WO2008006694A1

WO2008006694A1 - Adhesive mixtures having polyacrylnitrile

Info

Publication number: WO2008006694A1
Application number: PCT/EP2007/056338
Authority: WO
Inventors: Helmut Loth; Oliver Schmidt
Original assignee: Henkel Ag & Co. Kgaa
Priority date: 2006-07-14
Filing date: 2007-06-26
Publication date: 2008-01-17
Also published as: EP2041232A1; DE102006033075A1

Abstract

The present invention relates to a cyanacrylate adhesive, comprising at least a 2-cyanacrylate and polyacrylnitrile. The invention also relates to the use of such adhesive mixtures as adhesive having improved water resistance and/or for the gap-filling bonding of substrates.

Description

"Adhesive blends with polyacrylonitrile"

The present invention relates to a cyanoacrylate adhesive comprising at least a 2-cyanoacrylate and polyacrylonitrile. The invention also relates to the use of such adhesive mixtures as an adhesive with improved water resistance and / or gap-filling adhesive bonding of substrates.

Cyanoacrylate adhesives are reaction adhesives based on monomeric cyanoacrylic acid esters which cure anionically to give uncrosslinked polymers. In order to initiate the polymerization, the moisture present in the air or on the surfaces of the substrates to be bonded is generally sufficient. Cyanoacrylate adhesives usually contain soluble and compatible polymers and plasticizers as well as fillers for viscosity adjustment and elastification. Cyanoacrylate adhesives are suitable for bonding very different materials with and among themselves, eg. As of textiles, paper, wood, ceramics, metals, glass, plastics and skin. They are also used as a wound adhesive in surgery.

Cyanacrylic acid-based adhesives are often referred to as instant or superglue because of their generally fast cure. Nevertheless, they are in need of improvement, especially for special applications. For example, for many applications, e.g. home or outdoor, disadvantageous that adhesive compounds based on cyanoacrylates are not permanently water resistant, but quickly soften under the action of moisture or water, so that a loss of adhesive bond occurs.

It is therefore an object of the present invention to provide cyanoacrylate-based adhesive mixtures which are distinguished by improved water resistance and at the same time enable simple and uncomplicated application of such adhesive mixtures.

The invention is based on the finding that by adding polyacrylonitrile to adhesives increased water resistance of the bonds is achieved. The invention therefore provides an adhesive mixture comprising at least one 2-cyanoacrylate and polyacrylonitrile.

An adhesive mixture is understood to mean an adhesive, an adhesive preparation, an adhesive mixture or an adhesive composition. This is in particular a cyanoacrylate adhesive or cyanoacrylate adhesive or a cyanoacrylate-based adhesive or a cyanoacrylate adhesive mixture.

Polyacrylonitriles are polymers, be it homopolymers or copolymers, which are the structural feature

contain. Polyacrylonitrile is mainly processed into textile fibers and technical fibers.

The adhesive mixtures according to the invention have the advantage that adhesive bonds of increased water resistance are achieved in the bonding of two substrates, as they are advantageous for example in the home, garden, leisure, but also for industrial applications. Thus, it is for example possible to assemble dishes, glass panes for aquariums or plastic tube with the adhesives of the invention.

Another advantage is the improved or higher durability of the adhesive joints against aggressive environments. This becomes apparent, for example, when the bonded substrates are exposed both to boiling water and to dishwashing programs of a domestic dishwasher which has been rinsed at high temperature and which additionally uses strongly alkaline dishwashing detergents. An additional advantage of the adhesive mixtures according to the invention is an improved gap filling capability in comparison with cyanoacrylate adhesives without polyacrylonitrile. The gap filling capability refers to the ability of an adhesive to close cavities and unevennesses through the adhesive bond. The gap bridging designates the distance between two substrates, over which it is possible to bond gap-filling by introducing the adhesive mixture, whereby the adhesive should harden between the substrates. This distance may be in the form of a gap between two planar substrates, but also in the form of substrates having an uneven surface, in which When bonding cavities are bridged, be formed. The degree of these improved properties depends on the polyacrylonitrile content of the adhesive mixture.

Another advantageous property of the adhesive mixtures according to the invention consists in a higher voltage resistance. By this is meant that the bond has a higher elasticity than that of known cyanoacrylate adhesives. This is particularly advantageous in adhesions that are subject to a single, recurring or sustained mechanical stress, e.g. Vibrations, vibrations or those caused by temperature differences such as heating, stand or are exposed to it.

Furthermore, one can freely set the curing time over a wide range in the adhesive mixtures according to the invention. This is particularly advantageous in the bonding of glass parts, which are usually used on butyl cyanoacrylate adhesives. The addition of polyacrylonitrile here allows the use of the more available and less expensive 2-Ethylcyanacrylats.

According to a preferred embodiment, the adhesive mixtures according to the invention contain a proportion by weight of 0.1 to 40 wt .-% polyacrylonitrile based on the total weight of the adhesive mixture. Unless otherwise stated, parts by weight (% by weight) in the following text are based on the total of the respective adhesive mixture. These adhesive blends have improved water resistance for many home, garden, and industrial bonding applications.

In addition, an improved gap filling capability was observed depending on the polyacrylonitrile content. Thus, the adhesive mixtures according to the invention have a greater gap bridging than cyanoacrylate adhesives without polyacrylonitrile.

Particularly advantageous are those adhesive mixtures whose proportion of polyacrylonitrile 1 to 30 wt .-% is. These have a greatly improved water resistance, as well as a higher gap bridging than conventional cyanoacrylate-based adhesives. In addition, not only the water resistance, but also the resistance of these adhesive joints in aggressive environments is significantly improved. Therefore, there are adhesive bonds of this kind even when in contact with, for example, strongly alkaline, hot, aqueous solutions for a long time. In a further advantageous embodiment, the weight fraction of polyacrylonitrile 5 to 15 wt .-%. Such mixtures appear transparent as a dried bond and thus meet particular aesthetic requirements. Adhesive mixtures with a higher proportion of polyacrylonitrile up to about 25% by weight appear increasingly cloudy as adhesive formulations in larger layer thicknesses, but give largely transparent adhesive layers after curing.

The layer thickness of an adhesive mixture is understood to be the thickness of the applied layer. However, it may also indicate the strength of an adhesive strand when the adhesive is removed from a metering system, e.g. a tube or cartridge, is applied. The degree of transparency of a fabric often depends substantially on the layer thickness the viewer is viewing. Since the applied layer of an adhesive is usually significantly larger than the film of an adhesive bond between two substrates, differences in the perception of the user are possible here.

Another preferred embodiment contains up to 20% by weight of polyacrylonitrile. Adhesive mixtures of this specification are relatively thin and also give predominantly transparent bonds. They are therefore particularly well suited for bonding non-absorbent substrates that have even or slightly uneven surfaces. The high flowability promotes a smooth running and wetting of such surfaces by the adhesive mixture.

Another particularly preferred embodiment contains 20-30% by weight of polyacrylonitrile. Such adhesive mixtures are viscous to pasty. Therefore, they can not be absorbed by porous or absorbent substrates. Because of their viscous flow behavior, they are particularly well suited for gap-filling or gap-bridging bonding, for example of uneven, absorbent substrates.

Another preferred embodiment of the invention

Cyanoacrylate Adhesive Blends contain from 15 to 25 weight percent polyacrylonitrile. It is characterized by a particularly high durability. This embodiment is particularly advantageous when the adhesive seam is permanently or recurrently subjected to mechanical or chemical stress. The particularly high durability of the adhesive seam is a significant advantage here.

According to a further advantageous embodiment, the average molecular weight of the polyacrylonitrile is between 20 and 300 kg / mol. Particularly advantageous is polyacrylonitrile having an average molecular weight between 60 and 210 kg / mol or for example 85 kg / mol. The average molecular weight generally denotes the weight-average molecular weight <M _W > (also: M _w ) of the polymer, which is determined by means of common analysis methods, for example by means of GPC or the viscosity measurement according to Archibald. The molecular weights given in this application were determined by the method of Archibald.

While specific gravity is a material-inherent property, the bulk density, that is, the weight of the lumpy, fibrous, or powdery raw material form in relation to a given volume, is dependent on the manufacturing process. For example, polyacrylonitrile having a bulk density of about 0.1 to 0.8, preferably from 0.3 to 0.6, or also from 0.34 to 0.39 kg / l at a particle size of from 10 to 100 is suitable. / m, advantageously 40 - 50 // m or even 43 - 47 // m.

The surface correlates directly or indirectly with these parameters. Polyacrylonitrile is particularly suitable with about 0.1-0.2 m ² / g, more preferably 0.14-0.17 m ² / g. Another method for determining surfaces is the Gasabsorbtionsfähigkeit. Thus, the so-called BET surface area of a particularly suitable polyacrylonitrile is preferably less than 50 m ² / g, in particular less than 38 m ² / g or less than 30 m ² / g ,

According to a further advantageous embodiment of the adhesive mixture according to the invention polyacrylonitrile is added as a powder and / or in fiber form. The addition in powder or fiber form allows for accurate metering and even distribution during mixing. Polyacrylonitriles are in principle also in any other form, e.g. lumpy or as granules, for incorporation into cyanoacrylates suitable for an adhesive mixture according to the invention.

According to a further preferred embodiment, the polyacrylonitrile is dissolved in the adhesive mixture, colloidally dissolved or dispersed. Polyacrylonitrile has a good mixing behavior with cyanoacrylates. Depending on the molecular weight of the polyacrylonitrile and the cyanoacrylate used, the polyacrylonitrile in the adhesive mixture may be either dissolved or colloidally dissolved or dispersed. In general, the skilled person understands a homogeneous mixture of a solid and a liquid substance as dissolved. By colloidally dissolved, it is generally understood in polymers that parts of the polymer are solvated by the medium (solvent), other ranges again not be completely penetrated. Macroscopically, liquids are pooled under colloidal solutions that appear cloudy to the naked eye.

In addition, polyacrylonitrile may be dispersed in cyanoacrylates. Dispersions are understood as systems consisting of several phases, of which at least one is dispersed continuously (dispersion medium) and at least one further is dispersed (dispersed phase). In principle, dispersions can consist of immiscible, liquid phases, but also of finely divided, solid phases in a liquid phase, or a mixture of several, compatible liquid phases. The form of the solubility of the polyacrylonitrile with respect to the cyanoacrylate has no significant influence on the water resistance of the adhesive mixture according to the invention.

It is likewise possible to produce a cyanoacrylate adhesive according to the invention by adding polydisperse polyacrylonitrile or by adding a plurality of different polyacrylonitriles or their derivatives. A polydisperse polyacrylonitrile is generally understood by a person skilled in the art to mean a polyacrylonitrile which has a broad molecular weight distribution, which may also have a plurality of subdistributions. It is likewise possible to prepare a widely distributed sample by previously mixing two polyacrylonitriles of different molecular weight. In addition, the different polyacrylonitriles of different molecular weight can also be added during mixing, ie in the process of preparation of the adhesive. There is no need to previously mix the polyacrylonitriles.

Furthermore, improved water resistance of the cyanoacrylate adhesives of the invention can be achieved by using polyacrylonitrile derivatives. Polyacrylonitrile derivatives are understood by the person skilled in the art to mean chemical substances or compounds which can be prepared by reacting polyacrylonitrile in a chemical reaction, for example hydrogenation, saponification, cyclization reaction or a combination of such reactions. Adhesive mixtures according to the invention may therefore also contain polyamines, polycarboxylic acids or carbon fibers and intermediates of the reaction of the polyacrylonitrile via a cyclization reaction and a dehydrogenation to carbon fiber. Furthermore, it is possible that not only mixtures of different polyacrylonitriles are constituents of the adhesive mixtures according to the invention, but also mixtures of different polyacrylonitrile derivatives or one or more polyacrylonitriles with one or more polyacrylonitrile derivatives. In addition, the adhesive mixture according to the invention may contain a proportion of fillers, for example glass powder, glass powder, glass hollow spheres, glass fibers, finely divided silicas or graphite.

According to a further advantageous embodiment, the adhesive mixture according to the invention comprises at least one filler of amorphous, highly dispersed, i. finely divided silica. This can be added to a presented mixture of cyanoacrylate adhesive and polyacrylonitrile, but the individual components can also be mixed together in any order.

The addition of fumed silica appears to further improve the stress resistance of the bond, such that these bonds are susceptible to thermal or mechanical stress, e.g. Vibrations, vibrations or those arising from temperature differences or heating, are highly resistant. In addition, the viscosity or the pasty nature of the adhesive mixture can also be influenced in a targeted manner by the addition of highly dispersed silicon dioxide. By suitable choice of the mixing proportions of polyacrylonitrile and finely divided silica, the processing and setting properties of the adhesive mixtures can be adjusted.

According to a further advantageous embodiment, the proportion by weight of the amorphous silicon dioxide is 1 to 40% by weight, in particular 1 to 30% by weight, based on the total weight of the adhesive mixture. Depending on the proportion of fumed silica, it is possible to observe a growing dielectric strength or an increasing elasticity of the bond.

Furthermore, proportions by weight of between 10 and 15% by weight of silica are advantageous. Such cyanoacrylate adhesives have particularly good mechanical properties, in particular excellent cohesion.

According to a further advantageous embodiment of the adhesive mixture according to the invention, the BET surface area of the amorphous silica is 10 to 250 m ² / g, particularly preferably 30 to 90 m ² / g. In addition to the usually used as fillers fumed silica types having a BET surface area of 100-400 m ² / g, which are known for example under the trade name Aerosil, the use of such silica is particularly advantageous, the BET surface area of 10 to 90 m ² / g, preferably from 30 to 70 m ² / g or also, for example, 45 to 55 m ² / g. This, for example, available under the name Durasil, has a significantly lower BET surface area. While silica grades with a high BET surface area have a strong viscosity-increasing effect, this silica has a lower BET surface area Contrary to the highly dispersed silicas with a high BET surface area only a small influence on the viscosity of the adhesive mixture. Thus, significantly higher filling levels can be achieved with sufficiently low-viscosity adhesives. This low BET surface area silica makes it possible to adjust the processing time (correction time, correctability) over the added amount of silica. In the case of glass adhesives, instead of the usual butyl cyanoacrylate, for example, 2-ethyl cyanoacrylate can be used, which reacts too quickly in combination with the commonly used types of silica.

Another silica suitable for the practice of the invention, for example, is commercially available as silica soot. This is a product which is obtained in the production of quartz glass and has a surface corresponding to BET of 50 ± 10 m ² / g. This silica is highly pure (SiO ₂ content> 99%), has a pH of about 1 to 7, preferably 2 to 5 or even 3 to 4. Silica Soot is used as a filler for silicone rubber sealants use.

In a further preferred embodiment, the 2-cyanoacrylate is selected from the group consisting of methyl, ethyl, chloroethyl, n-propyl, i-propyl, chloropropyl, allyl, propargyl, 2-butenyl, phenylethyl -, n-butyl, sec-butyl, iso-butyl, tert-butyl, n-pentyl, 1-methyl-butyl, 1-ethyl-propyl, neo-pentyl, n-hexyl, 1 Methyl pentyl, n-hexyl, n-heptyl, 2-ethylhexyl, n-octyl, n-nonyl, oxononyl, n-decyl, n-undecyl, n-dodecyl, cyclohexyl , Benzyl, phenyl, tetrahydrofuran, I, methoxyethyl, ethoxyethyl, ethoxypropyl, ethoxyisopropyl, propoxyethyl, isopropoxyethyl, butoxyethyl, methoxypropyl, methoxyisopropyl, methoxybutyl, propoxymethyl, propoxypropyl -, butoxymethyl, butoxyethyl, butoxypropyl, butoxyisopropyl, butoxybutyl, iso-nonyl, iso-decyl, cyclohexylmethyl, naphthyl, 2- (2'-methoxy) ethoxyethyl, 2 (2'-ethoxy) -ethoxyethyl, 2- (2'-propoxy) -ethoxy-ethyl, 2- (2'-butoxy) -ethoxy-ethyl, 2- (2'-pentoxy) -ethoxy ethyl, 2- (2'-hexoxy) - ethoxy-ethyl, 2- (2'-methoxy) -propoxy-propyl, 2- (2'-ethoxy) -propoxy-propyl, 2- (2'-propoxy) -propoxy-propyl, 2- 2'-pentoxy) propoxypropyl, 2- (2'-hexoxy) propoxy-propyl, 2- (2'-methoxy) -butoxy-butyl, 2- (2'-ethoxy) -butoxy- butyl, 2- (2'-butoxy) -butoxy-butyl, 2- (3'-methoxy) -propoxy-ethyl, 2- (3'-methoxy) -butoxy-ethyl, 2- (3 ' -Methoxy) -propoxy-propyl, 2- (3'-methoxy) -butoxy-propyl, 2- (2'-methoxy) -ethoxy-propyl, 2- (2'-methoxy) -ethoxy-butyl 2,2,2-trifluoroethyl and hexafluoroisopropyl ester of 2-cyanoacrylic acid. In addition to the α-cyanoacrylates commonly used, it is also possible to use β and γ-cyanoacrylates. These adhesive mixtures are characterized by a slowing compared to the α-cyanoacrylate adhesives setting behavior.

In a further advantageous embodiment, an adhesive mixture according to the invention may also contain further additives, e.g. Plasticizers, thickeners, stabilizers, activators, dyes, inhibitors and accelerators, e.g. Polyethylene glycol or cyclodextrin.

Particularly suitable plasticizers are ester compounds. The alcohol component of the ester is preferably alcohols having from 1 to 5, in particular from 2 to 4, OH groups and from 2 to 5, in particular 3 or 4, directly connected carbon atoms. The number of not directly connected C atoms can be up to 1 10, in particular up to 18 carbon atoms.

Suitable monohydric alcohols are the following: methanol, ethanol, I propanol, 2-propanol, 1-butanol, 2-butanol, 2,2-dimethyl-1-propanol, 2-methyl-1-propanol, 2,2-dimethyl 1-propanol, 2-methyl-2-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 1-pentanol, 2-pentanol, 3-pentanol, cyclopentanol, cyclopentenol, glycidol, tetrahydrofurfuryl alcohol, tetrahydro-2H-pyran-4-ol, 2-methyl-3-buten-2-ol, 3-methyl-2-buten-2-ol, 3-methyl 3-buten-2-ol, 1-cyclopropyl-ethanol, 1-penten-3-ol, 3-penten-2-ol, 4-penten-1-ol, 4-penten-2-ol, 3-pentyne 1-ol, 4-pentin-1-ol, propargyl alcohol, allyl alcohol, hydroxyacetone, 2-methyl-3-butyn-2-ol.

Suitable dihydric alcohols are, for example: 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, dihydroxyacetone, thioglycerol, 2-methyl-1,3-propanediol, 2-butyne-1,4-diol, 3-butene 1, 2-diol, 2,3-butanediol, 1, 4-butanediol, 1, 3-butanediol, 1, 2-butanediol, 2-butene-1, 4-diol, 1, 2-cyclopentanediol, 3-methyl 1, 3-butanediol, 2,2-dimethyl-1,3-propanediol, 4-cyclopenten-1, 3-diol, 1, 2-cyclopentanediol, 2,2-dimethyl-1,3-propanediol, 1, 2-pentanediol, 2,4-pentanediol, 1, 5-pentanediol, 4-cyclopentene-1, 3-diol, 2-methylene-1,3-propanediol, 2,3-dihydroxy-1,4-dioxane, 2,5-dihydroxy-1,4 dithiane.

The following trihydric alcohols may be used: glycerin, erythrulose, 1, 2,4-butanetriol, erythrose, threose, trimethylolethane, trimethylolpropane and 2-hydroxymethyl-1,3-propanediol. Of the tetrahydric alcohols, for example, erythritol, threitol, pentaerythritol, arabinose, ribose, xylose, ribulose, xylulose, lyxose, ascorbic acid, glucono-γ-lactone can be used.

As examples of pentahydric alcohols may be mentioned: arabitol, adonite, XyNt. Other suitable monohydric or polyhydric alcohols are familiar to the person skilled in the art.

The polyhydric alcohols described above can also be used, for example, in etherified form. The ethers can be prepared, for example, by condensation reactions, Williamson ether synthesis or by reaction with alkylene oxides such as ethylene, propylene or butylene oxide from the abovementioned alcohols. Examples include: diethylene glycol, triethylene glycol, polyethylene glycol, diglycerol, triglycerol, tetraglycerol, pentaglycerol, polyglycerol, technical mixtures of the condensation products of glycerol, glycerol, Diplycerinpropoxylat, pentaerythritol, Dipentaeryrthrit, Ethylenglykolmonobutylether, Propylenglykolmonohexylether, Butyldiglykol, Dipropylenglykolmonomethylether.

Examples of monohydric carboxylic acids which can be used for the esterification with the abovementioned alcohols are: formic acid, acrylic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, 2-oxovaleric acid, 3-oxovaleric acid, pivalic acid, acetoacetic acid, levulinic acid, 3-methylpentanoic acid. 2-oxobutyric acid, propiolic acid, tetrahydrofuran-2-carboxylic acid, methoxyacetic acid, dimethoxyacetic acid, 2- (2-methoxyethoxy) acetic acid, pyruvic acid, 2-methoxyethanol, vinylacetic acid, allylacetic acid, 2-pentenoic acid, 3-pentenoic acid.

Examples of polybasic carboxylic acids which may be mentioned are: oxalic acid, malonic acid, fumaric acid, maleic acid, succinic acid, glutaric acid, acetylenedicarboxylic acid, oxalacetic acid, acetonedicarboxylic acid, mesoxalic acid, citraconic acid, dimethylmalonic acid, methylmalonic acid, ethylmalonic acid.

Hydroxycarboxylic acids can also be used as starting materials, for example tartronic acid, lactic acid, malic acid, tartaric acid, citramalic acid, 2-hydroxyvaleric acid, 3-hydroxyvaleric acid, 3-hydroxybutyric acid, 3-hydroxyglutaric acid, dihydroxyfumaric acid, 2,2-dimethyl-3-hydroxypropionic acid, dimethylolpropionic acid, glycolic acid , The esterification can be either complete or partial. Optionally, mixtures of these acids can be used for the esterification.

The esters prepared from these alcohols and carboxylic acids or the corresponding derivatives are preferably free of catalysts, in particular of alkali metals and amines. This can be achieved by treating the esters according to the invention with acids, ion exchangers, acetic clays, aluminum oxides, activated carbon or other auxiliaries known to the person skilled in the art. For drying and further purification can be distilled.

Examples of esters which are particularly suitable as plasticizers are: ethyl acetate, butyl acetate, glycerol triacetate, glycerol tripropionate, triglycerol pentaacetate, polyglycerol acetate, diethylene glycol diacetate, ethyl 3-hydroxyvalerate, butyl lactate, isobutyl lactate, ethyl 3-hydroxybutyrate, diethyl oxalate, diethyl malate, dimethyl malate, diisopropyl malate, diethyl tartrate, tartaric acid tartrate , Weinsäu- rediisopropylester, dimethyl glutarate, dimethyl succinate, succinic acid diethyl ester, diethyl maleate, diethyl fumarate, malonic acid diethyl ester, acrylic acid 2-hydroxyethyl, 3-oxovalerate, glycerol diacetate, glycerol tributyrate, glycerol tripropionate, Glycerindipropionat, Glycerintriisobutyrat, Glycerindiisobutyrat, glycidyl butyrate, Acetessigsäurebutylester, ethyl levulinate, 3 Hydroxyglutaric acid dimethyl ester, glycerol acetate diprop ionate, glycerol diacetate butyrate, butyl propionate, propylene glycol diacetate, propylene glycol dibutyrate, diethylene glycol dibutyrate, trimethylolethane triacetate, trimethylolpropane triacetate, trimethylolethane tributyrate, neopentyl alcohol dibutyrate, pentyl methoxyacetate, butyl dimethoxyacetate, butyl glycolate.

The esters mentioned may be added in an amount of up to 50% by weight, preferably in an amount of 1 to 30% by weight, based on the total adhesive. Further suitable plasticizers are, for example, esters such as abietic acid esters, adipic acid esters, azelaic acid esters, benzoic acid esters, butyric acid esters, acetic acid esters, esters of higher fatty acids containing from about 8 to about 44 carbon atoms, esters containing OH groups or epoxidized fatty acids, fatty acid esters and fats, glycolic esters, phosphoric esters, phthalic acid esters , linear or branched alcohols containing 1 to 12 carbon atoms, propionic acid esters, sebacic acid esters, sulfonic acid esters, thiobutyric acid esters, trimellitic acid esters, citric acid esters, and mixtures of two or more thereof. Particularly suitable are the asymmetric esters of difunctional, aliphatic or aromatic dicarboxylic acids, for example the esterification product of adipic acid monooctyl ester with 2-ethylhexanol (Edenol DOA, Cognis, Dusseldorf) or the esterification product of phthalic acid with butanol.

Also suitable as plasticizers are the pure or mixed ethers of monofunctional, linear or branched C ₄ _ ₁₆ -alcohols or mixtures of two or more different ethers of such alcohols, for example dioctyl ether (available as Cetiol OE, Cognis, Dusseldorf).

In addition, end-capped polyethylene glycols are suitable as plasticizers. For example, polyethylene or polypropylene glycol di-C ^ alkyl ethers, in particular the dimethyl or diethyl ether of diethylene glycol or dipropylene glycol, and mixtures of two or more thereof.

A further example of an adhesive according to the invention with an ester additive comprises at least one partial and / or full ester of mono- or polyhydric aliphatic carboxylic acids with 1-5 directly bonded C atoms and monohydric to pentahydric aliphatic alcohols with 1-5 directly C atoms joined together, wherein the number of directly interconnected carbon atoms in the other aliphatic groups is at most 3, when an aliphatic group contains 4 or 5 carbon atoms, wherein the ester additive is preferably free of alkali metals and amines.

In addition, polymers may be added to the cyanoacrylate adhesive compositions of this invention, e.g. to increase their viscosity or to vary the adhesive properties. These additives serve as thickeners and affect the rheology of the adhesive mixture in the desired manner. The polymers can be used in an amount of 1 to 60, in particular 10 to 50, preferably 10 to 30 wt .-% based on the total formulation. Particularly suitable are polymers based on

Vinyl ethers, vinyl esters, esters of acrylic acid and methacrylic acid having 1 to 22 carbon atoms in the alcohol component, styrene or derived therefrom copolymers and terpolymers with ethene, butadiene. Preferred are vinyl chloride / vinyl acetate copolymers having a vinyl chloride content of 50 to 95 wt .-%. The polymers may be in liquid, resinous or even solid form. Most importantly, the polymers do not contain any impurities from the polymerization process that inhibit the curing of the cyanoacrylate. If the polymers have too high a water content, it may be necessary to dry them.

The molecular weight may be scattered in a wide range, should be at least at M _w = 1, 5 kg / mol, but at most 1,000 kg / mol, otherwise the final viscosity of the adhesive formulation is too high. It is also possible to use mixtures of the abovementioned polymers. In particular, the combination of low and high molecular weight products has particular advantages in terms of the final viscosity of the adhesive formulation. As examples of suitable polymers based on vinyl acetate may be mentioned: the Mowilith types 20, 30, and 60, the Vinnapas types B1, 5, B100, B17, B5, B500 / 20VL, B60, UW 10, UW1, UW30, UW4 and UW50. Examples of suitable acrylate-based polymers include: Acronal 4F and Laromer types 8912, PE55F and PO33F. Examples of suitable polymers based on methacrylate are: Elvacite 2042, Neocryl types B 724, B999 731, B 735, B 81 1, B 813, B 817 and B722, Plexidon MW 134, Plexigum types M 825 , M 527, N 742, N 80, P 24, P 28 and PQ 610. As an example of suitable polymers based on vinyl ethers may be mentioned: Lutonal A25. For thickening also cellulose derivatives and silica gel can be used. Particularly noteworthy is the addition of polycyanoacrylates.

Further, an adhesive of the invention may contain a pyrylium salt. This makes it possible to add a dye in a high concentration to the cyanoacrylic acid esters without noticeably deteriorating the storage stability and the adhesive properties. It can be prepared stock solutions with which cyanoacrylate adhesives can be easily dyed according to the particular application.

In addition, it is possible to add 2-cyano-pentadienoic acid esters as well as an effective amount of at least one alkylene bis (2-pentadienoate) to the cyanoacrylate adhesives in addition to the above-mentioned admixtures. These adhesive mixtures have an increased heat resistance. A further advantageous embodiment of the present invention is given by radiation-curable, containing compositions. For example, compositions comprising a cyanoacrylate component, a metallocene component and a photoinitiator component can be provided.

The cyanoacrylate adhesives of the invention may further contain a first accelerator component selected from the group consisting of calixarenes and oxacalixarenes, silicon containing crown ethers, cyclocodextrins and combinations thereof, and a second accelerator component selected from the group consisting of poly (ethylene glycol) di (meth ) acrylates, ethoxylated compounds and combinations thereof. Such adhesives cure very quickly.

Another preferred adhesive composition includes a

An accelerating component consisting essentially of calixarenes, oxacalixarenes or a combination thereof and further at least one crown ether.

Furthermore, the adhesives may contain an accelerator characterized by the following chemical structure

wherein R is a radical selected from the group consisting of hydrogen, alkyl, alkoxy, alkylthioethers, haloalkyl, carboxylic acids and esters thereof, sulfinic, sulfonic and sulfuric acids and their esters, phosphinic, phosphonic and phosphoric acids and their Estern, X is an aromatic hydrocarbon radical which may be substituted with oxygen or sulfur, Z is a single or double bond, n = 1-12, m = 1-4 and p = 1-3.

As known, cyanoacrylates are accessible to both anionic and free-radical polymerization. It is therefore advisable to protect the ester masses against both types of polymerization so that premature curing of the ester does not occur, thereby avoiding storage difficulties. These inhibitors thus have the effect that the setting behavior does not change significantly over a significantly extended storage period. In other words, by the one or more inhibitors used quantitatively inhibited spontaneous or slow polymerization. Furthermore, discoloration of the adhesive during storage is prevented.

In order to prevent anionic polymerization, an anionic polymerization inhibitor may be added to the adhesives according to the invention. Suitable for this purpose are all anionic polymerization inhibitors which have hitherto been used in the field of cyanoacrylate ester adhesives. For example, the anionic polymerization inhibitor may be an acid gas, a protonic acid or an anhydride thereof. The preferred anionic polymerization inhibitor for the adhesives according to the invention is sulfur dioxide, preferably in an amount of 0.001 to 0.5% by weight, based on the adhesive. Other useful anionic polymerization inhibitors are nitrous oxide, hydrogen fluoride, hydrochloric acid, sulfuric acid, phosphoric acid, organic sulfonic and carboxylic acids and anhydrides thereof, phosphorus pentoxide and acid chlorides. The adhesives may also be added according to the invention, a radical polymerization inhibitor in an amount of 0.01 to 0.05 wt .-%. This radical polymerization inhibitor may be one of the radical polymerization inhibitors known for cyanoacrylic acid ester compositions. Usually, phenol compounds, for example, hydroquinone, 2,6-di-tert-butyl-4-methylphenol (BHT), t-butylcatequinone, catechol and p-methoxyphenol are used.

Improved toughness of the cured cyanoacrylate adhesives can be prepared by an elastomeric copolymer as toughening additive, which is a reaction product of a C ₂ - ₂ o-olefin and a (meth) acrylate ester can be achieved.

Thermostable cyanoacrylate bonds, in particular of electrical, electronic or optical components, result in particular from cyanoacrylate adhesive compositions based on esters of monocyanacrylic acid of the general formula

H ₂ C = C (CN) -CO-O- R

wherein R is an alkyl, alkenyl, cycloalkyl, aryl, alkoxyalkyl, aralkyl or haloalkyl group, the adhesive composition containing diisocyanates and bisphenols.

Another advantageous cyanoacrylate adhesive composition with reduced adhesion to skin has a content of at least one compound of the following groups A to D and an anionic polymerization accelerator: A: Aliphatic alcohol with an aliphatic group in which six or more

Carbon atoms are directly linked together; B: aliphatic carboxylic acid ester having an aliphatic group in which six or more

Carbon atoms are directly linked together; C: aliphatic carboxylic acid ester having at least two aliphatic groups in which four or more carbon atoms are directly linked together; and D: Carboxylic acid ester of a carbocyclic compound, which in a carboxylic acid radical or

Alcohol group has an aliphatic group in which five or more carbon atoms are directly connected.

An accelerated curing of the cyanoacrylate adhesives can be achieved in particular by the use of organic compounds as activators, which have the following structural element:

-N = C-S-S-C = N -

Another object of the invention relates to the use of polyacrylonitrile to improve the water resistance of adhesive mixtures.

With the adhesive mixtures of the invention, wood, wood materials, textiles, paper, cardboard, plastic, rubber, metal, glass or ceramic can be glued. These mentioned materials can be glued to themselves, but also with each other.

Another object of the invention relates to the use of such adhesive mixtures as a superglue.

According to a preferred embodiment, the adhesive blends according to the invention are used for instant adhesives with improved water resistance.

Also particularly advantageous is the additionally improved suitability of such adhesive mixtures for gap-bridging bonding.

In the following the invention will be explained in more detail by means of examples. EXAMPLES

The test pieces were subjected to the following tests:

Test 1:

The water resistance was determined by means of a machine dishwasher program (with

Whirlpool DWF 406 W, program: Intensive (T = 70 ° C, program duration: 125 min.), Cleaner:

25 g of somat powder).

The measured value was the number of rinse cycles before the bonded substrates dissolved in the subsequent rinse.

Test 2:

The water resistance in boiling water was determined. The time was recorded after a specimen breaks up by dissolution of the adhesive bond in two parts.

Test 3:

The water resistance at room temperature (25 ° C) was determined. The time was recorded after a specimen breaks up by dissolution of the adhesive bond in two parts. If the bond lasted longer than 48 hours, this was recorded as an event.

In addition, transparency was assessed by eye.

Examples 1-11: Preparation of cyanoacrylate adhesives with polyacrylonitrile

Commercially available polyacrylonitrile, available from Kelheim Fibers, D-93309 Kelheim, under the trade designation N-polyacrylonitrile, was added manually to 2-ethyl cyanoacrylate. The polyacrylonitrile has a molecular weight of about 85 kg / mol. The proportions were set as indicated in Table 1. This adhesive mixture was applied to glass substrates and bonded in each case with glass or aluminum bodies. The size of the bond area was 2.0 cm x 2.5 cm. After a curing time of one day, the test was carried out at final strength. The glass substrate was standard window glass. In the comparative examples, pure 2-ethylcyanoacrylate was glued without additives. Table 1: Glass-glass bonding

Table 2: Glass-aluminum bonding

Observation:

The addition of polyacrylonitrile shows in all cases an improvement in the water resistance according to test 2. In glass-glass bonding shows a significant improvement in glass-aluminum bonding a slight improvement in water resistance according to test 1. In glass-glass bonding shows a significant improvement in water resistance after test 3.

Example 12-21: Preparation of Ethyl Cyanoacrylate Adhesives with Polyacrylonitrile and Amorphous Silica.

2-Ethylcyanacrylat was submitted, with polyacrylonitrile and high purity, amorphous SiC> ₂ , which is available under the trade name Aerosil OX50 Degussa AG, mixed homogeneously. The tests were carried out accordingly.

Table 3: Glass-glass bonding

Observation:

The addition of polyacrylonitrile and amorphous SiO ₂ shows in glass-glass bonds again improved water resistance according to test 2. In glass-glass bonds also shows an improvement in water resistance according to test 1. With respect to test 3 glass-glass Adhesions also achieved excellent water resistance.

Claims

claims

An adhesive composition comprising at least one 2-cyanoacrylate and polyacrylonitrile.

2. Adhesive mixture according to claim 1, characterized in that it

0.1 to 40 wt .-%, in particular 1 to 30 wt .-% polyacrylonitrile based on the total weight of the adhesive mixture contains.

3. Adhesive mixture according to claim 1 or 2, characterized in that it contains between 5 and 15 wt .-% polyacrylonitrile based on the total weight of the adhesive mixture.

4. Adhesive mixture according to one of the preceding claims, characterized in that the average molecular weight of the polyacrylonitrile is between 20 and 300 kg / mol.

5. Adhesive mixture according to one of the preceding claims, characterized in that the polyacrylonitrile was added as a powder and / or as a fiber.

6. Adhesive mixture according to one of the preceding claims, characterized in that the polyacrylonitrile dissolved in the adhesive mixture, colloidally dissolved or dispersed.

7. Adhesive mixture according to one of the preceding claims, characterized in that the adhesive mixture contains at least one filler of amorphous silica.

8. Adhesive mixture according to claim 7, characterized in that the weight fraction of the amorphous silicon dioxide is 1 to 40%, in particular 1 to 30% based on the total weight of the adhesive mixture.

9. Adhesive mixture according to claim 7 or 8, characterized in that the amorphous silica has a BET surface area of 10 to 250 m ² / g.

10. Adhesive mixture according to claim 9, characterized in that the amorphous silica has a BET surface area of 30 to 70 m ² / g.

11. Adhesive mixture according to one of the preceding claims, characterized in that the 2-cyanoacrylate is selected from the group consisting of methyl, ethyl, chloroethyl, n-propyl, i-propyl, AIIyI-, -Propargyl-, n-butyl, i-butyl, n-pentyl, n-hexyl, cyclohexyl, phenyl, tetrahydrofurfuryl, heptyl, 2-ethylhexyl, n-octyl, n-nonyl, oxononyl, n-decyl, n-dodecyl, 2-ethoxyethyl, 3-methoxybutyl, 2-ethoxy-2-ethoxyethyl, butoxyethoxyethyl, 2,2,2-trifluoroethyl and hexafluoroisopropyl esters of 2-cyanoacrylic acid.

12. Use of polyacrylonitrile to improve the water resistance of adhesive blends.

13. Use of an adhesive mixture according to any one of claims 1 to 11 as a superglue.

14. Use of an adhesive mixture according to claim 13 as a superglue having improved water resistance.

15. Use of an adhesive mixture according to claim 13 or 14 as a superglue suitable for gap-bridging bonding.