Rubber composition and an article of manufacture comprising a rubber composition

Abstract

In a first aspect of the present invention, a rubber composition is provided, comprising at least one rubber, at least one filler, at least one thermoplastic polymer, wherein the thermoplastic polymer is a poly alkylacrylate, and wherein the alkylacrylate comprises a polycyclic substituent at its single bonded oxygen atom. In another aspect of the invention, an article of manufacture such as a tire, a power transmission belt, a hose, a track, an air sleeve, and a conveyor belt is provided which comprises the rubber composition in accordance with the first aspect.

Claims

1. A rubber composition, the rubber composition comprising: at least one elastomer, at least one filler, at least one thermoplastic polymer, wherein the thermoplastic polymer is a poly alkylacrylate, wherein the glass transition temperature of the poly alkylacrylate is at least 195 C. as measured at a rate of temperature increase of 10 C. per minute, wherein the molar weight Mn of the polyalkylacrylate is at least 20,000 g/mol, and wherein the polyalkylacrylate consists of repeat units having the structural formula: ##STR00005## wherein n is an integer which represents the number of the number of repeat units in the poly alkylacrylate; wherein R.sub.1 represents the alkyl group; and wherein R.sub.2 represents a polycyclic hydrocarbon group.

2. The rubber composition of claim 1, wherein R.sub.1 is a member selected from the group consisting of CH.sub.3 and C.sub.2H.sub.5.

3. The rubber composition of claim 1, wherein R.sub.2 is a bicyclic substituent or a tricyclic substituent.

4. The rubber composition of claim 1, wherein R.sub.2 is a hydrocarbon substituent comprising at least seven carbon atoms, with at least five of the carbon atoms cyclically arranged.

5. The rubber composition of claim 1, wherein the poly alkylacrylate of: consists of poly(isobornyl methacrylate).

6. The rubber composition of claim 1, wherein the molar weight Mn of the poly alkylacrylate is less than 2,000,000 g/mol, and wherein the polydispersity index Mw/Mn of the poly alkylacrylate is at least 1.5.

7. The rubber composition of claim 1, wherein the glass transition temperature T.sub.g of the poly alkylacrylate ranges from 195 C. to 250 C.

8. The rubber composition of claim 1, wherein the rubber composition comprises: 100 phr of the elastomer, from 20 to 120 phr of the filler, and from 5 to 50 phr of the poly alkylacrylate.

9. The rubber composition of claim 1, wherein the filler is a pre-silanized silica.

10. The rubber composition of claim 1, wherein the elastomer is one or more of: styrene butadiene rubber, polybutadiene, solution polymerized styrene butadiene rubber, emulsion polymerized styrene butadiene rubber, natural rubber and synthetic polyisoprene.

11. The rubber composition of claim 1, wherein the rubber composition comprises from 10 phr to 40 phr of the poly alkylacrylate.

12. The rubber composition of claim 1, wherein the wherein the glass transition temperature of the poly alkylacrylate is within the range of 210 C. to 250 C. as measured at a rate of temperature increase of 10 C. per minute.

13. The rubber composition of claim 1, wherein the polyalkylacrylate consists of repeat units of the structural formula: ##STR00006##

14. The rubber composition of claim 1 wherein the poly alkylacrylate is present in the rubber composition at a level which is within the range of 15 phr to 25 phr.

15. The rubber composition of claim 1, wherein the poly alkylacrylate consists of poly(adamantyl methacrylate).

16. A tire which includes a tread, an innerliner, a belt structure, a carcass ply, two sidewalls, two bead regions, two beads and two bead filler apexes, wherein the bead filler apexes are comprised of the rubber composition of claim 1.

17. A tire which includes a tread, an innerliner, a belt structure, a carcass ply, two sidewalls, two bead regions, two beads, two bead filler apexes, and two flippers, wherein the flippers are comprised of the rubber composition of claim 1.

18. A tire which includes a tread, an innerliner, a belt structure, a carcass ply, two sidewalls, two bead regions, two beads, two bead filler apexes, and two chippers, wherein the chippers are comprised of the rubber composition of claim 1.

19. A tire which includes a tread, an innerliner, a belt structure, a carcass ply, two sidewalls, two bead regions, two beads, two bead filler apexes, two flippers, and two chippers, wherein the apexes, flippers, and chippers are comprised of the rubber composition of claim 1.

20. The tire of claim 19, wherein the polyalkylacrylate consists of repeat units of the structural formula: ##STR00007##

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The structure, operation and advantages of the invention will become more apparent upon contemplation of the following description taken in conjunction with the accompanying drawing, wherein:

(2) FIG. 1 shows a schematic cross section through an example tire.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) FIG. 1 is a schematic cross-section of a tire 1. The tire 1 has a tread 10, an inner liner 13, a belt structure comprising four belt plies 11, a carcass ply 9, two sidewalls 2, and two bead regions 3 comprising bead filler apexes 5 and beads 4. The example tire 1 is suitable, for example, for mounting on a rim of a vehicle, e.g. a truck or a passenger car. As shown in FIG. 1, the belt plies 11 may be covered by an overlay ply 12. The carcass ply 9 includes a pair of axially opposite end portions 6, each of which is associated with a respective one of the beads 4. Each axial end portion 6 of the carcass ply 9 may be turned up and around the respective bead 4 to a position to anchor each axial end portion 6. One or more of the carcass ply 9, belt plies 11 and overlay ply 12 comprise a rubber composition in accordance with the invention and may have a plurality of substantially parallel reinforcing members made of a fabric material such as polyester, rayon, or similar suitable organic polymeric compounds or made of metal wire. The turned-up portions 6 of the carcass ply 9 may engage the axial outer surfaces of two flippers 8 and axial inner surfaces of two chippers 7. As shown in FIG. 1, the example tread 10 may have four circumferential grooves, each groove essentially defining a U-shaped opening in the tread 10. The main portion of the tread 10 may be formed of one or more tread compounds, which may be any suitable tread compound or compounds.

(4) While the embodiment of FIG. 1 suggests a plurality of tire components including for instance apexes 5, chippers 7, flippers 8 and overlay 12, such components are all not mandatory for the invention. Also, the turned-up end of the carcass ply 9 is not necessary for the invention or may pass on the opposite side of the bead area 3 and end on the axially inner side of the bead 4 instead of the axially outer side of the bead 4. The tire could also have, for instance, more or less than four grooves. It shall be emphasized that the present invention focuses on the use of a thermoplastic polymer which is a poly alkylacrylate in a rubber composition. Thus, the description of FIG. 1 is merely to be understood as an example without necessarily limiting the present invention.

(5) In an example of the invention, a rubber composition, such as in the tire 1, comprises an elastomer, in particular a SSBR, and a filler which may comprise carbon black, silica or combinations thereof. In accordance with the invention, the rubber composition comprises also a thermoplastic polymer which is a poly alkylacrylate, wherein the alkylacrylate comprises a polycyclic substituent at its single bonded oxygen atom.

(6) Table 1 shows three control samples comprising SSBR rubber, filler, oil, stearic acid, antioxidants, waxes, zinc oxide, sulfur as well as curing accelerators. Control Sample 1 comprises no thermoplastic polymer and is mainly reinforced by means of its carbon black filler. In contrast, Control Sample 2 (which is also not in accordance with the present invention) comprises additional 20 phr of polyethylene (PE) which is used for reinforcing purposes. Control Sample 3 comprises silica and silica coupler instead of carbon black but no PE. The Inventive Examples do not comprise PE either. Inventive Example 1 comprises instead of PE 20 phr poly(isobornyl methacrylate) (PIBOMA) having a molecular weight of 50k and Inventive Example 2 comprises instead of PE 20 phr PIBOMA 277k. Inventive Example 3 comprises poly(adamantyl methacrylate) (PADAM) with a molecular weight of 38 k g/mol. Both, PIBOMA and PADAM are supposed to help reinforcing the rubber compound. Inventive Example 4 comprises silica in combination with the PIBOMA 277k.

(7) TABLE-US-00001 TABLE 1 [phr] Control Inventive Material 1 2 3 Example 1 Example 2 Example 3 Example 4 SSBR.sup.1 100 100 100 100 100 100 100 Carbon Black 50 50 0 50 50 50 0 Silica 0 0 65 0 0 0 65 Oil.sup.2 4 4 26 4 4 4 26 PIBOMA 50k.sup.3 0 0 0 20 0 0 0 Coupling 0 0 6.5 0 0 0 6.5 agent.sup.4 PIBOMA 277k.sup.5 0 0 0 0 20 0 20 PADAM 38k.sup.6 0 0 0 0 0 20 0 PE.sup.7 0 20 0 0 0 0 0 Stearic Acid 2 2 3 2 2 2 3 Antioxidants.sup.8 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Waxes 1.5 1.5 0 1.5 1.5 1.5 0 MBT.sup.9 0 0 0.3 0 0 0 0.3 Zinc Oxide 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Sulfur 1.5 1.5 1.1 1.5 1.5 1.5 1.1 Accelerators.sup.10 2.3 2.3 5.5 2.3 2.3 3 5.5 .sup.1Solution styrene butadiene rubber as Sprintan SLR 4602 of Trinseo company .sup.2TDAE oil .sup.3Poly(isobornyl methacrylate) with 50,000 g/mol molecular weight .sup.4Bis-(3-triethyoxysilylpropyl) disulfide .sup.5Poly(isobornyl methacrylate) with 277,000 g/mol molecular weight .sup.6Poly(adamantyl methacrylate) with 38,000 g/mol molecular weight .sup.7Ultra-high molecular weight polyethylene (UHMWPE) with 4,700,000 g/mol molecular weight .sup.8as Phenylene diamine .sup.9as 2-Mercaptobenzothiazole .sup.10as Sulfenamides and diphenylguanidine

(8) Table 2 shows measured storage modulus (E) values for the compositions listed already in Table 1, wherein the storage modulus can be considered as a stiffness indicator. In particular, Table 2 shows an improved reinforcement, especially in high temperature regions, for instance at 150 C. or above. The samples with only carbon black or silica (and no thermoplastic reinforcement) have storage module values below all other materials shown which comprise a thermoplastic material. When considering the storage modulus in dependency of the temperature of the polyethylene-comprising composition, the reinforcement is relatively good until the softening point of the polyethylene but drops then considerably around its melting point of about 135 C. which can be seen in the 150 C. and higher value in Table 2. The poly(isobornyl alkylacrylate) and poly(adamantyl alkylacrylate) Inventive Examples do not show that sharp dropping behavior. In particular, the storage modulus value drops for the PE sample by almost 40% from 100 C. to 150 C., whereas the drop for the Inventive Examples is at about 10% or less in the same temperature range. Moreover, the storage modulus at 150 C. and above is higher for the Inventive Examples 1, 2, 3 and 4 than the values of Control 2, i.e. the PE sample.

(9) TABLE-US-00002 TABLE 2 Storage Modulus E [MPa]* Inventive Control Example Example Example Example Temperature 1 2 3 1 2 3 4 30 C. 15.0 26.5 12.5 17.7 26.0 21.5 14.8 50 C. 12.0 20.0 10.7 14.3 20.5 17.0 12.9 100 C. 9.5 13.3 8.9 10.8 15.1 13.7 10.8 150 C. 8.9 8.6 8.1 9.7 13.6 13.0 10.0 180 C. 8.6 8.1 7.8 9.6 12.7 12.8 9.4 *Dynamic Mechanical Thermal Analysis (DMTA) measurements have been carried out for cured compounds/compositions on films (typically length width thickness = 10 6 2 (mm)) with a DMA 242 C model (Netzsch, Germany) operating in tension mode (strain between 0.05 and 0.07%, pretension: 10.sup.2 N). Experiments were performed at 1 Hz frequency with a heating rate of 2 C. min.sup.1 from 180 to 180 C.

(10) Below Table 3 shows glass transition temperatures for the thermoplastic polymers used in the compositions discussed in the context of Tables 1 and 2 (i.e. not the glass transition temperature of the whole rubber compositions). Glass transition temperatures of the thermoplastic polymers used in the Inventive Examples are significantly higher than the softening point of the UHMWPE used in control sample 2 which is at about 135 C.

(11) TABLE-US-00003 TABLE 3 Glass Transition Temperature Tg Inventive Inventive Inventive Inventive Example 1 Example 2 Example 3 Example 4 195 C. 195 C. 235 C. 195 C.

(12) Variations in the present invention are possible in light of the provided description. While certain representative embodiments, examples and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the invention. It is, therefore, to be understood that changes may be made in the particular example embodiments described which will be within scope of the invention as defined by the following appended claims.

(13) In any case, the above described embodiments and examples shall not be understood in a limiting sense. In particular, the features of the above embodiments may also be replaced or combined with one another.