Method for the treatment of a sealant layer of a tyre, sealant and tyre

Abstract

A method for reducing the stickiness on the surface exposed to the air of a sealant layer applied on an inner cavity of a tyre. The method establishes that the surface exposed to the air of the sealant layer is subject to a UV radiation.

Claims

1. A method for the application of a sealant layer in a tire comprising a deposition step, in which a vulcanized sealant layer having a stickiness is deposited on a free surface of an inner liner layer facing an inner cavity of the tire; and a step of reduction of the stickiness, in which a surface exposed to the air of said sealant layer deposited on said inner liner layer is subject to the direct action of a UV radiation.

2. A method according to claim 1, characterized in that said UV radiation has a wavelength range ranging from 200 to 400 nm.

3. A method according to claim 1, characterized in that said UV radiation has a radiant exitance ranging from 250 W/m.sup.2 to 1500 W/m.sup.2.

4. A method according to claim 3, characterized in that said UV radiation has a radiant exitance ranging from 500 W/m.sup.2 to 1000 W/m.sup.2.

5. A method according to claim 1, characterized in that said surface exposed to the air is subject to a UV radiation for an amount of time ranging from 5 min to 15 min.

Description

BEST MODE FOR CARRYING OUT THE INVENTION

(1) An embodiment example is given below purely by way of illustrative non-limiting example.

(2) A compound was prepared for the production of a sealant layer, the formulation of which is reported in phr in Table I.

(3) TABLE-US-00001 TABLE I Halobutyl rubber 100.0 Carbon black 40.0 Plasticizer 240.00 Sulphur 0.5 Stearic acid 1.5 Zinc oxide 1.0 Accelerant 4.0 The halobutyl rubber is a bromobutyl rubber. The carbon black used is identified by N550. The plasticizer used is naphthenic oil. The accelerant used is dibenzothiazyl disulphide (MBTS).

(4) The ingredients indicated in Table I were mixed together and kept under stirring at a temperature of 100 C. for 10 min.

(5) The compound thus prepared was vulcanized and applied on the surface of an inner liner layer. In particular, the sealant layer was heated and placed in an extruder from where it was extruded directly above the inner liner layer.

(6) The sealant layer is applied according to a known technique and therefore does not constitute an innovative aspect for the present invention.

(7) A surface exposed to the air of the sealant layer was irradiated with a UV lamp for 15 minutes. The lamp used emits in a radiant exitance range between 500 W/m.sup.2 and 1000 W/m.sup.2 and in a wavelength range between 200 and 400 nm.

(8) During treatment with the UV radiation, the stickiness of the surface subject to the treatment was periodically measured, identifying a progressive reduction in the stickiness. It was found that after the 15 minutes of irradiation, the stickiness on the irradiated surface had decreased by approximately 80% compared to the initial stickiness.

(9) To verify whether the treatment subject of the present invention could compromise the effectiveness of the sealant layer overall, the viscosity and stickiness values of the surface exposed to the radiation were measured and also the pressure retention following puncturing of the tyre on which said treatment was applied.

(10) For a significant evaluation of the effects of the treatment subject of the present invention, the above parameters were measured both on the layer that underwent the UV radiations and on a sealing layer that was identical but did not undergo UV radiations. A comparison between the values recorded on the two sealant layers can reveal whether application of the treatment subject of the present invention has effects or not, not only on the surface stickiness, but also on the characteristics important for effectiveness of the sealant layer.

(11) The viscosity measurement was obtained according to the ISO13145 standard procedure while the stickiness measurement was obtained according to the D1876 standard procedure.

(12) The pressure retention test was performed on tyres on which the sealant layer not subject to the UV radiation treatment and the sealant layer subject to 15 minutes of UV radiation were applied, in the same conditions. After inflating the tyres to the same internal pressure, they were subjected to the same puncturing conditions with subsequent removal of the object used for the puncturing. For each of the tyres that underwent the test, retention of the pressure 24 h after puncturing (and subsequent removal of the object) was evaluated.

(13) Table II shows the values of the above tests, in indexed form with respect to the sealant layer not subjected to the UV radiation treatment.

(14) TABLE-US-00002 TABLE II Before treatment After treatment Viscosity 100 100 Pressure retention 100 100 Stickiness 100 20

(15) From the values of Table II it can be seen that, while the treatment subject of the present invention causes a drastic reduction in surface stickiness, the viscosity and pressure retention characteristics are not modified by the irradiation with the UV radiations.

(16) In other words, the treatment of the present invention solves the problems of the known art, drastically reducing the stickiness of the surface exposed to the air of the sealant layer applied on the inner cavity of a tyre, without compromising in any way the sealing properties thereof.