WO2010100155A1

WO2010100155A1 - Polyurethane elastomers and methods of manufacture thereof

Info

Publication number: WO2010100155A1
Application number: PCT/EP2010/052630
Authority: WO
Inventors: Raymond Kirwan; Eamonn Blair
Original assignee: Raymond Kirwan; Eamonn Blair
Priority date: 2009-03-02
Filing date: 2010-03-02
Publication date: 2010-09-10
Also published as: IE86186B1; GB2468574A; GB201003453D0; IE20100115A1; GB2468574B

Abstract

The invention relates to a polyurethane elastomer comprising an environmentally friendly extender oil with relatively low levels of polycyclic aromatic hydrocarbons (PAH). The polyurethane elastomers of the present invention ideally provide a deflation proof tyre fill composition. The invention also relates to a method to manufacture of polyurethane elastomers comprising the use of environmentally friendly extender oil with relatively low levels of polycyclic aromatic hydrocarbons (PAH); and in a further aspect there is provided a method for manufacturing deflation proof tyres comprising filing a tyre casing with the polyurethane elastomers of the invention, comprising an extender oil with relatively low levels of polycyclic aromatic hydrocarbons (PAH), and curing the polyurethane elastomers to produce a substantially void free elastomeric filing material within the tyre casing.

Description

POLYURETHANE ELASTOMERS AND METHODS OF MANUFACTURE THEREOF

The present invention relates to polyurethane elastomers and methods of manufacture thereof. The polyurethane elastomers of the invention comprise polyurethane (PU) elastomer compositions for filling deflation proof tyres. Thus, the present invention relates especially to deflation proof tyre filling polyurethane elastomer compositions and methods of manufacturing said polyurethane elastomers. The present invention also relates to tyres filled with said PU elastomers.

Background of the Invention

It is known that mixing liquid polyols and isocyanates produces polyurethane polymers of varying elasticity, ranging from very flexible elastomers to semi-rigid and rigid foams. Polyurethane formulations cover an extremely wide range of stiffness, hardness, and densities. Immediately after mixing a polyol and isocyanate, a chemical reaction occurs this is accompanied by a rise in temperature. Blowing agents in the polyol-isocyanate mix start to evaporate due to the heat of the reaction, causing the mixture to expand. The resulting polyurethane polymers are used in a very diverse range of applications, including thermal insulation, upholstery, adhesives and sealants. One of the uses of polyurethane polymers is the manufacturing of wheels and tyres, including rubber tyre treads and deflation proof tyres.

Polyurethane elastomers conventionally used in tyre filling applications are typically composed of 30% to 50% (w/w) of an "extender material", such as an extender or process oil. Such an extender material has an influence on the final Durometer hardness of the resulting polyurethane elastomers. However, the prime function of the extender material is as an unreactive diluent, thereby making the cost per kilo of the polyurethane elastomers lower than that of unextended polyurethane. Extender materials, such as aromatic oils are conventionally obtained from the petroleum industry and generally consist of approximately 77% to 78% aromatic compounds and approximately 3% to 9% polar compounds. These extender oil materials, such as aromatic process oils, contain very high levels of aromatic compounds, the polycyclic aromatic hydrocarbons (PAH or PCA). Polycyclic aromatic hydrocarbons carry an R45 classification and are carcinogenic.

US Patent Nos. 4 416 844 and 5 070 138 are directed to highly aromatic (78%) oil extended polyurethane compositions suitable for use as deflation proof fillings for tyres. US Patent No. 4 416 844, states that aromatic extender oils containing the highest possible amounts of aromatic and polar compounds has better compatibility in the resultant polyurethane elastomer. It has also been determined that extender oil compatibility increases when polyols of high molecular weight are used. However, high molecular weight polyols lead to hard elastomers and so a delicate balance of polyol molecular weight/ oil aromaticity is required. Often achieving this balance to result in an elastomer with desirable properties is difficult.

US Patent No. 4 230 168 is directed to deflation proof tyre filling products where a chlorinated paraffin or dialkyl phthalate plasticiser is used as the extender oil. Such chlorinated paraffin's have a high negative environmental impact. Furthermore, these dialkyl phthalate plasticisers are known to cause negative effects on human health and the environment.

United States Patent Specification No. 5 070 138 A "POLYURETHANE ELASTOMER TYRE FILL COMPOSITIONS AND METHOD OF MAKING SAME" discloses a method for making a polyurethane elastomer tyre fill composition wherein a mixture of a) a low functionality (2.0-2.3) 4,4'-diphenylmethane diisocyanate, such as a carboiimide-modified (2.0 functionality) 4,4'-diphenylmethane diisocyanate and b) a nonreactive diluent, such as an oil extender, is mixed with a polyol, such as polypropylene oxide triol. The reaction mixture is inserted into a tyre casing under pressure and cured therein to form an essentially void-free tyre filler. The tyre fill composition maintains pressure within the tyre during use. No prepolymer step is necessary in the method of US 5 070 138 A.

United States Patent Specification No. 5 070 138 A discloses that a typical polyurethane elastomer is produced by the reaction of two components, an A component containing the isocyanate and a B component, usually a polyol containing the hydrogen donor. According to US 5 070 138 A, tyre fill polyurethane elastomers made in accordance with known prior art methods have used an isocyanate A component consisting of an isocyanate prepolymer. In US 5 070 138 A, the A component consists essentially of a mixture of a low functionality (2.0-2.3) 4,4'-diphenylmethane diisocyante with a nonreactive diluent, such as an extender oil, adjusted to a specific % NCO such that a one-to-one volume mix with the B component can be obtained. According to US 5 070 138 A, the non-reactive diluents used in making the component A mixture with the low functionality 4,4'- diphenylmethane diisocyanate include a number of extender oils. US 5 070 138 A discloses that these oils are complex distillates of crude oil and have a high percentage of aromatic content and that some oils may also contain polar compounds. US 5 070 138 A also discloses that a typical oil for use as a polyurethane extender is sold under the trademark Califlux LP by its manufacturer, Witco Corporation and that such extender oil has about 78 percent aromatics and 9 percent polar compounds with the remainder being saturates. The extender oil of US 5 070 138 A may be present in amounts from at least about 10% up to about 50% and even as high as 60% of the final reaction product. Thus, US 5 070 138 A discloses a polyurethane elastomer tyre filling composition which contains extender oil having a high aromatic content including a high level of polycyclic aromatic hydrocarbons (PAH's).

International Patent Publication No. WO 2008/080557 A "SELF-SEALING COMPOSITION FOR A PNEUMATIC OBJECT" discloses the use of an elastomer composition as a self- sealing composition in a pneumatic object, such as a pneumatic tyre, the elastomer composition comprising at least, as the main elastomer, a styrene thermoplastic (TPS) elastomer and an extension oil at a concentration of between 200 and 700 pee (parts by weight per 100 parts of elastomer). The disclosure of WO 2008/080557 A also relates to an airtight anti-puncture laminate which can be used, in particular, in the above-mentioned pneumatic object, comprising at least a first anti-puncture layer consisting of the self- sealing composition and a second airtight layer, for example based on butyl rubber. The patent specification of WO 2008/080557 A discloses that preferably, the extender oil is selected from the group consisting of oils from the polymerization of olefins, diolefins or monoolefin, Naphthenic oils (a high or low viscosity), aromatic oils, mineral oils, and mixtures of these oils.

United States Patent Specification No. 4 416 844 A "DEFLATION-PROOF PNEUMATIC TYRE AND ELASTOMERIC FILLINGS THEREFOR" discloses a deflation-proof pneumatic tyre comprises a casing and a substantially void-free, preferably oil-containing elastomeric filling material. The tyre casing is injected with a combination comprising a polyol, an organic polyisocyanate and water, in amounts and under conditions sufficient to produce carbon dioxide and form a polyurea-containing polyurethane elastomer in which the carbon dioxide is dissolved in the elastomer, thereby providing a substantially void- free filling material. The formulation permits the addition of a substantial amount of extender oil while retaining an acceptable level of hardness. According to US 4 416 844 A, it is preferred to add at least 10 volume percent, up to about 60 volume percent, of an extender oil while retaining a Durometer hardness of at least 20 on the A scale. US 4 416 844 A discloses that preferably, the extender oil is substantially aromatic and may contain polar compounds. According to US 4 416 844, a particularly effective oil is the aromatic extender oil sold under the trade mark Califlux LP or Bearflex LPO, both sold by the Whitco Chemical Company. Califlux LP comprises about 78 percent aromatics and 9 percent polar compounds, the remainder being saturates. Thus, US 4 416 844 A discloses a deflation-proof tyre comprising an elastomeric filling material; the filling material comprising a polyurea-containing polyurethane elastomer and extender oil and the extender oil used in the process of US 4 416 844 A comprises about 78 percent aromatics.

Problems associated with Prior Art

The conventional extender oils disclosed in the prior art in the patent publications referred to above pose problems in terms of personal and environmental toxicity. Such extender oils, i.e. the aromatic oils used in the prior art, are waste products from the petroleum industry, contain high levels of polycyclic hydrocarbons (PAH's) and are known to act as human carcinogens. As such, the handling and disposal of such materials present both environmental and health hazards. In addition, it is likely that the use of high aromatic content extender materials will be strictly regulated and potentially banned in the future.

The present invention seeks to alleviate these disadvantages and in particular, aims to overcome the toxicity problems associated with conventional polyurethane elastomers, whilst at the same time maintaining the integrity of the resultant elastomers, in terms of hardness, rebound etc for tyre fill applications including in particular, deflation proof tyre fill compositions.

Often, balancing the need to use different non-environmentally toxic materials with the need to obtain elastomers with suitable properties presents technical problems and difficulties. The present invention also seeks to alleviate these problems.

Summary of the Invention

According to a general aspect of the invention, there is provided a polyurethane elastomer comprising an environmentally friendly extender oil with relatively low amounts of polycyclic aromatic hydrocarbons (PAH) compared with known polyurethane elastomers. According to another general aspect of the invention, there is provided a method for manufacture of polyurethane elastomers comprising the use of environmentally friendly extender oil with relatively low levels of polycyclic aromatic hydrocarbons (PAH).

By "relatively low amounts of polycyclic aromatic hydrocarbons" is meant less than 10% by weight; preferably less than 5% and more preferably 3% (w/w).

By "relatively low aromatic(s) content" is meant less than 60% aromatic(s) content; preferably 40-60% aromatic(s) content.

Ideally, the polyurethane elastomers of the present invention are used as deflation proof tyre filling polyurethane elastomers compositions.

According to yet another general aspect of the invention, there is provided the use of a polyurethane elastomer of the invention comprising environmentally friendly extender oil with relatively low levels of polycyclic aromatic hydrocarbons (PAH) in the manufacture of a deflation proof filled tyre.

According to a still further aspect of the invention, there is provided a method for manufacturing deflation proof tyres comprising filing a tyre casing with the polyurethane elastomers of the invention, comprising an environmentally friendly extender oil with reduced levels of polycyclic aromatic hydrocarbons (PAH), and curing the polyurethane elastomers to produce a substantially void free elastomeric filing material within the tyre casing.

Advantageously, this invention involves the use of non-toxic environmentally friendly extender oil materials with relatively low levels of polycyclic aromatic hydrocarbons (PAH) in the manufacture of the polyurethane elastomers. The extender oil of the invention is used as a direct replacement for conventional aromatic oils, chlorinated paraffin's and dialkyl phthalate plasticisers which are currently used in the manufacture of polyurethane elastomers. Thus, this invention overcomes the toxicity problems associated with conventional extenders oils and provides a resultant polyurethane elastomer which is nontoxic. In addition, we have found that the resultant polyurethane elastomer has ideal properties for deflation proof tyre filling applications. It will be understood that the general method of manufacture of the two component polyurethane elastomers involves the preparation of a polyol pre-polymer (Component A) and an isocyanate pre-polymer (Component B), which are combined and cured to form the resultant polyurethane elastomers. The extender oil of the present invention is used in the manufacture of both the polyol prepolymer (Component A) and isocyanate prepolymer (Component B). Alternatively, the extender oil may be used entirely in Component A only or Component B only.

Accordingly, the present invention provides a polyurethane (PU) elastomer for use as a deflation proof tyre fill composition, the polyurethane elastomer produced from a polyol pre-polymer (Component A) comprising a polyol and an isocyanate pre-polymer (Component B) comprising an isocyanate; the polyol pre-polymer and/or the isocyanate pre-polymer comprising an extender oil having relatively low polycyclic aromatic hydrocarbons content.

Preferably, the polyol comprises polyester polyol and/or polyether polyol, or combinations thereof.

Ideally, the polyol has a molecular weight of at least 3000 and has a preferred molecular weight of 6000 to 7000.

The isocyanate may be selected from any one or more of the following group: polymeric diphenylmethane-4-4 Diisocyanate, hexamethylene Diisocyanate, polymethylene polyphenyl isocyanate, m-phenylene Diisocyanate, p-phenylene Diisocyanate, 3,3-dimethyl - 4-4 diphenyl Diisocyanate, 3,3-dimethoxy-4-4 biphenylene Diisocyanate, 2-2,4-4 tetramethyl-4-4 biphenylene Diisocyanate, 3,3-dimethyl-4-4 diphenylamine Diisocyanate, 4'4-diphenyl isopropylidene and/or polymethylene polyphenyl isocyanate.

Advantageously, the polyurethane elastomer includes an extender oil which is an environmentally friendly, substantially non-carcinogenic extender oil having relatively low levels of polycyclic aromatic hydrocarbons (PAH or PCA); preferably, a relatively low level less than 10% (w/w) and more preferably less than 5% (w/w) and most preferably about 3% (w/w). Preferably, the extender oil included in the polyurethane elastomer compositions of the present invention is CATENEX SNR ™ (supplied by Shell Chemicals). This particular extender oil has an aromatic content of less than 60% (specifically about 44% (w/w)) while having a polycyclic aromatic hydrocarbon (PAH) content of 3%. Since the PAH content is low (at 3%), this extender oil is classified as non-carcinogenic.

The extender oil used in the present invention is not derived as a waste product from the petroleum industry.

Preferably, the extender oil is included in an amount from 5% to 60% (w/w).

Advantageously, the extender oil may be included in the polyol pre-polymer (Component A) and/or the isocyanate pre-polymer (Component B).

Ideally, the extender oil has an aromatic content of approximately 44% and a polar content of approximately 1 % (w/w).

Ideally, the extender oil of the present invention has the following properties:

a polycyclic aromatic compound content of about 3% or less by weight; a kinematics viscosity at 40 degrees C of approximately 175 mm²/s; a flash point of 240 degrees C or more; an aromatic hydrocarbon content of about 40-45% by weight; and - a polar compound content between 1.0% and 4.0% (preferably, between 0.1% and 2.5%).

Thus, the extender oil of the present invention has relatively low aromatic content and relatively low polycyclic aromatic hydrocarbons.

Ideally, the polyurethane elastomer includes a tin based amine catalyst, preferably included in an amount in the range from 0.01 % to 2.00% (w/w).

The polyurethane elastomer preferably includes high density polyethylene (HDPE) having a crystalline melting point of 132 degrees Celsius and ideally, is included in an amount in the range from 0.5% to 5.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

Conveniently, the polyurethane elastomer comprises Zeolite (ideally, in the form of Zeolite paste), preferably in an amount in the range from 0.5% to 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

The Zeolite may comprise a Potassium-calcium-sodium alumino-silicate type Zeolite in Castor Oil.

Advantageously, the polyurethane elastomer may comprise an anti-oxidant. The amount of antioxidant included can range from 0% to 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A). The anti-oxidant may comprise a Zeolite.

Preferably, the polyurethane elastomer of the present invention comprises water in an amount from 0% to 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A). The water is added to the polyol pre-polymer (Component A), not to the isocyanate pre-polymer (Component B)

The polyurethane elastomer ideally includes recycled polyurethane or polyisocyanurate powder; preferably in an amount from 0.5% to 6.92 % (w/w) and most preferably, in an amount from 2.9% to 3.0% (w/w).

Advantageously, the polyurethane or polyisocyanurate powder included in the composition of the present invention, was heretofore a waste product which was left over after manufacturing processes including manufacturing of polyurethane or polyisocyanurate insulation. Heretofore, this waste material was dumped in land fills but now can be used as a useful ingredient in the polyurethane elastomer of the present invention.

Advantageously, the polyurethane elastomer of the present invention comprises recycled rubber crumb, preferably having a particle size in the range from 0.5 mm to 1.5 mm, and most preferably, the particle size is 1.0 mm. The inclusion of rubber crumb from waste tyres which have heretofore been a waste product, is a further significant advantage of the polyurethane elastomer compositions of the present invention.

Previously, used vehicle tyres were entirely a waste product with all the environmental implications that entails but now such used vehicle tyres can find useful application as an ingredient in the compositions of the present invention.

Ideally, the polyurethane elastomers of the present invention comprise recycled rubber crumb included in an amount from 1 % to 7% (w/w) and preferably, included in an amount of 5.77% (w/w).

The polyurethane elastomer of the present invention comprise a Polysiloxane based surfactant in hydrocarbon and preferably, in an amount from 0% to 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

The polyurethane elastomer of the present invention may comprise an amine extender such as metaphenylamine diamine. Preferably, the diamine extender is included in an amount from 0.1 % and 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

Advantageously, the polyurethane elastomer of the present invention comprises a compound which absorbs Carbon Dioxide.

Ideally, the carbon dioxide absorbing compound comprises Zinc oxide. Preferably the carbon dioxide absorbing compound is included in an amount in the range from 0% to 5.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

Ideally, the polyurethane elastomer includes Monofunctional isocyanate preferably included in an amount in the range from 0.1 to 5% (w/w) based on the total weight of the isocyanate pre-polymer (Component B).

Potential end applications for a deflation proof tyre include use to deflation-proof and extend the life of off-the-road, industrial and mining tyres. Ideally, a deflation proof tyre manufactured in accordance with the invention has a Durometer hardness in the range, Shore A scale, of 5 to 60 depending on the requirements of the tyre. For instance, a tyre for a golf buggy can have a hardness of 7-8 shore, whereas a tyre for a dumper truck would be much higher. For example, a golf buggy tyre or a ride-on lawn mower vehicle would use a tyre having relatively low Durometer, whereas a high Durometer may be used on heavy mining equipment vehicles. The actual hardness of the tyre depends on the size/weight of the vehicle on which the tyre will be used and its application. For example, a 40 tonne vehicle may need tyres of hardness 35 shore whereas an 80 tonne vehicle may need a tyre having hardness of 55 shore.

Thus, the resulting hardness of a tyre filled with the polyurethane elastomer of the present invention can be controlled by the formulation of the polyurethane elastomer composition. Thus for instance, very hard tyres would be required for tyres on a dumper truck whereas for lighter vehicles such as cars and even golf buggy wheels where very light, non- compressive tyre would be needed on a golf course, a much softer filling composition can be selected.

Thus, in a preferred application, the polyurethane elastomers of the present invention, are deflation proof tyre fill compositions.

In a further aspect, the present invention also provides a method for producing a polyurethane elastomer for use in the manufacture of deflation proof tyre fill, the method comprising the following steps: (a) preparing a polyol pre-polymer (Component A) comprising a polyol;

(b) preparing an isocyanate pre-polymer (Component B) comprising an isocyanate; and

(c) combining the polyol pre-polymer (Component A) with the isocyanate pre-polymer (Component B) and curing to form the polyurethane elastomer; wherein the polyol pre-polymer an/or the isocyanate pre-polymer comprise an extender oil having relatively low levels of polycyclic aromatic hydrocarbons content. Step (c) of the above method is carried out in situ i.e. the components are mixed with each other just before being pumped into a tyre, resulting in a reaction inside the tyre producing the polyurethane elastomer tyre filling composition of the present invention.

Ideally, the polyol pre-polymer comprises polyester polyol and/or polyether polyol, or combinations thereof.

Advantageously, the polyol has a molecular weight of at least 3000 and has a preferred molecular weight in the range from 6000 to 7000.

Ideally, the isocyanate is selected from any one or more of the following group: polymeric diphenylmethane-4-4 Diisocyanate, hexamethylene Diisocyanate, polymethylene polyphenyl isocyanate, m-phenylene Diisocyanate, p-phenylene Diisocyanate, 3,3-dimethyl - 4-4 diphenyl Diisocyanate, 3,3-dimethoxy-4-4 biphenylene Diisocyanate, 2-2,4-4 tetramethyl-4-4 biphenylene Diisocyanate, 3,3-dimethyl-4-4 diphenylamine Diisocyanate, 4'4-diphenyl isopropylidene and/or polymethylene polyphenyl isocyanate.

Advantageously, the method of the present invention further includes an extender oil which is an environmentally friendly, substantially non-carcinogenic extender oil having relatively low levels of polycyclic aromatic hydrocarbons (PAHs or PCAs). The extender oil may be included in the polyol pre-polymer (Component A) and/or the isocyanate pre- polymer (Component B). The extender oil is preferably included in an amount from 5% to 60% (w/w).

The extender oil most preferably has an aromatic content of approximately 44% of which polycyclic aromatic hydrocarbon content is about 3%; and the extender oil preferably has a polar content of approximately 1 % (w/w).

The method of the present invention ideally also includes the step of adding a tin based amine catalyst, ideally, in an amount in the range from 0.01 % to 2.00% (w/w).

In the method of the present invention, the polyurethane elastomer preferably includes high density polyethylene (HDPE) having a crystalline melting point of 132 degrees Celsius. Preferably, the HDPE is included in an amount of 0.5% to 5.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

The method ideally comprises the step of including Zeolite; preferably, the Zeolite is included in an amount from 0.5% to 2.0% (w/w) based on the weight of the polyol pre- polymer (Component A).

Preferably the Zeolite is included in the form of a paste.

Ideally, the Zeolite comprises a Potassium-calcium-sodium alumino-silicate type Zeolite in Castor Oil.

The method may include the step of including an anti-oxidant.

The amount of antioxidant included is preferably, from 0% to 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

Advantageously, the method comprises the step of including water in the polyol pre- polymer (Component A); preferably, in an amount from 0% to 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

The method of the present invention ideally comprises the step of including recycled polyurethane or polyisocyanurate powder; preferably, in an amount in the range from 0.5% to 6.92 % (w/w) and most preferably, in an amount of 2.9% to 3.0% (w/w).

The method of the present invention may also advantageously, comprise the step of including recycled rubber crumb; ideally, having a preferred particle size of 0.5 mm to 1.5 mm. The most preferred particle size is 1.0 mm.

The recycled rubber crumb may be included in an amount in the range from 1 % to 7% (w/w). Most preferably, the recycled rubber crumb may be included in an amount of 5.77% (w/w). The method may comprise the step of including a Polysiloxane based surfactant in hydrocarbon in an amount from 0% to 2.0% (w/w) based on the weight of the polyol pre- polymer (Component A).

The method may comprise the step of including an amine extender such as metaphenylamine diamine. Preferably, the amine extender is included in an amount from 0.1 % and 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

The method may advantageously, comprise the step of including a compound which absorbs Carbon Dioxide. Ideally, the carbon dioxide absorbing compound comprises Zinc oxide. Preferably, the carbon dioxide absorbing compound may be included in an amount in the range of 0% to 5.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

The method may comprise the step of further including an additive comprising a Monofunctional isocyanate preferably in an amount in the range from 0.1 to 5% (w/w) based on the total weight of the isocyanate pre-polymer (Component B).

In another aspect, the present invention also provides a deflation proof tyre filled with the above referred to polyurethane elastomers and also provides a deflation proof tyre produced using the above method of the present invention.

Detailed Description of the Invention

Each component of the invention, comprising the extender oil, polyol pre-polymer (Component A) and isocyanate pre-polymer (Component B) is described in more detail.

EXTENDER OIL

The extender oil of the invention serves as a filler or extender for the polyurethane elastomer. The extender oil of the invention is environmentally friendly extender oil which is not toxic to humans or environmentally hazardous and has relatively low levels (much reduced below the levels of the prior art) of polycyclic aromatic hydrocarbons (PAH), otherwise known as polycyclic aromatic compounds (PCA). Advantageously, the extender oil of the invention does not comprise polycyclic aromatic hydrocarbons (PAH). This ensures that the resultant polyurethane elastomer is environmentally friendly and non-toxic.

Ideally, the extender oil of the invention has an aromatic content of approximately 40% to 60% and a polar content of approximately 1 % to 2.5%.

We have found that this extender oil shows high compatibility with polyurethane systems while maintaining optimum performance properties in the resultant polyurethane.

a polycyclic aromatic hydrocarbons content less than 10%, more preferably, less than 5% and most preferably about 3% by weight; - a kinematics viscosity at 40 degrees C of approximately 175 mm²/s; a flash point of 240 degrees C or more; an aromatic hydrocarbon content is 40-45% by weight; and a polar compound content between 0.1 % and 4.0% (preferably between 1% and 2.5% (w/w).

Ideally, the extender oil is used in amounts of from approximately 5% to 60% (w/w) based on weight of total polyurethane elastomer. It is important to ensure that the correct level of extender oil is used; addition levels up to a maximum of approximately 60% (w/w) based on the weight of total polyurethane elastomer are possible. However, the hardness of the tyre fill decreases greatly at levels higher than this.

In addition, it will be understood that the quantity of the extender oil may be reduced and replaced with the equivalent weight of recycled powdered rubber or other filling materials such as recycled plastic. In this situation, it may be desirable to increase the quantity of catalyst, so as to accelerate the crosslinking time and crosslinking density.

This extender oil of the invention is used in the manufacture of the two component polyurethane elastomers of the present invention. As such, the extender oil of the invention may be used in the manufacture of both the polyol pre-polymer (Component A) and the isocyanate pre-polymer (Component B). This is dependant on the type of metering equipment used to fill the tyre with the elastomers.

The preferred extender oil which may be used is Catenex SNR® (supplied by Shell Chemicals). Ideally, the Catenex SNR® is used in amounts of from 5% to 60% (w/w) on total formulation. Catenex SNR® has an aromatic content of approximately 44% and a polar content of approximately 1 % and is non-carcinogenic. Typical physical characteristics of the Catenex SNR® extender oil are shown in the table below:

CATENEX SNR PHYSICAL & CHEMICAL PROPERTIES

Other oils which may be used are outlined as follows:

Catenex Oil S321 Catenex PH 908

Catenex Oil S232 Catenex PH 908

Catenex Oil S326 Catenex PH941 FU

Catenex Oil S373 Catenex S946

Catenex Oil S379 Catenex S 321

Prorex 15 Flexon 683

Vivatec 200 Plaxolene MS

Further details on polyol pre-polymer (Component A) and isocyanate pre-polymer (Component B) are given below, together with the various additives ideally used in the preparation of the polyurethane elastomers of the present invention.

POLYOL - COMPONENTA

Any polyol may be used in the manufacture of the polyol pre-polymer (Component A) of the invention.

It will be understood that the polyol used may comprise polyester polyol and/or polyether polyol, or combinations thereof.

The minimum molecular weight of the polyol is 3000 is required. Molecular weights under this value may lead to the formation of very soft elastomers. The preferred polyol molecular weight is 6000 to 7000. Higher molecular weight polyol will give better compatibility with extender oil content.

Ideally, the amount of polyol used in the manufacture of the pre-polymer is from approximately 50% to 70% w/w based on the total weight of the resultant pre-polymer Component A.

Ideally, the amount of extender oil used in the manufacture of the pre-polymer is from approximately 5% to 60% % w/w based on the total weight of the resultant pre-polymer.

Component A. The extender oil with reduced levels of polycyclic aromatic hydrocarbons (PAH), as defined above, is used in the preparation of the polyol pre-polymer (Component A).

Further additives may be used in the manufacture of the polyol pre-polymer (Component A) including, but not limited to a catalyst which accelerates the reaction between the polyol and isocyanate; polyethylene fibers which increase the flexural strength of the resulting elastomer; Zeolite (preferably in the form of a paste) which absorbs excess water which would, if present, react with the isocyanate and produce large amounts of carbon dioxide; water (which in the absence of the Zeolite paste may be used to accelerate the reaction; antioxidant which prevents photo or thermal oxidation of the resulting elastomers; and surfactant and/or chain extenders which increase the crosslinking density of the elastomers. These materials are used in formulating the polyurethane elastomers of the present invention so as to produce the desired properties such as the desired hardness needed depending on application/use.

Suitable catalysts include tin based amine catalysts. Ideally, the amount of catalyst used is from 0.01% to 2.00% (w/w) based on the weight of the resultant pre-polymer Component A. The catalyst is vital in the formulation as it accelerates the reaction between the polyol and the isocyanate through the promotion of gel formation and accelerating tack free time.

Polyethylene fibers may be used. These fibers are manufactured from high density polyurethane (HDPE) and have a crystalline melting point of 132 deg C. These long chain polymer fibres serve to transfer load more effectively to the backbone of the polymer by strengthening the intermolecular interactions resulting in a more tough material and are commonly used in rubber manufacture. Ideally, the amount of polyethylene fibers used is from 0.5% to 5.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

Zeolite paste may be used. Ideally, the amount of Zeolite used is from 0.0% to 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

Water may be used. Ideally, the amount of water used is from 0% to 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A). It will be understood that water is only used when Zeolite paste is absent. Water and Zeolite paste are mutually exclusive components.

Recycled polyurethane or polyisocyanurate powder (commonly found in fridges and cold stores etc) may be used as a cost effective filler to increase the hardness of the elastomers. The preferred particle size of the recycled polyurethane or polyisocyanurate powder is between 500 to 1000 microns. The addition of this material produces rigid elastomers with a Shore A hardness of 33. These elastomers may find use in tyre fill applications where maximum compression strength is required (i.e. quarry vehicles). Recycled polyurethane or polyisocyanurate powder may be used in an amount from 0.5% to 6.92 % (w/w). The preferable addition level is 2.9% to 3.0% (w/w).

Recycled rubber crumb as obtained from used vehicle tyres may also be used as cost effective filler. The benefit offered by this material is that it is a cheap easily available and otherwise is a difficult to dispose of material. The preferred particle size of the recycled rubber crumb is from 0.5 mm to 1.5 mm. Most preferably, the particle size of the recycled rubber crumb is 1.0 mm.

Recycled rubber crumb may be used in amounts from 1% to 7% (w/w). The most preferred addition level is 5.77% (w/w).

Suitable antioxidants include a Potassium-calcium-sodium alumino-silicate type Zeolite in Castor Oil. Ideally, the amount of antioxidant used is from 0% to 2.0% (w/w) on the weight of the polyol pre-polymer (Component A).

Suitable surfactants include Polysiloxane resins in hydrocarbon. Ideally, the amount of surfactant used is from 0% to 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

Suitable chain extenders include a diamine extender such as metaphenylamine diamine, ideally, the amount of chain extender used is between 0.1% and 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

Zinc oxide may be used. Ideally, the amount of zinc oxide used is from 0 to 5.0% based on the weight of the polyol pre-polymer (Component A). The function of the Zinc Oxide is to absorb excess carbon dioxide which, if left in the polyurethane elastomers, would produce soft foam.

ISOCYANATE - COMPONENT B

lsocyanates with two or more functional groups are ideally used in the present invention.

Ideally, aromatic TDI based isocyanates are used. Aromatic isocyanates are ideal for the present purposes as they are more reactive and more economical. However, mixes of isocyanates with both aromatic and aliphatic groups may also be used.

Preferably, the isocyanate is selected from polymeric diphenylmethane-4-4 Diisocyanate. Other organic polyisocyanates which could be used in the invention include hexamethylene Diisocyanate, polymethylene polyphenyl isocyanate, m-phenylene Diisocyanate, p-phenylene Diisocyanate, 3,3-dimethyl - 4-4 diphenyl Diisocyanate, 3,3- dimethoxy-4-4 biphenylene Diisocyanate, 2-2,4-4 tetramethyl-4-4 biphenylene Diisocyanate, 3,3-dimethyl-4-4 diphenylamine Diisocyanate, 4'4-diphenyl isopropylidene and/or polymethylene polyphenyl isocyanate.

Preferably, the amount of isocyanate used is from approximately 2 to 15% w/w based on the total composition of isocyanate prepolymer Component B. It will be understood that increasing the percentage of isocyanate will increase the cross-linking of the elastomer and the resultant hardness.

The extender oil with relatively low levels of polycyclic aromatic hydrocarbons (PAH), as defined above, is used in the preparation of isocyanate prepolymer (Component B).

Ideally, the amount of extender oil used is from approximately 5.0% to 60% w/w based on the total weight of combined Component A and Component B.

Ideally, the ratio of isocyanate to extender oil is approximately 1 :9. The preferred ratio of extender oil to isocyanate is 100:6.5 and 100: 13.0. Monofunctional isocyanate may also be used at a level of from approximately 0.1 to 5% w/w based on the total weight of the isocyanate pre-polymer (Component B).

Further additives may be used in the manufacture of the isocyanate pre-polymer (Component B) including, but not limited to, surfactants, antifoams, defoamers, solvents etc.

POLYURETHANE ELASTOMER MANUFACTURING PROCESS

According to a general embodiment of this aspect of the invention, the method for producing polyurethane elastomer of the invention comprises the preparation of polyol pre-polymer, the preparation of isocyanate pre-polymer followed by combining the polyol pre-polymer and isocyanate pre-polymer to form a polyurethane elastomer.

It will be understood that the step of combining the polyol pre-polymer and isocyanate prepolymer to form the polyurethane elastomer may occur in situ in the tyre filling application. As such, the two component prepolymers are combined either in a tyre or in a two component static mixer just before being injected into a tyre. The two component pre- polymers are subjected to the appropriate conditions for curing to form a polyurethane elastomer to take place.

The use of the specific extender oil with relatively low levels of polycyclic aromatic hydrocarbons (PAH), as defined above, results in an environmentally friendly polyurethane elastomer. Furthermore, the specific formulation of the polyurethane elastomers of the present invention permits the addition of a substantial amount of extender oil whilst retaining an acceptable level of hardness. This is desirable for commercial purposes to result in an environmentally acceptable elastomer, which is cost- effective yet retains the desirable physical characteristics that permit it for use in tyre filling applications.

According to one specific embodiment of the invention, the method for producing polyurethane elastomer of the invention comprises the following general process steps:

a) The preparation of the Polyol pre-polymer comprising:

(i) Charging the mixer with the oil extender of the invention and heating to approximately 25 deg C;

(ii) Charging the mixer with a polyol pre-polymer and mixing for approximately five minutes;

(iii) Adding at least one catalyst;

(iv) Adding Zeolite paste or water;

(v) Adding at least one antioxidant, surfactant and at least one chain extender to form a polyol pre-polymer; (vi) Adding inert filler such as recycled powdered polyurethane or polyisocyanurate foam or recycled rubber crumb;

b) The preparation of the lsocyanate pre-polymer comprising

(ii) Adding an isocyanate;

(iii) Adding a monofunctional isocyanate (this may or may not be applicable, depending on the humidity of the environment in which the resins are blended) thereby forming an isocyanate pre-polymer; and c) Combining the Polyol pre-polymer and lsocyanate pre-polymer to form a polyurethane elastomer.

APPLICATIONS

Ideally, the polyurethane elastomers of the invention are used in the manufacture of deflation proof filled tyres. Though it is to be understood that other uses for the polyurethane elastomers of the present invention are also envisaged and are possible within the scope of the invention.

We have found that the use of the extender oil of the invention with an aromatic content of approximately 40% and 80% and a polar content of approximately 1% to 4.0% in the generation of the pre-polymer components, provides a suitable elastomer for use in the manufacture of deflation proof tyres. Ideally, the extender oil used in the manufacture of the prepolymer components of the present invention has the following properties:

a polycyclic aromatic hydrocarbons content of less than 10%, more preferably less than 5% and most preferably, about 3% by weight; - a kinematics viscosity at 40 degrees C of approximately 175 mm²/s; a flash point of 240 degrees C or more; and a polar compound content between 1% and 4% (w/w).

This is the first time that this particular extender oil type has been used in the manufacture of an elastomeric tyre fill composition. It is important to note that many elastomers are used in the manufacture of rubber for tyre treads, however, these elastomeric rubber are not suitable for use as tyre fill composition. The desirable physical properties of rubber tyre treads and tyre fill compositions are very different.

For this particular use, the pre-polymer components are stored separately and are combined in-situ in a tyre. Thus, the pre-polymer components which form the polyurethane are introduced into a tyre under pressure and cured to form essentially void- free tyre filler. Ideally, the tyre fill polyurethane elastomer composition is injected into the tyre through the valve stem via a pumping unit, ensuring the correct mixing ratio of the respective pre- polymers and the appropriate final tyre pressure.

Curing takes place in under 10 hours to cure into a soft, yet resilient elastomer which ensures that the interior of the tyre is completely void free, thereby eliminating any deflations caused by penetrations of the tread or sidewalk We have found that this soft resilient inner core gives the same ride and performance characteristics as air filled tyres but eliminates punctures and under inflation for the life of the tyre.

Hence, the resultant polyurethane elastomer filled tyre is deflation proof and substantially void-free. We have surprisingly found that this tyre fill composition maintains pressure during use and has excellent physical and thermal properties.

Ideally, a deflation proof tyre manufactured in accordance with the present invention has a Durometer hardness in the range, Shore A scale, of 5 to 60. For example, a golf buggy tyre or a ride-on lawn mower vehicle would use a tyre having relatively low Durometer, whereas a high Durometer is needed on heavy mining equipment vehicles. The actual hardness of the tyre depends on the size of the vehicle on which the tyre will be used and its application. For example, a 40 tonne vehicle may need tyres of hardness 35 shore whereas an 80 tonne vehicle may need a tyre having hardness of 55 shore.

The extender oil as well as the M. W. (molecular weight) of the polyol and the polyol/isocyanate ratio in the formulation, influence the final Durometer hardness of the polyurethane elastomer so as to produce the desired hardness as appropriate.

EXAMPLES

The invention will now be illustrated by reference to the following non-limiting Examples which are provided, by way of example only, of a number of embodiments of the compositions of the present invention.

Process Mixing Equipment

Steel mixing vessel with a 'Greaves' type dispersion head 205 L drums with drum taps and a base drum heater or drum jacket Digital balances

Brookfield Viscometer for viscosity determination Vacuum pump Vent driers

Standard Pumping Unit

Raw Materials

Polyol and lsocyanate Compounds including their Chemical Function

Additive Compounds including their Chemical Function

General Method

Manufacturing Process of Polyol (Component A) - General Procedure

The aromatic oils were mixed at 60 RPM and heated to 25 ⁰C. The polyol was added to the mixture and stirred for 5 min followed by the addition of the catalyst and a further 5 min stirring. The polyethylene fibers were slowly added and the mixture was stirred at 120 RPM. The recycled PU or PIR powder, or recycled crumb rubber are added (if applicable). The Zeolite paste or water was added to the mixture and stirred at 180 RPM whereupon the antioxidant and surfactant were added. Using a filter the mixture was decanted into a clean, dry drum and dry nitrogen gas was blanketed over the top of the mixture and the drum was sealed.

Manufacturing Process of lsocyanate (Component B) - General Procedure

The aromatic oils were mixed at 60 RPM and heated to 25 ⁰C for 5 min. The isocyanate was added to the mixture and stirred for 2 min followed by the addition of the multifunctional isocyanate. The drum was sealed immediately and the area above the mixture was blanketed with dry nitrogen gas and stirred for a further 10 min. The mixture was decanted using a filter into a clean, dry drum and dry nitrogen gas was blanketed over the top of the mixture and the drum was sealed.

Manufacturing Process of the Elastomer (General Procedure)

Components A and B are mixed together, typically a 6:4 or 7:3 ratio (polyohisocyanate) depending on the required density of the elastomer. The elastomer will cure within 10 hours and form soft, resilient, durable foam. COMPARATIVE EXAMPLES

Example 1

Materials

SHORE 'A' HARDNESS 31

Example 2

Materials

SHORE 'A' HARDNESS 26 Example 3

Materials

SHORE 'A' HARDNESS 27

Example 4

Materials

SHORE 'A' HARDNESS 24

Example 5

Materials

SHORE 'A' HARDNESS 27

Example 6

Materials

SHORE 'A' HARDNESS 29.9

Example 7 (2/65A)

Materials

SHORE 'A' HARDNESS 33

Example 8 (2/65B)

Materials

SHORE 'A' HARDNESS 30

Example 9 (2/65C)

Materials

SHORE 'A' HARDNESS 37

Example 10(2/68A)

Materials

SHORE 'A' HARDNESS 27

Use of the Elastomer as a Tyre Fill (General Procedure)

Components A and B are injected into a tyre through the valve stem via a specially designed pumping unit.

The pumping unit measures the predetermined mixing ratio of the components, typically a 1 :1 ratio (but may be 6:4 or 7:3 polyohisocyanate) depending on the density required for the elastomer, and mixes the components just prior to injection into the tyre, as well as ensuring the final tyre pressure.

Once injected into the tyre, the elastomer requires 4 hours to cure into a soft, yet resilient elastomer. The interior of the tyre is completely void free.

Although the polyurethane elastomers of the present invention are referred to and described throughout this specification primarily in relation to use as tyre fill compositions, it is to be understood that the polyurethane elastomers of the present invention are also suitable for other uses such as manufacture of car bumpers and motorway safety bollards, for instance.

It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention as defined in the appended claims.

Claims

CLAIMS:

1. A polyurethane (PU) elastomer for use as a deflation proof tyre fill composition, the polyurethane elastomer produced from a polyol pre-polymer (Component A) comprising a polyol and an isocyanate pre-polymer (Component B) comprising an isocyanate; the polyol pre-polymer and/or the isocyanate pre-polymer comprising an extender oil having relatively low polycyclic aromatic hydrocarbons content.

2. A polyurethane elastomer as claimed in Claim 1 , wherein the polyol pre-polymer comprises polyester polyol and/or polyether polyol, or combinations thereof.

3. A polyurethane elastomer as claimed in Claim 1 or Claim 2, wherein the polyol has a molecular weight of at least 3000 and preferably, has a molecular weight in the range from 6000 to 7000.

4. A polyurethane elastomer as claimed in any preceding claim, wherein the isocyanate is selected from any one or more of the following group: polymeric diphenylmethane-4-4 Diisocyanate, hexamethylene Diisocyanate, polymethylene polyphenyl isocyanate, m-phenylene Diisocyanate, p-phenylene Diisocyanate, 3,3-dimethyl - 4-4 diphenyl Diisocyanate, 3,3-dimethoxy-4-4 biphenylene Diisocyanate, 2-2,4-4 tetramethyl-4-4 biphenylene Diisocyanate, 3,3-dimethyl-4-4 diphenylamine Diisocyanate, 4'4-diphenyl isopropylidene and/or polymethylene polyphenyl isocyanate.

5. A polyurethane elastomer as claimed in any preceding claim, wherein the extender oil is an extender oil having relatively low levels of polycyclic aromatic hydrocarbons (PAH) of less than 10% (w/w); and preferably, less than 5% (w/w).

6. A polyurethane elastomer as claimed in any preceding claim, wherein the extender oil has an aromatic content of less than 60%, preferably between 40-60% and most preferably between 40-45%.

7. A polyurethane elastomer as claimed in any preceding claim, wherein the extender oil has a polar content of between 1% and 4.0% (w/w).

8. A polyurethane elastomer as claimed in Claim 7, wherein the polar content is between 1.0 and 2.5% (w/w).

9. A polyurethane elastomer as claimed in any preceding claim, wherein the extender oil is included in an amount in the range from 5% to 60% (w/w).

10. A polyurethane elastomer as claimed in any preceding claim, including a tin based amine catalyst, preferably included in an amount in the range from 0.01% to 2.00% (w/w).

1 1. A polyurethane elastomer as claimed in any preceding claim, wherein the polyurethane elastomer includes high density polyethylene (HDPE) having a crystalline melting point of 132 degrees Celsius and preferably, the HDPE is included in an amount in the range from 0.5% to 5.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

12. A polyurethane elastomer as claimed in any preceding claim comprising a Zeolite in an amount in the range from 0.0% to 2.0% (w/w) based on the weight of the polyol pre- polymer (Component A).

13. A polyurethane elastomer as claimed in Claim 12, wherein the Zeolite comprises a Potassium-calcium-sodium alumino-silicate type Zeolite in Castor Oil.

14. A polyurethane elastomer as claimed in any preceding claim, wherein an antioxidant is included; preferably the amount of antioxidant included is from 0% to 2.0% (w/w) on the weight of the polyol pre-polymer (Component A).

15. A polyurethane elastomer as claimed in any preceding claim comprising water in an amount from 0% to 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

16. A polyurethane elastomer as claimed in any preceding claim, comprising recycled polyurethane or polyisocyanurate powder, preferably in an amount from 0.5% to 6.92 % (w/w) and most preferably in an amount from 2.9% to 3.0% (w/w).

17. A polyurethane elastomer as claimed in any preceding claim comprising recycled rubber crumb, preferably having a particle size in the range from 0.5 mm to 1.5 mm, and most preferably, having a particle size of 1.0 mm.

18. A polyurethane elastomer as claimed in any preceding claim comprising recycled rubber crumb in an amount in the range from 1% to 7% (w/w).

19. A polyurethane elastomer as claimed in any preceding claim comprising a Polysiloxane based surfactant in hydrocarbon in an amount from 0% to 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

20. A polyurethane elastomer as claimed in any preceding claim comprising an amine extender such as metaphenylamine diamine, preferably, the amine extender is included in an amount from 0.1% and 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

21. A polyurethane elastomer as claimed in any preceding claim comprising a compound which absorbs Carbon Dioxide.

22. A polyurethane elastomer as claimed in any preceding claim, wherein the carbon dioxide absorbing compound comprises Zinc oxide.

23. A polyurethane elastomer as claimed in Claim 21 or Claim 22 wherein the carbon dioxide absorbing compound is included in an amount in the range of 0% to 5.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

24. A polyurethane elastomer as claimed in any preceding claim further including an additive comprising Monofunctional isocyanate; preferably included in an amount from 0.1 to 5% (w/w) based on the total weight of the isocyanate pre-polymer (Component B).

25. A method for producing a polyurethane elastomer for use as deflation proof tyre fill compositions, the method comprising the following steps:

(a) preparing a polyol pre-polymer (Component A);

(b) preparing an isocyanate pre-polymer (Component B); and (c) combining the polyol pre-polymer (Component A) with the isocyanate pre-polymer (Component B) and curing to form the polyurethane elastomer, and wherein the polyol pre-polymer and/or the isocyanate pre-polymer comprise an extender oil having relatively low polycyclic aromatic hydrocarbons content.

26. A method as claimed in Claim 25, wherein the polyol pre-polymer comprises polyester polyol and/or polyether polyol, or combinations thereof.

27. A method as claimed in Claim 25 or Claim 26, wherein, the polyol pre-polymer has a molecular weight of at least 3000 and preferably has a molecular weight in the range from 6000 to 7000.

28. A method as claimed in any one of Claims 25 to 27, wherein, the isocyanate pre- polymer is selected from any one or more of the following group: polymeric diphenylmethane-4-4 Diisocyanate, hexamethylene Diisocyanate, polymethylene polyphenyl isocyanate, m-phenylene Diisocyanate, p-phenylene Diisocyanate, 3,3-dimethyl - 4-4 diphenyl Diisocyanate, 3,3-dimethoxy-4-4 biphenylene Diisocyanate, 2-2,4-4 tetramethyl-4-4 biphenylene Diisocyanate, 3,3-dimethyl-4-4 diphenylamine Diisocyanate, 4'4-diphenyl isopropylidene and/or polymethylene polyphenyl isocyanate.

29. A method as claimed in any one of Claims 25 to 28, wherein, the extender oil is an extender oil having relatively low levels of polycyclic aromatic hydrocarbons (PAHs or

PCAs) of less than 10% (w/w); and preferably, less than 5% (w/w).

30. A method as claimed in any one of Claims 25 to 29, wherein the extender oil has an aromatic content of less than 60% and preferably has an aromatic content in the range of 40-45%.

31. A method as claimed in any one of Claims 25 to 30, wherein the extender oil has a polar content in the range of 1-4.0% (w/w), preferably in the range of 1-2.5% (w/w).

32. A method as claimed in any one of Claims 25 to 31 , wherein the extender oil is included in an amount from 5% to 60% (w/w).

33. A method as claimed in any one of Claims 25 to 32, wherein the method comprises the step of including a tin based amine catalyst; preferably included in an amount in the range from 0.01% to 2.00% (w/w).

34. A method as claimed in any one of Claims 25 to 33, wherein the polyurethane elastomer includes high density polyethylene (HDPE) having a crystalline melting point of 132 degrees Celsius and preferably, is included in an amount of 0.5% to 5.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

35. A method as claimed in any one of Claims 25 to 34, wherein comprising in an amount in the range from 0.0% to 2.0% (w/w) based on the weight of the polyol pre- polymer (Component A).

36. A method as claimed in any one of Claims 25 to 35, wherein the Zeolite comprising a Potassium-calcium-sodium alumino-silicate type Zeolite in Castor Oil.

37. A method as claimed in any one of Claims 25 to 36, wherein the method includes the step of including an anti-oxidant, and preferably, the amount of antioxidant used is from 0% to 2.0% (w/w) on the weight of the polyol pre-polymer (Component A).

38. A method as claimed in any one of Claims 25 to 37, wherein the method includes the step of adding water to the polyol pre-polymer (Component A), the water being added in an amount from 0% to 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

39. A method as claimed in any one of Claims 25 to 38, wherein the method includes the step of including recycled polyurethane or polyisocyanurate powder in an amount from

0.5% to 6.92 % (w/w) and preferably, in an amount from 2.9% to 3.0% (w/w).

40. A method as claimed in any one of Claims 25 to 39, wherein the method includes the step of adding recycled rubber crumb, preferably, having a particle size of 0.5 mm to 1.5 mm, and most preferably having a particle size of 1.0 mm.

41. A method as claimed in Claim 40, wherein recycled rubber crumb is added in an amount from 1% to 7% (w/w).

42. A method as claimed in Claim 41 , wherein the rubber crumb is added in an amount of 5.77% (w/w).

43. A method as claimed in any one of Claims 25 to 42, wherein the method includes the step of including a Polysiloxane based surfactant in hydrocarbon in an amount from 0% to 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

44. A method as claimed in any one of Claims 25 to 43, wherein the method includes the step of including an amine extender such as metaphenylamine diamine, preferably in an amount from 0.1% and 2.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

45. A method as claimed in any one of Claims 25 to 44, wherein the method includes the step of including a compound which absorbs Carbon Dioxide.

46. A method as claimed in Claim 45, wherein the carbon dioxide absorbing compound comprises Zinc oxide.

47. A method as claimed in Claim 45 or Claim 46, wherein the carbon dioxide- absorbing compound is included in an amount in the range of 0% to 5.0% (w/w) based on the weight of the polyol pre-polymer (Component A).

48. A method as claimed in any one of Claims 25 to 47, wherein the method includes the step of further including an additive comprising a Monofunctional isocyanate, preferably included in an amount in the range of 0.1 to 5% (w/w) based on the total weight of the isocyanate pre-polymer (Component B).

49. A deflation proof tyre filled with a polyurethane elastomer as claimed in any of Claims 1 to 24.

50. A deflation proof tyre produced by the method as claimed in any of Claims 25 to 49.