HK1088021B - Polyurethane prepolymers blocked with ch-acidic cyclic ketones, reactive systems produced from said polymers and the use of the same - Google Patents

Description

Polyurethane prepolymers capped with CH-acidic cyclic ketones, reaction systems prepared from said polymers and their use

Technical Field

The present invention relates to novel blocked polyurethane prepolymers, to a process for their preparation, and to the polyurethane prepolymers prepared therefrom

Background

The polyamine/epoxy resin systems known from the prior art are distinguished, for example, by their excellent metal adhesion, very good resistance to chemical attack and outstanding corrosion resistance. In the case of solvent-containing formulations and powder coating systems, highly flexible crosslinked films can be obtained using epoxy resins and/or polyaminoamides having a high molar mass, for example based on dimeric fatty acids, as hardeners. Coatings based on solvent-free liquid resins and solvent-free amine hardeners are very brittle due to the low molar mass of the epoxy resin and the high network density formed. Thus, tar substitutes such as benzofuran resins are used in solventless formulations as plasticizers. Especially when relatively large amounts of hydrocarbon resins are employed, such coatings tend to become brittle over time due to migration of non-functional components.

Epoxy resins can impart good and permanent elasticity by combining with polyurethanes. In DE-A2338256, for example, high molecular weight polyether urethane ureas having amino end groups are prepared by reacting prepolymers containing free isocyanate groups with amines in highly dilute solutions and are subsequently cured with epoxy resins. The use of solvents, in particular aromatic solvents, required for this purpose is a practical disadvantage both from a technical and physiological point of view. On the other hand, the viscosity of solvent-free reaction products, such as, for example, those prepared in particular according to DE-A2338256, is too high for practical use.

DE-A2418041 describes a process for producing plasticized moldings and sheets in which an epoxy compound is reacted with an amine compound obtained by hydrolysis of prepolymeric ketimines or enamines. Chemically resistant thermosetting molding compounds having good adhesion and improved properties can be prepared by this process. The described method has the disadvantage of high process engineering costs.

DE-A2152606 describes a reaction system based on alkylphenol-blocked polyisocyanates and polyamines, which can optionally also be cured in combination with epoxy resins. Still, such reaction systems suffer from a few disadvantages associated with the application technology. For example, they have a relatively high viscosity and the molecular weight of the blocking agent released is comparatively low, so that over time they migrate out of the coating and the adhesion of the coating to the substrate is no longer sufficient.

Thus, in order to allow the specific reaction of the polyisocyanate prepolymer with excess diamine to take place, it is in many cases advisable to employ the polyisocyanate in blocked form, as described, for example, in CA-A219986, EP-A293110 or EP-A082983, where the preferred blocking agents used are phenols or substituted phenols. After their reaction with the polyamines, these substances are distilled off incompletely or not from the reaction mixture because of their too high boiling point. However, residues of optionally substituted phenols in the mixture or in the plastic compound will lead to the disadvantages described above.

In EP-A0457089, on the other hand, secondary amines, preferably of low boiling point, are used as blocking agents. The residue of these amines in the reaction mixture is prone to an odor nuisance after deblocking. Although in principle, the secondary amines used in epoxy systems can be incorporated into the system, the reaction proceeds relatively slowly, especially at low temperatures (e.g. room temperature), so that part of the amine will leave the coating. In a particularly preferred manner, the amine blocking agent is distilled from the reaction mixture after deblocking. Although the procedure produces a product that does not cause odor nuisance, the number of steps involved and therefore the cost is too high.

U.S. Pat. No. 6,060,574 also discloses reactive compositions consisting of reversibly blocked organic polyisocyanates and at least one polyamine having at least two primary amino groups and optionally also containing epoxy-containing compounds. Hydrocarbon resins having phenolic hydroxyl groups are used as blocking agents for organic polyisocyanates. Polyisocyanates blocked in this way are distinguished by a significantly reduced reactivity towards polyamines compared with alkylphenol-blocked polyisocyanates. The organic polyisocyanates used may be prepolymers obtained by reacting polyols with an excess of diisocyanates or polyisocyanates. Examples of polyols which may be used are polyether polyols obtainable by alkoxylation of suitable starter molecules, for example monomeric polyols.

However, all reversibly blocked polyurethane prepolymers described in the prior art and prepared by reacting polyurethane prepolymers containing isocyanate groups with blocking agents have the disadvantage that, after reaction with polyamines, the blocking agents are released again. The blocking agent is not chemically incorporated in the plastic produced and therefore it may escape or be washed out over time, which is a major drawback in view of the mechanical properties of the plastic.

Furthermore, the reversibly blocked polyurethane prepolymers known to date have very high viscosities due to intermolecular hydrogen bridges of the urethane groups, which is a great disadvantage for the processing of corresponding reaction systems with polyamines and optionally epoxides. Due to the high viscosity, such systems cannot generally be applied by spraying.

Disclosure of Invention

It is therefore an object of the present invention to provide a novel polyurethane prepolymer which has a much lower viscosity than the reversibly blocked polyurethane prepolymers known hitherto and which, together with polyamines and optionally compounds containing epoxy groups, can be used in room-temperature-curing reaction systems, wherein no blocking agent is released when the reaction system is cured (no elimination system).

It has now been found that polyurethane prepolymers end-capped with specific activated cyclic ketones have a much lower viscosity than the corresponding prepolymers end-capped according to the prior art and that elimination of the blocking agent does not occur after reaction with polyamines (no elimination system).

Accordingly, the present invention provides a polyurethane prepolymer comprising

I) Oxyalkylene ether units and

II) structural units of the general formula (1):

wherein

X is an electron-withdrawing group,

R¹、R²independently of one another, may be a hydrogen atom, a saturated or unsaturated aliphatic or cycloaliphatic radical, an optionally substituted aromatic or araliphatic radical, and the radical in each case contains up to 12 carbon atoms and optionally up to 3 heteroatoms from the elements oxygen, sulfur and nitrogen, and may optionally be substituted by halogen atoms, and

n is an integer of 0 to 5.

The oxyalkylene ether unit of the polyurethane prepolymer of the present invention means a structure of the general formula (2):

wherein

R may be hydrogen or C₁-C₁₀-an alkyl group, and

n may be 1 to 1000, and

m may be 1 to 3.

Preferably, R is hydrogen or a methyl group and n is 1 to 300.

The invention also provides a process for preparing the polyurethane prepolymers of the invention, in which

A) One or more polyisocyanates with

B) One or more polyether polyols, selected from the group consisting of,

C) optionally in the presence of one or more catalysts, and then reacting the free NCO groups with

D) Reacting a blocking agent comprising at least one CH-acidic cyclic ketone of the general formula (3),

wherein

X is an electron-withdrawing group,

R¹、R²independently of one another, may be a hydrogen atom, a saturated or unsaturated aliphatic or cycloaliphatic radical, an optionally substituted aromatic or araliphatic radical, and the radical in each case contains up to 12 carbon atoms and optionally up to 3 heteroatoms from the elements oxygen, sulfur and nitrogen, and may optionally be substituted by halogen atoms, and

n is an integer of 0 to 5,

E) the reaction is optionally carried out in the presence of one or more catalysts.

Polyisocyanates suitable as component A) are all the known aliphatic, cycloaliphatic, aromatic or heterocyclic organic isocyanates, preferably diisocyanates or polyisocyanates having at least two isocyanate groups, and also mixtures of the compounds mentioned. Examples of suitable aliphatic isocyanates are diisocyanates or triisocyanates, such as 1, 4-butane diisocyanate, 1, 5-pentane diisocyanate, 1, 6-hexane diisocyanate (hexamethylene diisocyanate, HDI), 4-isocyanatomethyl-1, 8-octane diisocyanate (triisocyanatononane, TIN), or cyclic systems, such as 4, 4' -methylenebis (cyclohexyl isocyanate) (Desmodur)^_W, Bayer, Leverkusen), 3, 5, 5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI) and omega, omega' -diisocyanato-1, 3-dimethylcyclohexane (H)₆XDI). Particularly suitable are aromatic polyisocyanates, for example 1, 5-naphthalene diisocyanate, diisocyanatodiphenylmethane (2, 2 '-, 2, 4-and 4, 4' -methylenediphenyl diisocyanate, MDI), especially the technical-grade mixtures of the 4, 4 '-isomer and the 2, 4-and 4, 4' -isomers, diisocyanatesIsocyanatomethylbenzenes ((2, 4-and 2, 6-tolylene diisocyanate, TDI), especially the 2, 4-and 2, 6-isomers and technical-grade mixtures of the two isomers, and 1, 3-bis (isocyanatomethyl) benzene (XDI).

Very particularly suitable aromatic diisocyanates are 2, 4-tolylene diisocyanate and technical-grade mixtures thereof containing from 70 to 90% of 2, 4-tolylene diisocyanate and from 30 to 10% of 2, 6-tolylene diisocyanate.

Secondary products of said isocyanates with biuret, isocyanurate, iminooxadiazinedione, uretdione, allophanate and/or urethane structures which are known per se are also suitable for use according to the invention.

Higher molecular weight polyether polyols known per se from polyurethane chemistry which can be obtained in a manner known per se by appropriate initiation of the alkoxylation of molecules are used as component B) in the process according to the invention for preparing the polyurethane prepolymers according to the invention.

Preferably, the polyether polyols used have a molecular weight in the range from 300 to 20,000, preferably from 1000 to 12,000, particularly preferably from 2000 to 6000.

Examples of suitable starter molecules are simple polyols, such as ethylene glycol, 1, 2-or 1, 3-propanediol, 1, 4-butanediol, 1, 6-hexanediol, neopentyl glycol, 2-ethyl-1, 3-hexanediol, glycerol, trimethylolpropane, pentaerythritol, sorbitol, and also low molecular weight hydroxyl group-containing esters of such polyols with aliphatic or aromatic dicarboxylic acids. Other examples are low molecular weight ethoxylated or propoxylated products of such simple polyols, or any mixture of such modified or unmodified alcohols, water, organic polyamines having at least two N-H bonds, or any mixture of such starter molecules.

Suitable compounds for alkoxylation are cyclic ethers, for example tetrahydrofuran and/or alkylene oxides, for example ethylene oxide, propylene oxide, butylene oxide, styrene oxide, or epichlorohydrin, in particular ethylene oxide and/or propylene oxide, which can be used in the alkoxylation in any order or in mixtures.

Very particular preference is given to those polyether polyols having a molecular weight in the range from 300 to 20,000, preferably from 1000 to 12,000, particularly preferably from 2000 to 6000, and an unsaturated end group content of less than or equal to 0.02 meq/g of polyol, preferably less than or equal to 0.015 meq/g of polyol, particularly preferably less than or equal to 0.01 meq/g of polyol (determination: ASTM D2849-69). The polyether polyol has a particularly narrow molecular weight distribution, i.e. a polydispersity (PD ═ M) of 1.1 to 1.5_w/M_n) And/or an OH functionality of 1.90 or more. Preferably, the polyether polyol has a polydispersity of 1.1 to 1.5 and an OH functionality of ≥ 1.9, particularly preferably ≥ 1.95.

Polyether polyols having an unsaturated end group content of less than or equal to 0.02 milliequivalents and a particularly narrow molecular weight distribution, i.e. a polydispersity of from 1.1 to 1.5 and/or an OH functionality of > 1.90, can be prepared in a manner known per se by suitably initiating the alkoxylation of molecules, in particular using double metal cyanide catalysts (DMC catalysts). This is described, for example, in US-A5158922 (e.g.Example 30) and EP-A0654302302 (p.5, 1.26-p.6, 1.32).

Examples of these very particularly preferred polyether polyols are given in table 1:

TABLE 1

	Acclaim_1000	Acclaim_2200	Acclaim_3201	Acclaim_4200	Acclaim_6300	Acclaim_8200
							Physical data
Molecular weight	1000	2000	3000	4000	6000	8000
							Functionality degree	2	2	2	2	3	2
Viscosity (25 ℃ C.)	70	335	620	980	1470	3000
							Chemical data
OH value (mg KOH/g)	112	56	37	28	28	14
							Proportion of double bonds (meq/g)	≤0.0070	≤0.0070	≤0.0070	≤0.0070	≤0.0070	≤0.0070
Acid value (mg KOH/g)	0.02	0.02	0.018	0.018	0.02	0.02

All Acclaims^_The products are all available from Bayer corporation (Leverkusen, DE).

Catalysts known per se from polyurethane chemistry for accelerating the NCO/OH reaction, in particular metal-organic compounds such as tin (II) octoate, dibutyltin (II) diacetate or dibutyltin (II) dilaurate, or tertiary amines, for example triethylamine or diazabicyclooctane, can be used as compounds of component C).

The blocking agents used in component D) are CH-acidic cyclic ketones of the general formula (3):

wherein

X is an electron-withdrawing group,

R¹、R²independently of one another, may be a hydrogen atom, a saturated or unsaturated aliphatic or cycloaliphatic radical, an optionally substituted aromatic or araliphatic radical, and the radical in each case contains up to 12 carbon atoms and optionally up to 3 heteroatoms from the elements oxygen, sulfur and nitrogen, and may optionally be substituted by halogen atoms, and

n is an integer of 0 to 5.

The electron withdrawing group X can be all substituents that result in CH acidity of the alpha hydrogen. These may be, for example, ester groups, sulfoxide groups, sulfone groups, nitro groups, phosphonate groups, nitrile groups, isonitrile groups or carbonyl groups. Nitrile and ester groups are preferred, while methyl and ethyl carboxylate groups are particularly preferred.

Also suitable are compounds of the general formula (3) whose ring optionally contains heteroatoms such as oxygen, sulfur or nitrogen atoms. Preferred herein are the structural units of lactones. The activated cyclic systems of the general formula (3) preferably have a ring size of 5(n ═ 1) and 6(n ═ 2).

Preferred compounds of the formula (3) are cyclopentanone-2-carboxymethyl ester and carboxyethyl ester, cyclopentanone-2-carbonitrile, cyclohexanone-2-carboxymethyl ester and carboxyethyl ester or cyclopentanone-2-carbonyl methane. Cyclopentanone-2-carboxymethyl ester and carboxyethyl ester and cyclohexanone-2-carboxymethyl ester and carboxyethyl ester are particularly preferred.

The CH-acidic cyclic ketones can of course be used in component D) both in mixtures with one another and in any desired mixtures with other blocking agents. Examples of further suitable blocking agents are alcohols, lactams, oximes, malonates, alkyl acetoacetates, triazoles, phenols, imidazoles, pyrazoles and amines, for example butanone oxime, diisopropylamine, 1, 2, 4-triazole, dimethyl-1, 2, 4-triazole, imidazole, diethyl malonate, ethyl acetoacetate (Acetessig ester), acetoxime, 3, 5-dimethylpyrazole, epsilon-caprolactam, N-methyl-, N-ethyl-, N- (iso) propyl-, N-N-butyl-, N-isobutyl-or N-tert-butylbenzylamine or 1, 1-dimethylbenzylamine, N-alkyl-N-1, 1-dimethylmethylbenzylamine, adducts of benzylamines with compounds having activated double bonds, for example malonic acid esters, N-dimethylaminopropylbenzylamine and other optionally substituted benzylamines containing tertiary amino groups, and/or dibenzylamine, or any mixtures of these blocking agents. If they are used at all, the proportion of these further blocking agents of component C) which are different from CH-acidic cyclic ketones is up to 80% by weight, preferably up to 40% by weight and in particular up to 20% by weight, based on the total component D).

Preferably, CH-acidic cyclic ketones of the general formula (3), in particular cyclopentanone-2-carboxyethyl ester, can be used exclusively as component D).

Alkali metal and alkaline earth metal bases, for example powdered sodium carbonate (soda), trisodium phosphate, or amine bases, for example DABCO (1, 4-diazabicyclo [2.2.2] octane), may be used as catalysts E) for the blocking reaction. Carbonates and zinc salts of the metals of the second subgroup are also suitable. Preference is given to using sodium carbonate, potassium carbonate or zinc 2-ethylhexanoate.

The free NCO group content of the polyisocyanate prepolymers of the invention is preferably less than 1% by weight, particularly preferably less than 0.1% by weight and very particularly preferably less than 0.01% by weight.

In the process of the present invention, component B) is reacted with an excess of polyisocyanate component A), optionally in the presence of catalyst C). Optionally unreacted polyisocyanate, and subsequently removed by distillation, e.g., thin film distillation. The molar ratio of hydroxyl groups in the polyether polyol component to NCO groups in the diisocyanate or polyisocyanate is preferably from 1: 1.5 to 1: 20, particularly preferably from 1: 1.8 to 1: 5, very particularly preferably from 1: 1.95 to 1: 2.05.

B) The reaction with A) is generally carried out at a temperature of from 0 to 250 ℃, preferably from 20 to 140 ℃, particularly preferably from 40 to 100 ℃, optionally with the use of a catalyst component C).

To prepare the products of the invention, the polyurethane prepolymers containing isocyanate groups obtained from A) and B), optionally with C), are finally reacted with blocking agents D) at temperatures of from 0 to 250 ℃, preferably from 20 to 140 ℃, particularly preferably from 40 to 100 ℃, optionally with the use of suitable catalysts E).

The blocking agent is used in such an amount that the number of equivalents of blocking agent groups suitable for isocyanate blocking corresponds to at least 30 mol%, preferably 50 mol%, particularly preferably more than 95 mol%, of the number of isocyanate groups to be blocked. It is advisable to have a slight excess of blocking agent to ensure complete reaction of all isocyanate groups. In general, this excess is not more than 20 mol%, preferably not more than 15 mol%, particularly preferably not more than 10 mol%, based on the isocyanate groups to be blocked. It is therefore very particularly preferred that the number of blocking agent groups suitable for NCO blocking is from 95 mol% to 110 mol%, based on the number of isocyanate groups of the prepolymer to be blocked.

In the process of the invention, from 0.001 to 10% by weight, preferably from 0.005 to 5% by weight, particularly preferably from 0.005 to 0.1% by weight, of catalyst, based on the entire reaction mixture, can be added.

In general, one or more organic solvents which are inert under the process conditions can be introduced at any time E) during the preparation of the polyisocyanates according to the invention. The products of the invention are preferably prepared without additional solvent.

In one embodiment of the process of the present invention, component B) is charged into a suitable reaction vessel and optionally heated to 40 to 100 ℃ with stirring. When the desired temperature is reached, the polyisocyanate component A) is added with stirring and stirring is continued until the theoretical NCO content of the polyurethane prepolymer predicted according to the chosen stoichiometry has been reached or very close. To accelerate the subsequent blocking reaction, a suitable catalyst E), for example zinc (II) 2-ethylhexanoate, is subsequently added, during which the temperature of the reaction mixture is optionally adjusted to a value of from 50 to 100 ℃ before or after the addition of the catalyst. When the desired temperature is reached, the blocking agent D) is added and the reaction mixture is heated until the content of free isocyanate groups is less than 0.5% by weight, preferably less than 0.2% by weight and particularly preferably less than 0.1% by weight. Subsequently, the reaction mixture is cooled and optionally a reaction terminator, for example benzoyl chloride, is added.

In another embodiment of the process of the present invention for preparing a prepolymer, the polyisocyanate component of A) is charged into a suitable reaction vessel and optionally heated to 40-100 ℃ with stirring. When the desired temperature has been reached, component B) is added with stirring and stirring is continued until the theoretical NCO content of the polyurethane prepolymer predicted according to the chosen stoichiometry has been reached or very close. The reaction then continues as already described.

The invention also provides a reaction system comprising

a) One or more of the polyurethane prepolymers of the present invention,

b) one or more organic compounds having at least 2 primary amino groups,

c) optionally one or more epoxy group-containing compounds having an average epoxy functionality greater than 1, and

d) optionally products formed by the reaction of components a) to d) with one another,

and a method for preparing the same.

The amines of component b) are polyamines having at least two primary amino groups per molecule and optionally also secondary amino groups, and preferably having an average molecular weight of from 60 to 500. Examples of suitable polyamines are ethylenediamine, 1, 2-and 1, 3-diaminopropane, 1, 4-diaminobutane, 2, 4-and/or 2, 4, 4-trimethylhexamethylenediamine, isoxylylenediamine, 1, 4-diaminocyclohexane, 4, 4-ethylenediaminodicyclohexylmethane, 1, 3-diaminocyclopentane, 4, 4 ' -diaminodicyclohexylsulfone, 4, 4 ' -diaminodicyclohexyl-1, 3-propane, 4, 4 ' -diaminodicyclohexyl-2, 2-propane, 3 ' -dimethyl-4, 4 ' -diaminodicyclohexylmethane, 3-aminomethyl-3, 3, 5-trimethylcyclohexylamine (isophoronediamine), 3- (4) -aminomethyl-1-methylcyclohexylamine, 1-dimethylcyclohexylamine, 1, 4-diaminocyclohexane, 2-dimethylcyclohexylamine, 1, 4-diaminocyclohexane, 1, 3-diaminocyclohexane, 2-dimethylcyclohexylamine, 4-dimethylcyclohexylamine, 3, 5-dimethylcyclohexylamine, 3, Technical-grade bisaminomethyltricyclodecane, octahydro-4.7-methylindene (methanoinden) -1.5-dimethylamine (dimethanamine), or polyamines which have secondary amino groups in addition to at least two primary amino groups, for example diethylene triamine or triethylene tetramine.

Polyamines, in particular diamines having one or more cycloaliphatic rings in the stated molecular weight range, are particularly preferred. These include, for example, 1, 4-diaminocyclohexane, 4 '-diaminodicyclohexylmethane, 1, 3-diaminocyclopentane, 4' -diaminodicyclohexylsulfone, 4 '-diaminodicyclohexyl-1, 3-propane, 4' -diaminodicyclohexyl-2, 2-propane, 3 '-dimethyl-4, 4' -diaminodicyclohexylmethane, 3-aminomethyl-3, 3, 5-trimethylcyclohexylamine (isophoronediamine), 3-and 4-aminomethyl-1-methylcyclohexylamine or technical-grade bisaminomethyltricyclodecane.

Other components which can be used in the amine component are adducts prepared by reacting an excess of the polyamine with an epoxy resin of the type mentioned below.

Further ingredients which can be used in component b) are those prepared by reacting polyether polyols with ammonia and are known, for example, from Huntsman under the trade name Jeffamin^_The polyetheramines sold.

Polyamide resins are also suitable components of component b). Such polyamide resins, including polyaminoamides and polyaminoimidazolines, are available under the trade name Versamid from the company Hamburg^_And (5) selling.

It is, of course, also possible to use mixtures of the stated polyamines as amine component b).

The compounds in the epoxy component c) are epoxy resins which contain on average more than 1 epoxy group per molecule. Examples of suitable epoxy resins are glycidyl ethers of polyhydric alcohols such as butanediol, hexanediol, glycerol or hydrogenated diphenylolpropane, or polyhydric phenols, for example resorcinol, 2-diphenylolpropane (bisphenol A) or diphenylolmethane (bisphenol F) or phenol/aldehyde condensation products. Glycidyl esters of polycarboxylic acids such as hexahydrophthalic acid or dimerized fatty acids may also be used.

Particular preference is given to using liquid epoxy resins based on epichlorohydrin and 2, 2-dihydroxyphenyl propane (bisphenol A) or dihydroxyphenyl methane (bisphenol F) or mixtures thereof. If desired, monofunctional epoxy compounds can be used to reduce the viscosity of the mixture and thus improve the processability. Examples of such compounds are aliphatic and aromatic glycidyl ethers, for example butyl glycidyl ether or phenyl glycidyl ether, glycidyl esters, for example glycidyl esters of versatic acid, or epoxides such as styrene oxide or 1, 2-epoxydodecane.

The solventless room temperature curing reaction system of the present invention generally comprises: 0.4 to 0.9, preferably 0.5 to 0.8 primary amino groups in component b), and 0.02 to 0.6, preferably 0.03 to 0.5 blocked isocyanate groups in component a), each epoxy group in component c).

To prepare the ready-to-use mixtures, the reaction systems of the invention may comprise conventional auxiliaries and additives, for example fillers, solvents, flow control agents, pigments, solvents, reaction accelerators or viscosity regulators. Examples which may be mentioned are reaction accelerators such as salicylic acid, bis (dimethylaminomethyl) phenol or tris (dimethylaminomethyl) phenol, fillers such as sand, crushed stone, silicic acid, asbestos flour, kaolin, talc, metal powder, tar pitch, asphalt, granulated cork or polyamides, plasticizers such as phthalates, or other viscosity regulators such as benzyl alcohol.

Of course, optionally up to 20% by weight, preferably up to 10% by weight, particularly preferably up to 5% by weight, of a solvent or varnish solvent of the type mentioned above can be added to the ready-to-use mixture for the purposes of application engineering. If it is intended to use a solvent at this point, it is possible to dispense with the eventual removal of any solvent used during the synthesis of the polyurethane prepolymer of the invention.

However, very particular preference is given to solvent-free, ready-to-use reaction systems for the purposes of the present invention.

In the process according to the invention for preparing the reaction system, component a) and component b) are mixed in any order, preferably with stirring. Components c) and d) are subsequently added, likewise in any order, optionally with stirring.

The reaction systems according to the invention consisting of a) and b) and optionally c) and/or d) are preferably prepared at temperatures of from-20 ℃ to 50 ℃ and particularly preferably at temperatures of from 0 ℃ to 40 ℃.

The polyisocyanates and the reaction systems according to the invention are suitable for the production of coatings, adhesives, sealing compounds, casting compounds or mouldings in all application areas where good adhesion, chemical resistance and high impact strength are required in addition to good flexibility and elasticity. The inventive systems are particularly suitable as anticorrosive coatings. In particular when the coating is attacked by aggressive media, for example in the case of ballast tank coatings, the systems are distinguished by good wet adhesion and good adhesion under cathodic protection conditions.

The reaction system of the present invention can be used for a wide variety of substrates. Examples which may be mentioned are inorganic substrates, for example composed of concrete and/or stone, metal substrates, for example made of iron, steel, copper, brass, bronze, aluminum or titanium, and alloys of the metals mentioned, and plastics, for example in the form of coatings which are already present, for example, on the metal or inorganic substrates mentioned.

The reaction systems according to the invention can be applied to the surface to be coated, for example by pouring, brushing, dipping, spraying, flow coating, knife coating or roller coating. Depending on the field of application, layer thicknesses of from 10 μm (e.g. thin corrosion protection coatings) up to several centimeters (e.g. crack-filling casting compounds) can thus be achieved.

Depending on the composition chosen for the reaction systems of the invention, they can complete the curing under ambient conditions, i.e. at temperatures of preferably-30 ℃ to 50 ℃ and at relative humidities of preferably 10% to 90%, in from a few minutes up to several days. By increasing the temperature, for example above 50 ℃, additional forced curing is also possible, which may also be desirable in practice.

Detailed Description

Examples of the invention

Preliminary explanation

All percentages are by weight (wt%) unless otherwise indicated.

The polyether polyols used in the examples for preparing the blocked polyurethane prepolymers according to the invention are obtainable, for example, from bayer, lever kusen, germany and are characterized by the following parameters:

TABLE 2

	Acclaim_1000	Acclaim_2200	Acclaim_3201	Acclaim_4200
					Physical data
Molecular weight	1000	2000	3000	4000
					Hydroxyl functionality	2	2	2	2
Viscosity (25 ℃ C.)	70	335	620	980
					Chemical data
Hydroxyl number (mg KOH/g)	112	56	37	28
					Unsaturated end group content (meq/g)	≤0.0070	≤0.0070	≤0.0070	≤0.0070
Acid value (mg KOH/g)	0.02	0.02	0.018	0.018

D.E.R358 is a liquid epoxy resin based on bisphenol A and bisphenol F, having an epoxy equivalent weight of 170 to 180, corresponding to an epoxy content of 23.9 to 25.3% (both values being determined according to ASTM D-1652), available from Dow Plastics, Midland, USA. Perenol^_E8 is an anti-foaming and anti-foaming additive available from Cognis, Dusseldorf, DE, and Laromin^_C260[ bis (4-amino-3-methyl-cyclohexyl) methane]Available from BASF corporation, Ludwigshafen, DE.

Example 1

852.58g (0.43g eq (val))) polyether Acclaim^_4200 (Bayer Co., Ltd., hydroxyl value: 28[ mg KOH/g ]]) A2L four-necked flask equipped with a reflux condenser was charged under a nitrogen atmosphere, and heated to 60 ℃. Subsequently, 74.17g (0.85 gram equivalent (val)) of 2, 4-toluene diisocyanate (Bayer Corp., Leverkusen) was added rapidly at 60 ℃ via a metering funnel. Stirring was continued until the NCO content had reached 1.93%. 1g of zinc 2-ethylhexanoate was then added to the mixture, followed by 73.25g (0.47 g equiv.) of cyclopentanone-2-carboxyethyl ester. The mixture obtained is subsequently stirred at a temperature of 50 ℃ until the NCO content is less than 0.1% (about 4 h). The blocked isocyanate prepolymer obtained showed the following parameters:

blocked NCO content: 1.79 percent

Viscosity (23 ℃ C.) 19,000 mPas.

Example 2

a)743.04g (0.743 gram equivalent) of polyether Acclaim^_2200 (Bayer Co., hydroxyl number: 56[ mg KOH/g ]]) A2L four-necked flask equipped with a reflux condenser was charged under a nitrogen atmosphere, and heated to 60 ℃. 129.29g (1.5 g equiv.) of 2, 4-tolylene diisocyanate (Bayer AG, Leverkusen) were then added rapidly via a metering funnel at 60 ℃. Stirring was continued until the NCO content had reached 3.58%. 1g of zinc 2-ethylhexanoate was then added to the mixture, followed by 127.67g (0.81 g equiv.) of cyclopentanone-2-carboxyethyl ester. The mixture obtained is subsequently stirred at a temperature of 50 ℃ until the NCO content is less than 0.2% (about 4 h). The blocked isocyanate prepolymer obtained showed the following parameters:

blocked NCO content: 3.12 percent of

Viscosity (23 ℃ C.) 23,700 mPas.

b)20g of the prepolymer from a) were mixed with 6.82g of octahydro-4.7-methylindene-1.5-dimethylamine, 20g of D.E.R358, 0.2g of 2, 3-dimethyl-3, 4, 5, 6-tetrahydropyrimidine, 0.4g of oleic acid, 0.2g of Perenol^_E8 and 0.2g benzyl alcohol were stirred together homogeneously. The mixture was poured to a layer thickness of 3 mm. After several hours, a transparent, highly elastic plastic is obtained with the following mechanical parameters:

breaking stress: 20.1MPa

Elongation at break: elongation of 55.9%

Resistance to propagation by tearing: 38.9N/mm.

Example 3

a)591.14g (1.18 gram equivalent) of polyether Acclaim^_1000 (Bayer Corp., hydroxyl number: 112[ mg KOH/g ]]) A2L four-necked flask equipped with a reflux condenser was charged under a nitrogen atmosphere, and heated to 60 ℃. 205.72g (2.36 g equiv.) of 2, 4-tolylene diisocyanate (Bayer Corp., Leverkusen) were then added rapidly via a metering funnel at 60 ℃. Stirring was continued until the NCO content had reached 6.23%. 1g of zinc 2-ethylhexanoate was then added to the mixture, followed by 203.14g (1.3 g equiv.) of cyclopentanone-2-carboxyethyl ester. The mixture obtained is subsequently stirred at a temperature of 50 ℃ until the NCO content is less than 0.2% (about 4 h). The blocked isocyanate prepolymer obtained showed the following parameters:

blocked NCO content: 4.97 percent

Viscosity (23 ℃ C.) 115,000 mPas.

b)20g of the prepolymer from a) were reacted with 7.33g of octahydro-4.7-methylindene-1.5-dimethylamine, 20g of D.E.R358, 0.2g of 2, 3-dimethyl-3, 4, 5, 6-tetrahydropyrimidine, 0.4g of oleic acid, 0.2g of Perenol^_E8 and 0.2g benzyl alcohol were stirred together homogeneously. The mixture was poured to a layer thickness of 3 mm. After 24h, a clear, highly elastic plastic was obtained with shore a and shore D hardness of 92 and 60, respectively.

Example 4

a)812.65g (0.54 gram equivalent) of polyether Acclaim^_3201 (Bayer Co., hydroxyl number: 37[ mg KOH/g ]]) A2L four-necked flask equipped with a reflux condenser was charged under a nitrogen atmosphere, and heated to 60 ℃. 94.27g (1.08 g equiv.) of 2, 4-tolylene diisocyanate (Bayer Corp., Leverkusen) are then added rapidly at 60 ℃ via a metering funnel. Stirring was continued until the NCO content had reached 251 percent. 1g of zinc 2-ethylhexanoate was then added to the mixture, followed by 93.09g (0.6 g equiv.) of cyclopentanone-2-carboxyethyl ester. The mixture obtained is subsequently stirred at a temperature of 50 ℃ until the NCO content is less than 0.2% (about 4 h). The blocked isocyanate prepolymer obtained showed the following parameters:

blocked NCO content: 2.28 percent

Viscosity (23 ℃ C.) 15,200 mPas.

b)20g of the prepolymer from a) were mixed with 6.70g of octahydro-4.7-methylindene-1.5-dimethylamine, 20g of D.E.R.358, 0.2g of 2, 3-dimethyl-3, 4, 5, 6-tetrahydropyrimidine, 0.4g of oleic acid, 0.2g of Perenol^_E8 and 0.2g benzyl alcohol were stirred together homogeneously. The mixture was poured to a layer thickness of 3 mm. After several hours, a transparent, highly elastic plastic is obtained with the following mechanical parameters:

breaking stress: 19.9MPa

Elongation at break: 56.9% elongation

Resistance to propagation by tearing: 29.6N/mm.

Example 5

a)786.64g (0.62 g equiv.) of a polyether polyol having a hydroxyl number of 42(mg KOH/g) were prepared by base-catalyzed simultaneous ethoxylation and propoxylation of a 2: 1 mixture of propylene glycol and glycerol (EO/PO ratio 2: 8), charged under nitrogen into a 2L four-necked flask equipped with a reflux condenser and heated to 60 ℃. 107.35g (1.23 g equiv.) of 2, 4-tolylene diisocyanate (Bayer Corp., Leverkusen) were then added rapidly via a metering funnel at 60 ℃. Subsequently, stirring was continued until the NCO content had reached 2.90%. 1g of zinc 2-ethylhexanoate was then added to the mixture, followed by 106.01g (0.68 g equiv.) of cyclopentanone-2-carboxyethyl ester. The mixture obtained is subsequently stirred at a temperature of 50 ℃ until the NCO content is less than 0.2% (about 4 h). The blocked isocyanate prepolymer obtained showed the following parameters:

blocked NCO content: 2.59 percent

Viscosity (23 ℃ C.) 29,900 mPas.

b)20g of the prepolymer from a) were mixed with 6.75g of octahydro-4.7-methylindene-1.5-dimethylamine, 20g of D.E.R.358, 0.2g of 2, 3-dimethyl-3, 4, 5, 6-tetrahydropyrimidine, 0.4g of oleic acid, 0.2g of Perenol^_E8 and 0.2g benzyl alcohol were stirred together homogeneously. The mixture was poured to a layer thickness of 3 mm. After several hours, a transparent, highly elastic plastic is obtained with the following mechanical parameters:

breaking stress: 17.8MPa

Elongation at break: elongation at 41.2%

Resistance to propagation by tearing: 37.7N/mm.

Example 6

a)845.6g (0.45 gram equivalent) of a mixture of linear polyether polyols (hydroxyl number: 28[ mgKOH/g ]) comprises: 55% of a linear polyether polyol, obtained by ethoxylation and propoxylation of propylene glycol (EO/PO ratio 1: 3), and 45% of a linear polyether polyol, obtained by ethoxylation and propoxylation of propylene glycol (EO/PO ratio 1: 6), were placed in a 2L four-necked flask equipped with a reflux condenser under nitrogen and heated to 60 ℃. 77.68g (0.9 g equiv.) of 2, 4-tolylene diisocyanate (Bayer AG, Leverkusen) were then added rapidly via a metering funnel at 60 ℃. Subsequently, stirring was continued until the NCO content had reached 2.03%. 1g of zinc 2-ethylhexanoate was then added to the mixture, followed by 76.71g (0.49 g equiv.) of cyclopentanone-2-carboxyethyl ester. The mixture obtained is subsequently stirred at a temperature of 50 ℃ until the NCO content is less than 0.2% (about 4 h). The blocked isocyanate prepolymer obtained showed the following parameters:

blocked NCO content: 1.88 percent

Viscosity (23 ℃ C.) 15,600 mPas.

b)20g of the prepolymer from a)With 6.59g octahydro-4.7-methylindene-1.5-dimethylamine, 20g D.E.R358, 0.2g 2, 3-dimethyl-3, 4, 5, 6-tetrahydropyrimidine, 0.4g oleic acid, 0.2g Perenol^_E8 and 0.2g benzyl alcohol were stirred together homogeneously. The mixture was poured to a layer thickness of 3 mm. After a few hours, a very slightly turbid, highly elastic plastic is obtained with the following mechanical parameters:

breaking stress: 18.7MPa

Elongation at break: 60.5% elongation

Resistance to propagation by tearing: 26.4N/mm.

Example 7

10g of each of the blocked polyurethane prepolymers prepared according to examples 1 to 6 and 0.05g of Perenol^_E8 and 0.05g 2, 3-dimethyl-3, 4, 5, 6-tetrahydropyrimidine were mixed with stirring. Subsequently, Laromin was added with stirring^_C260 in the amounts shown in table 3, and then allowing the reactive mixture to stand at ambient temperature for 3 days. In all cases, i.e., for all described amounts of Laromin^_C260, a transparent, homogeneous, well-cured and elastic plastic was obtained.

TABLE 3

	Laromin_C 260
				Blocked polyurethane prepolymers from the following examples	The dosage is 1g]	The dosage is 2g]	The dosage is 3g]
1	0.4	0.6	0.8
				2	0.6	0.8	1.2
3	1.6	2.0	2.4
				4	0.6	0.8	1.2
5	0.6	0.8	1.2
				6	0.6	0.8	1.2

Example 8

283.5g (0.04 g eq.) of polyether Acclaim^_8200 (Bayer corporation, Leverkusen, hydroxyl number: 15.8[ mg KOH/g ]]) A500 mL three-necked flask equipped with a reflux condenser was charged under a nitrogen atmosphere, and heated to 60 ℃. Subsequently, 13.9g (0.08 g equiv.) of 2, 4-tolylene diisocyanate (Bayer Corp., Leverkusen) were added rapidly at 60 ℃ via a metering funnel. Subsequently, stirring was continued until the NCO content had reached 1.13%. Subsequently, 93mg of zinc tetramethylpimelate were added to the mixture, followed by 12.5g (0.08 g equiv.) of cyclopentanone-2-carboxyethyl ester. The mixture obtained is subsequently stirred at a temperature of 50 ℃ until the NCO content is less than 0.2% (about 22 h).

Blocked NCO content: 1.08 percent

Viscosity (23 ℃ C.) 31,000 mPas.

Example 9

112g (0.01 gram equivalent) of a polyether Acclaim^_12200 (Bayer, Leverkusen, hydroxyl number: 10.0[ mg KOH/g ]]) Into a 250mL three-necked flask equipped with a reflux condenser, a nitrogen atmosphere was charged, and heated to 60 ℃. Subsequently, 3.5g (0.02 gram equivalent) of 2, 4-tolylene diisocyanate (Bayer Corp., Leverkusen) were added rapidly via a metering funnel at 60 ℃. Subsequently, stirring was continued until the NCO content had reached 0.73%. 59mg of zinc acetylacetonate are subsequently added to the mixture, followed by 3.1g (0.01 g equiv.) of cyclopentanone-2-carboxyethyl ester. The mixture obtained is subsequently stirred at a temperature of 50 ℃ until the NCO content is less than 0.2% (about 22 h).

Blocked NCO content: 0.71 percent

Viscosity (23 ℃ C.) 103,000 mPas.

Example 10

100g (0.1 gram equivalent) of the polyether Acclaim^_2200 (Bayer, Leverkusen, hydroxyl number: 55.9[ mg KOH/gl) was charged in a 250mL three-necked flask equipped with a reflux condenser under nitrogen and heated to 60 ℃. Subsequently, 17.4g (0.05 gram equivalent) of 2, 4-tolylene diisocyanate (Bayer Corp., Leverkusen) were added rapidly via a metering funnel at 60 ℃. Subsequently, stirring was continued until the NCO content had reached 3.58%. Subsequently, 70mg of zinc 2-ethylhexanoate were added to the mixture, followed by 18.7g (0.12 g equiv.) of cyclohexanone-2-carboxyethyl ester. The mixture obtained is subsequently stirred at a temperature of 50 ℃ until the NCO content is less than 0.2% (approximately 16 h).

Blocked NCO content: 3.13 percent

Viscosity (23 ℃ C.) 17,700 mPas.

Example 11

989.4g (0.25 gram equivalent) of polyether Acclaim^_4200 (Bayer Co., Leverkusen, hydroxyl number: 28.3[ mg KOH/g ]]) A2L three-necked flask equipped with a reflux condenser was charged under nitrogen atmosphere and heated to 60 ℃. Subsequently, 87g (0.5 gram equivalent) of 2, 4-tolylene diisocyanate (Bayer Corp., Leverkusen) were added rapidly via a metering funnel at 60 ℃. Subsequently, stirring was continued until the NCO content had reached 1.95%. Subsequently, 215.4g (0.1 g equiv.) of the obtained amount of the prepolymer was taken and placed in another flask to be reacted with 18.7g of cyclohexanone-2-carboxyethyl ester (0.11g equiv.) in which 350mg of zinc acetylacetonate had been suspended in advance. The mixture obtained is subsequently stirred at a temperature of 50 ℃ until the NCO content is less than 0.2% (about 30 h).

Blocked NCO content: 1.68 percent of

Viscosity (23 ℃ C.) 32,000 mPas.

Example 12

25.5g (0.15 gram equiv.) of Cyclohexanone-2-carboxyethyl ester were slowly charged under nitrogen into a 250mL three-necked flask equipped with a reflux condenser, charged beforehand with 180g (0.15 gram equiv.) of Desmodur^_E14 (isocyanate-functionalized polyurethane prepolymer, ex Bayer AG (Leverkusen), NCO content: 3.3% by weight, viscosity: 6800mPa.s, equivalent: about 1270) and 0.206g of zinc 2-ethylhexanoate 28.2g of methoxypropyl acetate and 59.9g of xylene were used as solvents. After 20h, the NCO content had reached 0.8%. 14.4g of 2-butanol were additionally added.

Blocked NCO content: 2.89 percent.

Example 13

10g of each of the end-capped polyurethane prepolymers prepared according to examples 8 to 12 and 0.05g of Perenol^_E8 and 0.05g 2, 3-dimethyl-3, 4, 5, 6-tetrahydropyrimidine were mixed with stirring. Subsequently, Laromin was added with stirring^_C260, addThe amounts are shown in Table 4, and the reactive mixture is then allowed to stand at ambient temperature for 3 days. Laromin in all cases, i.e. for all the quantities described^_C260, a transparent, homogeneous and elastic plastic is obtained.

TABLE 4

	Laromin_C 260
				Blocked polyurethane prepolymers from the following examples	The dosage is 1g]	The dosage is 2g]	The dosage is 3g]
8	0.4	0.6	0.8
				9	0.4	0.6	0.8
10	0.4	0.6	0.8
				11	0.4	0.6	0.8
12	0.4	0.6	0.8

Claims (9)

1. A polyurethane prepolymer comprising

I) Oxyalkylene ether units and

II) structural units of the general formula (1):

wherein

X is an electron-withdrawing group,

R¹、R²independently of one another, is a hydrogen atom, saturated or unsaturatedAliphatic or cycloaliphatic radicals, optionally substituted aromatic or araliphatic radicals and the radicals in each case containing up to 12 carbon atoms and optionally up to 3 heteroatoms from the elements oxygen, sulfur and nitrogen, and optionally substituted by halogen atoms, and

n is an integer of 0 to 5.

2. A polyurethane prepolymer according to claim 1 characterised in that the electron-withdrawing group X is an ester, sulphoxide, sulphone, nitro, phosphonate, nitrile, isonitrile or carbonyl group.

3. A process for preparing the polyurethane prepolymer of claim 1 or 2, wherein

A) One or more polyisocyanates with

B) One or more polyether polyols, selected from the group consisting of,

C) optionally in the presence of one or more catalysts, and then reacting the free NCO groups with

D) Reacting a blocking agent comprising at least one CH-acidic cyclic ketone of the general formula (3),

wherein

X is an electron-withdrawing group,

R¹、R²independently of one another, is a hydrogen atom, a saturated or unsaturated aliphatic or cycloaliphatic radical, an optionally substituted aromatic or araliphatic radical, and the radical in each case contains up to 12 carbon atoms and optionally up to 3 heteroatoms from the elements oxygen, sulfur and nitrogen, and is optionally substituted by halogen atoms, and

n is an integer of 0 to 5,

E) the reaction is optionally carried out in the presence of one or more catalysts.

4. A process according to claim 3, characterised in that the electron-withdrawing group X of the CH-acidic cyclic ketone is an ester, sulphoxide, sulphone, nitro, phosphonate, nitrile, isonitrile or carbonyl group.

5. A reactive composition comprising

a) One or more polyurethane prepolymers according to claim 1 or 2,

b) one or more organic compounds having at least 2 primary amino groups,

c) optionally one or more epoxy group-containing compounds having an average epoxy functionality greater than 1,

d) optionally catalysts and/or additives, and

e) optionally from the reaction of components a) to d) with one another.

6. A process for preparing the reaction composition of claim 5, wherein components a) to d) are mixed with each other in any order.

7. Use of the reactive composition of claim 6 for the production of adhesives, sealing compounds, moldings and coatings.

8. A substrate coated with the coating of claim 7.

9. A molded article obtainable according to claim 7.