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...
Reexamination Certificate
2000-06-15
2002-12-10
Niland, Patrick D. (Department: 1714)
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...
C524S590000, C525S123000, C525S127000, C525S455000, C528S044000, C528S067000, C528S073000
Reexamination Certificate
active
06492456
ABSTRACT:
The invention relates to a process for reducing the viscosity of compositions resulting from the polymerization of isocyanate monomers or from copolymerization of isocyanate monomers with another polymerizable compound, which generally have a high viscosity at room temperature, and for allowing the separation of the high-viscosity polymerization product from the corresponding isocyanate monomer.
During the preparation of oligomeric or polymeric compounds by polymerization of starting isocyanate monomers, or copolymerization with a compound other than an isocyanate, in particular a polyol, a resulting mixture is obtained which contains the desired oligomer or (pre)polymer and, predominantly, the unreacted monomer(s), which should be separated from the products of higher molar mass.
In particular, during the catalytic cyclotrimerization of isocyanate monomers, in particular of diisocyanate monomers, the resulting mixture contains the isocyanurate, polyisocyanate where appropriate, resulting from the condensation of at least three starting monomers, as well as unconverted monomers.
Now, one of the obstructions to the industrial preparation of (poly)isocyanurate polyisocyanates, in particular those obtained by catalytic cyclotrimerization of cycloaliphatic isocyanates, has up to the present been the separation of the unconverted monomer from the condensation products of higher mass.
The reason for this is that a large number of the compositions, in particular polyisocyanates, obtained after a catalytic (cyclo)trimerization reaction comprise polymerization products which have, at the separation temperatures usually used, a high viscosity or are even solid at these temperatures.
Thus, during the preparation of IPDT (isophorone diisocyanate trimer) which is obtained by catalytic cyclotrimerization of isophorone diisocyanate (IPDI or 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane), a mixture of polyisocyanates, in particular containing isocyanurate units, is obtained, which, in the purified state (IPDI content of less than 0.5%), is a solid whose melting point is about 110-115° C. and in addition a non-newtonian fluid (viscosity at T>115° C. depends on the coefficient of shear). Separation of the IPDI from the crude trimerization mixture in the evaporators used for this purpose, in particular scraped-film evaporators, consequently requires the use of higher temperature levels than in the case of the separation of monomers of polymethylene diisocyanate type from the crude trimerization mixture obtained by polyaddition of these monomers.
In particular, in the final step of evaporation of the IPDIs, it is necessary to work at more than 200° C. in order to remove all of the IPDI and to make the IPDT conveyable.
On an industrial scale, such operating conditions require adaptations which increase the duration and cost of the process: change of exchangers, accelerating pump on the IPDT before formulation, line plotting, etc.
In addition, the transportation of purified IPDT remains difficult on account of considerable losses of load, risks of blockage, difficulty in rinsing the lines, greater cross-contamination, etc.
Moreover, there is a need in the coating industry for low-viscosity polyisocyanate compositions which combine a certain number of properties often obtained only by using isocyanates of different nature.
Thus, EP 693,512 describes a polyurethane coating composition comprising a polyisocyanate component and a polyol component, the polyisocyanate component being obtained by mixing:
(A
1
) from 50 to 95% by weight of a 1,6-diisocyanatohexane-based polyisocyanate lacquer with a viscosity at 23° C. of from 100 to 4000 mPa.s; and
(A
2
) from 5 to 50% by weight of a polyisocyanate containing isocyanurate groups, based on cycloaliphatic diisocyanates.
The polyisocyanate component can be obtained by adding, during the preparation of component A
2
, compound A
1
to the crude reaction mixture at the end of the trimerization reaction and by then removing the excess cycloaliphatic monomers by thin-film distillation.
By virtue of the invention, it has been discovered, surprisingly, that by adding to an oligomer/polymer composition of high viscosity, obtained by polymerization, in particular catalytic (cyclo)trimerization, of starting isocyanate monomers, in particular of diisocyanates, or by copolymerization of these compounds with another polymerizable compound, an amount of less than 50% by weight of the monomer-free mixture of a product with a substantially lower viscosity than that of the high-viscosity oligomer/polymer composition, the viscosity of the polymer/oligomer composition can be reduced substantially, so as to allow separation by distillation (evaporation) of the high-viscosity oligomer or polymer from the unconverted isocyanate monomer(s) and to obtain this oligomer or polymer in high purity comprising less than 1%, preferably less than 0.5%, by weight of the corresponding unconverted isocyanate monomer(s).
In addition, the final compositions containing the mixture of oligomers/polymers of high and low viscosity in the proportions indicated have particularly advantageous application properties for the production of coatings, since some of its properties are better than those obtained with a simple mixture of the two types of polyisocyanate components in the same proportions.
For the purposes of the present invention, the expression high viscosity is intended to mean a viscosity generally of greater than 10
4
mPa.s at 25° C., including compounds which are solid at 25° C.
For the purposes of the present invention, the expression low viscosity is intended to mean a viscosity generally of less than 5×10
3
mPa.s at 25° C. The viscosities are measured according to DIN standard 53019.
More generally, the ratio of the viscosities of the low-viscosity compound to the high-viscosity compound must be less than 1/1.5, preferably less than about 1/2.
The subject of the invention is thus a process for separating one (or more) oligomeric or polymeric compound(s) A obtained by polymerization or polycondensation of isocyanate monomers (A
1
) with each other or polymerization or polycondensation of isocyanate monomers (A
1
) with another copolymerizable monomer compound (A
2
), from the unconverted monomer(s), the said compound(s) A having, in the presence of an amount of monomers (A
1
and optionally A
2
) of not more than 1% by weight, preferably not more than 0.5% by weight, a viscosity (a), this process comprising the following steps:
i) the viscosity of the crude polymerization or poly-condensation mixture containing the said compound(s) A is lowered by adding thereto one or more compound(s) B of viscosity (b) such that b/a is less than 1/1.5, and preferably less than 1/2, in an amount of less than 50% by weight of the mixture A plus B; and
ii) the mixture thus obtained is co-distilled so as to separate the compound(s) (A) and (B) from the unconverted monomers.
(A) and (B) are preferably miscible at the distillation temperature.
A
2
is advantageously a polyfunctional monomer compound containing a labile hydrogen, in particular a polyol.
B
2
is advantageously a polyfunctional monomer compound containing a labile hydrogen, in particular a monofunctional or polyfunctional alcohol.
(B) can be, in particular, a molecule with a boiling point, expressed in degrees Kelvin, at atmospheric pressure, which is substantially higher, advantageously by at least 20%, preferably by at least 30%, than the highest boiling point of A
1
and A
2
.
(B) is advantageously an oligomeric or polymeric compound obtained by polymerization of isocyanate monomers (B
1
) or copolymerization of isocyanates (B
1
) with another polymerizable compound (B
2
).
(B) can also be a varnish or paint additive such as a “mar-resistance” agent, a spreading agent or a surfactant to help disperse A and B in aqueous media, or another additive used to give any property to a composition for preparing coatings.
The compounds A and B can also consist of a mixture of the compounds described above. In particular, A an
Bernard Jean-Marie
Charriere Eugénie
Revelant Denis
Burns Doane Swecker & Mathis L.L.P.
Niland Patrick D.
Rhodia Chimie
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