US2012968A - Saturating fibrous conduit and process of making same - Google Patents

Description

Sept. 3, 1935. 2,012,968

SATURATED FIBRoUs coNDUlT AND PROCESS oF MAKING .SAME

S. P. MILLER Filed May 27, 1922. 2 sheets-sheetfl INVENToR Sil/arf Par/elfe /////@f BY? A-rToRNEY S. P. MILLER Sept. 3, 1935.

SATURATED FIBROUS CONDUIT AND PROCESS OF MAKING SAME 2 Sheets-Shes?l 2 Filed May 27, 1932 W P M r. m

INVENTORV jzz/arl Paf/)feige /V/V/er ig/4 ATToRNEY Patented Sept.. 3, 1935 SATURATING FIBROUS CONDUIT AND PROCESS F MAKING SAME Stuart I. Miller, Englewood, N. ll., assgnor to The Barrett Company, New York, N. Y., a corporation of New `Hersey Application May 27, 1932, seriai'No. 613,939

12 claims. (ci. iii-7o) This invention is directed to theV saturation of absorbent articles, and particularly, the saturation and impregnation of fibrous conduits employed to conduct and protect underground cables, telephone lines, electric light, and other conductors, and for the formation of water and drain pipes to render them substantially waterproof and resistant to abrasion, corrosion, and conditions encountered underground by fibrous conduits. While, as yabove stated, the invention is particularly adapted for the saturation of fibrous conduits, it will be understood that it may` be employed to saturate small fibrous or other articles requiring impregnation, such as spools, coils, or other preformed articles, asbestos products, concrete pipes, flashing blocks, and to impregnate and saturate wood. The articles to be saturated may, of course, be prepared in any known manner. In the case of brous bases for conduits, newsprint and paper pulp, or other fibrous material, may be beaten in the usual paper beaters and the result-v ant stock screened and then pumped to paper 4cylinder machines and there formed into wet -felts or paper. The Wet paper may be wound about a cylindrical tube or mandrel to produce a wet conduit of proper thickness. This conduit may be dried in kilns to remove the major portion of its moisture content. The brous base may, of course, be prepared in any other known manner.' Such conduits are made in several sizes, commonly varying from two inches to six inches or larger in internal diameter, have an average wall thickness of approximately of an inch and are usually produced in 5, 6, and 8 foot lengths. The wall thickness of the conduits may, of course, be greater or less than 3A; of an inch and other dimensions may vary. As they come from the drying kilns, they usually contain from to 8 per cent moisture, although considerably more than 8 per cent moisture may, on occasion, be found present.

The porosity or absorptive characteristics of the walls of brous conduits may vary within wide limits from a very dense wall of a density corresponding to hard wood and exceedingly difcult to saturate with low carbon water gas tar pitch or even with other waterproofing material, such as asphalt, to a porous open wall similar in density to that of roofing feit, which will readily v absorb bituminous saturants. Samples of present commercial fibrous conduits have been tested and found to vary from substantially less than 1 cc. of voids per gram of tube wall to 2.8 or more cc. of voids per gram of tube wall. To determine the cubic centimeters of voids per gram of tube wall, a small sample of tube wall (say 2 x 5") is dried for one hour at 100 C., cooled, dessicated, 'and thereafter weighed. It is then immersed in kerosene, maintained at a temperature of 25 C., for 18 hours. Thereafter, the sample is removed from the kerosenadrained in vertical position for 30 seconds, and again weighed. The difference in weight represents the kerosene absorbed- This difference in weight in grams, divided by the specic gravity of the kerosene, corresponds to the cubic centimeters of kerosene absorbed. This volume in cubic centimeters, clivided by the original weight in grams, gives the 'voids in cubic centimeters per gram.

The fibrous conduits, as they come from the drying kiln, containing from 5 to 8 per cent of moisture, have heretofore commonly been impregnated with water gas tar pitch by immersing them in tanks of molten pitch maintained at atmospheric pressure or pressure above atmospheric and at a temperature of 275 to 300 F. or upwards. The conduits have in many cases been allowed to soak in the molten pitch for from 7 to 12 hours, then withdrawn, and permitted to drain to remove excess saturant therefrom.

This process of saturating brous conduits, it will be noted, requires the soaking of the conduits for long periods of time to obtain satisfactory penetration of the saturant throughout the Walls of the conduit. In the practice of the process, numerous dilculties are encountered, among the mostl important of which may be mentioned- 1) Foaming of the pitch during the saturation of the conduits with consequent loss of volatile oils from the pitch and restriction of the amount of pitch absorbed by the brous walls. This, I have found, may largely be attributed to the moisture content of the fibrous tubes. In the case of prior processes involving the maintenance of pitch in open tanks loss of volatile oils also occurs due to evaporation even without foaming.

(2) Building up of the free carbon content of the pitch due to the, prolonged maintenance of large bodies of pitch in which the conduits are immersed under heat, resulting in decomposition of the pitch. Increase in the free carbon content of the pitch decreases the penetrability of the saturant'and also results in carbon deposits on the walls of the conduit, preventing entrance of the saturant thereinto and resulting in defectively saturated conduits, i. e., conduits having white spots within the walls. The term free carbon is used in the sense common in thecoal tar industry to indicate material contained in the or carbon bisulde.

`as described by Weiss (Journal of Industrial and Engineering Chemistry, vol. 10, 1918, pages 736 and 820, Test D). It comprises highemolecular weight carboncompounds of low solubility, carbon, and other insoluble material;

(3) Unsatisfactory saturation of the conduits due to the fibrous walls not absorbing sufficient saturant to render them substantially waterproof. Conduits which are not adequately saturated do not attain maximum strength and resistance vto deflection or deformation;

(4) In the case of saturation of conduits under substantially atmospheric pressure,y or under higher pressures, a substantial nre hazard may exist. This is especially the case where increased pressure is produced by air'pressure on the sat-Il urant and where inadequa'tely covered and protected saturating tanks are used; and

' (5) Due to long time immersion of the organic or' fibrous bases in hot saturant, charring or burn` lng of the organic bases frequently takes place.

In order to satisfactorily protectcables and other electrical conductors, it is important that the brous conduit be substantially waterproof, resistant to abrasion and soil pressures, and capable of withstanding underground conditions and not punctured or broken by the soil and dbris surrounding it. One of the tests t0 which conduits are subjected to determine their waterproofness is to immerse them in distilled water,

. maintained at a temperature of approximately Present conduits, saturated :with water gas tar 77 F. for 48 hours, then ascertain thevpercentage increase in the weight ofthe conduit and thus arrive at the amount offwater absorbed thereby.

pitch, have been tested in this manner and many have been found to absorb in the vneighborhood of 12 m14 per eem: or water. At the present time, it isgenerally recognized that a conduit which,

upon immersion for 48 hours in distilled water maintained at a temperature of approximately 77 F., will absorb not more than 6 per cent moisture represents a satisfactorily waterproof con-I duit; a conduit absorbing not more than 4 per cent moisture under these conditions is regarded l as eminently satisfactory.. Itshould be noted .that as indicated hereinabove, many of the sat- 'urated fibrous conduits now made, when subjected to the waterproofness test briey described above, show .an absorption of moisture substan- -tially-in excess of 4 per cent, many of themV absorbing 12 per cent and more moisture. In general, the lower the water absorption, the more satisfactory is the product.

'It is an object of the present invention to pror I vide a processof saturating porous articles, and

particularly fibrous conduits, which results in substantially uniform saturation 4and impregna-- tion of conduits or other articles. In the invention disclosed and claimed in application of George Embers Serial N0. 613,937, led May' 27,

1932, involving the saturation of brous conduits by-a. vacuum process with the conduits in vertical position, while the waterproofing properties of the conduits are greatly improved as compared with prior processes of saturating the conduits, involving the soaking in saturant at atmospheric pressure or pressures above atmospheric, the portion of the conduit occupying the base portion of -the tank was .more thoroughly saturated, and

consequently, 'more resistant to absorption of Y water than the opposite end of the conduit. 'Ihe thereby reducing bituminous saturant which is insoluble in benzol i It is commonly determined process of this invention results in substantially more uniform saturation of theconduits.

Another object of this invention is to provide a process that isv simple and inexpensive to operate,

requires comparatively inexpensive apparatus for its practice, the handling of comparatively small quantities of saturant, and a comparatively short i time o'f contact between the saturant and the fibrous bases. Hence, substantially all tendencies toward charring'` or burning the organic bases are lo eliminated. The apparatus may be compact so as to occupy a small vamount of floor space.' In a well known method of saturating conduits, very large amounts of pitch were recirculated in contact with the conduit, the pitch being maintained l5 in contact with the conduits for a long period of time. As hereinafter indicated, the process of this invention may be practiced in simple, compact apparatus which requires no pumping equipment for recirculating material within the tank and in which onlyV a relatively small quantity of saturant is employed, consequently materially re.

ducing the cost involved in saturating the conduits.

In the impregnation of absorbent articleswith 2l bituminous saturant, two of the factors which tend to prevent satisfactory saturation are- 1. Air in the pores or voids, and 2. Moisture on, the fibers or other solid surfaces and as vapor or even liquid in the pores.

Air and water vapor in the pores of the material tend tol prevent entrance v'of the saturant, and

' water on the inner or outer lmaterial surfaces tends to prevent wetting of the surfaces by the saturant.

When saturation at atmospheric pressure is at- I' tempted, the major portion of the water may be removed by long soaking in the hot saturant at a vtemperature above the boiling point of water.

' The escaping steam carries with it some air. The 40 ration by applying pressure, some improvementis 50- found, but saturation is still imperfect. The effect of pressure is, by forcing additional saturant into the material, `to compress residual air and water vapor in the pores, even to vthe extent lof somewhat compressing, densifying, and deforming the walls of the saturated article. On release of pressure, the compressed air and water vapor lexpand, forcing saturant out from the material. the degree and uniformity of saturation.l y.

In accordance with a preferred embodiment of this invention, occluded gas and'moisture are removed from the conduit walls by placing them in a saturating tank and evacuating thetank 'while heating it. In the preferred procedure of drying,

I subject the conduits to be saturated to a vacuum gradually increasing to'a maximum, say 28 to 29 inches of mercury, and hold them at this vacuum while heating them long enough to-rexnov'e vsubstantially all water, water vapo and air from the voids, without allowing them to 'contact with the pitch saturant, When thus dehydrated and deaderated, I permit pitch to come into contact with them. Even while the pressure head on any given point'of the tube due to the level of pitch 75 attained-either because the 5 in the tank is low, the capillarity of the pores causes a considerable amount of pitch to be absorbed. Increase of' pressure head of the pitch forces additional amounts into the vaporand air-free voids, effecting substantially complete saturation. A

Slow increase of head of pitch has the added advantage of permitting satisfactory saturation with saturants containing ne suspended or colloidal matter like the free carbon of coal tar pitch. Slow increase in pressure (as is well known in the filtering art) tends to eliminate the building up of impenetrable layers of such suspended matter (e. g. "free carbon) on the surface of the ber conduit, and by avoiding such impenetrable layers, assures greater penetration and improved saturation.

'I'he higher the vauum attained, the more ef,- fective is the removal of air and water from the voids Aand the more complete is the absorption of saturant.

Innimpregnating withY other saturants such asaqueous of alcoholic solutions or the like, the removal of volatile liquids immiscible with the saturant from the porous or absorbent articles can be accomplished as herein described thereby facilitating the wetting of the porous article by theA saturant.

Instead of drying the conduits in the preferred manner hereinabove described, the conduits may be soaked at atmospheric pressure but preferably under vacuum in hot saturant, such as coal tar pitch or other bituminous waterproofing material,

pressure, or higher pressures.

until foaming-of the pitch stops and substantially all moisture is removed from the conduit walls. The pitch is maintained at a temperature materially above the boiling point of water ei l fective during thedrying of the conduits; for example, at a temperature of about 275 F. to 3007 F. if atmospheric pressure be employed. If this procedure of drying the conduits is followed, the present equipment for saturating them, involving the soaking of the conduits in the hot saturant, may be employed to dry the conduits. After the conduits have been dried, they may be saturated under vacuum, as hereinafter more fully pointed out. The saturant employed may be the pitch in which the conduitswere immersed to eiect the drying of fresh waterproofing saturant may be utilized.

My invention also contemplates the drying of the conduits by heating them at atmospheric Thereafter the conduits, while hot, are subjected to,` vacuum, with heating if desired, to remove moisture and occluded gas therefrom, the sensible heat of the conduits aiding in, or effecting, the evaporation under the reduced pressure to which they are subjected.

In the preferred 'method of saturation after the conduits are dried, saturant, which may be coal tar pitch, water gas tar pitch, asphalt, cutback pitches, blended pitches, or other waterproofing material, is progressively introduced into the tank while the vacuum is maintained therein. The vacuum in the tank may be utilized to cause the saturant to enter thereinto. As the saturant' progressively rises, it contacts with the walls of the material to. be saturated, illling the evacuated pores or voids thereof. 'I'he rate of flow of the saturant into the tank is controlled so that a substantially constant vacuum, preferably from 23 to 29 inches of' mercm'y, is maintained during the entire period required for the saturant to rise to completely immerse the material being saturated. Adequate vacuum generating capacity must be provided since otherwise, as the pitch rises, the vacuum would become less and less until, under the most extreme conditions, the voids at the top of the tube would become substantially full of air and hence resistant to penetration of the saturant thereinto. The, saturating tank is preferably made of such height as Ato leave a substantial space above the body of saturant introduced thereinto and in which the brous tubes are immersed. Preferably, the lfibrous tubes are permitted to soak in the saturant for from 15 minutes to two hours or longer while the vacuum is maintained therein.

Due to the maintenance of substantially constant vacuum in the container during the entire period required for the introduction of the saturant into the tank or container and the main tenance of the vacuum during the soaking period, the voids at the top end of the fibrous tubes when the tubes are being treated in vertical position "will be as Well lled with saturant as those at the bottom end and a uniformly saturated tube of impricved waterproof properties and strength will resu As the saturant for fibrous conduits, a coal tar pitch having a melting point of from 140 to 180 F. may employed. Pitch of a melting point as high as 225 F. may be used in special cases, e. g., where conduits are to be exposed to temperatures which would soften the lower 'melting point pitches. Preferred pitches having melting points of from 140 to 180 F. or higher will have a free carbon content of from 5 to 9 per cent, but pitches of higher free carbon content up to from 15 to 25 per cent, or even higher may be [used to give commercially satisfactory saturation under favorable conditions, e. g., in saturating products having comparatively open wall structure.

Preferably, coal tar pitch made by a vacuum distillation process, such for example as disclosed in Patent No. 1,759,816, granted May 20, 1930, or other processes minimizing decomposition of the tar undergoing distillation, is employed as thesaturant. Pitches made by a low temperature vacuum distillation process are characterized by low free carbon content as compared with pitches made by higher temperature processes from the same tar, and I have found that suchI pitches are particularly suitable as the saturant for fibrous conduits.` For example, such pitch of 149 F. melting point (cube in water) when tested had a free carbon content of from 5 to 9 per cent; such pitch of 158 F. melting point (cube in water) when tested had a free carbon content of from 5 to 9 per cent; such pitch of 226 F. melting point i cube in air) had a free carbon content of from 1l to 15 per cent; and such pitch of 291 F. melting point (cube in air) when testedhad a free carbon content of from 16 to 2l per cent.

Pitches produced-by distilling tar not under vacuum but by continuously heating the tar and then passing the heater tar into a vapor box where the vapors separate from the pitch have considerably higher free carbon contents for the same melting point pitch, e. Ag., p itch produced in this manner having a melting point of 149 F. (cube inwater) when tested had a free carbon content of from 11 to 1.3 percent; a pitch of 158 F. melting point (cube in water) had a "free carbon'content offrom l0 to l4per-cent; a pitch of 4 from 33 to 37 per cent. The free carbon content will depend'largely on the temperature treatment during distillation as well as on the melting point of the pitch and the free carbon 'content of the tar used to make` the pitch. Coke oven tar generally will not run much above 5 per cent free carbon; 1 per cent relatively low for such tars.

-The use of a pitch made4 by a vacuum distillation process for saturation has a two-fold advantage:

(l) In. its manufacture, this pitch is distilled under vacuum and consequently at a lower tem. perature than would be needed to produce a pitch of the same melting point by the usual methods oi distillation. This low temperature causes minimum decomposition and hence minimum free carbon formation in the pitch.` Low free carbon'? content is an aid ineilecting complete penetration and saturation of porous articles.

- (il) In its manufacture, thepitch lhas been subjectedto temperature and vacuum conditions such as to insure the substantially complete removal o1 oils which would be volatile under the conditions' maintainedin the saturating operation o! my invention. Such pitches will be substantially'tree from oils volatile under the temperature' and vacuum conditions encountered in the saturating operation, and consequentlmwill suiler minimum or at least only nominal losses from volatilization during saturation.` Owing to low volatilization losses, concentration of free carbon resulting from oil losses as well as in creases in melting point during saturation will be reduced to a Other methods of manufacture, such as steamor -inert-gas-distillation, which eii'ect distillation at relatively low temperatures, will yield desirable pitches for my process for the reasons outlinedabove.l

While my invention is particularly adapted to 'saturating absorbent articles with waterproofing materialin a molten condition, itis likewise adapted to saturating with waterproofing compounds V"dissolved to form liquid solutionsin solvents by observing the -proper temperature, pressure and time conditions. Such materials may be'` natural resins (e. g. resin) drying oils (e. g.,` linseed, tung oil, etc.), synthetic resins (e. g., paracoumarone resin, phenol#formaldehydel resin, etc.); plasticizers and modifying agents may be added. The solvents used may be chosen to meet requirements for the water-proong material used, the temperature of saturation and vacuum and other working conditionsfsuch solvents may be benzol, toluol, solventvnaphthas, petroleum naphtha, or other fractions, alcohols. chlorinated hydrocarbons,

' natural oils, etc.

Besides'waterprooiing absorbent articles this invention mayfbe employed in iireproons, oil proonns, sas lproofing, insulating, painting and, coloring such-',artlclea For example, in firearticle it may be impregnated with an aqueous solution of inorganic salts, e. g., solutions comprisingphosphates, in oil prooilng a resin or cellulose solution may be used, in gas proofing and insulating the article may be saturated with cellulose or rubber mixture and in painting and colorins thel article may be impregnatedwith paints, laoquers, enamels. or var- The invention maynalso be applied to the preservinglof wood by impregnation of the wood with creosote or aqueous solution. of fungicidal iree carbon content is Preferably, after 'theV4 tubes have been allowed \to soak for 15 minutes or more, while the body o! saturant is maintained under vacuum, the tubes are removed from the saturant and moved into the evacuated space' thereabove. This permits saturant to drain from the tubes and the removal of residual gas ormoisture in the tube walls. The fibrous tubes maybe subjected to vacuum mo.- mentarily while in this evacuated space and then again'immersed `in the saturant or they may be maintained inthe evacuated space for a predetermined period 'of time whichl may be as short as one or two minutes, and may, if desired, be for longer periods e. g., for one or more hours. In this way, removal of a maximum proportion of occluded gas and moisture and the absorption of a maximum amount of saturant by the fibrous tubes is insured; a uniform andv thoroughly saturated tube results. Instead of moving the tubes up into the evacuated space, the saturant may be passed i out of the tank while maintaining vacuum therein and the tubes thus subjected to vacuum.

As a modication of the procedure hereinabove described, after the initial soaking of the brous tubes under vacuum, the vacuum may be broken and pitch drained out of the tank. The saturated tubes are left in the tank subjected to the atmospheric pressurev then prevailing therein for a period of one or two minutes or longer. The tank is then again evacuated and then saturant passed thereinto while holding the vacuum substantially constant. The saturated tubes are permitted to soak while maintaining the vacuum ,for any desired period, for example l5 minutes or longer, and then the vacuum again broken. After the tubes are soaked in the saturant under atmospheric pressure for a brief period, they are removed, allowed to drain, cooled, trimmed and then4 stacked for shipment to the consumer.

If desired, after ythe saturation of the ilbrous conduits under vacuum, as hereinabove described, the vacuum may be broken and pressure which lmay be up to 100 pounds per square inch built up on the saturant by introducing pitch or other saturant or inert gas into The pitch or inert gas is introduced slowly into the tank so that the pressure builds up gradually. Operation in this manner is particularly suited to the saturation of very dense conduits. The pressure on the saturant in which the conduits are immersed after the conduits have been subjected to vacuum 'saturation as hereinabove described, causes the introduction of maximum amounts of saturant into the conduit walls. Y

In the preferred embodiment illustrated in the drawings, the invention is shown incorporated in the production of a brous conduit saturated with a bituminous material and the present disclosure will be confined to the present illustrated embodiment of the invention. It will be understood', however,` that the novel features and im provements are susceptible to other applications, such, for example, as thel saturation of absorbent articles generally. Included in the scope of my invention is the saturation of conduits, piping and other conductors made of cement, concrete, cement-asbestos mixture, or other porous or absorbent articles capable of being saturated. The conduits produced by my process are not only resistant to external pressures, such as soil pressures, but by suitable choice of materials and saturating conditions, may be, made reslstantto high internal pressures and hence suitable for pipe lines conveying corrosive waters or the like. Hence, the scope of this invention is the saturatlns tank.

not confinedA to the specific embodiment herein described.

In the drawings, Figure 1 is a side elevation, partly in section, illustrating a preferred form 'i of apparatus forl saturating conduits in accordance with the process of this invention, and Figure 2 illustrates a modified form of apparatus for practicing this invention.

In the drawings, reference ynumeral l indicates a pump communicating with a source of supply of saturant, and a pipe pipe connects with pipe\ leading into the base of a vertical tank 3. Pipes li and 5 have valves 6 and 1 therein. A valve-controlled discharge pipe 8 communicates with pipe 4 and leads to a storage tank `(not shown) or other point of disposal of residua1 pitch or other saturant in tank 3. The tank 3 is preferably made of a height such as to accommodate a maximum barometric column of the saturant. In the case of coal tar pitch of 1.2 specific gravity, the tank is made approximately 38 feet high so that a maximum barometric column of the saturant.: approximately 28 feet high, may rise therein, and a considerable evacuated space provided above the column of saturant.

Tank 3 may be heated directly by burners ll disposed about the base andv sides of tank 3 or may be steam heated, e. g., by a steam jacket or coils. Gaseous or liquidfuel may be fed to these burners through valve-controlled pipe l2, the products of combustion passing through a jacket ill surrounding the tank. Cover i3 provided with a valve-controlled vent 53 for venting the tank to the atmosphere seals the top of the tank. In the drawings the cover is shown as bolted to the tank, as indicated by reference numeral M, a gasket being inserted between the cover and ange l5 of the tank to give a gas-tight joint. A thermometer-well i6 is formed in the top of the cover. The top of the cover is also provided with an eye bolt i1 permitting ready removal of the cover from and replacement on the tank. A port I8 n'ear the upper edge of tank 3 communicates by means of pipe i9 with the receptacle 2l, having sight glasses `Z0 permitting visual inspection of any vapors and foam which may come over from the saturating tank 3. A valve-controlled drain pipe ll leads from receptacle 2l, permitting removal of ,any liquid which may collect in the receptacle.

Pipe 22 connects the receptacle 2l with a, safety tank 23. This tank functions to collect any foam coming from the saturating tank and prevents the entrance of this foam into the vacuum line 2B, leading from trap l2 to vacuum pump 25. Trap 42 "is provided with a valvecontrolled draw-olf Y3,6. Discharge of the contents of tank 23 may be eiected through valvecontrolled pipe 26. pipe d3 passing through condenser 44 connects the safety tank 23 with,V trap 42. A baille plate-45 in' trap 42 prevents ow of entrained condensate into the vacuum line 24.2

The conduits may bel supported in'a perforated basket or other device 21 resting von suitable brackets or supports 2li-bolted or otherwise secured to the sides of tank 3. A grid 29 rests on' supports 28. This grid carries the weight of the basket 21. Secured to grid 29 is the piston rod 3| of a hydraulic or pneumatic cylinder 32 provided With inlet and outlet ports 33. Operation of the cylinder 32 by the admission and y' discharge ofl pressure uid through .ports 33 v causes elevation of the piston 3i with consequent elevation of the basket 21 into the space' 35 in the ltop of tank When the piston rod 3l descends, the basket 21 descends therewith into ythe lower portion of the tank 3.

Parts of the apparatus of Fig. 2 corresponding has been eliminated, the tank is provided with' a steam jacket 48 for heating the contents thereof and a kettle 49 of a capacity suflicient to hold the saturant fed to tank 3 communicates with the tank by means of a line '5l' leading into the base thereof. In the apparatus of Fig. 2, the basket of tubes is maintained at a, fixed point within the tank during saturation and is not moved up and down as in the case of the apparatus of Fig. 1. The level of saturant within the tank may be changed during the saturation so that the tubes are alternately contacted with saturant and subjected to vacuum or pressure. While the saturant may be fed into thetank 3 from kettle i9 disposed therebeneath by the vacuum created in tank 3 preferably a pump 52 is placed in valve-controlled line.5l to pump the saturant into the tank.

In operation of the apparatus of Fig.v 1, the fibrous conduits to be saturated, preferably in vertical position, are placed in perforated basket 21, and the basket then inserted in the saturatingA tank 3, resting on grid 29. Thereafter, cover i3 is suitably sealed onto the saturating tank. Cylinder 32 is operated so that the tubes are maintained in space A at the top of the tank..

The vacuum pump 25 is then started, causing the vacuum to gradually build up in the container and the container or saturating tank heated by means of burners H simultaneously with the building up of the vacuum. Preferably, before heating the container, a limited amountof saturant is admitted thereinto. 'I'he saturant in the base of the container servedv to prevent local overheating vof thel container Walls during the heating to drive out the moisture and occluded gas from the brous conduits, and prevents overheating of the brous conduits.

A vacuum of from 17 to 29 inches of mercury,

preferably above 26 inches of mercury, may bev maintained during the drying of the conduits. The heating of the conduits under vacuum is carried on until moisture and occluded gas are removed therefrom to the maximumpossible degree. Just how long this should take depends upon the porosity f the conduits, their initial` moisture content, etc.

For a fibrous conduit having about 1.6 cc..of voids per gram of tube wall and having a moisture content of approximately 5 to 6 per cent, heating from about;` 45 minutes to 2 hours should suiice. The optimum temperature in the container or saturating tank duringthe drying of the conduits will depend upon fthe percentage of water, size of voids, density of the material, time cycle, and other factors. Inone case, 140 F. was found to be satisfactory with a vacuum of 2'7 inches of mercury when drying conduits containing approximately from 5 to 8 per cent moisture and having 1.6 cc. of voids per gram of tube wall.

After the moisture and occluded gas have been removed, Ithe basket of brous tubes is lowered to the position indicated in Fig. 1 and the saturant .gradually pumped through pipes 3,5, whi1e.the

level of the saturant in the tank so that a subf were'consumed in submerging the tubes.

exposed portions of thefibrous conduits in thebasket2'l;' Thefiowmay be soF regulated that the saturant rises to a level above the tops of the conduits, -vas indicatedon the drawings, dur-` ing a. predetermined time interval. With con. duits having relatively open wall structure, satisfactory results have been obtained when the ow of saturant was regulated so that 6to 10 minutes r With exceptionally dense structures an hour or more may bey consumed in submerging'the tubes.J

Utilizing coal tar pitch having a melting point of about 158 F., the pitch is maintained in the saturating kettle at a temperature of -irom 275 to 350 F., preferably about 320 F. The conduits are permitted to soak in the saturant while the vacuum `is maintained thereon for a suitable periodof timefor example from 2 to 4 hours, and

thereafter cylinder 32 actuated to elevatev the basket of conduits into the space 35 above lthe saturant. Excess saturant drains from the conduits and the vacuum to which the conduits are subjected effects' the removal of any residual moisture or occludedl gas from the conduits. The

basket of conduits is then again immersed in'the saturant by lowering basket 21 into the position indicated on the drawings@ The basket may bey quickly moved from its position immersed in the saturant into the evacuated space 35 and then returned into' the saturant sothat the conduits are disposed only momentarilynin the space 3 5, orthe conduits may be maintained in the evacuated space for a considerable period of'time', oneV or two minutes, or if desired, for a period of an hour or longer After the soak period, the vacuum may'bereleased, cover I3 removedand the basket of saturatedv tubes orcorduits taken out` of the tank. They vmay then'be allowedto drain for from 2 to6 minutes or longer, e. g., 15 to120I minutes, cooled trimmed and stored for lshipment to the consumer. If desired, the conduits prior to nal draining may be given a wash ,treatment with bituminous saturant at a temperature higher than'the temperature of the s at'l urant in tank 3 to remove any foreign matter, such as lint., carbon,` etc.,` adhering to the saturated tube walls Ii desired, the basket of conduits Ymay maintained at the base of the tank during the vacuum drying, and after the drying the saturant gradually introduced while. 'maintaining a' vacuum in the tank. Further Ithe basket of tubes may be dried while supported inthe top of the tank,

saturant/run into the tank to a level beneath the baselof the` tubes and then the tubes gradually immersed' by lowering the basket of tubes while maintaining vacuum in lthe tank.

In the apparatus of Fig. 2, the basketof tubes 'is inserted' inthe tank, the cover of therank sealed thereonV and vacuum gradually built up to a maximum and maintained until the tubes are dried, Thereafter pump 52 progressively introduces the saturant into the tankrwhile thevacuum is maintained in the 'tank. The tubes are then permitted to soak while the vacuum is maintained. Thereafter the saturant is drained from the chamber 35 through pump 52vv by opening the valve in line 5 I, the height of the saturant in chamber 35 above the. level of saturant in tank 49 being greater than a barometric column. vThe tubes are then subjected lto vacuum .for the desired. period of time out4 ofl contact with theA saturant. saturant isv then again progressively introduced into the tank. After. the desired soak period, the vacuum may be broken, the saturant returned to' kettlev 49 andthe saturated tubes Withdrawn. y

In the case ofthe apparatus if Fig. `1, after saturation, the saturant remaining in tank 3 is permitted to return to its source by breaking the lines -5 and 4, respectively. If desired, the pitch remaining in the saturating tank may be drained f vacuum in tank 3 and opening valves I and i in ow while the vacuum is maintained substantially constant at from 23 to 29 inches of mercury. After the saturant has reached a level such that the conduits are completely immersed, the ilbrous conduits are permitted to soak for aperiod of from l 15 minutes to an hour or more while the vacuum ismaintained at from 23 to 29 inches. Thereafter, the vacuum is broken and the pitch or other saturant drained from the tank into kettle I. The conduits remain in tank 3 subjected to the atmos'pheric pressure therein. The tank/isthen again evacuated and while maintaining a vacuum of from 23 to 29 inches, pitch is progressively introduced thereinto 'from kettle I until the level of the pitch .in thetank I3'rises lto a point such that the conduits are completely immersed in the saturant. The vacuum is then again released, the conduits permitted to soak for a brief period in the saturant and thereafter the saturant removed. The saturated conduits are then removed from the tank, permitted to drain, cooled, trimmed and stored for shipment to the consumer. Saturation of the conduits may be eiected by placing them in the top portion of the saturating tank, sealing thel cover, opening vent 53 (Fig. 2)

and then 'pumping saturantinto the tank until it is lled, the air in the tank escaping through vent 53. Thereafter the vent 53i's'c1osed and the level of the saturant permitted `to f'all to its baro' metric height, the bottom of the column being sealed by the liquid in tank l5. Thus a vacuum will be created in the ,top portion of the tank. The vacuum pump may be operated to maintain a subs tantially constant vacuum during the evacuation of the pores or voids of the conduits. The conduits may be placed in the base portion ofthe tankwhich is illled with saturant while vented to the atmosphere, the vent closed and the 4column of saturant permitted to fall to create a vacuum urant followed by periods during which the conduits out of .contact with the saturant are s ubjected to vacuum or atmospheric pressure, or the conduits may be vmoved while the level of saturant may bel maintained constant, or both the level of saturant and the vconduits may .be moved relatively to each other. In all procedures, the comhination 0I' long time of immersion of the nbrous I5 conduits in the saturant and the pulsation of the y saturant into and out ofthe side walls of the conduits due to the change in pressure to which the conduit Walls are subjected by immersing them in the saturant, subjecting them to vacuum or atmospheric pressure, and then again immersing them in the saturant under vacuum progresses through the cycle of saturating operations and results in thoroughly saturated conduits.

In the specification and drawings the saturation of conduits while maintained ina vertical position has'been described and shown. Such position of the conduit has several advantages and is therefore preferred, but it will be understood that the conduits during drying and saturation may be maintained in a horizontal position or a position inclined to the horizontal'. Among the advantages of maintaining the conduits in vertical position may be mentioned; the necessary apparatus occupies smaller floor space, ready egress of air from the wall of the conduit is permitted, lcontact ofA the'saturant with the conduit walls is facilitated, and tendency of the conduit to bend or deform is lessened. Settling of free carbon on horizontal surfaces is also obviated. r

In accordance with one example of practicing this invention, a conduit containing about 9 'per cent moisture and havinga porosity of about 1.6

cc. of voids per gram of conduitwall was placed l vertically in a saturating tank and dried while a vacuum of 29 inches was maintained in the tank. During the drying, a body of pitch at a temperature of about 320 F. was disposed approximately 2 inches below the bottom of the conduit. The conduitwas maintained under vacuum for approximately 2 hours. Thereafter, coal tar pitch of Aa specific gravity of 1.23 at 60 F., a

melting point of 158 F. (cube .in water), and" having a free carbon content of 6.4 per cent, was gradually introduced intoY the tank by( the vacuum maintainedl in the tank, this vacuum being maintained substantially constant at 29 inches. Thirty minutes were required for the introduction of the pitch into the tank. The conduit was permitted to soak in this pitch maintained atv a temperature of approximately 320.'

F. for four hours and the vacuum was then brok'- en, the pitch drained out of the saturating tank, the conduit drained andcooled.

'Ihe conduit on a bone dry basis absorbed 230 per cent saturant. 'Sections were cut from the top, middle and bottom of the conduit and immersed in distilled Water for periods of 24 hours and 48 hours and the following results obtained:

uum of 29 inches of mercury in thetank. The' con'duit was permitted to soak in the pitch under vvacuum for approximately 'one and one-half hours. Thereafter, it was moved from the saturant into the vacuum space above the body of saturant and maintained under vacuum for about 40 minutes. It was then slowly vimmersed in the pitch so that it took approximately 12 minutes for the conduit to be completely immersed. After the conduit was thus immersed, the vacuum was gradually reduced to atmospheric pressure, a period of 50 minutes elapsing during the reduction of the vacuum to atmospheric. The conduit permitted to soak at atmospheric pressure for 40 minutes, then withdrawn, drained, and cooled. The conduit prepared in this manner was found to absorb 258 per cent pitch. Sections cut frcin the top and bottom of the conduits and immersed in distilled water maintained at' a temperature Aof 78 F. for 24 and 48 hours showed water ab- Conduits having approximately 8 per cent moisture and about 1.3 oc. of voids per vgrani of tube` 4 wall were saturated in.l accordance with this in- `vention and absorbed from about 180 to 190 per cent' saturant, based on the bone dry weight of the fibrous conduit. Sections through the top and bottom of the conduit were immersed Afor 24 hours .in distilled water maintained at a temperature of '77 F. with the following results: The

section through the top of the conduit absorbed 0.23 per cent of water and the section through the'bottom absorbed 0.19 per-cent of water.

Conduits having approximately 7 perv cent moisture and less than 1 cc. of voids per gram of tube wall (very dense conduits) were saturated in accordance with this invention and absorbed per cent saturant, basedron the bone dry weight of the conduit.

In Figs. 1 and 2, lthe tops of the tubes are indicated as lying just below the surface of the saturant. The upper ends of the tubes are, therefore, subjected to a liquid pressure corresponding to only a few inches depth of saturant, whereas the bottom endsare subjectedto a liquid vpressure corresponding to approximately nine feet depth of saturant (assuming a tube length of eight feet). In some cases it may be desirable to subject the tubes to considerably greater liquid pressures. This maybe accomplished by locating the supports 28 at the bottom or at an intermediate saturant. Pressures considerably lgreater can,

course, be attained by making tank 3 much deep- 8' point in tank 3 and lowering the tubes to that level. In. the case in which saturant is allowed to rise to the maximum barometric level (approximately 28 feet depth for pitch of 1.2 specific` gravity) the lower ends of the tubes would be subjected to pressure corresponding to approximately 27feet depth of saturant; the-upper ends (assuming 8 foot tube iected to a pressure of approximately 19 feet of of er, e. g., 60 feet, and pumping in 'saturant to a depth of approximately 50 feet. Ordinarily, however, it will be more convenient to attain such pressures by pumping saturant or inert gas-into the `tank 3 until the desired pressure is obtained. g It will be noted that the process of this invention results in a more thorough saturation of absorbent articles than prior processes, requires materially less time for efiicientsaturation and' impregnation, andinvolves comparatively simple and compact apparatus for its practice. Further, the process of this invention results in substantially uniform saturation from vend to end of the article with a material improvement in the waterproofness properties of the brous conduits or other porous article saturated. From fibers and bonding with voids or pores substantially coal tar pitchv or other saturant employed; has

the examples of saturated conduits given above, it will be noted that the variation in the amount of water absorbed by the top and bottom portionsv of the conduits, proofness testis from 0.04 per cent 'to 0.38 per cent, less than half of one per cent variation. Itis evident,-therefore, that the conduits are substantially uniformly saturated throughout their length. The conduit of this invention has its completely filled with,4

the coal tar pitch or other saturant covering the the pitclr'in the voids. Hence, the brous base is effectively waterproofed and protected against corrosion, abrasion, and soil'pressures. This is-evidenced by -the water-absorption tes'ts described above.

The conduit of this invention, saturated with coal tar, pitch,'absorbs materially less moisture;

is more resistant to corrosion, abrasion, and soil pressures; and is of greater tensile and compressiverstrength thanthe 1saturated conduits heretofore known to me. It is also much more resistant to attack by moldsg'fungi, and all cellulose-destroying organisms;-

It is to be understood that this inventiony is not restricted to the presentgdisclosure otherwise than as dennedlbythe appended claims.

I claim: I f .1. The process otffsaturating conduits which comprises immersing the conduits in'a body of saturant-'maintainedjunder vacuum, and while continuously maintainingl said vacuum the impregnation removing the 'conduits from the body of saturantjsubjecting them to vacu um and then again-'immersing them into the body of'saturant.

2. The process of saturating absorbent articles whichrcomprlses immersing the articles in a body of saturant maintained inl a container having an evacuated space above the body of the saturant, soaking the articlesfin'thesaturant while maintaining thein body of saturant, moving body of saturant into the space thereabove and `thereafter again immersing the articles intothe 1 body of the saturant.

3. The process, of saturati'ng porous articles lengths) would be subf .moisture and occluded gas container x until the when subjected to the water- 1 during f' 'stationaryfwithin the 'v the articlesfrom the l' vby removing moisture and occluded gas from tainer having an evacuated space above the body of the saturant, moving ,body of the saturant into 'and thereafter again immersing the articles into the body of the saturant.V

the articles from the the space thereabove,

4. 'I'he process of saturating absorbent material which comprises placing the material in a container, `evacuating the container to remove from the absorbent material. while maintaining vacuum thereon, progressively introducing the/saturant into the mersed and anevacuated space above the material is provided, moving said material from the saturant into theeevacuated space and again immersing the material into the saturant in the container. l

5. The process of saturating absorbent material which comprises placing the material in a saturating tank, evacuating thetarikywhile heating it and thus' removing moisture and occluded gas lfrom the' material, progressively introducing the saturant until the material is immersed and while maintaining vacuum in the tank, soaking the material in the saturant after the introduction of the saturant into the tank and while maintaining the vacuum in said tank, subjecting the material to vacuum conditions out l of contact with the saturant 'withoutinterrupting the vacuumin the tank and then again immersing thev materialin the saturant. i 6. The process of saturating absorbent articles which comprises placing the articles to be saturated in a saturating tank, evacuating said tank to remove occluded gasfrom said tank, progressively introducing saturant into said tank at a controlled rate of flow while regulating the vacuum so that a substantially constant vacuum is maintained on the articles during the introduc-v tion of saturant into the tank, the amount of saturant introduced being suillcient to completely immerse said articles and leave \anA evacuated space above the level of the saturant, moving the articles from the saturant into the evacuated space thereabove and thereafter again immersing the articles in the body of the saturant.

'1. A process of saturating fibrous conduits .with bituminous saturant which comprises evacuating the voids of said conduits, progressively introducmaterial is completely `im ing bituminous saturant into-.said voids while maintaining the fibrous conduits under vacuum, permitting the conduits to soak in the saturant maintaining vacuum` on the saturant while the conduits soak therein, then subjecting the conduits to vacuum conditions out of contact with the saturant without interrupting thel vacuum under which the fibrous conduits are maintained duringtheir soaking and thereafter continuing the introduction of saturant into said voids. l

8'. A process of saturating ilbrous conduits with coal tar pitch which comprises drying the conduits, immersing them in a body of coal tar pitch maintained in a container having an evacuated space above the body of pitch, moving the conduits from the space there above, to subject them to vacuum conditions in said space and then again immersing the conduits in said bodyof coal tar pitch.

9. The process of saturating fibrous conduits with bituminous saturant which comprises heat ing the fibrous conduits, thereafter while still hot subjecting the nbrous conduits to vacuum therethe body of pitch into the evacuated4 conduits, thereafter contacting the conduits with bituminous saturant while maintaining vacuum in the saturating zone, without interrupting the vacuiun to which the brous conduits are subjected while contacted with the saturant, subjecting the partially saturated conduits to vacuum conditions out of contact with the saturant, thereafter again contacting the conduits with the saturant and maintaining` them in contact with said saturant until the voids. are substantially completely filled with saturant.

10. The process of saturating porous material which comprises progressively contacting the materialwith liquid saturant while the portions not contacted are subjected tovacuum, after all portions to be saturated have been contacted with saturant and without interrupting said vacuum, moving the partially saturated material out of contact with the saturant, and subjecting it to vacuum maintaining the material out of contact with the saturant while subjecting it to vacuum and thereafter again contacting the material with.

saturant.

' 11. The process of saturating brous tubes with bituminous saturant which comprises gradually immersng the brous tubes in the bituminous saturant; maintaining vacuum on the bodybf saturant in which the tubes are immersed while continuously maintaining said vacuum, removing the tubes from the body of saturant and subjecting them to vacuum conditions out of contact with the saturant, and thereafter again immersing the tubes in the body of saturant while subjecting to vacuum said body of saturant and the tube walls as they are gradually immersed in the saturant.

12. Th'e process of saturatingbrous conduits which comprises immersing the conduits in a body of saturant maintained in a container having an evacuated space above the body of saturant, soaking the conduits in the saturant while maintaining them within the body of the saturant, moving the conduits from the body of saturant into the evacuated space thereabove, thereafter again immer-sing the conduits into the body of saturani: and removing the saturated conduits from the body of saturant.

STUART P. MILLER.

CERTIFICATE' or coRREc'rloN.

Patent No. 2, 012,968. C A A September 3, 1.9.35.

STUART P. MILLER, I

lt is hereby certified that error appears in the above numberedv patent requiring correction as follows: In the grant and heading to the printed specification, title of invention, for "SATURATING FIBROUS CONDUITS AND PROCESSES 0F MAKING SAME" read SATURATED FIBROUS CONDUITS AND PROCESSES 0F MAKING SAME; page 3, first column, line 23, for "of" read or; and 4second column, line28, after "may" insert the word be; and line 63, for "heater" read hears-(hooge 7, 4first column, line 73, -right section of table, 'for "2.98" read 2.92; line 7 4, same section,v

for "2.82" read 2.88'; and that thesad Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the i Patent Office.

sigma and sealed this sth day of october, A. D. 193s..

. Leslie Frazer l(Seal) Acting Commissioner of Patents.

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