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United States Patent Office Patented Feb 3,305,508 United States Patent Office Patented Feb. 21, 1967 2 3,305,508 EMULSIFICATION IN PRESENCE OF AN AL standing the reduced foam formation the losses of co PHATC OXYGEN COMPOUND . agulum are high. This is because coagulation is then Gerardus E. La Hei and Jacques A. Waterman, Amster caused by the comparatively large amount of highly water dam, Netherlands, assignors to Shell Oil Company, New soluble organic oxygen compounds that is needed, even York, N.Y., a corporation of Delaware when the concentration of emulsifier is but low, for Sup No Drawing. Filed Dec. 13, 1963, Ser. No. 330,266 pressing troublesome foam formation. Moreover, these Claims priority, application Netherlands, Feb. 5, 1963, processes are not sufficiently flexible, because, on the one 288,572 hand, enlargement of the latex particles through reduc 6 Claims. (Cl. 260-29.7) tion of the emulsifier concentration does not permit of a The invention relates to a process for the preparation O proportional reduction in quantity of organic oxygen com of aqueous dispersions of homopolymeric or copolymeric pounds and hence involves greater coagulum losses, and, macromolecular substances obtained by polymerization, on the other, reduction of particle size by raising the polycondensation or polyaddition of vinylidene com emulsifier content cannot be achieved without sacrificing pounds. More in particular, the preparation of artificial the advantage of suppressing troublesome foam forma latices is contemplated. 5 tion, or without increasing the quantity of organic oxygen If necessary, increased temperature and/or pressure can compoundsagulum losses. and hence also further increasing the co be applied in preparing the solutions of the macromolec Because of this the particle size is often too small for ular substances. the preparation of good macromolecular foams and too If in preparing artificial latices, one fails to take special 20 large for preparing latices of the quality that is the most measures during and/or after emulsification, very trouble desirable for dipping processes. some foam formation occurs when the solvent is removed It has now been found that not only can the aforesaid via the vapor phase, even if the concentration of emulsifier troublesome foam and slime formation be avoided, but is quite low, and this is accompanied by partial coagula the losses through coagulation can also be obviated en tion and often by the formation of “slime.” By "slime' 25 is understood a slimy mixture, presumably consisting of tirely or almost entirely, while, in addition, within cer a continuous solvent phase in which droplets of water tain limits the particle size of the latices can be con are dispersed, which contain polymer particles that have trolled by adjusting the emulsifier concentration, without been only partially freed of solvent and are hence in a sacrificing the advantages mentioned before. strongly swollen state. Moreover, if high emulsifier con 30 Now in accordance with this invention, the process is centrations are not applied, the latices thus obtained are carried out in the presence of certain aliphatic organic very coarse, which makes them unsuitable for being con oxygen compounds, which are in this case, too, brought centrated to what are called foam latices, from which into contact with the other substances exclusively before foam rubbers can be manufactured. In addition, such vaporization of the polymer solvent and which coarse dispersions, when concentrated, do not produce 35 (a) In the conditions under which the solvent for the latices that are suitable for dipping processes. If this polymer is removed, do not have an acid reaction process is carried out with higher emulsifier concentra towards the water phase (which therefore rules out, tions and/or if pressure is reduced during the removal of for instance, esters that are hydrolyzed under such con the solvent, surface dehydration of the foam formed will ditions and also phenols), and further increase the losses due to coagulation and slime 40 (b) In the quantity applied, are completely miscible at formation. The latices of non-rubberlike polymers, such 30 C, with the quantity of solvent applied. as those of polystyrene or of styrene/butadiene copoly The distinctive features are now, however: mers with a high styrene content, can very suitably be (1) That the organic oxygen compounds applied are mixed with, say, foam rubber latices, in order to prepare poorly soluble in water, that is to say, that at 30 C. therefromproperties. foam rubbers having improved mechanical their solubility in water is less than 20 g. per 100 ml., Processes are known for the preparation of artificial and latices from diene polymers or copolymers, in which the (2) That the quantity of oxygen compounds applied, as emulsification of the solutions of such polymers can be referred to water phase, is 0.5-30% by volume. effected. For instance, they may be formed in the pres 50 As a rule the emulsification takes place under normal ence of organic oxygen compounds that are highly soluble temperature and pressure conditions, but in certain cases in water, such as readily water-soluble alcohols, ketones it may be carried out at higher or lower temperature or ethers. Under the conditions at which the solvent is and/or pressure. removed, the oxygen compounds previously used are gen The aliphatic oxygen compounds useful for this pur erally completely miscible, at the emulsification temper 55 pose include especially alcohols and ketones having 4-10 ature and pressure, with the quantities of solvent used for carbon atoms per molecule. Carbinols are preferred, as the polymer and with water. The application of the well as ketones in which at least one of the alkyl radicals aforesaid organic oxygen compounds aimed at improv attached to the DCFO group has a branched structure. ing the emulsification. The entire quantity of such com Examples of organic oxygen compounds that have a pounds was therefore admixed before emulsification. 60 solubility in water of less than 20 g. per 100 ml. at 30° C. It was found that in the processes just described, during are n-butyl alcohol, isobutyl alcohol, secondary butyl the removal of the solvent for the polymer via the vapor alcohol, the various amyl alcohols, methyl isobutyl car phase, there is no longer troublesome foaming, while no binol, the hexanols, heptanols and octanols, methyl iso "slime,” or scarcely any, is formed, provided the ratio by butyl ketone, diethyl ketone, methyl n-butyl ketone, di volume of the sum of polymer and solvent to the sum 65 isobutyl ketone. of water and organic oxygen compounds is not too high Application of the limited classes of organic oxygen and the quantity of these oxygen compounds is not too compounds according to the invention has the advantage low. Applying equal emulsifier concentrations, the aver that such compounds cause a greater reduction of surface age particle size of the resultant latices is then consider tension than do those of higher solubility in water. Con ably smaller than when the processes are carried out in 70 sequently, insofar as better emulsification is the objective, the absence of organic oxygen compounds, but notwith in the present process Smaller quantities may suffice. Be sides, such organic oxygen compounds generally have 3,305,508 3 4 higher boiling points than those of good solubility in prene, polypiperylene, copolymers of dienes with each water, owing to which they can longer continue to exert other or of dienes with monovinyl aromatic compounds, their anti-foaming effect when the solvent is being re such as the butadiene/styrene copolymers (in which moved. For this reason, too, a smaller quantity of this either the butadiene content or the styrene content may category of substances is needed than of the readily predominate), or from mixtures of such polymers and/or water-soluble organic oxygen compounds. copolymers with each other. The treatment of polymers In consequence, and also because only a very small of vinylpyridines, acrylic esters, methacrylic esters, hydro proportion of the poorly water-soluble organic oxygen genated derivatives of the foregoing polymers, and the compounds will get into the water phase, the process con like also is contemplated. cerned has the important advantage that the risk of the O The polymers that can be applied in the process ac occurrence of coagulum losses through the presence of cording to the invention also comprise the block polymers too much organic oxygen compound is Substantially less and copolymers, as well as the graft polymers and co than in the known processes. On this account, it is pos polymers. - sible to control the particle size of the latex within cer In many cases polymers or copolymers will be applied tain limits, and without any appreciable coagulation, by in the form of the solution in which they were formed modifying the concentration of the emulsifier, for instance during their preparation. between 1 and 20% w. (on polymer). According to the viscosity of the solution, the concen An additional advantage is that as a rule the difference tration of the solutions to be emulsified according to the in boiling point between the organic oxygen compounds invention may vary within wide limits, for instance from and the customary solvents for the macromolecular sub 20 3% w. to 70% w. of macromolecular substance. As a stances is large and that no azeotropes are formed between rule, however, concentrations between 5 and 20% w, will these two types of components, so that these components be the most suitable. do not pass over together. For this reason it will almost The solvents that can be used in the present process invariably be possible easily to recover the solvents free depend, among other factors, on the nature of the from, or virtually free from, organic oxygen compounds.
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