Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
524730, 524734, 524850, C09J 404
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to adhesives and, more particularly, to quick-setting adhesive compositions based on .alpha.-cyanoacrylates which contain .alpha.-, .beta.- and/or .gamma.-cyclodextrin derivatives at least partly soluble in the cyanoacrylates.
Adhesive compositions based on .alpha.-cyanoacrylates are capable of curing in a very short time and are eminently suitable for bonding a number of materials. Cyanoacrylate adhesives are generally cured by anionic polymerization initiated by only small traces of even weak bases, such as water or methanol. Problems arise in the use of these adhesives for bonding porous materials and for bonding substrates having surfaces showing an acidic reaction which inhibit the anionic polymerization of the .alpha.-cyanoacrylate. For example, setting times of up to 20 minutes are required in the bonding of cellulose-containing materials, quite apart from the fact that the bond strength of the joined materials is often unsatisfactory.
Now, various attempts have been made to shorten the setting times, even in the case of problematical materials.
2. Discussion of Related Art
DE-OS 28 16 836 describes .alpha.-cyanoacrylate adhesives with shortened setting times which contain at least one macrocyclic polyether compound (crown ether) selected from the group of macrocyclic polyethers and their analogs as setting accelerator. According to European patent application 142 347, crown compounds containing silicon atoms are added to the cyanoacrylates as accelerators in quantities of 0.1 to 5%. However, these adhesive compositions have certain negative properties. For example, their stability in storage is in need of improvement.
Accordingly, the problem addressed by the present invention was to find other additives which would significantly shorten the setting times of cyanoacrylates without adversely affecting their stability in storage
DESCRIPTION OF THE INVENTION
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term "about".
It has now surprisingly been found that the addition of .alpha.-, .beta.- and/or .gamma.-cyclodextrin derivatives which are at least partly soluble in .alpha.-cyanoacrylates considerably shortens the setting times of adhesive compositions based on .alpha.-cyanoacrylates without adversely affecting their stability in storage.
Accordingly, the present invention relates to adhesive compositions based on .alpha.-cyanoacrylates and setting accelerators, characterized in that the adhesive composition contains hydroxyl group derivatives of .alpha.-, .beta.- and/or .gamma.-cyclodextrins at least partly soluble in .alpha.-cyanoacrylates.
In the context of the invention, "hydroxyl group derivatives" are exclusively derivatives in which one or more of the free hydroxyl groups present in cyclodextrins have been reacted.
The present invention also relates to new cyclodextrin derivatives.
The adhesives according to the invention contain as their principal component .alpha.-cyanoacrylate monomers which are esterification products of .alpha.-cyanoacrylic acid with an alcohol ROH, where R is a linear or branched C.sub.1-2 alkyl group which may be substituted by a halogen atom or by an alkoxy group, a linear or branched C.sub.2-12 alkenyl group, a linear or branched C.sub.2-12 alkynyl group, a cycloalkyl group, an aralkyl group or an aryl group. According to the invention, preferred cyanoacrylates are those in which R is a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, pentyl group, hexyl group, allyl group, methallyl group, crotyl group, propargyl group, cyclohexyl group, benzyl group, phenyl group, cresyl group, 2-chloroethyl group, 3-chloropropyl group, 2-chlorobutyl group, trifluoroethyl group, 2-methoxyethyl group, 3-methoxybutyl group and 2-ethoxyethyl group.
The .alpha.-cyanoacrylates used in accordance wit
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D. French et al., J. Am. Chem. Soc. 71, 1949, pp. 353-356.
Nicolaisen Heinz C.
Delmendo R. H.
Grandmaison Real J.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Max-Planck-Gesellschaft zur Foerderung der Wissenschaften eV
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