Body ply skim compound

Abstract

Body ply skim compound comprising a cross-linkable unsaturated chain polymer base, a filler material, a vulcanization system and a polyepihalohydrin rubber. The compound comprises epoxidized natural rubber as a cross-linkable unsaturated chain polymer base and a laminated structure material as a filler material.

Claims

1. A body ply skim compound comprising a cross-linkable unsaturated chain polymer base, a filler material and a vulcanization system; said compound being characterized by comprising: (a) polyepihalohydrin rubber; (b) epoxidized natural rubber as the cross-linkable unsaturated chain polymer base; and (c) a laminated structure material as a filler material; and said compound being characterized in that said cross-linkable unsaturated chain polymer base consists exclusively of epoxidized natural rubber.

2. The body ply skim compound according to claim 1, characterized in that said polyepihalohydrin rubber is a rubber deriving from epichlorohydrin homopolymer, from epichlorohydrin/allyl-glycidyl ether copolymer, from epichlorohydrin/ethylene oxide copolymer or from epichlorohydrin/ethylene oxide/allyl-glycidyl ether terpolymer.

3. The body ply skim compound according to claim 1, characterized in that said laminated structure material has a diameter between 0.2 and 2 mm and an aspect ratio between 5 and 30.

4. The body ply skim compound according to claim 3, characterized in that said laminated structure material has an aspect ratio between 8 and 20.

5. The body ply skim compound according to claim 1, characterized in that said laminated structure material is comprised within the group made up of kaolin, clay, mica, feldspar, silica, graphite, bentonite and alumina.

6. The body ply skim compound according to claim 1, characterized by comprising from 30 to 50 phr of epoxidized natural rubber, from 50 to 70 phr of polyepihalohydrin rubber and from 40 to 60 phr of said laminated structure material.

7. A body ply skim portion, characterized in that it is made with the compound according to claim 1.

8. A tire characterized by comprising a body ply skim portion according to claim 7.

Description

EXAMPLES

(1) Six compounds were made, two according to the dictates of the present invention (A and B) and four as comparison compounds (Comp.1-4). The compounds made according to the present invention (A and B) differ in the relative amounts of epoxidized natural rubber and polyepihalohydrin rubber. The four comparison compounds (Comp.1-4) differ as follows: a first comparison compound (Comp.1) that represents a type of compound which is generally used for preparing innerliner layers; a second compound (Comp.2) that represents a type of compound commonly used in the preparation of body ply skim; a third compound (Comp.3) that differs from the second compound Comp.2 only in the substitution of the natural rubber with epoxidized natural rubber; a fourth compound (Comp.4) that differs from the third compound Comp.3 in the presence within the polymer base of polyepihalohydrin rubber in place of the SBR rubber.

(2) The purpose of the comparison compounds Comp.1 and Comp.2 is to verify whether the body ply skim compounds, which are object of the present invention, have characteristics of oxygen impermeability and adhesion to the plies that are comparable to those of an innerliner layer and a body ply skim layer respectively.

(3) The purpose of the comparison compounds Comp.3 and Comp.4 is to verify the existence of a synergistic effect between the epoxidized natural rubber, the polyepihalohydrin rubber and the material having a laminated structure.

(4) Preparation of the Compounds

(5) The compounds were made according to the standard procedure described below, which is not relevant to the present invention.

(6) (1.sup.st Mixing Step)

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

(8) The mixer was operated at a speed of 40-60 rpm, and the mixture thus formed was removed once a temperature of 140-160 C. had been reached.

(9) (2.sup.nd Mixing Step)

(10) The vulcanization system was added to the mixture obtained from the previous step, reaching a fill factor of 63-67%.

(11) The mixer was operated at a speed of 20-40 rpm, and the mixture thus formed was removed once a temperature of 100-110 C. had been reached.

(12) Composition of the Compounds

(13) Table I shows the compositions in phr of the six compounds described above.

(14) TABLE-US-00001 TABLE I Comp.1 Comp.2 Comp.3 Comp.4 A B SBR 35.0 35.0 Br-IIR 80.0 NR 20.0 65.0 E-NR 65.0 65.0 65.0 35.0 Polyepihalohydrin 35.0 35.0 65.0 rubber CB 50.0 40.0 40.0 40.0 40.0 40.0 CaCO3 40.0 Laminated clay 50.0 50.0 Sulfur 1.0 2.0 2.0 2.0 2.0 2.0 MBTS 1.5 0.2 0.2 0.2 0.2 0.2 TBBS 0.8 0.8 0.8 0.8 0.8 SBR is a polymer base obtained by means of a polymerization process in an emulsion or in a solution with a styrene content between 20 to 45% and an oil content between 0 and 30%. BR-IIR stands for bromobutyl rubber. NR stands for natural rubber that is made of a polymer base composed of natural origin cis-1,4-polyisoprene. E-NR stands for epoxidized natural rubber, presenting a degree of epoxidation of 25%. The polyepihalohydrin rubber used is a rubber derived from the epichlorohydrin/ethylene oxide/allyl-glycidyl ether terpolymer marketed as T3000 by the company ZEON. CB stands for carbon black belonging to the class N6. The laminated clay used is a mineral filler produced and marketed by BASF as ASP NC X-1. MBTS stands for mercaptobenzothiazole-disulfide. TBBS is the acronym for N-tert-butyl-2-benzothiazole sulfenamide used as a vulcanization accelerator.

(15) Laboratory Test Results

(16) The compounds described above were subjected to tests in order to evaluate the properties thereof, both in terms of adhesion towards the reinforcing plies and in terms of oxygen impermeability.

(17) The oxygen impermeability test was performed on materials with a thickness of 0.7 mm and using a conventional apparatus as MOCON OX-TRA (model 2/61). The measurements were performed at a temperature of 25 C.

(18) For easier interpretation of the results obtained, in Table II, the oxygen impermeability values are given in a form that is indexed with reference to the results of the comparison compound generally used for the implementation of an innerliner layer (Comp.1). The lower the indexed value, the greater the oxygen impermeability.

(19) The adhesion of the compounds to the reinforced ply was estimated as a percentage of the ply that was still covered with rubber following the separation of the two parts of the ply-rubber compound by application of a load. The ply used in the text is made of PET.

(20) For easier interpretation of the results obtained, in Table II, the adhesion values are given in indexed form with reference to the results of the compound that is the object of the invention, (Compound B). The greater the indexed value, the greater the measured adhesion.

(21) The ply-rubber adhesion value for the comparison compound Comp.1 is not reported, insofar as the samerelating to an innerliner layer and not a body ply skim layerdoes not possess this characteristic.

(22) TABLE-US-00002 TABLE II Comp.1 Comp.2 Comp.3 Comp.4 A B Ply-rubber adhesion 55 55 85 100 100 Oxygen impermeability 100 720 340 212 130 108

(23) As can be seen from the data reported in Table II, the compounds that are the object of the present invention have oxygen impermeability values that are comparable to those of an innerliner compound (Comp.1) while, at the same time, they have adhesion values (covering) that are by far greater than those of a compound (Comp.2) commonly used in the preparation of a body ply skim portion.

(24) In other words, the compounds of the present invention have the great advantage of being able to implement body ply skim portions that not only have oxygen impermeability comparable to that of an innerliner, but that unexpectedly also have high adhesion to the reinforcing plies.

(25) This will make it possible to greatly reduce the thickness of the innerliner, nevertheless guaranteeing the necessary oxygen impermeability for said oxygen not to spread within the other parts of the tyre, thereby causing the known degradation phenomenon thereto.

(26) The values of Table II relating to the comparison compounds Comp.3 and Comp.4 show that the presence of epoxidized natural rubber only or the combination of epoxidized rubber and of polyepihalohydrin rubber only are not able to ensure the benefits of the compounds of the invention.

(27) Finally, a further advantage of the invention is the fact that the polyepihalohydrin rubber can be produced from renewable sources. In fact, processes have recently been implemented that can produce epichlorohydrin from vegetable origin glycerol. In this way, therefore, it will be possible to implement body ply skim portions with a significantly lower environmental impact than those of the known art.