ZA200104538B - Substance for bonding, coating and sealing, consisting of cyanoacrylates and aldehyde or ketone condensation products. - Google Patents

Description

= 20014534

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Substance for Bonding, Coating and Sealing, Consisting of

Cyanoacrylates and Aldehyde or Ketone Condensation Products

This invention relates to a bonding, coating and sealing composition based on a mixture of A) cyanoacrylates and B) condensation products of aldehydes and ketones.

Cyanoacrylates adhesive such as these are known. Thus, DE 43 17 886 describes a cyanoacrylate adhesive which, to reduce adhesion to the skin, contains 1 to 40% by weight of fatty derivatives in the form of certain aliphatic alcohols or certain aliphatic carboxylic acid esters. 10 to 100,000 ppm of an anionic polymerization accelerator are added to this mixture. A large number of substances are mentioned, including inter alia formaldehyde and acetaldehyde condensation products and ethers of polyalkylene oxides, for example with sorbitol as hydroxyi-containing compound. Polyoxyethylene sorbitan esters and polyoxyethylene/sorbitol addition products are specifically mentioned. In order to make the cyanoacrylate - a low-viscosity liquid - more viscous or thixotropic, a thickener, for example polymethyl methacrylate, acrylate rubber, cellulose derivative or silicate, is dissolved or dispersed. According to the Examples, the thickener is added in a quantity of 0 to 10% by weight. The disadvantage of this composition is that, even with a high concentration of thickener, the cyanoacrylate adhesive is liquid and, accordingly, cannot be used as a sealing compound, for example, or is unsuitable for bonding porous substrates and, quite generally, is difficult to apply.

Against the background of this prior art, the problem addressed by the present invention was to provide a cyanoacrylate composition with improved handling behavior which of course would exhibit at least usable, if not outstanding performance properties for bonding, coating and sealing ‘and, above all, adequate stability in storage at room temperature. In addition, production would be simple.

The solution provided by the invention is defined in the claims and consists essentially in the use of a gel former based on a condensation product of aldehydes and ketones with polyols for cyanoacrylates in order to produce compositions dimensionally stable at 20°C.

Dimensionally stable means that the composition does not change shape over a period of 10 days at 20°C solely under the effect of its own weight when the cylindrical composition is stored horizontally at 20°C in an open tube 1.5 cm in diameter and 5 cm in length; at least the stick then projects less than 10 mm and preferably less than 0.1 mm beyond the tube.

On the other hand, however, dimensional stability should also be only so great that, when a light external pressure is applied, the composition rubs off onto paper in the same way as commercially available adhesive sticks.

Suitable gel formers are certain condensation products of aldehydes or ketones with polyols.

Compounds containing at least one acetal or ketal group are used as gel formers. Such compounds can be obtained by condensation reactions and are also typically prepared, for example, by partial or complete dehydration of polyols with aldehydes or ketones in a ratio (OH: =

C =0) of 1:0.5 to 1:0.01 and preferably 1:0.5 to 1:0.1, for example in the presence of an acid as catalyst. The acetals and ketals according to the invention may also be prepared by reaction of the polyols with derivatives of the aldehydes or ketones, for example by reaction of geminal dichlorides with evolution of hydrogen chloride or acetals or ketals with elimination of alcohol. Suitable compounds have a melting point of at least 50°C, more particularly of at least 100°C and preferably of at least 150°C. Mixtures of the acetals and ketals may also be used.

Suitable polyols contain at least one 1,2-diol, 1,3-diol or 1,4-diol group. Other functional groups, for example ether, acid, ester, amide, cyano, hemiacetal and halide groups, may also be present. Examples of

® such polyols are ethane-1,2-diol, propane-1,3-diol, propane-1,2-diol, butane-2,3-diol, butane-1,4-diol, 2,2-dimethylpropane-1,3-diol, 2,2-bis- (hydroxymethy!)-propane-1,3-diol, 2-(bromomethyl)-2-(hydroxymethyl)- propane-1,3-diol, butane-1,3,4-triol, 1-phenylpropane-1,2,3-triol, hexane- 1,2-diol, neopentyl glycol, 1,4-bishydroxymethyl cyclohexane, 2- methylpropane-1,3-diol, hexane-1,2,6-triol, 2-(2-hydroxyethoxy)-butane- 1,3,4-triol, glycerol, di- and polyglycerol, diglycerol diacetate, trimethylol propane, di-(trimethylolpropane), trimethylol ethane, pentaerythritol, bicyclo[2.2.1]heptane-2,3,5,6-tetrol, 2,2,3,3-tetrahydroxybutanedioic acid, dipentaerythritol, sorbitol, formitol, xylitol, inositol, glucitol, glucose, sucrose, starch, cellulose, ascorbic acid, partly or completely hydrolyzed polyvinyl acetate, 9,10-dihydroxystearic acid methyl ester, diacetyl sorbitol and methyl glycoside.

Preferred polyols are sorbitol, xylitol and mannitol, more particularly sorbitol.

Suitable aldehydes or ketones contain at least one substituted or unsubstituted aromatic, heteroaromatic or alicyclic ring. Other functional groups, for example ether, ester, amide, cyano and halide groups, may also be present.

Examples of suitable ketones are cyclopentanone, cyclohexanone, cycloheptanone, 1-(3,3-dimethylcyciohexyl)-ethanone, 1- cyclopropylethanone, 3-methyl-5-propylcyclohex-2-en-1-one, dicyclopropyl methanone, 4-tert.butyl cyclohexanone, dicyclohexyl methanone, 4-methyl cyclohexanone, 1-(1-methylcyclopropyl)-ethanone, (4-chlorophenyl)- cyclopropyl methanone, 1-(1H-pyrrol-2-yl)-ethanone, 1-(2,4,6- trimethylphenyl)-ethanone, 1-(2-furanyl)-2-propanone, 1-(2-naphthalenyl)- ethanone, 1-(2-thienyl)-1-propanone, 1-(4-bromophenyl)-ethanone, 1-(4- methoxyphenyl)-ethanone, 1-(naphthalenyl}-ethanone, 1,1-diphenyl-2- propanone, 1,2-diphenyl ethanone, 1,3-diphenyl-2-propanone, 1-phenyl-1- butanone, 1-phenyl-1-decanone, 1-phenyl-1-dodecanone, 1-phenyl-1-

hexanone, 1-phenyl-1-octanone, 1-phenyl-1-pentanone, 1-phenyl-1- penten-3-one, 1-phenyl-1-tetradecanone, 1-phenyl-2-butanone, 1-phenyl-2- propanone, 1-pyrazinyl ethanone, 2,2,2-trifluoro-1-phenyl ethanone, 1-(2- furanyl)-ethanone, 1-(2-pyridinyl)-ethanone, 1-(2-thienyl)-ethanone, 4- chloro-1-(4-fluorophenyl)-1-butanone, 4-phenyl-2-butanone, 1-phenyl ethanone, bis-(2-hydroxyphenyl)}-methanone, bis-(4-chlorophenyl)- methanone, cyclopentyl phenyl methanone, cyclopropyl-(4-methoxy- phenyl)-methanone, cyclopropyl-(4-methylphenyl)-methanone, cyclopropyl- 2-thienyl methanone, cyclopropyl phenyl methanone, 1,5-diphenyl-1,4- pentadien-3-one, phenyl-2-pyridinyl methanone, 2-bromo-1-(4-nitrophenyl)- ethanone, 2-napthalenyl phenyl methanone, 3-chloro-1-phenyl-1- propanone, 4-(4-hydroxyphenyl)-2-butanone, 4-(4-methoxyphenyl)-3-buten- 2-one, 1-(4-pyridinyl)-ethanone, 1-(4-hydroxyphenyl)-ethanone, 1-phenyl-1- propanone, 4-phenyl-3-buten-2-one, diphenyl methanone, 1-phenyl-2- butanone, 1-phenyl-2-buten-1-one, bis-(4-methylphenyl)-methanone, 2- methyl-1-phenyl-1-propanone, 2-chloro-1-phenyl ethanone, cyclopropyl-(4- fluorophenyl)-methanone, 1-(p-methoxyphenyl)-2-propanone, cyclohexyl phenyl methanone and phenyl-(2-thienyl)}-methanone.

Examples of suitable aldehydes are benzaldehyde, 3- chlorobenzaldehyde, 4-chlorobenzaldehyde, 2,6-dichlorobenzaldehyde, 2,4-dinitrobenzaldehyde, 3,4-dichlorobenzaldehyde, 3-fluorobenzaldehyde, 4-bromobenzaldehyde, 2-methyi tetrahydrobenzaldehyde, tetrahydrobenzaldehyde, 2-methyl-5-isopropylcyclopentene-1-aldehyde, 2,2 4-trimethylcyclohexa-4,6-diene-1-aldehyde, 3(4)-methyl-1- propylcyclohexene-3-aldehyde, 1,3(4)-dimethyicyclohexene-3-aldehyde, 2- methyl-1-propylcyciohexene-3-aldehyde, 3-cyclohexene-1-aldehyde, 2,3,4,5,6-pentafluorobenzaldehyde, 2,4,6-trihydroxybenzaldehyde, 4-tolyl acetaldehyde, 2-methylbenzaldehyde, 4-hydroxybenzaldehyde, 3-methyl benzaldehyde, 2-hydroxy-1-naphthaldehyde, 4-methylbenzaldehyde, 3,5- dimethoxy-4-hydroxybenzaldehyde, cinnamaldehyde, 3-nitrobenzaldehyde,

® 2-pentyicinnamaldehyde, 4-diethylaminobenzaldehyde, 4-methoxy- benzaldehyde, 2-phenylpropionaldehyde, 2-methoxycinnamaldehyde, 4- methylbenzaldehyde, phenoxyacetaldehyde, methylpyrrole-2-aldehyde, 2,5-dimethoxytetrahydrofuran-3-aldehyde, 2,5-dipropyl-3,4-dihydropyran-2- aldehyde, 2,5-diethyl-3,4-dihydropyran-2-aldehyde, 2,5-diisopropyl-3,4- dihydropyran-2-aldehyde, 2,5-dimethyl-3,4-dihydropyran-2-aldehyde, 2,5- dibutyl-3,4-dihydroypyran-2-aldehyde, thiophene-3-aldehyde, indole-3- aldehyde, thiophene-3-aldehyde, pyridine-3-aldehyde, pyridine-4-aldehyde and N-methylpyrrole-2-aldehyde.

Preferred aldehydes are benzaldehyde, 3-chlorobenzaldehyde and 3-fluorobenzaldehyde, more particularly benzaldehyde.

Examples of acetals and ketals according to the invention are di-O- benzylidene mannitol, di-O-(2-chlorobenzylidene)-mannitol, di-O-(4- nitrobenzylidene)-mannitol, di-O-(3-fluorobenzylidene)-mannitol, O- benzylidene sorbitol, di-O-benzylidene sorbitol diacetate, di-O-(2- chlorobenzylidene)-sorbitan diacetate, tri-O-(4-chlorobenzylidene)-sorbitol,

O-benzylidene threitol, O-benzylidene tartaric acid dimethyl ester, O- cyclohexylidene glycerol, O-cyclohexylidene ascorbic acid and O- benzylidene-9,10-dihydroxystearic acid methyl ester.

Preferred acetals and ketals are di-O-benzylidene mannitol, di-O-(3- fluorobenzylidene)-mannitol and di-O-benzylidene sorbitol, more particularly di-O-benzylidene sorbitol.

The percentage content of the aldehyde or ketone condensation products is 0.1 to 10% by weight, preferably 0.4 to 6% by weight and more particularly 1 to 3% by weight, based on the cyanoacrylate composition.

The cyanoacrylate composition is essentially based on typical cyanoacrylates, i.e. on monoacrylates and/or biscyanoacrylates. Their percentage content is at least 29.5% by weight and preferably at least 50% by weight, based on the cyanoacrylate compositions as a whole. “Typical monocyanoacrylic acid esters” in the context of the invention are understood to be compounds corresponding to general formula (1):

H.C = C(CN)-CO-O-R 0) where R is an alkyl, alkenyl, cycloalkyl, aryl, alkoxyalkyl, aralkyl or haloalkyl group with up to two conjugated C-C double bonds, with a cycloaliphatic 6- ring, with an aromatic nucleus derived from benzene and preferably with Br or Cl as halogen and containing 1 to 18 and preferably 2, 3 or 4 carbon atoms, more especially a methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, pentyl, hexyl, cyclohexyl, heptyl, 2-ethylhexyl, n-octyl, n-nonyl, oxononyl, n-decyl, d-dodecyl, 2,2,2-trifluoroethyl, hexafluoroisopropyl, allyl, methallyl, crotyl, propargyl, benzyl, phenyl, cresyl, 2-chloroethyl, 3- chloropropyi, 2-chlorobutyl, tetrahydrofurfuryl, 2-methoxyethyl, butoxyethoxyethyl, 3-methoxybutyl and 2-ethoxyethyl group. The cyanoacrylates mentioned above are known to the expert on adhesives, cf.

Ullmann’s Encyclopedia of Industrial Chemistry, Vol. A1, page 240,

Verlag Chemie Weinheim (1985), US-PS 3,254,111. Preferred monomers are the allyl, methoxyethyl, ethoxyethyl, methyl, ethyl, propyl, isopropyl or butyl esters of 2-cyanoacrylic acid. “Biscyanoacrylates” are compounds corresponding to general formula (Il): [H2C = C(CN)-CO-OLR’ (an where R'is a branched or unbranched difunctional aikane group containing 2 to 18 and, more particularly, 6 to 12 carbon atoms which may also contain hetero atoms, such as halogens and oxygen, or aliphatic or aromatic rings. However, R' is preferably a pure hydrocarbon. It is important that the biscyanoacrylates be particularly pure. This requirement

@ is satisfied, for example, by the following production and purification . methods: essentially, monocyanoacrylates are transesterified with diols and the reaction mixtures are subsequently worked up by fractional crystallization.

Accordingly, a suitable process for the production of biscyanoacrylates comprises transesterifying 2-cyanoacrylic acid or an alkyl ester thereof corresponding to general formula (lll):

H,C = C(CN)-CO-0-R? (1) where R? is a branched or unbranched alkyl group containing 1 to 6 carbon atoms, with diols corresponding to general formula (IV): [HOLR' (IV) where R' is a branched or unbranched difunctional alkane group containing 2 to 18 carbon atoms, which may also contain hetero atoms, such as halogens and oxygen, or aliphatic or aromatic rings, to form biscyanoacrylates corresponding to general formula Il and then purifying the reaction mixture by fractional crystallization.

Accordingly, one starting product is a monofunctional cyanoacrylic acid corresponding to formula Ill or an alkyl ester thereof. The alkyl group should be selected so that the alcohol formed can be easily removed.

Suitable possibilities are known to the expert from the general transesterification reaction. The alcohol is preferably removed by distillation. Accordingly, R? is a branched or unbranched alcohol radical containing 1 to 6 carbon atoms, preferably 1 or 2 carbon atoms. The monofunctional cyanoacrylate is stabilized in the usual way.

The diols (formula IV) are dihydric primary or secondary alcohols,

® preferably primary alcohols. The hydroxyl groups may be in any position to one another, although they are preferably in the alpha/omega position.

The diols contain 2 to 18 carbon atoms and preferably 6 to 12 carbon atoms. They may be in a linear, branched or cyclic arrangement. The aliphatic radical may also contain an aromatic group or, besides the hydrogen and carbon atoms, hetero atoms such as, for example, chlorine or oxygen atoms, preferably in the form of polyethylene or polypropylene glycol units. Hexane diol, octane diol, decane diol and dodecane diol are specifically mentioned as diols.

The cyanoacrylate is used in excess. Accordingly, the molar ratio of monofunctional cyanoacrylate to diol is at least 2.0:1.0, preferably 2.5:1.0 and, more preferably, 2.2:1.0.

The transesterification is catalyzed by strong acids, more especially sulfonic acids and preferably aromatic sulfonic acids such as, for example, p-toluene sulfonic acid. However, naphthalene sulfonic acid, benzene sulfonic acid and acidic ion exchangers may also be used. The concentration of the transesterification catalyst should be between 1 and 20% by weight, based on the monofunctional cyanoacrylate.

The transesterification reaction is carried out in solution, as is normally the case. Suitable solvents are aromatic hydrocarbons and halogenated hydrocarbons. Preferred solvents are toluene and xylene.

The concentration of the solution is 10 to 50% and preferably 10 to 20%.

The monohydric alcohol formed and the water formed are removed in known manner and, preferably, distilled off with the solvent. The conversion of the transesterification reaction is monitored, for example, from NMR spectra. The reaction takes several hours, as is normally the case. Where toluene is used as the solvent and p-toluene sulfonic acid as the catalyst, the reaction is terminated after 10 to 15 hours when there is no further separation of alcohol.

The working up of the reaction mixture is very important. Where

® acidic ion exchangers are used as the catalyst, they may be simply filtered off. Where soluble sulfonic acids, for example p-toluene sulfonic acid, are used as the catalyst, they are removed by solvent substitution: toluene is replaced by a mixture of hexane, heptane or decane. Pure biscyanoacrylate is obtained after two fractional crystallizations. According to NMR spectra, it has a purity of more than 99%.

The biscyanoacrylate obtained is stable in storage with the usual stabilizers and in the usual concentrations, i.e. there is hardly any change in its melting point after storage for 6 months at 20°C.

However, the biscyanoacrylates obtained polymerize very quickly in the presence of bases, preferably at substantially the same rate as the corresponding monocyanoacrylates. As with the monofunctional cyano- acrylates, traces of water are sufficient. A three-dimensionally crosslinked polymer with relatively good thermal properties is formed.

According to the invention, therefore, it is used in known cyanoacrylate adhesives in a quantity of 0.5 to 50% by weight, preferably 1 to 10% by weight and more preferably 2 to 5% by weight, based on the cyanoacrylate composition as a whole.

It is known that cyanoacrylates are accessible both to anionic and to radical chain polymerization so that it is advisable to protect the ester compositions against both types of polymerization in order to prevent premature hardening of the ester, thereby avoiding difficulties in storage.

In order to prevent anionic polymerization, an anionic polymerization inhibitor may be added to the adhesives according to the invention. Any anionic polymerization inhibitors of the type hitherto used in cyanoacrylate adhesives are suitable for this purpose. For example, the anionic polymerization inhibitor may be an acidic 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 a quantity of 0.001 to 0.5%, based on the adhesive. Other suitable anionic polymerization inhibitors are dinitrogen monoxide, hydrogen fluoride, hydrochloric acid, sulfuric acid, phosphoric acid, organic sulfonic and carboxylic acids and anhydrides thereof, phosphorus pentoxide and acid chlorides. In a preferred embodiment, a radical chain polymerization inhibitor is also added to the adhesives according to the invention in a quantity of 0.01 to 0.05% by weight. This radical chain polymerization inhibitor may be any one of the known radical chain polymerization inhibitors for cyanoacrylate compositions. Phenolic compounds, for example hydroquinone, t-butyl catequinone, pyrocatechol and p- methoxyphenol, are normally used. The above-mentioned commercially available ethyl 2-cyanoacrylate preparations are already stabilized. Should it be necessary to adjust the concentration of stabilizer where these commercially available preparations are used, this would present no difficulties to the expert.

In another preferred embodiment, polymers are also added to the cyanoacrylate compositions according to the invention, for example to increase their viscosity (thickeners) or to vary the adhesive properties. The polymers may be used in a quantity of 1 to 60% by weight, more particularly 10 to 50% by weight and preferably 10 to 30% by weight, based on the formulation as a whole. Suitable polymers are, above all, polymers based on vinyl ethers, vinyl esters, esters of acrylic acid and methacrylic acid containing 1 to 22 carbon atoms in the alcohol component, styrene or styrene co- and terpolymers with ethene, butadiene. Vinyl chloride/vinyl acetate copolymers with a vinyl chloride content of 50 to 95% by weight are preferred. The polymers may be present in liquid, resin-like or even in solid form. It is particularly important that the polymers contain no impurities from the polymerization process which could inhibit curing of the cyanoacrylate. If the polymers have too high a water content, they may have to be dried. The molecular weight (Mw) of the polymers may be scattered over a wide range but should be at least 1500 and at most

® 1,000,000 because otherwise the final viscosity of the adhesive formulation would be too high. Mixtures of the above-mentioned polymers may also be used. More particularly, a combination of low molecular weight and high molecular weight products has particular advantages in regard to the final viscosity of the adhesive formulation. Examples of suitable polymers based on vinyl acetate include Mowilith types 20, 30 and 60 and Vinnapas types B1.5, B100, B17, B5, B500/20VL, B60, UW10, UW1, UW30, UwW4 and UW50. Examples of suitable acrylate-based polymers are Acronal 4F and Laromer types 8912, PE5S55F and PO33F. Examples of suitable methacrylate-based polymers include Elvacite 2042, Neocryl types B 724,

B999 731, B 735, B 811, B 813, B 817 and B722, Plexidon MW 134,

Plexigum types M 825, M 527, N 742, N 80, P 24, P28 and PQ 610. An example of a suitable vinyl ether-based polymer is Lutonal A25. Cellulose derivatives and silica gel may aiso be used for thickening. The addition of polycyanoacrylates is particularly emphasized.

In addition, the cyanoacrylate composition according to the invention may contain other auxiliaries to obtain certain effects commensurate with the application envisaged. These other auxiliaries include above all the polymerization accelerators described in DE 43 17 886, i.e. polyalkylene oxides and derivatives thereof, particularly esters and ethers. Other polymerization accelerators are CROWN ETHERS and derivatives thereof, silica-crown compounds and cyclosulfur compounds. These polymerization accelerators are known to be added in a quantity of 10 to 100,000 ppm and more particularly in a quantity of 30 to 10,000 ppm, based on the cyanoacrylate composition. Another accelerator is cyclodextrin.

The fatty derivatives described in DE 197 52 893 and in DE 43 17 886 may also be used as plasticizers. These are fats and fatty derivatives, more particularly aliphatic alcohols, aliphatic carboxylic acid esters and carboxylic acid esters of a carbocyclic compound. Further information can be found in the patents cited above. The usual plasticizers, for example phthalates, citric acid esters, chloroparaffin and trimellitic acid esters, may of course also be used.

Solvents may also be added, in particular to increase the solubility of the aldehyde or ketone condensation product or to enable this product to be incorporated more easily in the form of a solution. Suitable organic solvents are, for example, alcohols, ethers, ketones and alkyl esters of low molecular weight. Particularly suitable organic solvents are isopropanol, methoxypropanol, ethoxypropanol, ethoxyethanol, propoxyethanol, butoxy- ethanol, methyl ethyl ketone and N-methyl-2-pyrrolidone. However, the content of solvents in the cyanoacrylate composition should be low in order not to jeopardize dimensional stability and is preferably less than 20% by weight.

Other auxiliaries are activators, dyes, pigments, fragrances, preservatives, antiseptics and fillers.

The cyanoacrylate composition according to the invention is produced essentially by dissolving the cyanoacrylates and the aldehyde or ketone condensation products with a polyol by heating and then hardening the resulting solution by cooling. In general, a stabilized cyanoacrylate composition is first prepared from an acrylate and an anionic polymerization inhibitor under nitrogen as an inert gas and is then heated to 50 to 90°C. The required components are then dissolved or suspended with intensive stirring untii a homogeneous mixture is obtained. The condensation product is then added in portions at 80 to 95°C and largely dissolved at 90 to 95°C. The mixture is then cooled, preferably to ca. 80°C, and poured into the required molds. After ca. 1 hour, the composition is generally hard and, after ca. 24 hours, is dimensionally stable enough for use as an adhesive stick. Despite its dimensional stability, the cyanoacrylate composition can be rubbed under light pressure onto a substrate, for example paper.

By virtue of its dimensional stability, the cyanoacrylate composition is suitable for conversion into a geometric shape, above all into a stick.

Adhesive sticks are preferably produced in cylindrical form. The particular shape is preferably adapted to the application envisaged. However, any shapes are possible, particularly geometric shapes with at least one plane or axis of symmetry, for example spheres, squares, pyramids, cones, cylinders, sticks, tapes, flakes, films and “pillows”. The shape is preferably smaller in two dimensions than in the third. Such shapes are, for example, sticks (hotmelt sticks) or “refills” in the form of wax sticks. The base or the geometric element may be angular, especially triangular, rectangular or hexagonal, or round (for example circular or elliptical). The diameter may be from 2 to 100 mm and the length up to 150 mm. Accordingly, the shape and quantity of the cyanoacrylate compositions according to the invention are highly variable and are largely determined by what is convenient for the particular application envisaged.

Liquid cyanoacrylate compositions with highly thixotropic properties can be produced by shearing of the ready-to-use cyanoacrylate composition at high rotational speeds. The cyanoacrylate compositions according to the invention are suitable for bonding, coating and sealing, more particularly for bonding porous substrates such as, for example, leather, textiles, paper, paperboard, cardboard, wood and skin. By virtue of their stick form, the cyanoacrylate compositions according to the invention may be used with particular advantage as an adhesive for repairing shoes, for PVC pipes and for artificial finger nails. The “gluing” of wounds, particularly where relatively long-chain cyanoacrylates are used, is also possible. In conjunction with primers, for example aliphatic amines, polyolefins can also be firmly bonded. The primers can also be converted into stick form with the gel formers according to the invention. Coloring and correcting sticks can also be produced by adding covering pigments and/or dyes. Through the absence of solvents, such sticks are particularly environment-friendly. In portioned form, the cyanoacrylate compositions according to the invention may also be used as filling material for filling cracks and holes in various materials. Both substrates are preferably coated with the adhesive, for example by rubbing with an adhesive stick.

Gap-filling bonds are also possible.

Where the cyanoacrylate compositions are used for sealing, their rapid curing rate is worth mentioning.

Surprisingly, the cyanoacrylate composition according to the invention is extremely stable in storage. For example, in conventional adhesive stick tubes, it could be stored and handled for many weeks at room temperature without any reduction in its adhesive strength.

Other advantages of the cyanoacrylate composition according to the invention include simple application, safe handling (no spattering, for example into the eyes or onto the skin), application over large areas, bonding of vertical substrates.

The invention is illustrated by the following Examples.

After 6 months at 2 to 5°C, the adhesive sticks were still usable, i.e. their consistency and adhesive properties were good. After 9 months at -18°C, the adhesive sticks were again still usable, i.e. no destruction of the gel structure and no polymer formation were observed. After heating to 20°C, the closure caps were easy to remove from the tubes. In tests with paper, the setting time and adhesive strength were virtually unchanged (paper tears). The stability in storage at -18°C of more than 9 months is important above all for medical applications.

Examples 1. Production of cyanoacrylate compositions

The stabilized cyanoacrylate was introduced under nitrogen into a three-necked flask and polymethacrylate was added in portions with intensive stirring at 50°C. After 10 minutes, the solution was clear and

EE homogeneous.

To form a gel, the temperature was increased to 85°C and dibenzylidene sorbital was added in portions to avoid the formation of lumps. After 10 minutes, the gelling agent was largely dissolved. After cooling to around 80°C, undissolved particles were removed by filtration.

The solution was poured while still hot into conventional adhesive stick tubes and then cooled. After ca. 1 hour, the consistency was solid. The next day the adhesive stick was ready-to-use and remained stable for several weeks despite repeated closing and opening. 2. Tests a) To test stability in storage, a cyanoacrylate composition in an adhesive stick tube was tested weekly for its adhesiveness on paper at 23°C/50% relative air humidity. b) To determine setting time, the cyanoacrylate composition was applied to one side of a 30 cm long paper strip and, immediately afterwards, a second strip of paper was applied and pressed down.

The time elapsing before the paper tore on separation of the adhesive bond was measured. «c©) To determine the tensile shear strength of longitudinal bonds, a) two drops of the liquid adhesive were applied to a 10 x 25 mm area of the substrate or b) a comparable quantity was applied to one side by rubbing with the adhesive stick. Immediately afterwards, the second substrate was lightly pressed on. After 2 days at 23°C/50% relative air humidity, the beechwood and also the non-wood specimens were tested for tensile shear strength (rate: 10 mm/min.) in accordance with EN 205.

The results were expressed as the averages of 5 measurements.

The substrates were pretreated as follows: - beechwood, untreated

. @ = A - PMMA: degreased - ABS plastic: degreased - PVC: degreased and - Alu: sandblasted and degreased. 3. Results

The test results are set out in Table 1. They show that useful strengths were obtained in every case, exceeding the strengths of conventional cyanoacrylate adhesives in the case of beechwood.

Table 1. Composition (in parts by weight) and properties of cyanoacrylate compositions 0 EE

Compositions Li. 1. Ethyl cyanoacrylate 100 100 2. SOz + + 3. Phosphoric acid, methanesulfonic acid + + 4. Polymethacylate 5 5 5. Dibenzylidene sorbital 0 1.8

Il Properties a) Storage stability [weeks] - >10 b) Setting time [seconds] No bond 20 c) Tensile shear strength [MP3] - beechwood 7.33 TA 7.75 - PMMA 7.01 MF 6.11 MF - ABS plastic 8.10 MF 6.21 part. MF - aluminium 14.75 7.08 -PVC 14.59 MF 4.90 MF v WO 00/32709 17 PCT/EP99/09287

TA = tearing of material

MF = material failure part. MF = material failure in some test specimens

Claims (13)

1. A cyanoacrylate adhesive, coating and sealing composition based on a mixture of A) at least one cyanoacrylate and B) at least one aldehyde or ketone condensation product with a polyol.

2. A composition as claimed in claim 1, characterized by at least one substance from the following group of aldehydes or ketones: benzaldehyde, 3-chlorobenzaldehyde and 3-fluorobenzaldehyde, more particularly benzaldehyde.

3. A composition as claimed in claim 1, characterized by at least one substance from the following group of polyols: sorbitol, xylitol and mannitol, more particularly sorbitol.

4. A composition as claimed in claim 1, characterized by at least one substance from the following group of aldehyde or ketone condensation products with polyols: di-O-benzylidene mannitol, di-O-(3- fluorobenzylidene)-mannitol and di-O-benzylidene sorbitol, more particularly di-O-benzylidene sorbitol.

5. A composition as claimed in claim 1, characterized by the following composition (based on the cyanoacrylate composition as a whole): A) 99.8 to 29.5% by weight of at least one cyanoacrylate and B) 0.1 to 10% by weight of at least one aldehyde or ketone condensation product with a polyol and C) 0.001 to 0.5% by weight of stabilizers, D) 0 to 60% by weight of thickeners, solvents, plasticizers, fillers and other auxiliaries.

6. A composition as claimed in claim 1, characterized by a geometric form, more particularly a stick form.

7. A process for the production of the composition claimed in at least one of claims 1 to 6, characterized in that a solution is first prepared from components A) and B) by heating and is then cooled.

PCT/EP99/09287

8. The use of the compositions claimed in at least one of claims 1 to 6 for bonding, coating and sealing.

9. The use claimed in claim 8 for bonding porous substrates.

10. A composition as claimed in claim 1, substantially as herein described and illustrated.

11. A process as claimed in claim 7, substantially as herein described and illustrated.

12. A use as claimed in claim 8, substantially as herein described and illustrated.

13. A new composition, a new process for the production of a composition, or a new use of a composition as claimed in any one of claims 1 to 6, substantially as herein described. AMENDED SHEET