COMPOUND FOR BODY PLY SKIM

Abstract

A rubber compound for body ply skim comprising: —a mix of rubber consisting of (i) Epoxidized Natural Rubber acting as polymer base with a cross-linkable unsaturated chain; (ii) Natural Rubber acting as polymer base with a cross-linkable unsaturated chain; (iii) Polyepihalohydrin rubber, —a filler material, and—a vulcanization system; The compound comprises: 70 to 90 phr of said Polyepihalohydrin rubber; 5 to 25 phr of said Epoxidized Natural Rubber (E-NR); and 5 to 25 phr of said Natural Rubber (NR); the phr ratio between E-NR and NR ranging from 0.2 to 5.0.

Claims

1-9. (canceled)

10. A rubber compound for a body ply skim comprising: a mixture of rubber consisting of: Epoxidized Natural Rubber (E-NR) acting as polymer base with a cross-linkable unsaturated chain, Natural Rubber (NR) acting as polymer base with a cross-linkable unsaturated chain, and Polyepihalohydrin rubber; a filler material; a vulcanization system; and wherein the compound comprises 70 phr to 90 phr of the Polyepihalohydrin rubber, 5 phr to 25 phr of the E-NR, and 5 phr to 25 phr of the NR, with a phr ratio between the E-NR and the NR ranging from 0.2 to 5.0.

11. The rubber compound of claim 10, wherein the phr ratio between the E-NR and the NR ranges from 1.0 to 3.0.

12. The rubber compound of claim 10, wherein the Polyepihalohydrin rubber comprises a rubber deriving from a homopolymer of epichlorohydrin, an epichlorohydrin/glycidyl-allyl ether copolymer, an epichlorohydrin/Ethylene-oxide copolymer, or an epichlorohydrin/ethylene-oxide/glycidyl-allyl-ether terpolymer.

13. The rubber compound of claim 10, further comprising 0 phr to 40 phr of an inert material with a laminated structure.

14. The rubber compound of claim 13, wherein the inert material with the laminated structure has a diameter ranging from 0.2 mm to 2 mm and an aspect ratio ranging from 5 to 30.

15. The rubber compound of claim 14, wherein the inert material with the laminated structure has an aspect ratio ranging from 8 to 20.

16. The rubber compound of claim 13, wherein the inert material with the laminated structure includes at least one of kaolin, clay, mica, feldspar, silica, graphite, bentonite, or alumina.

17. The rubber compound of claim 10, wherein the vulcanization system comprises sulfur and one or more accelerator agents.

18. The rubber compound of claim 17, wherein the one or more accelerator agents include at least one of mercaptobenzothiazol-disulfide (MBTS) or n-tert-butyl-2-benzothiazyl sulfenamide (TBBS).

19. The rubber compound of claim 10, further comprising carbon black (CB).

20. A body ply skim comprising a rubber compound, the rubber compound including: a mixture of rubber consisting of: Epoxidized Natural Rubber (E-NR) acting as a polymer base with a cross-linkable unsaturated chain, Natural Rubber (NR) acting as a polymer base with a cross-linkable unsaturated chain, and Polyepihalohydrin rubber; a filler material; and a vulcanization system, wherein the compound comprises 70 phr to 90 phr of the Polyepihalohydrin rubber, 5 phr to 25 phr of the E-NR, and 5 phr to 25 phr of the NR, with a phr ratio between the E-NR and the NR ranging from 0.2 to 5.0.

21. A tire comprising: a carcass located within the tire; an innerliner layer configured to contain air in the carcass such that the carcass remains under pressure; a body ply skim in contact with the innerliner layer and configured to provide support to the carcass; the body ply skim comprising a rubber compound, the rubber compound including: a mixture of rubber consisting of: Epoxidized Natural Rubber (E-NR) acting as a polymer base with a cross-linkable unsaturated chain, Natural Rubber (NR) acting as a polymer base with a cross-linkable unsaturated chain, and Polyepihalohydrin rubber; a filler material; and a vulcanization system, wherein the compound comprises 70 phr to 90 phr of the Polyepihalohydrin rubber, 5 phr to 25 phr of the E-NR, and 5 phr to 25 phr of the NR, with a phr ratio between the E-NR and the NR ranging from 0.2 to 5.0.

22. The tire of claim 21, wherein the rubber compound further comprises 70 phr to 90 phr of the Polyepihalohydrin rubber, 5 phr to 25 phr of the E-NR, and 5 phr to 25 phr of the NR, with a phr ratio between the E-NR and the NR ranging from 0.2 to 5.0.

23. The tire of claim 22, wherein the phr ratio between the E-NR and the NR ranges from 1.0 to 3.0.

24. The tire of claim 23, wherein the Polyepihalohydrin rubber comprises a rubber deriving from a homopolymer of epichlorohydrin, an epichlorohydrin/glycidyl-allyl ether copolymer, an epichlorohydrin/ethylene-oxide copolymer, or an epichlorohydrin/ethylene-oxide/glycidyl-allyl-ether terpolymer

25. The tire of claim 23, wherein the rubber compound further includes 0 phr to 40 phr of an inert material with a laminated structure

26. The tire of claim 25, wherein the inert material with the laminated structure has a diameter ranging from 0.2 mm to 2 mm and an aspect ratio ranging from 5 to 30.

27. The tire of claim 25, wherein the inert material with the laminated structure includes at least one of kaolin, clay, mica, feldspar, silica, graphite, bentonite, or alumina.

28. The tire of claim 21, wherein the vulcanization system comprises sulfur and one or more accelerator agents.

Description

EXAMPLES

[0026] Eight compounds were produced, four of them being comparison compounds (Comp.1-4) and four of them being compounds according to the invention (A-D).

[0027] The four comparison compounds (Comp.1-4) can be divided into: a first comparison compound (Comp.1) representing a type of compound generally used for the preparation of innerliner layers; a second compound (Comp.2) representing a type of compound generally used for the preparation of body ply skims; a third and a fourth compound (Comp.3 and Comp.4) using Polyepihalohydrin, E-NR and an inert material with a laminated structure in quantities that are different from the ones set forth in this invention.

[0028] The four compounds according to the invention (A—D) differ from one another in the relative quantity of Polyepihalohydrin rubber, Epoxidized Natural Rubber and Natural Rubber, always within the ranges and under the conditions set forth in the invention, and in the presence or absence of the inert material with a laminated structure.

[0029] The comparison compounds Comp.1 and Comp.2 fulfil the aim of checking whether the body ply skim compounds of the invention have features of impermeability to Oxygen and of brittleness which can be compared with the ones of common innerliner layer and body ply skim layers, respectively; the comparison compounds Comp.3 and Comp.4 fulfil the aim of checking the relevance of the relative quantities among the Epoxidized natural rubber, the Polyepihalohydrin rubber and the inert material with a laminated structure.

[0030] Preparation of the Compounds

[0031] The compounds were produced with a standard procedure explained below, which is not relevant for the purposes of the invention.

[0032] (1.sup.st Mixing Step)

[0033] The polymer bases, the reinforcing filler and the filler material (if present, also with the material with a laminated structure) were introduced into a mixer with tangential rotors (commonly known as Banbury) and with an inner volume ranging from 230 to 270 litres before the beginning of the mixing, thus reaching a filling factor ranging from 66 to 72%.

[0034] The mixer was operated at a speed ranging

[0035] from 40 to 60 revolutions/minute and the mixture resulting therefrom was removed after having reached a temperature ranging from 140 to 160° C.

[0036] (2.sup.nd Mixing Step)

[0037] The vulcanization system was added to the mixture obtained from the preceding step, thus reaching a filling factor ranging from 63 to 67%.

[0038] The mixer was operated at a speed ranging from 20 to 40 revolutions/minute and the mixture resulting therefrom was removed after having reached a temperature ranging from 100 to 110° C.

[0039] Composition of the Compounds

[0040] Tables I and II show the phr compositions of the eight compounds described above.

TABLE-US-00001 TABLE I Comp. 1 Comp. 2 Comp. 3 Comp. 4 SBR — 35.0 — — Br-IIR 80.0 — — — NR 20.0 65.0 — — E-NR — — 65.0 35.0 Polyepihalohydrin rubber — — 35.0 65.0 CB 50.0 40.0 40.0 40.0 CaCO3 40.0 — — — Laminated clay — — 50.0 50.0 Sulfur  1.0  2.0  2.0  2.0 MBTS  1.5  0.2  0.2  0.2 TBBS —  0.8  0.8  0.8

TABLE-US-00002 TABLE II A B C D NR 15.0 5.0 15.0 15.0 E-NR 15.0 10.0 15.0 15.0 Polyepihalohydrin rubber 70.0 85.0 70.0 70.0 CB 40.0 40.0 40.0 40.0 Laminated clay — — 10.0 20.0 Sulfur 2.0 2.0 2.0 2.0 MBTS 0.2 0.2 0.2 0.2 TBBS 0.8 0.8 0.8 0.8

[0041] SBR is a polymer base obtained by means of an emulsion or solution polymerization process with a styrene content ranging from 20 to 45% and an oil content ranging from 0 to 30%;

[0042] Br-IIR stands for Bromobutyl rubber.

[0043] NR stands for Natural Rubber, consisting of a polymer base made up of 1,4-cis Polyisoprene rubber of natural origin.

[0044] E-NR stands for Epoxidized Natural Rubber, having a degree of epoxidation amounting to 25%.

[0045] The Polyepihalohydrin rubber used is a rubber deriving from the Epichlorohydrin/Ethylene oxide/Glycidyl-allyl ether terpolymer, sold with the name T3000 by the company ZEON.

[0046] CB stands for carbon black belonging to the N6 class.

[0047] The laminated Clay used is a mineral filler produced and sold by BASF under the name ASP® NC X-1.

[0048] MBTS stands for Mercaptobenzothiazol-disulfide used as vulcanization accelerator.

[0049] TBBS stands for N-tert-butyl-2-benzothiazyl sulfenamide used as vulcanization accelerator.

[0050] Results of the Lab Tests

[0051] The compounds described above were used to produce respective samples, which were subjected to assessment tests in order to check the properties in terms of brittleness and in terms of impermeability to Oxygen.

[0052] In addition, the samples were subject to ply to rubber adhesion test in order to verify if the solution of the invention affects this property.

[0053] The Oxygen impermeability test was carried out on materials with a thickness of 0.7 mm and using a conventional apparatus, such as MOCON® OX-TRAN® (model 2/61). The values were measured at a temperature of 25° C.

[0054] The brittleness test was carried out according to ISO-812.

[0055] The adhesion of the compounds to the reinforcing ply was estimated as percentage of ply still covered with rubber after the separation of the two parts of the ply-rubber assembly through application of a load. The ply used in the text is made of PET.

[0056] For an easier interpretation of the results obtained, in Tables III and IV the values are expressed in a form indexed to the results of the comparison compound generally used for the production of an innerliner layer (Comp.1).

[0057] As to the brittleness and Oxygen impermeability values shown in Tables III and IV, it should be pointed out that the lower the value shown therein, the better the feature.

[0058] The ply-rubber adhesion value of the comparison compound Comp.1 is not shown in the table as said compound, being used for an innerliner layer and not for a body ply skim layer, does not have this feature.

TABLE-US-00003 TABLE III Comp. 1 Comp. 2 Comp. 3 Comp. 4 Brittleness 100 40 194 261 Oxygen impermeability 100 720 130 108 Ply-rubber adhesion — 55 100 100

TABLE-US-00004 TABLE IV A B C D Brittleness 96 114 126 156 Oxygen impermeability 180 140 120 107 Ply-rubber adhesion 100 100 100 100

[0059] Based on the data shown in tables III and IV, the compounds according to the invention feature a better compromise between the Oxygen impermeability values and the brittleness values.

[0060] The values of the compounds according to the invention C and D prove how the presence of the inert material with a laminated structure can further improve the performances of the compounds in terms of impermeability, without jeopardizing the mechanical features (brittleness).

[0061] The values concerning the body ply skim show above, ensuring an advantageous combination of brittleness and impermeability, are such as to allow the thickness of the innerliner layer to be significantly reduced.

[0062] By so doing, the thickness of the innerliner layer can be remarkably reduced, ensuring, anyway, both the necessary impermeability to Oxygen, so that the latter does not reach the other parts of the tire, thus causing the known degradation phenomena thereof, and the necessary strength, so as not to jeopardize the durability of the tire.

[0063] The values of Table III concerning the comparison compounds Comp.3 and Comp.4 prove how the sole combination of Epoxidized rubber and Polyepihalohydrin rubber, even in the presence of the inert material with a laminated structure, cannot ensure the advantages of the compounds according to the invention, if the conditions imposed by the invention are not observed.

[0064] Finally, a further advantage of the invention lies in the fact said Polyepihalohydrin rubber can be obtained from renewable sources. As a matter of fact, processes were recently conceived, which are capable of producing Epichlorohydrin from Glycerol of natural origin. Therefore, by so doing, manufacturers will have the chance to produce body ply skim portions with a significantly lower environmental impact than the ones of the prior art.

[0065] In conclusion, from the data shown in table IV is clear that the solution of the present invention does not worsens ply-rubber adhesion.