EP4208493A1 - Isocyanate-terminated prepolymers based on polyoxymethylene-polyoxyalkylene block copolymers, process for the preparation and use thereof - Google Patents

Abstract

The present invention relates to isocyanate-terminated prepolymers based on polyoxymethylene-polyoxyalkylene block copolymers, to a process for their preparation, and to the use of these isocyanate-terminated prepolymers as isocyanate components in 1- and 2-component systems for coatings, adhesives and sealants.

Description

Isocyanate-terminated prepolymers based on polyoxymethylene-polyoxyalkylene block copolymers, processes for their preparation and their use

The present invention relates to isocyanate-terminated prepolymers based on polyoxymethylene-polyoxyalkylene block copolymers and a process for their production. The present invention also relates to the use of these isocyanate-terminated prepolymers as an isocyanate component in 1- and 2-component systems for paints, adhesives and sealants.

Isocyanate-terminated prepolymers are used in many technical fields, in particular for bonding and coating substrates, and in sealants. Both moisture-curing 1-component systems and 2-component systems are used, with polyols and/or polyamines often being used as reactants for the isocyanate-terminated prepolymers.

In the field of moisture-curing adhesives, there is a need to provide more sustainable isocyanate-terminated prepolymers that do not require acid stabilization. In order to be suitable for use in the area of adhesives, the isocyanate-terminated prepolymers need increased adhesive strength and therefore high reactivity to atmospheric moisture. This is particularly important for the fastest possible, complete conversion of the free isocyanate groups in order to achieve the finished performance properties at an early stage. Nevertheless, the isocyanate-terminated prepolymer must have very good storage stability.

Various prepolymers for polyurethane synthesis are known from the prior art.

WO 2014/095679 discloses NCO-modified polyoxymethylene block copolymers and their use as prepolymers for producing flexible polyurethane foams and thermoplastic polyurethanes. The publication discloses that the viscosity of the prepolymer can be controlled in a targeted manner over the length of the polyoxymethylene blocks in relation to the additional oligomers. The reference is not concerned with the shelf life of the prepolymer.

In WO 2004/096746 A1, isocyanate-reactive diols with OH numbers of 685 and 868 mg KOH/g based on polyoxymethylene (POM) are described experimentally and it was generally stated in the document that these could be suitable for the production of prepolymers . However, a concrete composition or an embodiment was not described. The international application with the file number PCT/EP2019/057066, which was not yet published at the time the present invention was filed, describes a process for producing a prepolymer for the production of a polyurethane integral foam, the composition for producing the prepolymer containing an acid, and the prepolymer obtained by the process and a polyurethane integral foam based on the prepolymer.

DE-A 10 237 649 describes an 1C polyurethane adhesive which contains at least one polyisocyanate prepolymer and at least one aminopolyetherpolyol, the molar ratio of ether groups to amine nitrogen in the aminoetherpolyol being 7 to 30. The proportion of aminopolyetherpolyols in the adhesive according to the invention is very low and is only 0.2 to 4.0% by weight. With dimorpholinodiethyl ether catalysis, this small proportion already halves the pressing time when gluing beech wood. However, the open time (i.e. the processing time) is clearly negatively influenced even by this small amount of aminopolyether.

WO 2009/000405 A1 describes moisture-curing adhesives based on isocyanate prepolymers which are obtainable from the reaction of special polyisocyanate mixtures based on 2,2'-, 2,4'- and 4,4'-MDI with amino-free and amino-containing polyethers. The adhesives have a good shelf life, a very fast film formation and short film drying time, and very good initial and final strength.

The object of the present invention was to provide 1- and 2-component paint, adhesive and sealant systems which dry more quickly than known systems of the prior art. The adhesive systems should also have improved adhesion compared to the known systems with a faster film formation time and shorter film drying time, higher initial strength after a short tack time and higher final strength after the shortest possible curing time, and a long shelf life comparable to the known systems.

It has surprisingly been found that paint, adhesive and sealant systems based on special isocyanate-terminated prepolymers which contain polyoxymethylene-polyoxyalkylene block copolymers as structural components have these properties.

An object of the present invention is therefore a process for the preparation of isocyanate-terminated prepolymers for use as an isocyanate component in 1- and 2-component paint, adhesive and sealant systems, comprising or consisting of the implementation of A. at least one aliphatic, cycloaliphatic, araliphatic and/or aromatic polyisocyanate, component A having an NCO content according to DIN EN ISO 11909:2007-05 of 15 to 60% by weight, preferably 15 to 50% by weight, in particular preferably 15 to 45% by weight,

B. at least one polyoxymethylene-polyoxyalkylene block copolymer with a hydroxyl number according to DIN 53240-2:2007-11 of 15 mg KOH/g to 200 mg KOH/g,

C. i) at least one polyether containing amino groups and based on propylene oxide with a hydroxyl number according to DIN 53240-2:2007-11 of 40 to 80 mg KOH/g, an OH functionality of 4.0 and an amine content according to DIN EN 9702:1998 in the range from 0.5 to 1.0% by weight, ii) optionally at least one amino-containing polyether based on ethylene oxide, propylene oxide or a mixture of ethylene oxide and propylene oxide with an NH2 functionality of 2 or 3, excluding amino-containing polyethers of the component Ci,

D. optional auxiliaries containing protic acids (D2) and/or auxiliaries which are not protic acids according to D2 (D1).

The isocyanate-terminated prepolymers according to the invention based on polyoxymethylene-polyoxyalkylene block copolymers are more economical than isocyanate prepolymers built up from standard building blocks in PU applications. Furthermore, their so-called carbon footprint is smaller, so that more environmentally friendly components can be made available for the PU market.

A long shelf life is understood to mean that the dynamic viscosity of the isocyanate-terminated prepolymer increases by no more than 55% after storage for six months at 25° C. under a protective gas atmosphere. These storage conditions were simulated by storing a sample at 70°C over a period of 14 days under a nitrogen atmosphere. In addition, the NCO content of the isocyanate-terminated prepolymer should not drop by more than 10% during storage under the above conditions, so that the reactivity of the isocyanate-terminated prepolymer is sufficiently high even after storage to ensure good adhesive strength guarantee.

Starting compounds A for the process according to the invention are any polyisocyanates having aliphatically, cycloaliphatically, araliphatically and/or aromatically bound isocyanate groups. The polyisocyanates have an isocyanate functionality >2.

Suitable polyisocyanates A are any, in various ways, for example by phosgenation in the liquid or gas phase or in a phosgene-free way, such as. B. by thermal urethane cleavage, accessible diisocyanates. Preferred diisocyanates are those with a molecular weight in the range from 140 to 400 with aliphatic, cycloaliphatic, araliphatic and/or aromatically bound isocyanate groups, such as. B. 1,4-diisocyanatobutane, 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI), 2-methyl-1,5-diisocyanatopentane, 1,5-diisocyanato-2,2-dimethylpentane, 2, 2,4- or 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3- and 1,4-diisocyanatocyclohexane, 1,3- and 1,4-bis- (isocyanatomethyl)cyclohexane, l-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 4,4'-

Diisocyanatodicyclohexylmethane, 1-Isocyanato-1-methyl-4(3)isocyanatomethylcyclohexane, bis(isocyanatomethyl)norbornane, 1,3- and 1,4-bis(2-isocyanatoprop-2-yl)benzene (TMXDI), 1,5-diisocyanatonaphthalene (NDI), norbornane diisocyanate (NBDI), 2,4- and 2,6-diisocyanatotoluene (TDI), as well as 2,2'-, 2,4'- and 4,4'- Diisocyanatodiphenylmethane (MDI). Furthermore can

poly(methylene phenyl isocyanate) (pMDI, polymeric MDI, crude MDI) can be used. The polyisocyanates mentioned can also be used as a mixture with one another.

Suitable polyisocyanates A are also any polyisocyanates with a uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrione structure prepared by modifying simple aliphatic, cycloaliphatic, araliphatic and/or aromatic diisocyanates, for example those of the type mentioned above, as for example in J. Prakt. Chem. 336 (1994) 185-200, in DE-A 1 670 666, DE-A 1 954 093, DE-A 2 414 413, DE-A 2 452 532, DE-A 2 641 380, DE-A 3 700 209, DE-A 3 900 053 and DE-A 3 928 503 or in EP-A 0 336 205, EP-A 0 339 396 and EP-A 0 798 299 or any mixtures of such polyisocyanates.

In the production of these polyisocyanates, the actual modification reaction is generally followed by a further process step for separating off the unreacted excess monomeric diisocyanates. This removal of monomers is carried out by methods known per se, preferably by thin-layer distillation in vacuo or by extraction with suitable solvents which are inert towards isocyanate groups, for example aliphatic or cycloaliphatic hydrocarbons such as pentane, hexane, heptane, cyclopentane or cyclohexane. In the process according to the invention, preference is given to using modified polyisocyanates of the type mentioned which have a content of monomeric diisocyanates of less than 1% by weight, preferably less than 0.5% by weight, particularly preferably less than 0.3% by weight. % exhibit.

Preferred polyisocyanates A for the process according to the invention are the abovementioned polyisocyanates containing exclusively aromatic isocyanate groups.

Particularly preferred are aromatic polyisocyanates such as 1,5-naphthalene diisocyanate (NDI), diisocyanatodiphenylmethane (2,2'-, 2,4'- and 4,4'-MDI), especially 2,4'- and 4,4'- '-Isomers and technical mixtures of these two isomers or technical mixtures of the three MDI isomers, Poly(methylene phenyl isocyanate) (pMDI, polymeric MDI, crude MDI), diisocyanatomethylbenzene (2,4- and 2,6-tolylene diisocyanate, TDI), especially the 2,4- and the 2,6-isomer and technical mixtures of the two isomers.

A very particularly suitable aromatic polyisocyanate is 2,4-tolylene diisocyanate and its technical mixture of 70 to 90% 2,4-tolylene diisocyanate and 30 to 10% 2,6-tolylene diisocyanate.

Also very particularly suitable is a polyisocyanate mixture based on diphenylmethane diisocyanate with a proportion of 4,4'-isomers of <50%, preferably <48%, particularly preferably <46% and very particularly preferably <44%; a proportion of 2,4'-isomers ranging from 10 to 15%, more preferably 11 to 14% and most preferably 11.5 to 13.5%; and a proportion of 2,2'-isomers ranging from 0.1 to 5%, preferably from 1 to 4% and most preferably from 1.5 to 3.5%; an isocyanate content between 30 and 33% by weight, particularly preferably 31 and 32% by weight; and an average functionality >2.0, preferably >2.2, more preferably >2.4 and most preferably >2.5.

The composition for preparing the isocyanate-terminated prepolymer preferably contains 50% by weight to 70% by weight of component A, based on the sum of all components in the composition.

Component B to be used in the process according to the invention is a polyoxymethylene-polyoxyalkylene block copolymer with a hydroxyl number according to DIN 53240-2 (November 2007) from 15 mg KOH/g to 200 mg KOH/g, preferably from 30 mg KOH/g to 150 mg KOH/g, more preferably from 40 mg KOH/g to 100 mg KOH/g. The composition for preparing the isocyanate-terminated prepolymer preferably contains 15% by weight to 30% by weight of component B, based on the sum of all components in the composition. Polyoxymethylene-polyoxyalkylene block copolymers in the context of the invention refer to polymeric compounds which contain at least one polyoxymethylene block and at least one additional polyoxyalkylene or polyoxyalkylene carbonate block and preferably do not exceed a four-digit molecular weight.

Component B is preferably prepared by catalytic addition of alkylene oxides and optionally other comonomers onto at least one polymeric formaldehyde starter compound which has at least one terminal hydroxyl group in the presence of a double metal cyanide (DMC) catalyst, with

(i) in a first step, the DMC catalyst in the presence of the polymeric formaldehyde

Starter compound is activated at an activation temperature (Tact) of 20 to 120 ° C, wherein to activate the DMC catalyst, a portion (based on the total amount of alkylene oxides used in the activation and polymerization) of one or more alkylene oxides is added (“activation”),

(ii) in a second step, one or more alkylene oxides and optionally further comonomers are added to the mixture resulting from step (i), the alkylene oxides used in step (ii) being different from the alkylene oxides used in step (i) ("polymerization "),

Suitable polymeric formaldehyde starter compounds are in principle those oligomeric and polymeric forms of formaldehyde which have at least one terminal hydroxyl group for reaction with the alkylene oxides and any other comonomers. The term “terminal hydroxyl group” is understood to mean, in particular, a terminal hemiacetal functionality which results as a structural feature from the polymerization of the formaldehyde. For example, the starter compounds can be oligomers and polymers of formaldehyde of the general formula HO(CH2O)n-H, where n is an integer >2 and where polymeric formaldehyde typically has n>8 repeating units.

Preferred polymeric formaldehyde starter compounds generally have molar masses of 62 to 30,000 g/mol, preferably 62 to 12,000 g/mol, particularly preferably 242 to 6000 g/mol and very particularly preferably 242 to 3000 g/mol and include 2 to 1000, preferably from 2 to 400, more preferably from 8 to 200 and most preferably from 8 to 100 repeating oxymethylene units. The starter compounds used typically have a functionality (F) of 1 to 3, but in certain cases they can also have a higher functionality, ie have a functionality>3. Preference is given to using open-chain polymeric formaldehyde starter compounds with terminal hydroxyl groups which have a functionality of 1 to 10, preferably 1 to 5, particularly preferably 2 to 3. Linear polymeric formaldehyde starter compounds which have a functionality of 2 are very particularly preferably used. The functionality F corresponds to the number of OH end groups per molecule.

The preparation of the polymeric formaldehyde starter compounds, which are used for the process for preparing component B, can be carried out by known processes (cf., for example, M. Haubs et al., 2012, Polyoxymethylene, Ullmann's Encyclopedia of Industrial Chemistry; G. Reus et al., 2012, Formaldehydes, ibid). In principle, the formaldehyde starter compounds can also be used in the form of a copolymer, in which case, in addition to formaldehyde, 1,4-dioxane or 1,3-dioxolane, for example, are copolymerized as comonomers. Other suitable formaldehyde copolymers are copolymers of formaldehyde and trioxane with cyclic and / or linear formals such as for example butanediol formal, or epoxides. It is also conceivable that higher homologous aldehydes, such as acetaldehyde, propionaldehyde, etc., are incorporated into the formaldehyde polymer as comonomers. It is also conceivable that formaldehyde starter compounds are in turn produced starting from H-functional starter compounds, in particular polymeric formaldehyde starter compounds with a hydroxyl end group functionality F>2 can be obtained here through the use of polyfunctional starter compounds (cf., for example, WO 1981001712 A1 , Bull. Chem. Soc. J., 1994, 67, 2560-2566, US 3436375, JP 03263454, JP 2928823).

Mixtures of different polymeric formaldehyde starter compounds or mixtures with other H-functional starter compounds can also be used for the process for preparing component B. As a suitable H-functional starter substance ("starter"), compounds with active H atoms for the alkoxylation can be used which have a molar mass of 18 to 4500 g/mol, preferably 62 to 2500 g/mol and particularly preferably 62 up to 1000 g/mol. Groups with active H atoms which are active for the alkoxylation are, for example, -OH, -NH2 (primary amines), -NH- (secondary amines), -SH and -CO2H, -OH and -NH2 are preferred, and -OH is particularly preferred. As an H-functional starter substance, for example, one or more compounds are selected from the group consisting of monohydric or polyhydric alcohols, polyhydric amines, polyhydric thiols, amino alcohols, thioalcohols, hydroxy esters, polyether polyols, polyester polyols, polyester ether polyols, polyether carbonate polyols, polycarbonate polyols, polycarbonates, polyethylene imines, polyether amines , polytetrahydrofurans (e.g. PolyTHF® from BASF), polytetrahydrofuranamines, polyetherthiols, polyacrylate polyols, castor oil, the mono- or diglyceride of ricinoleic acid, monoglycerides of fatty acids, chemically modified mono-, di- and/or triglycerides of fatty acids, and C1- C24 alkyl fatty acid esters containing an average of at least 2 OH groups per molecule are used.

It is known that formaldehyde polymerizes even in the presence of small traces of water. Depending on the concentration and temperature of the solution, a mixture of oligomers and polymers of different chain lengths is formed in an aqueous solution, which is in equilibrium with molecular formaldehyde and formaldehyde hydrate. So-called paraformaldehyde precipitates out of the solution as a white, poorly soluble solid and is usually a mixture of linear formaldehyde polymers with n=8 to 100 oxymethylene repeat units.

In one embodiment, polymeric formaldehyde or so-called paraformaldehyde, which is commercially available and inexpensive, is used directly as the starter compound. In particular, polyoxymethylene blocks with a defined molecular weight and functionality can be introduced into the product via the molecular weight and the end group functionality of the polymeric formaldehyde starter compound. Advantageously, the length of the polyoxymethylene block can be controlled simply via the molecular weight of the formaldehyde starter compound used in the process for preparing component B. Preference is given here to linear formaldehyde starter compounds of the general formula HO-(CH2O)nH, where n is an integer >2, preferably with n=2 to 1000, particularly preferably with n=2 to 400 and very particularly preferably with n= 8 to 100, used with two terminal hydroxyl groups. In particular, mixtures of polymeric formaldehyde compounds of the formula HO—(CH 2 O) n H, each with different values for n, can also be used as the starter compound. In a preferred embodiment, the mixtures of polymeric formaldehyde starter compounds of the formula HO-(CH2O)nH used contain at least 1% by weight, preferably at least 5% by weight and particularly preferably at least 10% by weight of polymeric formaldehyde compounds with n > 20

In particular, the process for preparing component B can be used to obtain polyoxymethylene block copolymers which have an A-B-A block structure comprising an inner polyoxymethylene block (B) and outer oligomeric blocks (A). It is also possible that formaldehyde starter compounds with a hydroxyl end group functionality F> 2 are used, which consequently homologous block structures B (-A) y with a number y> 2 of outer oligomeric blocks (A), which consist accordingly results from the functionality of the formaldehyde starter compound used. It is also fundamentally possible for formaldehyde starter compounds with a functionality F<2 to be used; these can also be, for example, linear formaldehyde starter compounds with F=1, which are substituted at one chain end with a protective group or by other chemical radicals.

Component B preferably consists of a polyoxymethylene-polypropylene oxide block copolymer or a polyoxymethylene-polyoxyalkylene carbonate block copolymer, the block copolymer preferably having two terminal polyoxyalkylene blocks.

The outer oligomeric blocks (A) are preferably polyoxyalkylene or polyoxyalkylene carbonate blocks, with polyoxyalkylene or polyoxyalkylene carbonate blocks in the context of the invention also being understood as meaning blocks into which (small) proportions of other comonomers, generally less than 50 mol -%, preferably less than 25 mol%, based on the total amount of all repeating units present in the oligomeric block, are copolymerized.

A ^{polyoxyalkylene} carbonate block in the context of the invention designates a polymeric structural ^unit O[( _C2R1R2R3R4O ^{) x} ( ^CO2 ) ^{( C2R1R2R3R4O} _{) y} ] ^z- , with x > 1, y > 0 and z > 1, where R ¹ , R ² , R ³ and R ⁴ independently of one another are hydrogen, an optionally additional heteroatom such as nitrogen, Oxygen, silicon, sulfur or phosphorus-containing alkyl or aryl radical and can differ in different repeating units. In the context of the entire invention, the term "alkyl" generally includes substituents from the group n-alkyl such as methyl, ethyl or propyl, branched alkyl and/or cycloalkyl. In the context of the entire invention, the term "aryl" generally includes substituents from the group consisting of mononuclear carbo- or heteroaryl substituents such as phenyl and/or polynuclear carbo- or heteroaryl substituents, which may be substituted with other alkyl groups and/or heteroatoms such as nitrogen, oxygen, silicon, sulfur or Phosphorus can be substituted. The radicals R ¹ , R ² , R ³ and R ⁴ can be linked to one another within a repeating unit in such a way that they form cyclic structures, such as a cycloalkyl radical which is incorporated into the polymer chain via two adjacent carbon atoms.

The DMC catalyst is preferably activated in the presence of the polymeric formaldehyde starter compound. The starter compound and the DMC catalyst can optionally be suspended in a suspension medium. It is also possible to use a further liquid starter compound (“costarter”) in a mixture, with the DMC catalyst and the polymeric formaldehyde starter compound being suspended in this.

According to the invention, the DMC catalyst is activated at an activation temperature Tact in the range from 20 to 120.degree. C., preferably at 30 to 120.degree. C., particularly preferably at 40 to 100.degree. C. and very particularly preferably at 60 to 100.degree.

"Activation" of the DMC catalyst is understood to mean a step in which a portion of alkylene oxide is added to the DMC catalyst suspension at the specific activation temperature and then the addition of the alkylene oxide is interrupted, with heat being generated due to a subsequent exothermic chemical reaction, which can lead to a temperature peak ("hotspot"), and a pressure drop in the reactor is observed due to the conversion of alkylene oxide.

DMC catalysts suitable for the process for preparing component B for use in the homopolymerization of alkylene oxides are known in principle from the prior art (see, for example, US-A 3,404,109, US-A 3,829,505, US-A 3,941 849 and US-A 5,158,922). DMC catalysts, which are described, for example, in US Pat very high activity in the polymerization of alkylene oxides and, where appropriate, the copolymerization of alkylene oxides with suitable comonomers and enable the production of polyoxymethylene copolymers at very low catalyst concentrations, so that the catalyst can be separated from the finished product ia is no longer required. A typical example are the highly active DMC catalysts described in EP-A 700 949 which, in addition to a double metal cyanide compound (e.g

Zinc hexacyanocobaltate(III)) and an organic complex ligand (e.g. tert-butanol) also contain a polyether with a number-average molecular weight greater than 500 g/mol. For the synthesis of components A1, preference is given to using DMC catalysts which have been prepared with the addition of a base, preferably KOH. Such a particularly preferred DMC catalyst is one according to Example 6 of WO 01/80994 A1. A DMC catalyst containing zinc hexacyanocobaltate, tert-butanol and polypropylene glycol with a number-average molecular weight of about 1000 g/mol is preferably used for the synthesis of component B.

The concentration of DMC catalyst used is typically 10 to 10000 ppm, particularly preferably 20 to 5000 ppm and most preferably 50 to 2000 ppm, based on the mass of the polyoxymethylene block copolymer to be prepared. Depending on the requirement profile of the downstream application, the DMC catalyst can be left in the product or (partially) separated. The (partial) removal of the DMC catalyst can be carried out, for example, by treatment with adsorbents and/or filtration. Processes for removing DMC catalysts are described, for example, in US-A 4,987,271, DE-A 3132258, EP-A 0406440, US-A 5,391,722, US-A 5,099,075, US-A 4,721,818, US-A 4,877,906 and EP-A 0 385 619. According to the invention, component B and optionally also component C preferably contain a residual content of DMC catalyst(s), so that component B and component C together contain a content of DMC catalyst(s) of 10 to 5000 ppm, preferably from 10 to 3,000 ppm, each based on the total amount of components B and C.

In a preferred embodiment of the process according to the invention, at least component B was prepared in the presence of a double metal cyanide catalyst and component B still contains this double metal cyanide catalyst at least in part, the content of double metal cyanide catalyst based on the total amount of components B and C being 10 to 5000 ppm, preferably 10 to 3000, particularly preferably 10 to 2500 ppm, and the double metal cyanide catalyst content is determined using the amount of metal content from the double metal cyanide catalyst determined according to DIN-ISO 17025 (August 2005). The amount of metal content from the DMC catalyst can be determined either for component B and C in total or alternatively for each of the two components separately. The amount of catalyst can then be calculated using the information on the metal content from the DMC catalyst and the molecular weight of the DMC catalyst. It should be noted that double metal cyanide catalysts can contain different metals in different amounts. Compounds of the general formula (I) are preferred as the epoxide (alkylene oxide) for the preparation of the polyoxymethylene-polyoxyalkylene block copolymers: used, where R ¹ , R ² , R ³ and R ⁴ are independently hydrogen or an optionally additional heteroatoms such as nitrogen, oxygen, silicon, sulfur or phosphorus-containing alkyl or aryl radical and can optionally be linked together so that they form cyclic structures, such as a cycloalkylene oxide.

Preference is given to using those alkylene oxides which are suitable for the polymerization in the presence of a DMC catalyst. If different alkylene oxides are used, they can be metered in either as a mixture or one after the other. In the case of the latter method of dosing, the polyether chains of the polyoxymethylene-polyoxyalkylene block copolymer obtained in this way can in turn also have a block structure.

In general, alkylene oxides (epoxides) having 2-24 carbon atoms can be used. The alkylene oxides having 2-24 carbon atoms are, for example, one or more compounds selected from the group consisting of ethylene oxide, propylene oxide, 1-butene oxide, 2,3-butene oxide, 2-methyl-1,2-propene oxide (isobutene oxide), 1-pentene oxide, 2,3-pentene oxide, 2-methyl-1,2-butene oxide, 3-methyl-1,2-butene oxide, 1-hexene oxide, 2,3-hexene oxide, 3,4-hexene oxide, 2-methyl- l,2-pentene oxide, 4-methyl-l,2-pentene oxide, 2-ethyl-l,2-butene oxide, 1-heptene oxide, 1-octene oxide, 1-nonene oxide, 1-decene oxide, 1-undecene oxide, 1-dodecene oxide, 4-Methyl-1,2-pentene oxide, butadiene monoxide, isoprene monoxide, cyclopentene oxide, cyclohexene oxide, cycloheptene oxide, cyclooctene oxide, styrene oxide, methyl styrene oxide, pinene oxide, mono- or polyepoxidized fats as mono-, di- and triglycerides, epoxidized fatty acids, Cl-C24- Esters of epoxidized fatty acids, epichlorohydrin, glycidol and derivatives of glycidol such as methyl glycidyl ether, ethyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, glycidyl ethacrylate and epoxy-functional alkoxysilanes such as 3-glycidyloxy->propyl->trimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyltripropoxysilane, 3-glycidyloxy->propylmethyldimethoxysilane, 3-glycidyloxypropylethyldiethoxysilane, 3-glycidyloxypropyltriisopropoxysilane . The epoxide of the general formula (I) is preferably a terminal epoxide, where R ¹ , R ² and R ³ are hydrogen, and R ⁴ is hydrogen, an alkyl or optionally containing additional heteroatoms such as nitrogen, oxygen, silicon, sulfur or phosphorus aryl radical and can be in can distinguish different repeat units. The alkylene oxides used are preferably ethylene oxide and/or propylene oxide, in particular propylene oxide.

The process according to the invention is preferably carried out in such a way that the activation of the catalyst (step i) is followed by a polymerization step (ii) with metering in of one or more alkylene oxides.

In a further embodiment of the process according to the invention, the polymerization of the alkylene oxides in step ii) takes place in the presence of a further comonomer. As further comonomers, for example, all oxygen-containing cyclic compounds, in particular cyclic ethers such as oxetane, THF, dioxane or cyclic acetals such as 1,3-dioxolane or 1,3-dioxepane, cyclic esters such as y-butyrolactone, y-valerolactone, e-caprolactone, or cyclic acid anhydrides such as maleic anhydride, glutaric anhydride or phthalic anhydride and carbon dioxide are used. Carbon dioxide is preferably used as comonomer.

Further comonomers can be metered in as a pure substance, in solution or as a mixture with one or more alkylene oxides. Further comonomers can also be metered in parallel to metering in or after metering in of the alkylene oxides.

In a preferred embodiment of the process according to the invention, in addition to the addition of the alkylene oxide(s) onto the polymeric formaldehyde starter compound, carbon dioxide (CO2) is also added as a further comonomer. This can be used to produce polyoxymethylene-polyoxyalkylene carbonate copolymers. Compared to existing products (e.g. polyether polyols in the polyurethane sector or polyoxymethylene (co)polymers in the POM sector), these also contain CO2 as a cost-effective and environmentally friendly comonomer. Since CO2 is, among other things, a waste product of energy generation from fossil raw materials and is fed back into chemical recycling here, the incorporation of CO2 into the polymer structures results in both economic and ecological advantages (favorable CO2 balance of the product polymers, etc.).

For the purposes of the invention, polyoxymethylene-polyoxyalkylene carbonate block copolymers refer to polymeric compounds which contain at least one polyoxymethylene block and at least one polyoxyalkylene carbonate block. Polyoxymethylene-polyoxyalkylene carbonate block copolymers are of particular interest as starting materials in the polyurethane sector and for applications in the polyoxymethylene (POM) sector. By changing the CO2 content, the physical properties can be adapted to the respective application, which opens up new areas of application for these block copolymers. In particular, the process according to the invention can be used to provide polyoxymethylene-polyoxyalkylene carbonate copolymers a high content of incorporated CO2 is achieved, the products have a comparatively low polydispersity and contain very few by-products and decomposition products of the polymeric formaldehyde.

Component C includes the component Ci and the optional component Cii.

Component Ci comprises at least one polyether containing amino groups and based on propylene oxide with an OH number in the range from 40 to 80 mg KOH/g, preferably 45 to 75 and particularly preferably 50 to 70, an OH functionality of 4.0 and an amine content im Range of 0.50 to 1.00, preferably 0.56 to 0.94 and most preferably 0.62 to 0.88% by weight. As starter molecules for the starting compounds Ci, for example, diamines such. B. ethylenediamine, hexamethylenediamine, isophoronediamine, toluenediamine and 4,4'-diaminodicyclohexylmethane into consideration. The composition for producing the isocyanate-terminated prepolymer preferably contains 10% by weight to 30% by weight of component Ci, based on the sum of all components in the composition.

Component Cii comprises at least one polyether containing amino groups based on ethylene oxide, propylene oxide or a mixture of ethylene oxide and propylene oxide with an NH2 functionality of 2 or 3, with the exception of polyethers containing amino groups of component Ci. The polyethers of component Cii containing amino groups preferably have no OH functions (OH functionality=0).

Preferred polyethers containing amino groups of this type correspond to the following general formulas and wherein x is a number from 0 to 10, y is a number from 0 to 40 and z is a number from 0 to 10, EO is ethylene oxide and PO is propylene oxide. Examples of such polyethers containing amino groups are the products available under the name JEFF AMINE® from Huntsman Corporation. Polyethers containing amino groups from the JEFF AMINE® D, JEFF AMINE® ED, JEFF AMINE® T and JEFF AMINE® XTJ series are preferably used.

The polyethers of the JEFFAMINE® D series containing amino groups are amine-terminated polypropylene glycols (PPG) of the general formula where x is a number from 2 to 8.

The polyethers of the JEFFAMINE® ED series containing amino groups have a predominantly

Polyethylene glycol (PEG)-based backbone and correspond to the general formula where y is a number from 5 to 40 and the sum of x + z is a number from 3 to 8. The polyethers of the JEFFAMINE® T series containing amino groups are amine-terminated

Polypropylene glycols (PEG) of the general formula where R is hydrogen, CH3 or C2H5, n is a number 0, 1 or 2 and x + y + z = a number from 3 to 100.

The amino-containing polyethers of the JEFFAMINE® XTJ series are slower amines with a structure analogous to the amines of the D and T series. The JEFFAMINE® XTJ series of amino-containing polyethers are primary amines produced by the amination of epoxy-terminated polyethers. The reaction leads to primary amines with terminal groups of the formula

Preferred polyethers containing amino groups from the JEFFAMINE® product group are JEFF AMINE® D and JEFFAMINE® T.

The composition for preparing the isocyanate-terminated prepolymer preferably contains 0 to 15% by weight of component Cii, based on the sum of all components in the composition.

The compounds of component C can be produced by means of DMC catalysis or by other known production routes. If a DMC catalyst is used, essentially the same information as presented above for component B applies.

Component D, which can optionally be used in the process according to the invention, is an auxiliaries, the auxiliaries preferably being compounds with an antioxidant effect, so-called antioxidants (component D1). Suitable antioxidants are preferably sterically hindered phenols, which can preferably be selected from the group consisting of 2,6-di-tert-butyl-4-methylphenol (ionol), pentaerythritol-tetrakis(3-(3,5-di -tert-butyl-4-hydroxy-phenyl)-propionate), octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate, triethylene-glycol-bis(3-tert-butyl-4 - hydroxy-5-methylphenyl)propionate, 2,2'-thiobis(4-methyl-6-tert-butylphenol) and 2,2'-thiodiethylbis[3-(3,5-di-tert -butyl-4-hydroxyphenyl)propionate]. If required, these can be used individually or in any combination with one another. The composition for preparing the isocyanate-terminated prepolymer preferably contains 0.10 to 0.20% by weight of component D1, based on the sum of all components in the composition. Furthermore, protonic acids, for example, can also be used as auxiliaries (component D2). These are inorganic acids, carboxylic acids, halogenated carboxylic acids, dicarboxylic acids, hydroxycarboxylic acids, sulfonic acids, phosphoric acid, phosphoric acid derivatives, paratoluene sulfonic acids or an ammonium salt. Component D2 is preferably selected from the group consisting of benzoyl chloride, o-chlorobenzoic acid, ammonium nitrate, ammonium chloride, boron trichloride, boron trifluoride, bromoacetic acid, chloroacetic acid, trichloroacetic acid, 2-chloropropionic acid, citric acid, diethyl malonate, diphenylacetic acid, formic acid, cinnamic acid, salicylic acid, naphthoic acid, oxalic acid , Fumaric Acid, Maleic Acid, Citraconic Acid, Adipic Acid, Glutaric Acid, Succinic Acid, Malonic Acid, Phthalic Acid, Isophthaloyl Chloride, Terephthaloyl Chloride, Malic Acid, Tartaric Acid, Uric Acid (2,6,8-trihydroxypurine), Picric Acid (2,4,6-Trinitrophenol), Phosphorus acid, diphosphoric acid, dibutyl phosphate, sulfuric acid, hydrochloric acid, methanesulfonic acid and p-toluenesulfonic acid chloride. Dibutyl phosphate, hydrochloric acid or 2-chloropropionic acid is particularly preferred. The composition for preparing the isocyanate-terminated prepolymer contains 0 to 0.50% by weight, preferably 0 to 0.30% by weight, particularly preferably 0 to 0.20% by weight, of component D2, based on the Sum of all components in the composition. Most preferably, the isocyanate-terminated prepolymer according to the invention is prepared without the addition of a protonic acid D2. The isocyanate-terminated prepolymers according to the invention are expediently prepared by reacting the isocyanate components A with the polyol components B and C, optionally auxiliary D. The isocyanate component A is preferably initially introduced in a molar excess, usually in a reaction vessel and at temperatures in the range from 20 to 160.degree , preferably 40 to 140 ° C, the polyol components B and C metered in either as a mixture or one after the other. Any exothermicity which may occur is expediently intercepted by cooling in such a way that the reaction between the isocyanate groups of the isocyanate component and the hydroxyl groups of the hydroxyl components proceeds at a constant temperature. The reaction is complete when the desired isocyanate contents or viscosities of the isocyanate-terminated prepolymers according to the invention have been reached.

If monomeric diisocyanates are used, any residual amounts of these isocyanates present must be removed after the urethane reaction, for example by distillation or extraction, in order to obtain products with residual monomer contents of <1% by weight, preferably <0.5% by weight and more preferably <0.3% by weight. If polyisocyanates are used to produce the isocyanate-terminated prepolymers according to the invention, it is no longer necessary to remove excess residual monomers after the urethane reaction because polyisocyanates already have residual monomer fractions in the required range of <0.5% by weight. The reaction components are preferably used in proportions such that the properties of the isocyanate-terminated prepolymers described above, in particular the viscosity, the isocyanate content and the functionality, are achieved.

Further objects of this invention are isocyanate-terminated prepolymers obtainable by the process described above, the use of these prepolymers as isocyanate component in 1- and 2-component paint, adhesive and sealant systems, and the 1- and 2-component paint -, adhesive and sealant systems themselves.

The resulting isocyanate-terminated prepolymers according to the invention are suitable for use as one-component moisture-curing coating materials, adhesives and sealants. The isocyanate-terminated prepolymers according to the invention are also suitable for use in two-component curing coating materials, adhesives and sealants. For this purpose, commercially available polyols and/or polyamines (functionality >2 in each case) are used as reactants. Such polyols and/or polyamines have been previously described. In addition, other polyols are solvent-free and solvent-containing polyacrylate polyols, such as those used, for. B. under the trade name Desmophen® A from Viverso GmbH, Bitterfeld. Furthermore, aspartic acid esters can be used as reactants for the isocyanate-terminated prepolymers according to the invention. This special type of polyamines are products with reduced reactivity of the secondary amino groups. This makes it possible to formulate two-component systems with an appropriate pot life (pot life) in the range from 10 to 60 minutes, which is not possible due to the high reactivity of conventional compounds containing primary or secondary amino groups. Examples of suitable aspartic acid esters are e.g. B. Desmophen® NH 1220, Desmophen® NH 1420, Desmophen® NH 1520 and Desmophen® NH 1521 from Covestro Deutschland AG.

The suitable polyols and/or polyamines and also the isocyanate-functional prepolymers according to the invention are generally selected in such a way that the product properties which are optimum for the particular application result.

Further objects of the present invention are thus paint, adhesive or sealant systems, which are 1-component moisture-curing systems, and paint, adhesive or sealant systems, which are 2-component systems, in addition to the isocyanate according to the invention -terminated prepolymer further have at least one isocyanate-reactive component. An isocyanate-reactive component is to be understood as meaning a compound which carries at least one group which is reactive towards isocyanates, such as, for example, diols and polyols and diols and polyamines. examples

materials

Isocyanate 1: Aromatic polyisocyanate based on diphenylmethane diisocyanate (MDI) with an NCO content of 31.5% (31.8), a 2,2'-MDI content of 2.3%(0.1), a 2,4' content -MDI of 12.6%(12.7) and a 4,4'-MDI content of 42.4%(54.4)) and a viscosity of 90 (100) mPas at 25 °C

Polyol 1: polyoxymethylene-polypropylene oxide block copolymer having an OH number of 112 mg KOH/g, prepared using double metal cyanide catalysis, the double metal cyanide catalyst being prepared according to Example 6 of WO 01/80994 A1

Polyol 2: Polyoxymethylene-polypropylene oxide block copolymer having an OH number of 56 mg KOH/g, prepared using double metal cyanide catalysis, the double metal cyanide catalyst being prepared according to Example 6 of WO 01/80994 A1

Polyol 3: polyoxymethylene-polypropylene oxide block copolymer having an OH number of 18 mg KOH/g, prepared using double metal cyanide catalysis, the double metal cyanide catalyst being prepared according to Example 6 of WO 01/80994 A1

Polyol 4: Polypropylene oxide polyether based on 1,2-propylene glycol with an OH number of 112 mg KOH/g

Polyol 5: Polypropylene oxide polyether based on 1,2-propylene glycol with an OH number of 56 mg KOH/g

Polyol 6: Polypropylene oxide polyether based on 1,2-propylene glycol with an OH number of 14 mg KOH/g

Polyol 7: Polypropylene oxide polyether based on 1,2-diaminoethane with an OH number of 60 mg KOH/g and an amine content of 0.7% by weight.

methods

The OH numbers were determined titrimetrically based on DIN 53240-2:2007-II. The Arning content was determined trimetrically according to DIN EN 9702:1998.

The NCO content was determined titrimetrically according to DIN EN ISO 11909:2007-05.

All viscosity measurements were carried out using a Physica MCR 51 rheometer from Anton Paar Germany GmbH (DE) in accordance with DIN EN ISO 3219:1994-10 at a shear rate of 250 s-1.

The film formation time (FBZ, dry-hard time) and film drying times (FTZ, set-to-touch time) were determined according to ASTM D 5895:2013-06 in a linear drying recorder.

Tensile shear strength of the beech/beech bond measured without a gap when subjected to tensile forces parallel to the bonded surface in accordance with DIN EN 205:2016-12.

syntheses

Example 1:

A mixture of 175.0 g of polyoxymethylene-polypropylene oxide block copolymer having an OH number of 112 mg KOH/g prepared under double metal cyanide catalysis (polyol 1) and 214.5 g of polypropylene oxide poly ether based on 1,2-diaminoethane with a OH number of 60 mg KOH/g and an amine content of 0.7% by weight (polyol 7) is placed in a 1 liter ground glass vessel and stirred for 1 hour at 120° C. under a vacuum of 20 mbar. Thereafter, it is cooled to 55.degree. The resulting polyol mixture is converted within about 30 minutes to 571.0 g of an aromatic polyisocyanate based on diphenylmethane diisocyanate (MDI) with an NCO content of 31.5%, a 2,2'-MDI content of 2.3%, a content of 2,4'-MDI of 12.6% and a content of 4,4'-MDI of 42.4% and a viscosity of 90 mPas at 25 ° C (isocyanate 1). The mixture is then heated to 60° C. using any exothermic reaction that may occur. The mixture is stirred at 60° C. until the isocyanate content is constant. A brownish-colored polyisocyanate mixture results with an NCO content of 15.2% by weight, a viscosity of 35,600 mPas (23° C.) and an average isocyanate functionality of 2.7.

Example 2 to 3:

Further polyisocyanates were prepared using the polyols summarized in Table 1 by the method described in Example 1. The resulting characteristics are also summarized in Table 1. Comparative example 4 to 6:

Further polyisocyanates were prepared by the process described in Example 1 using the polyols summarized in Table 1. The resulting characteristics are also summarized in Table 1.

Application tests

Testing the reactivity as a reactive adhesive

To compare the reactivity, the film formation time (FBZ, dry-hard time) and film drying time (FTZ, set-to-touch time) according to ASTM D 5895:2013 in the linear drying recorder and the viscosity at 25 °C (based on DIN EN ISO 3219:1994-10). The wet layer thickness of the reactive adhesive was 250 μm. Furthermore, the storage stability at 70° C. was measured in the form of the increase in viscosity over time. The polyisocyanate mixture is storage-stable if the viscosity has less than doubled within 14 days of storage at 70 °C.

The polyisocyanate mixture according to the invention according to example 1 has a higher viscosity than example 4 (comparison) and comparable storage stability. However, the reactivity of the polyisocyanate mixture according to Example 1 according to the invention, which is reflected in shorter film formation and film drying times, is significantly higher than the reactivity of the comparative example.

This effect can be observed even more clearly in example 2. In contrast to comparative example 5, the reactivity of the polyisocyanate according to the invention is significantly higher than the reactivity of the comparative example.

The polyisocyanate example 3 according to the invention shows not only increased reaction of the three examples mentioned but also the lowest viscosity.

Testing of the tensile shear strength as a reactive adhesive

To compare the adhesive effect, the tensile shear strength of the beech/beech bond was measured without a gap when subjected to tensile forces parallel to the adhesive surface in accordance with DIN EN 205:2016. The tensile shear strength was tested according to the time intervals summarized in the table below.

After 60 minutes, the polyisocyanate mixture according to the invention according to example 1 experiences a higher force than example 4 (comparison) until the test piece breaks. This is also shown by Examples 2 and 3, which experience a higher force than Comparative Examples 5 and 6 until the specimen breaks. The bond strength of the inventive polyisocyanate mixture according to Example 1, which is reflected in higher tensile shear strengths, is significantly higher than the bond strength of the comparative example.

Table 1: Summary of the composition and characteristics of the examples.

Claims

- 23 -Claims

1. A process for the preparation of isocyanate-terminated prepolymers for use as isocyanate component in 1- and 2-component paint, adhesive and sealant systems, comprising or consisting of the implementation of

A. at least one aliphatic, cycloaliphatic, araliphatic and/or aromatic polyisocyanate, component A having an NCO content according to DIN EN ISO 11909:2007-05 of 15 to 60% by weight, preferably 15 to 50% by weight, in particular preferably 15 to 45% by weight,

B. at least one polyoxymethylene-polyoxyalkylene block copolymer with a hydroxyl number according to DIN 53240-2:2007-11 of 15 mg KOH/g to 200 mg KOH/g,

C. i) at least one polyether containing amino groups and based on propylene oxide with a hydroxyl number according to DIN 53240-2:2007-11 of 40 to 80 mg KOH/g, an OH functionality of 4.0 and an amine content according to DIN EN 9702:1998 in the range from 0.5 to 1.0% by weight, ii) optionally at least one amino-containing polyether based on ethylene oxide, propylene oxide or a mixture of ethylene oxide and propylene oxide with an NH2 functionality of 2 or 3, excluding amino-containing polyethers of the component Ci,

D. optional auxiliaries containing protic acids (D2) and/or auxiliaries which are not protic acids according to D2 (D1).

2. The method according to claim 1, characterized in that component B consists of a polyoxymethylene-polypropylene oxide block copolymer or a polyoxymethylene-polyoxyalkylene carbonate block copolymer, the block copolymer preferably having two terminal polyoxyalkylene blocks.

3. The method according to claim 1 or 2, characterized in that at least component B was prepared in the presence of a double metal cyanide catalyst and component B still at least partially contains this double metal cyanide catalyst, the content of double metal cyanide catalyst based on the total amount of component B and C is 10 to 5000 ppm, preferably 10 to 3000 ppm, and the double metal cyanide catalyst content is determined using the amount of metal content from the double metal cyanide catalyst determined according to DIN-ISO 17025 (August 2005).

4. The method according to any one of the preceding claims, characterized in that the polyoxymethylene-polyoxyalkylene block copolymer of component B or that the Polyoxymethylene-polyoxyalkylene block copolymer of component B each have a hydroxyl number according to DIN 53240-2:2007-11 from 15 mg KOH/g to 150 mg KOH/g, preferably from 15 mg KOH/g to 120 mg KOH/g, particularly preferably from 18 mg KOH/g to 112 mg KOH/g.

5. The method according to any one of the preceding claims, characterized in that the polyether containing amino groups of component Ci or the polyether containing amino groups of component Ci each have a hydroxyl number according to DIN 53240-2:2007-11 of 45 to 75 mg KOH/g, preferably 50 has or have up to 70 mg KOH/g.

6. The method according to any one of the preceding claims, characterized in that the polyether containing amino groups of component Ci or the polyether containing amino groups of component Ci each have an amine content according to DIN EN 9702:1998 of 0.56 to 0.94% by weight, preferably 0.62 to 0.88% by weight.

7. The method according to any one of the preceding claims, characterized in that component A comprises at least one aromatic polyisocyanate, preferably 1,5-naphthalene diisocyanate (NDI), diisocyanatodiphenylmethane (2,2'-, 2,4'- and 4,4'- MDI), in particular the 2,4'- and the 4,4'- isomer and technical mixtures of these two isomers or technical mixtures of 2,2'-, 2,4'- and 4,4'-MDI, poly(methylene phenyl isocyanate ) (pMDI, polymeric MDI, crude MDI), diisocyanatomethylbenzene (2,4- and 2,6-toluylene diisocyanate, TDI), especially the 2,4- and the 2,6-isomer and technical mixtures of the two isomers.

8. The method according to any one of the preceding claims, characterized in that the isocyanate-terminated prepolymer is obtained or is obtainable by reacting a composition containing or consisting of

- 50 to 70% by weight of component A,

- 15 to 30% by weight of component B,

- 10 to 30% by weight of component Ci,

- 0 to 15% by weight of component Cii,

- 0.10 to 0.20% by weight of component Dl,

- 0 to 0.50% by weight of component D2, the % by weight being based on the sum of all components of the composition.

9. Isocyanate-terminated prepolymer obtained by or obtainable by a process according to any one of claims 1 to 8.

10. Use of the isocyanate-terminated prepolymers according to claim 9 in paint, adhesive or sealant systems.

11. paint, adhesive or sealant systems containing at least one isocyanate-terminated prepolymer according to claim 9.

12. Paint, adhesive or sealant systems according to claim 11, which are 1-component moisture-curing systems which contain no isocyanate-reactive components apart from the at least one isocyanate-terminated prepolymer.

13. paint, adhesive or sealant systems according to claim 11, wherein it is 2-component

Is systems that have at least one isocyanate-reactive component in addition to the at least one isocyanate-terminated prepolymer.

14. Coated or bonded substrates with lacquer, adhesive or sealant systems according to claims 11 to 13.