Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1997-03-05
2000-08-01
Zitomer, Fred
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
526297, 526312, 558303, 558462, 560155, C07C25330
Patent
active
060968486
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a process for the production of biscyanoacrylates and to their use in cyanoacrylate adhesives.
BACKGROUND OF THE INVENTION
Biscyanoacrylates and their production have been known for some time. They are produced by at least the following two methods: biscyanoacetates to form a crosslinked polymer which cannot readily be thermally depolymerized. blocked with dienes. The blocked monofunctional cyanoacrylate is hydrolyzed to the free acid. The ester is then prepared from the corresponding acid chloride with a diol. Finally, after the biscyanoacrylate has been exchanged for maleic anhydride, the pure biscyanoacrylate is obtained after repeated recrystallization from benzene. Accordingly, this method of production comprises five stages and is thus uneconomical.
DETAILED DESCRIPTION OF THE INVENTION
There is therefore a need for a simple method of producing pure biscyanoacrylate.
The solution provided by the invention is defined in the claims and essentially comprises transesterifying monocyanoacrylates with diols and working up the reaction mixture by fractional crystallization. The process according to the invention for the production of biscyanoacrylates is thus characterized in that 2-cyanoacrylic acid corresponding to the following general formula: carbon atoms, the following general formula: containing 2 to 18 carbon atoms, which may also contain hetero atoms, such as halogens and oxygen, or aliphatic or aromatic rings, crystallization.
Accordingly, one starting product is the monofunctional cyanoacrylic acid corresponding to formula II or an alkyl ester thereof. The alkyl group should be selected so that the alcohol formed is easy to remove. Possibilities suitable for this purpose are known to the expert from the general transesterification reaction. The alcohol is preferably removed by distillation. R.sup.2 is therefore a branched or unbranched alcohol radical containing 1 to 6 carbon atoms and preferably 1 or 2 carbon atoms. The monofunctional cyanoacrylate is stabilized in the usual way.
The diols 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 4 to 12 carbon atoms. They may be linear, branched or cyclic. The aliphatic radical may even be an aromatic group or, in addition to the hydrogen and carbon atoms, may also contain hetero atoms, for example chlorine or oxygen atoms, preferably in the form of polyethylene or polypropylene glycol units. Suitable diols are hexanediol, octanediol, decanediol and dodecanediol.
The cyanoacrylate is used in excess. The molar ratio of monofunctional cyanoacrylate to diol is therefore 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 by sulfonic acids, preferably by aromatic sulfonic acids such as, for example, p-toluene sulfonic acid. However, naphthalene sulfonic acid and benzene sulfonic acid and acidic ion exchangers may also be used as transesterification catalysts. The concentration of the transesterification catalyst should be between 1 and 20% by weight, based on the monofunctional cyanoacrylate.
The transesterification is carried out in solution as is normally the case. Suitable solvents are aromatic hydrocarbons and halogenated hydrocarbons. The preferred solvent is toluene or xylene. The concentration of the solution is in the range from 10 to 50% and preferably in the range from 10 to 20%.
The monohydric alcohol formed and the water formed are removed in known manner, preferably being distilled off with the solvent. The conversion of the transesterification reaction is monitored, for example with the aid of NMR spectra. The reaction takes several hours as usual. Where toluene is used as the solvent and p-toluene sulfonic acid as the catalyst, the reaction is over after 10 to 15 hours, i.e. no more alcohol separates off.
The
REFERENCES:
patent: 3254111 (1966-05-01), Hawkins et al.
patent: 3654340 (1972-04-01), Banitt
patent: 3975422 (1976-08-01), Buck
Abstract of L.
Carl J. Buck, Journal of Polymer Science: Polymer Chemistry Edition, vol. 16, 2475-2507, 1978.
Gololobov, Yu. G., et al., "A Novel Approach to the Synthesis of bis(2-cyanoacrylates)", Russian Chemical Bulletin, vol. 42, No. 5, May 1993, p. 961.
Ullman's Encyclopedia of Industrial Chemistry, 5th ed., vol. A 1, Verlag Chemie, Weinheim, 1985; p. 240.ff. "6.2.1 Adhesives Setting by Polymerization", esp. col. 2.
Gololobov Yuri
Gruber Werner
Nicolaisen Christian
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Zitomer Fred
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