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March 20, 1945. F. w. WANDERER 2,371,722 PROCESS FOR WASHING AND DRYING COAGULA OF RUBBER AND SIMILAR MATERIALS Filed Oct. 24, 1940 [a 0 6 10a 106 6 a 105 _._L7 ' ‘.2 J ' .4 i ' Ill’ 1 129' 19 . Q Ml l l l lim 7‘NE 91111201,. 5 L A 4,212,191ll” Freda-420% WMzzdézqer ‘Wily/III!” ‘ INVENTOR 7 WW I ATTORNEY v2,371,722 Patented Mar. 20, 1945 UNITED STATES PATENT oFricE raoonss roa WASHING emitomrmo 00-‘ 'AGULA or RUBBER AND snvnma MATE RIALS Frederick W. Wanderer, Penns Grove, N. J., as signor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation otDelaware Application October 24, 1940, Serial No. 362,557 3 Claims. (or. 18-48) ' This invention relates to the’ treatment of rub sure to a coagulum by means of a rotating worm ber-like materials, and' more particularly, to a in a suitable housing and forcing it through small openings. The other objects can be accom plished by passing a dispersion and a coagulating process for coagulating, washing, and drying aqueous dispersions of rubber-like materials comprising chloroprene. ' agent into a housing containing a worm and forcing the coagulum through an opening or ' Natural rubber is usually converted into the openings under pressure, and subsequently pass solid form in which it appears in commerce by coagulating the latex in the form of sheets or slabs, passing'these between rollers, sometimes in the presence of water, to assist in the removal ing the coagulum through one or more similar steps. In its preferred form, the invention is l0 accomplished by passing a dispersion of rubber of soluble material, and ?nally drying the sheets like material or natural rubber latex into a hop or slabs thus obtained. Rubber-like materials synthetically prepared in aqueous dispersion can not, in general, be obtained in a satisfactory solid per, simultaneously passing a coagulating agent into the hopper, forcing the coagulum through a truncated cone from the larger end to the smaller and by means of a rotating worm and out form by the methods used for natural rubber, since usually the properties of the rubber-like of the cone under pressure through a perforated plate, passing the coagulum through a similar operation with a washing ?uid, and then passing material are adversely affected if any substan tial quantity of the dispersing agent is allowed to remain and since the methods used by working the coagulum through one or more similar oper up natural rubber remove only a part of the wa 20 ations, without additional ?uid, to dry the said coagulum. ' ter-soluble material. In the processes now used In the drawing: Figure 1 is a vertical section through a suit from their aqueous dispersions, they must, ac able coagulating, washing, or drying apparatus; cordingly, be thoroughly washed with water, al cohol, or other solventeither by kneading them 25 Figures 2 to 5 are suitable perforated plates for such apparatus; and in apparatus in which fresh surfaces are continu Figure 6 is an elevation of an apparatus for ally exposed to the action of the solvent or by the preferred continuous process. converting them into a form such as thin sheets Referring now more particularly to the draw or small crumbs which present a large surface - ing, Figure 1 is a vertical section through a suit relative to the volume. In either case, the ma able coagulating, washing, or drying apparatus. terial must ?nally be dried and converted into a In the ?gure, housing I has a hopper .2 and a re form suitable for storage and shipment. It is volving worm 3 which is driven by a shaft 4 by obvious that such processes for converting the any suitable means (not shown). The coagulum coagulum into the ?nal dry form require elabo enters hopper 2 and issqueezed and compressed rate equipment and considerable attention fromv by worm 3 and . is extruded, under pressure, the operating force. Both these factors add con through extruding head 5 having therein ori?ce siderably to the cost of production of the syn 6. Head 5 is attached to housing I by screws 1, thetic rubber and form one of the main reasons passing through suitable openings 8 and into why none of these synthetic products is yet as cheap as natural rubber. Furthermore, it would 40 threaded openings Sin the housing I. The water which is thereby removed from the coagulum be noted that, although the present processes for leaves housing I through openings l0, a small working up coagulated natural rubber'are consid amount also escaping through ori?ce 6. ered satisfactory, they, too, are in need of further Figure 2 is a planned view of extruding head 5 improvement, It is an object of this invention to provide a 45 having extruding opening 6 and holes 8‘ for screws. ‘ simple and e?icient method of removing the Figure 3 is another type of extruding head I05 water phase from coagula of rubber-like materi for obtaining the synthetic rubber-like materials having extruding openings I06 and screw holes als, especially neoprene (polymeric chloro-2-bu I08. , tadiene-1,3). Another object is to coagulate such dispersions; wash the coagulum, dry the 50 Figure 4 is a third type of extruding head 305 having extruding openings 306 and screw holes coagulum, and convert it into a form ‘suitable for further processing, storage, or shipment. 300. It has been discovered that the ?rst of these , objects can be accomplished by applying pres - -, Figure 5 is another type of extruding head 405. having extruding openings 406 and screw ‘ Other objects will appear hereinafter. 55 holes 408. ‘ 2,371,722 In order that the invention may be more fully understood, it will be described with reference to a dispersion of neoprene, but it is to be under stood that the invention is not limited thereto as will become more apparent hereinafter. | 205 having an increased number of openings 206. The coagulum, in the form of more numerous and smaller strings l'l, then passes into hopper 302 of housing 30l where it is again subjected to the action of a revolving worm and is extruded through head 305 through still smaller openings Example I 308. The strings of coagulum 18 contain less ' Chloroprene (100 parts) containing 0.6 'part of than 5 per cent, water and is very porous in sulfur and 4 parts of rosin, is emulsi?ed by 'me structure. The remaining water- quickly evap chanical agitation in 233 parts of water, con 10 orates on air-drying and the 'coagulum is collect taining 0.5 part of ammonium persulfate, 0.8 ed in container l9. part of sodium hydroxide and 0.5 part ’of the Although the process has been described in 'Sodium salts of the dinaphthyl methane sulfonic terms of the treatment of a dispersion of poly acid prepared‘ according to U. S. Patent 1,336, merized chloroprene in apparatus of speci?c 759. The rosin is neutralized by the sodium hy form, the invention is, in fact, very much broader. droxide forming sodium abietate which, along Thus, it may be applied to the treatment of rub with the sulfonic acids mentioned above, acts as the emulsifying and dispersing agent. The dis persion is kept at 40° C. inv a suitable vessel, ber or any rubber-like material in the form of a wet coagulum. It is clear from the above dis closure that the invention has to do with unvul which can be externally cooled or heated, until 20 canized rubber and rubber-like materials. These the polymerization is substantially complete, as may be generically called vulcanizable plastic shown by the density of the dispersion which is materials. In addition to natural rubber and ~ approximately a linear function of the propor rubber-like ‘polymers of chloroprene, it may be tion of chloroprene which is polymerized. The applied to other types of so-called synthetic rub dispersion is then treated with 2.5 parts of tetra 25 bers such as the polymers of butadiene and ho ethyl thiuram disul?de dispersed in 10 parts of mologous dienes prepared with or without the the'above emulsifying solution, The entire proc use of other polymerizable substances, such as ess up to this point may conveniently be car ried out in a continuous manner as described in styrene, methyl methacrylate, and acrylic nitrile. It may also be applied to the products obtained the application of Calcott and Starkweather, 30 from the reaction of organic dichlorides, such as Serial No. 308,386, ?led December 9, 1939. ethylene dichloride, and beta, beta-dichloro-di The dispersion so prepared, which contains ethyl ether with metallic polysul?des. 'The type about 30 per cent of neoprene, is processed in an of dispersing agent used in the preparation of the apparatus illustrated in Figure 6. This ?gure dispersions of these rubber-like materials is not shows an apparatus consisting of 4 successive critical to the present invention. The coagulum units. In the ?gure, similar parts in the various used in the invention may be prepared by any of units are indicated by numerals which differ the appropriate methods known in the art such from each other by 100, and‘ any part not specifi as the addition of salts, such, for example, as cally described hereinafter by number will be aluminum sulfate, magnesium sulfate, etc., acids, understood to be the same as the corresponding alcohols, and ketones, or by freezing as described part of the first unit of the apparatus. Refer ‘in U. S. Patent No. 2,187,146. The coagulum may ring more particularly to Figure 6, the dispersion ' be introduced into the apparatus in the form of of neoprene enters housing I through hopper 2 separate pieces or in the form of a continuous from conduit ll. Simultaneously, Vs of 7 its sheet or strip such as, for example, that formed weight of a 3 per cent aqueous solution of alu 45 by the operation of the preferred form of the minum sulfate is passed into hopper 2 from con above patent. It is often advantageous tocarry duit l2. Coagulation occurs in the hopper. The out the coagulation within the hopper of the coagulum descends upon revolving worm 3 which extrusion apparatus as in the above specii?c example. forces it through housing I ‘and out of extruding 50 head 5. The size of the opening 6 in extrusion The apparatus described above may also be head 5 is of such size that the revolving worm varied, for example, as to the size, shape, and builds up pressure within the housing and'the ‘pitch of the worm, and the volume and shape of coagulum is thus subjected to a combined pres-1 the chamber between it and the plate through sure and tearing action which removes much of which a material is extruded. It is preferred, the aqueous phase and water-soluble materials. 65 however, that the chamber in which the worm This aqueous phase escapes through perforations rotates and the worm itself should be of conical l0 and also, to a small extent, through opening rather than cylindrical form with the outlet at 0 through extrusion head 5, the water escaping the narrow end. The number of holes through through opening 0 being carried off by drain l3. which material is extruded andalso their cross The extruded coagulum l4 containing about 50 section may be varied. Thus, in the first stage, per cent water passes into second hopper I02. when the material has only slight plasticity, a Simultaneously, a stream of fresh water enters large hole is used, whileseveral smaller holes are through this hopper through conduit IS.‘ The _ used as the material becomes more plastic in the coagulum is thus washed as it passes through later stage. It is always preferred, however, that hopper I02 and into housing IN. V The coagulum 65 the size and number of the openings are small is propelled through housing l0l by-a revolving enough to cause the exertion of considerable pres worm which subjects it to pressure and tearing sure by the worm upon the material being procaction and the coagulum comes out of extrusion essed. The form of the hole vneed not be cir head I05 puri?ed and containing less than 20 per cular, and, in fact, it is often desirable in the cent water. Extrusion head I05 has therein sev 70 case of more plastic materials to extrude in the eral, openings I06 and the coagulum in the form form of flat ribbons or other shapes offering a of several strings l6 passes into hopper 202 of large surface for subsequent drying. housing 20l where it is subjected to the action of Instead of a short air drying followed by col a revolving worm as before. The coagulum is lecting the coagulum. as shown in Figure 6, the extruded from this unit through extrusion head 75 coagulum. as it comes from the last unit of the ' ‘ , ' 3 2,871,722 drying apparatus in the form of porous strings having a small amount of moisture, may be passed upon a moving belt through a drying tun therefore, it is not intended to be limited except‘ as indicated in the appended claims. nel counter-current to a stream of warm air, and then collected. When so treated, less than 0.37 per cent of moisture remains in the coagulum. The conditions under which the apparatus is operated may also be varied, These variables in clude the rate of rotation of the worm, the rate > I claim: 1. The process which comprises passing-an aqueous dispersion of a__vulcaniz_able" material, comprised essentially of chloroprene polymer into a path of decreasing cross-section, simulta , neously subjecting the dispersion to coagulation conditions, forcing the mass-'along'saidpathiof ' at which the material is supplied to the ma 10 decreasing cross-section, subjecting the massive tearing action, and withdrawing the, aqueous_ chine and the temperature. Because of the work done upon the material, the temperature of the ' phase therefrom. ' 2. The process of washing and extruded material is higher than that of the ma coagulum, obtained by coagulating-an. aqueous terial introduced. This is generally‘ advanta dispersion of a vulcanizable material comprised geous where it is desired to remove part of the essentially of chloroprene polymer whichcom water content by evaporation, but, if the mate prises forcing the coagulum and fresh wash wa rial be processed is sensitive to heat, this heating may be reduced by jacketing the apparatus with ter to traverse a path'of decreasing cross-section‘ a cooling liquid or by operating at a slower speed. whereby the coagulum becomes more and- more The principle of the present invention is 20 compact while simultaneouslylsubiecting the coagulum to tearing action whereby the aqueous ‘ roughly similar to that by which natural latex coagulum is usually processed in that the coagu phase is released from the coagulum, simulta-‘' lum is dehydrated by pressure. The process, how neously drawing off the wash w'ater andv exuded aqueous phase, and then forcing the coagulum ever, di?ers by compressing the material by a worm rather than by rolls and by keeping it 25 simultaneously through .a plurality of ori?ces, compressed for a much longer time with the said orifices having a total cross-section area less result that the removal of the aqueous phase (and, than the cross-section areaof-jthe'path‘just pre ceding them. ' ' I hence, the removal of water-soluble materials) 3. The process which comprises passing an is much more e?icient and complete. Moreover, the action of the worm breaks up the cells of 30 aqueous dispersion of a vulcanizable material comprised essentially of chloroprene' polymer into the coagulum more completely, thus aiding in releasing imprisoned water. Another unexpected a path of decreasing cross-section, simultaneous ly subjecting the dispersion to coagulation condi in nature which gives it improved air drying for tions, forcing the mass along said path‘oi’ de the small amount of residual moisture and also 35 creasing cross-section, subjecting the mass to, tearing action, and withdrawing the aqueous facilitates compounding operations. Further— phase therefrom, then forcing the coagulum and more, the present invention has the further ad vantages over the prior art that the apparatus fresh wash water to traverse-a second path of decreasing cross-section whereby the coagulum required is much more compact and is much bet advantage is that the extruded product is porous ‘ ter adapted for continuous and automatic proc 40 becomes more and more compact while simulta essing of the material. The process is especially desirable with neoprene because the action of the revolving worms unexpectedly plasticizes this material to a considerable extent and reduces the amount of 45 , milling necessary in subsequent compounding op erations. » It is apparent that many widely di?erent em bodiments of this invention may be made without departing from the spirit and scope thereof, and, neously subjecting the coagulum to tearing action whereby the aqueous. phase is released from the coagulum, simultaneously drawing-oi! the wash water and exuded aqueous phase, and then forc ing the coagulum simultaneously through a plu rality of ori?ces, said ori?ces having a total cross-section area less than the cross-section area of the path just preceding them. FREDERICK W. WANDmER.