HK1090076B - Adhesive compositions containing blocked polyurethane prepolymers - Google Patents

Description

Adhesive compositions comprising blocked polyurethane prepolymers

Technical Field

The present invention relates to novel reactive compositions based on blocked polyurethane prepolymers, to a process for their production and to their use in adhesive compositions.

Background

The blocking of polyisocyanates or polyurethane prepolymers for the temporary protection of the isocyanate groups is a known processing method and is described, for example, in Houben WeylMethoden der organischen ChemieXIV/2, pp.61 to 70. A review of suitable blocking agents in principle is found, for example, in Wicks et al, progress in organic coatings 1975,3，pp.73-79，1981，9from pp.3 to 28 and 1999,36pp.148-172. Curable compositions comprising blocked polyisocyanates or polyurethane prepolymers are used, for example, in Polyurethane (PUR) lacquers or Polyurethane (PUR) adhesives.

Thus, DE-A19963585 describes a hot-melt adhesive composition comprising: a prepolymer containing isocyanate groups, obtained by reacting a mixture of at least partially crystalline, linear polyester with linear polyether and optionally amorphous polyester with a diisocyanate, the reactive isocyanate groups being partially or completely capped with known capping agents; and diamines and/or their epoxy adducts as a crosslinker component.

In EP-A0419928, one-pack polyurethane adhesives with a long shelf life are described which are at least partially crystalline at room temperature, are predominantly linear and can be cured by the action of heat. They are based on at least partially crystalline polyurethane prepolymers comprising isocyanate groups terminated by monofunctional blocking agents known from polyurethane chemistry and at least one low molecular weight, NH-and/or OH-functional chain extender or crosslinker.

Blocked isocyanates are also described in US-B4798879 as a component of adhesive systems. There, two-component systems are described which set rapidly at room temperature and comprise prepolymers containing blocked isocyanate groups and primary amines as hardeners.

In the aforementioned adhesive composition, the blocking agent performs the following tasks: 1) it prevents premature reaction of NCO groups with the NH and/or OH crosslinker components, and 2) it regulates the curing of the adhesive in a specific temperature range from its specific deblocking properties. Furthermore, the shelf life of the adhesive composition is increased as a result of preventing undesired side reactions with traces of water which enter the adhesive during production or storage and lead to an increase in viscosity and finally to curing before processing.

However, in addition to these desirable properties, a single capping agent also brings disadvantages such as lack of cost-effectiveness, environmental problems and critical physiological effects.

The volatile organic compounds are released by the separation of the blocking agent. These substances generally remain in the adhesive layer and act as plasticizers, which adversely affect the application performance profile of the adhesive formulation. Likewise, the isolation of the blocking agent is an equilibrium reaction. Since the detached blocking agent remains in the glue line, deblocking does not proceed to completion, which leads to incomplete crosslinking of the adhesive. This also causes significant impairment of the adhesive application performance profile. However, if the detached blocking agents leave the adhesive layer, their gaseous escape can lead to the formation of bubbles in the adhesive layer and thus also to a reduction in the strength of the bonded joint.

In WO-A03/004545, emission-free blocked organic polyisocyanates and polyisocyanate prepolymers are disclosed, wherein special CH-acidic cyclic ketones are used as blocking agents. The crosslinking of the blocked isocyanate is carried out with the polyol at a temperature of 110 ℃ to 140 ℃ within 15 to 30 minutes or at a temperature of 300 ℃ to 400 ℃ within 2 minutes without separation, i.e. release, of the blocking agent. Furthermore, it is mentioned that the polyisocyanates blocked according to the invention can also be cured with diamines or polyamines. This reaction should preferably be carried out at room temperature. However, the reaction conditions mentioned above inhibit the widespread use of the systems as adhesives, since many substrates are irreversibly damaged at temperatures of 110-130 ℃ over a period of 15-30 minutes. Furthermore, the above-mentioned crosslinking conditions are generally unsuitable from an economic viewpoint (energy cost).

DE-A10260300 discloses crosslinkers for powder coatings based on emission-free blocked polyurethane crosslinkers. The blocking is again carried out using special CH-acidic cyclic ketones. The curing is carried out with known curing agents for powder coatings at temperatures of 110 ℃ to 220 ℃ for 1 to 6 minutes. Here again, the crosslinking conditions are inhibitory for the use as adhesives for the reasons already mentioned.

DE-A10260299 describes polyurethane prepolymers end-blocked by special CH-acidic cyclic ketones and their use for producing adhesives, sealants, moldings and coatingsThe polyurethane prepolymers described cure without emissions and are based on polyethers. Curing of the blocked prepolymers is carried out with polyamines having a molecular weight of from 60 to 500g/mol or with polyetheramines such as those known under the trade name HuntsmanAnd (5) selling. Curing of these systems takes place at room temperature within a few minutes to hours. It is a two-component system which has only a very limited processing time (pot life) due to the short curing time. This can lead to processing problems, such as when bonding large area substrates.

It is an object of the present invention to provide reactive compositions based on blocked Polyurethane (PUR) prepolymers as adhesive formulations which react without emissions, i.e. without isolation of the blocking agent, have a good shelf life at ambient temperature, crosslink at low temperatures and at the same time exhibit a sufficiently long pot life or processing time.

This object is achieved by the reactive compositions according to the invention based on PUR prepolymers which are terminated with special CH-acidic compounds and are very suitable as crosslinker components for heat-activatable adhesive compositions. These specially blocked polyisocyanate prepolymers can be combined with OH-functional reactants in which the OH component undergoes activation by the β -amine component and curing without separation of volatile species at room temperature within a few hours or at a temperature of 50 ℃ to 90 ℃ within a few minutes to a few hours.

Disclosure of Invention

The present invention relates to a reactive composition comprising

A) One or more blocked polyurethane prepolymers having a blocked isocyanate group (calculated as NCO) content of from 0.1 to 20% by weight and prepared from:

i) at least one aromatic, aliphatic, araliphatic and/or cycloaliphatic diisocyanate having a free NCO group content of 5 to 60% by weight,

ii) a polyol component comprising at least one polyester polyol, and/or at least one polyether polyol and/or at least one polycarbonate polyol,

iii) CH-acidic cyclic ketones corresponding to the general formula (I) as blocking agents

Wherein

X represents an electron-withdrawing group,

R¹and R²Independently of one another represent a radical H, C₁-C₂₀(cyclo) alkyl, C₆-C₂₄Aryl radical, C₁-C₂₀(cyclo) alkyl ester or amide, C₆-C₂₄Aryl esters or amides, mixed aliphatic/aromatic radicals containing 1 to 24 carbon atoms, which may also be part of a 4-to 8-membered ring

n is an integer of 0 to 5, and

B) one or more OH-functional compounds in which the OH component undergoes activation by the beta-amine component,

C) optionally a catalyst and

D) optionally additives and/or auxiliaries.

The invention also relates to a composite system comprising two adherends bonded together by the reactive composition according to the invention.

Detailed Description

Suitable diisocyanates as component i) for the production of the blocked polyurethane prepolymers A) are those having an isocyanate content of from 5 to 60% by weight, based on the diisocyanate, and containing aliphatically, cycloaliphatically, araliphatically and/or aromatically bonded isocyanate groups. Examples include 1, 4-diisocyanatobutane, 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, 1-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-isocyanato-prop-2-yl) benzene (TMXDI), 2, 4-and/or 2, 6-diisocyanatotoluene (TDI), 2 ' -, 2, 4 ' -and/or 4, 4 ' -diisocyanatodiphenylmethane (MDI), 1, 5-diisocyanatonaphthalene or 1, 3-and 1, 4-bis (isocyanatomethyl) benzene. Preferred diisocyanates are 1, 6-diisocyanatohexane (HDI), 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 4 '-diisocyanatodicyclohexylmethane, 2, 4-and/or 2, 6-diisocyanatotoluene (TDI) and 2, 2' -, 2, 4 '-and/or 4, 4' -diisocyanatodiphenylmethane (MDI).

Suitable starting components i) also include polyisocyanate adducts which are prepared from the aforementioned diisocyanates and contain uretdione (uretdione), isocyanurate, iminooxadiazinedione (iminooxadiazinedione), urethane, allophanate, acylurea, biuret and/or oxadiazinetrione groups. Examples are described in J.Prakt.chem.336(1994)185-200 or DE-A1670666, DE-A1954093, DE-A2414413, DE-A2456329, DE-A2641380, DE-A3700209, DE-A3900053, DE-A3928503, EP-A336205, EP-A339396 and EP-A798299.

Suitable polyols as component ii) for producing the blocked polyurethane prepolymers include polyester polyols, polyether polyols and/or polycarbonate polyols known from polyurethane chemistry.

Polyester polyols having a number average molecular weight of from about 200 to about 10000g/mol, preferably from about 1000 to about 6000g/mol, are suitable as polyol component ii). Polyester polyols can be formed from the reaction of low molecular weight alcohols, in particular ethylene glycol, diethylene glycol, neopentyl glycol, hexanediol, butanediol, propylene glycol, glycerol or trimethylolpropane, with caprolactone. Also suitable as polyfunctional alcohols for the production of the polyester polyols are 1, 4-hydroxymethylcyclohexane, 2-methyl-1, 3-propanediol, 1, 2, 4-butanetriol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol and polybutylene glycol.

Other suitable polyester polyols may be produced by polycondensation. The di-and/or tri-functional alcohol may react with the insufficient di-and/or tri-carboxylic acid, or reactive derivative thereof, in a condensation reaction to form a polyester polyol. Suitable dicarboxylic acids include adipic acid or succinic acid and higher homologues thereof containing up to 16C atoms; unsaturated dicarboxylic acids such as maleic acid or fumaric acid; and aromatic dicarboxylic acids, especially the isomeric phthalic acids, such as phthalic acid, isophthalic acid or terephthalic acid. Suitable tricarboxylic acids include citric acid or 1, 2, 4-trimellitic acid. The above acids may be used alone or as a mixture of two or more. Particularly suitable alcohols include hexanediol, butanediol, ethylene glycol, diethylene glycol, neopentyl glycol, 3-hydroxy-2, 2-dimethylpropyl-3-hydroxy-2, 2-dimethylpropionate, trimethylolpropane or mixtures of two or more of these alcohols. Particularly suitable acids are phthalic acid, isophthalic acid, terephthalic acid, adipic acid or dodecanedioic acid or mixtures thereof.

Polyester polyols having high molecular weight include the reaction product of a polyfunctional, preferably difunctional alcohol (optionally together with a small amount of a trifunctional alcohol) and a polyfunctional, preferably difunctional carboxylic acid. Instead of the free polycarboxylic acids, it is also possible to use the corresponding polycarboxylic anhydrides or their corresponding polycarboxylic esters with alcohols preferably containing 1 to 3C atoms. The polycarboxylic acids are aliphatic, cycloaliphatic, aromatic or heterocyclic, or both. They may optionally be substituted, for example, with alkyl, alkenyl, ether or halogen groups. Suitable polycarboxylic acids include succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, phthalic acid, isophthalic acid, terephthalic acid, 1, 2, 4-trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylenetetrahydrophthalic anhydride (endomethylenetetrahydrophthalic acid), glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimer or trimer fatty acids or mixtures thereof.

Polyesters obtainable from lactones, such as those based on epsilon-caprolactone (also known as "polycaprolactone"), or hydroxycarboxylic acids, such as omega-hydroxycaproic acid, may also be used.

Oleochemical-derived polyester polyols may also be used. For example, these polyols can be produced by: the complete ring opening of a fatty mixture containing at least partially ethylenically unsaturated fatty acids with one or more epoxidized triglycerides containing 1-12C-atoms alcohols and the subsequent partial transesterification of the triglyceride derivatives to form alkyl ester polyols containing 1-12C-atoms in the alkyl group.

Polyether polyols suitable as polyol component ii) are known from polyurethane chemistry. They are typically obtained starting from low molecular weight, polyfunctional, OH-or NH-functional compounds as starting materials by reaction with cyclic ethers or mixtures of different cyclic ethers. Bases, such as KOH or double metal cyanide-based systems, are used as catalysts in these reactions. Production processes suitable for this purpose are disclosed in US-B6486361 or l.e.st.pierre, polyether moiety I, polyalkylene oxides and other polyethers, compiled: norman g.gaylord; xiii, High polymers vol; interscience Publishers; 1963, new york; p.130 and pages below.

Suitable starting materials preferably contain from 2 to 8, preferably from 2 to 6, hydrogen atoms capable of addition polymerization with cyclic ethers. Such compounds include water, ethylene glycol, 1, 2-or 1, 3-propanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 6-hexanediol, bisphenol A, neopentyl glycol, glycerol, trimethylolpropane, pentaerythritol or sorbitol.

Alkylene oxides, such as ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, styrene oxide or tetrahydrofuran, are suitable as cyclic ethers. In component ii), polyethers containing propylene oxide, ethylene oxide and/or tetrahydrofuran units, more preferably containing propylene oxide and/or ethylene oxide units, based on the above-mentioned starting materials, are preferably used.

The polyether polyols suitable as polyol component ii) have number average molecular weights of about 200-.

Polycarbonate polyols suitable for use as the polyol component ii) are substantially linear and have at least two, preferably terminal, OH groups. They can be obtained from the reaction of diols, such as propylene glycol, 1, 4-butanediol or 1, 6-hexanediol, diethylene glycol, triethylene glycol or tetraethylene glycol or mixtures thereof, with diaryl carbonates, such as diphenyl carbonate or phosgene.

The ratio of components i) and ii) to each other is chosen so as to obtain an equivalent ratio of NCO groups to OH groups of from 1.2 to 4.0, preferably from 1.4 to 3.0.

The reaction of components i) and ii) for the preparation of the polyurethane prepolymer A) is carried out such that the polyol which is liquid at the reaction temperature is blended with excess polyisocyanate and the homogeneous mixture is stirred until a constant NCO content is obtained. The reaction temperature is 40 ℃ to 180 ℃, preferably 50 ℃ to 140 ℃. The production of the polyurethane prepolymers A) can of course also be carried out continuously in stirred cascade vessels or suitable mixers, such as high-speed mixers according to the rotor-stator principle.

It is also possible to use an insufficient amount of diisocyanate, preferably 1, 6-diisocyanatohexane (HDI), 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 4 ' -diisocyanatodicyclohexylmethane, 2, 4-and/or 2, 6-diisocyanatotoluene (TDI) and/or 2, 4 ' -and/or 4, 4 ' -diisocyanatodiphenylmethane (MDI) for modifying polyester and/or polyether and/or polycarbonate polyols, and to react the polyol containing urethane groups with an excess of diisocyanate at the completion of the reaction to form polyurethane prepolymer A). If desired, catalysts and/or solvents for promoting the NCO/OH reaction can also optionally be added during the reaction of components i) and ii).

Amines or organometallic compounds known from polyurethane chemistry are suitable as catalysts. Suitable amine catalysts include tertiary amines such as triethylamine, dimethylbenzylamine, N, N, N ', N ' -tetramethyldiaminodiethyl ether, 1, 8-diazabicyclo-5, 4, 0-undecene-7 (DBU), and N, N ' -dimorpholinodiethyl ether (DMDEE); and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyl-and N-ethyldiethanolamine, and dimethylaminoethanol.

Also suitable are organometallic compounds of tin, lead, iron, titanium, bismuth or zirconium, such as iron (II) chloride, zinc chloride, lead octoate and preferably tin salts, such as tin dioctoate, tin (II) acetate, tin (II) ethylhexoate, tin (II) diethylhexoate, dibutyltin dilaurate, and dialkyltin (IV) carboxylates. Tin oxide and tin sulfide, as well as tin mercaptides, may also be used. Specific compounds include bis (tributyltin) oxide, bis (trioctyltin) oxide, dibutyltin bis (2-ethylhexyl mercaptide) and dioctyltin, and dibutyltin bis-dodecylmercaptide and dioctyltin. Ti compounds, in particular Ti (IV) -O-alkyl compounds, are also suitable. Suitable alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, 2-pentyl and 3-pentyl; ethyl, n-propyl, isopropyl, n-butyl, isobutyl and tert-butyl are preferred. Particularly preferred is butylated ti (iv). As organobismuth compounds, use is made in particular of bismuth carboxylates in which the carboxylic acid contains 2 to 20C atoms, preferably 4 to 14C atoms.

If catalysts are used, they are used in amounts of from 0.01 to 8% by weight, preferably from 0.1 to 5% by weight, based on the total amount of components i) and ii).

The starting compounds iii) used for the production of the blocked polyurethane prepolymers A) are CH-acidic cyclic ketones corresponding to the general formula (I),

wherein

X represents an electron-withdrawing group,

R¹and R²Independently of one another represent a radical H, C₁-C₂₀(cyclo) alkyl, C₆-C₂₄Aryl radical, C₁-C₂₀(cyclo) alkyl ester or amide, C₆-C₂₄Aryl esters or amides, mixed aliphatic/aromatic radicals containing 1 to 24 carbon atoms which may also be part of a 4-to 8-membered ring, and

n is an integer of 0 to 5.

The electron withdrawing group X in formula (I) may be any substituent that results in CH acidity of the hydrogen in the alpha-position. Examples include ester groups, amide groups, sulfoxide groups, sulfone groups, nitro groups, phosphonate groups, nitrile groups, isonitrile groups, carbonyl groups, polyhaloalkyl groups and halogens, in particular fluorine and chlorine. Preference is given to nitrile and ester groups and particular preference to methyl and ethyl carboxylates.

Suitable starting compounds iii) are also compounds analogous to the general formula (I), wherein the ring optionally comprises heteroatoms, such as oxygen, sulfur or nitrogen atoms. If a nitrogen atom is present in the ring, the preferred structural element is a lactone or thiolactone.

The ring size of the activated cyclic ketones of formula (I) is preferably 5(n ═ 1) or 6(n ═ 2), n preferably being from 1 to 2.

Preferred starting compounds iii) are cyclopentanone-2-carboxymethyl ester and-carboxyethyl ester, cyclopentanone-2-carboxylic acid nitrile, cyclohexanone-2-carboxymethyl ester and-carboxyethyl ester or cyclopentanone-2-carbonylmethyl. Particular preference is given to cyclopentanone-2-carboxymethyl ester and-carboxyethyl ester and cyclohexanone-2-carboxymethyl ester and carboxyethyl ester. Cyclopentanone systems are readily obtained industrially by the dieckmann condensation of dimethyl adipate or diethyl adipate. Cyclohexanone-2-carboxymethyl ester can be produced by hydrogenation of methyl salicylate.

The blocking of the polyurethane prepolymers using the cyclic ketones iii) is generally carried out in the presence of catalysts, the prepolymers being produced by reacting the components i) and ii). 0.8 to 1.2 mol of cyclic ketone iii) are used per equivalent of isocyanate groups present in the polyurethane prepolymer. Preferably, one equivalent of isocyanate groups from the polyurethane prepolymer to be capped are reacted with one equivalent of capping agent.

Suitable catalysts for promoting the capping reaction include alkali and alkaline earth metal bases, such as powdered sodium carbonate (soda). Depending on the cyclic ketone iii) used, it is also possible to use trisodium phosphate or amine bases such as1, 4-diazabicyclo [2.2.2]Octane). Carbonates of metals of the second subgroup of the periodic table are also suitable. Preferably, sodium or potassium carbonate is used. Optionally, the reaction of the cyclic ketone iii) with the polyurethane prepolymer containing NCO groups can be carried out in the presence of zinc salts as catalysts. The reaction using zinc 2-ethylhexanoate is particularly preferred. Mixtures of catalysts may also be used.

The catalysts are generally used in amounts of from 0.01 to 10% by weight, preferably from 0.05 to 3% by weight and more preferably from 0.07 to 1% by weight, based on the weight of the NCO-terminated prepolymer.

The reaction can be carried out at 0 ℃ to 140 ℃. Preferably in the temperature range of 15 ℃ to 90 ℃.

The capping can be carried out in the absence or presence of suitable solvents including known paint solvents such as butyl acetate, methoxypropyl acetate, methyl ethyl ketone, acetone, N-methyl-2-pyrrolidone, toluene, xylene, solvents such as those made by Exxon Chemie as aromatics (Solvesso)Solvent naphtha, and mixtures of the above solvents are provided.

In addition to the cyclic ketones iii), other known blocking agents can also be used for producing the blocked prepolymers A). The amount of cyclic ketone iii) is at least 30 wt%, preferably 50 wt% and more preferably 100 wt%, based on the weight of the capping agent. Suitable additional blocking agents include diisopropylamine, diethyl malonate, acetoacetate, acetoxime, butanone oxime, epsilon-caprolactam, 3, 5-dimethylpyrazole, 1, 2, 4-triazole, dimethyl-1, 2, 4-triazole, imidazole, or mixtures of these blocking agents.

The blocked polyurethane prepolymers A) obtained in this way have a blocked isocyanate group (calculated as NCO) content of generally from 0.1 to 20% by weight, preferably from 0.1 to 15.6% by weight and more preferably from 0.1 to 14% by weight, based on the weight of the blocked prepolymer. They are obviously suitable as starting components for the production of the reactive compositions according to the invention.

The OH-functional compounds of component B) are polyols in which the OH groups undergo activation by the beta-amine component. These mixed functional reactants include ethanolamine, methylethanolamine, dimethylethanolamine, diethanolamine, methyldiethanolamine, or multifunctional aminoethanol. Preferred mixed-function reactants are N, N, N ', N' -tetrakis (2-hydroxyethyl) ethylenediamine or N, N-bis (2-hydroxyethyl) amine.

To produce the reactive compositions according to the invention, the blocked polyurethane prepolymers A) are combined with the OH-functional reactants in such an amount that from 0.6 to 1.4, preferably from 0.8 to 1.2 and more preferably from 0.9 to 1.1 isocyanate-reactive groups are present per blocked and optionally free isocyanate group.

The reactive composition obtained may optionally comprise a suitable catalyst C) which makes it possible to carry out crosslinking at temperatures as low as room temperature or to promote crosslinking with the provision of heat.

Suitable catalysts C) include dibutyltin Dilaurate (DBTL), titanium 2-ethylhexanoate, titanium tetraisopropyl and other conventional titanium (IV) compounds, zirconium 2-ethylhexanoate and other conventional zirconium (IV) compounds, triethylaluminum, scandium triflate, yttrium 2-ethylhexanoate, yttrium triflate, lanthanum 2-ethylhexanoate, lanthanum triflate, cobalt 2-ethylhexanoate, copper 2-ethylhexanoate, indium triflate, gallium acetylacetonate, nickel acetylacetonate, lithium 2-ethylhexanoate, lithium triflate, sodium 2-ethylhexanoate, sodium acetate, sodium triflate, magnesium 2-ethylhexanoate, magnesium triflate, calcium 2-ethylhexanoate, calcium triflate, zinc 2-ethylhexanoate, zinc dithiocarbamates, zinc acetylacetonate, zinc tetramethylheptanedionate, sodium tetramethylheptanedionate, Zinc salicylate, zinc chloride and other zinc (II) compounds, bismuth 2-ethylhexanoate and bismuth acetate.

Preferred catalysts C) are zinc and bismuth compounds; zinc 2-ethylhexanoate and bismuth 2-ethylhexanoate are particularly preferred.

The catalyst is generally used in an amount of from 0.00001 to 2.0%, preferably from 0.05 to 1.0% and more preferably from 0.01 to 0.7%, based on the weight of the reactive composition.

The reactive composition may also comprise an additive D) known from the adhesive art as a formulation additive. Such additives include plasticizers, fillers, pigments, colorants, light stabilizers, antioxidants, thixotropic agents and adhesion promoters. Carbon black, precipitated silica, fumed silica, mineral chalk and precipitated chalk are examples of suitable fillers. Suitable plasticizers include phthalates, adipates, alkyl sulfonates of phenol, or phosphate esters. Fumed silica, polyamides, hydrogenated castor oil derivatives or polyvinyl chloride are examples of thixotropic agents.

Specifically, suitable desiccants include alkoxysilyl compounds such as ethyltrimethoxysilane, methyltrimethoxysilane, isobutyltrimethoxysilane, and hexadecyltrimethoxysilane; inorganic substances such as calcium oxide (CaO); and compounds containing an isocyanate group such as tosylisocyanate. Known functional silanes such as the aforementioned aminosilanes and N-aminoethyl-3-aminopropyltrimethoxy and/or N-aminoethyl-3-aminopropylmethyldimethoxysilane, epoxysilanes and/or mercaptosilanes may be used as adhesion promoters.

The production of the reactive compositions according to the invention from components A) and B) and optionally C) and/or D) is preferably carried out at temperatures of from-20 ℃ to 50 ℃ and more preferably at temperatures of from 0 ℃ to 40 ℃.

The reactive compositions according to the invention can be used for producing adhesives, sealants, coatings, insert parts or mouldings. The reactive compositions according to the invention are preferably used for producing adhesives.

The reactive compositions according to the invention are suitable for bonding a wide variety of materials to themselves or to one another, such as metals, plastics, glass, wood, leather and textiles.

The invention also provides a process for producing composite systems, in which the adherends to be bonded are coated on one side or on both sides with the reactive composition according to the invention.

The invention also provides composite systems comprising the reactive compositions according to the invention as coatings.

Depending on the chosen composition of the reactive compositions according to the invention, they can be cured within a few hours to a few days under ambient conditions, i.e. at a temperature of preferably-30 ℃ to 50 ℃ and a relative humidity of preferably 10% to 90%. Curing may additionally be promoted by raising the temperature above 50 c, preferably at a temperature of from about 60 c to about 100 c and more preferably at a temperature of from about 60 c to about 80 c, which may be desirable in practice. In this case, the reactive compositions according to the invention cure within minutes to hours, depending on the composition chosen.

Detailed Description

The invention is illustrated by the following examples:

examples

In the following examples, percentages are by weight.

The viscosity was measured at a test temperature of 23 ℃ using a Visco Tester VT550 rotational viscometer available from Thermo Haake, Harlsruhe, DE with an SV measuring cup and an SV DIN2 sensor.

The NCO content of the prepolymer and of the reaction mixture was determined in accordance with DIN EN 1242.

Starting compounds

Cyclopentanone-2-carboxyethyl ester (obtained from Fluka).

N, N' -tetrakis (2-hydroxyethyl) ethylenediamine (obtained from Fluka and used without any further purification).

Production of blocked polyurethane prepolymers from alpha-acidic cyclic ketones

End-capped polyurethane prepolymer a:

100.8g (0.30equiv) of a mixture of HDI and a polyether diol were added under a nitrogen atmosphere305; bayer Mateial science AG, Leverkusen, NCO content 12.5%, equivalent weight 336g/equiv) and 0.095g of zinc 2-ethylhexanoate were initially charged in a 250ml four-necked flask having a reflux condenser and an internal thermometer. 47.8g (0.306equiv) of cyclopentanone-2-carboxyethyl ester are then slowly added dropwise at room temperature, so that the reaction temperature does not exceed 40 ℃. The mixture can be cooled with a water bath if desired. When all the ester was added, stirring was continued at 40 ℃ until the NCO content of the reaction mixture reached zero. The blocked NCO content of the prepolymer was 8.52%.

Blocked polyurethane prepolymer B:

under a nitrogen atmosphere, 146.2g (0.15equiv) of a mixture of diisocyanatotoluene (TDI) and polyether glycol15；Bayer MaterialScience AG，Leverkusen，NCO4.3% NCO prepolymer prepared in equiv 974.5g/equiv) and 0.170g of zinc 2-ethylhexanoate were initially charged in a 250ml four-necked flask having a reflux condenser and an internal thermometer. 23.4g (0.15equiv) of cyclopentanone-2-carboxyethyl ester are then slowly added dropwise at room temperature, so that the reaction temperature does not exceed 40 ℃. The mixture can be cooled with a water bath if desired. When all the ester was added, stirring was continued at 40 ℃ until the NCO content of the reaction mixture reached zero. The prepolymer had a blocked NCO content of 3.71% and a viscosity of 48,900 mPas.

End-capped polyurethane prepolymer C:

1.2equiv of 2, 6-diisocyanatotoluene (TDI) and 348.1g of acetone were initially charged at a temperature of 50 ℃ in a 500ml three-necked flask. Then 150g of polyester diol was added1225; bayer MaterialScience AG, Leverkusen, hydroxyl number 225mg KOH/g substance corresponding to 6.52-7.12% hydroxyl content). The temperature is maintained so that it does not exceed 60 ℃. The mixture was allowed to react until the NCO content of the urethane stage (4.18%) was reached. It was then cooled to 45 ℃. 93.7g (0.6equiv) of cyclopentanone-2-carboxyethyl ester and 348g of zinc 2-ethylhexanoate were added. The mixture was allowed to react at 45-50 ℃ until zero NOC content was reached. The acetone was then distilled off. The blocked NCO content of the product obtained was 14.5%. The substance is a solid.

Blocked polyurethane prepolymer D:

193.93g (2.23equiv) of 2, 6-diisocyanatotoluene (TDI) were initially charged at a temperature of 60 ℃ in a nitrogen atmosphere in a 2000ml four-necked flask with stirrer, reflux condenser and internal thermometer. 1114.56g (1.11equiv) of polypropylene glycol were then added slowly through the addition funnelMaterialScience AG, Leverkusen, DE, hydroxyl number about 56mgKOH/g, nominal functionality of 2) such that the temperature does not exceed 6 deg.f during the addition0 ℃ is used. When all the polyether has been added, stirring is continued at 60 ℃ until the NCO content of the urethane stage (3.58%) is reached. The mixture was cooled to 50 ℃ and stirred with zinc 2-ethylhexanoate in an amount of 1.5 g. 191.5g (1.23equiv) of cyclopentanone-2-carboxyethyl ester are then added dropwise over the course of 30 minutes. The reaction was allowed to continue until the NOC level (approximately 10 hours) was zero. The mixture was then cooled to room temperature and the product decanted. The blocked NCO content of the prepolymer was 3.12%.

Blocked polyurethane prepolymer E:

111.26g (1.28equiv) of 2, 6-diisocyanatotoluene (TDI) were initially charged at a temperature of 60 ℃ in a nitrogen atmosphere in a 2000ml four-necked flask with stirrer, reflux condenser and internal thermometer. 1278.87g (0.64equiv) of polypropylene glycol were then added slowly through the addition funnelMaterialScience AG, Leverkusen, DE, hydroxyl value of about 28mgKOH/g, nominal functionality of 2) such that the temperature does not exceed 60 ℃ during the addition. When all the polyether was added, stirring was continued at 60 ℃ until the NCO content of the urethane stage (1.93%) was reached. The mixture is cooled to 50 ℃ and stirred with zinc 2-ethylhexanoate in an amount of 0.5 g. 109.87g (0.7equiv) of cyclopentanone-2-carboxyethyl ester are then added dropwise over the course of 30 minutes. The reaction was allowed to continue until the NOC level (approximately 10 hours) was zero. The mixture was then cooled to room temperature and the product decanted. The blocked NCO content of the prepolymer was 1.79%.

Application examples

Example 1

The blocked polyurethane prepolymer (component A) in the amount specified in Table 1 was mixed well with N, N, N ', N' -tetrakis (2-hydroxyethyl) ethylenediamine (component B) in the amount specified in the table, corresponding to a ratio of blocked NCO groups to OH groups of 1: 1. The mixture was then poured into a Teflon dish (diameter 8cm, depth: 1cm) and allowed to cure at room temperature. The measurement times for complete curing are listed in table 1.

Comparative example 1

The blocked polyurethane prepolymers (component A) in the amounts specified in Table 1 are mixed thoroughly with the polyamines in the amounts specified in the table, corresponding to a ratio of blocked NCO groups to OH groups of 1: 1. The mixture was then poured into a Teflon dish (diameter: 8cm, depth: 1cm) and allowed to cure at room temperature. The measured times to complete the cure are listed in table 2.

Example 2

The blocked polyurethane prepolymer (component A) in the amount specified in Table 1 was mixed well with N, N, N ', N' -tetrakis (2-hydroxyethyl) ethylenediamine (component B) in the amount specified in the table, corresponding to a ratio of blocked NCO groups to OH groups of 1: 1. The mixture was then placed on a Kofler stand and the time to complete curing at elevated temperature was measured. The measured times to complete the cure are listed in table 3.

Example 3

15g of blocked polyurethane prepolymer A and 1.797g of N, N, N ', N' -tetrakis (2-hydroxyethyl) ethylenediamine were weighed as reactants, corresponding to a ratio of blocked isocyanate groups to OH groups of 1: 1. 0.15g of zinc 2-ethylhexanoate was added as catalyst and blended by vigorous stirring. Beech boards (size 30X 120X 4.0mm, stored at 23 ℃ and 50% relative humidity) were bonded with unplasticized PVC film (Benecke-Kaliko, Benlitoli RTF, dimensions 30X 210X 0.4mm) using the above adhesive composition. The adhesive was applied to one side of beech wood (150 μm) using a grooved doctor blade. The adherend surface was about 30 x 90 mm. The bonded substrates were weighed together with a 2kg weight and left for 3 days to cure. The peel strength was then measured at a peel angle of 180 ° and a peel rate of 100 mm/min. Five individual measurements were made and then averaged. The peel strength was 3.7N/mm.

Example 4

15g of blocked polyurethane prepolymer C and 1.526g of N, N, N ', N' -tetrakis (2-hydroxyethyl) ethylenediamine were weighed out as reactants, corresponding to a ratio of blocked isocyanate groups to OH groups of 1: 1. 0.15g of zinc 2-ethylhexanoate was added as catalyst and blended by vigorous stirring. Beech boards (size 30X 120X 4.0mm, stored at 23 ℃ and 50% relative humidity) were bonded with unplasticized PVC film (Benecke-Kaliko, Benlitoli RTF, dimensions 30X 210X 0.4mm) using the above adhesive composition. The adhesive was applied to one side of beech wood (150 μm) using a grooved doctor blade. The adherend surface was about 30 x 90 mm. The bonded substrates were weighed together with a 2kg weight and left for 3 days to cure. The peel strength was then measured at a peel angle of 180 ° and a peel rate of 100 mm/min. Five individual measurements were made and then averaged. In both test parts, substrate fracture (tearing of the PVC film) occurred. In the three remaining individual measurements, the average value of the peel strength was 4.5N/mm.

Example 5

15g of blocked polyurethane prepolymer A and 1.797g of N, N, N ', N', -tetrakis (2-hydroxyethyl) ethylenediamine were weighed as reactants, corresponding to a ratio of blocked isocyanate groups to OH groups of 1: 1. 0.15g of zinc 2-ethylhexanoate was added as catalyst and blended by vigorous stirring. NBR test parts (30X 180mm) were bonded to one another using the above adhesive composition. The adhesive was applied to one side of beech wood (150 μm) using a grooved doctor blade. The adherend surface was about 30 x 90 mm. The bonded substrates were weighed together with a 4kg weight and left for 3 days to cure. The peel strength was then measured at a peel angle of 180 ° and a peel rate of 100 mm/min. Three single measurements were made and then averaged. The peel strength was 3.6N/mm.

TABLE 1Curing time of the reactive composition according to the invention at room temperature (about 25 ℃)

Component A)	The quantity [ g ]]	Component B)	The quantity [ g ]]	Curing time [ min ]]
					Blocked polyurethane prepolymers A	15	N, N, N ', N' -tetrakis (2-hydroxyethyl) ethylenediamine	1.797	1440
Blocked polyurethane prepolymers B	15	N, N, N ', N' -tetrakis (2-hydroxyethyl) ethylenediamine	0.799	1440
					Blocked polyurethane prepolymers D	15	N, N, N ', N' -tetrakis (2-hydroxyethyl) ethylenediamine	0632	2880
Blocked polyurethane prepolymers E	15	N, N, N ', N' -tetrakis (2-hydroxyethyl) ethylenediamine	0.348	2880

TABLE 2Comparative example Cure time at room temperature (about 25 ℃ C.)

Component A)	The quantity [ g ]]	Polyamines	The quantity [ g ]]	Curing time [ mim ]]
					Blocked polyurethane prepolymers D	15	4, 4' -Diaminodicyclohexylmethane (PACM20)	1.13	75
Blocked polyurethane prepolymers E	15	4, 4' -Diaminodicyclohexylmethane (PACM20)	0.68	90
					Blocked polyurethane prepolymers D	15	4, 4 '-diamino-3, 3' -dimethyldicyclohexylmethane (Laromin C260)	1.28	195
Blocked polyurethane prepolymers E	15	4, 4 '-diamino-3, 3' -dimethyldicyclohexylmethane (Laromine C260)	0.77	135

TABLE 3Curing time at elevated temperature of the reactive composition according to the invention

Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Claims (16)

1. A reactive composition comprising

A) One or more blocked polyurethane prepolymers having a blocked isocyanate group content of from 0.1 to 20 weight percent, calculated as NCO, and prepared from:

i) at least one aromatic, aliphatic, araliphatic and/or cycloaliphatic diisocyanate having a free NCO group content of 5 to 60% by weight,

ii) a polyol component comprising at least one polyester polyol, and/or at least one polyether polyol and/or at least one polycarbonate polyol,

iii) CH-acidic cyclic ketones corresponding to the general formula (I) as blocking agents

Wherein

X represents an electron-withdrawing group,

R¹and R²Independently of one another represent a radical H, C₁-C₂₀(cyclo) alkyl, C₆-C₂₄Aryl radical, C₁-C₂₀(cyclo) alkyl ester or amide, C₆-₂₄Aryl esters or amides, mixed aliphatic/aromatic radicals containing 1 to 24 carbon atoms which may also be part of a 4-to 8-membered ring and

n is an integer of 0 to 5, and

B) one or more OH functional compounds wherein the OH component undergoes activation by the β -position amine component.

2. The reactive composition of claim 1 wherein component i) comprises 1, 6-diisocyanatohexane, 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane, 4 '-diisocyanatodicyclohexylmethane, 2, 4-and/or 2, 6-diisocyanatotoluene, or 2, 2' -, 2, 4 '-and/or 4, 4' -diisocyanatodiphenylmethane.

3. The reactive composition of claim 1, wherein component iii) comprises cyclopentanone-2-carboxymethyl ester, cyclopentanone-2-carboxyethyl ester, cyclopentanone-2-carboxynitrile, cyclohexanone-2-carboxymethyl ester, cyclohexanone-2-carboxyethyl ester, or cyclopentanone-2-carbonylmethyl.

4. The reactive composition of claim 2, wherein component iii) comprises cyclopentanone-2-carboxymethyl ester, cyclopentanone-2-carboxyethyl ester, cyclopentanone-2-carboxynitrile, cyclohexanone-2-carboxymethyl ester, cyclohexanone-2-carboxyethyl ester, or cyclopentanone-2-carbonylmethyl.

5. The reactive composition of claim 1 wherein the polyurethane prepolymer a) has a blocked isocyanate group content of 0.1 to 15.6% by weight.

6. The reactive composition of claim 1 wherein component B) comprises ethanolamine, methylethanolamine, dimethylethanolamine, diethanolamine, methyldiethanolamine or a multifunctional aminoethanol.

7. The reactive composition of claim 2 wherein component B) comprises ethanolamine, methylethanolamine, dimethylethanolamine, diethanolamine, methyldiethanolamine or a multifunctional aminoethanol.

8. The reactive composition of claim 3 wherein component B) comprises ethanolamine, methylethanolamine, dimethylethanolamine, diethanolamine, methyldiethanolamine or a multifunctional aminoethanol.

9. The reactive composition of claim 4 wherein component B) comprises ethanolamine, methylethanolamine, dimethylethanolamine, diethanolamine, methyldiethanolamine or a multifunctional aminoethanol.

10. The reactive composition of claim 1 wherein component B) comprises N, N' -tetrakis (2-hydroxyethyl) ethylenediamine and/or N, N-bis (2-hydroxyethyl) amine.

11. The reactive composition of claim 2 wherein component B) comprises N, N' -tetrakis (2-hydroxyethyl) ethylenediamine and/or N, N-bis (2-hydroxyethyl) amine.

12. The reactive composition of claim 3 wherein component B) comprises N, N, N ', N' -tetrakis (2-hydroxyethyl) ethylenediamine and/or N, N-bis (2-hydroxyethyl) amine.

13. The reactive composition of claim 4 wherein component B) comprises N, N, N ', N' -tetrakis (2-hydroxyethyl) ethylenediamine and/or N, N-bis (2-hydroxyethyl) amine.

14. A process for the production of a reactive composition according to claim 1, comprising reacting the blocked polyurethane prepolymer a) with an OH-functional compound B) in such an amount that from 0.6 to 1.4 isocyanate-reactive groups are present per blocked and optionally free isocyanate group.

15. A composite system comprising two adherends bonded together by the reactive composition of claim 1.

16. The composite system of claim 15, wherein the adherent is metal, plastic, glass, wood, leather, or textile.