Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2002-06-18
2003-11-25
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C544S193000, C544S222000, C252S182200, C252S182210
Reexamination Certificate
active
06653432
ABSTRACT:
The invention concerns a novel catalyst for the polycondensation of diisocyanates, in particular the (cyclo)trimerisation of diisocyanates.
A large number of catalysts are used for the polycondensation of diisocyanates to produce as a majority trimeric compounds with an isocyanurate and/or biuret and/or allophanate unit.
Mention may be made of catalysts of basic type such as tertiary amines described in DE 951 168, derivatives of alkali or alkaline earth metals such as hydroxide, carbamate, alcoholate, etc, described in FR 1 190 065, quaternary ammonium hydroxides described in FR 1 204 697, FR 1 566 256, EP 3765 and EP 10589, catalysts with an ethylene-imine group described in FR 1 401 513 and FR 2 230 642, the Mannich bases in general obtained from phenol, aldehyde and secondary amine described in FR 2 290 459 and FR 2 332 274, phosphines described in FR 1 510 342, FR 2 023 423 and DE 19 347 63 and the aminosylilated derivatives such as monoaminosilanes, diaminosilanes, silylureas and silazanes described in EP 57653.
Those catalysts generally make it possible to obtain a polycondensation product having a satisfactory proportion of trimers.
U.S. Pat. No. 3,736,298 describes a process for the trimerisation of polyisocyanates using a double alcoholate of metals selected from the transition metals of groups III-A, IV-A and V-A, alkali metals and alkaline earth metals, more particularly a complex of alkali or alkaline earth metal of a polyvalent metal alcoholate.
The catalyst is added at ambient temperature (10-40° C.) to the reaction medium containing the isocyanate compounds and causes brutal autogenous exothermy which is not controllable. The temperature can thus reach and even exceed 200° C. The product obtained at the end of the reaction is a polyisocyanurate compound which is not clearly defined. Moreover, having regard to the exothermy factor and the autocatalytic character of the reaction, it is difficult to develop such a method on an industrial scale. Control of the method is an essential parameter insofar as it makes it possible to reproducibly guarantee a well-defined composition and targeted properties such as products of controlled viscosity, in particular products of very low viscosity.
GB 1 386 399 describes a method for the preparation of isocyanurate polymers by the reaction of isophorone diisocyanate and a catalytic amount of alkali metal phenolate.
Moreover H. Sugimoto and S. Inoué describe in Macromol. Rapid Commun., 17, No 1, January 1996, pages 1-7, the use of lanthanum isopropylate and other lanthanide isopropylates as an anionic initiator for the polymerisation of hexylisocyanate to obtain poly(hexyl isocyanate) of very high molecular weight. The reaction is conducted at low temperatures (−78° C.). The document also mentions that at ambient temperature the cyclic trimer is the only reaction product.
In addition it is indicated that the polymerisation of isocyanates carrying secondary and tertiary alkyl groups does not take place.
Ikeda et al (Pure Applied Chem. A 3410), pages 1907-1920 (1997) also describe the polymerisation of monoisocyanates at ambient temperature by means of alcoholates of lanthanides.
They report that, when n-hexyl isocyanate is reacted with yttrium isopropylate at ambient temperature, the result obtained is a product of high viscosity which solidifies after 10 minutes.
After one hour, when hydrochloric acid in methanol solution is added to the polymerisation mixture at ambient temperature, a white powder precipitates.
By the addition of a hydrochloric solution of that white powder in methanol, the result obtained is a fibrous polymer of a molecular weight of 59,000, which is revealed by infrared analysis to have the structure of nylon-1.
On the other hand, with lanthanum triisopropylate, n-hexylisocyanate results at ambient temperature in cyclic trimer as the sole reaction product.
It has now surprisingly been found that in the presence of alcoholates of rare earths, isocyanates having at least two isocyanate functions reproducibly result, under certain condition in terms of control of the reaction, in a (cyclo)condensation product composed principally of true trimer, namely the product of cyclotrimerisation of the isocyanate comprising a single isocyanurate ring, for a high rate of transformation of the initial isocyanate monomer.
Depending on the rare earth used, it is possible to obtain besides the isocyanurate forms, derivatives of biuret and/or imino-oxadiazinetrione type.
The invention concerns a method for the (cyclo)trimerisation of isocyanates having at least two isocyanate functions, characterised in that it comprises:
a) reacting initial isocyanate monomers having at least two isocyanate functions, optionally in the presence of other monomers reactive with the isocyanate monomers having at least two isocyanate functions, at a temperature of at least 20° C., advantageously at least 50° C., and lower than 200° C., advantageously lower than 150° C., in the presence of a compound comprising at least one ligand including an alcoholate function of rare earths,
b) stopping the reaction by inactivating the catalyst, in particular by the addition of a compound selected from a strong acid and a peroxide and mixtures thereof at a rate of transformation of the NCO functions present in the reaction medium of at least 2.5%, advantageously 5%, preferably 6%, and at most 80%, advantageously 70%; and optionally
c) distilling the reaction medium to eliminate the unreacted monomers.
Advantageously the compound comprising at least one ligand including a rare earth alcoholate function is in accordance with the invention an alcoholate of rare earths. The other ligands may comprise other functions such as for example acetylacetonates.
For a definition of elements of rare earths, reference will be made to the Table on page B.208 of the “Handbook of Chemistry and Physics”, Editor Robert C. Weast, 67th Ed.
They comprise the following elements: scandium, yttrium, lanthanum as well as lanthanides (cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, ytterbium and lutetium).
According to the invention it is possible to add a compound comprising a rare earth alcoholate function or a mixture of compounds.
The rare earth alcoholate function may consist of any function obtained by substitution of an alcohol OH group by a rare earth metal.
Mention may be made in particular of propylates, especially isopropylates, in particular isopropylate of the following rare earth elements: Y, Sm, Yb and La.
Methylates, ethylates and butylates of the foregoing elements are also satisfactorily suitable.
Moreover, very good results were obtained with compounds comprising at least one rare earth alcoholate function and a polyalkenylene oxide group, in particular polyethylene oxide or polypropylene oxide.
The preference is for the alcoholates of polyalkylene glycol in which the number of alkylene oxide units is not greater than 20, preferably not greater than 10 and preferably not greater than 5.
The alcoholate groups may also be carried by molecules carrying a plurality of alcoholate functions on the same molecule. By way of example mention may be made of the compounds having two alcohol functions such as glycols, butane-diols, branched glycols such as propylene glycol, triols such as glycerol or trimethylolpropane.
The ligands comprising a rare earth alcoholate function may be identical or different.
It is also possible to use a mixture of alcoholates from two or more rare earths or a mixture of metal alcoholates of which at least one is a rare earth alcoholate. The ligands of those alcoholate mixtures may be identical or different.
The method according to the invention may be used for the cyclotrimerisation of any type of isocyanates or mixture of isocyanates as defined hereinbefore whether they are aliphatic, cycloaliphatic or aromatic, including the prepolymers having terminal isocyanate groups, in particular those described in U.S. Pat. No. 5,115,071, the content of which is incorporated by reference into the present application. It can thus
Bernard Jean-Marie
Dallemer Frédéric
Leising Frederic
Revelant Denis
Burns Doane Swecker & Mathis L.L.P.
Gorr Rachel
Rhodia Chimie
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