polymers LLC where SBS=styrene-butadiene-styrene block copolymer SB=styrene-butadiene diblock having a polystyrene proportion of 29-33%. [0048] Kraton® D 1102, a linear unhydrogenated SBS/SB block copolymer from Kraton Polymers LLC where SBS=styrene-butadiene-styrene block copolymer SB=styrene-butadiene diblock having a polystyrene proportion of 26.8-30%. [0049] Nynas T 400: naphthenic oil from Nynas AB. [0050] Di-tert-dodecyl pentasulfide from Arkema having the product description TPS® 32. [0051] Dioctyl pentasulfide 40% sulfur employed as Additin® RC 2540 from Lanxess Deutschland GmbH.

Example 1 (Comparative Example)

[0052] Analogously to U.S. Pat. No. 4,554,313, 12 g of the SBS copolymer (SBS, Kraton® 1101) were mixed with 32 g of Nynas T 400 oil at 170° C. This solution was then added to 366 g of bitumen (bitumen 50/70) to afford a solution of 3% by weight of polymer in a bitumen-oil mixture. Subsequently 0.32% by weight of di-tert-dodecyl pentasulfide comprising 32% sulfur (this corresponds in the reaction batch to a sulfur proportion of 0.1% by weight based on the reaction mixture) were added as shown in table 1 and vulcanized for 2 hours by heating to 170° C.

[0053] The thus-obtained composition was then used to cast a DSR test specimen and the MSCR test was performed for 3 stress levels at 60° C. The results are reported in table 1.

Example 1 (Inventive)

[0054] A solution of 12 g of the polymer (SBS, Kraton® 1101) in 32 g of the oil Nynas T 400 was initially produced at 170° C. This solution was added to 366 g of bitumen to result in a solution of 3% by weight of polymer in a bitumen-oil mixture. Subsequently 0.25% by weight of di-octyl pentasulfide comprising 40% sulfur (this corresponds in the reaction batch to a sulfur proportion of 0.1% by weight based on the reaction mixture) were added as shown in table 1 and crosslinking was carried out by heating to 170° C. for 2 hours.

[0055] The dynamic shear rheometer (“DSR”) has proven advantageous for determining the viscoelastic properties, for instance the elastic recovery, of modified bitumens. To determine the elastic properties a “Multiple Stress Creep and Recovery Test (MSCR test)” was performed according to DIN EN 16659 (2013). This MSCR method (“multiple stress creep recovery”) constitutes a simple method which at elevated temperature such as for instance 60° C. makes it possible to achieve rapid determination of the recoverable proportion of a performed deformation in percent (“R value”). The J value indicates a ratio of permanent deformation to employed force and is therefore a measure of the susceptibility of the binder to deforming forces.

[0056] The compositions obtained from the examples 1V and 1E were then used to cast a DSR test specimen and the MSCR test was performed for 3 stress levels at 60° C. In this test, which better reflects the stress conditions on the road than oscillating DSR measurements, the recovery in percent (R-value) was determined in 10 stress cycles comprising a stress phase with constant shear stress of 1 second duration and a subsequent destress phase of 9 seconds duration. This test was performed with three stress levels of 0.1 kPa, 1.6 kPa and 3.2 kPa. The deformations during the force-controlled cycles were captured with subdivision into three deformation magnitudes.

[0057] The results are listed in Table 1.

TABLE-US-00001 TABLE 1 DSR MSCR test results Example 1E (inventive) Example 1V 0.1% by weight S 0.1% by weight S in the form of in the form of dioctyl(C8) di-tert-dodecyl(C12) Crosslinker pentasulfide pentasulfide R % 0.1 kPa 33.84 26.63 R % 1.6 kPa 10.32 6.14 R % 3.2 kPa 2.68 0.34 J 1/kPa 0.1 kPa 1.9040 2.2371 J 1/kPa 1.6 kPa 2.9857 3.3451 J 1/kPa 3.2 kPa 3.7305 4.1041

[0058] For each stress level the R value for elastic recovery was highest, and the J value for susceptibility to deformation lowest, for dioctyl pentasulfide despite metered addition of the same sulfur content.

Example 2 (Inventive) without Oil

[0059] Initially 12 g of the more soluble polymer SBS, Kraton® 1102 was added to 366 g of bitumen at 180° C. to form a solution of 3% by weight of polymer in bitumen. Subsequently 0.25% by weight of dioctyl pentasulfide comprising 40% sulfur (S proportion=0.1% by weight) were added according to table 1 and the crosslinking was performed by heating to 170° C. for 2 hours.

TABLE-US-00002 TABLE 2 DSR MSCR test results Kraton ® 1102 Kraton ® 1102 crosslinked with crosslinked with 0.1% by weight S 0.1% by weight S in the form of in the form of Kraton ® 1102, dioctyl(C8) di-tert-dodecyl(C12) uncrosslinked pentasulfide pentasulfide R % 0.1 kPa 5.73 14.92 14.35 R % 1.6 kPa 3.26 10.7 9.91 R % 3.2 kPa 1.38 6.14 5.32

[0060] In this experiment, too, the C.sub.8-dialkyl polysulfide showed the best elastic recovery, as is apparent from table 2.