METHOD FOR REPAIRING SELF-SEALING TIRES

Abstract

This invention discloses a technique for replenishing the level of sealant in self-sealing tires at the time that a puncture in the tire is being repaired or when the tire is being recapped. This technique provides the tire with its original level of self-sealing capabilities and will enhance the possibility of the tire remaining in service until it can be conveniently repaired. This method involves (1) injecting a liquid sealant formulation into the sealant layer of a self-sealing tire through at least one puncture hole therein, and (2) sealing the hole or holes in the supporting carcass and the innerliner of the tire. The sealant utilized is typically liquid polyisobutylene having a weight average molecular weight of 25,000 to 200,000. The sealant formulation used can optionally also contain a colorant or a pigment.

Claims

1. A method for replenishing sealant that has escaped from a self-sealing pneumatic tire through one or more holes, wherein said self-sealing pneumatic tire is comprised of a generally toroidal-shaped supporting carcass with an outer circumferential tread, two spaced beads, at least one ply extending from bead to bead, sidewalls extending radially from and connecting said tread to said beads, a sealant layer which is disposed inwardly from the supporting carcass, and an innerliner which is disposed inwardly from the sealant layer, and wherein said circumferential tread is adapted to be ground-contacting, said method comprising (1) injecting a liquid sealant formulation into the sealant layer of the tire through at least one of the holes, and (2) repairing the hole or holes in the supporting carcass and the innerliner of the tire.

2. The method as specified in claim 1 wherein the liquid sealant formulation is polyisobutylene, and wherein the polyisobutylene has a weight average molecular weight which is within the range of 25,000 to 200,000.

3. The method as specified in claim 2 wherein the polyisobutylene has a weight average molecular weight which is within the range of 40,000 to 130,000.

4. The method as specified in claim 2 wherein the polyisobutylene has a weight average molecular weight which is within the range of 50,000 to 110,000.

5. The method as specified in claim 2 wherein the liquid sealant composition is further comprised of a pigment selected from the group consisting of red pigments, orange pigments, yellow pigments, green pigments, and blue pigments or a colorant selected from the group consisting of red colorants, orange colorants, yellow colorants, green colorants, and blue colorants.

6. The method as specified in claim 2 wherein said sealant composition is void of carbon black.

7. The method as specified in claim 2 wherein said sealant composition is void of oils.

8. The method as specified in claim 2 wherein said sealant composition is void of polyethylene glycol.

9. The method as specified in claim 2 wherein said sealant composition is void of polydiene rubbers.

10. The method as specified in claim 2 wherein said sealant composition is void of natural rubber, synthetic polyisoprene rubber, emulsion styrene-butadiene rubber, solution styrene-butadiene rubber, isoprene-butadiene rubber, styrene-isoprene-butadiene rubber, styrene/butadiene diblock polymers, styrene/butadiene/styrene triblock polymers, neoprene, nitrile rubber, ethylene-propylene rubbers, and ethylene-propylene-diene monomer rubbers.

11. A sealant composition which is particularly useful for repairing self-sealing tires, said sealant composition consisting essentially of a liquid polyisobutylene having a weight average molecular weight which is within the range of 25,000 to 200,000 and a colorant or a pigment.

12. The sealant composition as specified in claim 11 wherein the polyisobutylene has a weight average molecular weight which is within the range of 30,000 to 160,000.

13. The sealant composition as specified in claim 11 wherein the polyisobutylene has a weight average molecular weight which is within the range of 40,000 to 130,000.

14. The sealant composition as specified in claim 11 wherein the polyisobutylene has a weight average molecular weight which is within the range of 50,000 to 110,000.

15. The sealant composition as specified in 11 wherein the pigment or colorant is selected from the group consisting of Pigment Yellow 1 (CAS No. 2512-29-0), Pigment Yellow 110 (CAS No. 5590-18-1), Pigment Yellow 12 (CAS No. 15541-56-7), Pigment Yellow 126 (CAS No. 90268-23-8), Pigment Yellow 127 (CAS No. 68610-86-6), Pigment Yellow 13 (CAS No. 5102-83-0), Pigment Yellow 138 (CAS No. 30125-47-4), Pigment Yellow 14 (CAS No. 5468-75-7), Pigment Yellow 150 (CAS No. 68511-62-6), Pigment Yellow 151 (CAS No. 31837-42-0), Pigment Yellow 154 (CAS No. 68134-22-5), Pigment Yellow 168 (CAS No. 71832-85-4), Pigment Yellow 17 (CAS No. 4531-49-1), Pigment Yellow 174 (CAS No. 78952-72-4), Pigment Yellow 180 (CAS No. 77804-81-0), Pigment Yellow 183 (CAS No. 65212-77-3), Pigment Yellow 191 (CAS No. 129423-54-7), Pigment Yellow 3 (CAS No. 6486-23-3), Pigment Yellow 34 (CAS No. 1344-37-2), Pigment Yellow 42 (CAS No. 51274-00-1), Pigment Yellow 65 (CAS No. 6528-34-3), Pigment Yellow 74 (CAS No. 6358-31-2), Pigment Yellow 75 (CAS No. 52320-66-8), Pigment Yellow 81 (CAS No. 22094-93-5), Pigment Yellow 83 (CAS No. 5567-15-7), C.I. Pigment Yellow 42 (iron oxide), C.I. Pigment Yellow 34 (lead chromates), C.I. Pigment Yellow 184 (bismuth vanadates), C.I. Pigment Yellow 53 (nickel antimony), C.I. Pigment Orange 20 (cadmium sulfide), C.I. Pigment Red 101 (iron oxide), C.I. Pigment Red 104, C.I. Pigment Red 29 (ultramarine pigment), C.I. Pigment Blue 29 (ultramarine pigment), C.I. Pigment Blue 28, C.I. Pigment Blue 36, C.I. Pigment Violet 15 (ultramarine pigment), C.I. Pigment Violet 16 (manganese violet), Pigment Green 17 (chrome oxide green), C.I. Pigment Green 19 (cobalt-based mixed metal oxides), C.I. Pigment Green 26 (cobalt-based mixed metal oxides), and C.I. Pigment Green 50 (cobalt-based mixed metal oxides).

16. The sealant composition as specified in claim 11 wherein the pigment or colorant is an inorganic pigment selected from the group consisting of Ultramarine blue, Persian blue, Cobalt blue (CAS No. 1345-16-0), Curlean blue, Egyptian blue, Han blue (BaCuSi.sub.4O.sub.10), Azurite blue (Cu.sub.3(CO.sub.3).sub.2(OH).sub.2, Prussian blue (CAS No. 14038-43-8), YInMn blue (Oregon blue), Realgar red (α-As.sub.4S.sub.4), cadmium red (Cd.sub.2SSe), Cerium sulfide red, Venetian red (Fe.sub.2O.sub.3), Red Ochre (anhydrous Fe.sub.2O.sub.3), Burnt sienna red, Red lead (Pb.sub.3O.sub.4), Vermilian red, Cinnabar red, Ultramarine violet, Han purple (BaCuSi.sub.2O.sub.6), Cobalt violet (CO.sub.3(PO.sub.4).sub.2), Manganese violet (NH.sub.4MnP.sub.2O.sub.7), Purple of Cassius, Primrose yellow (BiVO.sub.4), Cadmium yellow (CdS), Chrome yellow (PbCrO.sub.4), Aureolin yellow (K.sub.3Co(NO.sub.2).sub.6), Yellow Ochre (Fe.sub.2O.sub.3.H.sub.2O), Naples yellow, Titanium yellow (NiO.Sb.sub.2O.sub.3.20TiO.sub.2), Zinc yellow (.sub.ZnCrO4), and Chrome orange (PbCrO.sub.4.PbO).

17. A method for replenishing sealant that has escaped from a self-sealing pneumatic tire through one or more holes, wherein said self-sealing pneumatic tire is comprised of a generally toroidal-shaped supporting carcass with an outer circumferential tread, two spaced beads, at least one ply extending from bead to bead, sidewalls extending radially from and connecting said tread to said beads, a sealant layer which is disposed inwardly from the supporting carcass, and an innerliner which is disposed inwardly from the sealant layer, and wherein said circumferential tread is adapted to be ground-contacting, said method comprising (1) making a slit in the innerliner of the tire, (2) injecting a solid sealant composition into the slit to replenish the level of sealant in the tire, wherein the sealant composition is comprised of a butyl rubber and/or polyisobutylene and a peroxide, (3) sealing the slit and any the hole or holes in the supporting carcass of the tire, (4) subjecting the tire to a cure cycle.

18. The method of claim 17 wherein the cure cycle is used to cure a replacement tread onto the tire during recapping of the tire.

19. The method of claim 18 wherein the sealant composition is further comprised of a filler, a processing oil, and polyethylene glycol.

20. The method of claim 18 wherein the sealant composition is further comprised of a colorant or pigment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention is further illustrated by the accompanying drawings. These drawings represent two preferred embodiments of the present invention.

[0028] FIG. 1 is a cross-sectional view of a tire of this invention wherein the sealant layer is sandwiched between the innerliner and carcass of the tire.

[0029] FIG. 2 is a cross-sectional view of a pneumatic rubber tire of this invention wherein the self-sealant layer of the tire is located between two layers of innerliner in the tire.

DETAILED DESCRIPTION OF THE INVENTION

[0030] Sealant which is lost from conventional self-sealing tires which are manufactured utilizing conventional tire building techniques can be replenished utilizing the technique of this invention. The replacement sealant will be injected into the sealant layer of the tire in an amount which is sufficient to replace the quantity of sealant lost. This is typically a level which will expand the sealant layer to its original size. For instance, the replacement sealant is normally injected in a quantity which will restore the sealant layer of the tire to its original thickness. Generally, the thickness of the sealant layer will range from about 0.2 mm to about 8.5 mm. It is generally preferred for the sealant layer to have a thickness of 3 mm to 6 mm and is typically most preferred for the sealant layer to have a thickness which is within the range of 4 mm to 5 mm. In passenger tires it is normally most preferred for the sealant layer to have a thickness of about 4.5 mm.

[0031] The sealant layer will normally extend from one shoulder of the tire to the other, in other words, it should cover the crown area of the tire. In most cases the sealant layer is situated in the tire between the supporting carcass and the innerliner of the tire as is illustrated in FIG. 1. The innerliner is an air barrier layer that serves to keep air or another gas, such as nitrogen, which is used to inflate the tire for escaping through the tire structure by diffusion. The innerliner is typically comprised of a halobutyl rubber or some other suitable material having a high degree of resistance to gas permeation. Another possibility is for the sealant layer to be situated in the tire between two layers of innerliner as is illustrated in FIG. 2. In other words, it is sandwiched between two or more layers of innerliner or between one or more innerliner layers and the tire carcass.

[0032] The self-sealing tire 2 depicted in FIG. 1 has sidewalls 3, a supporting carcass 4, inextensible beads 5, an innerliner (air barrier layer) 6, a sealant layer 7, and an outer circumferential tread (tread portion) 8. The individual sidewalls 3 extend radially inward from the axial outer edges of the tread portion 8 to join the respective inextensible beads 5. The supporting carcass 4 acts as a supporting structure for the tread portion 8 and sidewalls 3. The sealant layer 7 is disposed inwardly from said supporting carcass 4 and outwardly from said innerliner 6. The outer circumferential tread 8 is adapted to be ground contacting when the tire is in use. In this embodiment of the invention, the innerliner 6 is disposed inwardly from said supporting carcass 4.

[0033] In FIG. 2 a self-sealant pneumatic rubber tire 10 of another embodiment of this invention is depicted. This pneumatic tire of the tubeless type includes a tread portion 11, a crown area 12, sidewalls 13, a supporting carcass 14, inextensible beads 15, an innerliner 16, and sealant layer 17. In this embodiment of the present invention the sealant layer 17 is sandwiched between two layers of innerliner 16. This, sealant layer 17 is disposed inwardly from one layer of innerliner and outwardly from another layer of innerliner. Both layers of innerliner 16 and the sealant layer 17 are disposed inwardly from the supporting carcass 14.

[0034] In the practice of this invention the replacement sealant is injected into the depleted sealant layer of the tire. The replacement sealant is normally injected into the depleted sealant layer through a hole where the tire was previously punctured. This is normally done using a dull pointed injector. In cases where the tire was not punctured, but the level of sealant needs to be supplemented, such as in retreading operations, the replacement sealant can be injected into the sealant layer by piercing through the innerliner using an injection needle having a sharp point. In either case, after the replacement sealant has been injected any holes in through the innerliner and/or supporting carcass are repaired so as to plug the holes.

[0035] The replacement sealant employed in the practice of this invention is typically liquid polyisobutylene. The polyisobutylene typically has a weight average molecular weight which is within the range of 25,000 to 200,000. The polyisobutylene more typically has a weight average molecular weight which is within the range of 30,000 to 160,000, and preferably has a weight average molecular weight which is within the range of 40,000 to 130,000. The polyisobutylene more preferably has a weight average molecular weight which is within the range of 50,000 to 110,000. In many cases the polyisobutylene rubber will have a weight average molecular weight which is within the range of 50,000 to 75,000. The polyisobutylene can be used neat without any additional ingredients being included in the sealant formulation.

[0036] The replacement sealant can optionally also include a pigment or a colorant to make the point where a tire was punctured more visible. A wide variety of colors can be used for this purpose with light colors which stand out from the characteristic black color of tire treads being preferred. Titanium dioxide can be utilized to impart a brilliant white color, red iron pigment can be used to impart a brilliant red color, or pigment yellow 12 can be used to impart a brilliant yellow color. The pigment or colorant will typically be utilized in a quantity that will make punctures in the tire more readily apparent and will normally be used at a level which is within the range about 1 phr to about 5 phr, and will preferably be used at a level which is within the range of 2 phr to 4 phr.

[0037] Both organic and inorganic pigments can be utilized. In most cases the pigment or colorant will be of a white, red, orange, yellow, green, or blue color. Some representative examples of pigments that can be utilized include, but are not limited to, Pigment Yellow 1 (CAS No. 2512-29-0), Pigment Yellow 110 (CAS No. 5590-18-1), Pigment Yellow 12 (CAS No. 15541-56-7), Pigment Yellow 126 (CAS No. 90268-23-8), Pigment Yellow 127 (CAS No. 68610-86-6), Pigment Yellow 13 (CAS No. 5102-83-0), Pigment Yellow 138 (CAS No. 30125-47-4), Pigment Yellow 14 (CAS No. 5468-75-7), Pigment Yellow 150 (CAS No. 68511-62-6), Pigment Yellow 151 (CAS No. 31837-42-0), Pigment Yellow 154 (CAS No. 68134-22-5), Pigment Yellow 168 (CAS No. 71832-85-4), Pigment Yellow 17 (CAS No. 4531-49-1), Pigment Yellow 174 (CAS No. 78952-72-4), Pigment Yellow 180 (CAS No. 77804-81-0), Pigment Yellow 183 (CAS No. 65212-77-3), Pigment Yellow 191 (CAS No. 129423-54-7), Pigment Yellow 3 (CAS No. 6486-23-3), Pigment Yellow 34 (CAS No. 1344-37-2), Pigment Yellow 42 (CAS No. 51274-00-1), Pigment Yellow 65 (CAS No. 6528-34-3), Pigment Yellow 74 (CAS No. 6358-31-2), Pigment Yellow 75 (CAS No. 52320-66-8), Pigment Yellow 81 (CAS No. 22094-93-5), Pigment Yellow 83 (CAS No. 5567-15-7), C.I. Pigment Yellow 42 (iron oxide), C.I. Pigment Yellow 34 (lead chromates), C.I. Pigment Yellow 184 (bismuth vanadates), C.I. Pigment Yellow 53 (nickel antimony), C.I. Pigment Orange 20 (cadmium sulfide), C.I. Pigment Red 101 (iron oxide), C.I. Pigment Red 104, C.I. Pigment Red 29 (ultramarine pigment), C.I. Pigment Blue 29 (ultramarine pigment), C.I. Pigment Blue 28, C.I. Pigment Blue 36, C.I. Pigment Violet 15 (ultramarine pigment), C.I. Pigment Violet 16 (manganese violet), Pigment Green 17 (chrome oxide green), C.I. Pigment Green 19 (cobalt-based mixed metal oxides), C.I. Pigment Green 26 (cobalt-based mixed metal oxides), and C.I. Pigment Green 50 (cobalt-based mixed metal oxides).

[0038] Some additional inorganic pigments that can be used include Ultramarine blue, Persian blue, Cobalt blue (CAS No. 1345-16-0), Curlean blue, Egyptian blue, Han blue (BaCuSi.sub.4O.sub.10), Azurite blue (Cu.sub.3(CO.sub.3).sub.2(OH).sub.2, Prussian blue (CAS No. 14038-43-8), YInMn blue (Oregon blue), Realgar red (α-As.sub.4S.sub.4), cadmium red (Cd.sub.2SSe), Cerium sulfide red, Venetian red (Fe.sub.2O.sub.3), Red Ochre (anhydrous Fe.sub.2O.sub.3), Burnt sienna red, Red lead (Pb.sub.3O.sub.4), Vermilian red, Cinnabar red, Ultramarine violet, Han purple (BaCuSi.sub.2O.sub.6), Cobalt violet (CO.sub.3(PO.sub.4).sub.2), Manganese violet (NH.sub.4MnP.sub.2O.sub.7), Purple of Cassius, Primrose yellow (BiVO.sub.4), Cadmium yellow (CdS), Chrome yellow (PbCrO.sub.4), Aureolin yellow (K.sub.3Co(NO.sub.2).sub.6), Yellow Ochre (Fe.sub.2O.sub.3.H.sub.2O), Naples yellow, Titanium yellow (NiO.Sb.sub.2O.sub.3.20TiO.sub.2), Zinc yellow (ZnCrO.sub.4), and Chrome orange (PbCrO.sub.4—PbO).

[0039] The replacement sealant will normally be void of fillers, such as carbon black, graphite, graphene, carbon nanotubes, wollastonite, silica, crystalline silica, clay, chemically modified clays, 2:1 layered silicate clays (montmorillonite, bentonite, hectorite, saponite, nontronite, beidellite, fluorohectorite, stevensite, volkonskoite, sauconite laponite, related analogs thereof and their physical blends), talc, diatomaceous earth, calcium carbonate (CaCO.sub.3), calcium silicate, starch, lignin, alumina, and polyolefins, such as polypropylene. The replacement sealant will also normally be void of polyethylene glycol and oils, such as aromatic oils, paraffinic oils, naphthenic oils, triglyceride oils, and low PCA oils, such as MES, TDAE, SRAE and heavy naphthenic oils.

[0040] The following examples are included to further illustrate the method of replenishing the level of sealant in self-sealing tires. These examples are intended to be representative of the present invention and are not to be regarded as limiting the scope of the invention or the manner in which it can be practiced. Unless specifically indicated otherwise, parts and percentages are given by weight.

Examples 1-5 and Comparative Example 6

[0041] In this series of experiments a number of compositions were evaluated for use in replenishing the level of sealant in self-sealing tires which are being repaired or recapped. The results of these evaluations are reported in Table 1. It should be noted that Comparative Example 6 was a control in which a commercial butyl rubber sealant was evaluated. The storage modulus (G′) values shown in Table 1 are reported in MPa.

TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 PIB PIB PIB PIB.sup.1 PIB.sup.2 BR M.sub.v 40,000 55,000  85,000  85,000  85,000 — M.sub.w 53,000 70,000 108,000 108,000 108,000 —  G′ @ 1% 0.021 0.050 0.098 0.084 0.011 0.106  G′ @ 3% 0.022 0.054 0.101 0.087 0.019 0.078  G′ @ 5% 0.022 0.054 0.099 0.087 0.019 0.066 tanδ @ 1%  1.218 0.738 0.461 0.512 1.049 0.795 tanδ @ 3%  1.475 0.849 0.526 0.585 0.89  0.991 tanδ @ 5%  1.427 0.875 0.535 0.602 0.957 1.084 .sup.1The polyisobutylene rubber evaluated in this example also include 1.5 phr of Di-Cup 40C dicumyl peroxide on precipitated calcium carbonate (40.5% active) from Arkema Inc. and was cured. .sup.2The polyisobutylene rubber evaluated in this example also include 3 phr of Di-Cup 40C dicumyl peroxide on precipitated calcium carbonate (40.5% active) from Arkema Inc. and was cured.

[0042] As can been seen from Table 1, the storage modulus values reported in Example 1 and Example 2 are less than 0.70 MPa and have characteristics that are useful for sealant compositions. In fact, these liquid polyisobutylene polymers have storage modulus values which are within an excellent range of 0.020 MPa to 0.055 MPa. As can be seen, the higher molecular weight polyisobutylene evaluated in Examples 3-5 could be reduced significantly by including a peroxide and subjecting it to a cure cycle. In any case, Table 1 shows that liquid polyisobutylene can be used to replenish the level of sealant in self-sealing tires.

[0043] In another embodiment of this invention, higher molecular weight semi-solid or even solid rubbers containing a peroxide can be used to replenish the level of sealant in self-sealing pneumatic tires. In other words, conventional sealant compositions as known in the art can be used in replenishing the level of sealant in self-sealing tires. In one scenario, a slit could be made in the innerliner of the tire with the semi-solid or solid sealant composition being inserted therein. Then, the slit in the innerliner is repaired and the tire is subjected to a cure cycle, such as curing the tread onto a tire in standard recapping techniques. Solid sealant compositions that can be employed in such procedures typically contain a butyl rubber and/or polyisobutylene, a peroxide, a filler, optionally, a processing oil, optionally, a colorant or pigment, and optionally polyethylene glycol. Such solid sealant compositions are described in greater detail in U.S. Patent Application Ser. No. 63/084,898; U.S. Pat. Nos. 4,895,610; and 4,228,839. The teachings of U.S. Patent Application Ser. No. 63/084,898, U.S. Pat. Nos. 4,895,610, and 4,228,839 are incorporated herein by reference for the purpose of describing such solid sealant compositions.

[0044] Variations in the present invention are possible in light of the description of it provided herein. The illustrations and corresponding descriptions are not intended to restrict or limit the scope of the appended claims in any way. While certain representative embodiments 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 subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.