NO760833L - - Google Patents

Description

The present invention relates to a puncture sealing compound intended for tubeless vehicle tyres, and a method for sealing puncture holes in tubeless tires on the basis of a mixture containing over 50% low molecular liquid rubber, a high molecular elastomer, and an amount of cross-linking agent for the mixture which is sufficient to give partial cross-linking.

Preferably, the mixture contains a tackifying or plasticizing compound, which enables the amount of low molecular weight elastomer to be reduced, but the total amount of tackifying or plasticizing compound plus low molecular weight elastomer constitutes over 50% of the mixture.

Puncture-sealing tubeless tires are previously known and these contain in the area of the tire that is most exposed to punctures (i.e. the tread or the area from one shoulder of the tire to the other above the tire crown), a layer of a sealant that has plastic and adhesive properties adapted so that the mixture adheres to the puncture object and when the object is pulled out will flow into the opening or puncture and form a plug that seals the opening against air loss. Unfortunately, it has proved difficult to provide a mass which will flow into the puncture hole and still have sufficient viscosity to prevent flow at elevated temperatures of up to 120°C and higher which occur in the tires under operating conditions. The problem is complicated by the very high centrifugal force to which the mixture is exposed when the tire rotates at high speed, since such centrifugal force will force the mixture to flow towards the central crown area of the tire and leave the areas near the shoulder sections unprotected. Furthermore, it has proven difficult to provide a sealing compound which will maintain the desired balance between viscosity, plasticity, adhesion and formability over a longer period of operation.

There are a number of patents that use non-vulcanized, partially vulcanized or fully vulcanized elastomer layers as puncture compounds in pneumatic tires. Among these are the U.S. patents Nos. 2,782,829 (1957), 2,802,505 (1957), and 2,811,190

(1957). Some of these masses include smaller amounts of plasticizers or plasticizers such as mineral oil, natural resin oils, coumarone-indene resins or liquid polybutene. Such substances, however, remain in a completely uncured state and do not act as actual components in the sealant. An embodiment of the present invention uses a larger amount, at least 50%, of liquid elastomer which is a significant part of the sealing mixture and is partially covulcanized with a high molecular weight solid elastomer. The resulting composition is unique in that the high molecular weight partially vulcanized portion of the mixture serves as a stiffened or gelled network that prevents the low molecular weight portion from flowing at elevated temperature and high centrifugal force and still allows sufficient malleability in the mass to act effectively as a puncture sealant. .

However, a preferred embodiment of the invention includes the use of a tackifier and/or piastizer as an additive, in which case the amount of liquid rubber mass can be below 50% as long as the total amount of tackifier plus liquid rubber is over 50%.

U.S. patent no. 2,657,729 (1953) describes a sealant based on depolymerized rubber and gelling agent.

Unlike the present sealant, this composition does not contain partially covulcanized high molecular weight elastomer.

Japanese Patent No. 82796/72 (1974) describes the use of mixtures of high molecular weight and low molecular weight elastomers, such as EPDM and polybutene, whose non-flowing property is achieved by adding short nylon fibers. In an example describing the use of a bag containing the puncture sealant in a small amount, 0.5 phr of sulfur is added to the mixture. This amount of sulfur is insufficient to work according to the present invention. • The present sealant contains against a sufficient amount of curing agent to form resistance to flow, fiber-based flow barrier is neither necessary nor desirable according to the present invention, which preferably

vis is without fibrous filler.

Thus, according to the prior art, various elastomers, both cured and uncured, have been proposed as puncture sealants. In the uncured state, the individual times, even though they may act as sealants, will be exposed to "cold flow" or flow at elevated temperatures which is encountered in tires during use. Such flow is undesirable. When the compounds are cross-linked (cured) to prevent flow, these compounds sometimes tend to lose adhesion and formability from the uncured state and no longer act as sealants.

The methods that have been used to date for sealing punctures in tubeless tires have not been completely satisfactory for a number of reasons. Particular difficulties have been in achieving satisfactory results when sealing tires of the radial type.

According to the invention, it has now been found that punctures in tubeless tires and including radial tires can be sealed in an appropriate and reliable manner by applying to the puncture hole a composition which is based on a mixture of a low-molecular liquid elastomer and a high-molecular solid elastomer containing a cross-linking agent in sufficient quantity to provide sufficient curing, so as to prevent the mixture from flowing at elevated temperature and high centrifugal force occurring under operating conditions. The compound is applied to the puncture hole and then cured in situ in the hole.

Applicants have found that a mixture of high and low molecular weight elastomers, where the latter is present in an amount in excess of 50% by weight, and is hardened to a limited degree sufficient to prevent flow under service conditions, offers new and unique advantages. The high-molecular elastomer provides rigidity and strength. The low molecular weight elastomer provides the adhesion and malleability necessary for a puncture sealant. Preferably, adhesion ability and

malleability increased by the addition of a tackifying agent and/

or piastising agent. The migration tendency is naturally greatest with the low-molecular component. By increasing the relative amount of the high molecular component, the tendency can be reduced but not completely removed. When the mass is partially cured, the cross-links will be more effective in the high-molecular elastomer and make it act as a supporting skeleton or latticework that prevents

re flow without cross-linking of the low molecular weight elastomer to the point where its function as a sealant would be significantly impaired.

Use of the present composition as a puncture-sealing material is notable in that the high molecular weight delyulcanized portion serves as a stiffened latticework that retains or prevents the low molecular weight portion from flowing at elevated temperature and high centrifugal force.

The invention shall be described in connection with the attached drawings, where: Fig. 1 schematically shows a cross-section through an air tire that uses a puncture-sealing layer according to the invention,

fig. 2 and 3 are enlarged sections from fig. 1 and illustrates the sealing effect of the sealant, and

fig. 4 shows in a similar way as .fig. 1 a modification of the invention,

fig. 5 schematically shows a cross section of a hose

loose tire punctured with a nail,

fig. 6 shows a section on a larger scale, and illustrates how the puncture hole is sealed by introducing the sealing material using a syringe or needle, and

fig. 7 shows in a similar manner as fig. 5, a tire

which is repaired while sitting on a coward.

As indicated, one side of the invention consists of a sealant which is a mixture of a low molecular weight elastomer with a high molecular weight elastomer, the former being present in an amount greater than 50%, based on the weight of the two polymers, and is cross-linked as measured by gel- and Mooney viscosity1, to a degree that will prevent the mass from flowing at an elevated temperature,'

shares have sufficient adhesion and malleability to act as

sealant and repair compound. Preferably, a tackifier may be used in place of a portion of the low molecular weight rubber to increase adhesion and formability.

Furthermore, the invention includes a method for repairing a puncture hole by applying the present repair material followed by partial curing or cross-linking.

Any high-molecular solid elastomer which can be cross-linked can be used as the aforementioned high-molecular elastomeric component in the sealing compound according to the invention. Examples are. highly unsaturated rubbers based on conjugated diolefins, either homopolymers as in polyisoprene (especially cis-polyisoprene, natural or synthetic), polybutadiene (including polybutadiene with a high cis content), polychloroprene (neoprene), or copoly-

more like e.g. have a greater proportion of conjugated dienes such as butadiene with a smaller relative amount of monoethylenically unsaturated copolymerizable monomers such as styrene or acrylonitrile. Alternatively, elastomers with low unsaturation can be used, particularly butyl rubbers (copolymers of such isoolefins as isobutylene with smaller amounts of conjugated dienes such as isoprene), or EPDM types (copolymers of at least two different monoolefins such as ethylene and propylene with a smaller amount of non- conjugated diene such as dicyclopentadiene, 1,4-hexadiene, 5-ethylidene-2-nor-bornene etc.) Even saturated elastomers such as EPM or ethylene vinyl acetate can be used, by using a suitable curing system. The elastomer can be prepared by emulsion or in solution, by stereospecific preparation or by other means. The solid elastomer's molecular

weight is usually over 50,000, and most often between 60,000 and 2 or 3 million or more. Typically, the solid elastomeric component has a Mooney viscosity in the range of 20 to 160 ML-4 at 100°C.

The low molecular weight elastomer used has a molecular weight of less than 50,000, usually in the range of 1,000 to 10,000 and is preferably of the "liquid" rubber type' with a maximum Brookfield viscosity at 66°C of 200,000 eps., usually in the range of 20,000 to 200,000 eps. Examples are: liquid cis-polyisoprene (eg heat depolymerized natural rubber, or cis-polyisoprene polymerized to low molecular weight), liquid polybutadiene, liquid polybutene, liquid EPDM, and liquid butyl rubber. The high molecular weight, elongation and film strength of cis-polyisoprene (both natural and synthetic) and high stickiness of depolymerized cis-polyisoprene provide a combination of these two elastomers, which after partial curing according to the present invention have a high flow resistance in combination with effective sealing ability. Other elastomeric combinations according to the invention, particularly saturated rubbers, provide resistance to oxidation during operation which also makes the mixtures very suitable.

Said tackifying or plasticizing compounds which are preferably added to the mass are low molecular weight substances such as e.g. natural resin esters ("Staybelite, ester 10), aliphatic petroleum resins (eg. "Piccopale.A-70), polyterpene resins.derived from alpha-pinene (eg.. "Piccolyte" A-10), beta-pinene (f .eg "Piccolyte" S-25), resins derived from styrene and related monomers (eg "Plccolastic" A-5), resins of dicyclopentadiene (eg "Piccodiene" 2215), and resins produced by reaction between a mineral oil cleaning residue with formaldehyde and with nitric acid catalyst according to West German patent no. 1.29 2.39 6, under the trademark "Struktol".

The new composition according to the invention contains a larger part, i.e. between 50 and 90% by weight of the total weight, low molecular material (i.e. low molecular elastomer plus low molecular tackifying agent). The weight ratio between high-molecular and low-molecular components depends mainly on the molecular weight of the high-molecular elastomer and other variables, such as the particular elastomer used, the amount and type of cross-linking agent and the nature of the cross-linking. Typically, the ratio of the two elastomeric components is chosen to give an initial Mooney viscosity at room temperature (the first peak reading, which is usually taken within the first few seconds) of between 30 and 70 (large rotor, ML) in the finished cross-linking compound, a preferred range is 40 to 60. Below said starting Mooney viscosity equal to 30, the compound will tend to flow down from the shoulder area and sidewalls of the tire when this is driven at high speeds, as well as out of the hole when the tire is punctured. Above said initial Mooney viscosity equal to 70,. will be the covering ability or sealing ability of the composition. degraded so that it becomes unusable for practical purposes. However, this upper limit does not apply when the mixture is used as a repair material.

Although there is no critical upper limit for the degree of hardening of the repair material, and the hardening can be carried out if desired

far that it would be considered substantially full curing in normal rubber processing practice, it is usually not necessary or desirable to use more curing agent than to obtain an initial Mooney viscosity of approx. 70-100 (ML at room temperature) when cross-linking is complete. The Mooney viscosity of the mixture can also be regulated for a given elastomeric mixture according to the invention by the amount of mechanical shear force used to mix the components. The net effect here is of course to break down (ie lower) the molecular weight of the high molecular weight component, thereby lowering the Mooney viscosity before curing.

According to the invention, the mixture further comprises a cross-linking agent. The crosslinking agent can be any compound or compound mixture that will harden or gel the mixture to the desired degree. Examples are: 1) Sulphur-curing systems based on sulfur or sulfur-releasing substances (e.g. tetramethyl thiuram disulfide) and common accelerators of sulfur vulcanization. 2) Quinone systems such as para-quinone-dioxime ("GMF, trademark Uniroyal Chemical) with or without additional oxidizing agent. 3) Organic peroxides (or hydroperoxides) such as dicumyl peroxide, cumene hydroperoxide, methyl ethyl ketone hydroperoxide or other radical releasing catalysts such as azobis-isobutyronitrile 4) Polyisocyanates such as MDI (4,4'-methylene-bis-phenylene-isocyanate), TDI (tolylene diisocyanate), and PAPI (polymethylene polyphenylisocyanate) as well as other dimers and trimers of MDI and TDI. 5) Tetrahydrocarbyl titanium esters as described in

parallel application.

The amount of cross-linking agent used will depend on the selected elastomers and their ratio, as well as the selected cross-linking agent and the cross-linking conditions. Usually, an amount is used that is sufficient to prevent the mixture from flowing in the tire at temperatures up to 95°C and speeds up to 80 kn/hour, while still having sufficient adhesion and forming ability to fulfill the desired sealing function. The quantities used will depend on the quantity ratio between high molecular weight and low molecular weight mixture. Higher relative amounts of high molecular weight elastomer require less crosslinking agent and vice versa to provide the desired combination of flow resistance and sealing ability. The amount of cross-linking agent will naturally vary with the nature of the elastomers.

For a mixture of depolymerized natural rubber (DPR) and natural rubber (NR) as the puncture sealing composition, the amount of sulfurous or quinoid curing agent will be in the range of 0.5 to 2.0 dph (parts by weight per 100 parts by weight of total elastomers), usually from 0 .7 to 1.5 dph. For this same mixture, when polyisocyanate or hydrocarbyl titanate ester curing agents are used, amounts from 2 to 10 dph, and usually 3 to 8 dph, will be required. For peroxide or hydroperoxide curing agents (radical releasing catalyst) the range will usually be 0.1 to 1.0 dph, preferably 0.2 to 0.7 dph.

For a mixture of depolymerized natural rubber (DPR)

and natural rubber (NR) used as repair compound, the amount of sulfur-containing or quinone-containing curing agent will be in the range from 0.5 to 4 dph, usually from 0.7 to 2 dph. For the same mixture with polyisocyanate or hydrocarbyl titanate ester hardeners, the required amounts will be in the range of 4 to 25 dph, preferably 5 to 15 dph. The application range for peroxide or hydroperoxide hardeners (radical releasing catalyst) will be 0.1 to 1.5 dph, preferably 0.2 to 1 dph.

The cross-linking of the sealing compound leads to increased viscosity and gel content (content of insoluble matter). It has been found that for a mixture of natural rubber and depolymerised natural rubber, a gel content measured in toluene at room temperature of between 15 and 60%, preferably 20 to 50% by weight in the crosslinked mixture will give the desired combination of sealing ability and flow resistance. For use as a repair material, the gel content should be between 20 and 80% or higher (eg 95%), preferably 20 to 60%. For other elastomeric compositions, the range for optimal gel content will vary depending on the molar weight and quantity ratio of the elastomeric components. As mentioned, it has been shown that an initial Mooney viscosity (ML at room temperature) in the specified range for the pre-cured mixtures coincides with the said desired combination of properties.

The cross-linking can take place at normal temperature or elevated temperature depending on the temperature at which the cross-linking system is active in the selected elastomer composition.

The composition can also, if desired, contain various additives such as pigments of the soot black type, special organic fillers, thickeners, adhesives, stabilizers and antioxidants. It is not necessary or desirable to add fibrous filler to the existing masses.

When carrying out the invention for use of the pulp

as a puncture sealant, the components are mixed evenly and introduced into the tire in the form of a relatively thin sealing layer (e.g. 2-3 mm thick). With reference to the drawings and in particular to fig. 1, one can see a typical embodiment of the invention which comprises a tubeless tire 10 with a normal vulcanized rubber tread 11 and side parts 12, 13 which are applied to a vulcanized rubber carcass 14 reinforced with wire material that terminates in rim beads 15, 16 which are provided with normal tensile strength reinforcement. The entire inside of the carcass is coated with a conventional air-tight liner 17. A layer 18 of sealant according to the invention extends over the inner crown or top surface of the liner in the tire from one shoulder area to the other,

and at least partially down over each interior side wall.

The sealing effect of the layer 18 is shown in fig. 2 and 3, where fig. 2 shows a nail 19 which has punctured the tire through the web 11, the carcass 14, the liner 17 and the sealing layer 18. The sealing layer will adhere to the nail and prevent loss of air pressure while the nail is in the tyre. When the nail is pulled out, as shown in fig. 3, it will tend to pull a plug 20 of sealant up through the hole 21, which is thereby closed against air loss.

By a modification of the invention, as shown in

fig. 4, the puncture sealing agent 23 according to the invention is arranged between the inner surface of the carcass 24 and the liner 25. In such cases where the sealing layer is embedded in the tire, can

it is cross-linked before or after the introduction. In a similar way, the tire can be hardened before or after introducing the sealing layer.

For applying a sealing layer inside a tire, the composition can be prepared as a solution in a solvent, such as e.g. n-hexane or other suitable volatile organic solvent. This glue can be applied (e.g. showered or brushed) to the desired area of the inner surface of the air sealing liner, using as many layers as necessary to build up the desired thickness. With the hydrocarbyl titanate curing system, the applied sealing layer will be sufficiently cross-linked to perform the sealing function within approx. five days at room temperature, although the curing time can be shortened if desired by storing in a warm place, e.g. at 50 to 100°C.

Another method is to extrude the heated sealant in the tire at an elevated temperature in the form of a layer or strip of the desired thickness. Advantageously, the composition can be extruded directly onto the liner surface from a suitable nozzle which enters the tire carcass, while it rotates. For extrusion at an elevated temperature, a curing system must be chosen which will not react too early at the extrusion temperature, but which will cure later at a somewhat higher temperature.

Tetrahydrocarbyl titanate ester curing of the sealing compound offers a particularly favorable solution in that with tetrahydrocarbyl titanate ester it is possible to extrude the sealing compound at an elevated temperature without prior curing and still the curing of the applied sealant can take place at a lower temperature (e.g. room temperature). The reason is that the titanate ester curing of the elastomeric compound will only take place if hydrocarbyl alcohol (obviously formed as a by-product of the curing reaction) can escape from the composition. If the mass is located in such a way that it cannot evaporate components (e.g. inside the extruder cylinder), curing will not take place, even at too high a temperature. However, after the mixture is applied to the tire, the hydrocarbyl alcohol. could evaporate freely from the layer and curing takes place, even without heating.

Alternatively, a pre-made strip (e.g. an extruded strip) of sealant of suitable width can

and thickness is applied in a suitable way to the inside of the tyre.

If desired, the puncture-sealing layer can cover the entire inner surface of the tire from one rim bead to the other,

in which case the liner can be omitted and the puncture-sealing layer serves as the liner.

In some cases, it may be advantageous to introduce the sealing strip into the tire unit during manufacture of the tire, e.g. by applying a strip of sealing compound to a tire building drum, and placing the liner and other carcass components. above this layer. The sealing layer can be prevented from adhering to the construction drum by first placing a layer of flexible material on the drum followed by the sealing layer and the rest of the tire components. Thus, the lining can first be placed on the construction drum, followed by the sealing layer and carcass layer, to build up a construction as shown in fig. 4.

The puncture-sealing effect and flow resistance of the composition of the invention can be tested in an inflated tyre. For this purpose, the sealant is placed in a tire that is driven at 110 - 140 km/h and sufficiently loaded to give an internal temperature of 120°C or higher. After driving at high speed, observe whether the sealant has flowed out of the tire shoulders and onto the crown area of the tire or whether it has formed a pond at the bottom of the tire after the tire has stopped. The ability to withstand flow at at least 80 km/h and internal air temperature of at least 95°C is an important criterion for judging the performance of the elastomer composition according to the invention. To assess the puncture sealing ability, the tire is punctured with nails of different sizes, which are then pulled out and the air pressure loss in the tire is measured. Another important advantage of the invention is the ability of the sealant to seal holes with a diameter of at least 3 mm.

When carrying out the invention as a repair compound

.the plastic repair compound is prepared by mixing the described components evenly and applying the compound to a tire to be repaired. Reference is made to the figure, and in particular fig. 5, where one sees a typical tire to be repaired and which consists of a tubeless tire 10. with radial layer and ordinary vulcanized rubber tread 11 and sidewalls 12, 13 over a vulcanized rubber carcass 14

reinforced with strings that end in rim beads 15,16 with

inserted tensile reinforcement. The entire inside side surface of the carcass is coated with a regular air-tight lining 17. The tire, as shown in the drawing, is punctured with a nail 19 which goes through the tread 11, the carcass 14 and the lining 17 and down into the inner cavity. For repairing the tire after it has been removed from the rim, the tire is pulled out of the puncture hole 22, as shown in fig. 6, and the repair compound 23 is introduced into the hole by means of a syringe 24 or the like. Amount introduced, repair material is usually from 50 to 200 g, and should be sufficient to completely fill the hole and form a

excess in the form of an enlarged patch part 25, which is shaped

by smearing or flattening the excess material against the liner surface in the interior of the tire around the puncture hole. The repair material is then cross-linked to make the repair permanent. In a preferred embodiment, the ratio between the surface of the patch part and the cross-sectional area of the hole should be approx. 100 to 400 to 1. To make the adhesion between the patch part and the inside of the tire as strong as possible, the contact area surrounding the hole should be cleaned by e.g. washing with aqueous soap solution, rubbing with solvent and/or brushing. For optimal adhesion between the patch part and the cleaned area, a thin layer of repair material is applied to the area from a solution in a suitable solvent. If the repair material requires heat for curing, the repair area can be heated by e.g. irradiation, hot air, placing in an oven or the like. If the repair material hardens without heating, this is probably unnecessary.

In the embodiment of the invention shown in fig. 7, the repair or sealing of the hole takes place while the tire is on the rim 26. As described above in connection with the repair of a flat tire, a quantity of sealant is injected, usually from approx. 50 to 100 g in the tire through a syringe 27 (fig. 3). The amount of repair material should be sufficient to completely fill the hole as a plug 29 and to form an excess that adheres to the plug on the inside of the tire as an enlarged head or lump 30. The head 30 whose cross-section is substantially larger than the cross-section of the hole area (due to of the elasticity of the repair compound which causes the compound to swell to a larger diameter as it flows out of the hole on the inside of the tire), acts as an anchor and holds the plug in the hole during use and prevents the plug from

blown out by the air pressure. The repair compound is cross-linked to make it permanent as before.

The following examples will illustrate the implementation of the invention in practice in more detail.

EXAMPLE. IN

480 g of natural rubber (Standard Malaya gum, Mooney viscosity 64 ML-4-100 o C, average weight-molar weight 4.7 x 10 6 ) was dissolved in 15 1 of n-hexane. To the solution was added 960 g of depolymerized natural rubber (DPR-400 "Hardman Company", viscosity 80,000 eps at 66°C), and the mixture was stirred until it was smooth. 100.8 g of tetra-n-butyl titanate was added and the adhesive was stirred

again. 24 g of "Antioxidamt 2246" (American Cyanamid), 2,2'-methylene-bis(4-methyl-6-tert-butylphenol) was added here.

The formed glue had a solids content of approx. 14%.

The adhesive was coated on the inside of the airtight liner

in a radial tire of the type HR 78-15 at a distance of 10 cm on

either side of the center line and up above the tire's inner sidewalls. The lining was first cleaned by washing with soap and water and dried. The glue was applied by painting in thin layers until you got it

a weight of 1200 g of solid material around the tire's entire circumference. The solvent was evaporated overnight at room temperature and curing was completed by allowing the tire to be stored at room temperature for 5 days. This process can be accelerated so that a similar hardening is obtained by heating the tire for 24 hours at 93°C. After curing, the gel content in the sealant was 35% measured in toluene at room temperature compared to approx. 5% before curing.

The modified tire was examined upon assembly

on a normal car rim, inflation to 2.0 kg/cm 2, and driving on a simulator roller of diameter. 28 cm for one hour at a speed of 80 kg/h to equalize the temperature of the tire. Eight nails with

4.7mm stud diameters were driven into each of the 6 grooves in the tire tread, distributed over the tire crown, one nail through each groove and two others between the lugs, so that the nail head does not

could be driven into the groove. The tire was driven for a further 20 h at 80 km/h, without adjusting the pressure.

No or little air loss from the tire was found. All the nails were taken out and a hole was found in the tire with approximately the same diameter as the nail stem. More importantly, it was observed that during the extraction and immediately after, only a slight pressure loss was obtained in the tire (less than 0.28 kg/cm 2 ) when all the holes were completely sealed with sealant. The tire was then driven a further 16,000 km (200 t at 80 km/h) and no further loss of pressure was found.

A similar tire containing no sealant lost pressure instantly in the above test, immediately after the studs were pulled out.

EXAMPLE' II

A tyre, where the sealant contained 60% DPR

400 and 40% natural rubber, was applied by extrusion at 120°C as a 2.5 mm thick layer on the inner lining of the tire and gave a similar result as when the sealant was applied from the solution. For extrusion, a mixture of 2.7 kg of DPR-400,

45 g "Antioxidant 2246" of 2.7 kg Hevea natural rubber latex

(67% solids) in cream form mixed in a dough mixer with a double S-blade at a container temperature equal to 132°C for 30 min. Vacuum was applied and mixing was continued for 30 min. after which the moisture content was below 0.2%. The mixture was cooled to approx. 77°C and 272 g of tetra-n-butyl titanate added. The mixer was closed tightly and mixing was continued for a further 30 min. The resulting mass was extruded at 120°C as a 2.5 mm thick layer on the tire inner liner. The starting Mooney viscosity at room temperature (large rotor, ML) for the fully cured sealant was 55.

EXAMPLE III

The mixture according to example II was used as a repair compound. The compound can be filled with a syringe, glue gun, grease gun or the like, for application to the repair site as described earlier. The mass can be heated to a higher temperature to facilitate application by increasing flow or plasticity, but this is not essential. The specified composition will not harden as long as the mixture is inside the sprayer or gun, because evaporation of hydrocarbyl alcohol, which is necessary for the hardening process to take place, cannot take place. However, when the repair compound is applied to the puncture area, alcohol can escape and curing takes place. Typical repairs with the specified composition are cross-linked to the desired extent within approx. five days at room temperature, or within a shorter time if the repair site is heated.

In an experiment, a tire of the type HR78-15 was punctured with a 7 cm nail in the center groove and the inside of the surface, which surrounded the hole was cleaned with n-hexane. With a grease gun filled with specified repair compound heated to 93°C, approx. 150 g of hot repair compound injected into the hole from the outside directly into the inside of the tyre. Excess repair compound was flattened into a patch as described earlier. The repaired tire was placed in a hot air oven and cured for 24 hours at 93°C, the patch and tire material then forming a continuous web. After cooling, the tire was fitted to a normal car rim and inflated to a pressure of 2.7 kg/cm 2. There was no air pressure loss over a period of two weeks. It is noted that this period of two weeks is not a necessary condition for carrying out the invention. The repair is permanent immediately after the minimum harden is reached. After the aforementioned two-week period, the inflation pressure was set to 2.0 kg/cm 2 and the tire was run on a roller with a diameter of 28 cm with a load of 450 kg at 80 km/h. There was no loss of pressure after 24 hours (1900 km), after which the drive ended.

EXAMPLE IV

A sealant containing equal parts natural rubber, DPR-400 and Struktol 30, as well as 8% tetraisopropyl titanate and 1% Antioxidant 2246 (both based on total rubber amount), was mixed according to the procedure in the second example above. The mass was extruded onto the liner in a tire as a 3 mm layer at 115°C, and cured for 7 days at 66°C. ML^ for the cured sealant at room temperature was 45 and the gel content equal to 33.1% measured in toluene at 50°C for 24 hours.

The tire was fitted with a rim and inflated. As a measure of the sealing effect, four 7 cm long nails were driven into the tire, one in the outer lug, one in the outer groove and two in inner positions. The tire was run on a cylinder at 80 km/h for periods of ] hour with; constant .speed increases of 8 km/1 until all the studs were ejected from the tire. All the holes, which in this experiment had the same diameter as the nail stems, were closed and the inflation pressure was not lost. A tire containing no sealant went flat within 1 minute after the first nail was ejected.

EXAMPLE V-

A sealant identical to the sealant from. example IV.. except that it contained 10% tetra-isopropyl titanate (based on total rubber weight) was extruded into each of four tires as a 3 mm strip and cured as above. The cured sealant had ML^ values at room temperature between 45 and 55 and gel content of 18 to 25%. The tires were put on a car, and a 2 1/2" nail driven in along the edge or in the center of the tread and the car driven for 100 miles in periods at the following speeds until the nails were thrown out.

For all the tires it was found that the studs were ejected and the hole closed with little or no loss of air pressure and the car could still drive. Uncoated tires during similar tests lost air pressure quickly and went flat within 1 minute

EXAMPLE VI

A sealant containing 50 parts natural rubber, 50 parts DPR-400 and 70 parts "Piccadiene 2215" (tackifying resin prepared from polymerized dicyclopentadiene, Hercules Inc.), plus 8% tetra-isopropyl titanate and 10% Antioxidant 2246 (based on total amount of rubber), was mixed as indicated in Example II. The mass was extruded at 120°C as a 3 mm thick strip in the tire and cured. The puncture sealing effect for this mass was measured. in the nail ejection test as in Example IV, and showed an average sealing effect of 75%. (3 out of 4 nail holes sealed).

EXAMPLE VII

A sealant containing 50 parts natural rubber and DPR-400, plus 50 parts "Piccopale 100" (a hydrocarbon polymer tackifying resin, Hercules, Inc.) 16% tetraisopropyl titanate and 10% "Antioxidant 224 6" (based on total rubber ) was mixed and extruded into a tire at 120°C as a 3 mm thick strip. The sealing effect in the nail ejection test from example IV was over 75%.

EXAMPLE VIII

A sealing compound of 50 parts natural rubber 50 parts: DPR-400 and 50 parts "Struktol 30" plus 10 parts by weight "Antioxidant 2.246" was extruded at 120°C as a flat strip

with thickness 6.3 mm and width 20 cm. It was irradiated with an electron beam at 1.4 million volts and a dose of 20 megarads. The irradiated sample showed a gel content of 29.6% and ML^start-Mooney viscosity) at room temperature equal to 43. The strip was laid on top of the air sealing layer of an uncured steel cord radial tire, which was cured in a conventional tire press. The tire showed 100% sealing effect in the nail ejection test from example IV.

EXAMPLE IX

A sealant containing 40 parts by weight of natural rubber, 30 parts by weight of DPR-400 and 30 parts by weight of "Struktol 30" as well as 4.2 parts by weight of tetra-isopropyl titanate and 0.7 parts by weight of "Antioxidant 2246" was mixed as indicated in Example II. Then the mass was extruded in a tire at 135°C as a 3 mm thick strip, cured and subjected to the nail ejection test of Example IV. Average sealing effect was 70%,

EXAMPLE X

Tc part butyl "LM .430" (Enjay liquid polyisobutylene, average viscosity-mol weight 32,000, about 4 mole percent unsaturation) and part "Royalene 505" (Uniroyal, Inc., ethylene-propylene-ethylidene norbornene terpolymer, 58/42 ethylene -propylene ratio, iodine number 20, ML-4=50 at 125°C) was dissolved in hexane to a concentration of approx. 10%. 8 dph (based on total rubber content) tetra-n-butyl titanate was added and the mixture coated on the inside of a tire in a width of 20 cm. A sufficient amount of solution was used to give a layer with a thickness of 3 mm after complete evaporation of the solvent. The sealant was allowed to cure by storage for at least 24 hours at room temperature after complete evaporation of the solvent. The tire was inflated on a rim and punctured in the track with;; four nails with a diameter of 3 mm. The tire was driven 1,600 km at 80 km/h on a cylinder and the nails were taken out.

There was no greater loss than 0.28 kg/cm 2 in air pressure and the holes were all sealed.

EXAMPLE XI

A sealant containing equal parts butyl LM 4 30 "Royalene 505" and "Piccolyte A100" (polyterpene resin derived from alpha-pinene, softening point 100°C), plus 6% tetra-n-butyl titanate (based on total rubber) was mixed out in hexane solution and coated on a deck to a strip 20 cm wide and 3 mm thick after evaporation. After curing at room temperature, the sealing effect of the coating was examined in the same way as in example X with 3 mm nails. Complete sealing was obtained after the nails were removed, with little or no loss of inflation pressure.

EXAMPLE XII

A sealant containing equal parts "Royalene 505", "Butyl LM 430" and "Piccodien 2215" plus 10% tetra-n-butyl titanate (based on total rubber mass) was dissolved in hexane and coated on a tire to a strip 20 cm wide and 3 mm thick after evaporation. After hardening at room temperature, the tire was examined to find the sealing effect as in example X. Two nails with a diameter of 3 mm were used and after driving for 1600 km they were removed, without loss of inflation pressure.

EXAMPLE XIII

A sealant containing equal parts "Royalene 525" (ethylene-propylene-ethylidene norbornene terpolymer, iodine number 20, ML-4=55 at 125°C), "Butyl LM 430" and "Struktol 30" plus 10% tetra-isopropyl- titanate (based on total rubber content) was dissolved in hexane and coated on a tire to a strip 20 cm wide and 3 mm thick after evaporation. The sealant was cured at room temperature, after which the tire was placed on a rim and inflated to 2.0 kg/cm 2. The tire was punctured with two 2.5" nails and driven at 80 km/h for 20 hours. The nails were then pulled out. , without loss of inflation pressure.

As described in more detail in the previously mentioned application .... which was filed at the same time, and to which reference is hereby made, the curing (the cross-linking or gelling to an insoluble state) of unsaturated elastomer with organic titanium ester takes place only when the mixture is exposed to free atmosphere and can is prevented by keeping the mixture in a closed system. The unsaturated elastomers that can be cured with titanium esters include cis-polyisoprene (natural or synthetic), polybutadiene, especially cis-polybutadiene, butadiene-styrene copolymer rubber, butadiene-acrylonitrile copolymer rubber, EPDM rubber (especially ethylene-.propylene-5-ethylidene-2- norbornene terpolymer rubber with an iodine number above 8), polychloroprene rubber, butyl rubber (isoprene-isobutylene copolymer), and mixtures of such elastomers. Organotitanate esters that are used as curing agents or cross-linking agents for gelling unsaturated elastomers are tetrahydrocarbyl titanates of the formula (RO)^Ti, where R denotes a hydrocarbyl group, such as e.g. an alkyl group, with 1 to 12 C atoms, preferably 3 to 8 C atoms, or an aryl group with 6 to 10 C atoms, for example cresyl. When preparing a hardenable mixture can

the mixture of the organo-titanate ester and the unsaturated elastomer takes place without evaporation in a closed•system such as e.g. a closed mixer of the S-blade stirrer type (eg Baker-Perkins) or Brabender mixers. Optionally, the organo-titanium ester can be mixed with the unsaturated elastomer in solution in an inert volatile organic solvent for the elastomer (e.g. n-hexane), preferably in the presence of a minor amount of volatile alcohol (e.g. ethyl alcohol) to suppress past gelling. The gelation takes place only after evaporation of the solvent and the alcohol. In most cases in practice, mixing occurs under conditions that suppress gelation (in a closed system with no possibility of evaporation, or in the presence of volatile alcohol) and then, after the mixture is formed into the desired shape (e.g., cast, extruded , coated etc), the mixture is allowed to set

by simply allowing evaporation to open atmosphere. Depending on the rubber types and the amount of extraneous hydroxyl compounds, such as e.g. antioxidants, (hydroxyl compounds are hardening-inhibiting components), the amount and type of titanium esters will determine the hardening speed and degree of hardening.

The required time and temperature for the titanate curing again depends on any hydroxy1 constituents that will counteract the curing and the type and content of titanium. Curing of the mixture takes place by evaporation of the alcohol, corresponding to the alkoxy part in the titanium ester. Thus, titanium esters of low boiling alcohols will harden faster than titanium esters of higher boiling alcohols, e.g. isopropyl titanate will act faster than butyl titanate, which in turn is faster than ethylhexyl titanate. Elevated temperature increases the curing rate regardless of the type and content of titanate, although solvent curing in the absence of added hydroxy1 inhibitors is rapid at room temperature. In general, from 1 to 10 days are required for curing at room temperature, depending on factors such as the type of rubber, the amount of hydroxy1 contamination, the surface/volume ratio (the larger the exposed surface, the faster the curing takes place), as well as the relative content and type of titanium esters. It is an essential feature of curing that the curable mixture can be processed at an elevated temperature (without the possibility of evaporation) without previous curing taking place, after which the curing can then take place at a lower temperature or room temperature (when evaporation is allowed).

As indicated, it has been found that the titanate curing reaction is followed by alcohol evolution, i.e. an alcohol ROH corresponding to the ester's organic group in the formula (RO)^Ti is released during curing. If the alcohol is prevented from evaporating, such as in a closed container, curing will not proceed. However, when the curable mass is placed in an open atmosphere, where evaporation can take place and the evolved alcohol ROH can escape, the curing will take place. Thin parts such as e.g. coatings deposited from a solution, calendered or extruded films and webs,

and similar thin parts (e.g. 5 mm or less), have a higher surface/volume ratio than thicker parts (such as most cast versions) and have a greater opportunity for evaporation of the released alcohol ROH. Therefore, such thin sections will harden faster

than thick.

As the titanate cure proceeds, the gel content of the rubber will increase (that is, the fraction insoluble in organic liquids which are usually solvents for uncured elastomer), indicating that cross-linking is taking place and alcohol evolution is taking place until a certain degree of gel formation is reached .

As indicated, hydroxyl-containing additives have an inhibiting or hindering effect on titanate curing. For example, it has been found that phenolic antioxidants will reduce the curing rate. When such antioxidants are removed, as much as possible, solutions of the rubber will tend to solidify more quickly when titanium esters are added. Normally, significant gelation will only take place slowly during evaporation

of solvent from the soln. Addition of small amounts of volatile alcohol to the gum solutions will prevent premature gelation. In this way, the curing rate can be regulated by the molar weight of the added alcohol. Low molecular weight alcohols such as ethyl alcohol have a weak or temporary inhibitory effect, while higher boiling alcohols such as dodecyl alcohol have a greater and more permanent inhibitory effect. After gelling, the solidified gum is insoluble in toluene or other organic solvents, but the addition of an acid such as acetic acid reverses the process and the gum becomes soluble again. Addition of carboxylic acids will also inhibit gel formation. It seems possible that the cross-linking is a consequence of titanium ester formation in the elastomer.

Preferred elastomers for use with the titanate curing agent are natural rubber, synthetic cis-polyisoprene elastomer, cis-polybutadiene elastomer, and ethylene-propylene-5-ethylidene-2-norbornene terpolymer with an iodine number of at least 12, in low molecular weight form (liquid form) or higher molecular form (solid form).

It will be understood that measurements of gel content and Mooney viscosity discussed here, in connection with fully cured sealant, are measured on a separate sample of sealant that has undergone curing conditions equivalent to the conditions to which the final curing agent is subjected, that is of course it is not practical to make these measurements on the real sealant that is in use in the tire itself.

In tires repaired by the present method, the puncture hole is completely filled with sealant which is sufficiently plastic and malleable in the uncured state to take the exact shape of the puncture hole and . fill all cavities without unwanted tensile stresses occurring. Such a repair will, after a certain minimum hardening in situ as described, tend to stay in place unlike various repairs made with a pre-formed plug or the like, which tend to work loose. Ordinary repair plugs are often cut through when they work against steel strands in belts used to build up radial tires (especially at the stretched ends of broken strands in the puncture area), while the existing repair compound resists this due to the nature of the material and method of application. Adhesion between the inner patch part of the repair compound and the inside of the tire is good, due to the way it is applied in the uncured state, followed by curing in situ on the inner tire surface. The liquid rubber component, which undergoes only limited vulcanization during the repair process, serves to maintain stickiness and adhesiveness, so that the mass is not worked loose.

Claims (31)

1.. Composition for sealing puncture holes in tubeless tyres, characterized by the wood mixture of at least 50 to 90% by weight low molecular weight liquid elastomer in the form of a liquid rubber with a Brookfield viscosity at 66°C, of 20,000 to 200,000 eps with correspondingly less than 50 to 10% by weight high molecular weight elastomer with a Mooney viscosity of 20 to 160 ML-4 at 100°C, as well as a cross-linking agent for the elastomers in an amount sufficient to partially cross-link the elastomers to such an extent that the mass, after cross-linking, has a gel content of 15 to 95% by weight of the mixture measured in toluene at room temperature and an initial Mooney viscosity of more than 30 ML at room temperature, which mixture in a partially cross-linked state has sufficient adhesion and shaping ability to act as a sealant in the tire and whereby the mass is prevented from flowing at the high temperatures and centrifugal forces to which the tire is exposed during use. 2. Composition as stated in claim 1, for use as a sealant, where the gel content after cross-linking is from 15 to 60% and the initial Mooney viscosity from 30 to 70-. 3. Composition as specified in claim 1 for use as repair compound, where the gel content after cross-linking is from 20 to 95%. 4. Composition as stated in claims 1 to 3, characterized in that the liquid rubber is heat- ■ depolymerized natural rubber. 5. Composition as set forth in claims 1 to 3, characterized in that the low molecular weight elastomer is selected from liquid cis-polyisoprene, liquid polybutadiene, liquid polybutene, liquid ethylene propylene-non-conjugated di-terpolymer g.um, and liquid isobutylene -isoprene copolymer rubber. 6. Composition as stated in claims 1 to 3, characterized in that the high molecular weight elastomer is a conjugated diolefin homopolymer rubber, copolymers of a larger proportion of conjugated diolefin with a smaller proportion of copolymerizable monoethylenically unsaturated monomer, copolymers of isobutylene with a smaller amount of isoprene, ethylene-propylene—non-conjugated diene terpolymers and saturated elastomers. 7. Composition as stated in claims 1 to 3, characterized in that the cross-linking agent is selected from sulfur or sulphur-releasing curing agents, quinoid curing agents, radical-releasing curing agents, polyisocyanate curing agents, and tetrahydrocarbyl titanate ester curing agents. 8. Composition as stated in claims 1 to 7, characterized in that the high molecular weight elastomer is solid cis-polyisoprene rubber. 9. Composition as specified in claims 1 and 2, characterized in that the cross-linking agent is selected from the following, used in the specified quantities: at least 0.5 to 2.0 parts sulfur or sulfur-releasing curing agent, at least 0.5 to 2.0 parts quinoid curing agent , at least Ofl. to 1.0 parts of radical-releasing curing agent, from 2 to 10 parts of polyisocyanate curing agent and from 2 to 10 parts of tetrahydrocarbyltitanate ester curing agent, where the indicated quantity ratios are based on 100 parts by weight of the combined weight of the two elastomers. 10. Composition as set forth in claims 1 to 3, characterized in that the cross-linking agent is selected from among the following in the specified quantities: at least 0.5 to 4 parts by weight quinoid curing agent, at least 0.1 to 1.5 parts by weight free-radical curing agent, from 4 to 25 parts by weight polyisocyanate curing agent and from 4 to 25 parts by weight of tetrahydrocarby1-titanate ester curing agent, the ratio being based on 100 parts by weight of the combined weight of the two elastomers. 11. Puncture sealing composition as stated in claim 2, intended for tubeless tires, characterized by a mixture of at least 50 to 90% by weight low molecular weight liquid elastomer with a Brookfield viscosity at 66°C of 20,000 to 200,000 eps with correspondingly less than 50 to 10% by weight -% high-molecular solid elastomer with Mooney viscosity from 20 to 160 ML-4 at 100°C, and from 2 to 10 parts by weight per 100 parts by weight of the two elastomers of a tetraalkyl-titanate ester as cross-linking agent, where the alkyl groups have from 1 to. 12 C atoms, which mixture is partially cross-linked with said cross-linking agent to give a gel content in the mixture of from 20 to 50% by weight based on the weight of the mixture after measurement in toluene at room temperature, and an initial Mooney viscosity of 40 to 60 ML at room temperature, whereby the compound is prevented from flowing at the elevated temperatures and centrifugal forces to which the tire is subjected in use, and which compound has sufficient adhesion and formability to act as a sealant, in the tire. 12. Puncture sealing compound as stated in claim 11, characterized in that the alkyl groups in the tetraalkyl titanate ester cross-linking agent have from 3 to 8 C atoms, the amount of titanate ester is from 3 to 8 parts per 100 parts by weight of the two elastomers, and the composition is free of fibrous filler. 13. Puncture-sealing composition as stated in claim 12, characterized in that the ter-crosslinking agent of tetraalkyl-titanates is tetra-n-butyl-titanate. 14. Composition as stated in the above claim, characterized in that part of the low molecular weight liquid elastomer is replaced with a tackifying or pastifying compound. 15. Composition as stated in claim 14, characterized in that said tackifying compound is selected from among natural resin esters, aliphatic petroleum resins, polyterpene resins, styrene resins, dicyclopentadiene resins and resins produced by reaction of a mineral oil cleaning residue with formaldehyde and nitric acid catalyst. 16. Puncture-proof tubeless tire with vulcanized rubber tread on a vulcanized rubber carcass reinforced with string-shaped material, which carcass part has a crown under the tread and with sidewalls extending from shoulder areas at the edges of the crown to rim beads with tensile reinforcement and a puncture-sealing layer inside the tire placed across and below the crown at least from one shoulder portion to the other, which puncture sealant consists of a fiber-free blend of a major weight fraction of low molecular weight liquid elastomer with a minor weight fraction of high molecular weight elastomer, partially cross-linked sufficiently to prevent the blend from float at the higher temperatures and centrifugal forces to which the tire is exposed in use, and where it partially transverses bonded mixture has sufficient adhesion and forming ability to act as a sealant in the tire, and that the amount of said low molecular weight elastomer amounts to more than 50 to 90% by weight and the amount of high molecular weight elastomer correspondingly less than 50 to 10% by weight, based on the total weight of the two elastomers, where the low-molecular. elastomer is a liquid rubber with Brookfield viscosity at 66°C from 20,000 to 200,000 eps and said high molecular weight elastomer has a Mooney viscosity from 20 to 60. ML-4 at 100°C, and that the mass contains a cross-linking agent selected from the following, in the stated amounts: at least 0.5 to 2.0 parts by weight of sulfur or sulfur-releasing curing agent, at least 0.5 to 2.0 parts by weight of quinoid curing agent, from 0.1 to 1.0 parts by weight of radical-releasing curing agent. from 2 to 10 parts by weight of polyisocyanate curing agent, and from 2 to 10 parts by weight of tetrahydrocarbyl-titanate ester curing agent, which quantity ratios are based on the weight of 100 parts of the combined weight of the two elastomers, further that the gel content in the mixture in a partially cross-linked state is from 15 to 60% by weight of the mixture measured in toluene at room temperature and the initial Mooney viscosity of the mixture in the partially cross-linked state is from 30 to 70 ML at room temperature. 17. Tire as stated in claim 16, characterized in that said puncture-sealing layer is placed on the inside of said airtight lining. 18..Tyre as specified in claim 16, characterized in that the puncture-sealing layer is laminated between the airtight lining and the inner surface of the casing. 19. Tire as stated in claims 16 to 18, characterized in that the liquid rubber is heat depolymerized natural rubber. 20. Eekk as stated in claim 16 to. 19, characterized in that the low molecular weight elastomer is selected from liquid cis-polyisoprene, liquid polybutadiene, liquid polybutene, liquid ethylene-propylene-non-conjugated diene terpolymer rubber, and liquid isobutylene-isoprene copolymer rubber. 21. Tires as stated in claims 16 to 19, characterized in that the high molecular weight elastomer is selected from conjugated diolefin homopolymer rubbers, copolymers containing a larger proportion of conjugated diolefin with a smaller proportion of copolymerizable monoethylenically unsaturated monomer, copolymers of isobutylene with a smaller amount of isoprene, ethylene -propylene non-conjugated diene terpolymers and saturated elastomers. 22. Tires as stated in claims 16 to 21, characterized in that part of the low molecular weight liquid elastomer is replaced with a tackifying or plasticizing agent fabric. 23. Puncture proof tubeless tire with a vulcanized tread over a vulcanized rubber carcass reinforced with string-shaped material, which carcass has a crown underlying the tread and sidewalls extending from the shoulder areas at the crown to rim beads containing tensile reinforcement, the inside of the tire being coated with an airtight liner, and a puncture-sealing layer inside the tire is arranged transversely under the crown area of the tire at least from one shoulder to the other, which puncture-sealing layer consists of a mixture of at least 50 to 90% by weight low molecular weight liquid elastomer with Brookfield viscosity at 66°C from 20,000 to 200,000 eps. and correspondingly less than 50 to 10% by weight high-molecular solid elastomer having a Mooney viscosity of from 20 to 160 ML-4 at 100°C, and from 4 to 10 parts by weight per 100 parts by weight of the two elastomeric tetraalkyl titanate ester crosslinking agents, wherein the alkyl group has from 1 to 12 C atoms, which mixture is partially crosslinked by the crosslinking agent to form a gel content of 20 to 50% by weight based on the weight of the mixture measured in toluene at room temperature, and an initial Mooney viscosity of 40 to 60 ML at room temperature, whereby the composition is prevented from flowing at the elevated temperatures and centrifugal forces to which the tire is subjected in use, and the composition has sufficient adhesion and malleability to act as sealant in the tire. 24. Tire as stated in claim 23, characterized in that the alkyl group in the tetraalkyl titanate ester cross-linking agent has from 3 to 8 C atoms, the amount of titanium ester is from 3 to 8 parts per 100 parts by weight of the two elastomers, and the composition is free of fibrous filler. 25. Tire as stated in claim 24, characterized in that the tetraalkyl titanate ester cross-linking agent is tetra-n-butyl titanate. 26. Procedure for repairing punctures in tubeless tyres, characterized by applying a repair material to the puncture as specified in claims 1 and 3 to 15. 27. Method as stated in claim 26, character i-, characterized in that the initial Mooney viscosity is from 30 to 100 ML at room temperature. ' 28. Method as stated in claims 26 and 27, characterized in that an additional amount of repair material is applied to the inside of the tire at the puncture area as an enlarged patch with a larger area than the cross-sectional area of the puncture, which patch forms one piece with the repair material in the puncture hole itself, so that repairs in the finished cross-linked structure is held securely in place. 29. Method for repairing a puncture in a tubeless tyre, characterized by pressing into the puncture a plastic repair material that fills the hole and depositing on the inside of the tire at the hole a further amount of repair material as an enlarged patch of repair material inside the tire and in one piece with the hole material, which repair material consists of of a mixture of at least 50 to 90 wt% low molecular weight liquid elastomer with Brookfield viscosity at 66°C from 20,000 to 2QQ,000 eps with correspondingly less than 50 to 10 wt.t*-% high molecular weight solid elastomer with Mooney viscosity from 2Q to 160 ML-4 at 100°C, and from 4 to 25 parts per 100 parts by weight of the two elastomeric tetraalkyl-titanate esters as a cross-linking agent, where the alkyl groups have from 1 to 12 O atoms, after which the introduced repair material undergoes curing conditions so that the mass is at least partially cross-linked to a gel content of from 20 to 80% based on weight on the weight of the mixture, measured in toluene at room temperature, and an initial Mooney viscosity of 40 to 100 ML at room temperature, whereby the mixture is prevented from flowing at the elevated temperature and centrifugal force to which the tire is subjected during use and effectively seals the puncture against air loss. 30, Method as stated in claim 29, characterized in that the alkyl groups in the tetraalkyl-titanate ester^-crosslinking agent have from 3 to 8 C atoms and the amount of titanium esters is from 5 to 15 parts per 100 parts by weight of the two elastomers. 31. Method as stated in claims 26 to 30, characterized in that the tire is a radial tire.