WO2016120406A1

WO2016120406A1 - A polyurethane adhesive formulation based on polyether carbonate polyol

Info

Publication number: WO2016120406A1
Application number: PCT/EP2016/051839
Authority: WO
Inventors: Susana GARCÍA RAMOS; Mónica GARCÍA RUIZ; María Dolores BLANCO GONZÁLEZ; Román GALDÁMEZ
Original assignee: Repsol, S.A.
Priority date: 2015-01-28
Filing date: 2016-01-28
Publication date: 2016-08-04

Abstract

The present invention refers to a polyurethane adhesive formulation 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. It also relates to a method of joining two substrates, said method comprising the step of applying an adhesive formulation as defined above.

Description

A POLYURETHANE ADHESIVE FORMULATION BASED ON POLYETHER

CARBONATE POLYOL

FIELD OF THE INVENTION

The present invention belongs to the field of polyurethane adhesives, more particularly to polyurethane adhesives comprising segments derived from polyether carbonate polyols, methods for their preparation, as well as their use for joining substrates.

BACKGROUND

Polyurethane adhesive compositions are used as universal binder in a range of industrial sectors. Polyurethane adhesives bind to many substrates due to their physical bonding forces. They have therefore found use in a number of industrial applications, such as for example the furniture industry, the car industry, shoe manufacturing and even in the textile industry, for the manufacture of fabric and film composites.

Polyurethane adhesives are normally defined as those adhesives that contain a number of urethane groups in the backbone of a polymer, regardless of the chemical composition of the rest of the chain. Thus, a typical urethane adhesive may contain, in addition to urethane linkages, aliphatic and/or aromatic hydrocarbons, esters, ethers, amides, urea and allophonate groups. Typically, an isocyanate group reacts with the hydroxyl groups of a polyol to form the repeating urethane linkage.

Thus, linear polyurethane adhesives may be obtained by reacting a diol with a diisocyanate. When polyols with three or more reacting hydroxyl groups (i.e. functionality of three or more) are reacted with a polyisocyanate, or when isocyanates having three or more isocyanate groups are reacted with a polyol, the resulting polymer is crosslinked. However, in reaction systems where there is an excess of isocyanates, crosslinking reactions may also occur.

Thus, polyols, and in particular, polyether polyols are widely used in the polyurethane adhesive technology to react with isocyanates in order to provide polyurethane adhesive compositions.

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 WO2013/158621 describes the use of polycarbonate polyols with a high content of carbonate linkages derived from the copolymerization of CO₂ with one or more epoxides to produce a 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.

Application WO2011/146252 discloses a two-component polyurethane adhesive composition having a first component containing a polyol, such as a polycarbonate polyol, a second component containing one or more isocyanates, a catalyst and a blocking agent.

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 C0₂. 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 adhesives 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 C0₂ incorporated in the backbone of the polymer are of particular interest to produce polyurethane compositions, and more specifically polyurethane adhesive compositions, with improved properties.

BRIEF DESCRIPTION OF THE INVENTION

The authors of the present invention have developed a new polyurethane adhesive formulation 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 polyurethane adhesive formulation 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 polyurethane adhesive formulation with improved physical properties when compared to polyurethanes derived from polyether polyols or from polyether carbonate polyols having a lower content of carbonate linkages or having been obtained by other processes. In particular, the polyurethane adhesive formulation of the present invention presents an improved tensile strength as well as a higher elongation or percentage extension for breaking. In addition to that, the tests carried out and detailed in the experimental part have pointed out that said formulation provides improved adhesive properties as higher strength should be applied to separate the bonded substrates. As explained in more detail in the experimental part, the polyurethane formulation of the present invention has shown an improvement of about 37% in tensile strength and 26%> in elongation with respect to polyurethanes obtained from polyol ethers where no carbonate groups are present, in contrast to polyurethane formulations, such as those described in document DE102010019504, which derive from polyether carbonate polyols obtained by a different process but having similar content of CO₂ where only an improvement of 2%> in tensile strength has been observed.

Thus, a first aspect of the present invention refer to a polyurethane adhesive formulation 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.

In a particular embodiment, the adhesive formulation comprises a polyurethane prepolymer obtainable by reacting a polyether carbonate polyol as defined above with one or more di- or poly-isocyanates.

In another particular embodiment, said adhesive formulation is a one-component formulation comprising a polyurethane prepolymer as defined above.

In another particular embodiment, the adhesive formulation is a two-component formulation comprising a first component and a second component, said first component comprises a polyether carbonate polyol as defined above and said second component comprises one or more di- or poly-isocyanates.

Another aspect of the invention refers to a method of joining two substrates, said method comprising the step of applying an adhesive formulation as defined in any of the particular embodiments mentioned above, arranging the substrates so that both substrates are in contact with the adhesive formulation, and curing the adhesive formulation.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows the arrangement of the samples in the shear stress test.

Figure 2 shows a scheme of the different types of failing produced in a shear stress test.

DETAILED DESCRIPTION OF THE INVENTION

As mentioned before, a first aspect of the present invention refers to a polyurethane adhesive formulation 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:

- 0-10% by weight of a 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 polyurethane adhesive formulation with improved properties when compared to polyurethanes derived from polyether polyols or from polyether carbonate polyols having a lower percentage of carbonate linkages or having been obtained by other processes. DMC catalyst

The DMC catalyst used in the process as described above can be obtained by a process comprising:

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,

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 hexacyanoferrate (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-C₆ aliphatic alcohols, selected from the group consisting of ethanol, isopropyl alcohol, n- butyl alcohol, z o-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 hexacyanoferrate (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. 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 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 BF₃, SbF₅, Y(CF₃S0₃)₃, or Bronsted acids such as CF₃S0₃H, HBF₄, HPF₆, HSbF₆.

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

Using a polyether polyol 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

- 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.

Step b

The isolated polyether polyol-containing solid catalyst is then first washed with an aqueous solution comprising 90-100%o 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 polyether 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 110°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 teri-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 teri-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 teri-butyl alcohol and the polyether polyol has been synthesized by acidic catalysis. Preferably, the organic complexing agent is teri-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 teri-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.

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 adhesive formulation 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-C₆ 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 one or more compounds selected from the group consisting of mono- or poly-hydric alcohols, polyvalent amines, polyvalent thiols, aminoalcohols, thioalcohols, hydroxy esters, polyether polyols, polyester polyols, polyester ether polyols, polyether carbonate polyols, polycarbonate polyols, polycarbonates, polyethyleneimines, polyether amines, polytetrahydrofurans, polytetrahydrofuranamines, polyether thiols, polyacrylate polyols, castor oil, the mono- or di-glyceride of ricinoleic acid, monoglycerides of fatty acids, chemically modified mono-, di- and/or tri-glycerides of fatty acids, and Ci-C₂4-alkyl fatty acid esters that contain on average at least 2 hydroxyl groups per molecule.

In a particular embodiment, the H-functional initiator substance is a polyhydric alcohol also known as polyol, more particularly is a polyether polyol, preferably having a number molecular weight from 100 to 4000 Da. More preferably, the polyether polyol has a functionality from 2 to 8, i.e., it has from 2 to 8 hydroxyl groups per molecule, even more preferably is a diol or a triol. Suitable 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 having from two to eight hydroxyl groups, more preferably diols and triols. In a particular embodiment, the polyether polyol is a triol. In another particular embodiment, the polyether polyol ether is a diol. Preferably, the polyether polyol is a poly(oxypropylene) diol or triol 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 polyol 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 BF₃, SbF₅, Y(CF₃S0₃)₃, or Bronsted acids such as CF₃S0₃H, HBF₄, HPF₆, HSbF₆.

In a particular embodiment, the H-functional initiator substance is a polyether polyol that has been synthesized by acidic catalysis. Preferably, it is a polyether triol or 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.

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 adhesive formulation 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 N₂ 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 N₂ 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 CO₂ or preferably in the absence of CO₂,

(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 C0₂,

(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 C0₂,

(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 CO₂;

(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, 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 at least two, preferably from two to eight. 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 35 wt%, still more preferably from 5 to 25 wt%, even more preferably from 12 to 25 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 is a triol having from 5 to 50 wt% of carbon dioxide, more preferably from 5 to 35 wt%, still more preferably from 10 to 30 wt%, even more preferably from 12 to 25 wt%, and particularly preferable from 18 to 22 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 is a diol having from 5 to 50 wt% of carbon dioxide, more preferably from 5 to 35 wt%, still more preferably from 5 to 20 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 15 to 35 wt%, based on the total weight of the polyether carbonate polyol excluding the initiator and the alkylene oxide activation.

In another particular embodiment, the polyether carbonate polyol obtained according to this process is a triol having from 5 to 50 wt% of carbon dioxide, still more preferably from 10 to 35 wt%, even more preferably from 15 to 35 wt%, and particularly preferable from 25 to 35 wt% or from 25 to 32 wt%, based on the total weight of the polyether carbonate polyol excluding the initiator and the alkylene oxide activation.

In another particular embodiment, the polyether carbonate polyol obtained according to this process is a diol having from 5 to 50 wt% of carbon dioxide, still more preferably from 5 to 35 wt%, even more preferably from 5 to 25 wt%, and particularly preferable from 8 to 22 wt% or from 15 to 22 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 polyether carbonate polyol from which the segments comprised in the adhesive formulation of the invention derive has a functionality of at least two, preferably from two to eight, even more preferably a functionality of 2 or 3, i.e. two or three hydroxyl groups per molecule. Thus, the polyether carbonate polyol from which the segments comprised in the adhesive formulation of the invention derive is preferably a polyether carbonate diol or a polyether carbonate triol, even more preferably is a polyether carbonate triol.

In another preferred embodiment, the polyether carbonate polyol from which the segments comprised in the adhesive formulation of the invention derive has from 5 to 35 wt% of carbon dioxide, more preferably from 12 to 25 wt%, 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 adhesive formulation of the invention derive is a triol having from 5 to 35 wt% of carbon dioxide, still more preferably from 10 to 30 wt%, even more preferably from 12 to 25 wt%, and particularly preferable from 18 to 22 wt%, based on the total weight of the final polyether carbonate polyol.

In another particular embodiment, the polyether carbonate polyol from which the segments comprised in the adhesive formulation of the invention derive is a diol having from 5 to 35 wt% of carbon dioxide, more preferably from 5 to 20 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 from which the segments comprised in the adhesive formulation of the invention derive has from 5 to 35 wt% of carbon dioxide, more preferably from 10 to 35 wt%, even more preferably from 15 to 35 wt%, based on the total weight of the polyether carbonate polyol excluding the initiator and the alkylene oxide activation. In another particular embodiment, the polyether carbonate polyol from which the segments comprised in the adhesive formulation of the invention derive is a triol having from 10 to 35 wt% of carbon dioxide, more preferably from 15 to 35 wt%, and particularly preferable from 25 to 35 wt% or form 25 to 32 wt%, based on the total weight of the polyether carbonate polyol excluding the initiator and the alkylene oxide activation.

In another particular embodiment, the polyether carbonate polyol from which the segments comprised in the adhesive formulation of the invention derive is a diol having from 5 to 35 wt% of carbon dioxide, even more preferably from 5 to 25 wt%, and particularly preferable from 8 to 22 wt% or from 15 to 22 wt%, based on the total weight of the polyether carbonate polyol excluding the initiator and the alkylene oxide activation.

In a particular embodiment, the polyurethane adhesive formulation of the present invention comprises a polyurethane prepolymer obtainable by reacting a polyether carbonate polyol as defined herein above with one or more di- or poly-isocyanates. Said isocyanates react with the reactive end groups of the polyether carbonate polyol to render higher molecular weight structures through chain extension and/or cross-linking. The resulting prepolymer comprises a plurality of segments derived from the polyether carbonate polyols linked via urethane bonds.

In a particular embodiment, the prepolymer is obtained by reacting a polyether carbonate polyol as defined herein above with a stoichiometric excess of one or more di-isocyanates. As will be appreciated by those skilled in the art, the degree of polymerization of this prepolymer (i.e., average number of polyol segments contained in the prepolymer chains) can be modified by controlling the relative amount of isocyanate as well as the order of reagent addition and the reaction conditions.

In a particular embodiment, the polyurethane prepolymer has a Tg from -25°C to -50°C, more preferably from -25°C to -40°C, even more preferably from -30°C to -37°C, when the polyether carbonate polyol used to prepare said prepolymer is a triol.

In another particular embodiment, the polyurethane prepolymer has a Tg from -40°C to -50°C, when the polyether carbonate polyol used to prepare said prepolymer is a diol.

In another particular embodiment, the prepolymer has an isocyanate content of from 3 to 30 wt%, more preferably from 5 to 25 wt%, even more preferably from 5 to 10 wt%, on average in the prepolymer.

A large number of isocyanates are known in the art which can be used in the process for obtaining the polyurethane prepolymer. However, in a particular embodiment, the isocyanate used to prepare said prepolymer comprises two or more isocyanate groups per molecule. In a particular embodiment, the isocyanate is a di-isocyanate. In another particular embodiment, the isocyanate is a higher polyisocyanate, such as a tri-isocyanate, a tetraisocyanate, a isocyanate polymer or oligomer, and the like, which are typically a minority component of a mix of predominantly diisocyanates.

In a particular embodiment, the isocyanate is an aliphatic or cycloaliphatic polyisocyanate or a derivative thereof or an oligomer of an aliphatic or cycloaliphatic polyisocyanate. In another particular embodiment, the isocyanate is an aromatic polyisocyanate or a derivative thereof or an oligomer of an aromatic polyisocyanate. In another particular embodiment, the isocyanate may comprise mixtures of any two or more of the above type of isocyanates.

Suitable aliphatic and cycloaliphatic isocyanate compounds include, for example, 1,3- trimethylene diisocyanate; 1,4-tetramethylene diisocyanate; 1,6-hexamethylene diisocyanate; 2,2,4-trimethylhexamethylene disocyanate; 2,4,4-trimethylhexamethylene disocyanate; 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 isocyanate 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; triphenylmethane triisocyanate; 4,4'-diphenylether diisocyanate; tetrachlorophenylene diisocyanate; 3,3'-dichloro-4,4'-diphenylmethane diisocyanate; and triisocyanate phenylthiophosphate.

In a particular embodiment, the isocyanate is selected from the group consisting of 1,6- hexamethylaminediisocyanate (HDI); isophore diisocyanate (IPDI); 4,4-methylene bis(cyclohexyl isocyanate) (H₁₂MDI); 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); 4,4 ',4 "-triphenylmethane triisocyanate; tris(/ isocyanatomethyl)thiosulfate; 1 ,3-bis(isocyanatomethyl)benzene; 1 ,4-tetramethylene diisocyanate; trimethylhexane diisocyanate; 1,6-hexamethylene diisocyanate; 1,4-cyclohexyl diisocyanate; lysine diisocyanate; HDI allophonate trimer; HDI-trimer and mixtures of any two or more thereof. In a preferred embodiment, the isocyanate used to prepare the polyurethane prepolyner is 2,4- toluene diisocyanate (TDI) or 2,6-toluene diisocyanate (TDI).

Isocyanates suitable for obtaining the polyurethane prepolymer 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 isocyanates as reagent to produce polyurethane prepolymers for adhesive applications is within the capability of one skilled in the art of polyurethanes technology.

In a particular embodiment of the invention, the polyurethane adhesive formulation of the invention further comprises a catalyst. Conventional catalysts comprising an amine compound or tin compound may be used to promote the polymerization reaction between the polyether carbonate polyol and the isocyanate.

Any suitable urethane catalyst may be used, including tertiary amine compounds and organometallic compounds. Examples of tertiary amine compounds include triethylene diamine, N-methylmorpholine, Ν,Ν-dimethylcyclohexyl amine, pentamethyldiethylene triamine, tetramethylehtylene diamine, 1 -methyl -4-dimethylaminoethylpiperazine, 3-methoxy-N- dimethylpropylamine, N-ethylmorpholine, diethylethanolamine, N,N-dimethyl-N,N' -dimethyl isopropylpropylene diamine, N,N-diethyl-3-diethylaminopropylamine, dimethylbenzylamine, DABCO, pentamethyldipropylenetriamine, bis(dimethylamino ethyl ether), dimethylcyclohexyl amine, DMT-30, triazabicyclodecene (TBD), N-methyl TBD, ammonium salts and combinations thereof. Examples of organometallic catalysts include organomercury, organolead, organoferric and organotin catalysts.

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

Typical amounts of catalysts are 0.001 to 10 parts of catalyst per 100 parts by weight of total polyol.

In a particular embodiment of the invention the polyurethane adhesive formulation further comprises additives as are known in the art of polyurethane adhesive technology. Such additives may include, but are not limited to, solvents, fillers, clays, blocking agents, stabilizers, thixotropes, plasticizers, compatibilizers, colorants, UV stabilizers, flame retardants, and the like. The polyurethane adhesive formulation of the invention or the prepolymer contained therein can be dispersed in a solvent which can include water or organic solvents known to those skilled in the art. Suitable solvents include aliphatic, aromatic, or halogenated hydrocarbons, ethers, esters, ketones, lactones, sulfones, nitriles, amides, nitromethane, propylene carbonate, dimethyl carbonate and the like. Representative examples include, but are not limited to, acetone, acetonitrile, benzene, butanol, butyl acetate, butyro lactone, chloroform, cyclohexane, 1,2- dichloromethane, dimethylsulfoxide, dimethylformamide, 1,4-dioxane, ethanol, ethyl acetate, ethyl ether, ethylene glycol, hexane, isopropyl acetate, methanol, methyl acetate, methylene chloride, methyl ethyl ketone, methyl methacrylate, propylene carbonate, propylene oxide, styrene, tetrahydrofuran, toluene and the like.

Optional additives of the polyurethane adhesive formulation 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 adhesive and/or to provide thixotropic properties to the adhesive.

Other optional additive to be used in the adhesive formulation 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 which facilitates formulation of pumpable adhesive. Preferably, the clay is in the form of pulverized powder, spray-dried beads or finely ground particles.

The adhesive formulation of the invention can include blocking agents to provide an induction period between the mixing of the two-parts of the adhesive composition, when said formulation is a two-part formulation as described herein after, and the initiation of the cure. The addition of the blocking agents provides an induction period which causes a reduction in the curing rate immediately after mixing of the components of the adhesive formulation. The reduction in the curing rate results in lower initial tensile shear strength and storage moduli immediately after mixing of the components.

Following the induction period, the adhesive quickly cures so that the tensile shear strength and storage moduli are similar to those produced by adhesives that do not contain the blocking agent. Such blocking agents include, but are not limited to, hydroxyl containing compounds such as diethylene glycol, mono alkyl ethers, butanone oxime, methyl ethyl ketone oxime, nonylphenol, phenol and cresol; amine containing compounds such as caprolactam, diisopropyl amine, 1 ,2,4-triazole and 3,5-dimethyl pyrazole; and aliphatic containing compounds such as dialkyl malonate.

The adhesive formulation of the invention may further comprise a thixotrope. Such thixotropes are well known to those skilled in the art and include, but are not limited to, alumina, limestone, talc, zinc oxides, sulfur oxides, calcium carbonate, perlite, cyclodextrin and the like. The thixotrope may be added to the adhesive formulation in a sufficient amount to provide the desired rheological properties.

The adhesive formulation of the invention may further comprise plasticizers so as 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, chloroparaffins, adipic acid esters, castor oil, toluene and alkyl naphthalenes. The plasticizer is added to the adhesive formulation in a sufficient amount to provide the desired rheological properties and to disperse any catalyst that may be present in the system.

The adhesive formulation 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 and carbon black.

UV-stabilizers can also be added to the adhesive formulation. Light protection agents, such as hydroxybenzotriazoles, zinc dibutyl thiocarbamate, 2,6-ditertiary butylcatechol, hydroxybenzophenones, hindered amines and phosphites have been already used to improve the light stability of polyurethanes. Color pigments have also been used for this purpose.

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

The amount of the additives described above will vary depending on the desired application. One-component adhesive formulation

In a particular embodiment, the adhesive formulation of the invention is a one-component formulation comprising a polyurethane prepolymer as defined above. The prepolymer is made with one or more polyether carbonate polyols as defined above. This prepolymer is typically produced by reacting a stoichiometric excess of isocyanate with the polyether carbonate polyol.

In a particular embodiment, the prepolymer has an isocyanate content of from 3 to 30 wt%, more preferably from 5 to 25 wt%, even more preferably from 5 to 10 wt%, on average in the prepolymer.

This adhesive formulation is typically cured with water which can be added or which is present in the atmosphere or in the material being bonded.

Any of the above described di-isocyanates or poly-isocyanates can be used to prepare the prepolymer. However, in a preferred embodiment, said isocyanate is a di-isocyanate selected from aliphatic or aromatic di-isocyanates, more preferably is MDI or TDI.

In a particular embodiment, the one -component adhesive formulation further comprises one or more additives. Such additives may include, but are not limited to, solvents, fillers, clays, blocking agents, stabilizers, thixotropes, plasticizers, compatibilizers, colorants, UV stabilizers, flame retardants, and the like.

In a particular embodiment, the one-component adhesive formulation of the invention comprises 100% solids, i.e., no solvent is present at the time of application. In another particular embodiment, the one-component adhesive formulation may be dissolved, dispersed, and/or emulsified in a solvent or water to reduce viscosity or otherwise to improve the applicability of the adhesive formulation.

In a particular embodiment, the adhesive formulation does not include any catalyst. In another particular embodiment, the one -component adhesive formulation comprises one or more catalysts to increase the reaction rate of free isocyanate and water.

In a particular embodiment, functional groups or molecules with functional groups may be included in the polyether carbonate polyol or in the prepolymer to enable the cross- linking/curing thereof. Examples of these functional groups include hydroethyl acrylate groups which introduce UV light curing properties. Fatty acid groups and/or molecules with unsaturation functionality enable the cross-linking via oxidation.

In a particular embodiment, the one-component adhesive formulation forms a final, cured polyurethane adhesive. In this particular embodiment, the cured polyurethane adhesive has a tensile strength ranging from 8 to 15 MPa, more preferably from 8 to 12 MPa, measured according to UNE-EN ISO 527-1.

Two-component adhesive formulation In another particular embodiment, the adhesive formulation of the invention is a two-component formulation comprising a first component and a second component, said first component comprises a polyether carbonate polyol as defined above and said second component comprises one or more di- or poly-isocyanates.

The first component comprises a polyether carbonate polyol which is obtained according to the process defined herein above using a double metal cyanide catalyst obtainable also as defined above.

In a particular embodiment, the polyether carbonate polyol contained in the first component has a functionality of at least two, preferably from two to eight. More preferably is a polyether carbonate diol or a polyether carbonate triol, even more preferably is a polyether carbonate triol.

In a particular embodiment, the number average molecular weight of the polyether carbonate polyol contained in the first component ranges from 500 to 20000 Da, preferably from 1000 to 12000 Da, more preferably from 1000 to 5000.

Preferably, said polyether carbonate polyol has from 5 to 35 wt% of carbon dioxide, more preferably from 12 to 25 wt%, based on the total weight of the polyether carbonate polyol.

In another particular embodiment, the polyether carbonate polyol is a triol having from 5 to 35 wt% of caron dioxide, still more preferably from 10 to 30 wt%, even more preferably from 12 to 25 wt%, and particularly preferable from 18 to 22 wt%, based on the total weight of the final polyether carbonate polyol.

In another particular embodiment, the polyether carbonate polyol is a diol having from 5 to 35 wt% of carbon dioxide, more preferably from 5 to 20 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 has from 5 to 35 wt% of carbon dioxide, more preferably from 10 to 35 wt%, even more preferably from 15 to 35 wt%, based on the total weight of the polyether carbonate polyol excluding the initiator and the alkylene oxide activation.

In another particular embodiment, the polyether carbonate polyol is a triol having from 10 to 35 wt% of carbon dioxide, more preferably from 15 to 35 wt%, and particularly preferable from 25 to 35 wt% or form 25 to 32 wt%, based on the total weight of the polyether carbonate polyol excluding the initiator and the alkylene oxide activation.

In another particular embodiment, the polyether carbonate polyol is a diol having from 5 to 35 wt% of carbon dioxide, even more preferably from 5 to 25 wt%, and particularly preferable from 8 to 22 wt % or from 15 to 22 wt%, based on the total weight of the polyether carbonate polyol excluding the initiator and the alkylene oxide activation.

In a particular embodiment, the second component comprises one or more di- or poly- isocyanates. Any of the above mentioned isocyanates can be included in the second component. In a preferred embodiment, said isocyanate is a di-isocyanate selected from aliphatic or aromatic di-isocyanates, more preferably is MDI or TDI.

The first component and/or the second component may include one or more additives. Such additives may include, but are not limited to, solvents, fillers, clays, blocking agents, stabilizers, thixotropes, plasticizers, compatibilizers, colorants, UV stabilizers, flame retardants, and the like.

In a particular embodiment, the two-component adhesive formulation of the invention comprises 100% solids, i.e., no solvent is present at the time of application. In another particular embodiment, the any of the two components of the adhesive formulation may be dissolved, dispersed, and/or emulsified in a solvent or water to reduce viscosity or otherwise to improve the applicability of the adhesive formulation.

In a particular embodiment, the two-component adhesive formulation does not include any catalyst. In another particular embodiment, at least one of the two components of the adhesive formulation comprises one or more catalysts to increase the reaction rate of free isocyanate and the polyether carbonate polyol.

In a particular embodiment, functional groups or molecules with functional groups may be included in the polyether carbonate polyol to enable the cross-linking/curing thereof. Examples of these functional groups include hydroethyl acrylate groups which introduce UV light curing properties. Fatty acid groups and/or molecules with unsaturation functionality enable the cross- linking via oxidation.

In a particular embodiment, the two components of the adhesive formulation are mixed at the time of application to form a final, cured polyurethane adhesive. In this particular embodiment, the cured polyurethane adhesive has a tensile strength ranging from 8 to 15 MPa, more preferably from 8 to 12 MPa, measured according to UNE-EN ISO 527-1.

Another aspect of the invention refers to a method of joining two substrates, said method comprising the step of applying an adhesive formulation as defined above, either a one- component adhesive formulation or a two-component adhesive formulation, to at least one of the substrates, arranging the substrates so that both substrates are in contact with the adhesive formulation, and curing the adhesive formulation. 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 (700 mol. wt triol)

Glycerin (130 g) was charged into the reactor, purged with N₂ and dehydrated at 130°C (until H₂0 < 500 ppm). Then, glycerin was stabilized at 50°C and the catalyst HBF₄ (2 g, 2000 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 50°C with N₂ 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 = 250±10 mg KOH/g; Humidity <500 ppm; Acidity <0.1 mg KOH/g; Viscosity <400 cps.

Example 3. Acidic catalysis synthesis of propoxylated glycol (400 mol. wt diol)

Monopropylene glycol (190 g) was charged into the reactor, purged with N₂ and dehydrated at 130°C (until H₂0 < 500 ppm). Then, it was stabilized at 50°C and the catalyst HBF4 (2 g, 2000 ppm) was added to the reactor. Propylene oxide feeding (810 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 50°C with N2 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 = 275±10 mg KOH/g; Humidity <500 ppm; Acidity <0.1 mg KOH/g; Viscosity <100 cps.

Example 4. Synthesis of polvether carbonate polvols (PCP).

General Procedure

A two-liter stainless steel reactor was charged with 160 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 N₂ stripping. After reaching the desired temperature, vacuum was continued for 30 min more. When the initiator was dried (H₂0< 100 ppm), the DMC catalyst (200 ppm) was added.

A first portion of propylene oxide 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 C0₂ and a waiting time was observed until activation occurred. Optionally, a third portion of propylene oxide was added in the absence of C0₂ and a waiting time was observed until activation occurred. Carbon dioxide was then introduced into the reactor until the desired pressure and a further portion of propylene oxide was added. After catalyst activation was observed, the remaining propylene oxide needed for a poly ether carbonate triol Mw 3000, was slowly and continuously pumped into the reactor. When the carbon dioxide pressure decreased a certain value, further CO₂ was admitted.

When co-feeding of propylene oxide and carbon dioxide was started, temperature was decreased to 90°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 N₂ stripping for 1 h at 90°C. The reactor was cooled and the product discharged.

In Table la, the reaction conditions employed and the results obtained in each example are shown.

The amount by weight (in wt%) of CO₂ incorporated in the resulting polyether carbonate polyol, and the ratio of propylene carbonate to polyether carbonate polyol, were determined by means of 'H-NMR (Broker AV III HD 500, 500 MHz, pulse program zg30, waiting time dl : Is, 120 scans). The sample was dissolved in deuterated chloroform. The relevant resonances in the ^lH- NMR (based on TMS=0 ppm) are as follows: Cyclic carbonate= 1.50 ppm (3H); Polyether carbonate polyol= 1.35-1.25 ppm (3H); Polyether polyol: 1.25-1.05 ppm (3H).

The amount by weight (in wt. %) of polymer bonded carbonate (CP) in the polyether carbonate polyol was calculated according to formula (I):

CP = F(1.35-1.25) x 102 x 100 / Np (I) wherein:

- F(1.35-1.25) is the resonance area at 1.35-1.25 ppm for polyether carbonate polyol (corresponds to 3 H atoms);

- the value for Np ("denominator" Np) was calculated according to formula (II):

Np = F(1.35-1.25) x 102 + F(1.25-1.05) x 58 (II) being F(1.25-1.05) the resonance area at 1.25-1.05 ppm for polyether polyol (corresponds to 3 H atoms).

The factor 102 results from the sum of the molar masses of C0₂ (molar mass 44 g/mol) and of propylene oxide (molar mass 58 g/mol) and the factor 58 results from the molar mass of propylene oxide.

The amount by weight (in wt. %) of C0₂ in polymer was calculated according to formula (III)

% CO₂ in polymer = CP x 44 / 102 (III).

The amount by weight (wt. %) of cyclic carbonate (CC) in the reaction mixture was calculated according to formula (IV) :

CC = F(1.50) x 102 x 100 / N (IV) wherein: - F(l .50) is the resonance area at 1.50 ppm for cyclic carbonate (corresponds to 3 H atoms);

- the value for N ("denominator" N) was calculated according to formula (V)

N = F(1.35-1.25) x 102 + F(1.50) x 102 + F(1.25-1.05) x 58 (V) Table la

Acidic initiator refers to the propoxylated glycerol obtained in Example 2 using HBF₄ catalysis.

a Calculated excluding the initiator and the propylene oxide activation

A similar procedure as described above was followed but substituting the triol initiator (propoxylated glycerol) with the diol initiator (propoxylated glycol) prepared in example 3. The results are shown in Table lb:

Table lb

Acidic initiator refers to the propoxylated glycol obtained in Example 3 using HBF4 catalysis ^aa Calculated excluding the initiator and the propylene oxide activation Example 5. Synthesis of polvurethane prepolymers

Polyurethane prepolymers were synthesized by reacting the polyether carbonate polyols obtained according to the procedure described in example 4 above with TDI 80/20 as isocyanate at a temperature of 80°C. A stoichiometric excess of 8% of the isocyanate was used to obtain prepolymers with manageable viscosity in the reactor.

For comparative purposes, polyurethane prepolymers were also prepared from polyether polyols (PP9, PP10 and PP14) where no carbonate groups are present.

In order to calculate the proportion of the reactants is necessary to know the following variables:

NCO percentage in the prepolymer to be synthesized;

molecular weight of isocyanate;

OH index (IOH) of the polyol and water content;

amount of polyol (given in grams)

By using the following formulas, the amount of isocyanate to be added in the reaction to form the prepolymer can be obtained:

OH (moles)/ polyol (grams) ^: IOH

56.1 x 1000

OH moles in the polyol = OH moles poiyd^^)

polyol(grams)

H₂0 moles = % de H₂0

18 - 100

=> moles of NCO necessary to react with water = 2 · moles of H₂0

=> moles of NCO necessary to react with polyol = OH moles in the polyol

=> stoichiometric NCO moles = NCO moles to react with water + NCO moles to react with polyol

=> Stoichiometric isocyanate (grams) = stoichiometric NCO (moles) ^■ Mwisocyanate

isocy anat e functionality

Now, the amount of TDI to be added in excess is calculated to obtain a prepolymer with the desired NCO percentage. This amount can be obtained by:

% NCO in excess = NCO in excess (grams) _ _{χ QQ}

total grams

% de NCO = NCO in excess (grams) _{l QQ}

TDI in excess (grams) + stoichiometric TDI (grams) + polyol(grams)

Since one molecule of TDI has two NCO groups, there are 84 g of NCO (2 x 42 g) per every 174,2 g of TDI (1 mol)

Then:

g TDI _cxccss = % NCO^■ (g polyol+ g TDI stoichiometric)

⁸⁴⁰⁰ - o/oNCO

174.2

The properties of the prepolymers are shown in Table Ila and Table lib below:

Calculated excluding the starter and the propylene oxide activation

Table lib

Calculated excluding the starter and the propylene oxide activation

The polyether carbonate polyols have a viscosity higher than polyether polyols, thus the prepolymers obtained from polyether carbonate polyols have higher viscosities. Additionally, an increase in the Tg with the content of CO₂ is also observed.

Example 6. Synthesis of cured polvurethane polymers

In order to assess the mechanical properties of the polyurethane polymer, cured samples were obtained. The samples were cured by humidity, i.e., the water present in the environment reacts with the excess of isocyanate present in the prepolymer to give ureas, thus curing the prepolymer.

A plurality of samples was obtained for each polymer in order to be used for the measurements of the different properties.

In particular, 38-40 g of prepolymer were placed in a plastic vessel and closed under N₂ atmosphere. Then, 18 g (1 mL) of dried toluene were added to the vessel and the mixture was stirred until a homogeneous mixture was obtained.

The vessel was covered with a glass and placed in an oven at 50°C for 15 minutes. Then, the vessel was extracted from the oven and left to cool for 15 minutes at room temperature.

The mixture was poured in a Petri plate and introduced in a desiccator provided with four glass tubes of toluene and one glass tube of water to assure the presence of some humidity in the desiccator, thus allowing the curing of the samples.

Once the desiccator is closed, vacuum was applied for 20 minutes to evaporate the toluene, and then the samples were left in the desiccator for 7 days. Once the samples were extracted from the desiccator and removed from the Petri plate, they were left at atmosphere conditions for 7 additional days to assure their complete curing before being subjected to the tests to measure their mechanical properties.

In particular, the following mechanical properties were measured:

- tensile strength (according to UNE-EN ISO 527- 1 );

elongation or extension percentage for bracking (according to UNE-EN ISO 527-1) shear stress (according to an internal procedure described below)

adhesion/peeling (according to ISO 11339-93)

The shear stress was measured using the polyurethane as a contact adhesive. The equipment used for measuring shear strength was a Dynamometer (INSTRON 5500 R4505 H1680). It was needed jagged grips for avoiding the samples to be slipped out. The grips were placed in the dynamometer allowing the longitudinal axe match with the stretching force through the grips coupling line.

Initial distance between grips was 70 mm

The pneumatic air pressure of the tweezers was 2,5 bar

The speed applied for the test was 75 mm/min

The load cell was 5000 N reference 1/02/004/F003

The specimens were built using aluminiun plates with the following dimensions: 25 mm x 75 mm x 2 mm.

The aluminium plates were prepared by first cleaning the surfaces where the prepolymer was to be applied with acetone and were let dry for 15 minutes. Then, the plates were placed in a climatic chamber with the following conditions: 70 % relative humidity and 50° C.

A prepolymer drop was added with a Pasteur pipette on the surface of one of the plates, having special care for not wetting the plate borders. The two plates were joined together as shown in Figure 1 so as a distance of 15 mm was left from one end. The prepolymer did not reach the borders of the plates.

The samples were placed in the climatic chamber for 7 days at 70 % relative humidity and

50° C.

Then, the maximum load, the shear stress and the type of failing were measured.

The type of failing produced between the two aluminium plates could be:

- adhesive failing: the separation is produced between the adhesive interface and the aluminium plate;

- cohesive failing: when the adhesive is separated;

- intermediate failing: the failing presents in some parts an adhesive failing and in some parts a cohesive failing (see figure 2).

The shear stress is calculated as the maximum load divided by the adhesive drop area after the assay:

maximum load (N)

Shear stress (kPa) =

adhesive drop area (m²)x 1000

Tables Ilia and Illb show the values of the mechanical properties for the different samples: Table Ilia

Calculated excluding the starter and the propylene oxide activation

Table Illb

Calculated excluding the starter and the propylene oxide activation

As can be seen from the experimental results, the tensile strength increases for those polyurethane polymers obtained from a polyether carbonate polyol. However, this increase is significantly higher in the case of polyurethanes obtained from polyether carbonate polyols having a higher percentage of carbonate linkages in the backbone of the polymer which are obtained following the procedure described in the present specification. It can also be seen a correlation between the Tg of the prepolymer and the polyol and the tensile strength of the cured sample.

Furthermore, an increase in the percentage of elongation was also observed in the samples of the invention having a higher content of C0₂.

Regarding the shear stress, in all cases the failing produced when taking off the aluminum plates was cohesive, i.e., it is related to the structure of the material but does not affect the surface to which the polymer is adhered. As can be seen, samples of the invention having a content of C0₂ higher thanl2 wt% provide the best results as higher load has to be applied to separate the aluminum plates.

Furthermore, the peeling tests have also revealed the improved adhesion properties of the samples of the invention.

These experimental results have also pointed out that, for example, when comparing a polyurethane 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 triol PCP3 having 23.8 wt% of C0₂ or diol PCP19 having 20.6 wt% of C0₂, the tensile strength was respectively improved up to 37% in the case of triols and up to 48.8% in the case of diols.

This improvement in the tensile strength is significantly higher than that observed for polyurethane formulations obtained from polyol ether carbonates that, having also high C0₂ content, have been prepared by other processes different from the one herein described. In document DEI 02010019504 (see Table 2), an increase of only 2% was observed for the same physical property (tensile strength) when comparing a polyurethane obtained from a polyol ether (without any carbonate group) with a polyurethane prepared from a polyol ether carbonate as described in said document having 24.3 wt%> of C0₂.

The same applies for the elongation property where, comparing the same samples, an increase of 26% has been observed for the polyurethane of the present invention in contrast to the results shown in DE102010019504 in which even a slight decrease of this property is observed. 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 obtained from it are different, even when the same or similar content of CO₂ is incorporated in the polymer structure.

Claims

1. A polyurethane adhesive formulation 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:

- 90-100% by weight of water; and

- 0-10% by weight of a 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,

to form a slurry.

2. The adhesive formulation according to claim 1, wherein the polyether carbonate polyol has a number average molecular weight from 500 to 20.000 Da.

3. The adhesive formulation according to anyone of claims 1 to 2, wherein the polyether carbonate polyol has from 12 to 25 wt%> of carbon dioxide, based on the total weight of the polyether carbonate polyol

4. The adhesive formulation according to anyone of claims 1 to 3, wherein the H-functional initiator substance is a polyhydric alcohol having a number average molecular weight from 100 to 4000 Da.

5. The adhesive formulation according to claim 4, wherein the polyhydric alcohol is a polyether diol or a polyether triol.

6. The adhesive formulation according to any one of claims 4 to 5, wherein the polyether polyol is poly(oxypropylene) diol or poly(oxypropylene) triol.

7. The adhesive formulation according to claim 6, wherein the poly(oxypropylene)diol or the poly(oxypropylene) triol has a number average molecular weight lower than 2000 Da.

8. The adhesive formulation according to anyone of claims 1 to 7, comprising a polyurethane prepolymer obtainable by reacting a polyether carbonate polyol as defined in any of claims 1 to 7 with one or more di- or poly-isocyanates.

9. The adhesive formulation according to claim 8, wherein the polyurethane prepolymer has a Tg from -25°C to -50°C when the polyether carbonate polyol used to prepare said prepolymer is a triol.

10. The adhesive formulation according to claim 8, wherein the polyurethane prepolymer has a Tg from -40°C to -50°C when the polyether carbonate polyol used to prepare said prepolymer is a diol.

11. The adhesive formulation according to anyone of claims 1 to 10, which further comprises one or more additives.

12. The adhesive formulation according to anyone of claims 1 to 11, wherein said formulation is a one -component formulation comprising a polyurethane prepolymer as defined in anyone of claims 9 to 10.

13. The adhesive formulation according to anyone of claims 1 to 11, wherein said formulation is a two-component formulation comprising a first component and a second component, said first component comprises a polyether carbonate polyol as defined in claims 1 to 8 and said second component comprises one or more di- or poly-isocyanates.

14. The adhesive formulation according to anyone of claims 1 to 13 which, once cured, has a tensile strength from 8 to 15 MPa, measured according to UNE-EN ISO 527-1.

15. A method of joining two substrates, said method comprising the step of applying an adhesive formulation as defined in anyone of claims 12 to 13 to at least one of the substrates, arranging the substrates so that both substrates are in contact with the adhesive formulation, and curing the adhesive formulation.