Load bearing belt made from flame retardant thermoplastic polyurethane (TPU)

Abstract

The invention is directed to a load bearing belt extruded from a composition comprising a thermoplastic polyurethane with low abrasion and good mechanical properties, as well its respective production process.

Description

[0001] Load Bearing Belt made from Flame Retardant Thermoplastic Polyurethane (TPU)

[0002] The current invention is directed to a load bearing belt made from flame retardant thermoplastic polyurethane (TPU). Load bearing belts are used in e.g. elevators, roping arrangements, drive belts for machines, passenger conveyors and the like.

[0003] US 6,295,799 and US 6,739,433 describe belts used in suspending an elevator car and counterweight within an elevator system. A conveyor handrail construction is shown in US 4,982,829. An example passenger conveyor drive belt is shown in U.S. Pat. No. 6,540,060. Beside good flame retardancy, and good overall mechanical properties these belts need good resistance against abrasion, because the dust form abrasion negatively effects the operation of those belts. One example to overcome this disadvantage is the coextrusion of said belts as outlined e.g. in WO2011141068A1 , whereby a thermoplastic polyurethane with little or no flame retardant is applied to the surface of the belt.

[0004] For that it is an ongoing demand to provide the market with thermoplastic polyurethane, with good mechanical properties, good flame-retardant properties, and high abrasion resistance.

[0005] It was surprisingly found that a thermoplastic polyurethane composition comprising polyphos- phonate fulfills all these requirements. According to the present invention, the problem is solved by a load bearing belt extruded from a composition comprising a thermoplastic polyurethane, the thermoplastic polyurethane being the reaction product of a diisocyanate, a polyol and a chain extender, wherein the composition further comprises a polyphosphonate in an amount between 0 weight-% and 25 weight-%, preferably between 5 weight-% and 20 weight-%, more preferably between 8 weight-% and 15 weight-% referring to the whole composition being 100 weight-%.

[0006] A first aspect of the invention and embodiment 1 is directed to a load bearing belt extruded from a composition comprising a thermoplastic polyurethan, the thermoplastic polyurethane, preferably being the reaction product of a diisocyanate, a polyol and a chain extender, wherein the composition further comprises a polyphosphonate in an amount between 0 weight-% and 25 weight-%, preferably between 5 weight-% and 20 weight-%, more preferably between 8 weight-% and 15 weight-% referring to the whole composition being 100 weight-%. The term composition indicates that the composition does not comprise the thermoplastic polyurethane only, but may comprise other polymers, additives, or auxiliaries, or a mixture thereof. The term comprises means that the respective substance is comprised, but other substances may be comprised as well. In a further embodiment the term “comprising” has the meaning of “consisting of”.

[0007] Preferably, the sum of the amounts of the polyphosphonate and the thermoplastic polyurethane is between 50 weight-% and 100-weight %, referring to the total amount of the composition being 100 weight-%, more preferably between 60 weight-% and 100-weight %, more preferably between 70 weight-% and 100 weight %, more preferably between 80 weight-% and 100-weight %, more preferably between 90 weight-% and 100-weight %. In a preferred embodiment 2 according to the precedent embodiments or one of their preferred embodiments, the sum of the amounts of the polyphosphonate and the thermoplastic polyurethane is between 50 weight-% and 100-weight %, referring to the total amount of the composition being 100 weight-%, more preferably between 60 weight-% and 100-weight %, more preferably between 70 weight-% and 100 weight %, more preferably between 80 weight-% and 100-weight %, more preferably between 90 weight-% and 100-weight %.

[0008] The belt may comprise a wire, preferably a wire made of steel. Preferably, the load bearing belt is an elevator belt. In a preferred embodiment 3 according to one of the precedent embodiments, or one of their preferred embodiments, the belt according to any of the precedent claims, comprises a wire, preferably a wire made of steel.

[0009] In a preferred embodiment 4 according to the precedent embodiment 3, or one of its preferred embodiments the steel wire comprised filaments of which the steel wire is formed. The steel preferably is characterized as follows: 0.40 weight-% (a minimum carbon content of greater than 0.65%), a manganese content of 0.40 weight-% to 0.70 weight-%. The steel preferably has a silicon content of 0.30 weight-%, a maximum sulfur content of 0.03 weight-%, a maximum phosphorus content of 0.30 weight-%, or a mixture thereof. Only trace amounts of copper, nickel and / or chromium are present. A minimum carbon content of 0.8 weight-% (e.g., 0.775 weight-% to 0.825 weight-%) refers to high tensile strength steel.

[0010] In a preferred embodiment 5 according to the precedent embodiment 4, or one of their preferred embodiments the steel comprises all features as outlined in embodiment 4 and its preferred embodiments. The wire from steel preferably is composed of filaments preferably having a tensile strength of at least 2 x 103MPa, more preferably more than 2,7 x 103MPa, more preferred more than 3 x 103MPa, more preferred more than 3.5 x 103MPa, and most preferred more than 4.2 x 103MPa. Such high tensile strength can be obtained by cold drawing the filament from steel having carbon content exceeding 0.65 weight-% to a sufficient degree. Tensile strength is defined as the perpendicular cross-sectional area of the filament (square millimeters [mm2] ratio of the filament divided by breaking load (Newtons [N]). It is highly preferred that the filament having the largest diameter is made of steel so as not to cause other problems such as electrolytic corrosion (e.g., if the filament is made of copper), reduced breaking loads (as steel is one of the metals with the highest expected tensile strength), uneven loads, and the like.

[0011] In a preferred embodiment 6 according to one of the precedent embodiments, or one of their preferred embodiments the load bearing belt is an elevator belt.

[0012] Typically, he thermoplastic polyurethane of the belt, is prepared by reacting an organic isocyanate, preferably an organic diisocyanate, with a polyol, preferably having two functional groups reactive with isocyanate, also referred to as polymer diol, and a chain extender. In a preferred embodiment 7 according to one of the precedent embodiments, or one of their preferred embodiments the thermoplastic polyurethane of the belt, is prepared by reacting an organic isocyanate, preferably an organic diisocyanate, with a polyol, preferably having two functional groups reactive with isocyanate, also referred to as polymer diol, and a chain extender. The compound reactive with isocyanate preferably has a number average molecular weight between 0.5 x 103g / mol and 100 x 103g / mol, more preferably between 0.5 x 103g / mol and 10 x 103g / mol. The chain extender preferably has a molecular weight between 0.05 x 103g / mol and 0.499 x 103g / mol. The reaction preferably takes place in the presence of a catalyst. The composition in preferred embodiments comprises an auxiliary, an additive, or a mixture thereof.

[0013] The number average molecular weight Mn and the weight average molecular weight in the context of this invention preferably is determined by gel permeation chromatography, more preferably according to DIN EN ISO 13885-2:2020, no salt is used, instead of N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF) weight is determined at 60°C.

[0014] The components organic isocyanate, preferably diisocyanate, compound reactive with isocyanate, in a preferred embodiment a polymer diol, and the chain extender are also addressed individually or together as building components. The building components, if applicable, including the catalyst and / or the auxiliary and / or the additive are also called input materials. To adjust the hardness and melt flow index of the thermoplastic polyurethane (TPU), the molar ratios of the quantities of the building components, can be varied, whereby the hardness and melt viscosity increase with increasing content of isocyanate and chain extender, while the melt flow index decreases.

[0015] Preferably, the composition has a hardness between 70 and 60 Shore D, more preferably between 80 Shore A and 100 Shore A, preferably measured according to DIN ISO 7619-1 : 2016. In a preferred embodiment 8 according to one of the precedent embodiments, or one of their preferred embodiments the composition has a hardness between 70 and 60 Shore D, more preferably between 80 Shore A and 100 Shore A, preferably measured according to DIN ISO 7619-1 : 2016.

[0016] The molecular weight of the thermoplastic polyurethane may vary in broad ranges. Preferably, the thermoplastic polyurethane has a weight-average molecular weight of at least 0.04 x 106g / mol, more preferably at least 0.06 x 106g / mol, more preferably at least 0.07 x106g / mol, and more preferably at least 0.08 x106g / mol. In a preferred embodiment 9 according to one of the precedent embodiments, or one of their preferred embodiments the thermoplastic polyurethane has a weight-average molecular weight of at least 0.04 x 106g / mol, more preferably at least 0.06 x 106g / mol, more preferably at least 0.07 x106g / mol, and more preferably at least 0.08 x106g / mol. The upper limit for the weight-average molecular weight of TPU is generally determined by the processability and the desired range of properties. Preferably the weight-average molecular weight does not exceed 0.5 x106g / mol, more preferably 0.4 x106g / mol, more preferably 0.25 x106g / mol, and more preferably 0.2 x106g / mol.

[0017] In a preferred embodiment 10 according to one of the precedent embodiments, or one of their preferred embodiments the isocyanate used for the synthesis of the thermoplastic polyurethane is a diisocyanate. Further preferred the isocyanate is selected from the group consisting of aliphatic, cycloaliphatic, araliphatic and aromatic isocyanates, in particular aliphatic, cycloaliphatic, araliphatic and aromatic diisocyanates or is a mixture thereof.

[0018] The isocyanate more preferably is selected from the group consisting of tri-, tetra-, penta-, hexa- , hepta- and / or octamethylene diisocyanate, 2-methyl-pentamethylene 1 ,5-diisocyanate, 2-ethyl- butylene-1 ,4-diisocyanate, 1 ,5-pentamethylene diisocyanate (PDI), 1 ,4- butylene-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (isophorone diisocyanate, IPDI), 1 ,4- bis(isocyanatomethyl)cyclohexane and / or 1 ,3-bis(isocyanatomethyl)cyclohexane (HXDI), 2,4-paraphenylene diisocyanate (PPDI), 2,4-tetramethylene xylene diisocyanate (TMXDI), 4,4'-, 2,4'- and 2,2'-dicyclohexylmethane diisocyanate (H12MDI), 1 ,6-hexamethylene diisocyanate (HDI),1 ,4-cyclohexane diisocyanate, 1-methyl-2,4- and / or -2, 6-cyclohexane diisocyanate, 2,2'— diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 1 ,5-naphthylene diisocyanate (NDI), 2,4- toluene diisocyanate, 2,6-toluene diisocyanate (TDI), 3,3'-dimethyl-diphenyl diisocyanate, 1 ,2-diphenylethane diisocyanate and / or phenylene diisocyanate, or is a mixture thereof. Preferably, the isocyanate is 2,2'- diphenylmethane, 2,4'- diphenylmethane or 4,4'-diphenylmethane diisocyanate (MDI), or is a mixture thereof, especially preferred is 4,4'-diphenylmethane diisocyanate.

[0019] In a preferred embodiment 11 according to one of the precedent embodiments, or one of their preferred embodiments, the isocyanate is 2,2'- diphenylmethane, 2,4'- diphenylmethane or 4,4'- diphenylmethane diisocyanate (MDI), or is a mixture thereof, especially preferred is 4,4'-diphe- nylmethane diisocyanate.

[0020] Suitable polyols are in principle known. Preferably, the polyol, has on statistical average at least 1.8 and at most 2.4 Zerewitinoff-active hydrogen atoms. This number is also referred to as the functionality of the polyol and indicates the quantity of the isocyanate-reactive groups of the molecule calculated theoretically down to one molecule from a quantity of substance. The functionality is preferred between 1.8 and 2.2 and especially preferred 2. A polyol with the functionality of 2 is also referred to as polymer diol. In a preferred embodiment 12 according to one of the precedent embodiments, or one of their preferred embodiments, the polyol, has on statistical average at least 1.8 and at most 2.4 Zerewitinoff-active hydrogen atoms. This number is also referred to as the functionality of the polyol and indicates the quantity of the isocyanate-re- active groups of the molecule calculated theoretically down to one molecule from a quantity of substance. The functionality is preferred between 1.8 and 2.2 and especially preferred 2. A polyol with the functionality of 2 is also referred to as polymer diol.

[0021] In a preferred embodiment 13 according to one of the precedent embodiments, or one of their preferred embodiments the polyol has a number average molecular weight between 0.5 x103g / mol and 8 x103g / mol, more preferably between 0.6 x 103g / mol and 6.0 x 103g / mol, even more preferred between 0.6 x 103g / mol and 3.0 x 103g / mol.

[0022] Preferably the polyol is linear and is a single polyol, or is a mixture of at least two polyols, in which case the mixture meets the above requirements. Preferably, the polyol is selected from the group consisting of polyether diol and polycarbonate diol or is a mixture thereof. Particularly preferred the polyol comprises polyether polyol. In particular, the polyol comprises a polyether diol, further preferred selected from the group of poly-ethanediol, poly-1 , 3-propanediol and poly- 1 ,4-butane diol, or a mixture thereof, more preferred the polyether is polytetrahydrofuran (PTHF).

[0023] In a preferred embodiment 14 according to one of the precedent embodiments, or one of their preferred embodiments the polyol is selected from the group consisting of polyether diol and polycarbonate diol or is a mixture thereof. Particularly preferred the polyol comprises polyether polyol.

[0024] In a preferred embodiment 15 according to one of the precedent embodiments, or one of their preferred embodiments, the polyol comprises a polyether diol, further preferred selected from the group of poly-ethanediol, poly-1 , 3-propanediol and poly-1 , 4-butane diol, or a mixture thereof, more preferred the polyether is polytetrahydrofuran (PTHF).

[0025] In a preferred embodiment 16 according to one of the precedent embodiments, or one of their preferred embodiments the polyetherpolyol, preferably the polytetrahydrofuran, has a number average molecular weight between 0.5 x 103g / Mol and 2 x 103g / Mol, more preferably between 0.6 x 103g / Mol and 1.5 x 103g / Mol, even more preferably between 0.8 x 103g / Mol and 1.2 x 103g / Mol, and most preferably 1.0 x 103g / Mol.

[0026] Polyetherpolyol has the advantage that it is more stable against hydrolysis and thus will be applied in applications where this is a requirement.

[0027] In a preferred embodiment 17 according to one of the precedent embodiments, or one of their preferred embodiments, the polyol comprises a polycarbonate diol, preferably an aliphatic polycarbonate diol. A preferred polycarbonate diol is a polycarbonate diol based on alkane diol. In a preferred embodiment the production of polycarbonate diol is carried out by polycondensation of phosgene with a diol or by ring-opening polymerization of cyclic carbonates, or by transesterification of a carbonic acid diester.

[0028] In a preferred embodiment 18 according to one of the precedent embodiments, or one of their preferred embodiments the polycarbonate diol is an OH-difunctional polycarbonate diol, preferably an OH-difunctional aliphatic polycarbonate diol. A preferred polycarbonate diol is based on butanediol, pentanediol or hexanediol.

[0029] In a preferred embodiment 19 according to one of the precedent embodiments, or one of their preferred embodiments the polycarbonate diol is based on 1 ,4-butanediol, 1 ,5-Pentanediol, 1 ,6- Hexanediol, and 3-Methylpentane-(1 ,5)-diol, or a mixture thereof, more preferred the polycarbonate diol is based on 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, or a mixture thereof.

[0030] In a preferred embodiment 20 according to one of the precedent embodiments, or one of their preferred embodiments the polycarbonate diol is based on a mixture of 1 ,4-butanediol and 1 ,6- hexanediol, a mixture of 1 ,5-pentanediol and 1 ,6-hexanediol or is a polycarbonate diol based on 1 ,6-hexanediol or is a mixture thereof.

[0031] In a preferred embodiment 21 according to one of the precedent embodiments, or one of their preferred embodiments, the polycarbonate diol has a number average molecular weight Mn in the between 1 x 103and 5 x 103g / mol, more preferred between 1.4 x 103g / mol and 3 x 103g / mol, more preferred between 1 .8 x 103g / mol and 2.2 x 103g / mol, more preferred 2.0 x 103g / mol.

[0032] Polycarbonate diols have a better permeability for microwave, less dirt uptake and show better flame retardancy.

[0033] Suitable chain extenders are in principle known. In a preferred embodiment 22 according to one of the precedent embodiments, or one of their preferred embodiments the chain extender is an aliphatic, araliphatic, aromatic, cycloaliphatic compound, or a mixture thereof, preferably with a molecular weight of 50 g / mol to 499 g / mol.

[0034] In a preferred embodiment 23 according to one of the precedent embodiments, or one of their preferred embodiments the chain extender has 2 isocyanate-reactive compounds. These isocyanate reactive compounds are also referred to as functional groups. Preferred chain extenders are diamines and / or alkanediols. Further preferred the chain extender comprises 2 to 10 carbon atoms in the alkylene radical, more preferably 3 to 8 carbon atoms. The alkandiol preferably has only primary hydroxyl groups.

[0035] Preferably, the chain extender is selected from 1 ,2-ethylene glycol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,6-hexanediol, hydroquinone bis (beta-hydroxyethyl) ether (HQEE) and di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona- or decaalkylene glycols, also preferred corresponding oligo- and / or polypropylene glycols or is a mixture thereof. In a preferred embodiment 24 according to one of the precedent embodiments, or one of their preferred embodiments the chain extender is selected from 1 ,2-ethylene glycol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,6-hexanediol, hydroquinone bis (beta-hydroxyethyl) ether (HQEE) and di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona- or decaalkylene glycols, also preferred corresponding oligo- and / or polypropylene glycols or is a mixture thereof.

[0036] In a preferred embodiment 25 according to one of the precedent embodiments, or one of their preferred embodiments the chain extender is selected from the group of 1 ,2-ethylene glycol, 1 ,3-propanediol, 1 ,4-butanediol, and 1 ,6-hexanediol, or is a mixture thereof, more preferred the chain extender is 1 ,3-propanediol, 1 ,4-butanediol, or a mixture thereof, most preferred the chain extender is 1 ,4-butanediol.

[0037] The belt according to this invention comprises a polyphosphonate. Preferably, the polyphosphonate is an aromatic polyphosphonate, preferably the polyphosphonate preferably has a melting point between 100 °C and 115 °C, more preferably between 104 °C and 110 °C. Preferably, the P content of the polyphosphate is between 5 weight-% and 20 weight-%, referring to the total amount of the polyphosphonate being 100 weight-%.

[0038] In a preferred embodiment 26 according to one of the precedent embodiments or one of their preferred embodiments the polyphosphonate is an aromatic polyphosphonate, preferably the polyphosphonate preferably has a melting point between 100 °C and 115 °C, more preferably between 104 °C and 110 °C.

[0039] In a preferred embodiment 27 to one of the precedent embodiments or one of their preferred embodiments the P content of the polyphosphate is between 5 weight-% and 20 weight-%, referring to the total amount of the polyphosphonate being 100 weight-%.

[0040] In a preferred embodiment 28 according to any of the precedent embodiments or one of their preferred embodiments the polyphosphonate comprises the structural element as outlined in Formula 1.

[0041] Formula 1 : wherein:

[0042] R is an organic rest with 0 to 20 carbon atoms, more preferably between 5 and 15 carbon atoms, more preferably the rest comprises an aromatic structure, more preferred R is an rest as outlined in Formula 2:

[0043] Formula 2:

[0044] In a preferred embodiment 29 the belt according to any of the precedent embodiments or one of their preferred embodiments the polyphosphonate is the polyphosphonate with the CAS-Num- ber 68664-06-2.

[0045] In a preferred embodiments 30 the belt according to any of the precedent embodiments or one of their preferred embodiments the structural element as outlined in Formula 1 is comprised in the polyphosphonate with between 20 mol-% and 100 mol-%, referring to the total amount of polyphosphonate being 100 mol-%, more preferably between 40 mol-% and 100 mol-%, more preferably between 60 mol-% and 100 mol-%, more preferably between 80 mol-% and 100 mol- %, more preferably between 90 mol-% and 100 mol-%.

[0046] In a preferred embodiments 31 according to any of the precedent embodiments or one of their preferred embodiments the weight average molecular weight of the polyphosphonate is between 3 x 103mol and 100 x 103mol, more preferably between 20 x 103mol and 80 x 103mol, more preferably between 40 x 103mol and 70 x 103mol, more preferably between 50 x 103mol and 60 x 103mol. The amount of the polyphosphonate is limited to have good flame retardancy and good mechanical property of the belt. The phosphonate shows less migration to the surface of the belt and enhances processability of the composition for extruding the belt.

[0047] The composition may comprise a further phosphorous containing additive beside the polyphosphonate, preferably a phosphorous containing flame retardant. The flame retardant typically is a single substance or is a mixture of several substances. Preferably, the phosphorus containing additive, preferably phosphorus containing flame retardant, and the polyphosphonate is comprised in the composition with an amount between 1 weight-% and 25 weight-%, more preferably between 5 weight-% and 20 weight-%, more preferably between 8 weight-% and 15 weight-%.

[0048] In a preferred embodiment 32 according to one of the precedent embodiments, or one of their preferred embodiments, the composition, beside the polyphosphonate comprises a further phosphorous containing additive, preferably a phosphorous containing flame retardant. The flame retardant is a single substance or is a mixture of several substances.

[0049] In a preferred embodiment 33 according to the precedent embodiment 32 or one of their preferred embodiments, the phosphorus containing additive, preferably phosphorus containing flame retardant, and the polyphosphonate is comprised in the composition with an amount between 1 weight-% and 25 weight-%, more preferably between 5 weight-% and 20 weight-%, more preferably between 8 weight-% and 15 weight-%.

[0050] In a preferred embodiment 34 according to one of the precedent embodiments 32 to 33, or one of their preferred embodiments, the phosphorous containing additive, preferably the flame retardant, is liquid, preferably is liquid at a temperature of 21 °C.

[0051] This flame retardant beside its flame-retardant properties preferably also has a softening effect for the composition.

[0052] In a preferred embodiment 35 according to one of the precedent embodiments 32 to 34 or one of their preferred embodiments the phosphorus containing flame retardant is a derivative of the phosphorus acid, of the phosphonic acid, or of the phosphinic acid, or is a mixture thereof, preferably the derivatives of the phosphoric acid, phosphonic acid, or phosphinic acid involve salts with an organic or an inorganic cation or involve an organic ester. In a preferred embodiment 36 according to the precedent embodiment 35 or one of their preferred embodiments the organic ester involves an alkyl ester, and in another preferred embodiment it involves an aryl ester, more preferred all of the hydroxy groups of the corresponding phosphorus-containing acid have been esterified. The phosphoric acid ester preferably is a triester, more preferred a trialkyl phosphate or a triaryl phosphate, preferably triphenyl phosphate.

[0053] In a preferred embodiment 37 according to one of the precedent embodiments 35 to 36 or one of their preferred embodiments the phosphoric acid ester preferably is a tri-ester, more preferred a trialkyl phosphate or a triaryl phosphate, preferably triphenyl phosphate.

[0054] In a preferred embodiment 38 according to one of the precedent embodiments 35 to 37 or one of their preferred embodiments the phosphoric ester has the general Formula 3:

[0055] Formula 3: where R denotes substituted alkyl, cycloalkyl, or phenyl groups, and n is an integer in the range from 1 to 15.

[0056] If R in the general formula (I) is an alkyl moiety, alkyl moieties that preferably are used are those having from 1 to 8 carbon atoms. The cyclohexyl is a preferred example of the cycloalkyl groups. In other preferred embodiments R denotes a phenyl or alkyl-substituted phenyl. Preferably, n is 1 , or an integer from 3 to 6.

[0057] In a preferred embodiment 39 according to one of the precedent embodiments 35 to 38 or one of its preferred embodiments the flame retardant is an aromatic phosphoric acid ester.

[0058] In a preferred embodiment 40 according to one of the precedent embodiments 35 to 39 or one of their preferred embodiments the phosphoric acid ester is selected from the group consisting of resorcinol bis-diphenyl phosphate (RDP), bisphenol-A bis- (diphenyl phosphate) (BDP), and diphenylkresyl phosphate (DPK), or is a corresponding oligomer, or is a mixture thereof. The oligomer preferably has an average degree of oligomerization of n = 3 to 6.

[0059] In a preferred embodiment 41 according to embodiments 32 to 40 or one of their preferred embodiments the flame retardant comprises resorcinol bis-diphenyl phosphate (RDP), more preferred in the form of an oligomer with an average degree of oligomerization of n = 3 to 6.

[0060] In a preferred embodiment 42 according to one of the precedent embodiments 32 to 41 or one of their preferred embodiments the phosphoric acid derivate preferably is comprised in an amount of between 1 % by weight and 25 % by weight referring to the whole composition, preferably between 2 % by weight and 12 % by weight, most preferably between 2 % by weight and 6 % by weight.

[0061] These flame retardants are especially advantageous since they are liquid at room temperature and therefor are better processable and in addition show a plasticizer effect in the composition, which is especially preferred, when the composition shall be flexible.

[0062] The composition may further comprise a catalyst, preferably selected from the group consisting of a tertiary amine and an organic metal compound or is a mixture thereof. In a preferred embodiment 43 according to any of the precedent embodiments or one of their preferred embodiments, the composition further comprises a catalyst, preferably selected from the group consisting of a tertiary amine and an organic metal compound or is a mixture thereof. The catalyst is either a single catalyst or is a mixture of several catalysts.

[0063] The catalyst preferably accelerates the reaction between the NCO groups of the isocyanates and the hydroxyl groups of the polyol and of the chain extender.

[0064] In a preferred embodiment 44 according to the preferred embodiments of embodiment 43 the metal compound is selected from the group consisting of a titanic ester, an iron compound, a tin compound, and a bismuth salt, or is a mixture thereof. A preferred iron compound is iron (III) acetylacetonate. A preferred tin compound is selected from the group consisting of tin diacetate, tin dioctoate, tin dilaurate, tin (II) neodecanoate, and dialkyl tin salts of aliphatic carboxylic acids, or a mixture thereof. Preferably the catalyst is tin dioctoate, tin (II) neodecanoate, or is a mixture thereof. A preferred titanic ester is tetrabutyl orthotitanate. In preferred bismuth salts, the bismuth is present in the oxidation states 2 or 3, in particular 3, with preference being given to salts of carboxylic acids, preferably carboxylic acids having from 6 to 14 carbon atoms, particularly preferably from 8 to 12 carbon atoms. A very preferred bismuth salt is bismuth (III) neodecanoate, bismuth 2-ethylhexanoate, or bismuth octanoate, or is a mixture thereof.

[0065] In a preferred embodiment 45 according to any of the precedent embodiments 43 to 44 or one of their preferred embodiments the catalyst is used in an amount of from 0.0001 to 0.1 part by weight per 100 parts by weight of the polyol. Preference is given to using tin catalyst, in particular tin dioctoate.

[0066] In a preferred embodiment 46 according to any of the precedent embodiments 43 to 45 or one of their preferred embodiments, the composition comprises SDO (tin (II) 2-ethylhexanoate), tin (II) neodecanoate, or a mixture thereof, preferably used in quantities of 0.35-0.4 parts by weight, referring to the whole composition being 100 parts by weight.

[0067] In preferred embodiment 47 according to one of the precedent embodiments or on of its preferred embodiments, a further auxiliary or additive is comprised in the composition. The auxiliary or additive is a single substance, or a mixture of at least two substances. In a preferred embodiment the auxiliary or additive is selected from the group consisting of a surface-active substance, a filler, a flame retardant, a nucleating agent, an oxidation stabilizer, a lubricating aid, a demolding aid, a dye, a pigment, an inorganic filler an or an organic filler, a reinforcing agent, a plasticizer, an antistatic agent, a stabilizer, preferably a stabilizer against hydrolysis, light, heat or discoloration, an inorganic filler, an organic filler, a reinforcing agent, a plasticizer, or is a mixture thereof.

[0068] A stabilizer preferably is an additive which protects a plastic or a plastic composition against harmful environmental influences. A preferred example is a primary or secondary antioxidant, a sterically hindered phenol, a hindered amine light stabilizer, an UV absorber, a phosphite, a hydrolysis inhibitor, a quencher, and a flame retardant, or is a mixture thereof. Examples of commercial stabilizers are given in Plastics Additives Handbook, 5th Edition, H. Zweifel, ed., Hanser Publishers, Munich, 2001 ([1]), p.98-136.

[0069] Preferably the UV absorber has a number average molecular weight greater than 0.3 x 103g / Mol, in particular greater than 0.39 x 103g / Mol. Furthermore, the preferred UV absorber has a molecular weight not exceeding 5 x 103g / Mol, particularly preferred not exceeding 2 x 103g / mol.

[0070] The UV absorber is preferably selected from the group consisting of cinnamates, oxanilides, benzophenones and benzotriazole, or is a mixture thereof, particularly suitable as UV absorbers is benzotriazole. Examples of particularly suitable UV-absorbers are Tinuvin® 213, Tinuvin® 234, Tinuvin® 312, Tinuvin® 571 , Tinuvin® 384 and Eversorb® 82.

[0071] Preferably the UV absorbers is added in quantities of 0.01 wt.% to 5 wt.% based on the total weight of the composition, preferably 0.1 wt.% to 2.0 wt.%, in particular 0.2 wt.% to 0.5 wt.%.

[0072] Often a UV stabilization based on an antioxidant and a UV absorber as described above is not sufficient to guarantee a good stability of the composition against the harmful influence of UV rays. In this case, in addition to the antioxidant and / or the UV absorber, or as single stabilizer, a hindered-amine light stabilizer (HALS) is added to the composition.

[0073] Examples of commercially available HALS stabilizers can be found in Plastics Additive Handbook, 5th edition, H. Zweifel, Hanser Publishers, Munich, 2001 , pp. 123-136.

[0074] Particularly preferred hindered amine light stabilizers are bis-(1 ,2,2,6,6-penta-,methylpiperidyl) sebacat (Tinuvin® 765, Ciba Spezialitatenchemie AG) and the condensation product of 1-hy- droxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid (Tinuvin® 622). In particular, the condensation product of 1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidines and succinic acid (Tinuvin® 622) is preferred, if the titanium content of the finished product is less than 150 ppm by weight, preferably less than 50 ppm by weight, in particular less than 10 ppm by weight, based on the components used.

[0075] HALS compounds are preferably used in a concentration of from 0.01 wt.% to 5 wt.%, particularly preferably from 0.1 wt.% to 1 wt.%, in particular from 0.15 wt.% to 0.3 wt.%, based on the total weight of the composition.

[0076] A particularly preferred UV stabilizer contains a mixture of a phenolic stabilizer, a benzotriazole and a HALS compound in the preferred amounts described above.

[0077] Further information on the above-mentioned auxiliaries and additives can be found in the technical literature, e.g. Plastics Additives Handbook, 5th edition, H. Zweifel, ed., Hanser Publishers, Munich, 2001.

[0078] One advantage of the belt according to the invention is that despite its very good abrasion behavior also shows good flame retardance properties. This allows to produce belts without an additional cover. That cover often comprises an elastomer with good mechanical properties and very low or no content of flame retardant. In preferred embodiment 48 according to one of the precedent embodiments or on of its preferred embodiments the belt does not have a cover based on an elastomer.

[0079] The present invention also relates to a process for preparing a belt as disclosed above, for example by extrusion. Another aspect of the invention and embodiment 49 is the production of the belt according to any of the precedent embodiments, preferably by extruding a composition as outlined above on a wire, preferably on a wire made of steel.

[0080] The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The composition of any one of embodiments 1 to 4", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The composition of any one of embodiments 1 , 2, 3 and 4". Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

[0081] 1 . Load bearing belt extruded from a composition comprising a thermoplastic polyurethan, the thermoplastic polyurethane being the reaction product of a diisocyanate, a polyol and a chain extender, wherein the composition further comprises a polyphosphonate in an amount between 0 weight-% and 25 weight-%, preferably between 5 weight-% and 20 weight-%, more preferably between 8 weight-% and 15 weight-% referring to the whole composition being 100 weight-%.

[0082] 2. Load bearing belt extruded from a composition comprising a thermoplastic polyurethan, the thermoplastic polyurethane being the reaction product of a diisocyanate, a polyol and a chain extender, wherein the composition further comprises a polyphosphonate in an amount between 0 weight-% and 25 weight-%, preferably between 5 weight-% and 20 weight-%, more preferably between 8 weight-% and 15 weight-% referring to the whole composition being 100 weight-%, and wherein the sum of the amounts of the polyphosphonate and the thermoplastic polyurethane is between 80 weight-% and 100-weight %, more preferably between 90 weight-% and 100-weight %. 3. Belt according to embodiment 1 or 2, comprising a wire, preferably a wire made of steel.

[0083] 4. Belt according to any one of embodiments 1 to 3, wherein the belt is an elevator belt.

[0084] 5. Belt according to any one of embodiments 1 to 4, wherein the polyphosphonate is comprised between 1 weight % and 25 weight-% referring to the total weight of the composition.

[0085] 6. Belt according to any one of embodiments 1 to 5, wherein the weight average molecular weight of the polyphosphonate is between 3 x 103mol and 100 x 103mol, more preferably between 20 x 103mol and 80 x 103mol, more preferably between 40 x 103mol and 70 x 103mol, more preferably between 50 x 103mol and 60 x 103mol.

[0086] 7. Belt according to any one of embodiments 1 to 6, wherein the polyphosphonate is an aromatic polyphosphonate, more preferably the polyphosphonate comprises the following structure: wherein:

[0087] R is a rest with 0 to 20 carbon atoms, more preferably between 5 and 15 carbon atoms, more preferably the rest comprises an aromatic structure, most preferably R has the following structure: more preferably the above structure is comprised in the polyphosphonate with between 20 mol-% and 100 mol-%, referring to the total amount of polycarbonate being 100 mol- %, more preferably between 40 mol-% and 100 mol-%, more preferably between 60 mol- % and 100 mol-%, more preferably between 80 mol-% and 100 mol-%, more preferably between 90 mol-% and 100 mol-%. 8. Belt according to any one of embodiments 1 to 7, wherein the extruded composition has a Shore A hardness of 80 to 100 measured according to DIN ISO 7619-1 : 2016.

[0088] 9. Belt according to any one of embodiments 1 to 8, wherein the composition comprises a further phosphorous containing additive, preferably a phosphorous containing flame retardant.

[0089] 10. Belt according to embodiment 9, wherein the flame retardant is an aromatic phosphoric acid ester.

[0090] 11 . Belt according to any one of embodiments 1 to 10, wherein phosphorous containing additive, preferably the phosphorous containing flame retardant, is liquid at 20 °C.

[0091] 12. Belt according to any one of embodiments 1 to 11 , wherein the phosphorous containing additive, preferably the phosphorous containing flame retardant, is comprised in the composition in an amount between 1 weight-% and 15 weight-%, preferably between 1 weight- % and 10 weight-%, more preferably between 3 weight-% and 8 weight-%.

[0092] 13. Belt according to any one of embodiments 1 to 12, wherein the chain extender is selected from the group consisting of ethane diol, propane diol, butane diol, hexane diol, or is a mixture thereof, more preferably the chain extender is selected from butane diol and propane diol, or is a mixture thereof, most preferably the chain extender is butane diol.

[0093] 14. Belt according to any one of embodiments 1 to 13, wherein the diisocyanate is an aromatic diisocyanate, more preferably the diisocyanate is methylene diphenyl diisocyanate (MDI).

[0094] 15. Belt according to any one of embodiments 1 to 14, wherein the polyol is a polyether diol or is a polycarbonate diol, preferably the polyether diol is a polytetrahydrofuran diol and the polycarbonate diol is based on 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, or a mixture thereof. Also preferred is polycarbonate diol based on butanediol and hexanediol, polycarbonate diol based on pentanediol and hexanediol, and polycarbonate diol based on hexanediol, or a mixture thereof. Belt according to embodiment 15, wherein the polyether has a number average molecular weight between 0.5 x 103g / mol and 2 x 103g / mol, more preferably between 0.6 x 103g / mol and 1.5 x 103g / mol, more preferably between 0.8 x 103g / mol and 1.2 x 103g / mol, most preferably more preferably 1 .0 x 103g / mol or the polycarbonate polyol has a number average molecular weight between 1.0 x 103g / mol and 5 x 103g / mol, more preferably between 1.4 x 103g / mol and 3 x 103g / mol, more preferably between 1.8 x 103g / mol and 2.2 x 103g / mol, most preferably more preferably 2.0 x 103g / mol. Load bearing belt extruded from a composition comprising a thermoplastic polyurethan, the thermoplastic polyurethane being the reaction product of a diisocyanate, a polyol and a chain extender, wherein the composition further comprises a polyphosphonate in an amount between 0 weight-% and 25 weight-%, preferably between 5 weight-% and 20 weight-%, more preferably between 8 weight-% and 15 weight-% referring to the whole composition being 100 weight-%. Belt according to any of the precedent embodiments, comprising a wire, preferably a wire made of steel. Belt according to any of the precedent embodiments, wherein the belt is an elevator belt. Belt according to any of the precedent embodiments, wherein the polyphosphonate is comprised between 1 weight % and 25 weight-% referring to the total weight of the composition. Belt according to any of the precedent embodiments, wherein the weight average molecular weight of the polyphosphonate is between 3 x 103mol and 100 x 103mol, more preferably between 20 x 103mol and 80 x 103mol, more preferably between 40 x 103mol and 70 x 103mol, more preferably between 50 x 103mol and 60 x 103mol. Belt according to any of the precedent embodiments, wherein the polyphosphonate is an aromatic polyphosphonate, more preferably the polyphosphonate comprises the following structure: wherein:

[0095] R is a rest with 0 to 20 carbon atoms, more preferably between 5 and 15 carbon atoms, more preferably the rest comprises an aromatic structure, most preferably R has the following structure: more preferably the above structure is comprised in the polyphosphonate with between 20 mol-% and 100 mol-%, referring to the total amount of polycarbonate being 100 mol- %, more preferably between 40 mol-% and 100 mol-%, more preferably between 60 mol- % and 100 mol-%, more preferably between 80 mol-% and 100 mol-%, more preferably between 90 mol-% and 100 mol-%.

[0096] 23. Belt according to any of the precedent embodiments, wherein the extruded composition has a Shore A hardness of 80 to 100 measured according to DIN ISO 7619-1 : 2016.

[0097] 24. Belt according to any of the precedent embodiments, wherein the composition comprises a further phosphorous containing additive, preferably a phosphorous containing flame retardant.

[0098] 25. Belt according to the precedent embodiment, wherein the flame retardant is an aromatic phosphoric acid ester.

[0099] 26. Belt according to any of the precedent embodiments, wherein phosphorous containing additive, preferably the phosphorous containing flame retardant, is liquid at 20 °C. Belt according to any of the precedent embodiments, wherein the phosphorous containing additive, preferably the phosphorous containing flame retardant, is comprised in the composition in an amount between 1 weight-% and 15 weight-%, preferably between 1 weight- % and 10 weight-%, more preferably between 3 weight-% and 8 weight-%. Belt according to any of the precedent embodiments, wherein the chain extender is selected from the group consisting of ethane diol, propane diol, butane diol, hexane diol, or is a mixture thereof, more preferably the chain extender is selected from butane diol and propane diol, or is a mixture thereof, most preferably the chain extender is butane diol. Belt according to any of the precedent embodiments, wherein the diisocyanate is an aromatic diisocyanate, more preferably the diisocyanate is methylene diphenyl diisocyanate (MDI). Belt according to any of the precedent embodiments, wherein the polyol is a polyether diol or is a polycarbonate diol, preferably the polyether diol is a polytetrahydrofuran diol and the polycarbonate diol is based on 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, or a mixture thereof. Also preferred is polycarbonate diol based on butanediol and hexanediol, polycarbonate diol based on pentanediol and hexanediol, and polycarbonate diol based on hexanediol, or a mixture thereof. Belt according to the precedent embodiment, wherein the polyether has a number average molecular weight between 0.5 x 103g / mol and 2 x 103g / mol, more preferably between 0.6 x 103g / mol and 1.5 x 103g / mol, more preferably between 0.8 x 103g / mol and 1 .2 x 103g / mol, most preferably more preferably 1 .0 x 103g / mol or the polycarbonate polyol has a number average molecular weight between 1.0 x 103g / mol and 5 x 103g / mol, more preferably between 1 .4 x 103g / mol and 3 x 103g / mol, more preferably between 1.8 x 103g / mol and 2.2 x 103g / mol, most preferably more preferably 2.0 x 103g / mol. Load bearing belt extruded from a composition comprising a thermoplastic polyurethan, the thermoplastic polyurethane being the reaction product of a diisocyanate, a polyol and a chain extender, wherein the composition further comprises a polyphosphonate in an amount between 0 weight-% and 25 weight-%, preferably between 5 weight-% and 20 weight-%, more preferably between 8 weight-% and 15 weight-% referring to the whole composition being 100 weight-%, and wherein the sum of the amounts of the polyphos- phonate and the thermoplastic polyurethane is between 80 weight-% and 100-weight %, more preferably between 90 weight-% and 100-weight %. wherein the composition comprises a further phosphorous containing additive, preferably a phosphorous containing flame retardant. Load bearing belt extruded from a composition comprising a thermoplastic polyurethan, the thermoplastic polyurethane being the reaction product of a diisocyanate, a polyol and a chain extender, wherein the composition further comprises a polyphosphonate in an amount between 0 weight-% and 25 weight-%, preferably between 5 weight-% and 20 weight-%, more preferably between 8 weight-% and 15 weight-% referring to the whole composition being 100 weight-%, and wherein the sum of the amounts of the polyphosphonate and the thermoplastic polyurethane is between 80 weight-% and 100-weight %, more preferably between 90 weight-% and 100-weight %. wherein the composition comprises a further phosphorous containing additive, preferably a phosphorous containing flame retardant and wherein the flame retardant is an aromatic phosphoric acid ester. Load bearing belt extruded from a composition comprising a thermoplastic polyurethan, the thermoplastic polyurethane being the reaction product of a diisocyanate, a polyol and a chain extender, wherein the composition further comprises a polyphosphonate in an amount between 0 weight-% and 25 weight-%, preferably between 5 weight-% and 20 weight-%, more preferably between 8 weight-% and 15 weight-% referring to the whole composition being 100 weight-%, and wherein the sum of the amounts of the polyphosphonate and the thermoplastic polyurethane is between 80 weight-% and 100-weight %, more preferably between 90 weight-% and 100-weight %. wherein the composition comprises a further phosphorous containing additive, preferably a phosphorous containing flame retardant, wherein phosphorous containing additive, preferably the phosphorous containing flame retardant, is liquid at 20 °C. Load bearing belt extruded from a composition comprising a thermoplastic polyurethan, the thermoplastic polyurethane being the reaction product of a diisocyanate, a polyol and a chain extender, wherein the composition further comprises a polyphosphonate in an amount between 0 weight-% and 25 weight-%, preferably between 5 weight-% and 20 weight-%, more preferably between 8 weight-% and 15 weight-% referring to the whole composition being 100 weight-%, and wherein the sum of the amounts of the polyphos- phonate and the thermoplastic polyurethane is between 80 weight-% and 100-weight %, more preferably between 90 weight-% and 100-weight %. wherein the composition comprises a further phosphorous containing additive, preferably a phosphorous containing flame retardant, wherein phosphorous containing additive, preferably the phosphorous containing flame retardant, is liquid at 20 °C, wherein the phosphorous containing additive, preferably the phosphorous containing flame retardant, is comprised in the composition in an amount between 1 weight-% and 15 weight-%, preferably between 1 weight-% and 10 weight-%, more preferably between 3 weight-% and 8 weight-%.

[0100] Examples will be used below to illustrate the invention.

[0101] Examples:

[0102] 1. Example 1 - Materials:

[0103] Elastollan 1185A10: TPU of Shore hardness 85A from BASF Polyurethanes GmbH, Elas- togranstrasse 60, 49448 Lemforde, is based on polytetrahydrofuran polyol (PTHF) with a molecular weight of 1000 g / mol, 1,4-butanediol and 4,4'-diisocyanatodicyclohexylme- thane.

[0104] Nofia HM 1100: Polyphosphonate homopolymer, CAS#: 68664-06-2, FRX Polymers (Europe), NV, Haven 507, Scheldelaan 420, 2040 Antwerpen, Belgium, Phosphorus content 10,9%, water content % (w / w) < 0,1, MVR (240°C / 1 ,2kg = 8 cm3 / 10 min).

[0105] 2. Example 2:

[0106] The following table 1 lists compositions A and B for which the individual materials used are given in terms of weight fractions (GT). The compositions were each produced with a twin-shaft extruder type ZE 40 A from KrausMaffei Berstorff GmbH, Germany, with a travel part length of 35 D divided into 10 housings. The compositions were granulated by means of a standard underwater granulation of the company Gala (UWG). 3. Example 3

[0107] For studying the mechanical properties of the compositions granulated compositions of Example 2 were extruded into films with a thickness of 1.6 mm in a single-shaft extruder, from company Arenz GmbH, in Germany with a three-zone snout with a mixing part (screw ratio 1 :3). The density, shore hardness, tensile strength, tear propagation resistance, abrasion, and elongation at break of the extruded films were measured. The results are summarized in the table below.

[0108] Table 1 :

[0109] 15

[0110] 4. Example 4

[0111] For the cone measurements the granulated composition from Example 2 were injection molded on an extruder (Arburg 520S) with a screw diameter of 30 mm into plates with a dimension of 200x150x5mm. The plates were then sawn to the size required for the test specimens for the cone measurement (100x100x5mm).

[0112] In order to evaluate the flame retardancy, a test specimen is tested horizontally at a radiation intensity of 35kW / m2 in the cone calorimeter according to ISO 5660 Part 1 and Part 2 (2002-12).

[0113] The results are summarized in Table 2. For composition B versus composition A, the total heat evolved (THE) and the peak of heat release (PHRR) have been significantly reduced.

[0114] Table 2:

[0115] Literature cited

[0116] US 6,295,799

[0117] US 6,739,433

[0118] US 6,540,060

[0119] US 4,982,829

[0120] WO 2011 / 141068A1

[0121] Plastics Additives Handbook, 5th Edition, H. Zweifel, ed., Hanser Publishers, Munich, 2001 ([1]), p.98-136

Claims

Claims1 . Load bearing belt extruded from a composition comprising a thermoplastic polyurethan, the thermoplastic polyurethane being the reaction product of a diisocyanate, a polyol and a chain extender, wherein the composition further comprises a polyphosphonate in an amount between 0 weight-% and 25 weight-%, preferably between 5 weight-% and 20 weight-%, more preferably between 8 weight-% and 15 weight-% referring to the whole composition being 100 weight-%, and wherein the sum of the amounts of the polyphosphonate and the thermoplastic polyurethane is between 80 weight-% and 100-weight %, more preferably between 90 weight-% and 100-weight %.

2. Belt according to claim 1 , comprising a wire, preferably a wire made of steel.

3. Belt according to claim 1 or 2, wherein the belt is an elevator belt.

4. Belt according to any one of claims 1 to 3, wherein the polyphosphonate is comprised between 1 weight % and 25 weight-% referring to the total weight of the composition.

5. Belt according to any one of claims 1 to 4, wherein the weight average molecular weight of the polyphosphonate is between 3 x 103mol and 100 x 103mol, more preferably between 20 x 103mol and 80 x 103mol, more preferably between 40 x 103mol and 70 x 10 3 mol, more preferably between 50 x 103mol and 60 x 103mol.

6. Belt according to any one of claims 1 to 5, wherein the polyphosphonate is an aromatic polyphosphonate, more preferably the polyphosphonate comprises the following structure:wherein:R is a rest with 0 to 20 carbon atoms, more preferably between 5 and 15 carbon atoms, more preferably the rest comprises an aromatic structure, most preferably R has the following structure:more preferably the above structure is comprised in the polyphosphonate with between 20 mol-% and 100 mol-%, referring to the total amount of polycarbonate being 100 mol- %, more preferably between 40 mol-% and 100 mol-%, more preferably between 60 mol- % and 100 mol-%, more preferably between 80 mol-% and 100 mol-%, more preferably between 90 mol-% and 100 mol-%.

7. Belt according to any one of claims 1 to 6, wherein the extruded composition has a Shore A hardness of 80 to 100 measured according to DIN ISO 7619-1: 2016.

8. Belt according to any one of claims 1 to 7, wherein the composition comprises a further phosphorous containing additive, preferably a phosphorous containing flame retardant.

9. Belt according to claim 8, wherein the flame retardant is an aromatic phosphoric acid ester.

10. Belt according to any one of claims 1 to 9, wherein phosphorous containing additive, preferably the phosphorous containing flame retardant, is liquid at 20 °C.

11. Belt according to any one of claims 1 to 10, wherein the phosphorous containing additive, preferably the phosphorous containing flame retardant, is comprised in the composition in an amount between 1 weight-% and 15 weight-%, preferably between 1 weight-% and 10 weight-%, more preferably between 3 weight-% and 8 weight-%.

12. Belt according to any one of claims 1 to 11, wherein the chain extender is selected from the group consisting of ethane diol, propane diol, butane diol, hexane diol, or is a mixture thereof, more preferably the chain extender is selected from butane diol and propane diol, or is a mixture thereof, most preferably the chain extender is butane diol.

13. Belt according to any one of claims 1 to 12, wherein the diisocyanate is an aromatic diisocyanate, more preferably the diisocyanate is methylene diphenyl diisocyanate (MDI).

14. Belt according to any one of claims 1 to 13, wherein the polyol is a polyether diol or is a polycarbonate diol, preferably the polyether diol is a polytetrahydrofuran diol and the polycarbonate diol is based on 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, or a mixture thereof. Also preferred is polycarbonate diol based on butanediol and hexanediol, polycar- bonate diol based on pentanediol and hexanediol, and polycarbonate diol based on hexanediol, or a mixture thereof.

15. Belt according to claim 14, wherein the polyether has a number average molecular weight between 0.5 x 103g / mol and 2 x 103g / mol, more preferably between 0.6 x 103g / mol and 1.5 x 103g / mol, more preferably between 0.8 x 103g / mol and 1.2 x 103g / mol, most preferably more preferably 1.0 x 103g / mol or the polycarbonate polyol has a number average molecular weight between 1.0 x 103g / mol and 5 x 103g / mol, more preferably between 1.4 x 103g / mol and 3 x 103g / mol, more preferably between 1.8 x 103g / mol and 2.2 x 103g / mol, most preferably more preferably 2.0 x 103g / mol.

Images