Sulfur-crosslinkable rubber mixture, vulcanizate of the rubber mixture, and vehicle tire

Abstract

The invention relates to a sulfur-crosslinkable rubber mixture, to the vulcanizate thereof, and to a vehicle tire. The rubber mixture according to the invention comprises at least the following constituents: at least one diene rubber; and, at least one char (HTC char) obtained by hydrothermal carbonization of at least one starting substance. A vehicle tire according to the invention comprises at least one vulcanizate according to the invention of the rubber mixture in at least one component.

Claims

1. A sulfur-crosslinkable rubber mixture comprising: at least one diene rubber, and at least one hydrothermal carbonized coal produced by hydrothermal carbonization of at least one starting substance, wherein the at least one hydrothermal carbonized coal has a BET nitrogen surface area according to DIN ISO 9277 of 20 to 200 m.sup.2/g; wherein the at least one hydrothermal carbonized coal is unactivated hydrothermal carbonized coal; wherein the hydrothermal carbonization is carried out at a temperature of 150? C. to 300? C. and a pressure of 2 bar to 20 bar; wherein the at least one hydrothermal carbonized coal has a surface functionality; wherein the sulfur-crosslinkable rubber mixture is free from silane coupling agents; and wherein at least one metal halide is used in the hydrothermal carbonization.

2. The sulfur-crosslinkable rubber mixture according to claim 1, wherein the at least one metal halide is at least one metal chloride.

3. The sulfur-crosslinkable rubber mixture according to claim 1, wherein the at least one starting substance is a degradation product of at least one biomass.

4. The sulfur-crosslinkable rubber mixture according to claim 1, wherein the at least one starting substance is two starting substances comprising a biomass and a degradation product of the biomass.

5. The sulfur-crosslinkable rubber mixture according to claim 1, wherein the at least one starting substance is selected from the group consisting of lignin, cellulose, hemicellulose and sugar.

6. The sulfur-crosslinkable rubber mixture according to claim 1, wherein the at least one starting substance is glucose.

7. The sulfur-crosslinkable rubber mixture according to claim 1, wherein the sulfur-crosslinkable rubber mixture further comprises 5 to 100 phr of the at least one hydrothermal carbonized coal.

8. The sulfur-crosslinkable rubber mixture according to claim 1, which is incorporated in at least one of side wall, horn profile and inner component of a vehicle, and subjected to sulfur vulcanization.

9. The sulfur-crosslinkable rubber mixture according to claim 1, wherein the surface functionality is functional groups at the surface of the at least one hydrothermal carbonized coal, and the functional groups are carbon-oxygen-containing functional groups, nitrogen, sulfur, and/or halides.

10. The sulfur-crosslinkable rubber mixture according to claim 1, wherein the hydrothermal carbonization is carried out at a temperature of 210? C. to 230? C.

11. The sulfur-crosslinkable rubber mixture according to claim 1, wherein a weight ratio of the at least one metal halide to starting substance is 0.3:1 to 3.0:1.

12. The sulfur-crosslinkable rubber mixture according to claim 1, wherein the sulfur-crosslinkable rubber mixture is devoid of any further reinforcing filler.

13. The sulfur-crosslinkable rubber mixture according to claim 1, wherein the at least one metal halide is at least ZnCl.sub.2.

14. The sulfur-crosslinkable rubber mixture according to claim 13, further comprising a salt selected from the group consisting of LiCl, NaCl and KCl.

15. The sulfur-crosslinkable rubber mixture according to claim 1, wherein the at least one starting substance is at least one biomass.

16. The sulfur-crosslinkable rubber mixture according to claim 15, wherein the biomass is selected from the group consisting of cereal husks, nut husks, fruit peels, green waste, wood waste, sawdust, and algae.

Description

(1) An HTC char produced using at least one salt has an increased surface roughness and an optimized surface functionality. The surface roughness may be qualitatively assessed using TEM images by way of comparison as shown for example in FIGS. 1 and 2.

(2) FIG. 1 shows an HTC char produced using the salt mixture ZnCl.sub.2/KCl (reaction at 180? C. for 12 hours).

(3) FIG. 2 shows a char produced without using the salt mixture under otherwise identical conditions (reaction at 180? C. for 12 hours).

(4) As is apparent from the comparison of FIG. 1 and FIG. 2 the HTC char produced using at least one salt has a higher roughness.

(5) FIG. 3 is an exemplary FTIR spectrum. Here, transmission is plotted qualitatively (units: a.u.=arbitrary units) against wavenumber (W for short) (units: cm.sup.?1).

(6) The spectra and their relevant sections are shown for the following substances: for the starting substance coconut husk flour 4; for a hydrochar 5 produced by hydrothermal carbonization of coconut husk flour (reaction at 180? C. for 12 hours) without salt for a salt hydrochar 6 produced using the salt ZnCl.sub.2 but otherwise identical conditions (reaction at 180? C. for 12 hours; coconut husk flour); for an activated salt hydrochar 7 produced using the salt mixture LiCl/ZnCl.sub.2 (reaction at 180? C. for 12 hours; coconut husk flour) and subsequent activation by water vapor at 500? C. for 1 hour; for carbon black N 660 8.

(7) It is apparent in FIG. 3 that a salt hydrochar 6 still comprises functional groups compared to a salt hydrochar 7 activated in a further step, as is apparent from the bands for carbonyl compounds 1 and the bands for oxygen-containing functional groups 3. The char produced with salt simultaneously exhibits bands for C?C double bonds 2 in the FTIR spectrum. The spectrum for the carbon black 8 also exhibits bands for oxygen-containing functional groups 3 and for C?C double bonds 2 and the salt hydrochar 6 is therefore chemically at least similar to carbon blacks. The salt hydrochar thus has functional groups which may possibly result in increased interactions in a rubber mixture. Compared to hydrochar (without salt) 5 it is apparent that while use of the salt causes part of the functionality to be lost and only the above described groups to be retained the band for oxygen-containing functional groups 3 is actually stronger in the salt hydrochar 6.

(8) It is further conceivable that the loss of the potentially disruptive groups results in improved interactivity of the salt hydrochar in a rubber mixture.

(9) The HTC chars summarized in table 1 were incorporated into rubber mixtures whose general formulations are shown in table 5. When choosing the chars the focus was on sustainability for economic reasons and several waste biomasses were therefore selected as starting substances. The mixtures labeled E are mixtures according to the invention which contain at least one HTC char as a filler while the mixtures marked with V are comparative mixtures containing carbon black as a filler.

(10) The mixture was produced according to the process customary in the rubber industry under standard conditions in three stages in a laboratory mixer having a volume of 300 milliliters to 3 liters wherein initially in the first mixing stage (preliminary mixing stage) all constituents apart from the vulcanization system (sulfur and vulcanization influencers) were mixed at 145? C. to 165? C., target temperatures of 152? C. to 157? C., for 200 to 600 seconds. This preliminary mixture was mixed again in a further step. Addition of the vulcanization system in the third stage (final mixing stage) afforded the final mixture, mixing being carried out at 90? C. to 120? C. for 180 to 300 seconds.

(11) All mixtures were used to produce test specimens by vulcanization and these test specimens were used to determine material properties typical for the rubber industry and these are summarized in tables 6 and 7. The tests described above were carried out on test samples using the following test methods: Archimedes density Shore A hardness at room temperature RT and 70? C. using a durometer according to ISO 868 Rebound resilience at RT and 70? C. according to ISO 4662 Stress values at 50% and 100% strain at room temperature according to ISO 37 and ASTM D 412 (M50 and M100)

(12) TABLE-US-00005 TABLE 5 Constituents Units V1 E1-E8 V2 E9-E16 SSBR .sup.g) phr 100 100 100 100 Carbon black N 660 phr 60 40 Char-varies .sup.h) phr 60 40 TDAE oil phr 3 3 3 3 Other additives .sup.i) phr 11 11 11 11 TBBS accelerator phr 0.7 0.7 0.7 0.7 Sulfur phr 1.7 1.7 1.7 1.7
Substances Used g) SSBR: Nipol NS 210R, Zeon Europe GmbH h) chars from table 1; as reported in tables 6 to 9, in each case in the reported amounts of 60 or 40 phr i) aging stabilizers, antiozonant wax, zinc oxide, stearic acid

(13) As is apparent from tables 6 and 7 carbon black (N 660) (mixtures V1 and V2) may be completely substituted by HTC chars, the reduced rebound resiliences resulting in improved room-temperature wet grip indicators, especially for use in vehicle tires. Stiffness (values for M50 and M100 hardnesses) and thus the handling indicators and rebound resilience at 70? C. remain at a comparable level acceptable for use in vehicle tires. In addition, the rubber mixtures according to the invention show a reduced density compared to the respective comparative mixtures which in turn results in lighter and thus rolling resistance-optimized components for vehicle tires.

(14) TABLE-US-00006 TABLE 6 V1 E1 E2 E3 E4 E5 E6 E7 E8 Char no. from tab. 1 Properties Units 1 2 3 4 5 6 7 8 Density g/cm.sup.3 1.16 1.07 1.07 1.06 1.05 1.07 1.06 1.08 1.09 Hardness RT Shore A 62.1 65.7 65.0 59.2 57.0 65.4 64.1 68.2 62.8 Hardness Shore A 58.8 59.0 59.4 52.3 47.6 56.2 55.6 62.0 56.7 70? C. Reb. resil. % 52.2 48.4 50.6 51.2 50.8 50.8 51.8 48.4 51.8 RT Reb. resil. % 59.4 56.0 53.6 56.2 53.2 52.0 55.2 56.4 56.4 70? C. M50 MPa 1.4 1.9 1.9 1.3 1.1 1.6 1.7 1.8 1.4 M100 MPa 2.4 2.4 3.0 1.7 1.4 2.0 2.4 2.6 1.9

(15) TABLE-US-00007 TABLE 7 V2 E9 E10 E11 E12 E13 E14 E15 E16 Char no. from tab. 1 Properties Units 1 2 3 4 5 6 7 8 Density g/cm.sup.3 1.10 1.05 1.04 1.04 1.03 1.04 1.04 1.02 1.07 Hardness RT Sh A 51.6 59.2 55.9 51.8 50.6 56.7 55.1 54.5 54.1 Hardness 70? C. Sh A 49.3 53.6 46.8 48.2 44.6 48.6 47.9 45.2 46.5 Rebound % 53.2 52.0 55.2 54.0 54.8 54.6 55.2 53.0 56.4 resilience RT Rebound % 61.6 58.4 57.2 59.4 58.8 57.0 58.4 55.0 58.2 resilience 70? C. M50 MPa 1.0 1.4 1.2 1.0 0.9 1.1 1.2 1.0 1.1

(16) As further working examples the hydrochars reported in tables 2 to 4 may furthermore be employed in the rubber mixture according to the invention.

LIST OF REFERENCE NUMERALS

(17) (Part of the Description)

(18) 1 band for carbonyl compound C?O (in FTIR spectrum) 2 band for C?C double bond (in FTIR spectrum) 3 band for oxygen-containing functional groups O (in FTIR spectrum) 4 section of the FTIR spectrum for the starting substance coconut husk flour 5 section of the FTIR spectrum for hydrochar: HTC (12 h, 180? C.) 6 section of the FTIR spectrum for salt hydrochar: HTC (12 h, 180? C.) with zinc chloride 7 section of the FTIR spectrum for activated salt hydrochar: HTC (12 h, 180? C.) with lithium chloride/zinc chloride and activated (1 h, 500? C.) with steam 8 section of the FTIR spectrum for carbon black N 660