METHOD FOR THE PRODUCTION OF SILANE-TERMINATED POLYMERS

Description

[0001] The present invention relates to a process for the production of silane-terminated polymers that can be used in sealants, adhesives and coating materials and are stable for a long period of time.

[0002] The silane-terminated polymers are produced using known methods. One known process, for example, involves the reaction of polyols, especially hydroxyl-terminated polyethers, polyurethanes, or polyesters, as well as hydroxyl-functional polyacrylates, with isocyanatoalkylalkoxysilanes.

[0003] Another method involves reacting the above-mentioned polyols with di- or polyisocyanates, using the latter in excess, so that isocyanate-functional polymers are produced in this first reaction step, which are then reacted in a second reaction step with alkoxysilanes that have an alkyl-bound isocyanate-reactive group.

[0004] The reaction of hydroxyl-functional polymers with isocyanates is carried out in the presence of additional catalysts, since only in this way can sufficiently high reaction rates be achieved in the corresponding reaction step for the economical production of the alkoxysilane-terminated polymers.

[0005] The use of bismuth catalysts, as described, for example, in EP1535940, leads to catalytic activity and thus to the acceleration of the reaction of isocyanate silanes with the hydroxy-terminated polyol. However, even with relatively high amounts of catalyst, long reaction times are required to achieve complete conversion. Furthermore, high amounts of catalyst tend to lead to undesired side reactions during synthesis and reduce the storage stability of the final products.

[0006] US 9,932,437 B2 and US 8,809,479 B2 disclose a moisture-curing resin composition with a low volatile organic content. This is obtained by reacting a moisture-curing polymer with a hydrolyzable silyl group and a reactive modifier.

[0007] The object of the present invention is to provide a process for the production of a silane-terminated polymer that allows for rapid but complete conversion.

[0008] The problem is solved by the method according to the invention. Preferred embodiments are the subject of the dependent claims.

[0009] Surprisingly, it was found that the inventive process yielded a silane-terminated polymer of formula (I) or formula (VI) The catalyst mixture according to the invention can be produced very efficiently. It leads to a significant reduction in reaction time. The catalyst mixture according to the invention is considerably more effective than pure bismuth catalysts or catalyst mixtures with bismuth and zinc catalysts. This increases efficiency and significantly reduces energy consumption, which is of high economic and ecological importance. Interestingly, the cobalt catalyst in the catalyst mixture cannot be replaced by a zinc catalyst, as the latter is not able to accelerate the reaction sufficiently.

[0010] According to the invention, the silane-terminated polymer of formula (I) is produced by reacting a hydroxy-terminated organic polymer of formula (II) with at least one isocyanate of the general formula (III) (RO) 3-Si-(CH 2 ) n-N=C=O (III) or with a multifunctional isocyanate of the formula (IV) B-(N=C=O) m (IV) and subsequent reaction with an alkoxysilane of the formula (V) (RO) 3Si-(CH 2 ) p-D 1 (V). The reaction takes place in the presence of a catalyst mixture, which is explained below. In the compounds of the general formula I, A for a polyether backbone, x and y for natural numbers between 1 and 10, where y must be greater than or equal to x, n, n1 and n2 for 1 or 3, p, p1 and p2 for a natural number between 1 and 5, m for a natural number between 2 and 10, R, R1 and R2 for methyl or ethyl, B for a linear, branched or cyclic organic residue not containing any isocyanate-reactive groups, where m is greater than 1, D is selected from the group consisting of NH, NR3 and S, D1 is a isocyanate-reactive group selected from the group consisting of NH2, NHR3 and SH, and R3 is a linear, branched or cyclic hydrocarbon residue with 1 to 10 carbon atoms, which may optionally include one or more heteroatoms selected from the group consisting of oxygen, sulfur and nitrogen.

[0011] In the process according to the invention, one or two different isocyanates of general formula (III) can be used. If only one isocyanate is used, R1 and R2 in the silane-terminated polymer of formula (I) or formula (VI) are identical and correspond to R in general formula (III). If two different isocyanates of general formula (III) are used, R1 corresponds to the residue R of the first isocyanate of general formula (III) and R2 to the residue R of the second isocyanate of general formula (III). The same applies to n and p.

[0012] In one embodiment of the present invention, R1 and R2 as well as n1 and n2 are identical. Such polymers can be obtained very simply by using only one isocyanate of general formula (III) in the synthesis.

[0013] In another embodiment, R1 and R2, or n1 and n2, or R1, R2, n1, and n2 are different from one another. Such polymers are obtained by mixtures of different isocyanates of general formula (III). This mixture allows the reactivity of the silane-terminated polymers to be controlled. Pure trimethoxysilane-terminated polymers crosslink rapidly, while pure triethoxysilane-terminated polymers react slowly. The reactivity can be individually adjusted by using different mixing ratios.

[0014] The catalyst mixture contains a bismuth catalyst and a cobalt catalyst, wherein the content of the cobalt catalyst is at least 2 ppm based on the hydroxy-terminated organic polymer of formula (II).

[0015] In connection with the present invention, the catalyst content is given in ppm. The values ​​refer to the metals contained in the catalyst, i.e., mg of the metal per kg of the hydroxy-terminated organic polymer. The catalyst anions are not included in the determination of the content.

[0016] Within the context of the present invention, complete conversion means that at least 95 wt.%, preferably 98 wt.% of the OH groups of the polymer backbone have reacted with the isocyanate of general formula III or IV.

[0017] In one embodiment, the catalyst mixture contains no further catalyst, i.e., it consists of a bismuth and a cobalt catalyst.

[0018] Preferably, the bismuth catalyst content of the catalyst mixture is at least 10 ppm based on the hydroxy-terminated organic polymer of formula (II). It has been shown that a combination with at least 2 ppm of the cobalt catalyst and at least 10 ppm of the bismuth catalyst leads to very short reaction times. Preferably, the reaction time is reduced by 50%, particularly preferably by 65%. The production of the silane-terminated polymer can be carried out continuously or batchwise.

[0019] In one embodiment, the silane-terminated polymer relates to a linear polymer of the general formula IA. where R1, R2, n1, n2, and A have the same definition as above. R1 and R2, as well as n1 and n2, are identical when only one isocyanate of general formula (III) is used. When two different isocyanates of general formula (III) are used, R1 and R2, or n1 and n2, or R1, R2, n1, and n2 are different from each other, resulting in a statistical distribution of polymers with R1-AR1, R1-AR2, and R2-AR2. A preferred embodiment relates to the linear polymer of general formula IB. in the production of which only an isocyanate of the general formula (III) is used.

[0020] Linear silane-terminated polymers of formula (IB) are particularly preferred for sealants and coatings where higher elasticity is required, such as joint sealants, elastic adhesives, surface sealants, or in marine applications, for example, for caulking teak. Such linear polymers become softer and more elastic after curing, while the branched polymers described below become harder and less elastic due to their higher crosslinking density.

[0021] In a second embodiment, the silane-terminated polymer relates to a branched polymer of the general formula IC where R1, R2, n1, n2, and A have the same definition as above, and x and y are natural numbers between 2 and 10. The isocyanate content of formula III can be varied with respect to the OH groups. Depending on the desired number of free OH groups, preferably 90 mol% to 130 mol% of the isocyanate of formula III is used. Preferably, the silane-terminated polymer of formula IC is substantially free of free OH groups, i.e., y and x are substantially identical, and the difference of yx is therefore approximately 0. Branched silane-terminated polymers of formula IC are particularly preferred for adhesives, sealants, and coatings where a higher Shore A hardness and a higher crosslinking density are required, such as in high-modulus adhesives, surface sealants, or floor coatings.The catalyst mixture according to the invention has no negative impact on the storage stability of the adhesives, sealants, and coatings produced therefrom and therefore does not require complex removal from the polymer. To prevent discoloration after prolonged storage, a deactivator or a complexing agent can optionally be added.

[0022] The hydroxy-terminated organic polymer of the formula The compound preferably has a polyether backbone A containing alkylene oxide repeating units with 2 to 6 carbon atoms, wherein 2 and 3 carbon atoms, i.e., propylene oxide and ethylene oxide, are preferred, or combinations thereof. The hydroxy-terminated organic polymer can be a homopolymer or a copolymer of different polyether units.

[0023] The term "copolymers thereof" refers to polymers composed of two or more monomer units. Besides alternating copolymers and graft copolymers, the term also includes, in particular, block polymers consisting of longer sequences or blocks of each monomer, which may be linked together via linker bonds. Such copolymers may, for example, contain aromatic glycol chain extenders with a total number of carbon atoms of 6 to 16, and preferably 6 to 12. Examples of suitable glycol chain extenders are benzene glycol and xylylene glycols, which are mixtures of 1,4-di(hydroxymethyl)benzene and 1,2-di(hydroxymethyl)benzene. Benzene glycol is preferred and comprises, in particular, hydroquinone, i.e., the bis(beta-hydroxyethyl) ether also known as 1,4-di(2-hydroxyethoxy)benzene, and resorcinol.the bis(beta-hydroxyethyl) ether, also known as 1,3-di(2-hydroxyethyl)benzene, pyrocatechol, i.e. the bis(beta-hydroxyethyl) ether, also known as 1,2-di(2-hydroxyethyl)benzene, and combinations thereof.

[0024] The term hydroxy-terminated refers to polymers that have free hydroxyl groups at the end of their molecules. y is a natural number from 1 to 10. In a preferred embodiment, y = 1, which corresponds to an α,ω-dihydroxy-terminated organic polymer, i.e., a polymer with two terminal OH groups. If y is greater than 1, the hydroxy-terminated polyol has more than two terminal OH groups, i.e., it is a polyol whose OH groups are intended to react with the isocyanate of formula III. In the case of branched hydroxy-terminated polymers, the OH groups are preferably not attached directly to the polymer backbone, but rather to the ends of side chains of the polymer backbone. They can be obtained, for example, by reactions with polyols. Both linear and branched hydroxy-terminated organic polymers are known to those skilled in the art and are also commercially available.

[0025] Examples of possible hydroxy-terminated polymers with a polyether polymer backing are Acclaim®< 4200, Acclaim®< 6300, Acclaim®< 8200, Acclaim®< 12200 and Acclaim®< 18200 (or the corresponding type Acclaim®< xx00N) from Covestro AG; PREMINOL S 1004F, PREMINOL S 4013F, PREMINOL S 4318F, PREMINOL S 3011, PREMINOL 5001F, PREMINOL 7001K, PREMINOL 7012 from AGC; Rokopol LDB Delta 12000, Rokopol LDB 18000D, Rokopol LDB 12000D, ROKAmer PPG 4000, Rokopol LDB8000D from PCC Group; and Voranol 3008. Voranol 3010, Voranol 3022J, Voranol 3136, Voranol 4000LM, Voranol 4053, Voranol 8000LM from DOW.

[0026] Preferably, the hydroxy-terminated organic polymer is liquid at room temperature. This is defined as a viscosity at 20°C of 1 to 10⁶ mPa*s. This viscosity is optimal for handling the composition according to the invention, particularly in the production of sealant preparations.

[0027] Preferably, the hydroxy-terminated organic polymer has an average molecular weight of 1,000–50,000 g / mol, particularly 2,000–25,000 g / mol, as these polymers are optimal for handling, optionally with the addition of a plasticizer to improve processability. Suitable plasticizers are known to those skilled in the art. Preferred plasticizers include, for example, phenyl alkanesulfonic acid esters such as Mesamoll from Lanxess, cyclohexanoate plasticizers such as Elatur DINCD from Evonik, 1,2-cyclohexanedicarboxylic acid diisononyl esters such as Hexamoll DINCH from BASF, hydrocarbons such as Shellsol D100 from Shell, and diesters of dicarboxylic acids such as dioctyl sebacate, dioctyl adipate, or dioctylazalate. In this document, "molecular weight" refers to the molar mass (in grams per mole) of a molecule.The "mean molecular weight" refers to the number-average molecular weight Mn of a polydisperse mixture of oligomeric or polymeric molecules, which is usually determined by titration of the acid and OH numbers. Alternatively, it can also be determined using analytical methods such as GPC / MALDI. The OH number (hydroxyl number) is a measure of the hydroxyl group content in polymers and is a quantity known to those skilled in the art. The acid number is a measure of the acid group content in polymers and is a quantity known to those skilled in the art.

[0028] The hydroxy-terminated organic polymers of formula (II) used according to the invention can be commercially available compounds which may be diluted with a plasticizer or solvent for better handling.

[0029] In a preferred embodiment of the present invention, the reaction is carried out with an isocyanate selected from the group consisting of 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane, or mixtures thereof. As shown in the following examples, these two silanes can be reacted very effectively with the catalyst mixture of the present invention. In the case of the less reactive isocyanatopropyltriethoxysilane, the cobalt catalyst content is preferably more than 4 ppm, and particularly preferably more than 5 ppm, in order to obtain a very rapid reaction.

[0030] The cobalt catalyst is preferably selected from the group consisting of cobalt(II) hexafluoroacetylacetonate, cobalt(II) benzoate, cobalt(II) isopropoxide, cobalt(II) acetylacetonate or cobalt(II) 2,4-pentanedionate, cobalt(II) oxalate, cobalt(II) citrate, cobalt(II) hydroxide, cobalt(II) acetate, cobalt(II) stearate, bis(2,2,6,6-tetramethyl-3,5-heptanedionato)cobalt(II), cobalt(II) oleate, cobalt(II) 2-ethylhexanoate (commercially available as Octa-Soligen® < Cobalt 10 from Borchers), cobalt(II) naphthenate (commercially available as 6% Cobalt Nap-All® < from Borchers). Cobalt (II) neodecanoate (commercially available as Borchers ®< Deca Cobalt 10 from Borchers) and cobalt(II) resinate, with cobalt (II) neodecanoate being particularly preferred.

[0031] The bismuth catalyst is preferably selected from the group consisting of bismuth(III) isopropoxide, bismuth(III) tert-pentoxide, bismuth(III) oleate, bismuth(III) 2-ethylhexanoate (commercially available as Borchi® < Kat 320 from Borchers), bismuth(III) neodecanoate (commercially available as Borchi® < Kat 315 from Borchers) and bismuth(III) acetylacetanoate, wherein bismuth(III) neodecanoate is particularly preferred.

[0032] The catalyst mixture is preferably added in a total amount of 8 to 500 ppm, particularly preferably 8 to 100 ppm and most preferably 10 to 50 ppm.

[0033] The catalysts can either be stirred into a mixture and added to the reaction mixture before the reaction or mixed directly into the prepolymer. Preferably, the catalyst mixture is freshly prepared before use, as this achieves the best reactivity. It has also been found that the catalyst mixture is more soluble if the isocyanate is already present in the reactor when the catalyst mixture is added.

[0034] For colorless end products, a cobalt catalyst content of 2 to 5 ppm is preferred, as otherwise discoloration of the product may occur.

[0035] Linear silane-terminated polymers selected from the group consisting of are particularly preferred. where A represents a polymer backbone according to the definition above. It has been found that these linear silane-terminated polymers can be produced particularly efficiently using the catalyst mixture according to the invention.

[0036] The inventive process for producing the silane-terminated polymer of formula (VI) is carried out by reacting a hydroxy-terminated organic polymer of formula (II) with a multifunctional isocyanate of formula (IV) B-(N=C=O) m (IV), and subsequent reaction with an alkoxysilane of formula (V) (RO) 3 Si-(CH 2 ) p -D (V) in the presence of the catalyst mixture according to the invention.

[0037] As multifunctional isocyanates of formula (IV), isocyanates with two or more, preferably 2 to 10, isocyanate groups in the molecule are particularly suitable. The known aliphatic, cycloaliphatic, aromatic, oligomeric, and polymeric multifunctional isocyanates are suitable for this purpose, provided that they do not contain any groups reactive towards isocyanate, i.e., in particular, no free primary and / or secondary amino groups. An example of an aliphatic multifunctional isocyanate is hexamethylene diisocyanate (HDI); an example of a cycloaliphatic multifunctional isocyanate is 1-isocyanato-3-(isocyanatomethyl)-3,5,5-trimethylcyclohexane (IPDI).Examples of aromatic multifunctional isocyanates include: 2,4- and 2,6-diisocyanatotoluene and the corresponding technical isomer mixture (TDI); diphenylmethane diisocyanates, such as diphenylmethane 4,4'-diisocyanate, diphenylmethane 2,4'-diisocyanate, diphenylmethane 2,2'-diisocyanate, and the corresponding technical isomer mixtures (MDI). Also included are naphthalene 1,5-diisocyanate (NDI) and 4,4',4" triisocyanatotriphenylmethane. The reaction is preferably carried out at temperatures between 50°C and 150°C, particularly preferably between 60°C and 120°C, and preferably at atmospheric pressure.

[0038] The crosslinkable compositions produced according to the invention are ideally suited as sealants for joints, including vertical joints, and similar voids, e.g., in buildings, land vehicles, watercraft, and aircraft, or as adhesives, in particular for bonding substrates with different coefficients of thermal expansion, e.g., in vehicle construction, facade construction, or solar applications, or as sealing compounds, e.g., in window construction or the manufacture of display cases, as well as for the production of protective coatings or rubber-elastic molded bodies and for the insulation of electrical or electronic devices. The compositions according to the invention are particularly suitable as sealants for joints with potentially high movement absorption.

[0039] The usual water content of the air is sufficient for crosslinking the composition according to the invention. Crosslinking can be carried out at room temperature or, if desired, also at higher or lower temperatures, e.g., at -5 to 10°C or at 30 to 50°C. Crosslinking is preferably carried out at atmospheric pressure.

[0040] The silane-terminated polymers according to the invention can also be formulated as a two-component system. In this system, the second component contains water in addition to excipients, which, after mixing with the first component, significantly accelerates the deep curing process. Corresponding two-component systems are known to those skilled in the art and are described, for example, in EP2009063 or EP2535376, the contents of which are incorporated by reference.

[0041] The preparations according to the invention may contain further excipients and additives. These excipients and additives include, for example, further silane-terminated polymers, plasticizers, stabilizers, antioxidants, fillers, reactive diluents, drying agents, adhesion promoters and UV stabilizers, rheological auxiliaries, color pigments or color pastes, crosslinking catalysts, and / or, optionally, solvents in small quantities. Such excipients and additives are known to those skilled in the art. Examples Comparative examples 1 to 10 and examples according to the invention 11-20

[0042] 230 g (11.65 mmol, determined by titration of the OH number) of Acclaim Polyol 18200N are placed in a reaction flask and pre-dried for 30 min at 80°C and 1 mbar. The vacuum is broken with nitrogen. Within 2 minutes, 5.09 g (23.3 mmol) of 3-isocyanatopropyltrimethoxysilane 94% are slowly added dropwise at a stirring speed of 170 rpm. Two minutes after complete addition of the isocyanatopropyltrimethoxysilane, the catalyst mixture (see table) dissolved in diisononyl phthalate is added to the reaction mixture. The reaction progress was determined by FTIR based on the increase in absorbance at 1722 cm⁻¹ (C=O absorption of the product) and the decrease in absorbance at 2270 cm⁻¹ (NCO absorption of the reactant). TMS-NCO: 3-Isocyanatopropyltrimethoxysilane

[0043] Example Bi [ppm] Zn [ppm] Co [ppm] Reaction progress after 25 minutes Reaction progress after 60 minutes NCO-silane 1 16.42 - - Not complete Not complete TMS-NCO 2 27.01 - - Not complete Not complete TMS-NCO 3 31.65 - - Not complete Not complete TMS-NCO 4 42.46 - - Not complete Not complete TMS-NCO 5 56.47 - - Not complete complete TMS-NCO 6 24.9 2.6 - Not complete Complete TMS-NCO 7 - - 3.58 Not complete Not complete TMS-NCO 8 - - 5.71 Not complete Not complete TMS-NCO 9 - - 7.00 Not complete complete TMS-NCO 10 6.8 - 1.7 Not complete Not complete TMS-NCO 11 14.5 - 3.66 complete TMS-NCO 12 15.6 - 3.96 complete TMS-NCO 13 19.36 - 2.57 complete TMS-NCO 14 11.02 - 3.38 complete TMS-NCO 15 10.6 - 3.93 Complete TMS-NCO 16 10.91 - 4.89 complete TMS-NCO 17 20.36 - 3.47 Complete TMS-NCO 18 23.89 - 3.86 complete TMS-NCO 19 31.09 - 4.13 complete TMS-NCO 20 19.01 - 5.83 Complete TMS-NCO Comparative examples 21 to 26 and examples according to the invention 27-29

[0044] 230 g (11.65 mmol, determined by titration of the OH number) of Acclaim Polyol 18200N are placed in a reaction flask and pre-dried for 30 min at 80°C and 1 mbar. The vacuum is broken with nitrogen. Over 2 min, 6.13 g (23.3 mmol) of 3-isocyanatopropyltriethoxysilane 94% are slowly added dropwise at a stirring speed of 170 rpm. Two min after complete addition of the silane, the catalyst mixture (see table) dissolved in diisononyl phthalate is added to the reaction mixture. The reaction progress was determined by FTIR based on the increase in absorbance at 1722 cm⁻¹ (C=O absorption of the product) and the decrease in absorbance at 2270 cm⁻¹ (NCO absorption of the reactant). TES-NCO: 3-Isocyanatopropyltriethoxysilane

[0045] Example Bi [ppm] Zn [ppm] Co [ppm] Reaction progress after 25 minutes Reaction progress after 60 minutes NCO-silane 21 46.85 - - Not complete Not complete TES-NCO 22 65.97 - - Not complete complete TES-NCO 23 70.12 - - Not complete complete TES-NCO 24 - - 4.28 Not complete Not complete TES-NCO 25 - - 6.51 Not complete complete TES-NCO 26 8.86 Not complete complete TES-NCO 27 13.7 - 5.11 complete TES-NCO 28 12.03 - 4.48 complete TES-NCO 29 40.5 - 4.91 complete TES-NCO

Claims

1. A process for preparing a silane-terminated polymer of the formula (I) or (VI) by reacting a hydroxy-terminated organic polymer of the formula (II) with at least one isocyanate of the general formula (III)         (RO)3-Si-(CH2)n-N=C=O     (III) or with a polyfunctional isocyanate of the formula (IV)         B-(N=C=O)m     (IV) and subsequent reaction with an alkoxysilane of the formula (V)         (RO)3Si-(CH2)p-D1     (V) in the presence of a catalyst mixture, wherein A is a polyether backbone, x and y are natural numbers from 1 to 10, where y must be greater than or equal to x, n, n1 and n2 are 1 or 3, p, p1 and p2 are a natural number from 1 to 5, m is a natural number from 2 to 10, and R, R1 and R2 are methyl or ethyl, B is a linear, branched or cyclic organic radical which does not contain any isocyanate-reactive groups, and m is greater than 1, D is selected from the group consisting of NH, NR3 and S, D1 is a reactive group which reacts with the isocyanate group and is selected from the group consisting of NH2, NHR3 and SH, and R3 is a linear, branched or cyclic hydrocarbyl radical which has 1 to 10 carbon atoms and may optionally comprise one or more heteroatoms selected from the group consisting of oxygen, sulfur and nitrogen, characterized in that the catalyst mixture contains a bismuth catalyst and a cobalt catalyst, and where the content of the cobalt catalyst is at least 2 ppm based on the hydroxy-terminated organic polymer of the formula (II).

2. The process as claimed in claim 1, characterized in that the content of the bismuth catalyst is at least 10 ppm based on the hydroxy-terminated organic polymer of the formula (II).

3. The process as claimed in any of the preceding claims, characterized in that the silane-terminated polymer is a linear polymer of the general formula IA 4. The process as claimed in any of the preceding claims, characterized in that the silane-terminated polymer is a linear polymer of the general formula IB 5. The process as claimed in either of claims 3 and 4, wherein the linear silane-terminated polymers are selected from the group consisting of where A is a polyether backbone as defined above.

6. The process as claimed in claim 1 or 2, characterized in that the silane-terminated polymer is a branched polymer of the general formula (IC) where x and y each correspond to a natural number from 2 to 10.

7. The process as claimed in claim 6, characterized in that the silane-terminated polymer of the formula (IC) is essentially free of free hydroxyl groups.

8. The process as claimed in any of the preceding claims, characterized in that the reaction is effected with an isocyanate selected from the group consisting of 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane.

9. The process as claimed in any of the preceding claims, characterized in that the cobalt catalyst is selected from the group consisting of cobalt(II) hexafluoroacetylacetonate, cobalt(II) benzoate, cobalt(II) isopropoxide, cobalt(II) acetylacetonate, cobalt(II) oxalate, cobalt(II) citrate, cobalt(II) hydroxide, cobalt(II) acetate, cobalt(II)stearate, bis(2,2,6,6-tetramethyl-3,5-heptanedionato)cobalt(II), cobalt(II) oleate, cobalt (II) 2-ethylhexanoate, cobalt (II) naphthenate, cobalt (II) neodecanoate and cobalt(II) resinate.

10. The process as claimed in any of the preceding claims, characterized in that the bismuth catalyst is selected from the group consisting of bismuth(III) isopropoxide, bismuth(III) tert-pentoxide, bismuth(III) oleate, bismuth(III) 2-ethylhexanoate, bismuth(III) neodecanoate and bismuth(III) acetylacetanoate.

11. The process as claimed in any of the preceding claims, characterized in that the hydroxy-terminated organic polymer has an average molecular weight of 1000-40 000 g / mol, especially 2000-25 000 g / mol.

12. The process as claimed in any of the preceding claims, characterized in that the content of the cobalt catalyst is 2 to 5 ppm, based on the hydroxy-terminated organic polymer of the formula (II).