Textile coat rubber composition for a tire and a tire comprising a textile coat rubber composition

Abstract

In accordance with the invention, a textile cord coat composition for a tire comprises from 70 to 90 phr cis 1,4-polyisoprene rubber, from 10 to 30 phr styrene butadiene rubber, from 25 to 45 phr carbon black, the latter comprising between 1 and 6 phr high surface area carbon black having a BET surface area of more than 700 m.sup.2/g. Moreover, the invention is directed to a textile reinforced ply and a tire comprising such a textile cord coat composition.

Claims

1. A textile cord coat rubber composition comprising: from 70 phr to 90 phr of cis 1,4-polyisoprene rubber, wherein the cis 1,4-polyisoprene rubber is comprised of natural rubber and synthetic polyisoprene rubber, and wherein the portion of natural rubber is higher than the portion of synthetic polyisoprene rubber, from 10 phr to 30 phr of styrene-butadiene rubber, from 25 phr to 45 phr of carbon black, from 1 phr to 10 phr of silica, and from 0.1 phr to 5 phr of a carbon black coupling agent of the structural formula: ##STR00006## wherein R.sup.1 and R.sup.2 can be the same or different and represent hydrogen atoms or an alkyl group, alkenyl group or alkynyl group containing from 1 to 20 carbon atoms; and wherein M.sup.+ represents a sodium ion, a potassium ion, or a lithium ion, wherein said composition is further comprised of a resin at a level which is within the range of 4 phr to 10 phr, wherein the resin is a combination of carbamid acid butyl ester and hexamethoxymethylmelamine, wherein the carbon black includes a conventional carbon black of one or more ASTM grades selected from the group consisting of N110, N121, N134, N220, N231, N234, N242, N293, N299, N315, N326, N330, N332, N339, N343, N347, N351, N358, N375, N539, N550, N582, N630, N642, N650, N683, N754, N762, N765, N774, N787, N907, N908, N990, and N991, and from 1 phr to 10 phr of a high surface area carbon black having a BET surface area of more than 700 m.sup.2/g.

2. The textile cord coat rubber composition of claim 1 wherein the cis 1,4-polyisoprene rubber is present at a level which is within the range of 75 phr to 90 phr, wherein the styrene-butadiene rubber is present at a level which is within the range of 10 phr to 25 phr, wherein the carbon black is present at a level which is within the range of 25 phr to 40 phr, and wherein the carbon black includes from 2 phr to 5 phr of the high surface area carbon black.

3. The textile cord coat rubber composition of claim 1, wherein the high surface area carbon black has a BET surface area which is within the range of 900 m.sup.2/g to 1500 m.sup.2/g; and wherein the high surface area carbon black has an average particle size which is within the range of 20 nm to 40 nm.

4. The textile cord coat rubber composition of claim 1, wherein the high surface area carbon black has an oil absorption value of more than 300 ml/100 g.

5. The textile cord coat rubber composition of claim 1, wherein R.sup.1 and R.sup.2 represent hydrogen atoms and wherein M.sup.+ represents a potassium ion.

6. The textile cord coat rubber composition of claim 1, wherein the carbon black coupling agent is present at a level which is within the range of 0.5 phr to 3 phr.

7. The textile cord coat rubber composition of claim 1, wherein said composition is further comprised of 3 phr to 7 phr of sulfur.

8. The textile cord coat rubber composition of claim 1, wherein said resin is present in the composition at a level which is within the range of 5 phr to 8 phr.

9. The textile cord coat rubber composition of claim 1, wherein said composition is further comprised of a methylene donor and a methylene acceptor, and wherein the weight ratio of the methylene donor to the methylene acceptor is within the range of 1:3 to 3:1.

10. The textile cord coat rubber composition of claim 9, wherein the methylene acceptor is of the chemical structural formula: ##STR00007## and wherein the methylene acceptor is present at a level which is within the range of 0.1 phr to 10 phr, and wherein the methylene donor is of the chemical structural formula: ##STR00008## wherein X represents an alkyl group having from 1 to 8 carbon atoms, and wherein R, R.sup.1, R.sup.2, R.sup.3, and R.sup.4 can be the same or different and are individually selected from the group consisting of hydrogen atoms, alkyl groups having from 1 to 8 carbon atoms, —CH.sub.2OX groups or their condensation products.

11. The textile cord coat rubber composition of claim 1 wherein the carbon black coupling agent is present in the textile cord coat rubber composition at a level which is within the range of 0.5 phr to 3 phr.

12. The textile cord coat rubber composition of claim 1, wherein R.sup.1 and R.sup.2 represent hydrogen atoms and wherein M.sup.+ represents a lithium ion.

13. A textile reinforced ply which is comprised of a textile cord coat rubber composition and a plurality of parallel reinforcing textile cords which are embedded in the textile cord coat rubber composition, wherein textile cord coat rubber composition is comprised of from 70 phr to 90 phr of cis 1,4-polyisoprene rubber, wherein the cis 1,4-polyisoprene rubber is comprised of natural rubber and synthetic polyisoprene rubber, and wherein the portion of natural rubber is higher than the portion of synthetic polyisoprene rubber, from 10 phr to 30 phr of styrene-butadiene rubber, from 25 phr to 45 phr of carbon black, from 1 phr to 10 phr of silica, and from 0.1 phr to 5 phr of a carbon black coupling agent of the structural formula: ##STR00009## wherein R.sup.1 and R.sup.2 can be the same or different and represent hydrogen atoms or an alkyl group, alkenyl group or alkynyl group containing from 1 to 20 carbon atoms; and wherein M.sup.+ represents a sodium ion, a potassium ion, or a lithium ion, wherein said composition is further comprised of a resin at a level which is within the range of 4 phr to 10 phr, wherein the resin is a combination of carbamid acid butyl ester and hexamethoxymethylmelamine, and wherein the carbon black includes a conventional carbon black of one or more ASTM grades selected from the group consisting of N110, N121, N134, N220, N231, N234, N242, N293, N299, N315, N326, N330, N332, N339, N343, N347, N351, N358, N375, N539, N550, N582, N630, N642, N650, N683, N754, N762, N765, N774, N787, N907, N908, N990, and N991, and from 1 phr to 10 phr of a high surface area carbon black having a BET surface area of more than 700 m.sup.2/g.

14. The textile reinforced ply of claim 13, wherein the rubber composition is further comprised of a methylene donor and a methylene acceptor, wherein the weight ratio of the methylene donor and the methylene acceptor is within the range of 1:3 to 3:1.

15. The textile reinforced ply of claim 14 wherein the methylene acceptor is of the chemical structural formula: ##STR00010## and wherein the methylene acceptor is present at a level which is within the range of 0.1 phr to 10 phr, and the methylene donor is of the chemical structural formula: ##STR00011## wherein X represents an alkyl group having from 1 to 8 carbon atoms, and wherein R, R.sup.1, R.sup.2, R.sup.3, and R.sup.4 can be the same or different and are individually selected from the group consisting of hydrogen atoms, alkyl groups having from 1 to 8 carbon atoms, —CH.sub.2OX groups or their condensation products.

16. The textile reinforced ply of claim 13 wherein the textile reinforced ply is a carcass ply, a belt ply, an overlay ply or a ply strip.

17. A pneumatic tire which is comprised of a toroidal-shaped carcass with an outer circumferential tread, two spaced beads, at least one ply as specified in claim 13, wherein the textile reinforced ply extends from bead to bead, and sidewalls extending radially from and connecting said tread to said beads, and wherein said tread is adapted to be ground-contacting.

18. A pneumatic tire which is comprised of a toroidal-shaped carcass with an outer circumferential tread, two spaced beads, and sidewalls extending radially from and connecting said tread to said beads, wherein said tread is adapted to be ground-contacting, and wherein the pneumatic tire is further comprised of a reinforcing ply as specified in claim 16.

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 drawings.

(2) FIG. 1 is a schematic cross section of a tire comprising amongst others belt plies and carcass plies comprising the rubber composition in accordance with an embodiment of the invention.

(3) FIG. 2 is a schematic cross section of a ply comprising textile cords and textile cord coat material in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(4) 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 metal wire and/or textile cords. 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.

(5) 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 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.

(6) The schematic cross-section of FIG. 2 shows a ply, e.g. a carcass, belt or overlay ply 9′ which comprises a plurality of cords 15 reinforcing the rubber composition material/textile coat 20. Typically, such a ply is made in a textile calender in which a textile, or in other words a textile sheet, is coated from both sides with a layer or sheet of rubber composition 20. Such methods are well known to the person skilled in the art of tire building. After curing, the textile cords 15 are embedded in the rubber composition 20, reinforcing the same.

(7) Cords 15 may also be dipped in dipping solutions or emulsions for better adhesion properties as known in the art. A dip is not shown here in FIG. 2.

(8) While the schematic drawing of FIG. 2 indicates nine cords, the number of cords per ply could be different, in particular higher such as from 10 to 40, or from 15 to 35). The invention could also be used in a ply strip comprising the rubber composition, with the strip comprising less than 9 parallel cords.

(9) A preferred example of a rubber composition according to the invention is shown in Table 1 in comparison with a Control Sample. Both compositions include the same content of natural rubber, synthetic polyisoprene and styrene butadiene rubber (SBR). Likewise, both samples comprise at least 30 phr conventional carbon black and small amounts of precipitated silica. However, in particular the silica is not deemed to be essential for the invention. In particular, the amount of silica is preferably below 10 phr. Both compositions comprise a carbon black to natural rubber coupling agent comprising on the one hand amino groups for coupling the agent to the carbon black and on the other hand double bonds of an olefinic group or part of the agent. Both compositions comprise also a reactive resin system for enhancing adhesion of the rubber to the cords. Oil has been added by the utilized SBR which is oil extended by TDAE oil. Apart from typical amounts of antidegradants (e.g. an antioxidizing agent), the compositions comprise a cure package having about 3 phr zinc oxide, about 3 phr stearic acid, about 1 phr accelerator and about 3 phr sulfur.

(10) As an important difference, the Inventive Example comprises 3 phr high surface area carbon black, with a BET surface area of about 1000 m.sup.2/g. The average particle size of the carbon black is at about 30 nm. The oil adsorption number, which is indicating the high structure of the high surface area carbon black, is at about 420 ml/100 g. Moreover, the high surface area carbon black is also electrically conductive.

(11) TABLE-US-00001 TABLE 1 Parts by weight (phr) Material Control Inventive Example Natural rubber 70 70 Synthetic Polyisoprene 12.5 12.5 SBR.sup.1 17.5 17.5 Carbon Black 33 30 Precipitated Silica 3 3 High Surface Area Carbon Black.sup.2 0 3 Carbon Black Coupling agent.sup.3 1 1 Resin.sup.4 6.5 6.5 Zinc Oxide 3 3 Oil.sup.5 6.5 6.5 Antidegradants 1 1 Stearic Acid 3 3 Accelerator.sup.6 1 1 Sulfur 3 3 .sup.1TDAE oil extended styrene butadiene rubber .sup.2Conductive carbon black as Printex XE2-B ™ from the Carycompany .sup.3Sodium (2Z)-4-[(aminophenyl)amino]-4-oxo-2-butanoate as Sumilink ® 200 carbon black coupling agent from Sumitomo Chemical Co., Ltd. .sup.4Reactive resin system comprising a carbamid acid butyl ester and a hexamethoxymethylmelamine. .sup.5TDAE oil from the extended SBR .sup.6Sulfur cure accelerators as sulfenamide

(12) Table 2 discloses mechanical test results for the Control composition and the Example composition disclosed in Table 1. The electrically conductive carbon black used in the Inventive Example improves slightly the stiffness over the Control Sample. For instance, the Shore A hardness has increased slightly and the same applies for G′ at low strain. The rebound value has slightly decreased but is still deemed at an acceptable level. The loss factor tangent delta did essentially not change. Modulus values are a bit higher which applies also to tensile strength. Elongation at break results are lower in the Inventive Example than in the Control.

(13) While the changes in the above-mentioned values are in the order of 10% or even considerably lower, the inventive composition shows a remarkable change in the tear strength which has improved by about 72% over the control. Moreover, the tear strength value of the Control is deemed below an acceptable threshold level of about 5 N/mm (in particular when considering overlay plies) whereas the Inventive Example is almost 50% above said crucial threshold.

(14) TABLE-US-00002 TABLE 2 Test/Property Units Control Inventive Example Shore A hardness (23° C.) .sup.a — 52.1 53.9 Rebound (23° C.) .sup.b % 66.0 64.6 G′ (1%) c MPa 0.7 0.8 Tan delta (10%) .sup.c — 0.05 0.05 Modulus (100%) .sup.d MPa 1.4 1.5 Modulus (200%) .sup.d MPa 3.2 3.8 Modulus (300%) .sup.d MPa 6.1 7.3 Elongation at break .sup.d % 544 537 Tensile strength .sup.d MPa 14.8 16.4 Tear Strength .sup.e N/mm 4.3 7.4 .sup.a Shore A hardness measured according to ASTM D2240 .sup.b Rebound measured on a Zwick Roell ™ 5109 rebound resilience tester according to DIN 53512/ASTM D1054 at given temperature .sup.c Data obtained with an RPA 2000 ™ Rubber Process Analyzer of Alpha Technologies based on ASTM D5289. .sup.d Ring sample test based on ASTM D412 and DIN 53504, percentages are percentages of elongation, respectively strain; tensile strength is stress at break; elongation is elongation at break in % .sup.e Strebler tear strength test according to DIN 53539

(15) The amounts of materials are usually expressed in parts of material per 100 parts of rubber by weight (phr).

(16) 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.

(17) 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.