WO2015040097A1

WO2015040097A1 - Dual-cure adhesive composition

Info

Publication number: WO2015040097A1
Application number: PCT/EP2014/069860
Authority: WO
Inventors: Michael Schlumpf
Original assignee: Sika Technology Ag
Priority date: 2013-09-20
Filing date: 2014-09-18
Publication date: 2015-03-26

Abstract

The invention relates to the use of a complex compound, composed of methylenedianiline and a sodium salt, as a curing agent for moisture curing and possibly for heat curing in a heat-curable and moisture-curable adhesive composition, which adhesive composition comprises a prepolymer having isocyanate terminal groups composed of at least one polyisocyanate, which is selected from an aliphatic polyisocyanate and toluene diisocyanate, and at least one polyol. The adhesive composition can be cured both by heat and by moisture (dual cure), wherein the complex compound acts as a curing agent even if moisture is present. The composition is suitable in particular as a single-component adhesive, e.g, for vehicle construction.

Description

Dual-cure Adhesive Composition Description Technical Field

The invention relates to the use of a complex compound

Methylene dianiline and a sodium salt moisture curing agent in an adhesive composition comprising an isocyanate-terminated prepolymer, a method of bonding with the adhesive composition, the products obtainable therefrom, and the adhesive composition.

State of the art

Polyurethane compositions have been known for a long time and are used in many fields, e.g. as an adhesive. A distinction is made between one-component (1K) and two-component (2K) polyurethane (PUR) compositions. Further, in the 1K PUR compositions in which all the components are contained in one component, it is possible to distinguish between moisture-curing compositions which cure under the influence of atmospheric moisture and thermosetting compositions in which the curing is induced by heating.

The use of thermally labile hardeners based on a complex compound of methylenedianiline and a sodium salt for heat curing for isocyanate prepolymers is known.

EP 0255572 A1 describes a one-component adhesive and / or sealant composition which contains a polyurethane-based prepolymer and a heat activatable hardener, the stoichiometric ratio between prepolymer and hardener is selected so that only a partial crosslinking is possible when heated to temperatures of 60 to 180 ° C.

US 481441 1A1 describes compositions based on isocyanate-terminated polyether prepolymers and metal halide salt complexes of methylenedianiline.

WO 88/06165 describes heat and moisture-curing one-part polyurethane sealants and adhesives containing an isocyanate prepolymer of aromatic diisocyanates and polyols, a moisture curing catalyst and a blocked, heat activatable crosslinking agent such as a methylenedianiline / sodium chloride. Complex compound included.

WO 2008/136788 relates to one-component polyurethane systems which include

Isocyanate-terminated prepolymer of carbon ring-containing di- or triisocyanates and polyols, a metal salt complex of methylene dianiline and optionally an organic acid halide.

EP 0351728 A2 relates to a method for producing a sealing and

Adhesive strand using a moisture-curing

One-component polyurethane composition comprising an isocyanate prepolymer of aromatic diisocyanates, a moisture curing catalyst and a blocked activatable crosslinking agent, wherein

Solvent is injected into the mass to the crosslinking agent

release. The blocked crosslinking agent may be a complex of methylene dianiline and sodium chloride.

US 8217133 B2 describes a one-component polyurethane composition which contains a polyurethane prepolymer, a metal salt complex of methylenedianiline and an organic acid halide and forms an elastomer when heated to a temperature of 100 to 150 ° C. US 2010/25631 1 A1 relates to a hardener composition comprising a complex of methylenedianiline and a salt and less than 1000 ppm by weight

Methylene dianiline, and a polyurethane product obtained by reaction of a polyurethane prepolymer with the hardener composition at elevated temperature.

In the thermosetting compositions of the prior art containing thermolatent hardeners such as complexes of methylene dianiline, prepolymers based on aromatic polyisocyanates are commonly used. The products must be sufficiently heated directly after application, so that the thermolatent hardener can react. If the product is exposed to humidity for a longer period of time, the prepolymers begin to crosslink by means of a water / NCO reaction. The thermolatent hardener remains and can release toxic MDA. Since both hardening paths proceed through different mechanisms, different mechanical properties are obtained, i. There is no "dual-cure" system in the true sense.

Also known from the literature are systems based on surface-deactivated uretdione of toluene-2,4-diisocyanate, such as e.g. Desmodur ^ TT, based. Such systems are "pure" thermosetting systems, i. they can only be cured by heat and do not react with the humidity.

In the prior art thermosetting compositions, reaction with atmospheric humidity prior to use and incomplete thermal curing typically results in the thermolatent curing agent not being completely consumed, thereby causing toxic substances

can be released.

Presentation of the invention

The object was therefore to provide a composition which overcomes the aforementioned disadvantages and is suitable as a one-component adhesive composition. In particular, the task was in the Providing a composition that can be cured by both heat and humidity, wherein the mechanical properties of the cured product should be substantially or at least substantially independent of the type of cure. Furthermore, the composition should not release any toxic components even in the case of partial or complete reaction with atmospheric moisture. The cured product should also be free of toxic products regardless of the type of cure.

Furthermore, the composition should preferably allow rapid curing and have sufficient storage stability.

It has surprisingly been found that for certain prepolymers with isocyanate end groups per se known thermolatent hardener based on methylene dianiline-sodium salt complex compounds in the

Moisture hardening can act as a hardener.

Accordingly, the present invention relates to the use of a complex compound of methylenedianiline and a sodium salt as curing agent for moisture curing and optionally for heat curing in an adhesive composition comprising an isocyanate-terminated prepolymer of at least one polyisocyanate selected from aliphatic polyisocyanates and tolylene diisocyanate , and at least one polyol.

In the use according to the invention, it has surprisingly been found that the adhesive composition can be cured both with heat and with air humidity or with a combination of moisture curing and heat curing, whereby the same mechanical properties are obtained in both types of curing. An analytical study of the moisture-only cured sample also shows that virtually no toxic methylene dianiline is detectable.

This indicates that in both hardening paths the thermolatent hardener is consumed, ie there is a true "dual-cure" system. It Thus, the same mechanical properties are independent of the

Hardening conditions are achieved and toxic methylenedianiline is not released. The curing by humidity and possibly heat is also sufficiently fast. Furthermore, storage-stable adhesive compositions are obtained.

The invention will be explained in detail below.

Way to carry out the invention

"Poly" starting compound names designate substances containing two or more of the functional groups occurring in their name per molecule. The compounds may be monomeric, oligomeric or polymeric compounds. A polyol is e.g. a

Compound with two or more hydroxyl groups. A polyisocyanate is a compound having two or more isocyanate groups.

Isocyanate-reactive compounds are compounds having at least one isocyanate-reactive group capable of reacting with isocyanate groups to form a chemical bond. A one-component adhesive composition means a composition in which the components are present in one component. Typically, a one-component composition is at room temperature (e.g., 23 ° C) and, if a moisture-curable system is present, at least over a period of time (e.g., at least 1 day or at least 1 month) with the exclusion of humidity.

storage stable.

The term "storage-stable" refers to the property of a substance or a composition that it can be stored at room temperature in a suitable container for several weeks to 6 months and more, without being limited in its application or use properties by storage in changed to a degree relevant to their use. The average molecular weight here means number average molecular weight (Mn), which can be determined by gel permeation chromatography (GPC) against polystyrene standard. It is known that the complex compound of methylenedianiline (im

Hereafter referred to as MDA) and a sodium salt is thermolabile and can be used as a thermolatent hardener in heat curing. According to current knowledge, the MDA is blocked by the complex formation and is not reactive at room temperature. Only at elevated

Temperature, the release of MDA from the complex takes place, which can then act as a hardener. The temperature at which the complex compound can act as a hardening hardener depends on the particular complex compound and also on the particular adhesive composition. All the following details, in particular for the adhesive composition, the process and the uses, naturally apply to the use according to the invention, the process according to the invention, the products obtainable therefrom and the adhesive composition according to the invention in equal measure, even if not specifically indicated.

Under heat curing, the cure is carried out at a temperature of e.g. at least 80 ° C understood. The thermosetting is carried out in particular at a temperature at which the complex compound of MDA and a sodium salt thermally liberates MDA, so that the complex compound acts as a curing agent for the thermosetting.

During heat curing, an adhesive bead is simultaneously cured everywhere. In contrast, moisture-hardening involves a diffusion-controlled process

Hardening of the adhesive bead from outside to inside. Moisture hardening is understood as curing under moisture, in particular atmospheric moisture. The moisture curing is usually carried out at a temperature of not more than 40 ° C, whereby the moisture hardening usually at Room temperature is carried out, for example at temperatures below 35 ° C, for example at about 23 ° C.

So far, it was assumed that in moisture curing in such systems, the water from the moisture causes the crosslinking and thus curing. It has surprisingly been found that for the adhesive compositions used according to the invention, the complex compound of MDA and a sodium salt is also reactive in moisture curing and acts as a hardener, i. consumed in moisture curing. It is preferred that even in the case of moisture curing, the MDA contained in the complex compound is consumed by incorporation into the polymer or polymer network forming from the prepolymer.

Without wishing to be bound by theory, it is believed that the reactivity of the isocyanate groups in the prepolymer plays an essential role in whether the complex compound of MDA and a sodium salt can act as a hardener for moisture cure. Thus, the isocyanate groups in diphenylmethane-4,4'-diisocyanate (MDI) are highly reactive, while the isocyanate groups in toluene diisocyanate (TDI) and in aliphatic

Isocyanates have a lower reactivity. While in prepolymers based on TDI or aliphatic isocyanates, the complex compound can also act as a curing agent for moisture curing, this is at

Prepolymers based on MDI not possible. In the thermosetting and moisture-curable adhesive composition, a complex compound of MDA and a sodium salt is used as a curing agent for moisture curing and optionally for heat curing. Systems that are both thermosetting and moisture curable are also referred to as "dual cure" systems. It is preferred if the curing proceeds independently of the curing route via the same mechanism. The use of the complex compound according to the invention as curing agent for moisture curing has the advantage that the same mechanism of curing takes place both in the case of moisture curing and during temperature curing, which results in similar products in moisture curing, in temperature curing and in a combination of temperature curing and moisture curing and thus more uniform properties are obtained regardless of the curing method.

The adhesive composition of the present invention comprises an isocyanate-terminated prepolymer of at least one polyisocyanate selected from aliphatic polyisocyanates and toluene diisocyanate and at least one polyol. Mixtures of two or more such prepolymers may also be used. Isocyanate-terminated prepolymers are familiar to those skilled in the art. The prepolymer has at least two isocyanate end groups and preferably two isocyanate end groups. Via the isocyanate end groups, the prepolymer may be reacted by reaction with compounds containing isocyanate-reactive groups, e.g. Water, hydroxyl or amine, chain-extended or cross-linked, which causes the curing of the adhesive composition. The

As used herein, "curing" or "crosslinking" also includes chain extension reactions

In the isocyanate-terminated prepolymer of at least one

Polyisocyanate selected from aliphatic polyisocyanates and toluene diisocyanate and at least one polyol is a polyurethane prepolymer prepared by reacting at least one polyisocyanate selected from aliphatic polyisocyanates and toluene diisocyanate and at least one polyol. The person skilled in the art can readily prepare such prepolymers.

The reaction of the at least one polyol with at least one polyisocyanate selected from aliphatic polyisocyanates and toluene diisocyanate can be carried out, for example, by the polyol component and the polyisocyanate component by conventional methods, for example at temperatures of 50 to 100 ° C, optionally in the presence of a suitable catalyst, are reacted, wherein the polyisocyanate is used in stoichiometric excess. Optionally, additives such as solvents and / or plasticizers may be added to the reaction mixture as needed. As the reaction product arises

Prepolymer with isocyanate end groups. Solvents, if used, can be removed again after the reaction. Plasticizers, if used, may preferably remain in the product obtained.

The polyisocyanate for forming the prepolymer having isocyanate end groups is a polyisocyanate selected from aliphatic polyisocyanates and tolylene diisocyanate. It is possible to use such a polyisocyanate or two or more such polyisocyanates. Preference is given to an aliphatic polyisocyanate.

An aliphatic polyisocyanate is an aliphatic compound which

has at least two isocyanate groups. Preference is given to an aliphatic diisocyanate. It may be an acyclic or cyclic aliphatic polyisocyanate, with a cyclic aliphatic polyisocyanate being preferred. Preferably, it is a saturated aliphatic polyisocyanate. These polyisocyanates are known and commercially available.

Examples of a suitable aliphatic polyisocyanate are 1,6-hexamethylene diisocyanate, 2,2,4- and 2,4,4-trimethyl-1,6-hexamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane

1,3- and 1,4-diisocyanate and mixtures of these isomers, isophorone diisocyanate (IPDI, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane),

2,4- and 2,6-hexahydrotoluylene diisocyanate, hexahydro-1,3-and -1,4-phenyl-diisocyanate, perhydro-2,4'- and -4,4'-diphenylmethane diisocyanate, and

Mixtures of the aforementioned isocyanates. Particularly preferred

Isophorone diisocyanate (IPDI) and hexamethylene-1,6-diisocyanate (HDI). The tolylene diisocyanate (TDI) may be 2,4-tolylene diisocyanate, tolylene 2,6-diisocyanate and mixtures of these isomers. TDI is also referred to as toluene diisocyanate. TDI is commercially available, such as Desmodur ^® T80 from Bayer AG or Lupranat® ^® T80 by BASF AG.

To form the isocyanate-terminated prepolymer, the at least one polyisocyanate selected from aliphatic polyisocyanates and TDI is reacted with one or more polyols. All polyols which are customary for polyurethane chemistry can be used. Suitable polyols are commercially available in great variety.

The polyol preferably has an average molecular weight or, if it is a non-polymeric polyol, a molecular weight of 250 to 30,000 g / mol and preferably from 400 to 20,000 g / mol. The polyol also preferably has an average OH functionality in the range of 1.6 to 3. It is understood that polymeric compounds may also contain substances formed from side reactions, e.g. only one or none

Have hydroxy group. As polyols, for example, the following commercially available polyols or mixtures thereof can be used: a) Polyoxyalkylenpolyole, also called polyether polyols or oligoetherols, which polymerization of ethylene oxide, 1, 2-propylene oxide, 1, 2 or 2,3-butylene oxide, oxetane, tetrahydrofuran or Mixtures thereof are, possibly polymerized with the aid of a starter molecule having two or more active hydrogen atoms such as water, ammonia or compounds having several OH or NH groups such as 1, 2-ethanediol, 1, 2 and 1, 3-propanediol, Neopentyl glycol, diethylene glycol,

Triethylene glycol, the isomeric dipropylene glycols and tripropylene glycols, the isomeric butanediols, pentanediols, hexanediols, heptanediols, octanediols, nonanediols, decanediols, undecanediols, 1,3- and 1,4-cyclohexanedimethanol, bisphenol A, hydrogenated bisphenol A, 1, 1, 1 - Trimethylolethane, 1, 1, 1 - Trimethylolpropane, glycerol, aniline, and mixtures of the aforementioned compounds. Both polyoxyalkylene polyols having a low degree of unsaturation (measured according to ASTM D-2849-69 and expressed in milliequivalents of unsaturation per gram of polyol (mEq / g)) prepared, for example, by means of so-called double metal cyanide complex catalysts (DMC) can be used. Catalysts), as well as polyoxyalkylene polyols having a higher degree of unsaturation, for example prepared with the aid of anionic catalysts such as NaOH, KOH, CsOH or Alkalialkoho- laten.

Particularly suitable are polyoxyalkylenediols or polyoxyalkylenetriols, in particular polyoxyethylene and polyoxypropylene di- and triols. Especially suitable are polyoxyalkylenediols and -triols having a degree of unsaturation of less than 0.02 meq / g and having an average molecular weight in the range from 1000 to 30,000 g / mol, and also polyoxypropylenediols and -triols having an average molecular weight of from 400 to 8,000 g / mol.

Also particularly suitable are so-called ethylene oxide-terminated (oxide-endcapped) polyoxypropylene polyols, the latter being specific polyoxypropylene-polyoxyethylene polyols obtained, for example, by further alkoxylating pure polyoxypropylene polyols, especially polyoxypropylene diols and triols, upon completion of the polypropoxylation reaction with ethylene oxide b) Styrene-acrylonitrile or acrylonitrile-methyl methacrylate-grafted polyether polyols c) Polyester polyols, also called oligoesterols, prepared by known processes, in particular the polycondensation of hydroxycarboxylic acids or the polycondensation of aliphatic and / or aromatic Polycarboxylic acids with dihydric or polyhydric alcohols. Particularly suitable polyester polyols are those which are prepared from dihydric to trihydric, especially dihydric, alcohols, for example ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl -1, 5-hexanediol, 1, 6-hexanediol, 1, 8-octanediol, 1, 10-decanediol, 1, 12-dodecanediol, 1, 12-hydroxystearyl alcohol, 1, 4-cyclohexanedimethanol, dimer fatty acid diol

(Dimerdiol), hydroxypivalate neopentyl glycol ester, glycerol, 1,1,1-trimethylolpropane or mixtures of the abovementioned alcohols, with organic di- or tricarboxylic acids, in particular dicarboxylic acids, or their anhydrides or esters, such as succinic acid, glutaric acid, adipic acid, trimethyladipic acid, suberic acid, azelaic acid , Sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, dinner fatty acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, dimethyl terephthalate, hexahydrophthalic acid, trimellitic acid and trimellitic anhydride, or mixtures of the abovementioned acids, as well as polyester polyols from lactones such as ε-caprolactone and starters such as those mentioned above di- or trihydric alcohols. d) polycarbonate polyols, as they are, for example, by reacting the abovementioned - used for the construction of the polyester polyols - alcohols with Dialkylcarbo- naten, diaryl carbonates or phosgene accessible. e) block copolymers bearing at least two hydroxyl groups, which have at least two different blocks having a polyether, polyester and / or polycarbonate structure of the type described above, in particular polyetherpolyesterpolyols. f) polyacrylate and polymethacrylate polyols. g) polyhydroxy-functional fats and oils, for example natural fats and oils, in particular castor oil; or by chemical modification of natural fats and oils - so-called oleochemical - polyols, for example by epoxidation of unsaturated oils and subsequent Ring opening with epoxy or polyoxypolyethers obtained with carboxylic acids or alcohols, or polyols obtained by hydroformylation and hydrogenation of unsaturated oils; or from natural fats and oils by degradation processes such as alcoholysis or ozonolysis and subsequent chemical linkage, for example by transesterification or dimerization, of the resulting degradation products or derivatives thereof obtained polyols. Suitable degradation products of natural fats and oils are in particular fatty acids and fatty alcohols and fatty acid esters, in particular the methyl esters (FAME), which can be derivatized for example by hydroformylation and hydrogenation to hydroxy fatty acid esters. h) polyhydrocarbyl polyols, also called oligohydrocarbonols, such as, for example, polyhydroxy-functional polyolefins, polyisobutylenes, polyisoprenes; polyhydroxy-functional ethylene-propylene, ethylene-butylene or ethylene-propylene-diene copolymers; polyhydroxy-functional polymers of dienes, in particular of 1, 3-butadiene, which may in particular also be prepared from anionic polymerization; polyhydroxy-functional copolymers of dienes such as 1,3-butadiene or diene mixtures and vinyl monomers such as styrene, acrylonitrile, vinyl chloride, vinyl acetate, vinyl alcohol, isobutylene and isoprene, for example polyhydroxy-functional acrylo nitrile / butadiene copolymers, such as, for example, epoxides or aminoalcohols and carboxyl-terminated acrylonitrile / butadiene copolymers; and hydrogenated polyhydroxy-functional polymers or copolymers of dienes.

The adhesive composition further comprises a complex of methylene dianiline and a sodium salt. The complex compound is known as a thermolatent hardener. The complex compound of methylene dianiline and a sodium salt is used in the adhesive composition according to the invention as a curing agent for moisture curing and optionally as a curing agent for heat curing. Methylenedianil in (MDA) is especially 4,4'-methylenedianiline and is sometimes referred to as 4,4'-diaminodiphenylmethane. Examples of the sodium salt are sodium chloride, sodium bromide, sodium iodide, sodium nitrite and sodium cyanide or mixtures of two or more of these sodium salts, with sodium chloride being particularly preferred. These complexes are known in the art and commercially available. Often, they are sold in the form of a dispersion in a plasticizer.

In these complex compounds, the MDA is complexed with the sodium salt. According to the literature, e.g. in the case of the complex compound of MDA and NaCl, the MDA is incorporated into an expanded sodium chloride lattice. The

Stoichiometric composition of this complex is given in the literature as (MDA) ₃ NaCl. Small amounts of MDA, for example less than 1 wt .-%, preferably less than 0.1 wt .-%, may be present in the complex compound freely. Upon heating to a certain temperature depending on the particular complex compound and the composition in which it is contained, the complex compound thermally dissociates and MDA is released. The released MDA can then react with the prepolymer to cure the composition.

According to the invention, the complex compound of methylenedianiline and a sodium salt also acts as a curing agent in moisture curing without requiring thermal dissociation. As a result, the complex compound, in particular the MDA contained therein, is also consumed in the case of moisture hardening. Preferably, in moisture curing, the MDA contained in the complex compound is consumed by incorporation into the polymer or polymer network forming from the prepolymer.

Complex compounds of MDA and sodium chloride include Chemtura Corporation, USA, as Caytur ^® 31 ^® 31 Caytur DA and Duracure ^® C3-LF available. Caytur ^® 31 is an approximately 47 wt .-% dispersion of MDA / NaCl complex in dioctylphthalate (DOP), the content of free MDA is greater than 0.1%. Caytur ^® 31 DA differs from Caytur ^® 31 in the use of Dioctyl adipate (DOA) instead of DOP. Duracure ^® C3-LF is a about 44% by weight dispersion of MDA / NaCl complex in dioctyl adipate, the content of free MDA is less than 0.1%. In an optional and preferred embodiment, the adhesive composition further comprises an acid. With the aid of an acid as a catalyst, the reaction with moisture, in particular humidity, can be accelerated to harden. Suitable acids are inorganic or organic acids. Preferred are carboxylic acids and sulfonic acids and derivatives of carboxylic acids and sulfonic acids. Examples of suitable acids are organic carboxylic acids such as benzoic acid, salicylic acid or 2-nitrobenzoic acid, organic carboxylic anhydrides such as phthalic anhydride, hexahydrophthalic anhydride and hexahydromethylphthalic anhydride, silyl esters of organic carboxylic acids, organic

Sulfonic acids such as methanesulfonic acid, p-toluenesulfonic acid or 4-dodecyl-benzenesulfonic acid, sulfonic acid esters, other organic or inorganic acids, or mixtures of the aforementioned acids and acid esters.

In an optional embodiment, the adhesive composition may further comprise an aromatic isocyanate compound. aromatic

Isocyanates help to stabilize the composition so that it is stable for several weeks at room temperature (e.g., 23 ° C). Of the aromatic isocyanates, preferably only relatively small amounts are included in the composition.

The aromatic isocyanate is preferably an aromatic polyisocyanate. Mixtures of two or more aromatic isocyanates may also be used. An aromatic isocyanate is an aromatic compound having at least one isocyanate group, preferably having at least two isocyanate groups. It is possible to use, for example, all aromatic isocyanates or polyisocyanates which are customary in polyurethane chemistry and are commercially available. Examples of aromatic isocyanates are 2,4- and 2,6-toluene diisocyanate (TDI) and mixtures of these isomers, 4,4'-diphenylmethane diisocyanate (MDI), the positionally isomeric 2,2'-MDI and 2,4'-MDI and mixtures these isomers, technical and modified MDI, 1, 3 and 1, 4-phenylene diisocyanate,

Naphthalene diisocyanate, 1, 3 and 1, 4-tetramethylxylylene diisocyanate, and mixtures of the aforementioned isocyanates.

In a preferred embodiment, the adhesive composition may comprise an acid, e.g. a carboxylic acid such as salicylic acid as above

and containing an aromatic isocyanate compound as described above. This combination improves storage stability.

Optionally, the adhesive composition according to the invention may further comprise one or more other auxiliaries and additives conventionally used in the polyurethane industry as additives.

Examples of such additives are plasticizers, e.g. Esters of organic carboxylic acids or their anhydrides, phthalates, e.g. Dioctyl phthalate or diisodecyl phthalate, adipates, e.g. Dioctyl adipate, sebacates, organic phosphoric and sulfonic acid esters and polybutenes; Solvents; inorganic and organic fillers, e.g. ground or precipitated calcium carbonates, Russian, kaolins, aluminas, silicas and PVC powders; Fibers, for example of polyethylene; pigments; Rheology modifier, e.g. Thickeners such as urea compounds, polyamide waxes, bentonites or fumed silicas; Adhesion promoters, in particular silanes, such as epoxysilanes, vinylsilanes and isocyanatosilanes; Desiccant, e.g. p-tosyl isocyanate and other reactive isocyanates, orthoformic acid esters, calcium oxide or molecular sieves;

Stabilizers against heat, light and UV radiation; flame-retarding substances; surfactants such as wetting agents, leveling agents, deaerators or defoamers; and fungicides or fungal growth inhibiting substances. The additives can be added in suitable amounts in the customary manner if required and depending on the application. In general, it is preferred that the adhesive composition contains at least one plasticizer and / or at least one filler.

The proportions of the ingredients in the adhesive composition can vary widely depending on the ingredients used and the purpose for which they are used. The following quantities for convenient and preferred embodiments are based on the total weight of the adhesive composition.

The level of isocyanate-terminated prepolymer of at least one polyisocyanate selected from aliphatic polyisocyanates and tolylene diisocyanate, and at least one polyol in the adhesive composition can be e.g. in the range of 10 to 90 wt .-%, and preferably from 20 to 45 wt .-%.

The complex compound is preferably used in substoichiometric amounts based on the amine groups of the complex compound to the isocyanate groups of the prepolymer, so that a part of the crosslinking of the prepolymer takes place via moisture. The proportion of the complex compound of methylene dianiline and a sodium salt in the adhesive composition depends on the amount of the adhesive composition

and containing isocyanate terminated prepolymer, and may be e.g. be chosen so that the molar ratio of isocyanate groups to

Amine groups in the adhesive composition in the range of 2: 1 to 1: 1, preferably 1, 5: 1 to 1: 1 and more preferably from 1, 1: 1 to 1: 1. The amine groups refer to those of methylenedianiline in the

Complex compound.

For example, if an acid is contained in the adhesive composition, the amount of acid in the adhesive composition may be in the range of 0.01 to 1% by weight and preferably 0.05 to 0.1% by weight. If in the In the adhesive composition containing an aromatic isocyanate compound, the proportion of the aromatic isocyanate compound in the adhesive composition may be, for example, in the range of 0.1 to 5% by weight, and preferably 0.5 to 2% by weight.

As stated, in an optional and preferred embodiment, the adhesive composition contains the acid and the aromatic isocyanate compound, e.g. 0.01 to 1 wt .-%, preferably 0.05 to 0.1 wt .-% acid, and 0.1 to 5 wt .-%, preferably 0.5 to 2 wt .-%, of aromatic isocyanate compound are included , Thereby, the storage stability of the composition can be improved.

The prepolymer and the complex compound as well as the optionally used acids, aromatic isocyanates and other additives can be mixed together in any order to obtain the adhesive composition. Some components, such as the complex compound and / or the optional acid can e.g. also be added as a mixture with a plasticizer. The mixing can at

Room temperature (e.g., 23 ° C). It can e.g. also be carried out partially or completely at slightly elevated temperature for easier homogenization or dispersion. As mixing devices, it is possible to use all mixing devices known in this field. The viscosity can be arbitrarily set in consideration of the intended use, e.g. For example, the adhesive composition may be pasty and preferably have pseudoplastic properties.

It is a thermosetting and moisture curable adhesive composition, ie it is a dual cure adhesive composition. It may be a multicomponent, eg two-component adhesive composition, but it is preferably a one-component adhesive composition. The invention also relates to a method for curing an adhesive composition, which can be cured by exposure to moisture and / or heat, wherein the adhesive composition A) obtain an isocyanate-functional prepolymer from the reaction of at least one polyisocyanate with at least one polyol, wherein the Polyisocyanate is selected from an aliphatic polyisocyanate and TDI, and B) at least one complex of methylenedianiline and a

Sodium salt, wherein the adhesive composition cures at least partially by the action of moisture, and in the cured adhesive composition, no free MDA, as determined by the method GC / MS given below, can be detected, or the cured adhesive composition has a content of free Methylene dianiline of <0.1 wt .-%, determined by the method GC / FID given below.

The invention also relates to a method for bonding adherends with the thermosetting and moisture-curable adhesive composition of the present invention as described above

a) applying the thermosetting and moisture-curable adhesive composition to one or both adherend surfaces to be bonded,

b) contacting the adherend surfaces to be bonded and

c) curing the adhesive composition in moisture

Moisture hardening and, if necessary, heat by heat curing.

The parts to be joined or the joining part surfaces to be bonded can be made of any material, whereby the joining part surfaces to be bonded can be made of the same material or of different materials.

Examples of suitable materials include metal including metal alloys, glass, plastic, ceramics, textiles or painted components.

Application of the thermosetting and moisture-curable adhesive composition to one or both adherend surfaces to be bonded may occur customary, known to those skilled manner. The joining part surfaces to be bonded are then contacted, with the joining part surfaces to be glued being optionally pressed against one another. The curing of the adhesive composition is then carried out at humidity, in particular at atmospheric humidity, by moisture hardening and optionally by heat by heat curing. The adhesive composition can only be cured by moisture curing. The complex compound of MDA and a sodium salt acts as a hardener for moisture curing.

In a preferred embodiment, the curing is carried out in part by heat by heat curing and partly by moisture by moisture curing, with a pre-cure on heat and then a post-cure in moisture is particularly preferred. If the curing takes place partly by moisture hardening and partly by heat curing, it is preferred that, in the case of a moisture curing subsequent to a heat curing, the remaining complex compound of MDA and a sodium salt contained in the composition is substantially or completely consumed.

The temperature used for the optionally used partial heat curing can vary within wide ranges, depending on the adhesive composition used, the desired degree of crosslinking and the duration of the heat curing. The thermosetting may e.g. be carried out at temperatures in the range of 80 to 160 ° C. The duration of the heat curing may e.g. ranging from 1 to 120 minutes. Subsequently, the complete curing by moisture curing can take place, wherein the duration naturally depends on the degree of crosslinking achieved during the heat curing.

Other sequences when performing a combination of thermosetting and moisture curing are also possible but less preferred, eg first a moisture hardening and a subsequent heat curing for complete curing or first a moisture hardening, a subsequent heat curing and finally a moisture curing for complete curing.

Also in the embodiments where both moisture curing and heat curing are performed, the complex compound of MDA and a sodium salt acts as a hardener for moisture curing and, in addition, as a hardener for heat curing. It is preferred that in the case of moisture-hardening and, if heat-cured, the methylene-dianiline contained in the complex compound is consumed by incorporation into the polymer or polymer network forming from the prepolymer, even on heat-curing. The invention also relates to an article comprising adherends and a cured adhesive composition as an adhesive bond of the adherends obtainable by the method of the invention. It is preferable for the article that the content of MDA in the cured adhesive composition is not more than 0.1% by weight based on

Total weight of the cured composition. The MDA content in the cured adhesive composition includes any MDA and MDA present from the complex compound of MDA and a sodium salt (free MDA). The MDA content does not include MDA incorporated by reaction into the polymer or polymer network formed from the prepolymer. The MDA content can be determined by GC / FID, HPLC or GC / MS as explained below in the experimental section. Unless otherwise stated, MDA values in the cured adhesive composition are based on the value determined by the GC / FID method.

Accordingly, the invention also relates to a thermosetting and

moisture curable adhesive composition comprising a) an isocyanate-terminated prepolymer of at least one polyisocyanate selected from an aliphatic polyisocyanate and tolylene diisocyanate, and at least one polyol and b) a complex compound of methylenedianiline and a sodium salt hardener for moisture curing and optionally for heat curing.

All the above details and explanations of the thermosetting and moisture-curable adhesive composition, e.g. with regard to suitable components etc., apply accordingly.

The adhesive composition, preferably the one-component

Adhesive composition, is generally suitable for bonding one or more materials of the same or different nature and in particular for bonding in vehicle construction or vehicle repair.

In the following the invention will be further explained by examples, which are not intended to limit the invention in any way.

Examples

Measuring Methods The properties tensile strength, elongation and modulus of elasticity 0.5-5% were determined according to DIN EN ISO 527.

The skin formation time (time to tack-free time) as a measure of the cure rate became 23 ° C ("RT") and 50% more relative

Humidity determined. To determine the skinning time, a small portion of the space temperature-warm coating composition was applied to cardboard in a layer thickness of about 2 mm and the time it took for the lightly tapping the surface of the coating composition For the first time, no residues were left on the pipette by means of a pipette made of LDPE.

MDA content using method GC / MS

500 mg of sample were cut into small pieces and combined with 4 mL of ethyl acetate. It was extracted for 18 h at room temperature (300 rpm). The extract was filtered with a 0.2 μηη PTFE membrane and used directly for analysis under the following conditions.

Instrument: ThermoFinnigan Trace GC DSQ 2

Column: Optima-5-MS; 30 m by 0.25 mm; Film thickness 0.5 μηη

Tem peratu rprog ram m: 0 min at 60 ° C, with 15 ° C / min from 60 ° C to 320 ° C,

15 min at 320 ° C

Carrier gas: helium, 1, 5 mL / min, constant flow

Injector temperature: 250 ° C

Split: 25: 1

Injection volume: 1 μΙ_

Interface temperature: 250 ° C

Detection: MS; 29 - 520 amu

Source temperature: 230 ° C

The volatiles were quantified using the area percent method (100% method). This semi-quantitative method does not take into account the different response factors of the individual substances, i. it is to be expected with a relative measurement uncertainty of approx. 20%. With this method no statement about the absolute quantity can be made.

MDA content by method GC / FID

1.2 g of the sample were cut into small pieces and treated with 10 mL of ethyl acetate (containing 0.4 mg / L phenyldecane as internal standard). It was during 18 h at room temperature (300 rev / min) extracted. The extract was filtered with a 0.2 μηη PTFE membrane and used directly for analysis under the following conditions.

Instrument: Agilent 7890N

Column: Optima-5-amine; 30 m by 0.25 mm; Film thickness 0.5 μηη

Tem peratu rprog ram m: 2 min at 60 ° C, at 15 ° C / min to 290 ° C, 5 min at

290 ° C

Carrier gas: helium, 1, 5 mL / min, constant flow

Injector temperature: 250 ° C

Injection volume: 1 μΙ_

Split: 25: 1

Detection: flame ionization detector (FID); 300 ° C An external 7-point calibration with MDA in ethyl acetate (containing 0.4 mg / mL phenyldecane as internal standard) was performed. From the sample containing MDA, a triple determination was made.

MDA content by HPLC / PDA method

The sample was cut into small pieces and about 100 mg was weighed into pills. 5 ml of acetonitrile were added by pipette. For 30 minutes, the sample was extracted by means of ultrasonic bath and vortex. After filtration through a 0.2μηη nylon membrane, the clear solution was analyzed by HPLC / PDA under the following conditions.

System: HPLC Varian

Column: Gemini C18, 75 x 4.6 mm 1 10 A 3 pm

Oven: 30 ° C

Mobile Phase A Deionized water

Mobile Phase B ACN

Mobile Phase C MeOH Gradient: Time Flow% A% B% C Relay

Start 1.0 80 5 15 on

2.00 1, 0 80 5 15

8.00 1, 0 5 5 90

1 1, 00 1, 0 5 5 90

12.00 1, 0 80 5 15

Flow rate: 1 ml / min

Detection: UV 240nm

Injection volume: 10 μί

The following chemicals were used:

Acetonitrile (ACN) of HPLC grade

Deionized water Elga (R> 18.2 MegaOh

Methanol (MeOH) Lichrosolv

4,4'-methylenedianiline MDA (CAS 101 -77-9)

To prepare standards, approximately 30 mg of MDA was weighed into a 20 ml volumetric flask, ACN was added to the mark. The solution was homogenized with vortex and ultrasound and made into a standard series in ACN as follows.

Standards volume of flask c ^* [mg / ml] in ACN

μΙ ml

STD 1 50 10 5

STD 2 100 10 10

STD 3 200 10 50

STD 4 500 10 100

STD 5 1000 10 200

raw materials

The following starting materials were used for the production of adhesives:

Voranol CP 4755 ^® (Dow polyether triol, CAS no. 9082-00-2

Chemical) Desmodur ^® MC 44 (Bayer) monomeric diphenylmethane-4,4'-diisocyanate (MDI)

Desmodur ^® T80 (Bayer) 2,4- and 2,6-toluene diisocyanate (TDI) in

Ratio of 80:20

Desmodur ^® 1 (Bayer) isophorone diisocyanate (IPDI)

Desmodur ^® H (Bayer) hexamethylene-1, 6-diisocyanate (HDI)

Coscat 83 ^® (Vertellus Organobismuth catalyst

Specialties Inc.)

DIDP diisodecyl phthalate (plasticizer)

Monarch ^® 570 (Cabot Corp.) Carbon black pigment (filler)

White Tex ^® aluminum silicate (filler)

Aerosil ^® R972 (Evonik Industries hydrophobicized with dimethyldichlorosilane) fumed silica (filler)

Duracure ^® C3 LF (Chemtura about 44% wt.% Tris (4,4'-diamino-Corp.) diphenylmethane) sodium chloride in

Dioctyl adipate, (free MDA <0.1% by weight)

Examples 1-4 The components listed in the table below were mixed in the proportions indicated (parts by weight) to prepare a formulation which was then reacted in a conventional manner to prepare prepolymers 1 to 4 (Prep.

Prep. 1 prep. 2 prep. 3 prep. 4

Voranol CP ^® 4755 68.8 71 8 69.8 72.05

DIDP 19,995 19,995 19,99 19,99

Desmodur ^® MC 44 1 1 2

Desmodur ^® T80 8.2

Desmodur ^® I 10.2

Desmodur ^® H 7.95

Coscat ^® 83 0.005 0.005 0.01 0.01

Total 100 100 100 100

NCO / OH ^* 2.05 2.05 2.05 2.05

NCO measured

[% By weight] ^** 2.46 2.59 2.49 2.45 ^* molar ratio of NCO groups to OH groups in the formulation

* ^* NCO groups in the prepolymer, determined by titration

The prepolymers 1 to 4 prepared above were mixed with the in

Components listed in the following table (parts by weight) mixed in order to produce adhesives (Examples 1 b 4).

* Comparative Example

** based on isocyanate groups in the prepolymer

*** Based on the adhesive composition determined from the content of MDA in the complex compound

Adhesive films of the resulting adhesives (Example 1-4) were each cured under the following conditions, RT at 23 ° C / 50% relative

Moisture (rh) means: a) at 120 ° C for 8 minutes and then at RT for 1 day; b) at 120 ° C for 8 minutes and then at RT for 7 days; c) 7 days at RT. The thus cured films were tested for mechanical properties. The results are given in the table below. Eg hardening tensile strength elongation at break [%] modulus of elasticity 0.5-5%

[MPa] [MPa]

1 ^* 8 '120 ° C 10.2 439 8.9

1 d RT

8 '120 ° C 9.4 351 10.0 7d RT

7d RT 8.3 484 5.4

2 8 '120 ° C 7.3 477 2.6

1 d RT

8 '120 ° C 8.5 374 4.8 7d RT

7d RT 7.8 401 4.5

3 8 '120 ° C 5.4 532 2.3

1 d RT

8 '120 ° C 6.7 561 2.9 7d RT

7d RT 7.3 655 2.8

4 8 '120 ° C 7.4 446 4.7

1 d RT

8 '120 ° C 8.6 438 6.0 7d RT

7d RT 8.5 414 5.4

^* Comparative Example

In Examples 2 to 4, the variation of the mechanical properties as a function of the curing conditions is significantly lower than in Example 1 (Comparative Example).

Furthermore, adhesive films of the adhesives obtained (Examples 1 -4) were each cured a) at RT and b) at 120 ° C., RT at 23 ° C./50% relative humidity (rh). The MDA content in the cured samples was determined semi-quantitatively by GC / MS. This method can be used to determine whether MDA is detectable or not. A quantitative determination of MDA content is thus not possible. The results are shown in the following table.

^* Comparative Example

Only in the RT-cured sample of Example 1 could MDA be detected. In all other samples no MDA was detectable. The MDA content in the RT-cured sample of Example 1 was quantified by GC / FID and HPLC. An MDA concentration of 1.17 ± 0.06% by weight, determined by GC / FID, or of 1.29 ± 0.06% by weight, determined by HPLC, resulted in this sample. The results of the two measurement methods are comparable.

Claims

claims

Use of a complex compound of methylene dianiline and a sodium salt hardening agent for moisture curing and optionally for heat curing in a thermosetting and moisture curable adhesive composition comprising a prepolymer having isocyanate end groups of at least one polyisocyanate selected from an aliphatic polyisocyanate and tolylene diisocyanate , and at least one polyol.

Use according to claim 1, wherein in the moisture-curing, the methylene dianiline contained in the complex compound is consumed by incorporation into the polymer or polymer network constituting the prepolymer.

Use according to claim 1 or claim 2, wherein the polyisocyanate for the prepolymer is an aliphatic polyisocyanate, preferably isophorone diisocyanate or hexamethylene-1,6-diisocyanate.

Use according to any one of claims 1 to 3, wherein the

Adhesive composition further comprises an acid, in particular a carboxylic acid, and / or the adhesive composition further comprises an aromatic isocyanate compound.

Use according to any one of claims 1 to 4, wherein the molar ratio of isocyanate groups to amino groups in the adhesive composition is in the range of 2: 1 to 1: 1, preferably 1: 5: 1 to 1: 1.

Use according to any one of claims 1 to 5, wherein the

Adhesive composition is a one-component adhesive composition. Use according to any one of claims 1 to 6 for the

Bonding in vehicle construction or vehicle repair.

A method of curing an adhesive composition which can be cured by the action of moisture and / or heat, wherein the adhesive composition

A) an isocyanate-functional prepolymer obtained from the

Reacting at least one polyisocyanate with at least one polyol, wherein the polyisocyanate is selected from an aliphatic polyisocyanate and tolylene diisocyanate, and

B) at least one complex compound of methylenedianiline and a sodium salt,

comprises, characterized in that

the adhesive composition cures at least partially by the action of moisture,

and that no free MDA, determined by means of the method of measurement "Method GC / MS" given in the description, can be detected in the cured adhesive composition,

or that the cured adhesive composition has a content of free methylene dianiline of <0.1% by weight, determined by means of the method of measurement "method GC / FID" given in the description.

Method for bonding parts to be joined, comprising

a) the application of a thermosetting and moisture-curable adhesive composition, the

A) an isocyanate-terminated prepolymer of at least one polyisocyanate selected from an aliphatic polyisocyanate and toluene diisocyanate, and at least one polyol and

B) a complex compound of methylenedianiline and a sodium salt hardener for moisture curing and optionally for heat curing comprises, on one or both adherend surfaces to be bonded, contacting the adherend surfaces to be adhered and curing the adhesive composition in moisture by moisture curing and optionally by heat

Heat curing.

10. The method of claim 9, wherein the curing takes place partly by heat by heat curing and partly by moisture by moisture curing.

1 1. A method according to claim 9 or 10, wherein initially a pre-curing at heat by heat curing and then a post-curing in moisture by moisture curing takes place. 12. The method according to any one of claims 9 to 1 1, wherein at

Moisture hardening and, if it is also cured by heat, even when thermosetting the methylene dianiline contained in the complex compound is consumed by incorporation into the polymer or polymer network forming from the prepolymer.

An article comprising adherends and a cured adhesive composition as an adhesive bond of the adherends obtainable by a method according to any one of claims 9 to 12. The article of claim 13, wherein the content of methylene dianiline in the cured adhesive composition is not more than 0.1% by weight, determined according to the method GC / FID given in the description, or no methylene dianiline is detected in the cured adhesive composition as determined by the method GC / MS given in the description.

15. A thermosetting and moisture curable adhesive composition comprising an isocyanate-terminated prepolymer of at least one polyisocyanate selected from an aliphatic polyisocyanate and toluene diisocyanate, and at least one polyol and

a complex compound of methylenedianiline and a sodium salt hardening agent for moisture curing and

optionally for heat curing.