Patent Application
20130046064
Not applicable
Not applicable
1. Field of the Invention
The present invention relates to a compound composition utilizing surface-treated carbon blacks. More particularly, the present invention relates to surface-treated carbon blacks used in conjunction with a functionalized elastomer, where the elastomer is functionalized along the polymer chain, giving a higher probability of increased carbon-black-elastomer interaction, providing substantial reductions in rubber vulcanizate hysteresis and is useful for the manufacture of rubber articles, including tires.
2. General Background of the Invention
The reduction of roiling resistance in tire tread compounds is important in raising the fuel economy of vehicles and reducing carbon dioxide emissions. One method of reducing the rolling resistance of tire tread compounds, normally composed of styrene butadiene copolymers and butadiene or natural rubber polymer blends and carbon black, is to alter the filler characteristics such that the filler-filler interaction is reduced and the filler-elastomer interaction is increased. This works because the highest source of heat generation in carbon-black-filled elastomeric compounds typically arises from the carbon black as a result of its propensity to form through-going networks via high filler-filler interaction. Reducing this filler-filler interaction and increasing the filler-elastomer interaction can substantially reduce the degree of filler networking and compound hysteresis, and thus the rolling resistance of the tire tread compound and ultimately the tire itself. Typically, reduced filler-filler interaction or networking is measured by a decrease in the low strain dynamic modulus, which results in a smaller change in the difference between the low strain and high strain dynamic elastic modulus. This phenomenon is called the Payne Effect.
This Payne Effect is demonstrated in
Methods that can be used to reduce filler-filler and increase filler-elastomer interaction in elastomeric compound compositions include:
First the magnitude of the change in vulcanizate hysteresis with the use of broad distribution carbon blacks has been minimal and on the order of 3 to 10%, based upon tangent delta measurements at 60 to 75° C.
Secondly, the use of coupling agents for carbon black and silica in compound compositions adds additional cost, requires additional mixing steps and special VOC emission handling systems for ethanol emissions that result from activation of the coupling agent used for increasing the filler-elastomer interaction via reactive mixing,
Thirdly, when carbon blacks are used in conjunction with coupling agents, relatively small benefits are also obtained in terms of compound hysteresis reduction.
Lastly, when silica is used with a coupling agent, which does provide significant reduction in vulcanizate hysteresis on the order of 40% or more, penalties are not only again incurred in terms of the cost of the silica and coupling agent, but the silica itself is very abrasive and causes an increase in the wear rate of the rubber mixers used in industrial factories. Silica also requires longer mixing and dispersion times, resulting in higher energy use and cost and lower factory output.
Thus, the object of this invention is to provide a novel rubber compound composition based on surface-treated carbon blacks and a functionalized polymer, that does not require the use of expensive coupling agents, and does not result in premature wear of factory rubber mixers, but yet provides significant reductions in compound hysteresis and maintains or improves compound wet traction more similar to silica, provides good abrasion resistance and provides easy dispersion for shorter mixing cycles, lower energy costs and higher factory throughput versus silica-based compound compositions, Additionally, this unique performance benefit is obtained with the combination of surface-treated carbon blacks and a functionalized solution-SBR, which has its functionalization along the polymer chain that provides a much higher probability of increasing the filler-elastomer interaction as opposed to elastomers with terminal, chain-end functionalization. Prior art, especially for solution SBR, teaches the use of polymer functionalization at the chain ends,
Scientists employed by Columbian Chemicals Company and Lanxess jointly developed the invention disclosed herein. In summarizing the invention, surface-treated carbon blacks have been used in conjunction with a functionalized elastomer, where the elastomer is functionalized along the chain, giving a higher probability of increased carbon-black-elastomer interaction, providing surprising and substantial reductions in hysteresis and benefits in wet traction relative to conventional carbon-black containing compounds, with said reductions in compound hysteresis and increases in wet traction more closely approaching silica-containing compounds, while also maintaining the excellent abrasion resistance of a carbon black compound.
For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein:
FIG. 8 illustrates Payne Effect Reduction for Ozone Treated (5.5 hrs) N234 and Higher Surface Area Carbon Blacks (N115, N134, CD2115) in functionalized (along the chain) BUNA VSL VP PBR-4003 vs a non-treated N234 Control and Silica in Normal BUNA VSL 5025-2 (compounds with 2.0 phr DPG);
FIG. 9 illustrates Tangent Delta Reduction for Ozone Treated (5.5 hrs) N234 and Higher Surface Area Carbon Blacks (N115, N134, CD2115) in functionalized (along the chain) BUNA VSL VP PBR-4003 vs anon-treated N234 Control and Silica in Normal BUNA VSL 5025-2 (compounds with 2.0 phr DPG);
In a preferred embodiment of the present invention, the results of this work in a model tire tread compound have shown significant reduction of tangent delta (main parameter used to evaluate potential of a rubber compound to reduce heat build-up in a dynamic application). In fact, these results have been unexpected in terms of the magnitude of the decrease in tangent delta and the corresponding improvement in predicted wet traction (tangent delta in the range of 0 to −10° C.). This type of behavior, lower tangent delta at 60° C. to 75° C. (lower rolling resistance prediction) and a higher tangent delta at 0° C. (higher wet traction prediction), was surprising for carbon black.
Normally, compound hysteresis reduction is relatively small for carbon black, either used as manufactured or even surface treated, when combined with common and normal SBR, BR, NR or EPDM compounds, and normally one or the other parameters (rolling resistance or wet reaction) might be improved, but not both simultaneously, and not to a significant degree. In the present invention, the combination of the surface-treated carbon black and the functionalized elastomer, with functionalization along the polymer chain, provides a compound composition with significant tangent delta reduction and maintains and improves the potential wet traction response.
What is provided is a compound composition comprised of a surface-treated carbon black, treated via oxidation, oxidation followed by treatment with a base, or chlorination followed by treatment with a base, which provides a carbon black with surface functional groups composed of oxygen, basic or a combination of oxygen and basic functional groups, and a functionalized polymer with functionalization along the polymer chain, with the polymer representing a solution SBR, and the functionalization representing a carboxylic acid (—COOH) or hydroxide (—OH) functionality.
Additionally, there is provided a compound that is reactively mixed to facilitate chemical interaction between the functionalized carbon black and the functionalized elastomer, where reactive mixing is accomplished in a rubber mixer such that the compound is held at an elevated temperature in the range of 145° C. to 160° C. for a time period of 2 to 8 minutes.
The present invention utilizes a typical tire tread compound composition as represented in Table 1, where the compound is composed entirely of the Lanxess functionalized solution SBR, BUNA VSL VP PBR 4003 (hereafter referred to as PBR 4003), but might also be represented by SBR/BR blends of ratios of 60/40 SBR/BR to 100/0 SBR/BR, as shown in Table 2. Additionally, surface-treated N234 carbon black and/or mixtures of surface-treated and as-manufactured carbon black or silica in ratios ranging from 50/50 to 100/0 can be used, in amounts ranging from 40 to 120 phr, along with typical processing oils, ranging from 2 to 50 phr, being representative of a typical tire tread formulation as might be used for tires.
The present invention also utilizes a typical mixing scheme as represented in Table 3, where the order of ingredient addition shown is typical of rubber mixing schemes, but, in addition, normal mixing times and temperatures are used and compared to reactive mixing times and temperatures, which are longer and higher temperature, respectively versus normal mixing schemes. The reactive mixing schemes are required to facilitate the increased carbon black-elastomer interaction of the surface-treated carbon blacks and functionalized polymer with functionalization along the polymer chain to realize the compound advantages of low hysteresis and good wet traction and abrasion resistance as described above.
A preferred embodiment of this invention provides compound compositions prepared with several different carbon black surface treatment schemes with different chemistries, to synergistically interact with the functionalized polymer with functionalization along the polymer chain, and in this case with carboxylic acid functionalization along the polymer chain, to increase filler-elastomer interaction and decrease the filler-filler interaction, as evidenced by reduction of the low strain elastic modulus, per the Payne Effect, and significantly reduce compound hysteresis and maintain and improve compound wet traction and abrasion resistance.
Besides compound compositions including N234, carbon blacks as defined and listed in Table 4 include carbon blacks with nitrogen surface areas in the range of 60 to 300 m2/g (NSA, see ASTM D6556), and structure levels or oil adsorption (OAN, see ASTM D2414) levels in the range of 50 to 180 cc/100 g, as might be produced via the furnace, impingement on lampblack process.
There is provided a compound composition of functionalized polymer with functionalization along the polymer chain and a carbon black surface treatment with oxidation of the carbon black surface via peroxide (e.g. see U.S. Pat. No. 6,120,594) or ozone (e.g. see U.S. Pat. No. 6,471,933) to provide a polar-polar and/or intermolecular-hydrogen-bonding mechanism between the oxygen-based functional groups on the carbon black surface and the carboxylic acid functionality along the polymer chain of the functionalized polymer, with the functionalization along the polymer chain resulting in increased filler-elastomer interaction, reduced filler-filler interaction and reduced Payne Effect.
There is provided a compound composition of functionalized polymer with functionalization along the polymer chain and a carbon black surface treatment with oxidation of the carbon black followed by treatment with amine-based compounds (e.g. see U.S. Pat. No. 5,708,055), preferably diamine compounds, that provide an acid-base interaction with the basic amine functional groups on the carbon black and the carboxylic acid groups along the polymer chain of the functionalized polymer, with the functionalization along the polymer chain resulting in increased filler-elastomer interaction, reduced filler-filler interaction and reduced Payne Effect.
There is provided a compound composition of functionalized polymer with functionalization along the polymer chain and a carbon black surface treatment with oxidation of the carbon black followed by treatment with amine-based compounds, preferably amine compounds with hydroxide or other polar, oxygen containing functional groups, that provides an acid-base interaction and/or acid-base and polar-polar interaction with the functional groups on the carbon black and the carboxylic groups along the polymer chain of the functionalized polymer, with the functionalization along the polymer chain resulting in increased filler-elastomer interaction, reduced filler-filler interaction and reduced Payne Effect.
There is provided a compound composition of functionalized polymer with functionalization along the polymer chain and a carbon black surface treatment with oxidation of the carbon black followed by treatment with hydroxy-based compounds, that provides a polar-polar interaction and/or intermolecular-hydrogen-bonding with the functional groups on the carbon black and the carboxylic groups along the polymer chain of the functionalized polymer, with the functionalization along the polymer chain resulting in increased filler-elastomer interaction, reduced filler-filler interaction and reduced Payne Effect.
There is provided a compound composition of functionalized polymer with functionalization along the polymer chain and a carbon black surface treatment with chlorination of the carbon black followed by treatment with ammonia, that provides an acid-base interaction between the functional groups on the carbon black and the carboxylic groups along the polymer chain of the functionalized polymer, with functionalization along the polymer chain resulting in increased filler-elastomer interaction, reduced filler-filler interaction and reduced Payne Effect.
A compound composition comprised of a surface-treated carbon black and a functionalized polymer with carboxylic-acid functionalization along the polymer chain, with the polymer representing a solution SBR, to reduce compound hysteresis and rolling resistance and improve wet traction in tires, while maintaining good abrasion resistance including passenger, truck and racing tires.
The present invention further provides the use of the inventive compound composition for the production of vulcanizates, which in turn serve for the production of highly reinforced mouldings, in particular for the production of tires.
The present invention further provides the use of the inventive compound composition for the production of rubber mixtures.
The polymers and as manufactured and surface-treated carbon blacks used in this present compound composition invention are listed in Table 5 and analytical results showing the affects of surface treatment are shown in Table 6.
Ozonated samples of carbon black included Sturdivant-milled beaded-carbon-black treated in a rotating drum for various lengths of time, ranging from 1.5 to 5.5 hours, with an air flow containing approximately 2% ozone concentration followed by wet beading and then drying the samples in an oven at 125° C. for six hours.
Hydrogen peroxide samples included powder carbon black wet beaded with a 50/50 weight percent of 35% to 50% hydrogen peroxide in a pin header following Columbian Internal Batch Lab Procedure LS0-1. The resulting wet beads were then dried in a fluid bed drier at 125° C. for two hours.
Amine samples of carbon black were prepared by treating fifty grams of ozonated N234 powder added to 2.5 liters of water and 25 ml of acetone in a 6 liter Lab Max reaction vessel. Ethylene diamine, diluted to a 1% solution in distilled water, was slowly added to the Lab Max with constant stirring until the target pH was reached. The carbon black was separated from the water by pressure filtration and soxhlet extracted with distilled water for 16 hours. The carbon black sample was then coffee milled, wet beaded, and dried in an oven for six hours at 125° C.
Typical examples of the affects of the surface treatments are shown in Table 6, where Volatile Content (Columbian Internal Procedure LS2-700) and pH (ASTM D1512) and Thermometric Titration (Columbian Internal Procedure LS2-702) values are shown, which reflect changes in the surface properties as a result of the surface treatments. As can be seen, the ozone oxidized carbon black shows an absolute 4.7% increase in volatile content, with a dramatic drop in pH and increase in thermometric titration (measure of heat of reaction between carbon black surface moieties and the base, butyl amine, that is used as the titrant), as well as an increase in moisture uptake (more polar groups), indicating the oxidation treatment was successful as the results show the typical increase in surface acidity normally observed for oxidized carbon blacks.
The amine treated carbon black shows a large increase in pH (oxidized CB used as feedstock, so acid groups neutralized) with a corresponding large drop in the thermometric titration value.
Amine treatment appears successful, but some acid sites possibly remain as evidenced by the pH value being <7 and possibly indicates that a carbon black with dual-surface-functionality has been obtained (basic amine and polar, and/or oxygen-based acid sites are both present).
The results of the surface treatment for these three carbon blacks shown in Table 6 represent typical values and represent the carbon black types primarily used for the in-rubber evaluations.
The polymers used in this present compound composition invention listed in Table 5 include Lanxess Buna VSL-5025-2, solution SBR with 50% vinyl and 25% styrene content, 37.5 phr of TDAE oil, and Mooney viscosity ML (1+4) @ 100° C. of 47 MU; and Lanxess PBR 4003, a functionalized polymer containing carboxylic functionalization along the polymer chain, and composed of
The compound variables used in this evaluation are described in Table 7, and compound performance of the compound compositions of the present invention were compared against normal SBR polymer (Lanxess Buna VSL-5025-2), with fillers including regular, ozonated, peroxide or amine treated carbon blacks and silica, with and without silane, and with and without reactive mixing. The in-rubber compound performance properties are listed in Tables 8 through 13. The reactive mixing procedure recommended by Lanxess for use with Si69 includes mixing up to and maintaining a temperature of 150-160° C. for 3 minutes, each for two passes, followed by addition of the curatives on a mill. The all SBR compounds (Table 1 and Tables 8 through 10) were mixed on a Brabender Plasticorder Mini-Mixer, while the SBR/BR compounds (Table 2 and Tables 11-13) were mixed on a GK 1.5 litre intermeshing mixer. Dynamic Properties for the SBR/BR compounds shown in Table 2, were determined using an MTS servo-hydraulic machine for the strain amplitude sweeps and a Gabo Explexor machine was used for determining the temperature sweeps. Amplitude sweeps were conducted under the following conditions: Double shear test piece, 1 Hz frequency and amplitude range from 0.2 to 80% DSA at 60° C. The Temperature Sweeps were conducted under the following conditions: 1% mean strain, 10 Hz frequency, 0.1% amplitude from −120° C. to 100° C. The cure accelerator, DPG (N,N-diphenylguanidine) was varied from 0.2 to 2.0 phr to improve and optimize cure rates due to effects on this properly from the varied surface chemistry of the carbon blacks. Improved cure rates and in-rubber properties were obtained with the higher amount (2.0 phr) of the DPG.
In-rubber properties evaluated included the following: MDR (ASTM D5289), Shore A Hardness (ASTM D2240), Rebound (ASTM D1054) and Stress-Strain (ASTM D412). Dynamic properties for the all SBR compounds in Table 1 were determined using a TA. Instruments Advanced Rheometric Expansion System (ARES) Model LS/M DMA, and were conducted in shear. Amplitude sweeps were conducted under the following conditions: 0% Mean Strain, 10 Hz Frequency, and amplitude range from 0.2-125% ptp at 75° C. The Temperature sweeps were conducted under the following conditions; 0% Mean Strain, 10 Hz Frequency, amplitudes of 8% (40° C. and lower) and 15% ptp (50° C. and higher), and temperature range from −5° C. to 60° C.
Table 8 shows the performance advantages of the Inventive Compound compositions versus normal or Reference Compound compositions typically employed, and
Table 9 shows the performance advantages of the Inventive Compound compositions versus normal or Reference Compound compositions typically employed, and
Table 10 compares the Inventive Compounds containing ozonated carbon blacks of higher surface area than N234, which includes N115, N134 and CD2115 and
Tables 11-13 show the performance advantages of the compositions of the Inventive Compounds versus normal or Reference Compound Compositions typically employed, but in this case SBR/BR blends as described in Table 2, more typical of an actual tire tread compound, are shown. Table 11 shows the basic stress-strain properties indicating a very good balance of modulus, tensile strength and elongation for the Inventive Compounds 4, 6 and 8 versus the normal Reference Carbon Black Compound Compositions 1, 9 and Silica Compound Compositions 10, 11. Table 12 shows the Amplitude Sweep dynamic properties at 60° C., and shows that all Inventive Compounds 4, 6 and 8 give reduced tangent delta in the range of 9% to 21%, relative to the Reference Compound 1 and 9 for N234. The ozonation and amine treatments for Inventive Compounds 4 and 6 had higher tangent delta maximum than Inventive Compound 8, which has an optimal amount of surface oxygen groups or volatile content greater than the 5% level. Consequently, as shown in Table 9, the tangent delta response for Innovative Compound 8, most closely matched the tangent delta response for Silica Compounds 10 and 11. Table 12 also shows the Temperature Sweep data for the SBR/BR Reference and Inventive Compounds, and as can be seen, the Inventive Compounds 4, 6 and 8 have tangent delta values at 0° C. similar to or greater than the Silica Reference Compound 10, indicating equal to greater predicted wet traction response for the Inventive Compounds 4, 6 and 8. The improved predicted rolling resistance and wet traction of Inventive Compound 8 versus the Normal Reference N234 Compound 1 and the Silica Reference Compound 10, is shown graphically in
These results indicate the Inventive Compounds have overcome the challenging hurdle of significantly and simultaneously improving rolling resistance, wet traction, treadwear and mixing and compound costs at the same time in a rubber compound.
The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.
Priority of U.S. Provisional Patent Application Ser. No. 61/237,593, filed 27 Aug. 2009, incorporated herein by reference, is hereby claimed.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US10/43384 | 7/27/2010 | WO | 00 | 10/5/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 61237593 | Aug 2009 | US |
