CARBONATE POLYOL

FIELD OF THE INVENTION

The present invention belongs to the field of thermoplasctic polyurethane, more particularly to thermoplastic polyurethanes comprising segments derived from polyether carbonate polyols, methods for their preparation, as well as their applications.

BACKGROUND

Thermoplastic polyurethane elastomers (TPUs) have been known for a long time and used in a wide array of products and applications. They are of industrial importance due to the combination of good mechanical properties with the known advantages of inexpensive, thermoplastic processability.

TPUs are generally made from the reaction of polyols (usually polyether and polyester polyols), an isocyanate compound (usually an organic diisocyanate) and a chain extender, such as a short-chain diol. The resulting TPU is then characterized for being a segmented polymer having soft segments derived from the hydroxyl terminated polyol and hard segments derived from the isocyanate compound and the chain extender.

Various types of compounds for each of these reactants are disclosed in the literature. The TPUs polymers made from these three reactants find particular use in various fields where products are made by melt processing the TPU and forming it into various shapes to produce desired articles.

Thus, polyols, and in particular, polytetramethylene oxide polyether polyols are widely used in the thermoplastic polyurethane technology to react with isocyanates and chain extenders in order to provide thermoplastic polyurethane compositions. As an alternative to polyether and polyester polyols, polycarbonate polyols have also been used in the polyurethane field to produce polyurethanes. Polycarbonates polyols are commercially available and all derived from diols (such as 1,4-butanediol, 1,6- hexane diol and the like) which react with phosgene or a reactive equivalent to produce carbonate linkages between the diol units. International patent application WO2013/138161 describes the use of polycarbonate polyols with a high content of carbonate linkages derived from the copolymerization of C0 ₂ with one or more epoxides to produce a thermoplastic polyurethane when reacting with a di- or poly- isocyanate. Said polycarbonate polyol is characterized for having two carbon atoms between the carbonate linkages. Document US 6,191,214 describes a method for preparing a water-borne polyurethane dispersion for adhesive by reaction of an organic isocyanate with polyols, among which polycarbonate polyols are cited, in the presence of chain extenders and compounds containing a diamide sulfonate group.

Polyether carbonate polyols have also been used to produce polyurethanes. There are several documents describing the preparation of polyether carbonate polyols by reactions catalized with double metal cyanide compounds.

EP 2548908 discloses the preparation of polyether carbonate polyols from alkylene oxides and carbon dioxide with a double metal cyanide (DMC) catalyst, where the DMC catalyst comprises at least one complex forming components comprising polycarbonate diol, polyethercarbonate polyol, polyethylene glycoldiol or poly(tetramethylene etherdiol). In this process, the DMC catalyst is obtained by a process in which the washing step is carried on with an aqueous solution of an organic complex and at least one of the complex forming components mentioned above.

US 2013/123532 relates to a process for the preparation of polyether carbonate polyols from alkylene oxides and carbon dioxide by means of a double metal cyanide catalyst (DMC). The presence of a certain amount of an alkaline metal hydroxide, metal carbonate and/or metal oxide in the cyanide-free metal salt, the metal cyanide salt or both the mentioned salts used for the preparation of the DMC catalyst is disclosed to improve selectivity (that is, reduce the ratio cyclic carbonate/linear polyether carbonate) and increase the catalyst activity towards C0 ₂ . In this process, the DMC catalyst is obtained by a process in which the washing step is carried on with an aqueous solution of an organic complex ligand.

EP 2441788 discloses the production of polyether carbonate polyols from alkylene oxides and carbon dioxide by means of a double metal cyanide (DMC) catalyst, where the reaction is carried out in a tubular reactor. Although these documents describe the use of said polyether carbonate polyols to obtain polyurethanes, more particularly flexible polyurethane foams, no explicit mention to their use in the formulation of thermoplastic polyurethane are disclosed.

US 2003/149323 discloses a method for the production of polyether carbonate polyols from alkylene oxides and carbon dioxide by means of a multimetal cyanide compound having a crystalline structure and a content of platelet-shaped particles of at least 30% by weight.

US 2013/0190462 relates to a process for the preparation of polyether carbonate polyols by catalytic copolymerization of carbon dioxide with alkylene oxides with the aid of double metal cyanide (DMC) catalysts and in the presence of metal salts.

In spite of the different procedures for preparing polyether carbonate polyols disclosed in the prior art, improved processes are still needed. In particular, processes that lead to polyether carbonate polyols with a high content of carbon dioxide, even under mild reaction conditions, and/or improved selectivity of the linear to cyclic product are desirable.

In fact, polyether carbonate polyol with a high content of C0 ₂ incorporated in the backbone of the polymer are of particular interest to produce polyurethane compositions, and more specifically thermoplastic polyurethane compositions, with improved properties.

BRIEF DESCRIPTION OF THE INVENTION

The authors of the present invention have developed a new thermoplastic polyurethane having segments derived from polyether carbonate polyols obtained in a particular process catalyzed with double metal cyanide catalysts. The polyether carbonate polyols used in the elaboration of the thermoplastic polyurethane are characterized for having a high content of carbonate linkages in the polymer backbone, as well as a particular distribution of said carbonate groups within the polymer structure. As derivable from the experimental part, this polyether carbonate polyol provides a thermoplastic polyurethane with improved properties when compared to polyurethanes derived from polyether polyols or from polyether carbonate polyols having been obtained by other processes. In particular, the thermoplastic polyurethane of the present invention presents an improved tensile strength, as well as a higher percentage elongation or strain.

As explained in more detail in the experimental part, the thermoplastic polyurethane of the present invention has shown an improvement in the tensile strength of up to 309% with respect to polyurethanes obtained from polyol ethers where no carbonate groups are present, in contrast to other thermoplastic polyurethanes, such as those described in document DE102012218848, which derive from polyether carbonate polyols obtained by a different process but having similar C0 ₂ and hard segment content for which only an improvement of 45% has been observed.

Thus, a first aspect of the present invention refer to a thermoplastic polyurethane composition comprising segments derived from a polyether carbonate polyol, wherein said polyether carbonate polyol is obtainable by a process comprising copolymerizing one or more H-functional initiator substances, one or more alkylene oxides and carbon dioxide in the presence of a double metal cyanide catalyst, wherein said copolymerization is performed at a temperature of 80 to 110°C and at a carbon dioxide pressure of 5 to 60 bar, and wherein the double metal cyanide catalyst is obtainable by a process comprising:

a) synthesizing a solid double metal cyanide catalyst in the presence of an organic complexing agent and a polyether polyol ligand; and

b) first washing the catalyst obtained in step a) with an aqueous solution comprising:

- 90- 100%) by weight of water; and

- 0- 10%o by weight of a polyether polyol ligand,

to form a slurry, wherein the aqueous solution does not contain any organic complexing agent other than the polyether polyol ligand; c) isolating the catalyst from the slurry obtained in step b); and

d) washing the solid catalyst obtained in step c) with a solution comprising:

- 90-100% by weight of an organic complexing agent; and

- 0-10%) by weight of a polyether polyol. Another aspect of the invention refers to a process for preparing a thermoplastic polyurethane composition, said process comprises the reaction of a polyether carbonate polyol as defined above with one or more diisocyanate compounds and a chain extender. The invention also refers to the thermoplastic polyurethane composition obtainable by reacting a polyether carbonate polyol as defined above with one or more diisocyanate compounds and a chain extender.

Additional aspects of the present invention refer to an injection molding composition or an article of manufacture comprising the thermoplastic polyurethane composition as mentioned above.

DETAILED DESCRIPTION OF THE INVENTION

As mentioned before, a first aspect of the present invention refers to a thermoplastic polyurethane comprising segments derived from a polyether carbonate polyol, wherein said polyether carbonate polyol is obtainable by a process comprising copolymerizing one or more H-functional initiator substances, one or more alkylene oxides and carbon dioxide in the presence of a double metal cyanide catalyst, wherein said copolymerization is performed at a temperature of 80 to 110°C and at a carbon dioxide pressure of 5 to 60 bar, and wherein the double metal cyanide catalyst is obtainable by a process comprising:

a) synthesizing a solid double metal cyanide catalyst in the presence of an organic complexing agent and a polyether polyol ligand; and

b) first washing the catalyst obtained in step a) with an aqueous solution comprising:

- 90- 100% by weight of water; and

- 0- 10% by weight of a polyether polyol ligand,

to form a slurry, wherein the aqueous solution does not contain any organic complexing agent other than the polyether polyol ligand; c) isolating the catalyst from the slurry obtained in step b); and

d) washing the solid catalyst obtained in step c) with a solution comprising:

- 90-100% by weight of an organic complexing agent; and - 0-10% by weight of a polyether polyol.

This process provides polyether carbonate polyols with a higher content of incorporated carbon dioxide, i.e. more percentage of carbonate linkages, than other related processes of the prior art, even when milder reaction conditions are used, as well as with a different distribution of said carbonate groups within the polymer structure. This polyether carbonate polyol provides a thermoplastic polyurethane composition with improved properties when compared to polyurethanes derived from polyether polyols or from polyether carbonate polyols having been obtained by other proceeses as derivable from the examples provided in this specification. DMC catalyst

The DMC catalyst used in the process as described above can be obtained by a process comprising: a) synthesizing a solid double metal cyanide catalyst in the presence of an organic complexing agent and a polyether polyol ligand; and

b) first washing the catalyst obtained in step a) with an aqueous solution comprising:

- 90- 100% by weight of water; and

- 0- 10%) by weight of a polyether polyol ligand,

to form a slurry, wherein the aqueous solution does not contain any organic complexing agent other than the polyether polyol ligand. c) isolating the catalyst from the slurry obtained in step b); and

d) washing the solid catalyst obtained in step c) with a solution comprising:

- 90-100% by weight of an organic complexing agent, and

- 0- 10%) by weight of a polyether polyol ligand.

Step a) This step can be performed by any method known in the prior art for the synthesis of a DMC catalyst. In a particular embodiment, this step can be carried out by reacting, in an aqueous solution, a water-soluble metal salt (in excess) and a water-soluble metal cyanide salt in the presence of a polyether polyol ligand and an organic complexing agent. In a preferred embodiment, aqueous solutions of a water-soluble metal salt and a water- soluble metal cyanide salt are first reacted in the presence of the organic complexing agent using efficient mixing to produce a catalyst slurry. The metal salt is used in excess; preferably the molar ratio of metal salt to metal cyanide salt is between 2: 1 and 50: 1, more preferably between 10: 1 and 40: 1. This catalyst slurry contains the reaction product of the metal salt and the metal cyanide salt, which is a double metal cyanide compound. Also present are excess metal salt, water, and organic complexing agent, all of which are incorporated to some extent in the catalyst structure. In another preferred embodiment, the mixture of the aqueous solution containing the water-soluble metal salt and the aqueous solution containing the water-soluble metal cyanide salt takes place at a temperature ranging from 30 to 70°C, more preferably from 40 to 60°C, even more preferably at about 50°C.

The water-soluble metal salt preferably has the general formula MA _n wherein:

M is a cation selected form the group consisting of Zn(II), Fe(II), Ni(II), Mn(II), Co(II), Sn(II), Pb(II), Fe(III), Mo(IV), Mo(VI), Al(III), V(V), V(IV), Sr(II), W(IV),

W(VI), Cu(II) and Cr(III). Preferably, M is a cation selected from Zn(II), Fe(II), Ni(II), Mn(II) and Co(II);

A is an anion selected from the group consisting of halide, hydroxide, sulfate, carbonate, vanadate, cyanide, oxalate, thiocyanate, isocyanate, isothiocyanate, carboxylate and nitrate. Preferably, A is a cation selected from halide; and n is 1, 2 or 3 and satisfies the valency state of M.

Examples of suitable metal salts include, but are not limited to, zinc chloride, zinc bromide, zinc acetate, zinc acetonylacetonate, zinc benzoate, zinc nitrate, iron(II) sulfate, iron(II) bromide, cobalt(II) chloride, cobalt(II) thiocyanate, nickel(II) formate, nickel(II) nitrate and the like and mixtures thereof. In a particular embodiment, the water-soluble metal salt is zinc chloride.

The water-soluble metal cyanide salts preferably have the formula D _x [E _y (CN)6] , wherein:

D is an alkali metal ion or alkaline earth metal ion; E is a cation selected from the group consisting of Co(II), Co(III), Fe(II), Fe(III), Mn(II), Mn(III), Cr(II), Cr(III), Ni(II), Ir(III), Rh(III), Ru(II), V(IV) and V(V). Preferably, E is selected from Co(II), Fe(II), Ni(II), Co(III) and Fe(III); and x and y are integers greater than or equal to 1 , the sum of the charges of x and y balances the charge of the cyanide (CN) group.

Suitable water-soluble metal cyanide salts include, but are not limited to, potassium hexacyanocobaltate (III), potassium hexacyano ferrate (II), potassium hexacyanoferrate (III), calcium hexacyanocobaltate (III), lithium hexacyanocobaltate (III), and the like. In a particular embodiment, the metal cyanide salt is potassium hexacyanocobaltate (III). The organic complexing agent can be included with either or both of the aqueous salt solutions, or it can be added to the catalyst slurry immediately following precipitation of the DMC compound. It is generally preferred to pre-mix the organic complexing agent with either aqueous solution before combining the reactants. Usually, an excess amount of the complexing agent is used. Typically, the molar ratio of complexing agent to metal cyanide salt is between 10: 1 and 100: 1 , preferably between 10: 1 and 50: 1 , more preferably between 20: 1 and 40: 1.

Generally, the complexing agent must be relatively soluble in water. Suitable organic complexing agents are those commonly known in the art, for example in US 5, 158,922. Preferred organic complexing agents are water-soluble heteroatom-containing organic compounds that can complex with the double metal cyanide compound. According to the present invention, the organic complexing agent is not a polyether polyol. More preferably, the organic complexing agents are water-soluble heteroatom-containing compounds selected from monoalcohols, aldehydes, ketones, ethers, esters, amides, ureas, nitriles, sulfides and mixtures thereof. Preferred organic complexing agents are water-soluble aliphatic alcohols, preferably Ci-C ₆ aliphatic alcohols, selected from the group consisting of ethanol, isopropyl alcohol, /? -butyl alcohol, z ^' so-butyl alcohol, sec- butyl alcohol and tert-butyl alcohol. 7¾rt-butyl alcohol (TBA) is particularly preferred.

Preferably, the aqueous metal salt and metal cyanide salt solutions (or their DMC reaction product) are efficiently mixed with the organic complexing agent. A stirrer can be conveniently used to achieve efficient mixing. Examples of double metal cyanide compounds resulting from this reaction include, for example, zinc hexacyanocobaltate (III), zinc hexacyano ferrate (III), nickel hexacyanoferrate (II), cobalt hexacyanocobaltate (III) and the like. Zinc hexacyanocobaltate (III) is preferred. The catalyst slurry produced after the mixing of the aqueous solutions in the presence of the organic complexing agent is then combined with a polyether polyol ligand. This step is preferably performed using a stirrer so that an efficient mixture of the catalyst slurry and the polyether polyol takes place.

This mixture is preferably performed at a temperature ranging from 30 to 70°C, more preferably from 40 to 60°C, even more preferably at about 50°C.

Suitable polyether polyols include those produced by ring-opening polymerization of cyclic ethers, and include epoxide polymers, oxetane polymers, tetrahydrofuran polymers and the like. Any method of catalysis can be used to make the polyethers. The polyethers can have any desired end groups, including, for example, hydroxyl, amine, ester, ether or the like. Preferred polyethers are polyether polyols having average hydroxyl functionalities from about 2 to about 8, more preferably the average hydroxyl functionality is 2. Also preferred are polyether polyols having a number average molecular weight lower than 2000, more preferably between 200 and 1000, even more preferably between 300 and 800. These are usually made by polymerizing epoxides in the presence of active hydrogen-containing initiators and basic, acidic or organometallic catalysts (including DMC catalysts).

Useful polyether polyols include poly(oxypropylene) polyols, ethylene oxide-capped poly(oxypropylene) polyols, mixed ethylene oxide-propylene oxide polyols, butylenes oxide polymers, butylenes oxide copolymers with ethylene oxide and/or propylene oxide, polytetra methylene ether glycols and the like. Most preferred are poly(oxypropylene) polyols, particularly diols and triols, and more preferably diols, having number average molecular weights lower than 2000, more preferably between 200 and 1000, even more preferably between 300 and 800.

More preferably, the polyether polyol used in the preparation of the DMC catalyst has been synthesized by acidic catalysis, i.e. by polymerizing an epoxide in the presence of active hydrogen-containing initiator and acidic catalysts. Examples of suitable acidic catalysts include Lewis acids such as BF ₃ , SbF ₅ , Y(CF ₃ S0 ₃ ) ₃ , or Bronsted acids such as CF ₃ S0 ₃ H, HBF ₄ , HPF ₆ , HSbF ₆ .

In a particular embodiment, the polyether polyol ligand is a poly(oxypropylene) polyol, more preferably is a poly(oxypropylene) diol with a number average molecular weight between 200 and 1000, preferably between 300 and 800, obtained by basic catalysis.

In another embodiment, the polyether polyol ligand is a poly(oxypropylene) polyol, more preferably is a poly(oxypropylene) diol with a number average molecular weight between 200 and 1000, preferably between 300 and 800, obtained by acidic catalysis.

Using a polyether diol obtained by acidic catalysis in the preparation of the DMC catalyst is preferred.

Once the polyether polyol has been combined with the double metal cyanide compound, a polyether polyol- containing solid catalyst is isolated from the catalyst slurry. This is accomplished by any convenient means, such as filtration, centrifugation or the like.

In a particular embodiment, enough reactants are used to give a solid DMC catalyst that contains:

- 30-80% by weight of the double metal cyanide compound;

- 1-10% by weight of water;

- 1-30%) by weight of the organic complexing agent; and

- l-30%o by weight of the polyether polyol ligand. Preferably, the total amount of the organic complexing agent and the polyether polyol is from 5% to 60% by weight with respect to the total weight of the catalyst, more preferably from 10% to 50% by weight, even more preferably from 15% to 40% by weight.

Step b)

The isolated polyether polyol-containing solid catalyst is then first washed with an aqueous solution comprising 90-100%) by weight of water and 0-10% by weight of a polyether polyol. This aqueous solution is absent of any organic complexing agent as those mentioned above. No other washing step is performed before this first washing step once the isolated solid DMC catalyst has been obtained in step a). The polyether polyol used in step b) is as defined above for step a). Percentages by weight of the components in the aqueous solution are based on the total weight of said aqueous solution.

It has been surprisingly found that the particular composition of the aqueous solution used in this washing step leads to a double metal cyanide catalyst that provides an improved process for preparing polyether carbonate polyols. As shown in the examples of the present invention, the content of incorporated carbon dioxide is higher than that obtained with a DMC catalyst obtained by washing with an aqueous solution comprising an organic complexing agent (such as tert-butyl alcohol) and a polyether polyol (comparative Examples 5-6). Preferably, the amount of polyether polyol ligand in the aqueous solution in step b) is lower than 5% by weight with respect to the total weight of the aqueous solution. According to a further particular embodiment the amount of polyether polyol ligand in the aqueous solution in step b) is lower than 4% by weight with respect to the total weight of solution, preferably lower than 3%. According to a further embodiment, the amount of polyether polyol ligand in the aqueous solution in step b) is between 0.05% and 10% by weight with respect to the total weight of solution, preferably between 0.1% and 2%, more preferably between 0.3% and 1.8%. In a further particular embodiment, the amount of polyether polyol ligand in the aqueous solution in step b) is 0%) by weight. In step b) the water and the polyether polyol ligand can be brought into contact with the catalyst obtained in step a) simultaneously or consecutively. That is, the aqueous solution in step b) can already contain both the water and the polyether polyol ligand when brought into contact with the catalyst obtained in step a) ("simultaneous bringing into contact") or the catalyst obtained in step a) can be first brought into contact with one of the individual components (the water or the polyether polyol ligand) and the resulting mixture then brought into contact with the other individual component ("consecutive bringing into contact"). In a particular embodiment, the water and the polyether polyol ligand are brought into contact with the catalyst obtained in step a) consecutively. In a preferred embodiment, the catalyst obtained in step a) is first brought into contact with water and then brought into contact with the polyether polyol ligand which is preferably in a 0.1 to 5%, more preferably in 0.1 to 3%, by weight with respect to the total weight of the aqueous solution.

This washing step is generally accomplished by reslurrying the catalyst in the aqueous solution followed by a catalyst isolation step using any convenient means, such as filtration.

It has also been particularly advantageous to use this aqueous solution in the washing step b) in combination with an excess amount of the organic complexing agent in step a) and/or d).

Step d) Although a single washing step suffices, the process for preparing the DMC catalyst described in the present invention also includes the washing of the catalyst more than once. The subsequent wash is non-aqueous and includes the reslurry of the double metal cyanide catalyst in an organic complexing agent or in a mixture of the organic complexing agent and the poly ether polyol used in the previous washing step. Thus, the double metal cyanide catalyst is washed with a solution comprising 90-100% by weight of the organic complexing agent and 0-10% by weight of the polyether polyol.

The polyether polyol used in step d) is as defined above for step a).

Percentages by weight of the components in the solution are based on the total weight of said solution. Preferably, the amount of polyether polyol in the solution in step d) is lower than 5% by weight with respect to the total weight of solution. According to a further particular embodiment the amount of polyether polyol ligand is lower than 4% by weight with respect to the total weight of solution, preferably lower than 3%. According to a further embodiment, the amount of polyether polyol in step d) is between 0.05%> and 5% by weight with respect to the total weight of solution, preferably between 0.1 % and 2%, more preferably between 0.3% and 1.8%.

The organic complexing agent is preferably tert-butyl alcohol. The polyether polyol is preferably a poly(oxypropylene)polyol, more preferably a poly(oxypropylene)polyol having a molecular weight lower than 2000 Da, more preferably from 200 to 1000 Da or from 300 to 800 Da, and/or which has been synthesized by acidic catalysis. Typically, the molar ratio of complexing agent to metal cyanide salt is between 10: 1 and 200: 1, preferably between 20: 1 and 150: 1, more preferably between 50: 1 and 150: 1.

In step d) the organic complexing agent and the polyether polyol can be brought into contact with the solid catalyst obtained in step c) simultaneously or consecutively. In a particular embodiment, they are brought into contact with the solid catalyst obtained in step c) consecutively. Preferably, the catalyst obtained in step c) is first brought into contact with the organic complexing agent and then brought into contact with the polyether polyol.

After the catalyst has been washed, it is usually preferred to dry it under vacuum until the catalyst reaches a constant weight. The catalyst can be dried at temperatures within the range of about 50°C to 120°C, more preferably from 60°C to 110°C, even more preferably from 90°C to 1 10°C. The dry catalyst can be crushed to yield a highly active catalyst in powder form appropriate for use in the co-polymerization process of the invention. In a particular embodiment, the double metal cyanide compound is zinc hexacyanocobaltate (III), the organic complexing agent is tert-butyl alcohol and the polyether polyol is a poly(oxypropylene) polyol. Preferably the polyether polyol is a poly(oxypropylene)polyol, more preferably a poly(oxypropylene)polyol having a molecular weight lower than 2000 Da, more preferably from 200 to 1000 Da or from 300 to 800 Da, and/or which has been synthesized by acidic catalysis.

The washing steps used in the process to prepare the DMC catalyst cannot be considered as simple steps where the catalyst is washed to remove impurities or reactants. Actually, these washing steps provide the DMC with a modified structure by incorporating therein polyether polyol ligands and the organic complexing agent. Thus, in a particular embodiment, the catalyst obtainable by the above process is also characterized by comprising:

- at least one double metal cyanide compound;

- at least one organic complexing agent; and

- at least one polyether polyol ligand having a molecular weight lower than 2000 Da. In a particular embodiment, the double metal cyanide compound is zinc hexacyanocobaltate (III), the organic complexing agent is tert-butyl alcohol and the polyether polyol has a molecular weight lower than 2000 Da. Most preferred the polyether polyol is a poly(oxypropylene) polyol, particularly a diol or triol having number average molecular weight between 200 and 1000 Da, more preferably between 300 and 800 Da.

In a particular embodiment, the organic complexing agent is tert-butyl alcohol and the polyether polyol has been synthesized by acidic catalysis. Preferably, the organic complexing agent is tert-butyl alcohol and the polyether polyol has a molecular weight lower than 2000 Da, preferably between 200 and 1000, more preferably between 300 and 800 Da, and has been synthesized by acidic catalysis.

In another embodiment, the organic complexing agent is tert-butyl alcohol and the polyether polyol has been synthesized by basic catalysis. Preferably, the organic complexing agent is tert-butyl alcohol and the polyether polyol has a molecular weight lower than 2000 Da, preferably between 200 and 1000, more preferably between 300 and 800 Da, and has been synthesized by basic catalysis.

In a particular embodiment, the double metal cyanide catalyst obtainable by the above process comprises:

- 30-80% by weight of the double metal cyanide compound;

- 1 - 10% by weight of water;

- 1-30% by weight of the organic complexing agent; and

- 1-30%) by weight of the polyether polyol ligand.

Preferably, the total amount of the organic complexing agent and the polyether polyol is from 5% to 60% by weight with respect to the total weight of the catalyst, more preferably from 10% to 50% by weight, even more preferably from 15% to 40% by weight.

In a particular embodiment, the DMC catalyst used in the process for obtaining the polyether carbonate polyol has been prepared according to the process as defined above.

Polyether carbonate polyol synthesis The DMC catalyst obtainable by the above process is particularly useful for the preparation of the polyether carbonate polyols from which the segments comprised in the thermoplastic polyurethane composition of the invention derive.

The process for the preparation of polyether carbonate polyols comprises copolymerizing one or more H-functional initiator substances, one or more alkylene oxides and carbon dioxide in the presence of a double metal cyanide catalyst obtainable as defined above, wherein said copolymerization is performed at a temperature of 80 to 110°C and at a carbon dioxide pressure of 5 to 60 bar.

Typically, alkylene oxides having from 2 to 24 carbon atoms can be used. Examples of said alkylene oxides include, among others, one or more compounds selected from the group consisting of optionally substituted ethylene oxide, propylene oxide, butene oxides, pentene oxides, hexene oxides, heptene oxides, octene oxides, nonene oxides, decene oxide, undecene oxides, dodecene oxides, cyclopentene oxide, cyclohexane oxide, cycloheptene oxide, cyclooctene oxide and styrene oxide. Substituted alkylene oxides preferably refer to alkylene oxides substituted with a Ci-C ₆ alkyl group, preferably methyl or ethyl. Preferred alkylene oxides are ethylene oxide, propylene oxide, butene oxide, styrene oxide and mixtures thereof. In a particular embodiment, the alkylene oxide is propylene oxide.

The term "H-functional initiator substance" refers to a compound having H atoms active for the alkoxylation, such as, for example, alcohols, primary or secondary amines, or carboxylic acids. Suitable H-functional initiator substances include those having a functionality of 2, i.e. those having two H atoms active per molecule. Examples of these compounds include dihydric alcohols, divalent amines, divalent thiols, aminoalcohols, dithioalcohols, dihydroxy esters, polyether diols, polyester diols, polyester ether diols, polyether carbonate diols, polycarbonate diols, polycarbonates, polyethyleneimines, polyether amines, polytetrahydrofurans, polytetrahydrofuranamines, polyether dithiols, polyacrylate diols, castor oil, the di-glyceride of ricinoleic acid, glycerides of fatty acids, chemically modified di-glycerides of fatty acids, and Ci-C ₂ 4-alkyl fatty acid esters that contain on average 2 hydroxyl groups per molecule. In a particular embodiment, the H-functional initiator substance is a polyether diol, optionally slightly branched, preferably having a number average molecular weight from 100 to 4000 Da.

Suitable polyether diols include poly(oxypropylene) diols, ethylene oxide-capped poly(oxypropylene) diols, mixed ethylene oxide-propylene oxide diols, butylenes oxide polymers, butylenes oxide copolymers with ethylene oxide and/or propylene oxide, polytetra methylene ether glycols and the like. Most preferred are poly(oxypropylene) diols, having number average molecular weights lower than 2000 Da, more preferably between 200 and 1000 Da, even more preferably between 300 and 800 Da.

More preferably, the polyether diol used as the H-functional initiator substance has been synthesized by acidic catalysis, i.e. by polymerizing an epoxide in the presence of active hydrogen-containing initiator and acidic catalysts. Examples of suitable acidic catalysts include Lewis acids such as BF ₃ , SbF ₅ , Y(CF ₃ S0 ₃ ) ₃ , or Bronsted acids such as CF ₃ S0 ₃ H, HBF ₄ , HPF ₆ , HSbF ₍ , In a particular embodiment, the H-functional initiator substance is a polyether diol that has been synthesized by acidic catalysis and has a number average molecular weight lower than 2000 Da, preferably between 200 and 1000 Da and more preferably between 300 and 800 Da.

The use of a polyether diol as H-functional initiator substance provides a polyether carbonate diol.

In an embodiment, the H-functional initiator substance is the same polyether polyol as the one used in the synthesis of the DMC catalyst.

The process for the preparation of polyether carbonate polyols used in the composition of the invention can be carried out continuously, semi-batch-wise or discontinuously. In a particular embodiment, at least one activation step of the DMC catalyst is performed before the copolymerization reaction. Preferably, one, two, three, four or five activation steps are performed, more preferably two, three or four activation steps.

Activation of the catalyst is achieved when a temperature peak ("hotspot") and/or pressure drop in the reactor occurs. For the activation of the DMC catalyst, preferably a partial amount of alkylene oxide (based on the total amount of alkylene oxide used in the process) is added to a mixture comprising the DMC catalyst and the H-functional initiator substance(s) in the absence or in the presence of carbon dioxide. In an embodiment, at least the first activation step is performed in the absence of carbon dioxide.

In an embodiment, the last activation step is performed in the presence of carbon dioxide. In a particular embodiment, all the activation steps are performed in the presence of carbon dioxide. In another embodiment, only the last activation step is performed in the presence of carbon dioxide.

In an embodiment of the present invention, two, three or four activation steps are performed before the copolymerization reaction by adding a partial amount of the alkylene oxide(s) to a mixture comprising the DMC catalyst and the H-functional initiator substance(s) and at least the first activation step is performed in the absence of carbon dioxide.

In another embodiment, two, three or four activation steps as defined above are performed and only the last activation step is performed in the presence of carbon dioxide. In an embodiment, two activation steps are performed, the first one in the absence of carbon dioxide and the second one in the presence of carbon dioxide. In another embodiment, three activation steps are performed, the two first ones in the absence of carbon dioxide and the third one in the presence of carbon dioxide. In another embodiment, four activation steps are performed, the three first ones in the absence of carbon dioxide and the fourth one in the presence of carbon dioxide.

In another embodiment, two, three or four activation steps as defined above are performed and all the activation steps are performed in the presence of carbon dioxide.

In an embodiment, three activation steps are performed, the first one in the absence of carbon dioxide and the second and third one in the presence of carbon dioxide. In another embodiment, four activation steps are performed, the first one in the absence of carbon dioxide and the three last ones in the presence of carbon dioxide. In a particular embodiment, the process for the preparation of polyether carbonate polyols comprises the following steps:

(i) the one or more H-functional initiator substances is placed in a vessel and heating and/or vacuum is applied ("drying"), preferably with N ₂ stripping, wherein the DMC catalyst is added to the one or more H-functional initiator substances before or after the drying;

In a particular embodiment, the DMC catalyst is added to the one or more H- functional initiator substances after the drying. Preferably, the one or more H- functional initiator substances is placed in a vessel and heating and vacuum are applied with N ₂ stripping (drying), and the DMC catalyst is added to the one or more H-functional initiator substances after the drying.

Preferably, the temperature in step (i) is brought to from 50 to 200°C, more preferably from 80 to 160°C, even more preferably from 110 to 150°C and/or the pressure is reduced to less than 500 mbar, preferably from 5 to 100 mbar.

In an embodiment, the H-functional initiator substance is subjected to a temperature from 110 to 150°C and to a pressure from 5 to 100 mbar and the DMC catalyst is then added to said H-functional initiator substance. In another embodiment, the DMC catalyst is added to the H-functional initiator substance and the resulting mixture is subjected to a temperature from 110 to 150°C and to a pressure from 5 to 100 mbar.

(ii) for activation

(ii-1) in a first activation step, a first partial amount of alkylene oxide (based on the total amount of alkylene oxide used in the process of the invention) is added to the mixture resulting from step (i), in the presence of C0 ₂ or preferably in the absence of C0 ₂ ,

(ii-2) in a second activation step, after the activation in the preceding step has been observed, a second partial amount of alkylene oxide (based on the total amount of alkylene oxide used in the process of the invention) is added to the mixture resulting from the preceding step, in the presence or in the absence of C0 ₂ , (ii-3) optionally in a third activation step, after the activation in the preceding step has been observed, a third partial amount of alkylene oxide (based on the total amount of alkylene oxide used in the process of the invention) is added to the mixture resulting from the preceding step, in the presence or in the absence of C0 ₂ , (ii-4) optionally in a further activation step, after the activation in the preceding step has been observed, a fourth partial amount of alkylene oxide (based on the total amount of alkylene oxide used in the process of the invention) is added to the mixture resulting from the preceding step in the presence of C0 ₂ ;

(iii) the rest of alkylene oxide and carbon dioxide are metered continuously into the mixture from step (ii) ("copolimerization"). The alkylene oxide used for the copolymerisation can be the same as or different from the alkylene oxide used in the activation or it can be a mixture of two or more alkylene oxides. In a particular embodiment, the alkylene oxide used for the copolymerisation is the same as the alkylene oxide used in the activation. The addition of alkylene oxide and of the carbon dioxide can take place simultaneously or sequentially, it being possible for the entire amount of carbon dioxide to be added at once or in a metered manner over the reaction time. A metered addition of the carbon dioxide is preferred.

In a preferred embodiment, the partial amount of alkylene oxide used in the activation steps is in each step from 1.0 to 15.0 wt. %, preferably from 2.0 to 13.0 wt. %, particularly preferably from 2.5 to 10.0 wt. % based on the total amount of alkylene oxide used in the process of the invention. In another embodiment, the partial amount of alkylene oxide used in the activation steps is in each step from 1.0 to 15.0 wt. %, preferably from 2.0 to 15.0 wt. %, particularly preferably from 5.0 to 15.0 wt. % based on the amount of initiator present in the vessel when said partial amount of alkylene oxide is added.

Preferably, the activation steps are performed at a temperature of from 100 to 200 °C, more preferably from 110 to 150°C. In an embodiment, the carbon dioxide pressure is between 10 to 50 bar, more preferably from 25 to 50 bar, even more preferably is 50 bar. In a particular embodiment, the DMC catalyst is used in the process for obtaining the polyether carbonate polyol in an amount of from 30 to 1000 ppm, preferably from 50 to 500 ppm, more preferably from 100 to 300 ppm, with respect to the total weight of the final polyether carbonate polyol. In a particular embodiment, the DMC catalyst has been prepared by a process as defined herein. Therefore, in an embodiment the process for obtaining the polyether carbonate polyol comprises preparing a DMC catalyst as defined herein and bringing it into contact with one or more H-functional initiator substances, one or more alkylene oxides and carbon dioxide as defined herein. The polyether carbonate polyols obtained according to this process have a functionality of two. This functionality coincides with the functionality of the H-functional starter substance used to prepare it.

In a particular embodiment, the number average molecular weight of the polyether carbonate polyol obtained according to said process ranges from 500 to 20000 Da, preferably from 1000 to 12000 Da, more preferably from 1000 to 5000.

Preferably, the polyether carbonate polyol obtained according to this process has from 1 to 50 wt%, from 5 to 50 wt%, from 1 to 40 wt% or from 5 to 40 wt%, of carbon dioxide. More preferably from 5 to 30 wt%, still more preferably from 5 to 25 wt%, even more preferably from 12 to 25 wt%, and particularly preferable from 12 to 16 wt%, based on the total weight of the final polyether carbonate polyol.

In another particular embodiment, the polyether carbonate polyol obtained according to this process has from 1 to 50 wt%, from 5 to 50 wt%, from 1 to 40 wt% or from 5 to 40 wt%, of carbon dioxide. More preferably from 5 to 35 wt%, still more preferably from 10 to 35 wt%, even more preferably from 19 to 25 wt%, based on the total weight of the polyether carbonate polyol excluding the initiator and the alkylene oxide activation.

The use of the above mentioned DMC catalyst in the co-polymerization of alkylene oxides and carbon dioxide allows the preparation of polyether carbonate polyols with a high content of incorporated carbon dioxide, i.e. a high content of carbonate linkages in the backbone of the polymer, as well as with a particular distribution of said carbonate groups within the polymer structure. The poly ether carbonate polyol from which the segments comprised in the composition of the invention derive has a functionality of two, typically two hydroxyl groups per molecule.

However, other reactive-end groups may be present if the polyols are treated to modify the chemistry of the end groups. Such modified materials may terminate in amino, thiol, alkene, carboxylate, isocyanate groups and the like.

As thermoplastic polyurethanes allow for the production of polyurethane by conventional thermoplastic techniques, they must not thermally degrade when repeatedly plasticized by the influence of temperature. Therefore, the thermoplastic polyurethane macromolecules are typically largely linear and not branched macromolecules since the latter cannot be easily thermoformed. Actually, bifuctional polyols are typically used to make the thermoplastic polyurethanes.

Thus, the polyether carbonate polyol from which the segments comprised in the composition of the invention derive is a polyether carbonate diol. In a preferred embodiment, the polyether carbonate polyol from which the segments comprised in the composition of the invention derive has from 5 to 25 wt% of carbon dioxide, more preferably from 12 to 25 wt%, even more preferably from 12 to 16 wt% of carbon dioxide, based on the total weight of the polyether carbonate polyol.

In another particular embodiment, the polyether carbonate polyol from which the segments comprised in the composition of the invention derive has from 5 to 35 wt% of carbon dioxide, more preferably from 10 to 35 wt%, even more preferably from 19 to 25 wt%, based on the total weight of the polyether carbonate polyol excluding the initiator and the alkylene oxide activation.

In another particular embodiment, the thermoplastic polyurethane of the invention has a Tg from -10°C to -20°C.

Process for preparing the thermoplastic polyurethane composition

The thermoplastic polyurethane composition of the present invention can be obtained by reacting a polyether carbonate polyol as defined herein above with one or more di- isocyanates and with a chain extender. This process can be carried out continuously or batchwise. During the process, all components can be added either simultaneously or in any sequence.

The polyurethane producing reaction can be carried out in the absence of a reaction medium, or in the presence of a solvent non-reactive to the isocyanates. When no reaction medium is used, the polymerization reaction can be carried out (a) by mixing the polyether carbonate polyol with a chain extender, and further mixing the resultant mixture with a diisocyanate compound to cause all the mixed components to be reacted with each other; (b) by reacting the polyether carbonate polyol with the diisocyanate compound to produce a prepolymer having isocyanate end groups, mixing the prepolymer-containing mixture with the chain extender to allow the prepolymer to react with the chain extender; or (c) by mixing the polyether carbonate polyol with the chain extender, further mixing a portion of the necessary amount of the diisocyanate compound to allow the mixed portion of the diisocyanate compound to react with the polyether carbonate polyol and the chain extender and to produce a prepolymer having hydroxyl groups, still further mixing a remaining portion of the diisocyanate compound into the prepolymer-containing mixture to allow the mixed portion of the diisocyanate compound to react with the prepolymer.

The polymerization reaction in the absence of the reaction medium is preferably carried out at a reaction temperature ranging from 80 to 250°C. When the procedure (b) or (c) is carried out, the resultant prepolymer has a low molecular weight and must be further polymerized to increase its molecular weight.

When the reaction medium is used (solvent non-reactive to the isocyanates), the polymerization reaction can be carried out (a) by dissolving the polyether carbonate polyol in the solvent, mixing the resultant solution with a chain extender and then with a diisocyanate compound, and subjecting the resultant reaction mixture to the polymerization reaction; (b) by dissolving the polyether carbonate polyol in the solvent, mixing the resultant solution with the diisocyanate compound to allow the diisocyanate compound to react with the polyether carbonate polyol and to prepare a prepolymer having isocyanate end groups, and further mixing the prepolymer-containing mixture with the chain extender to allow the chain extender to react with the prepolymer; or (c) by dissolving the polyether carbonate polyol in the solvent, mixing the resultant solution with the chain extender and a portion of the necessary amount of the diisocyanate compound to allow the mixed chain extender and the diisocyanate compound to react with the polyether carbonate polyol and to prepare a prepolymer having hydroxyl groups, and further mixing the prepolymer-containing mixture with a remaining portion of the diisocyanate compound, to allow the diisocyanate compound to react with the prepolymer.

The polymerization reaction in the presence of the reaction medium is preferably carried out at a reaction temperature of 20 to 200°C. The solvent for the reaction medium preferably comprises at least one selected from the group consisting of dichloromethane, chloroform, 1 ,2-dichloroethane, tetrahydrofurane, methylene ketone, ethyl acetate, toluene, dioxane, dimethylformamide, dimethylacetamide and dimethy lsulfo xide .

In a preferred embodiment, the polymerization reaction is carried out in the presence of a reaction medium and is conducted by process (b) mentioned above, i.e., by first by dissolving the polyether carbonate polyol in the solvent, mixing the resultant solution with the diisocyanate compound to allow the diisocyanate compound to react with the polyether carbonate polyol and to prepare a prepolymer having isocyanate end groups, and further mixing the prepolymer-containing mixture with the chain extender to allow the chain extender to react with the prepolymer. The polyurethane components can be mixed in a batch, mixed and dispersed continuously, or mixed continuously in an extruder.

A large number of diisocyanates are known in the art which can be used in the process for obtaining the thermoplastic polyurethane.

In a particular embodiment, the diisocyanate is an aliphatic or cycloaliphatic diisocyanate or a derivative thereof or an oligomer of an aliphatic or cycloaliphatic diisocyanate. In another particular embodiment, the diisocyanate is an aromatic diisocyanate or a derivative thereof or an oligomer of an aromatic diisocyanate. In another particular embodiment, the diisocyanate compound may comprise mixtures of any two or more of the above type of diisocyanates. Suitable aliphatic and cycloaliphatic diisocyanate compounds include, for example, 1,3- trimethylene diisocyanate; 1 ,4-tetramethylene diisocyanate; 1,6-hexamethylene diisocyanate; 2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylene diisocyanate; 1 ,9-nonamethylene diisocyanate; 1 , 10-decamethylene diisocyanate; 1 ,4- cyclohexane diisocyanate; isophorone diisocyanate; 4,4'-dicyclohexylmethane diisocyanate; 2,2'-diethylether diisocyanate; hydrogenated xylylene diisocyanate, and hexamethylene diisocyanate-biuret.

The aromatic diisocyanate compounds include, for example, /?-phenylene diisocyanate; tolylene diisocyanate; xylylene diisocyanate; 4,4'-diphenyl diisocyanate; 2,4'- diphenylmethane diisocyanate; 1 ,5 -naphthalene diisocyanate; 4,4'-diphenylmethane diisocyanate (MDI); 3,3 '-methyleneditolylene-4,4'-diisocyanate; tolylenediisocyanate- trimethylolpropane adduct; 4,4'-diphenylether diisocyanate; tetrachlorophenylene diisocyanate and 3,3 '-dichloro-4,4'-diphenylmethane diisocyanate.

In a particular embodiment, the diisocyanate is selected from the group consisting of 1 ,6-hexamethylaminediisocyanate (HDI); isophore diisocyanate (IPDI); 4,4-methylene bis(cyclohexyl isocyanate) (Hi ₂ MDI); 2,4-toluene diisocyanate (TDI); 2,6-toluene diisocyanate (TDI); 4,4'-diphenylmethane diisocyaante (MDI); 2,4'-diphenylmethane diisocyaante (MDI); xylylene diisocyanate (XDI); l ,3-bis(isocyanmethyl)cyclohexane (H6-XDI); 2,2,4-trimethylhexamethylene diisocyaante; 2,4,4-trimethylhexamethylene diisocyaante (TMDI); m-tetramethylxylylene diisocyanate (TMXDI); p- tetramethylxylylene diisocyanate (TMXDI); isocyanatomethyl-l ,8-octane diisocyanate (TIN); l ,3-bis(isocyanatomethyl)benzene; 1 ,4-tetramethylene diisocyanate; trimethylhexane diisocyanate; 1 ,6-hexamethylene diisocyanate; 1 ,4-cyclohexyl diisocyanate; lysine diisocyanate; and mixtures of any two or more thereof.

In a preferred embodiment, the diisocyanate used to prepare the thermoplastic polyurethane is 2,4-toluene diisocyanate (TDI), 2,6-toluene diisocyanate (TDI) or 4,4'- diphenylmethane diisocyaante (MDI).

Diisocyanates suitable for obtaining the thermoplastic polyurethane can be synthesized according to procedures already known for a skilled in the art. However, they are also available commercially under different trade names in various grades and formulations. The selection of suitable commercially-available diisocyanates as reagent to produce thermoplastic polyurethane is within the capability of one skilled in the art of polyurethanes technology. The diisocyanate compound is preferably employed in a molar amount approximately equal to the total molar amount of the polyether carbonate polyol and the chain extender. Particularly, as the isocyanate compound is a diisocyanate, and the polyether carbonate polyol is a polyether carbonate diol, the diisocyanate is used in an equivalent weight ratio of total active hydrogen atoms contained in the polyether carbonate diol and the chain extender to the isocyanate groups of the diisocyanate of 1 :0.8 to 1 : 1.2.

The reaction mixture also includes a chain extender which is a small molecule reactive toward isocyanates. Reactive small molecules include low molecular weight organic molecules having one or more functional groups, such as alcohols, amines, carboxylic acids, thiols, and combinations thereof.

In a preferred embodiment, said chain extender is an alcohol, more preferably is a polyhydric alcohol, even more preferably is an aliphatic or cycloaliphatic dihydric alcohol comprising from 2 to 20 carbon atoms. Examples of dihydric alcohols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4- butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonadediol, 1,10- decanediol, neopentyl glycol, 3-methyl- 1,5-pentanediol, 3,3-dimethylolpentane, 1,4- cyclohexanediol, 1,4-cyclohexanedimethanol and 1 ,4-dihydroxyehtyl cyclohexane. Preferably, the dihydric alcohol is 1,4-butanediol.

Other dihydric alcohols include diethylene glycol, triethylene glycol, tetraethylene glycol, higher poly(ethylene glycols), such as those having number average molecular weights of from 220 to about 2000 g/mol, dipropylene glycol, tripropylene glycol, and higher poly(propylene glycols), such as those having number average molecular weights of from 234 to about 2000 g/mol.

Other dihydric alcohols may include an aromatic group in the structure of the molecule although the alcohol groups are contained in an aliphatic chain. Examples of these compounds include, for example, 2-[3-(2-Hydroxy-ethoxy)-phenoxy]-ethanol and 2- [4- (2-Hydroxy-ethoxy)-phenoxy] -ethano 1.

Other chain extenders may also include an aliphatic or aromatic polyamine compounds, for example, ethylene diamine, 1 ,2-propylene diamine, 1,6-hexamethylene diamine, piperazine and meta- or para-xylene diamine; aliphatic, cycloaliphatic or aromatic aminoalcohol compounds, for example, ethanolamine, N-methyldiethanolamine, N- phenylpropanolamine; hydroxyalkyl sulfamides, for example, hydroxyethyl sulfamide and hydroxyethylaminoethyl sulfamide; urea and water.

The chain extender is generally used in an amount from 1 to 20 wt% of the total weight of the thermoplasctic polyurethane. Conventional mo no functional compounds such as chain terminators or mold release aids, may also be used in small amounts. Examples of suitable mono functional compounds include alcohols such as octanol and stearyl alcohol, and amines, such as butylamine and stearylamine.

Blowing agents can also be added to the reaction mixture. These blowing agents may be chemical blowing agents (typically molecules that react with components to liberate C0 ₂ or other volatile compounds) or physical blowing agents (typically molecules with a low boiling point that vaporize during the foam formation). Many blowing agents are known in the art and may be applied to the composition of the invention according to conventional methodology. The choice of blowing agent and the amounts added can be a matter of routine experimentation.

Examples of chemical blowing agents include water and formic acid. Water functions as a blowing agent by reacting with a portion of the isocyanate in the mixture to produce carbon dioxide gas. Similarly, formic acid reacts with a portion of the isocyanate to produce carbon dioxide and carbon monoxide gas. Suitable physical blowing agents include hydrocarbons, such as butane, isobutene, 2,3- dimethyl butane, pentane isomers, hexane isomers, heptane isomers and cycloalkanes including cyclopentane, cyclohexane and cycloheptane; fluorine-containing organic molecules, such as perfluorinated compounds, chlorofluorocarbons, hydrochlorofluorocarbons and hydrofluorocarbons; chloride-containing organic molecules, such as perchlorinated compounds and hydrochlorocarbons; acetone; methyl formate and carbon dioxide.

When used, the blowing agent is added in an amount of from 1 to 20 wt% with respect to the poly ether carbonate polyol in the composition.

In a particular embodiment, the process for obtaining the thermoplastic polyurethane further includes the addition of a catalyst to the reaction mixture. A conventional catalyst comprising an amine compound or tin compound can be employed to promote the polymerization reaction. Any suitable urethane catalyst may be used, including tertiary amine compounds, guanidines, amidines, and organometallic compounds.

Exemplary tertiary amine compounds include triethylene diamine, N-methyl morpholine, Ν,Ν-dimethylcyclohexyl amine, pentamethyldiethylene triamine, tetramethy ethylene diamine and dimethylbenzylamine. Exemplary guanidine compounds include triaza bicycle 4.4.0 dec-5-ene (TBD), N-methyl triaza bicycle 4.4.0 dec-5-ene (MTBD) and pentamethyl guanidine. Exemplary amidine compounds include N-methyl imidizol and l,8-diazabicylo[5.4.0]undec-7-ene (DBU). Exemplary organometallic catalysts include organomercury, organolead, organobismuth, organoferric and organotin catalysts, such as dibutyltin dilaurate, dibutylbis(laurylthio)stannate, dibutyltinbis(isooctylmercapto acetate) and dibutyltinbis(isooctylmaleate), tin octanoate and mixtures thereof.

Suitable tin catalysts include stannous chloride; tin salts of carboxylic acids, such as dibutyltin dilaurate; dibutylbis(laurylthio) stannate, dibutyltinbis(isooctylmercapto acetate) and dibutyltinbis(isooctylmaleate), tin octanoate (or 2-ethyl-hexanoate) and mixtures thereof.

Typical amounts of catalysts are 0.001 to 10 parts of catalyst per 100 parts by weight of total polyol in the reaction mixture. In addition to the thermoplastic polyurethane components mentioned above, customary auxiliaries and/or additives can also be added. Such additives may include, but are not limited to, plasticizers, lubricants, stabilizers, colorants, flame retardants, inorganic and/or organic fillers and reinforcing agents.

Plasticizers may be used to modify the rheological properties to a desired consistency. Such plasticizers should be free of water, inert to isocyanate groups and compatible with a polymer. Suitable plasticizers are well known to those skilled in the art and include, but are not limited to, alkyl phthalates such as dioctylphthalate or dibutyl phthalate, partially hydrogenated terpene, trioctyl phosphate, epoxy plasticizers, toluene-sulfamide, chloroparaffms, adipic acid esters, castor oil, toluene and alkyl naphthalenes. The plasticizer is added to the composition in a sufficient amount to provide the desired rheological properties and to disperse any catalyst that may be present in the system.

As lubricants, non-reactive liquids can be used to soften the thermoplastic polyurethane or to reduce its viscosity for improved processing. Examples of lubricants include fatty acid esters and/or fatty acid amides.

Stabilizers may include oxidation stabilizers, hydrolysis stabilizers and/or UV stabilizers. Examples of hydrolysis stabilizers include oligomeric and/or polymeric aliphatic or aromatic carbodiimides. As UV stabilizers, hydroxybenzotriazoles, zinc dibutyl thiocarbamate, 2,6-ditertiary butylcatechol, hydroxybenzophenones, hindered amines and phosphites can be used to improve the light stability of polyurethanes. Color pigments have also been used for this purpose.

The thermoplastic polyurethane composition of the invention may further comprise one or more suitable colorants. Typical inorganic coloring agents include, but are not limited to, titanium dioxide, iron oxides and chromium oxides. Organic pigments may include azo/diazo dyes, phthalocyanines and dioxazines as well as carbon black.

The composition of the invention may further comprise one or more suitable flame retardants to reduce flammability. The choice of flame retardant for any specific thermoplastic polyurethane composition often depends on the intended service application of that thermoplastic polyurethane and the attendant flammability testing scenario governing that application. Examples of such flame retardants include chlorinated phosphate esters, chlorinated paraffins and melamine powders.

Optional additives of the thermoplastic polyurethane composition of the invention include fillers. Such fillers are well known to those skilled in the art and include, but are not limited to, carbon black, titanium dioxide, calcium carbonate, surface treated silicas, titanium oxide, fume silica, talc, aluminium trihydrate and the like. In certain embodiment, a reinforcing filler is used in sufficient amount to increase the strength of the composition and/or to provide thixotropic properties to the composition.

Other optional additive to be used in the composition of the invention includes clays. Suitable clays include, but are not limited to, kaolin, surface treated kaolin, calcined kaolin, aluminum silicates and surface treated anhydrous aluminum silicates. The clays can be used in any form. Preferably, the clay is in the form of pulverized powder, spray- dried beads or finely ground particles.

The amount of the additives described above will vary depending on the desired application. The thermoplastic polyurethane obtained according to any of the procedures mentioned above has hydroxyl or isocyanate terminal groups. Thus, the thermoplastic polyurethane of the invention can be further polymerized linearly or in a three-dimensional network structure by reacting with a compound having at least two hydrogen atoms reactive to isocyanate groups per molecule, or a compound having two isocyanate groups per molecule. Also, by reacting with a compound having a urethane bond and/or urea bond or a compound having at least three hydrogen atoms reactive to the isocyanate groups, the thermoplastic polyurethane can be modified with a cross-linking structure introduced therein.

In a particular embodiment, the polyurethane thermoplastic has a tensile strength ranging from 35 to 70 MPa, more preferably from 40 to 60 MPa, measured according to ISO-37.

An additional aspect of the present invention refers to a process for manufacturing molded articles using the thermoplastic polyurethane prepared by the process as described above. For example, injection molding, extrusion, calendaring or blow molding can be used for manufacturing the molded articles, being preferred the use of injection molding. The process for manufacturing molded articles using the thermoplastic polyurethane composition of the invention by injection molding comprises (a) heating the thermoplastic polyurethane to a temperature above its melting point; (b) injecting the melted thermoplastic polyurethane into a mold; (c) cooling the thermoplastic polyurethane in the mold to a temperature below its solidification temperature to produce the molded articles; and (d) removing the molded article from the mold. During processing by injection molding, the thermoplastic polyurethane solidifies rapidly and is therefore easily removed from the mold.

The following examples merely illustrate the invention. Those skilled in the art will recognize many variations that can be performed without altering the functioning of the invention. Examples

Example 1. Preparation of zinc hexacyanocobaltate catalyst using TBA as organic complexing agent and polypropylene glycol (PPG) synthesized under basic conditions (MWn 400) as poly ether polyol {DMC catalyst).

DMC catalyst was prepared following the procedure disclosed in comparative Example 2 in WO 2012/156431 as follows:

1 ^st step: Potassium hexacyanocobaltate (7.5 g) was dissolved in deionized water (100 ml) in a beaker (Solution A). Zinc chloride (75 g) and tert-butyl alcohol TBA (75 mL) were dissolved in deonized water (275 mL) in a second beaker (Solution B). Solution B was heated at a temperature of 50°C. Subsequently, solution A was slowly added for 30 minutes to the solution B while stirring at 400 rpm. The aqueous zinc chloride and TBA solution and the cobalt salt solution were combined using a stirrer to intimately and effectively mix both aqueous solutions. The mixture was held post-reacting for 30 minutes at the same temperature to form a slurry of zinc hexacyanocobaltate. A third solution (solution C) was prepared by dissolving a 400 mol. wt. diol (8 g, polypropylene glycol(PPG)) in deonized water (50 mL) and TBA (3 mL). Said diol was synthesized by basic catalysis following procedures widely known in the art. Solution C (the PPG /water/TBA mixture) was added to the aqueous slurry zinc hexacyanocobaltate for 5 minutes, and the product was stirred for 10 additional minutes. The mixture was filtered under pressure to isolate the solid.

2 ^nd step: The solid cake was reslurried in water (208 mL) for 30 minutes at a temperature of 50°C and subsequently, additional 400 mol. wt diol PPG (2 g) was added. The mixture was homogenized by stirring for 10 minutes and filtered.

3 ^rd step: The solid cake obtained after the second step was reslurried in TBA (280 mL) for 30 minutes at a temperature of 50°C and subsequently, additional 400 mol. wt diol PPG (1 g) was added. The mixture was homogenized by stirring for 5 minutes and filtered. The resulting solid catalyst was dried under vacuum at 100°C and 10 mbar to constant weight. The DMC catalyst having a polyether polyol synthesized under acidic catalysis can be prepared following a similar process, as shown in Example 3 in WO 2012/156431. Example 2. Acidic catalysis synthesis of propoxylated glycerol (400 mol. wt diol)

Polypropylene glycol (190 g) was charged into the reactor, purged with N ₂ and dehydrated at 130°C (until H ₂ 0 < 500 ppm). Then, propylene glycol was stabilized at 50°C and the catalyst HBF ₄ (2 g of a 50% concentration by weight, 1000 ppm) was added to the reactor. Propylene oxide feeding (868 g) was started slowly at atmospheric pressure, controlling the flow rate in order to control the temperature (50 °C) and pressure (below 1 bar). As the reaction proceeded it slowed down, increasing the pressure (pressure was controlled not to exceed 3 bar). When the reaction was finished, the mixture was left for 2 h (post-reaction). Subsequently, vacuum was applied for 1 h at 120°C with N ₂ stripping in order to remove residual monomers. Then, the reactor was cooled to 30°C and the product discharged. The product obtained has the following properties: IOH = 295±10 mg KOH/g; Humidity <500 ppm; Acidity <0.35 mg KOH/g; Viscosity <100 cps.

Example 3. Synthesis of poly ether carbonate polyols (PCP).

A five-liter stainless steel reactor was charged with 490 g of the initiator substance obtained according to the procedure described in example 2 above. The reactor was heated to 130°C while vacuum was applied with N ₂ stripping. After reaching the desired temperature, vacuum was continued for 30 min more. When the initiator was dried (H ₂ 0< 100 ppm), the DMC catalyst (250 mg) was added.

A first portion of propylene oxide (75 g.) was added to the reactor for the catalyst activation. A waiting time was observed until a temperature peak (hotspot) and a pressure drop occurs. Optionally, a second portion of propylene oxide was added in the absence of C0 ₂ and a waiting time was observed until activation occurred. Carbon dioxide was then introduced into the reactor until the desired pressure (25 bar) and a further portion of 50 g. propylene oxide was added. After catalyst activation was observed, the remaining propylene oxide (1575 g) needed for a polyether carbonate Diol Mw 2000, was slowly and continuously pumped into the reactor. When the carbon dioxide pressure decreased a certain value, further C0 ₂ was admitted.

When co-feeding of propylene oxide and carbon dioxide was started, temperature was decreased to 95°C. When propylene oxide addition was completed, the mixture was stirred at said temperature for 60 min. Finally, residual monomers were removed under vacuum with N ₂ stripping for 1 h at 95°C. The reactor was cooled and the product discharged. Finally, the reaction mixture was passed through a thin film evaporator to eliminate residual propylene carbonate.

The poly ether carbonate polyol has the following properties:

a Calculated excluding the initiator and the propylene oxide activation

Example 4. Synthesis of thermoplastic polyurethanes Starting materials

The polyether carbonate polyol used in the preparation of thermoplastic polyurethanes were that obtained according to the process described in example 3 above with reference PCP1.

For comparative purposes, thermoplastic polyurethanes were also prepared from polyether polyols with references PPG2000 and PTMG2000.

PPG2000: It is a difunctional polypropylene glycol with secondary terminal hydroxyl groups and a hydroxyl number of 55.6 mgKOH/g, which is equal to an equivalent weight of 1009 g/eq or a molecular weight of 2018 g/mol.

PTMG2000 (supplied by Aldrich): It is a difunctional polytetramethylene glycol with primary terminal hydroxyl groups and a molecular weight calculated using proton NMR of 2079 g/mol.

All the polyols were heated at 100°C under vacuum for 2 hours and kept under vacuum until use to eliminate residual water and prevent water absorption.

4,4'-diphenyl methane diisocyanate (supplied by Aldrich): This diisocyanate was purified by distillation in a sublimator and stored under vacuum until use. Over time, this diisocyanate starts to form dimers which do not react under the conditions in which a polyurethane formation reaction takes place. Dimer formation means that the amount of isocyanate groups available is less than the theoretical amount. Therefore, pure diisocyanate was used until, in the prepolymer formation reaction, instead of obtaining a transparent mass, the latter started to have a milky appearance, indicating the presence of dimers and thus indicating that dimerization has occurred in a significant amount. The time it took for the prepolymer to no longer be completely transparent was a little more than two weeks, and therefore pure diisocyanate is always used within 15 days after purification. This diisocyanate will be referred to in this specification as MDI.

1,4-butanediol (supplied by Aldrich): This diol (chain extender) was purified by drying it overnight with a drying agent and distilling it the next day. It was stored in an amber- colored bottle closed with a septum through which the necessary diol was extracted at all times without air entering the bottle, thus preventing the diol from absorbing water. This diol will be referred to as BD.

Ν,Ν-dimethylacetamide (DMAc), a polar aprotic solvent maintaining the polyurethane formed in solution, was used as the solvent for the PU formation reaction. The DMAc was purified with the following process: a commercial MDI polyisocyanate was dissolved and left to react with possible water and possible impurities for several hours; the DMAc was then distilled at reduced pressure and a temperature of 60°C. The distilled DMAc was stored in an amber-colored bottle closed with a septum through which the necessary solvent was extracted at all times without air entering the bottle, thus preventing the solvent from absorbing water. The pure DMAc was always used within the first 15 days after purification. Thermoplastic polyurethanes were synthesized using the prepolymer method by means of the following procedure.

The suitable amount of dry polyol and MDI were weighed in a 25 ml flask to obtain 2.5 g of final polymer, and it was kept under magnetic stirring for 3 hours at 80°C. Once that time has elapsed, 3 ml of DMAc, the necessary amount of BD (95-100% of the stoichiometric amount) dissolved in 2 ml of DMAc, and one drop of catalyst (stannous octoate) dissolved in 2 ml of DMAc were added. The solution was magnetically stirred for 3 hours at 80°C and then overnight at room temperature. During the 3 hour-reaction at 80°C, if the viscosity of the solution increased such that it blocked magnetic stirring, the necessary amount of DMAc was added to maintain stirring. This process, the formation of prepolymer mass and final polyurethane in solution with the least amount of solvent possible, aimed to prevent to the greatest extent possible any side reaction and to achieve the highest possible molecular weight in the polyurethane.

After the polyurethane formation reaction, the solution was poured over a flat piece of glass previously reacted with trimethyl-chloro-silane to prevent the film from adhering to the glass, with a glass ring 10 cm in diameter to contain the expansion of the solution. The obtained films therefore had thicknesses approximately in the range of 150-250 microns. The silane-coated glass with the polymer solution was covered with a conical funnel to prevent it from being contaminated by dust from the environment and to prevent the solvent from evaporating too quickly. It was kept overnight at 80°C. The film was removed from the glass the next day and continued drying at room temperature under vacuum for at least 3 days. After this process, samples were die-cut from the resulting film in order to be used for the measurements of their different properties.

Experimental techniques The thermal properties were determined in a Mettler Toledo model DSC822e differential scanning calorimeter. With a suitable die, disks weighing about 10 mg were cut from prepared films and they were placed in an aluminum capsule with a perforated cover. The heating protocol was as follows: heating at 10°C/min from 25°C to 200°C, cooling from that temperature to -90°C, leaving at that temperature for 3 minutes and heating the sample from -90 to 200°C at 10°C/min.

The mechanical tensile properties were determined in a Synergy dynamometer with a 100 N load cell. Die-cut test pieces in the shape of a small dumbbell (S2 in ISO 37 standard) were tested at a clamp separation rate of 200 mm/min with an initial separation of 20 mm. Elongation was calculated based on clamp separation length, taking the 10 mm of the narrow part of the dumbbell-shaped test piece as the initial reference.

The properties of the different samples are shown in table II:

Samples Starting wt% of wt% of Tg (°C) Tensile Strain

polyol hard BD with strength (%)

segment respect to (MPa)

(wt% theoretical

HS)

comp.

The Tg value for the thermoplastic polyurethanes obtained from polyether carbonate polyols is greater than the values obtained for those synthesized from conventional polyether polyols, reaching about -13°C for TPU 1-35. An increase in the hard segment content from 35 to 50% slightly increases the Tg value, but the effect is very small, not more than 3°C.

It can also be seen that the tensile strength values of polyether carbonate polyol-based TPUs are the highest both at 35 and 50% by weight of HS.

At the same time, strain values are the highest for 35% of HS and of the same order as for other polyols for 50% of HS.

These experimental results have also pointed out that when comparing a polyurethane thermoplastic obtained from a polyol ether (without any carbonate group) with a polyurethane prepared from a polyol ether carbonate obtained by the process as described in the present invention, such as diol PCP1 having 19.6 wt% of C0 ₂ , the tensile strength increased up to 309% in the case of the diol having a hard segment content of 35% and up to 124% in the case of the diol having a hard segment content of 50%.

This improvement in the tensile strength is significantly higher than that observed for polyurethane thermoplastic obtained from polyol ether carbonates that, having also high C0 ₂ content, have been prepared by other processes different from the one herein described. In document DE102012218848 (see Table 2, compounds 1 and 2), an increase of only 45% (32.2 MPa vs. 22.2 MPa) was observed for the same physical property (tensile strength) when comparing a polyurethane obtained from a polyol ether (polyol 1, without any carbonate group) with a polyurethane prepared from a polyol ether carbonate as described in said document (polyol 2) having 15.1 wt% of C0 ₂ and 39.7% of hard segment content.

Thus, these results are a clear indication that the process described herein to produce polyol ether carbonates provides a different compound since the properties of the polyurethane thermoplastic obtained from it are different, even when similar content of C0 ₂ and hard segment is incorporated in the polymer structure.