NO803129L - SELF-SEALING PUNCH MASS AND TIRES. - Google Patents

Description

The present invention relates to a puncture sealant designed for tubeless vehicle tyres, and a method for sealing puncture holes in tubeless tires on the basis of a mixture containing more than 5:0% low molecular liquid form rubber, a high molecular. elastomer,.' and an amount of crosslinking agent for the mixture sufficient to provide partial crosslinking.

Preferably, the mixture contains a tackifier. or piastizing compound, which makes it possible to reduce the amount of low molecular elastomer, but the total amount of tackifying or piastizing compound plus low molecular elastomer makes up more than 50% of the mixture.

Puncture-proof tubeless tires are previously known

• and these ix.nehold in the area of the tire that is most exposed

for the 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 having plastic and adhesive properties adapted to

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. Worse, it has proved difficult to provide a compound that will flow into the puncture hole and still have sufficient viscosity to prevent flow at the elevated temperature of up to 120°C and higher that occurs 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 inwards towards the central crown area of the tire and leave the areas near the shoulder sections unprotected. Furthermore, it has proven difficult to

important information

For archival reasons, the Norwegian Patent Office only has access to documents for this generally available patent application that contain handwritten notes, comments or crossing outs, or that may be stamped "Expired" or the like. We have therefore had to use these documents for scanning to create an electronic edition.

Handwritten remarks or comments have been part of the proceedings, and must not be used to interpret the content of the document.

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Please ignore handwritten remarks, comments or crossing outs, as well as any stamps with "Expired" etc. which have the same meaning.

provide a sealant that will maintain the desired balance between viscosity, plasticity, adhesion and formability over

in

longer operating time. in

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. However, such substances remain in a completely uncured state and do not act as actual components in the sealing compound. An embodiment of the present invention uses a larger amount, at least 50%, of liquid elastomer which is an essential part of the seal.

the mixture and is partially covulcanized.with a high molecular weight

fasf 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 puncture sealing compound.

However, a preferred embodiment of the invention comprises the use of tackifying agent and/or plasticizer as an additive, in which case the amount of liquid rubber mass may be below 50% as long as the total amount of tackifying agent plus liquid rubber is above 50%.

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

In contrast to 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 act according to the present

invention. The present sealant therefore contains

against a sufficient amount of curing agent to provide resistance to flow, fiber-based flow barrier is neither necessary nor desirable according to the present invention, which. is preferably 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, even though they may act as sealants, they will sometimes be exposed to "cold flow" or flow at elevated temperatures which is encountered in tires during use. Such flow is undesirable. When the masses 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 a sealant.

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. succeeded 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 low-molecular liquid elastomer and a high-molecular solid elastomer which contains a cross-linking agent in sufficient quantity to provide sufficient curing, so as to prevent the mixture from flowing at the elevated temperature and high centrifugal force occurring under operating conditions. The compound is applied to the puncture hole and

•they are then hardened in situ in the hole. The applicants have found that a mixture of high and low molecular weight elastomers, where the latter is present in an amount of over 50% by weight, and is cured to a. limited degree, sufficient to prevent flow under service conditions, offers new and unique advantages. The high molecular weight elastomer provides stiffness and strength. The low molecular weight elastomer provides the adhesion and malleability necessary for a puncture sealant. Preferably, adhesion ability and

malleability increased by adding 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 removed completely. When the mass is partially cured, the cross-links will be more effective in the high-molecular elastomer and cause it to act as a supporting skeleton or latticework that prevents flow without cross-linking of the low-molecular 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 remarkable in that the high-molecular partially vulcanized portion serves as a stiffened latticework that retains or prevents the low-molecular portion from flowing at elevated temperature and high centrifugal force.

The invention must 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 tubeless tire punctured with a nail,

fig. 6 shows a section on a larger scale, and illustrates how the puncture hole • is sealed with wood. introduction of <■ the sealing material by hje'ilp. of a syringe or needle, and

fig. 7 shows in a similar way as fig. 5, a tire'

which is repaired while sitting on a rim.

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, where the former is present in an amount of more than 50%, based on the weight of the two polymers, and is cross-linked as measured by gel and Mooney viscosity, to a degree that will prevent the mass from flowing at elevated temperature,

shares have sufficient adhesion and malleability to act as-

sealant and repair compound. Preferably, a tackifying agent can be used instead of a part of the low molecular weight rubber, to increase. the 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 - As the aforementioned high-molecular elastomeric component in the 'sealant' according to the invention, any high-molecular solid elastomer that can be cross-linked can be used. Examples are highly unsaturated rubbers based on conjugated diolefins, either homopolymers such as polyisoprene (especially cis-polyisoprene, natural or synthetic), polybutadiene (including polybutadiene with a high cis content), polychloroprene (neoprene), or copolymers which, for example, have a larger proportion of conjugated dienes such as butadiene with a smaller relative amount of mqnoethylenically unsaturated copolymerisable monomers such as styrene or acrylonitrile. Alternatively, elastomers with low unsaturation can be used. in particular butyl rubbers (copolymers of such isoolefins as isobutylene with minor amounts of conjugated dienes such as isoprene), or EPDM types (copolymers of at least two different monoolefins such as ethylene and propylene with a minor amount of non-conjugated dienes 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" gummi type with maximum Brookfield

o 2,000,000" viscosity at 66 C of 600'■ 0'ft0( eps., usually in the range

\.ooo.o©o

20,000 to 004.0-00 eps. Examples are: liquid cis-polyisoprene (e.g. 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 great "stickiness for depolymerized

in

cis-polyisoprene provides a combination of these two elastomers, which

after partial curing according to the present invention

has 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 (e.g. "Piccolyte"

A-10), beta-pinene (e.g. "Piccolyte" S-25), resins of

led by styrene and related monomers (e.g. "Piccolastic" A-5), resins of dicyclopentadiene (e.g. "Piccodiene" 2215), and resins prepared by reacting a mineral oil refinery residue with formaldehyde and with nitric acid catalyst according to to West German patent, no. 1,292,396, 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 adhesive adhesive. mi.dae^T^Fweight 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.

Won-M-gul^ vul<j<*ji f^engedefdrrelation between the two elastomeric be-v^i«/-top- foot» C stand partsVfiik that one gets. a -G-tif-é^-Mooney viscosity at -Kom-toropea^e-trgg ' (the led peak reading ning, which usually f orotera

Jt/Lcc> • 9o week.<WA<v,»n Moovi-cy-K<*rvA.>\\SS

xrun and of the first te-fj\ , 'spk-v^ftéeri pa between 30 and (large rotor, ML) in the finished teve ygb-indjrrg-sb landing; a preferred range is 40 to "fft£' Below said i2^a§*-Mooney viscosity equal to 30, the mixture will tend to flow down from the shoulder area and the side walls of the tire when this is driven at high speeds, as well as out of the hole when the tire is punctured Above mentioned

\ °?*> ^ *J<*4n CUT Vw^oU^i^ «.WsUwkv pU*>

■ stafcte-Mooney viscosity equal to JJ- Q^, the covering ability or sealing ability of the composition will be degraded so that it becomes unusable- for practical purposes.-^Qenno -ovre - qjclåpv

however, not when the mixture is used as a repair gtsffs material. Although there is no critical upper^g-reTTse for the degree of hardening

of the repair material, and^-h-er^ding desired can be carried so far that it will bet^a-RlTes as substantially, full curing in ordinary rubber beajcb-élTdings practice , it is usually . not necessary

It is not possible to use more hardener than to get a starting

• Moortey' viscosity on-out.' —(ML" by luiiiLempididLui")—vetl of- aluGteLlvcTibindlir<g>^/ Mooney the viscosity of the mixture can also be regulated for a given elastomeric mixture according to invention nelsen by the amount of mechanical shear force used to mix the constituents. 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 (eg tetramethyl thiuram disulfide) and common accelerators of sulfur vulcanization. 2) Quinone systernes 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 which. MDI (4, 4 1 -methylene bis-phenylene isocyanate), TDI (tolylene diisocyanate), and PAPI (polymethylene polyphenyl isocyanate) as well as other dimers and. trimers of MDI and TDI.5) Tetrahydrocarbyl titanate ester as described in parallel application ........

The amount of crosslinking agent used will depend.

of the selected elastomers and their ■quantity ratio, as well as the selected cross-linking agent and cross-linking ratio. Usually, an amount is used which is sufficient to prevent the mixture from flowing in the tire at temperatures up to 95°C and speeds up to <*>!NSL knj/hour, while still having sufficient adhesion and formability. 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, mari will be required in amounts from 2 to 10 dph, and usually 3 to 8 dph. 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 area for peroxide or hydroperoxide curing agents (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 depolymerized natural rubber, a gel content measured in toluene at room temperature of between 15 and 60%, preferably 20 to 50% by weight in the cross-linked 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 area will

for optimal gel content vary, depending on the molar weight and quantity ratio of the elastomeric components. As mentioned, it has been shown

say that an initial Mooney viscosity (ML at room temperature) i

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 chosen 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 present masses.

When carrying out the invention for use of the mass

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 includes - a tubeless tire 10 with ordinary vulcanized rubber, tread 11 and side parts 12, 13 - which is applied to a vulcanized rubber carcass 14 reinforced with wire material that ends in rim beads 15, 16 which are provided with normal tensile reinforcement. The entire inside of the carcass is coated with ordinary air-tight lining 17. A layer 18 of sealant according to the invention extends over the inner crown or top surface of the lining 1 covered from one shoulder area to the other,

and at least partially down over each interior side wall.

The sealing effect for 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 casing 14, lining, 17 and the sealing layer 18. The sealing layer will adhere to the nail and prevent loss of air pressure while the nailer 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.

In the event of a modification. of the invention., as shown in Fig

fig. 4, the puncture sealing agent 23 according to the invention is arranged between the inner surface of the carcass '24 and the lining 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 adhesive can be applied (e.g. showered or brushed) to the desired area of the inner surface of the air seal 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 to perform the sealing function during

about. 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 previous curing and still the curing of the applied sealing agent can take place at a lower temperature (e.g. room temperature). The reason is that the titanate ester cure of the elastomer blister will only take place if hydrocarbyl alcohol (obviously formed as a by-product of the cure 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. After the mixture is applied to the tire, however, the hydrocarbyl alcohol will be able to evaporate freely from the layer and curing will take 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 beneficial to introduce the sealing strip in the tire unit•during the 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 over 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 placed on the construction drum, followed by a 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 driven at 110 - 140 km/h and sufficiently loaded to produce an internal temperature of 120°C or higher. After driving at high speed, one observes 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 an internal air temperature of at least 95°C is an important criterion for judging the performance of the e1astomer assembly according to the invention. To assess the puncture sealing ability, the tire is punctured with nails of different sizes, which are then pulled out to measure the air pressure loss in the tyre. 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 one tire to be repaired. ' It is shown to the figure, and particularly fig. 5, where one sees a typical tire to be repaired and which consists of a tubeless tire 10 with a radial ply and ordinary vulcanized rubber tread 11 and sidewalls 12, 13 above a vulcanized rubber carcass 14 reinforced with strings that end in rim beads 15,16 with

inserted tensile reinforcement. The entire carcass side surface in-

in

vendig is coated with an ordinary air-tight lining 17. The tire as shown in the drawing is punctured with a nail 19 which passes through the tread 11, the carcass 14 and the lining 17 and down into the inner cavity.. For repairing the tire after it has taken off 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 of repair material introduced is usually from 50' to 200 g, and should be sufficient to fill the hole completely and form a .surplus in the form of. an enlarged patch part"25, which is formed 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 more In order 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, for example, washing with an aqueous soap solution, rubbing with solvent and/or brushing.

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, 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 sealed 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 into 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 son adheres -to the plug on the inside of the tire as an enlarged head or lump 30. The head 30 whose cross-section is significantly larger than the cross-section of the hole area (on

«r

due to the elasticity of the repair mass, which causes the mass to bppswell to a larger diameter, as it flows out from

the hole on the inside of the tyre), acts as an anchor and holds the plug in the hole during use and prevents the plug from being 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' I

480 g of natural rubber (Standard Malaya gum, Mooney viscosity 64 ML-4-100 o C, weight-average molecular weight 4.7 x 10. ) 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 smooth. 100.8 g of tetra-n-butyl titanate were added and the glue was stirred

again. 24 g of "Antioxidamt 2246" (American Cyanamid), 2,2'-methylir-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 curing is obtained by heating the tire for 24 hours at 93 o 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 with a diameter of 28' cm for one hour at speed

80 kg/h to equalize the temperature of the tire. Eight nails with nail stem diameters of 4.7 mm 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 could not 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 approx

same diameter' as the nail stem. It was more important to observe

that during the withdrawal and immediately after, you only got

• 2

a slight pressure loss in the tire (less than 0.28 kg/cm ) when all the holes are completely sealed with sealant. The tire was then driven further. 16,000' km (200 h 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, were 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% dry matter) 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 27? g tetra-n-butyl titanate added. The blender

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 inner lining of the tyre. Mooney viscosity at roffttempera^r (large rotor, ML) for the fully cured sealant

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 similar, for application to the repair site as described earlier. The masses can. heated to a higher temperature

turn to facilitate the application by increasing the flow or plasticity, but this is not decisive... The specified composition will

"si ■ - •

do not harden as long as the mixture is inside the syringe

or the gun, because evaporation of hydrocarbyl alcohol, which is necessary for the curing 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 one attempt, a tire of the type HR78-15 was punctured

with a 7 cm nail in the middle trillery and the inside of the surface surrounding 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 hollow Jet 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 the covering material then formed 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 loss of air pressure 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 minimal harden-

none have been reached. After the aforementioned two-week period, the inflation pressure was set at 2.0 kg/cm 2 and the tire was run on a 28 cm diameter roller 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

that 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. \% ■ i ■ . sealant At room temperature, the gel content was equal to 33.1% measured in tblue at 50°C for 24 hours.

The tire was put on a coward and inflated. Like a. measure of the sealing effect, four 7 cm long nails were hammered into the tyre,

one in the outer knob, one in the outer rail and two in the inner one

positions. The tire was driven on a cylinder at 80 km/h for periods of 1 hour with constant speed increases of 8 km/h until all the nails were thrown out of the tyre. -' 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 in each of four tires as a 3 mm strip'-'and cured as above. The cured sealant had MLTV values at L rpm between "4*S and SS. and gel content of 18 to 25 The tires were placed on a car, and a 2 1/2" nail driven in along the edge or in the center of the track and the car .drove 160 km in periods at the below 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 minutes

EXAMPLE VI

A sealant that contained 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 224 6 (based on total gum), was mixed as indicated in Example TI. The mass was extruded at 10°C as a 3 mm thick strip in the tire and cured. The puncture sealing effect for this mass was measured by 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 tackifying

<.>i

hydrocarbon polymer resin, .Hercules, Inc..) 16% tetraisopropyl titanate and 10% "Antioxidant 2246" (based on total rubber content) 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 2246" was extruded at 120°C as a flat strip with a thickness of 6.3 mm and a width 20 cm. It was irradiated with an electron beam at .1.4 million volts and dose 20 megarads. The irradiated sample showed a gel content of 29.6% and ML. ■ota££ - Mooney viscosity)at^em-feefa^e-r-a-fctwr equal 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 of Example IV.

EXAMPLE IX

A sealant containing 40 parts by weight natural rubber, 30 parts by weight DPR-4 00 and 30 parts by weight "Struktol 30" as well as 4.2 parts by weight tetra-isopropyl titanate and 0.7 parts by weight "Antioxidant 2246" was mixed as indicated in Example II. Then the mass was extruded in one tire at 115°C as a 3 mm thick strip, cured and subjected to the nail ejection test

from Example IV. Means\sealing effect was 70%..

in; EXAMPLE X

Tc parts butyl "LM 430" (Eniay liquid polyisobutylene, average viscosity-molar wt. 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 of 3 mm thick 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 one cylinder and the nails removed. 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 430 "Royalene 505" and "Piccolyte A100" (poly.terpene resin of

derived from alpha-pinene, softening point 100°C), plus 6% tetra-n-butyl titanate (based on total rubber amount)■ was mixed out in hexane solution and coated on a tire 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 had been 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-buty1-titanate' (based on total rubber mass) was dissolved in hexane and coated on a tire for a .strip 20 cm wide and 3 mm thick after evaporation. After curing 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

1

were removed, without loss of inflation pressure.

EXAMPLE XIII

A sealant that contained 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 coverslip into a strip

20 cm wide and 3 mm thick after evaporation. The sealant was

cured at room temperature, after which! the tire was fitted with a rim and inflated to 2.0 kg/cm 2 . The tire<t>was punctured with two 2.5"

nail and driven at 80 km/h for 20 hours. Then the nails were drawn out, without loss of; inflation pressure.

As described in more detail in the previously mentioned application .... which is filed at the same time, and which is hereby referred to, the curing (the cross-linking etc. is gel] ng to an insoluble state) for unsaturated elastomer with organic titanates only takes place when the mixture exposed to free atmosphere and can be 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 with 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,

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 gelation. The gelation takes place only after evaporation of the solvent and the alcohol. In most cases in practice, the mixing takes place under conditions that suppress gelation (in a closed system without the possibility of evaporation,' or in the presence of volatile alcohol) and then, after the mixture has been formed into the desired shape (e.g. cast , extruded, coated etc), the mixture is allowed to solidify

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 ingredients), the amount and type of titanium esters will determine the hardening speed and degree of hardening.

The necessary time and temperature for titanate hardening

in none again depends on any hydroxy1 constituents that will counteract the hardening and type and:content;of titanate. 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 work faster than butyl titanate. which is again faster than ethylhexyl titanate. Elevated temperature increases the curing rate^ regardless of. type and content of titanate, although solvent curing in the absence of added hydroxy1-inhibitors is rapid at room temp. 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 hydroxy contamination, the surface to volume ratio (the larger the surface

which is exposed the faster the hardening takes place), as well as the relative content and type of titanium testes. It is an essential feature of the hardening that it curable mixture can be treated at an elevated temperature (without the possibility of evaporation) without previous hardening taking place, after which the hardening 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. When, however, the curable inasse is placed in an open atmosphere, where evaporation can take place'and the evolved alcohol ROH. can escape, hardening will take place.' Thin parts such as e.g. coatings deposited from a solution, calendered or extruded films and webs, and similar thin sections (e.g. 5 mm or less), have a higher surface to volume ratio than thicker sections (such as most casts) and have greater possibility of evaporation of the released alcohol ROH. Therefore, such thin sections will harden faster

than thick. ,.

As titanate curing takes place, 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.

As stated, hydroxy1-containing additives have an inhibiting or hindering effect on the 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

tend to harden faster when titanium testers are added. Normally, substantial gelation will only take place'; slowly by evaporation

of solvent. from the solution. Addition of small amounts. volatile alcohol to the gum solutions will prevent too early

■gelling. 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 lasting inhibition effect. After gelation, 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 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 that are equivalent to the conditions to which the final curing agent is exposed, it is of course not practical to. make these measurements on the real sealant that is in use in. the tire itself..

In tires that have been 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 preformed 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 for the construction of 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. The 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 i in tubeless tires, characterized by a mixture of at least 50 to 90% by weight of low molecular weight liquid elastomer in the form of a liquid rubber with Brookfield viscosity at 66°C, of 20,000 to 200n-0 0 0-eps with correspondingly less than 50 to' 10% by weight high-molecular elastomer with Mooney viscosity 20 to 160 ML-4 at 100°C, as well as a cross-linking agent for the elastomer.' more in sufficient quantity 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 a s-t«uit-Mooney viscosity of above 30 ML at ■aromtttmpeid!I"uT , which mixture in a partially cross-linked state has sufficient adhesion and forming 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 t-Mooney viscosity from .30 to , 3. Composition as stated in claim 1 for use as repair ionic mass, 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 stated 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 diene-terpolymer rubber, 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 part of conjugated diolefin with a smaller part of copolymerizable monoethylenically unsaturated monomer, copolymers of isobutylene with a w minor amounts 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, ka r a k- • teris, ert in that the high-molecular elastomer is solid cls-polyisoprene rubber. 9: Composition as specified in claims 1 and 2, characterized in that the cross-linking agent is selected from among the following, used in the specified quantities at least 0.5 to 2.0 parts sulfur or sulfur-releasing hardener, at least 0.5 to 2.0 parts chin.bid hardener, at least 0.1 to 1.0 parts radical-releasing curing agent, from 2 to 10 parts, polyisocyanate curing agent and from 2 to 10 parts tetrahydrocarbyl titanate 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 stated in claims 1 to 13, character, in particular that the cross-linking agent is selected from • the following in the indicated quantities: at least 0.5. to 4 parts by weight of quinoid hardener, at least 0.1 to 1.5 parts by weight radical-releasing curing agent, from 4 to 25 parts by weight polyisocyanate curing agent and from 4 to 2.5 parts by weight tetrahydrocarby 1-titanate ester hardener, where the ratio is 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 tyres, characterized by a mixture of at least 50 to 90% by weight of low molecular weight liquid elastomer with a Brookfield viscosity at 66 C of -8-0. 00^ to 2 -, OxXO . about °20Q ■ 009-. eps with correspondingly less than 50 to 10% by weight of high molecular weight solid elastomer having a Mooney viscosity of from 20 to 160ML-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 an et-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. a d-feesH^ -Mooney viscosity of -4-0—" &01 ML at j^mtamper-a-fe-a-r, whereby the mixture is prevented from flowing at the' elevated temperatures and centrifugal forces to which the tire is subjected during use, and which mixture has sufficient adhesion and forming ability to act as a sealant in the tyre. 12.. Puncture sealant as stated in claim 11, characterized in that the alkyl groups in the tetra-alkyl-1-titanate ester cross-linking agent have from 3 to 8 C- • atoms, - the amount of titanium esters 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 indicated in claim 12, characterized in that the tetraalkyl-titanate ester cross-linking agent is tetra-n-butyl titanate. 14. Composition, as stated in the above 'kr of, characterized in that a 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 natural resin esters, aliphatic petroleum resins, polyterpene resins, styrene resins, dicyclopentadiene resins and resins produced by reacting a mineral. oil cleaner residue with formaldehyde and nitric acid catalyst.. 16. Puncture-resistant 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 under the crown at least from one shoulder portion to the other, which puncture sealant consists of a fiber-free mixture of a major part by weight low molecular weight liquid elastomer with a minor part by weight high molecular weight elastomer, partly cross-linked sufficiently to prevent the mixture from flow at the higher temperatures' and centrifugal forces to which the tire is exposed in use, <:> and where-the partially cross- ■bonded mixture has sufficient adhesion and shaping 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 corresponding to less than 50 to 10% by weight, based on the combined weight of the two elastomers, where the low molecular weight. elastomer is a liquid rubber with Brookfield viscosity at 66 C from 20,000 to 200. 0-00-eps and said high molecular weight elastomer has a Mooney viscosity of 20 to 10-ML-4 at 100°C, and that the mass contains a cross-linking agent selected from the following, in the indicated amounts: at least 0.5 to 2.0 parts by weight of sulfur or sulfur-releasing hardener, at least 0.5 to 2.0 parts by weight; quinoid curing agent, • from 0.1 to 1.0 parts by weight radical-releasing curing agent. from 2 to 10 parts by weight polyisocyanate curing agent, and from 2 to 10 parts by weight tetrahydrocarbyl titanate ester curing agent, which quantity ratios are based on the weight of 100 parts total weight of the two elastomers, further that the gel content in the mixture in a partially crosslinked state is from 15 to 60% by weight of the ^.landing measured in toluene by. room temperature and -ftiS^éfe-Mooney viscosity of the mixture in the partially crosslinked to-, state is from 30 to 7^ ML' at ^^ffHjempe-ra-ttrr. ■ 17. Tire as specified in claim 16, characterized in that said puncture-sealing layer is placed on the inside of said Tufttette lining. 18. Tire as stated in claim 16, characterized in that the puncture-sealing layer is laminated between the airtight lining and the inner surface of the carcass. 19. Tire as specified in claims 16 to 18, characterized in that the floating! rubber is heat depolymerized in natural rubber.. 20. As stated in claims 16 to 19, characterized in that the low molecular weight elastomer is selected from liquid cis-polyisoprene <1>, liquid polybutadiene, liquid end polybutene, liquid ethylene-propylene-non-conjugated dien terpolymer -rubber, and liquid isobutylene-isoprene copolymer rubber. IN 21. Tire as stated in claims 16 to 19, characterized in that the high molecular elastomer is selected from conjugated diolefin-homopol <y> more <g> ummier r-.- copolymers containing a greater proportion of conjugated diolefin with a; smaller proportion of copolymerizable monoethylenic unsaturated monomer, copolymers of isobutylene with a smaller amount of isoprene, ethylene-propylene non-conjugated diene terpolymers and saturated elastomers. ' 22..Tires as specified in claims 16 to 21, characterized in that part of the low molecular weight liquid elastomer has been replaced with a tackifying or pasting substance. 23. Puncture resistant tubeless tire with a vulcanized tread over a vulcanized rubber carcass reinforced with string-shaped material, which carcass has a crown located below the tread and sidewalls extending from the shoulder bead guides' at the crown to rim beads which. contains tensile reinforcement, where the inside of the tire is coated with airtight lining, and a puncture-proofing layer inside the tire is arranged transversely under the crown area of the tire at least from one end shoulder to the other, which puncture-proofing 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-.:Qfrfr eps. and correspondingly less than 50 to 10% by weight of hay, . molecular solid elastomer with a Mooney viscosity of 20 to . 160 ML-4 at 100°C, and from 4 to 10 parts by weight per 100 parts by weight of the two elastomers, tetraalkyl titanate ester as cross-linking agent, where the alkyl group ■has from 1 to 12 C atoms, which mixture is partially cross-linked by the cross-linking 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 a Tauffife-Mooney viscosity of 40 to 6<5.0 ML at room temperature, thereby preventing the mixture from from floating at the elevated temperatures - and centrifugal forces to which the tire is exposed during use, and the mixture has sufficient adhesion and malleability to act as a 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 quantity of titanium esters 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 specified 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, characterized in that the initial Mooney viscosity is from 30 to 100 ML at room temperature. 28. Procedure as stated in claims 26 and 27, k a r a k- ■terized by applying an additional amount of repair material 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 . the sion material in the puncture hole itself, so that repairs in the finished cross-linked structure are held securely in place 29. '' Method for repairing a puncture hole in a tubeless tyre, characterized by pressing into the puncture hole 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 covered and in one piece with the hole material, which repair material consists of of a mixture of at least 50 to 90% by weight of low molecular weight liquid elastomer having a Brookfield viscosity at 66°C of from 20,000 to a-ftfr. 0 0 6 eps with correspondingly less than 50 more 10% by weight high molecular solid elastomer with Mooney viscosity from 20 to 3 60ML-4 at 100°C, and from 4 to 25 parts per t 100 parts by weight of the two elastomeric tetraalkyl titanate esters as cross-linking agent, where the alkyl groups have from 1 to 12 carbon 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% on a 'weight' basis based 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 the puncture effectively closed against air loss. 30, Method as stated in claim 29, characterized in that the alkyl groups in the tetraalkyl-titanate-ester cross-linking 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 claim 26 to] 30, characterized in that the tire is a radial tire.