Body Ply Skim Layer

Abstract

A body ply skim layer in which a reinforcing ply is embedded, arranged at a distance T from an outer surface of the body ply skim layer and at a distance B from an inner surface of the body ply skim layer, such as to define an asymmetry index AT equal to 100×(T−B/T+B). The asymmetry index AT is greater than −100 and less than 0.

Claims

1-9. (canceled)

10. A pneumatic tire comprising: a body ply skim layer comprising a single rubber compound and in which a reinforcing ply is embedded; wherein said reinforcing ply is arranged at a first distance (T) from an outer surface of the body ply skim layer and at a second distance (B) from an inner surface of the body ply skim layer such as to define an asymmetry index equal to 100×[(T−B)/(T+B)]; wherein said outer surface is directed towards a tread of the pneumatic tire and said inner surface is directed towards an inner cavity of the pneumatic tire; and wherein said asymmetry index is greater than −100 and less than 0.

11. The pneumatic tire of claim 10, wherein said asymmetry index is greater than −85 and less than −30.

12. The pneumatic tire of claim 10, wherein the body ply skim layer has a thickness of between 0.9 and 2.0 millimeters (mm).

13. The pneumatic tire of claim 10, wherein said body ply skim layer is made with a compound comprising polyepihalohydrin rubber; epoxidized natural rubber as a cross-linkable unsaturated chain polymer base; a filler; and a vulcanization system.

14. The pneumatic tire of claim 13, wherein said filler is a material with a lamellar structure.

15. The pneumatic tire of claim 13, wherein the compound comprises: from 70 to 90 parts per hundred parts of rubber (phr) of said polyepihalohydrin rubber; from 5 to 25 phr of said epoxidized natural rubber (E-NR); and from 5 to 25 phr of natural rubber (NR).

16. The pneumatic tire of claim 15, wherein the ratio in phr between E-NR and NR is between 0.2 and 5.0.

17. The pneumatic tire of claim 16, wherein the ratio in phr between E-NR and NR is between 1.0 and 3.0.

18. The pneumatic tire of claim 13, wherein the polyepihalohydrin rubber is a rubber deriving from the epichlorohydrin homopolymer.

19. The pneumatic tire of claim 13, wherein the polyepihalohydrin rubber is a rubber deriving from the epichlorohydrin/allyl-glycidyl ether copolymer.

20. The pneumatic tire of claim 13, wherein the polyepihalohydrin rubber is a rubber deriving from the epichlorohydrin/ethylene oxide copolymer.

21. The pneumatic tire of claim 13, wherein the polyepihalohydrin rubber is a rubber deriving from the epichlorohydrin/ethylene oxide/allyl-glycidyl ether terpolymer.

22. The pneumatic tire of claim 10, wherein: said body ply skim layer directly faces said inner cavity; said pneumatic tire being free of an innerliner layer.

Description

[0022] For a better understanding of the invention, the following examples serve for illustrative and non-limiting purpose with the help of the attached figures, wherein:

[0023] FIG. 1 is a sectional view of a portion of a pneumatic tire according to the invention;

[0024] FIG. 2 is a section of a portion of body ply skim layer according to the invention.

[0025] In FIG. 1 there is indicated, in its entirety with P, a pneumatic tire according to the present invention.

[0026] The pneumatic tire P comprises a tread layer 1 and a body ply skim layer 2 that faces directly an inner cavity 3 of the pneumatic tire P.

[0027] In particular, in the pneumatic tire P, the body ply skim layer 2 faces directly the inner cavity 3 insofar as the presence of the innerliner layer is not envisaged.

[0028] In FIG. 2 there is indicated, in its entirety with 2, a body ply skim layer according to the present invention. The body ply skim layer consists of a single compound 4 and a reinforcing ply 5 accommodated within the single compound 4.

[0029] The body ply skim layer 2 comprises an outer surface E directed towards a tread 1 of the pneumatic tire, and an inner surface I facing the inner cavity 3.

[0030] In FIG. 2 there is indicated with T the distance between the cord 5 and the outer surface E, and with B the distance between the cord 5 and the inner surface I.

EXAMPLES

[0031] Three pneumatic tire were manufactured: the pneumatic tire A represents a comparative example and comprises a body ply skim layer with a thickness equal to 1.2 mm in which a reinforcing ply of PET is embedded, having an AI equal to 0, and an innerliner layer with a thickness equal to 1.0 mm; the pneumatic tire B represents a comparative example and comprises a body ply skim layer with a thickness equal to 1.2 mm in which a reinforcing ply of PET is embedded, having an AI equal to 0, and does not comprise any innerliner layer; the pneumatic tire C represents an example according to the invention and comprises a body ply skim layer with a thickness equal to 1.2 mm in which a reinforcing ply of PET is embedded, having an AI equal to −49, and does not comprise any innerliner layer.

[0032] The pneumatic tires A-C are the same in all respects except for the presence of the innerliner layer and the position of the PET reinforcing ply.

[0033] The body ply skim layer was manufactured using a compound which composition in phr is reported in Table I

TABLE-US-00001 TABLE I A NR 15.0 E-NR 15.0 Polyepihalohydrin rubber 70.0 CB 40.0 Sulfur 2.0 MBTS 0.2 TBBS 0.8

[0034] NR stands for natural rubber that is made of a polymer base composed of natural origin cis-1,4-polyisoprene.

[0035] E-NR stands for epoxidized natural rubber, presenting a degree of epoxidation of 25%.

[0036] The polyepihalohydrin rubber used is a rubber derived from the epichlorohydrin/ethylene oxide/allyl-glycidyl ether terpolymer marketed as T3000 by the company ZEON.

[0037] CB stands for carbon black belonging to the class N6.

[0038] MBTS is the acronym for mercaptobenzothiazole disulfide used as a vulcanization accelerant.

[0039] TBBS is the acronym for N-tert-butyl-2-benzothiazole sulfenamide used as a vulcanization accelerant.

[0040] Preparation of the Compound

[0041] The compound was made according to the standard procedure described below, which is not relevant to the purposes of the present invention.

[0042] (1.sup.st mixing step)

[0043] Before the start of the mixing, a mixer with tangential rotors (commonly called a Banbury) and an internal volume of between 230 and 270 liters was loaded with the polymer bases and the reinforcing filler, reaching a fill factor of between 66-72%.

[0044] The mixer was operated at a speed of between 40-60 revolutions/minute, and the mixture thus formed was discharged once a temperature of between 140-160° C. had been reached.

[0045] (2.sup.nd mixing step)

[0046] The vulcanization system was added to the mixture obtained from the previous step, reaching a fill factor of between 63-67%.

[0047] The mixer was operated at a speed of between 20-40 revolutions/minute, and the mixture thus formed was discharged once a temperature of between 100-110° C. had been reached.

[0048] The pneumatic tires A-C were manufactured by means of an equal vulcanization process.

[0049] Once manufactured, the pneumatic tires were evaluated in terms of the weight of the innerliner+body ply skim (I+BPS) assembly, rolling resistance and Appearance.

[0050] Table II lists the assessments of the parameters described above.

[0051] The Appearance assessments derive from tactile and visual inspections on the part of an operator in the industry.

[0052] The data in relation to the weight are expressed in terms of variation of the weight of the I+BPS assembly of the pneumatic tire A.

[0053] The rolling resistance values are indexed with respect to the relative value of the pneumatic tire A and were detected in accordance with ISO28580 procedure

TABLE-US-00002 TABLE II Pneumatic tire Pneumatic tire Pneumatic tire A B C Weight Variation 0 −495.0 −495.0 I + BPS (g) Rolling 100 98 98 resistance* Appearance PROTRUBERANCES PROTRUBERANCES PROTRUBERANCES NO YES NO

[0054] As is clear from the assessments of Table II, the solution, which is the subject matter of the present invention, offers the great advantage of being able to eliminate the innerliner layer, with the relative advantages in terms of weight and rolling resistance, without thereby provoking the exposure or emergence of the cords of the reinforcing ply. Furthermore, it is important to emphasize that the compound used also ensures the necessary impermeability to air, notwithstanding the lack of an innerliner.