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
1996-03-04
2003-01-14
Gorr, Rachel (Department: 1711)
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...
C524S591000, C252S182200, C516S053000, C528S045000
Reexamination Certificate
active
06506832
ABSTRACT:
The present invention relates to a process for the preparation of emulsions of oils and/or gums and/or resins, which are preferably viscous. Its subject is more particularly a process for emulsifying (poly)isocyanates.
Furthermore, diisocyanates, especially alkylene diisocyanates (tolonates) and their derivatives of biuret type or their trimers are widely employed in the activity of paints and varnishes.
However, among the problems which remain unsolved to date, there is one that is particularly acute, namely the use of large quantity of organic solvent, the presence of which is considered to be toxic and detrimental to the environment.
This is why one of the aims of the present invention is to provide a process which makes it possible to obtain a stable dispersion of (poly)isocyanates in water.
Another aim of the present invention is to provide a monomer which permits (poly)isocyanate formulations in aqueous phase, with a view to responding to the progress in the techniques and regulations which tend to make the organic solvents disappear.
In order to solve this problem, there is already a description of the preparation of aqueous emulsions of oils, especially of high viscosity, by separate introduction in two different steps of two types of amphiphilic surface-active agents (which have different “HLB” values when this scale can be employed) into a conventional mixing apparatus.
However, these techniques are expensive in respect of energies and difficult to use. They demand mixing devices capable of giving high shears.
This is why one of the aims of the present invention is to provide a process which makes it possible to employ equipment which does not give high shears.
Another aim of the present invention is to provide a process which avoids high consumptions of energies.
Another aim of the present invention is to provide a process which makes it possible to obtain a narrow particle size distribution of particularly fine droplets.
We disclose a process for the preparation of aqueous emulsions of viscous phases based on preferably viscous, advantageously masked (poly)isocyanate oils and/or gums and/or resins, using a conventional mixing apparatus and not requiring the obligatory use of two types of surface-active agents.
Such a process makes it possible to prepare emulsions of advantageously masked (poly)isocyanate oils and/or gums and/or resins of completely controlled and relatively homogeneous particle size.
The process forming the subject of the invention is characterized in that a mixture consisting of the following is blended
100 parts by weight of an advantageously masked (poly)isocyanate(s) phase (A) of dynamic viscosity at 25° C. which is at least equal to 3 Pa s, preferably at least equal to 30 Pa s, or of consistency at 25° C. which does not exceed 2000, advantageously masked (poly)isocyanate(s) phase including at least one oil and/or at least one gum and/or at least one resin:
2 to 20 parts by weight, preferably from 3 to 15 parts by weight of water;
2 to 20 parts by weight, preferably from 3 to 15 parts by weight of at one least surface-active agent (B) or a combination of 0.5 to 10 parts by weight, preferably of 1 to 10 parts by weight of at least one surface-active agent (B) and of 2.5×10
−4
to 20 parts by weight, preferably of 0.001 to 15 parts by weight of at least one thickening water-soluble polymer (C) of molecular mass higher than 10,000 g/mole, preferably higher than 100,000 g/mole,
the said surface-active agent or mixture of surface-active agents exhibiting an ELB of at least 10 and the relative quantities of water and of constituent(s) (B) and optionally (C) being such that the viscosity or the consistency of the mixture of water+surface-active agent(s)+optional thickening water-soluble polymer(s) is close to or higher than one tenth of the viscosity or consistency of the advantageously masked (poly)isocyanate(s) phase (A), preferably close to or higher than the viscosity or consistency of the advantageously masked (poly)isocyanate(s) phase (A);
the said blending being carried out over a period and in shearing conditions which are sufficient to obtain an emulsion of “oil-in-water” type of particle size of the order of 0.1 to 5 micrometres, preferably of the order of 0.2 to 3 micrometres;
in that the mixture is then optionally diluted with water as a function of the desired solids content.
According to the invention a small scatter is obtained with a d
90
−d
10
which is at most equal to 4, more generally to 1.5 micrometres, preferably to 1 micrometre.
For a good implementation of the invention the dynamic viscosity measurements are preferably carried out at 25° C. with the aid of a Brookfield viscometer according to AFNOR standard NFT 76 102 of February 1972; the determination of the consistency may be performed by measuring the penetrability with the aid of a penetrometer, for example according to one of the standards AFNOR NFT 60 119, NFT 60 123, NFT 66 004, ASTM D 217, D 937, D 1321 and D 5.
As examples of advantageously masked (poly)isocyanate(s) (A) which can be used there may be mentioned-those consisting of:
polymethylene diisocyanates (generally &ohgr;,&ohgr;′), it being possible for the chain sequencing of the methylenes to be interrupted by an aromatic nucleus or by an oxygen,
the compounds originating from these derivatives to obtain a biuret, a dimer or a trimer.
it is appropriate to cite the prepolymer(s) of these products, which are formed by the reaction of isocyanate functional group(s) with a diol in proportions which define the number of the prepolycondensate units and ensures that virtually all of the end functional groups are isocyanates.
It is also possible to cite the compounds of addition of the above derivatives to polyols which have at least 3 alcohol functional groups.
The isocyanate functional groups are advantageously masked (this term is preferable to that of “blocked”, frequently employed in texts of Anglo-American sources or those culturally adapted thereto), and, thus, for two reasons, the isocyanate functional group has actually reacted so that it is no longer at all isocyanate and when they are “released” there is no certainty in any case that one passes through an isocyanate intermediate, secondly this masking is not absolute since properties similar to the isocyanate are gradually encountered again at certain temperature).
According to one of the most surprising methods of the present invention, it has been possible to demonstrate that the emulsion technique employed makes it possible to obtain stable emulsions of unmasked (poly)isocyanate(s).
The relative chemical instability of the isocyanates in the presence of phases containing water molecules not only has not prevented the formation of the emulsion whose physical stability is remarkable, but also appears to have been significantly reduced by the emulsification. It appears, to an extent which depends especially on the dilution, on the surface-active agents and on the emulsifiers, that the emulsion technique protects the (poly)isocyanates for a while from chemical decomposition.
Thus the advantageously masked (poly)isocyanate(s) may advantageously correspond to the following formula:
A(-NCOblock)
p
(Formula I)
where A denotes an organic backbone which has n free valencies, p being between 2 and 7 (closed interval) advantageously between 2 and 4 (closed interval);
where NCOblock denotes an isocyanate functional group which is advantageously masked (or protected) or otherwise.
It is appropriate to mention that the total number of carbons of the said monomer is advantageously between 10 and 100, preferably between 20 and 100, more preferably between 25 and 75.
The backbone A may be made up from a heavy polyamine (including anilines) which, for example, has a carbon number equal to at least 6 advantageously to 10, preferably to 15 [which is converted into isocyanate by the action of phosgene in a manner which is per se known].
The backbone A may also be that of the trimers and of the biurets.
Among the masking
Derian Paul-Joel
Langlois Bruno
Senechal Alain
Burns Doane Swecker & Mathis L.L.P.
Gorr Rachel
Rhone-Poulenc Chimie
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