Improved alumina reinforced rubber composition

Abstract

Described herein is a novel elastomeric composition having an alumina filler and a silane coupling agent wherein the silane coupling agent is not a blocked mercaptosilane and has a sulfur bridge having an average of 2.5 sulfur or less bridged sulfur. The elastomer composition shows surprisingly good tensile properties. The elastomer composition is particularly useful in rubber articles, such as tires and tire treads.

Description

Technical Field

[0001] The present subject matter relates to rubber compositions utilizing alumina fillers, and more particularly, to rubber compositions using alumina as a filler and silanes as a covering agent, which rubber compositions can be used in the manufacture of tires and exhibit properties superior to rubber compositions reinforced with alumina and / or silica. Background Art

[0002] The lack of infrastructure to support electric vehicle charging, the relatively long recharge rates, and the desire to reduce the carbon footprint of electric vehicles, which are still charged with electricity derived from fossil fuels, have made vehicle efficiency, and particularly tire rolling resistance, a primary consideration for tire designers. At the same time, the increase in weight and high torque and power of electric vehicles requires continued improvement in adhesion in both dry and wet conditions, as well as wear improvements.

[0003] Many solutions have been proposed to reduce the rolling resistance of tires and improve their adhesion, but these solutions are associated with a loss of wear resistance. Conventional white fillers such as silica, alumina, bentonite, clay, kaolin, chalk, titanium oxide, talc, etc., lead to improvements in rolling resistance and traction in dry and wet conditions, but also result in a loss of wear resistance.

[0004] The rubber and tire industry has investigated alumina as a means of improving tire performance. Improvements in rolling resistance have been demonstrated by using alumina fillers in combination with silane linkers, as described, for example, in U.S. Patent No. 5,900,449, which describes the use of alumina-reinforced rubber compositions with conventional silane Si69, or in European Patent No. 3,345,775, which describes alumina-reinforced rubber compositions with novel NXT silanes.

[0005] Silane coupling agents are well known to those skilled in the art and have been described, for example, in U.S. Patent No. 7,202,295. "Coupling agent" is more precisely understood to mean an agent capable of establishing a sufficient chemical and / or physical connection between the filler in question and the elastomer; such coupling agents, which are at least bifunctional, have, for example, the simplified general formula "YTX", in which:

[0006] Y represents a functional group ("Y" functional group) capable of physical and / or chemical bonding to an inorganic filler, such a bond being able to be established, for example, between a silicon atom of the coupling agent and a surface hydroxyl (OH) group of the inorganic filler (e.g., surface silanol in the case of silica);

[0007] X represents a functional group capable of physical and / or chemical bonding to the elastomer, for example, through a sulfur atom ("X" functional group);

[0008] T represents a group that enables Y and X to be linked.

[0009] The coupling agent must in particular not be confused with a simple reagent for capping the filler in question, which simple reagent, in a known manner, may comprise a Y functional group reactive with respect to the filler but lacks an X functional group reactive with respect to the elastomer.

[0010] Improvements in alumina-reinforced rubber compositions for the tire industry, which have shown promising results compared to conventional silica mixtures, would be desirable. Despite the advantages of alumina as a filler, the tire industry has been forced to adopt it in favor of conventional silica mixtures because industrial mixtures utilizing alumina generally do not exhibit the expected performance characteristics. The discovery of industrially scalable formulated rubber compositions that exhibit superior results would be particularly useful in the tire industry. Summary of the Invention

[0011] Aspects and advantages of the present invention will be set forth in part in the following description, or may be obvious from the detailed description, or may be learned through practice of the present invention.

[0012] In one exemplary embodiment, a rubber composition is described that includes a diene rubber elastomer and a reinforcing alumina filler, a silane coupling agent having an average of 2.5 or fewer bridging sulfurs, and a vulcanization system, the silane coupling agent not being a blocked mercaptosilane.

[0013] In another exemplary embodiment, the rubber composition contains an average of 2.4 or fewer bridging sulfurs.

[0014] In another exemplary embodiment, a rubber composition is described that includes a diene rubber elastomer and a reinforcing alumina filler, and a silane coupling agent having an average of 2.5 or less bridging sulfurs and a vulcanization system that does not contain DPG, the silane coupling agent not being a blocked mercaptosilane.

[0015] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims.The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the detailed description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] A complete and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art is set forth in the specification with reference to the accompanying drawings, wherein:

[0017] Figure 1 A graph of the stress-strain curve of the elastomer of Example 1 is provided.

[0018] Figure 2 A graph of the stress-strain curve for the elastomer of Example 2 is provided.

[0019] Figure 3 A graph of the stress-strain curve for the elastomer of Example 3 is provided.

[0020] The use of the same or similar reference numbers in different drawings denotes the same or similar features. DETAILED DESCRIPTION

[0021] The present invention provides a rubber composition that utilizes alumina reinforcing filler and non-terminated mercaptosilane with a sulfur grade of 2.4 or lower. For the purpose of describing the present invention, specific reference will now be made to embodiments and / or methods of the present invention. Each example is provided as an explanation of the present invention rather than a limitation of the present invention. In fact, it will be clear to those skilled in the art that various modifications and changes can be made in the present invention without departing from the scope or essence of the present invention. For example, the features or steps illustrated or described as part of an embodiment can be used together with another embodiment or step to produce yet another embodiment or method. Therefore, it is desired that the present invention encompasses such modifications and variations as if they were within the scope of the appended claims and their equivalents.

[0022] The rubber composition according to the present invention is particularly useful for manufacturing tire treads intended for installation on passenger cars, light trucks, vans, bicycles, motorcycles and trucks, aircraft, and civil engineering, agricultural and loading and unloading machinery. Treads comprising the rubber composition as disclosed in accordance with the present invention can be used to manufacture new tires or to retread worn tires.

[0023] Alumina, which can be used as reinforcing filler, can have a 30m 2 / g to 400m 2 / g, and preferably 80m 2 / g to 250m 2 / g of NSA surface area, and 100m 2 / cm 3 to 1360m 2 / cm 3 The volume surface area of ​​the NSA is 100 m. VP Aeroperl ALU 100 / 30 alumina from Evonik and Baikalox CR125 from Baikowski are two examples that can be used according to the present invention. The volume of the filler is similar, however, the weight of the alumina is less than the silica reference used in the following examples. VP Aeroperl has a 100 m 2 / g NSA surface area and 290m 2 / cm3 NSA volume surface area. Baikalox CR125 has 101m 2 / g NSA surface area and 340m 2 / cm 3 The reference silica RP160 (Solvay Zeosil 1165MP) has a NSA volume surface area of ​​159 m 2 / g NSA surface area and 319m 2 / cm 3 The NSA volume surface area is calculated. Alumina typically has a pH of 7-10. Silica, used as a reference, has a pH of 6.5 or lower. The alumina used in this work is also known to be microporous. Microporosity was estimated by observing the difference between the surface area measured by BET and CTAB, as shown in Table 1 below. The greater the difference, the greater the estimated microporosity.

[0024] Table 1. Properties of aluminum oxide .

[0025] filler <![CDATA[NSA(m 2 / g)]]> <![CDATA[CTAB(m 2 / g)]]> Solvay 1165MP 159 158 CR125 101 83.6 Aeroperl 100 71.7

[0026] Silane coupling agents are well known and are sulfur-containing organosilicon compounds that react with the silanol groups of silica during mixing and with the elastomer during vulcanization, resulting in improved properties of the cured rubber composition. It has been found that any organosilicon compound containing an average of less than 2.4 sulfur groups in the bridge is surprisingly useful in practicing embodiments of the present invention. Equally surprising is that blocked mercaptosilanes have not been shown to have the same positive results as other non-blocked mercaptosilanes that originally contained an average of less than 2.4 sulfur groups. Examples of suitable non-blocked mercaptosilane coupling agents having an average of less than 2.4 sulfur groups in the bridge include 3,3'-bis(triethoxysilylpropyl) disulfide (known as Si75 and Si266).

[0027] A silane with an average of more than 2.4 sulfurs in the bridge is SI69 or bis[3-(triethoxysilyl)propyl]tetrasulfide, as shown in the following structure (I):

[0028]

[0029] Silanes with an average of less than 2.4 sulfur groups in the bridge include SI-75 or SI266, bis(triethoxysilylpropyl) disulfide; MESPT silane; NXT Reg.; NXT v45; DSP18; Octeo; Si363; and MPS, mercaptopropyltriethoxysilane, as shown below in structures (II), (III), (IV), (V), (VI), (VII), (VIII), and (IX), respectively. Note that Octeo (VII) does not contain a reactive sulfur group and is therefore considered the least reactive of these silanes:

[0030]

[0031]

[0032] Typically, the amount added is between 4 and 10 weight percent, or alternatively between 5 and 9 weight percent, of the total weight of alumina added to the rubber composition.

[0033] Elastomer :The rubber elastomer disclosed in the embodiments herein is styrene-butadiene rubber (SBR). Rubber elastomers suitable for use with specific embodiments of the present invention include substantially unsaturated diene elastomers, and also include highly unsaturated diene elastomers, such as polybutadiene rubber (BR), polyisoprene rubber (IR), natural rubber (NR), isobutylene isoprene rubber (IIR) butadiene copolymers, isoprene copolymers and mixtures of these elastomers. Polyisoprene includes synthetic cis-1,4-polyisoprene, which may be characterized in that it has greater than 90 mol%, or alternatively greater than 98 mol% of cis-1,4 bonds. Specific embodiments of the rubber composition disclosed herein include only natural rubber.

[0034] Also suitable for use in embodiments of the present invention are rubber elastomers which are copolymers and include, for example, butadiene-styrene copolymers (SBR), butadiene-isoprene copolymers (BIR), isoprene-styrene copolymers (SIR), and isoprene-butadiene-styrene copolymers (SBIR), and mixtures thereof.

[0035] The elastomeric system may be a blend of various elastomers totaling 100 phr.

[0036] Reinforcement fillers : In addition to the above-mentioned alumina reinforcing fillers, other reinforcing fillers including carbon black and silica may also be included.

[0037] Other fillers may also be included as reinforcing fillers for the elastomeric system, for example, graphene, graphite, zeolites, and the like.

[0038] plasticizers : plasticizer comprises oil, resin (from petroleum or other natural renewable resources, for example sunflower seed, citrus orange peel).Processing oil is well known to those of ordinary skill in the art, is usually extracted from petroleum and is classified as paraffin, aromatic or naphthenic type processing oil, comprises MES and TDAE oil.Also known processing oil comprises, especially based on plant oil, such as sunflower oil, rapeseed oil and vegetable oil.Some rubber compositions disclosed herein may comprise elastomer, such as styrene-butadiene rubber, it has been increased with one or more such processing oils, but such oil is limited to 40phr of the total elastomer content of this rubber composition in the rubber composition of a specific embodiment and is no more than.

[0039] Vulcanization system For specific embodiments, the vulcanization system is preferably a sulfur-based vulcanization system, but other vulcanizing agents known to those skilled in the art may also be useful, such as peroxides and ionic crosslinking agents. As used herein, vulcanizing agents are those materials that cause crosslinking of the rubber and therefore can only be added to the productive mix so that premature curing does not occur, such agents include, for example, elemental sulfur, sulfur-donating agents, and peroxides.

[0040] The rubber composition may further include a vulcanization retarder, a vulcanization system based on, for example, sulfur or peroxide, a vulcanization accelerator, a vulcanization activator, etc. The vulcanization system may also include various known auxiliary accelerators or vulcanization activators, such as zinc oxide, stearic acid, and guanidine derivatives (specifically diphenylguanidine or "DPG").

[0041] Antidegradants : In addition to the compounds already described, the rubber compositions disclosed herein may also comprise all or part of the components usually used in diene rubber compositions intended for use in the manufacture of tires, such as additional protective agents of the type comprising antioxidants and / or antiozonants, such as 6PPD, 77PD, TMQ, hindered phenols and waxes.

[0042] Other components If desired, one or more conventional non-reinforcing fillers such as clay, bentonite, talc, chalk kaolin, aluminosilicates, fibers or coal may also be added.

[0043] Diphenylguanine or "DPG" is often used as an accelerator for the cure of rubber compositions. Rubber compositions lacking "DPG" typically have longer cure times.

[0044] Mixing and production :

[0045] The rubber composition as an embodiment of the present invention can be prepared in a suitable mixer in a manner known to those skilled in the art. Typically, mixing can be carried out using two consecutive preparation stages, the first stage being a thermomechanical work at a high temperature, followed by a second stage being a mechanical work at a lower temperature.

[0046] The first stage (sometimes called the "non-productive" stage) involves thoroughly mixing the various ingredients of the composition, excluding some of the vulcanization system, such as the vulcanizing agent, accelerator, and retardant, usually by kneading. The first stage is carried out in a suitable kneading device, such as a Banbury-type internal mixer, until a maximum temperature, generally between 120° C. and 190° C., is reached under the action of mechanical work and high shear applied to the mixture, indicating that the components are fully dispersed.

[0047] After cooling the mixture, implement the second stage of mechanical work at a lower temperature.Sometimes referred to as the "productivity" stage, this finishing stage comprises using suitable device (such as open mill) to mix some vulcanization systems (comprising vulcanizing agent, accelerator and retarder) in the aforementioned vulcanization system that do not add in the "non-productivity" stage into the rubber composition.It carries out appropriate time (usually, for example, between 1 minute and 30 minutes or between 7 minutes and 15 minutes) under enough low temperature (i.e., lower than the vulcanization temperature of mixture), to prevent premature vulcanization.

[0048] The rubber composition can be formed into usable articles, including tire components. The tire tread, for example, can be formed as a tread band and subsequently made into a tire, or it can be formed directly onto the tire carcass, for example by extrusion, and then cured in a mold. Other components, such as those located in the bead area or sidewalls of the tire, can be formed and assembled into a green tire and then cured as the tire cures.

[0049] The present invention is further illustrated by the following examples, which are to be regarded as illustrative only and not limiting of the invention in any way.

[0050] The characterization of the novel aluminas and silanes used and the properties of the rubber compositions disclosed in the examples were evaluated as follows.

[0051] Rheometer : Curing and curing properties of the rubber composition were carried out by using MDR (Moving Die Rheometer) according to ASTM D 2084. The test was carried out at 150°C.

[0052] Surface area measurementBET surface measurements were performed according to the Brunauer-Emmett-Teller method described in the "Journal of the American Society," Vol. 60, p. 309, February 1938, and corresponding to NFT standard 45007 (November 1987). CTAB surface measurements were performed according to ASTM D6845-20, "Standard Test Method for Silica, Precipitated, Hydrated—CTAB (Cetyltrimethylammonium Bromide) Surface Area."

[0053] Example 1 :

[0054] In this example, Aeroperl alumina reinforced compositions using different silanes are compared. An SBR elastomer with a TG = -65°C was used.

[0055] In these compositions, all parts are expressed as weight per hundred parts of elastomer. In this example, the components listed in Table 1 below were combined with an antidegradant package comprising an antioxidant and a wax:

[0056] Table 1. Example 1 mixture :

[0057]

[0058]

[0059] Results: The appearance of the uncured rubber was evaluated after grinding. The mixtures with the best appearance, having a smooth grey surface, were mixtures MA01, MA02, MA10 and MA09, which represent mixtures with Si-266, Si-75, Octeo and DPS18.

[0060] The NXT silane and Si-363 mixtures, MA07, MA08, and MA03, appeared to have poor appearance, exhibiting a rough, tan surface with a grainy appearance. Surprisingly, the NXT silanes had poor appearance and surface roughness of the raw rubber mixture. Generally, these NXT silanes exhibited good stability and lower reactivity than Si-69 when mixed with silica, but did not exhibit the advantages of Aeroperl alumina.

[0061] Tensile properties: These tests allow the determination of elastic stress and breaking properties. Unless otherwise stated, these tests were carried out in accordance with standard ASTM D 412, 1998 (sample C). All these tensile measurements were carried out in accordance with standard ASTM D 1349 (1999) under conditions of normal temperature and relative humidity and are reported in Table 2 and shown in Table 2. Figure 1 middle.

[0062] Table 2. Results of Example 1 :

[0063]

[0064] This example utilizes Aeropearl alumina with different silanes. Test results show that silanes with sulfur bridges (having less than an average of 2.4 sulfurs) produce rubber compositions with good tensile properties. For example, Example Si-363 contains a thiol head group. This is considered the most reactive sulfur-containing silane and results in poor tensile properties. The NXT blends, MA07 and MA08, had poor tensile results, which correlated with evidence of higher reactivity observed from the poor appearance after mixing. The blend MA11 containing Si-69, which has an average of 3.8 sulfurs, also showed poor tensile testing. Blends with silanes (having sulfur bridges and having less than an average of 2.4 sulfurs in the sulfur bridges), such as blends using Si266 silane, MA01; Si75 silane, MA02; MESPT silane, MA06; DPS silane, MA09 and Octeo silane, MA10, showed good results.

[0065] Example 2:

[0066] In this example, Baikalox alumina reinforced compositions use different silanes. In this example, the components listed in Table 3 below are expressed as weight per hundred parts of elastomer, combined with an antidegradant package containing antioxidants and waxes:

[0067] Table 3. Example 2 mixture :

[0068] MB01 MB02 MB03 MB04 MB05 MB06 MB07 SBR 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Sil160MP 110.0 Baikalox 177.0 177.0 177.0 177.0 177.0 ALU65 177.0 SI75 10.8 NXT Regular (New) 12.2 SI266 10.5 6.8 OCTEO 6.25 SI69 11.0 12.0 MPS 5.1 DPG 2.4 AgriPure 80(HTO) 12.0 12.0 12.0 12.0 12.0 12.0 12.0 Escorez 5600 60.0 60.0 60.0 60.0 60.0 60.0 60.0 SAD 3.0 3.0 3.0 3.0 3.0 3.0 3.0 ZNO 0.9 0.9 0.9 0.9 0.9 0.9 0.9 sulfur 0.8 1.8 2.1 2.1 2.1 2.1 2.1 CBS 2.3 2.3 2.3 2.3 2.3 2.3 2.3

[0069] Table 4. Results of Example 2 :

[0070] MB01 MB02 MB03 MB04 MB05 MB06 MB07 Fracture strain (mm / mm) 725 1100 500 1050 650 650 1220 Fracture stress (MPa) 18.6 17.0 12.3 16.0 12.3 10.5 15.5

[0071] The results here show that the alumina-filled mixture using Si-69 MB06 is not similar to the silica-filled mixture using Si-69 MB01. The results of Example 2 also show the same trend as shown in Example 1, namely, the mixtures filled with alumina with sulfur bridges and silanes with an average of 2.4 or fewer sulfurs show favorable tensile properties, while more reactive silanes or silanes with more sulfur show less favorable tensile properties. Another alumina from Evonik, ALU65, was tested with Si-266 (MB07) and showed good tensile properties similar to Baikalox and Si-266 (MB04).

[0072] Example 3: In this example, a silica-reinforced composition used a different silane and served as a reference to the alumina-reinforced mixture described above in Example 2. In this example, the components listed in Table 5 below, expressed as weight per hundred parts of elastomer, were combined with an antidegradant package comprising an antioxidant and a wax:

[0073] Table 5. Example 3 mixture .

[0074] Components MC01 MC02 MC03 MC04 MC05 MC06 MC07 MC08 SBR 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 SI75 10.8 SI363 11.0 20.0 SI266 (New Continuation) 9.7 SIL160MP 110.0 110.0 110.0 110.0 110.0 110.0 110.0 110.0 NXT Regular (New) 14.8 7.4 MPS 4.9 OCTEO 5.9 DPS18 7.5 AgriPure 80(HTO) 12.0 12.0 12.0 12.0 12.0 12.0 12.0 12.0 Escorez 5600 60.0 60.0 60.0 60.0 60.0 60.0 60.0 60.0 DPG 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 Si69 11.0 SAD 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 ZNO 0.9 0.9 0.9 0.9 0.9 0.90 0.9 0.9 sulfur 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 CBS 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3

[0075] Table 6. Results of Example 3 .

[0076] Components MC01 MC02 MC03 MC04 MC05 MC06 MC07 MC08 Fracture strain (mm / mm) 823 971 752 870 954 788 1192 415 Fracture stress (MPa) 20.1 19.0 16.8 19.1 18.6 17.4 14.8 14.1

[0077] The results of Example 3 show that the silica filled mixtures do not have as large a change in tensile properties as observed in the alumina mixtures in Examples 1 and 2 above, and reinforce the surprising results obtained by using alumina fillers with sulfur bridges and silanes with less than 2.4 sulfur moieties.

[0078] The selected combinations of aspects of the disclosed technology correspond to a variety of different embodiments of the present invention. It should be noted that each of the exemplary embodiments presented and discussed herein should not imply limitations on the present subject matter. Features or steps illustrated or described as part of one embodiment may be used in combination with aspects of another embodiment to produce yet another embodiment. In addition, certain features may be interchangeable with similar devices or features that are not explicitly mentioned but perform the same or similar functions.

[0079] The terms "a," "an," and singular forms of words should be considered to include the plural forms of the same words, such that these terms mean that one or more of something is provided. The terms "at least one" and "one or more" are used interchangeably. A range described as "between a and b" includes the values ​​of "a" and "b."

[0080] The citation of any document does not constitute an admission that the document is prior art with respect to any invention disclosed or claimed herein, nor does it constitute an admission that the document, alone or in combination with any other referenced document, teaches, suggests, or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

Claims

1. A rubber composition comprising: Diene rubber elastomer; Reinforced alumina filler; A silane coupling agent having an average of 2.5 or fewer bridging sulfurs, the silane coupling agent not being a blocked mercaptosilane; and Vulcanization system. 2 . The rubber composition according to claim 1 , wherein the silane coupling agent has an average of 2.4 or less bridging sulfurs. 3 . The rubber composition according to claim 1 , wherein the diene rubber elastomer is styrene-butadiene rubber.

4. The rubber composition according to claim 1, wherein the reinforcing aluminum oxide has a 2 / cm 3 Up to 8500m 2 / cm 3 The volume of NSA.

5. The rubber composition according to any one of the preceding claims, wherein the silane coupling agent is Si75 or Si266. 6 . The rubber composition according to claim 1 , further comprising an accelerator. 7 . The rubber composition according to claim 1 , further comprising an antioxidant. 8 . The rubber composition according to claim 1 , further comprising an antiozonant.

9. The rubber composition according to any one of claims 1 to 4, wherein the reinforcing alumina filler is present in an amount ranging from 80 phr to 185 phr.

10. The rubber composition according to claim 3, wherein the reinforcing aluminum oxide has a 2 / cm 3 Up to 8500m 2 / cm 3 The volume of NSA. The rubber composition according to claim 10 , wherein the silane coupling agent is Si75 or Si266. 12 . The rubber composition according to claim 11 , further comprising an accelerator. 13 . The rubber composition according to claim 12 , further comprising an antioxidant.

14. The rubber composition of claim 13, wherein the reinforcing alumina filler is present in an amount ranging from 80 phr to 185 phr.

15. A tire comprising the rubber composition according to any one of the preceding claims.

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