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 obtained by 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.1S.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.8-alkyl radical and x represents 5, are admixed.

2. 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.

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

4. 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.

5. The polymer-modified bitumen according to claim 2, 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.

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

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

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

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

13. 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.

Description

WORKING EXAMPLES

(1) Materials Employed:

(2) 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%. 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%. Nynas T 400: naphthenic oil from Nynas AB. Di-tert-dodecyl pentasulfide from Arkema having the product description TPS 32. Dioctyl pentasulfide 40% sulfur employed as Additin RC 2540 from Lanxess Deutschland GmbH.

Example 1 (Comparative Example)

(3) 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.

(4) 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)

(5) 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.

(6) 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.

(7) 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.

(8) The results are listed in Table 1.

(9) 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

(10) 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

(11) 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.

(12) 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

(13) In this experiment, too, the C.sub.8-dialkyl polysulfide showed the best elastic recovery, as is apparent from table 2.