US2096888A - Process of saturating fibrous conduits - Google Patents

Description

e. EMBERG Oct. 26, 1937.

PROCESS OF SATURAT'ING FIBRQUS CONDUITS Original Filed May 27, 1952 r CONDENSER OIL a; WATER COLLEtTO/f TRAP INVENTOR GEORGE EMBERG Y ATTORNEY Patented a. 26, 1937 UNITED STATES 2,096,888 PROCESS OF SATURATING FIBROUS connurrs George Emberg, Chicago, Ill., asslgnor to The Barrett Company, New York, N., a corporation of New Jersey Original application ma 21, 19st, ski-in No. 613,937. Divided and this application Augu t 13,1935, Serial-No. 35,991

8 Claims.

This invention is directed to the saturation of absorbent conduits, and more particularly, to a batch process of saturating and impregnatingflbrous conduits employed to conduct and-protect 6 underground cables, telephone lines, electric light and other conductors and for the formation of I drain pipes utilized for the discharge of corrosive liquids to render them substantially waterproof and resistant to abrasion, corrosion, and condi- 10 tions encountered underground by fibrous conduits.

The fibrous bases of the conduits for the preferred embodiment of my invention may be prepared in any well known manner. For example,

newsprint and paper pulp or other fibrous mate-. rial maybe beaten in the usual paper heaters and the resultant stock screened and then pumped topaper cylinder machines and there formed into wet felts or paper.

about a cylindrical tubeor 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 fibrous base of course, be prepared in other known manner.

Such conduits are made in several sizes, varying from 2 inches to 6 inches or larger in external diameter, have an average wall thickness of approximately of an inch and are usually produced in 5, 6, and 8 foot lengths. I Thewall thick 0 ness of the conduits may, of course, be greater or less than, of an inch and other dimensions may vary. As they come from the drying kilns, they usually contain from 5 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 fibrous conduits may vary within wide limits from a very dense wall of a density corresponding to hard wood and exceedingly dimcult 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 tothat of roofing felt, which will readily absorb bituminous saturants. Samples of prescut commercial fibrous conduits have been tested and found tovary from substantially less than 1 cc; of voids per gram of tube wall to 2.8 or more 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 0., cooled, desiccated,

and thereafter weighed. It is then immersed in kerosene, maintained at a temperature of 25? 0., for 18 hours. Thereafter, the sample is removed from the kerosene, drained in vertical position for The wet paper may be wound (c1. aivo) 30 seconds, and again weighed. The difference in weight represents the kerosene absorbed. This difference in weight in grams, divided by the specific gravity oi theikerosene, corresponds to the cubiccentlmeters'oi' kerosene absorbed. This,

volume in cubic centimeters, dividedby the original weight in grams, "gives. the voids in cubic centimeters per gram. k The fibrous conduits. as they come from the drying kiln, containing .pregnated with water gas tar; pitch by immersing them in tanks of molten pitchmaintained at atmospheric pressure or pressure. above atmospheric and at a -temperatureiof 300 F. or upwards. The conduits have in many cases been allowed to soak in the molten-pitch for from '1 to 12 hours, then withdrawn-,andpermitted to drain to remove excess saturant therefrom.

This process of saturating fibrous conduits, it will be noted, requires the soaking ofithe conduits for long periods .of time'to obtain satisfactory penetration or-the 'saturant throughout the walls of the conduit. In the practice or the process, numerous dimculties are. encountered, among the most important of, which maybe 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 bythe fibrous walls. This, I have found, may largely be attributed to the moisture content of the fibrous tubes;'

(2) Building up ofthe-xi-iree carbon" con- .tent of the pitch due to the prolonged maintenance of large bodies of pitch in which the conduits are immersed under heat, resulting in de composition of the pitch. Increase in the "free carbon content of the pitchgdecreases the penetrabllity oi thesaturanty and results in carbon deposits on the walls oif conduit, preventins entrance of the saturan't and resulting in deiectively saturatedconduits, i. e., conduits having white spots" within the walls." The term i'ree carbon? is used ill-Hie sense common in'the coal tar industry to indicate material contained in the bituminous sat nt which is insoluble in benzol or carbon bisulflde. It is commonly determined as descrlbed, .by Weiss (Journal or Industrial and En meeri c che ist vol. 10, 1918, pages 736 and 820, Test Di). "It comprises high-molecular carbon compounds otlow solubility, carbon, and other insoluble mate ial; (3). Unsatisfactory saturation of the conduits due to the fibrous walls not absorbing suiiicient' from 5 to 8 per cent of moisture, have heretofore commonly=-been imsaturant to render them substantially waterproof. Conduits which are not adequately saturated do not attain maximum strength and resistance to deflection or deformation; and

(4) In the case of saturation of conduits under 7 by distilling tar derived from carburetted water gas made by enriching blue gas with products of pyrogenic decomposition of petroleum oils. The oils constitute the chief source of tar present in the carburetted water gas. Water gas tar pitch is, therefore, essentially of petroleum origin and it is recognized that water gas tar pitch differs materially in composition from other pitches, particularly coal tar pitches derived from the distillation of tar obtained from coal distillation gases. Water gas tar pitch has been employed for saturating fibrous conduits largely because of its relatively low free carbon content (about 2 to '7 per cent); its improved waterproofing properties as compared with asphalt; and its capability to protect the fibrous base against molds and fungi. While in some cases asphalts have been employed for .the saturation of conduits, generally speaking, they are less satisfactory than pitch in that they are less waterproof and donot effectively withstand and protect against molds and fungi and other cellulose destroying organisms.

In order to satisfactorily protect cables'and are subjected to determine their waterproofness is to immerse them in distilled water, maintained at a temperature of approximately 77 F. for 48 hours, then ascertain the percentage increase in the weight of the conduit and thus arrive at the amount of water absorbed thereby. Present conduits, saturated with water gas tar pitch, have been tested in this manner and many have been found to absorb in themeighborhood of 12 per cent of water. At the present time, it is generally 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 satisfactory waterproof conduit; a conduit absorbing not more than 4 per cent moisture under these conditions is regarded as eminently satisfactory. It should be noted that as indicated hereinabove, many of the saturated fibrous conduits now made, when subjected to the waterproofness test briefly described above, show an absorption of moisture substantially in excess of 4 per cent, many of them absorbing 12 per cent and more moisture. In general, the lower the water absorption, the more satisfactory is the product.

In the impregnation of porous articles with saturant.

bituminous saturant, twoof 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 in the pores.

Air and water vapor in the pores of the material tend to prevent entrance of the saturant, and water on the material surfaces tends to prevent wetting of the surfaces by the saturant.

When saturation is attempted at atmospheric pressure, the major portion of the water may be removed by-long soaking in the hot saturant at a temperature above the boiling point of water. The escaping steam carries with it some air. The removal of water by this means is timeconsuming and air is not completely removed. By the heretofore commonly practiced methods of saturation, therefore, the voids of the saturated article are incompletely filled with saturant.

If it is attempted to improve the degree of saturation by applying pressure, some improvement is found, but saturation is still imperfect.

The cfiect of pressure is, by forcing additional release of pressure, the compressed air and water vapor expand, forcing pitch out from the material, thereby reducing the degree of saturation and even distribution of the saturant.

My invention largely or entirely eliminates these disadvantages and produces an article the voids of which are nearly or completely filled with Such articles are more resistant to water-absorption, abrasion, deflection, and deformation. In the process of my invention, the walls of the fibrous conduits are not subjected to pressure or other conditions which would cause densification or compression of the tube walls with consequent increased resistance to absorption,of saturant, but on the contrary the pores or voids are evacuatedduring saturation, materially increasing the absorbing capacity of the tube wall. Moreover, my process as, compared with prior procedures minimizes the pumping and other handling .of saturant.

In accordance with this invention a batch of conduits is first dried. The drying of the conduits may be accomplished in any desired manner, as for example, by permitting the conduits to soak in hot saturant or by subjecting them to heat out of contact with the saturant or by soaking the conduits in the saturant which will be employed for saturating the conduits. The drying of the conduits may be carried out under vacuum which may be gradually increased to a maximum, say 28 to 29 inches of mercury, and the 'conduits held at this vacuum while heated for a period long 'enough to remove substantially all water, water vapor, and air from the voids.

A batch of the dried conduits is then immersed in a body ofsaturant. Afterimmersion vacuum is pulled on the body of saturant. A vacuum of from 17 to 29 inches of mercury may be maintained on the saturant. The higher the vacuum attained the more effective is the removal of air and water from the voids and the more complete is the absorption of saturant.

In the case where the conduits are soaked in the body of saturant employed for the saturation,

'when the soaking has proceeded to the point where the conduits are substantially completely dried, a vacuum is then pulled on the body'o saturant containing the conduits. j

The immersion of the conduits in the saturant prior to pulling the vacuum thereon results in the entire area of the conduit walls contacting with the saturant when the body of saturant is subjected to vacuum. Hence impregnation of the conduits by capillarity takes place slowly over the entire area of the walls of the conduits, giving substantially complete impregnation. The

' uum may vary from about forty-five minutes to two hours, depending on the density of the fibrous base of the conduits, the saturant employed, etc.

While the conduits are permitted to soak in the saturant the vacuum is broken. Interruption of the vacuum may be gradual by admitting air or other inert gas to the saturating tank so that the pressure above the saturant gradually. builds up to atmospheric while the conduits are immersed in the saturant. Increase in pressure of the saturant containing immersed conduits results in the forcing of the maximum amount of saturant into the voids of the conduits.

I The conduits may be permitted to soak in the saturantat atmospheric pressures or pressures above atmospheric and then removed.

In the practice of this process a body of saturant may be. maintained in a suitable container equipped with vacuum producing means and successive batches of conduits introduced and immersed in the body of saturant, vacuum pulled on the body of saturant after immersion. and after saturation is completed the vacuum interrupted and the saturated conduits withdrawn and a fresh batch of conduits introduced thereunto and the steps repeated. Removal ofthe saturant Coal tar pitch, preferably a pitch having a melting point of from to F.'may be used as a saturant in the process of this invention. Pitch of a melting point as high as 225 F. may be employed in special cases, e. g., with conduits having large size voids. 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, and may be employed to saturate fibrous conduits in accoTdance with this invention resulting in a more waterproof, stronger and otherwise improved conduit. Best results are obtained using pitches having a relatively low free carbon content. Pitches of free carbon content up to from 15 to 25 per cent, or even higher may be used to give commercially satisfactory satutar undergoing distillation, is employed as the saturant. Pitches made by a low temperature vacuum di rbon content and I have found that such pitches are particularly suitable as the sat- 'perature than would be methods of distillation.

stillation process are characterized by' urant for fibrous conduits. For'example, such a. pitch of 149 F. melting point (water bath? had a free carbon content of from 5 to 9 per cent;

such pitch of 158F. melting point (water bath) had a free carbon content of from Ste 9 per cent; such pitch of 226 F. melting point (air bath) had a free carbon content of from 11 to 15 per cent; and such pitch of 291 F. melting point (air bath) had a freecarbon content of from 16 to 21 percent. Pitches produced by distilling tar not under vacuum but by continuously heating the tar and then passing the heated 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. g., pitch produced in this manner having a melting point of-149" F. (water bath) had a free carbon content of from 11 to 13 per cent;

, tar used to make the pitch. Coke oven tar generally will not run much above 5 per cent free carbon; 1 per cent free carbon contentis very low for such tars.

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

(1)' In its manufacture, this pitch is distilled under vacuum and consequently at a lower temneeded to produce a pitch of the same melting point by the usual This low temperature causes minimum decomposition and hence minimum free carbon formation in the pitch. Low free carbon content is an aid in effecting com 1pileize penetration and saturation of porous mate- (2) In its manufacture, the pitch has been subjected to temperature and vacuum conditions such as to insure the substantially complete removal of oils which would be volatile under the conditions maintained in the saturating operation of my invention. Such pitches will be substantially non-volatile at the temperature and vacuum conditions encountered in the saturatingoperation, and consequently, will suffer minimum or substantially no loss from volatilization during Owing to low volatilization losses,

saturation. increase in free carbon", as well as change in melting point, during saturation will be reduced to a minimum.

Other methods of manufacture, such asisteam- 'or inert-gas-distillation, which effect distillation at relatively low temperatures, will yield-desirable pitches for my process for the reasons outlined above.

In the drawing, the single figure vis a vertical section partly in elevation of one form of apparatus for practicing the process of this invention. Referring to the drawing, reference numeral I indicates a saturating tank or container, pref erably of an over-all height of approximately 5 feet in excess of the length of the conduits or tubes to be treated. A cover 2 pivoted at 2' has a flange 3 arranged to be bolted or otherwise secured against vacuum leakage, as indicated at 4, to flange 5 on container I. In lieuof bolting the cover to the container, flanges 3 and 5 may be gro nd to form a. gas-tight joint when 4 other heating means may be employed. At a point near the base of the container, a screen or other suitable support I I is provided for a basket l2 containing the conduits I 3 to be impregnated. Heatinsulating material (not' shown) may be disposed aboutthe tank and other parts of the apparatus to reduce heat losses therefrom.

saturant .is supplied to the tank I through valve-controlled pipe I4, disposed at the base of the tank. An over-flow pipe I5 is connected to a side wall-of the -tank near the top thereof. This pipe may communicate with a storage tank (not shown) for the saturant. If desired saturant ma'y flow under gravity into tank I through a valve controlled inlet pipe III. Extending through the side of tank I, through a gas-tight packed joint, is a pipe I6. This pipe is communie cably connectedwith condenser I! having inlet 18 and exit IQ for cooling water or other medium. A suction pump-2| of any suitable type is con nected, by pipe 22 with the trap 26 into which leads section 23'of pipelli. A baiiie 28 in the trap 26 prevents flow of liquid through the trap into the vacuum line 22. Pipe 24,connects trap 26 with oil. and water collector 25. .Yalves 21 are disposed in pipe lines [6, 22, and 24 to control flow therethrough.

A conveyor chain or rope 3|, provided with a hook or engaging means 32, is designed to run over a guide pulley 33. This conveyor chain can be operated manually or by power driven means to protect it against corrosion, abrasion and soil to lower a basket of conduits or tubes into the saturant and the chain is then removed from the tion, and the basket then immersed in the saturant. As indicated in the drawing, the tank i has an over-all height such that a considerable open space is provided above the top of the conduits. The conduits may be permitted to soak in the saturant to eflect the drying thereof, steam beingvpassed through the jacket I to facilitate drying. In lieu of drying the conduits at atmospheric pressure, cover 2 may be seated on the saturating tank and the vacuum pump-started. Simultaneously with the vacuum to which the conduits are subjected, the container or saturating tank may beheated by passing steam through the jacket I. Instead of drying. the conduits by soaking them'in the saturant in tank I, the conduits may be'dried in any other, suitable manner.

After the drying is completed, the dried conduits which comprises substantially continuously Upon completion of the saturating operation, the

vacuum is interrupted, cover 2; opened and the conduits withdrawn. A fresh batch of dry conduits may then be inserted in the saturating tank I and the steps repeated.

In the drawing I have shown tubes or conduits treated in a vertical position. By suitable'changes in the apparatus I may treat them equally eflec- 5 tively in a horizontal position.

I have found as a result of work performed, a conduit having about 1.6 cc. of voids per gram of tube wall saturated in accordance with my invention with coal tar pitch (e. g. containing 10 642% free carbon) will absorb an amount of saturant equal to more than 200 per cent of the weight of the dry unsaturated base. In saturating' very dense fibrous conduits, for example, conduits having approximately 0.67 cc. of voids per .15 gram of tube wall, with coal tar pitch or other bituminous saturant, the amount of saturant absorbed will be found to be as much as eighty per cent by weight of the dry unsaturated base.

Prior processes of saturating fibrous conduits 20 ance with this invention, much greater amounts 25.

of saturant may be introduced into the conduit walls as compared with the saturation of conduits with asphalt in accordance with prior procedure's. Asphalt, as is well known, may conin less than 1% freecarbon or may. contain no 30 po-- es substantially completely filled with coal tar pitch or other saturant employed, and has the coal tar pitch or other saturant covering the pressures. Conduits resulting from the pratclce of the process of this invention absorb materially 40 less moisture, are more resistant to corrosion, abrasion, and soil pressures, are of greater tensite and compressive strength than the saturated conduits heretofore known to me. Such conduits saturated with coal tar pitch are also more-re- 45 sistant to attack by molds, fungi, and all cellulose-destroying organisms. ,.'I'his application is a division of my co-pendin application Serial No. 613,937 filed May 27, 1932.

It is to be understood that this invention is not 50 restricted to the present disclosure otherwise than defined by the appended claims.

-I claim:

1. A batch process of impregnating fibrous coni duits which comprises maintaining a body of sat- 5 urant, drying a batch of said conduits, immersing the batch of dried conduits in the body or saturant, thereafter subjecting the conduits, while immersed in the saturant, to vacuum conditions,

permitting thebatch of conduits to soak in the o0 saturant while vacuum conditions are maintained on the saturant until the conduits are substantially completely saturated, interrupting the vacuum while maintaining the conduits immersed in the saturant to complete the saturation of the g5 conduits and removing the saturated conduits from the saturant.

, 2. A batch process of saturating fibrous conof saturant, after each batch of dried conduits is immersed in the saturant subiectingthe body of saturant containing the immersed conduits to vacuum conditions and maintaining said vacuum 1 conditions until the conduits are substantially completely saturated, interrupting the vacuum while the conduits are immersed in the saturant, and increasing the pressure on the saturant to cause the entry of additional saturant into the conduit walls and complete the saturation of the conduits, and then removing the saturated conduits from the saturant.

3. A batch process of saturating fibrous conduits which comprises substantially continuously maintaining a body of bituminous saturant, successively immersing batches of dried conduits in said body of bituminous saturant, after each batch of dried conduits is immersed in the said saturant subjecting the body of said saturant containing the immersed conduits to vacuum conditions and maintaining said vacuum conditions until the conduits are substantially completely saturated, interrupting the vacuum while the conduits are immersed in the bituminous saturant, increasing the pressure on the said saturant to cause the entry of additional bituminous satura'nt into the conduit walls and complete the saturation of the conduits, and removing the saturated conduits from the said saturant.

4. A batch process of saturating fibrous conduits which comprises substantially continuously maintaining a body of coal tar pitch, successively immersing batches of dried conduits in said body of coal tar pitch, after each batch of dried conduits is immersed in the coal tar pitch subjecting the body of coal tar pitch containing the immersed conduits to vacuum conditions and maintaining said vacuum conditions until the conduits are substantially completely saturated, interrupting the vacuum while the conduits are immersed in the coal tar pitch, increasing the pressure on the said coal tar pitch to cause the entry of additional coal tar pitch into the conduit walls and complete the saturation of the conduits, and removing the saturated conduits from the coal tar pitch.

5. A batch process of saturating fibrous conduits which comprises immersing the conduits in a body of pitch saturant, while the conduits thereon, interrupting the vacuum to cause the entry of additional saturant into the voids of the conduits to complete the saturation thereof,

and removing the saturated conduits from the saturant. p

6. A batch process of saturating fibrous conduits' which comprises immersing the conduits in a body of saturant from the group: coal tar pitch and water gas pitch, while the conduits are immersed in the saturant subjecting them to vacuum conditions, soaking the conduits in the saturant while vacuum conditions are maintained thereon, until substantially complete saturation of the conduits takes place, interrupting the vacuum to cause the entry of additional saturant into the voids of the conduits to complete the saturation thereof, and removing the saturated conduits from the saturant.

7. A batch process of saturating fibrous conduits initially containing air and moisture, comprising providing a hot body of heat liquefied bituminous saturant, immersing the conduits in the body of saturant and permitting them to soak under atmospheric pressure in the saturant until substantially dried, pulling a vacuum on the body of saturant containing the dried conduits and permit-ting the conduits to soak under vacuum conditions until substantially complete saturation of the conduits has occurred, interrupting the vacuum to complete the saturation of the concomprising providing a hot bath of heat liquefied coal tar pitch saturant of the type produced by low-temperature distillation methods and having a relatively low free carbon content, drying the conduits to remove substantially all moisture, soaking the conduits in said hot bath of pitch while subjecting the bath to a vacuum, the conduits being immersed in the bath and the vacuum being initiated after the conduits have been whollyimmersed, interrupting the vacuum after the conduits have become highly saturated,- and continuing the soaking of the conduits, to substantially completely fill the voids in the walls of said conduits .without producing substantial thermal decomposition of the fibrous material, and then removing the conduits from the bath.

- GEORGE EMBERG.

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