US1651567A - Process of manufacturing porous bodies, diaphragms, filters, and the like of ebonite - Google Patents

Description

M. WILDERMAN 1 PROCESS OF MANUFACTURING PORQUS BODIES, DIAPHRAGMS,

FILTERS, AND THE LIKE 0F EBONITE Filed April 22. 1922 Dec. 6, 1927. 1,651,567

- i avwe/ntoz leqer Vl/na/er m 4 h.

M o M raoonssor -mnumorume rono'os Bonus, mu s, rmrnns, Ann m 1 we a I, 1

1mm wmmm, "or Lonnon, autumn.

- I41 01' 130mm.

'Applio'ation fled April 22,1022, am; Io. 550,000, and in eel-man April 1,1023.

The present invention relatestothe' ro duction of diaphrag'ms -or filters an of other porous bodies from ebonite,,

The different .kinds of diaphragmsv or filters, prepared with the different processes and used up to the present, either do not withstand the action of alkali (e. g, diaphragms of nitrocloth, cement, ceramic diaphragms, which contain free silica) or do not withstand the action of acids or chlorlne (eg the diaphragms of nitrocloth, cement,

' age; they can be freed after use from all do .not also always. have asbestos, etc.)..

These diaphragms the desired physical properties. Some of them become soft in water, swell in the solution and lose t eirmechanical strength (e. g.

sheets of asbe tos) {others do not swell, but

become brittle and lose .in this way their mechanical strength; others again cannot be produced of the desired shape, or cannot be produced straight enough for large surfaces eg the ceramic diaphragms, etc.); others again present great difficulties in their manufacture, etc.

. Another special feature of the different kinds ofd'iaphragms preparedwith the differenti' methods, is that their production is restricted to special porosities and percolations, and that the last can be varied only in comparatively narrow limits. This restricts the field of the useful application of the different kinds o'fdiaphragms,

These diaphragms have furtherthe disadvantage, that they cannot be produced of any size or shape one may choose, that the .cannot readily be used in combination wit 'metals and especially not with r;insulated metals, and that after temporary use they cannot berepaired in case of da-ma e.

The object of the present invention is to produce diaphragms or filters which are free from the above disadvantages.

' By the present invention diaphragms or filters are manufactured from ebonite, which is capable of withstanding the action of alkali, acids and chlorine, theebonitemixture's being prepared in accordance with my earlier, U. ,S. Patent No. 1,022,014 issued- April 2, 1908, by which the chemical.

strength of the diaphragms is secured. a The diaphragms can be made of any desired porosity and y of any, desired percolat on properties; As they are made of ebonlte, they have also the property of adhering to ing itself at the same time into hard ebonite.

iron and to other metals, as well as-of com 55 bining with metals-whicliare totally or partially insulated "either with a non-vulcanized orv with a partially vulcanized or with a fully vulcanized ebonite-mixture. ThlS makes it possible for the first time to manufacture electrolytic cells and apparatus for they most varied purposes in a technically rational manner, both from the chemical and.

from the'mechanical point of -view. These diaphragms can be repaired in case of dam-- substances which ma have blocked up their capillaries during e ectrolysis or filtration,

andbe used again, 'by treatingthe diaphragms with acids or other suitable reagent's.

The means or methods used for the manu-1 facture of these diaphragms or filters are 'of a varied kind; they are nevertheless all based upon the same principle, consisting in the'manufacture of the same from particles which have the property, on heating (during vulcanization) to a suitable temperature,

of combining easily with one'another. Particles with suchproperties can be prepared either from partially vulcanized ebonite Thetendency of the particles thus prepared to 'easil combine with one another on heating, w ile they only-slightly touch each other, and for the mass to subsequently transform during vulcanization into hard diaphragms or filters and other porous bodies of' the most varied porosities and speeds of percolationa In order that one manner of doing this may be readily understood, I show in the accompanying drawings a form of mold adiapted for my purposes; ln-th'ese' drawings,

rubber, "enables one to manufacture ebonite- I shows a sectional view of such a mold, and Fi II a plan hereof.

he numeral 2 designates the main portion of the mold which in this instance is circular. Extending out from the upper edge of the mold 2 are flanges 3 from which project bolts 4. The cover 5 has sides 6 from which extend flanges 7. These flanges 7 are apertured so that they will slide on bolts 4. If desired, the cover 5 may be strengthened by webbing 8. i v

A quantity of the prepared powder is then taken, suflicient, if compressed so that no interstices would remain, to form a layer in the mold of a thickness considerably less than the total depth of the mold 2. For example, if the mold has a bottom area of one s}. dec. and grams of fine ebonite powder 0 the specific gravity of 1.25 were used, and the mold were subjected to a pressure of 150 atmospheres, we should get after vulcanization a dense ebonite plate free from ores which would be about 4 mm. thick. bviously, if the plate 5 is so held that the diaphragm cannot be compressed down to a thickness of 4 mm., a certain degree of porosity will result and this porosity will vary with the thickness of the final plate. In order to control such porosity, I utilize spreader blocks 9 which fit over bolts 4 and by substituting various spreader blocks of different lengths, the degree of porosity can be exactly controlled. For example, if the final plate should be 5, 6, 7, 8, 10 or 12 mm. thick, instead of l mm., we would obtain porous plates or diaphragms in which the volume of the air capillaries is equal to 20, 33, 43, 50. and 66% of the total plate or dia hragm. In this way we can get porosities w ich run through the whole scale of the known porisities for all of the different kinds of diaphragms used up to the present, and it is quite evident that in the same manner still greater and still smaller porosities can be produced. After the proper spreader blocks 9 are in place, the cover is pressed into place and the nuts are then screwed down on bolts 4, after which the mold is placed in a vulcanizer and the material is cured in the usual manner, preferably at a temperature corresponding to steam at 3 atmospheres pressure, though this may have to be varied to suit changing conditions.

Hand in hand with the different porosities we get also the greatest variation in speeds of percolation, which run through the whole sca e of known speeds of ercolation, and more. The s eed of perco ation of a dia- Ehragm or fi ter by a solution depends, as

own, upon the radius of its capillaries. According to the law of Stokes and Neumann the speed of discharge of a liquid through a capillary tube is directly pro ortional to the 4th ower of its radius. he

last, i. e. the radius of the capillary tubes ite, must depends in case of diaphragms upon two factors: in the first instance, u on the ratio of the air volume of the capil ary tubes of the diaphragm to the total volume of the diaphragm, and secondly, upon the degree of subdlvision of the ebonite powder or shavings used for the preparation of the diaphragms. As we are able to get the ebonite powder or shavings of the most varied dc gree of fineness and also to vary the porosity in very great limits, we are therefore able to vary the radius of the capillary tubes of the diaphragms in very reat limits, thus getting diaphragms or filters of the most varied speed of percolation.

While it is obvious that the chemical composition of the partially vulcanized or totally vulcanized ebonite used for the "diaphragms can vary within wide limits and can be selected in accordance with the use to which the product is to be put, nevertheless,

if it is desired that the diaphragms or filters should stand alkali and acids, as it is requisite for the chemical and the electrolyt1c industries, the ebonite mixtures used for the diaphragms should be prepared and the mixtures vulcanized in accordance with my Patent No. 1,022,014 above referred to, i. e. the partially vulcanized ebonite powder or shavings or the binding medium consisting of the thin layer of unvulcanized ebonite round the articles or shavings of hard ebonmust be sufficiently long vulcanized, or over-vulcanized. The use of vulcanization-accelerators does not alter anything in the essence of vulcanization, as long as they do not have a detrimental influence on the chemical composition of the ebonite.

'The covering of the ebonite powder or shavin etc. with a thin layer of nonvulcanize ebonite is carried through in the following manner:

If, e. g., diaphragms capable of withstanding the action of acids and alkali are to be prepared, then a solution of 55% rubber in e of a certain composition and benzine with 10% graphite and 35% sulphur is prepared; the fine powder or shavings are then introduced into such a solution, then separated by filtration from the same, dried in vacuum with recovery of the solvent and pulverized. This operation is repeated if thebindin medium (the unvulcanized ebon' ite) itself is transformed during vulcanization itself into hard ebonite, so that after vulcanization the porous diaphragmno longer contains any dissimilar binding medium, the whole of the diaphragm consisting fif vulcanized ebonite. only.

e vulcanized ebonite used'for the prep aratlon of the ebonite powder or shavings need not have a long vulcanization, since itsubsequently undergoes a further vulcanization, while the nonvulcanized ebonite of the top surface of the particles is being vulcanized.

When

lpartially vulcanized ebonite powder is to e used for the manufacture of the diaph'ragms, the ebonite used for the prepv aration of-the'sowder has to be only partlally vulcanize and this partial vulcanizatlon is carried on for a longer or a shorter timeaccordin to the fineness of the powder whichit -is esirable to get from it. The

finer the powder is to be, the longer this partial vulcanization must last.

On the other hand it is possible, by ke'eping the time of the partial vulcanization ofv 1 the ebonite for the powder as short as possible and b vulcanizing "subsequently the powder in t e mold also as short a time as possible, to get porous pliable, leatherlike iaphragms-or filters, which can-also be applied fora'number of useful purposes.

Another method of preparing ebonite dia- 5 phragms or filters consists in the followlng:

. z or the vulcanized hard powder orphysical or chemical means. The mixture is compressed in the mold and. vulcanized. This method proves, however, to be not only more complicated, but also less satisfactory than the above described much simpler methods. "It is found that the mechanical strength of such dia hragms invariably suffor much, the cohesion of the ebonite particles becoming much weeker.

As it'is possible to get with. the methods described above diaphragms of any thickness, size and shape, of any desired porosity and percolation pro rties, and as the diap ma e of ebonite, have also phragms, bein the property,-t at the can be easily made to-stlck to ron and ot er metals, as well as to metals which: are partially {or totally covered either with unvulcanized or with partially vulcanized or with completely vulcanized hard) ebonite, it is evident that the-field of their'application is very great,

and the manner of their application can also s avings application of the 'aphra for salts by means of partia be of a most varied kind. Thus it is possible e. g.- to use very porous diaphragms of great percolation properties as supports for other diaphragms or filtering materials, such .as sand, barium sulphate, flocks of asbestos, etc., in which case the latter act as the filterin material taking up all the impurities, -w ile thev ebonite diaphragms enable one to use thesefilters or filtering materials in a more rational manner and for a longer time.- The ebonite diaphragms can also be made of such a shape as to securely'receive and keep the barium sulphate, flocks of as-- bestos,etc., and so as to enable one to remove thesame from an electrolytic cell in a practical manner. Similarly, the diaphragms can be so ,constructed t at their surfaces are especially suited for-the reception and keeping other finely divided substances, such as barium sulphate, Portland cement, colloids, etc. In this way it is possible e. g. to fill up the capillanes only in the uppermost layer of the diaphragm with such substances, while the rest of t e diaphragm remains as before of a great porosit and of a small electrical resistance. Int is way'diaphra' s of ver small speed of percolation can obtaine Thislmay be illustrated by the following exam e:

- 7 mm. thick diaphragm was prepared from fine. powder, made from vulcanized hard ebonite and covered with a very'thin layer of .nonvulcanized ebonite, of a porosi-- ty=43.%: it had an absolute coefficient of 1 0 percolation (for water at 13 C.) k=r0.206.

'A pasteof fine natural barium sulphate was then prepared and rubbed into the pores of the top surfaces of the diaphragm with a piece of cloth, whith operation required only 108 very little time. The absolute coefiicient of percolation became about 1000 times smaller, in having become equal to 0.0001907. For the reasons 'ven above the field of gms' and filters is 110 very great. Not only will the be of great. use for the numerous electro ytic systems reduction of alkali and chlorine, of meta s, of gases-such as hydrogen and oxygen, of the numerous substances used exten- 116 .sivel in the dye-industry (obtained either by e ectrolytic oxidation or by electrolytic reduction), of perchlorates etc, which all use diaphragms, but they will be also'employed with great advantage for'many other 1 urposes of the electrolytic and chemical industries, such as for purification of solutions used for electrolysis, for separation of solids from liquids, for preparatlon of pure so ution, for preparation of table salt" from rock salt etc. There is also another great field of application ofthe porous diaphragms or bodies, namely in electric batteries.

Having now particularly and ascertained the nature (if my said invention and in what manner the same is to be performed I declare that what I claim is:--

1. The rocess of manufacturing porous ebonite bodies which comprises bringing partially cured ebonite particles, like wder, shavings and the like into such a v0 ume as will cause the adjacent particles to sufficiently contact and combine under the actlon of heat to form a bod of connected Ezracles, but will prevent t em thereafter III compacted into a. non-porous solid mass, an then vulcanizing them into an integral body of ebonite.

2. The process of manufacturing porous ebonite bodies which comprises bringing ebonite particles, like powder, shavings and the like, at least the surface portions of such particles being only artially cured, into such a volume as wil cause the adjacent particles to sufiiciently contact and combine under the action of heat to form a bod of connected particles, but will prevent t em from being com acted into a non-porous mass, and therea ter vulcanizing them mto an integral body.

3. A process of making porous ebonlte bodies which {comprises pressing particles, like powder, shavings and the like, of partially cured ebonite, into a mold having a greater, volume than the aggregate volume of such particles, and vulcanizing the same untila rous body of leatherllke consist ency is obtained.

4. A orous body comprising a distended mass 0 ebonite particles integrally united by vulcanization and finely divided material impregnating interstices between such united partic es.

5. A filter body com rislng a porous body comprising a distend mass of ebonite particles inte rally united by vulcanization and other sub ivided filtering material supported thereby.

6. A process of maklng a porous ebonite body which comprises pressing particles like powder, shavings, and the like of partially cured ebonite into a mass of contacting particles having a greater volume than the sum 8. The of manufacturing porous.

ebonite b0 es which comprises bringing ebonite particles, whose surface portions at least are only partially cured into such volume that they are in contact, but have interstitial spaces, and vulcanizing the mass.

9. A porous ebonite body comprising ini tially partially cured ebonite particles brought into such volume that the adjacent partlcles are in contact but are not com pacted into a non-porous solid mass, the particles being permanently united by vulcani zation.

10. A porous ebonite body comprising ebonite particles whose surface portions are initially only partially cured, the particles occupying such volume that adjacent particles are in contact, but are not compacted into a non-porous solid mass, the particles being permanently united by vulcanization.

MEYER WILDERMAN, PH. 1)., B. So.

Images