US2581685A

US2581685A - Impregnation of absorbent material

Info

Publication number: US2581685A
Authority: US
Inventors: Wallace A. Mcmillan
Original assignee: Texas Co
Current assignee: Texaco Inc
Priority date: 1948-06-16
Filing date: 1948-06-16
Publication date: 1952-01-08
Anticipated expiration: 1969-01-08

Description

Jan. 8, 1952 w. A. MGMILLAN w IMFREGNATION OF ABSQRBENT MATERIAL Filed June 1s, 1948 R. m m .m

N A L. L.

VVA LA E ,4./140

BY i

' TTQENEYS Patented Jan. 8, 1952 UNITED STATES PATENT vOFFICE IMPREGNATION OF ABSORBENT MATERIAL Wallace A. McMillan, Glenham, N. Y., assignor to The Texas Company, NewYork, N. Y., a corporation of Delaware Application June 16,1948, Serial No. 33,310

9 Claims.

l This invention relates to the impregnation and coating of absorbent or fibrous materials with bituminous compositions to saturate and thenA surface coat the materials to render them waterproof and weather-resistant. More particularly, the invention relates to an improved process for saturating felt with a normally solid asphalt followed by surface coating of the saturated felt with a filled asphalt in the manufacture of asphalt roofing materials, including roll roofing and shingles.

This is a continuation-in-part of my co-pendl with asphalt and the percentage saturation of the felt are measures of the extent of moisture removal and asphalt impregnation of the felt in the saturating pro'cess, and have a direct bearing on the weather resistant qualities of the finished roofing. Roofing felt, as furnished by the manufacturer, contains a maximum of 5% moisture; but, upon subsequent storage and transportation, particularly under humid atmospheric conditions, the felt absorbs additional moisture until the moisture content may be in equilibrium with that of the atmosphere.

Numerous methods of driving oif the moisture from the felt prior to the saturating step have been proposed, such as passing the felt strip or sheet through drying ovens or over steam heated rolls; but in practice these methods add considerably to the cost of the process and do not a1- ways achieve the desired end. The general practice in roofing manufacture is to immerse the moisture-containing felt sheet, without previous drying, in a body of hot asphalt maintained at an elevated temperature of the order of o-450 F., and allow the heat from the asphalt to vaporize the moisture which is driven oil' in the form of vapor while the felt is simultaneously being impregnated with the molten asphalt. Considerable diculty due to foaming of the asphalt saturating bath has been experienced in the past with this method, requiring constant vigilance on the part of the operator to prevent the tank 5^`y`vrposals have heretofore been made to employ y tain anti-foam additives, such as stearic acid, in

the saturating bath; but such additives as have heretofore been employed have had to be used ,in such large proportions as to deleteriously af- "fect the properties of the finished roofing, particularly from the standpoint of weatherab'ility.

Following the saturating step, the travelling sheet of asphalt impregnated felt is thengi'ven a surface coating of a so-called filled asphalt, which v"is a mixture of molten normally solid4 hard' asphalt' (lower ASTM penetration) with a iinely divided ller of the character of pulverized oyster shell, dolomite, and the like. This is acjcomplished by premixing the filler with theV molten asphalt, and then flowing the resultant mix onto the travelling sheet. In practice, it is found that there is considerable air and water vapor entrainment in the highly viscous mix which shows up in the form of substantial vapor bubbles trapped in the surface coating. This affects the uniformity of the coating layer and con-l tributes to poor weatherability and blistering of the product in service.

tions and to provide an improved process of continuous manufacture of asphalt roofing at etlicient line speed, and which will insure the maintenance of the desired operating conditions in` both the saturating and coating stepsover long periods of continuous operation so as to give a 35..: of spotty operation.V

from foaming over, and often necessitating reducng the level or depth of moltenY asphalt in the saturating bathfwhile concomitantly reducing Another object of the present invention is to provide an improved combination of the saturating and coating steps to achieve a final product of improved weathering characteristics in uniform, easily maintained, continuous operation.

Still another object of the present invention is to improve the saturating process to uniformly maintain a higher percentage of voids filled with a particular grade of harder roll saturant to in- `sure improved weatherability of the final product.

A further object of the present invention is to also improve the coating step to substantially eliminate the entrainment of vapor bubbles in vthe surface coating.

Other objects and.. advantages of the present invention will be apparent from the following de? scription, the attached drawing and the appended claims.

In accordance with the present invention, it i It is accordingly a principal objectof the pres-V "'"ent invention to overcome the foregoing objec- Ithosta d `to the sheet a characteristic shiny wet appear. ance. By thus maintaining the saturating bath'YV m thtibath which ,contains al 'up to a height of 4 to 5 ft. resulting in overflow of substantial depth and at zal,temperatureofr l about 250-450 F., and preferably about 375-42@l F., and then withdrawing theinlpregnatedsheet with the substantial surface lm and' looping theY same to allow it to cool, the surface lm rapidly dries in to provide a saturated sheet whichlcan uniformly be maintained at a minimum of 85% or higher of voids lled with asphalt, eventh'fogh the Yline speedof the felt is increased over that heretofore pfl'misjsible. VIn addition;- byk utilizing a no rsl'nally `solid asphaltV having an ASTM pene'- tration (loo gramas" seconds) at 77 F. within the range of about"3 0`50'for the saturating bath, which lleretoforehas involved increased diliculties in nonluniforln operation, the finished .product llas'been foundl to be uniformly superior from poil'ltjofV freedom vfrom blistering on atmospheric exposure.y Inlraddition, it has also been foundthata very small amount of the liquid organic silicone V'of the 'order V of-0.l10parts per millionbybvolume based on the asphalt in the coating Vmix effectively prevents the permanent entrainnl'ent ofv vapor bubbles'in the molten mix when theller isincorporated therein, so that the ultimatesurface coating onA the impregnated felt sheet is substantially freefrom trapped vapor bubbles. j The combination of these steps enables a roofing material of high quality and improved weatherabilityto'be uniformly manufactured at higlllinespeed over substantial periods of continuol'sls'uoperation.

The invention 1s riioreV particularly' illustrated l in the attached drawingl which'is a' diagrammatic looper, the felt passes .throu'ghfpairs of Aguide rolls I3 V,and I4 into a pr'esatur'atingsectiont I5 of theY saturating'tank indicatedge'nerally atA I6.` As shown",V the 'pres'atur'ati'ng section I5 is of less depth' than Ythe main saturating section II of the tankA-` Each section is equipped with afseries of closely spacduppoif roll-eis (l tV and ja' lower serios of rollers I9, sqthat the rfelt travels over jan4 upper roller; thence downwardly into the molten asphalt and around a lower roller, and then back up `to the next upper rol-ler ill series, `to receive loops as indicated at'20. "l

The function of" Vthe I presaturatin y''saction4Y I57 is primarilyl'to eliminate moisture from vth v'felt als.

miizetionpeint Qf. @contained moisture, Wfl'il' some impregnation of tle'travolllfig `rolt with Viis- 'sol `a pluralitysof' immersions"while in the form of phalt occurs in this section, it is purposely designed of rather shallow depth, so that the depth of immersion of the felt is comparatively small, and the liberated Water vapor has only a limited distance to'travel to reach the surface of the molten asphalt and escape to the atmosphere. Even with this arrangelnenuA considerable diniculty has been encountered'in the past due to copious foaming of the saturating bath, with the foam on the surface of the bath often building from the tank if the level of molten asphalt is notV immediately lowered therein. It should be understood that a; presaturating section is not essentialto the present invention.

The asphalt saturants employed in tank I5 Vare the blown petroleum asphalts, or the blended lasphalts obtained by blending a steam reduced residual or asphaltic stock with a blown asphalt, and which are normally solid at atmospheric temperatures and possess an ASTM penetration (100- grams, 5 seconds) at 77 F. within the range of about 20- 125, and an ASTll/ly softening point (ball and ring method) within the range of 100-18'0" F. As discussed more in detail herein below, the asphalt saturant preferably has an ASTM Vpenetration at 77 F. of about 30-'60, since' the harder type asphalt saturant has been found to giveV improved weatherabilty when manufactured in accordance with the present invention. Also, in accordance with the present in-` vention, the asphalt saturant within tank I6 contains a very Vsmall amount of a liquid organic silicone of the order of about 0.1-10 parts per million by volume based on the asphalt in the bath".v This has been found to 'inhibit foaming such that "not more than an inch or two of foam is present on the surface of any portion of the bath during long'periods of continuous operation, thereby 'permitting the level of the bath to be uniformly maintained near the top of the saturating tank. For. example, in a-saturating' tank havin'ga total depth ofv about '7 ft. in the deeper saturating section I 7,- tlie level o'f molten asphalt may conveniently be arranged just below the upper series Vof rolls I3, providing a depth of immersion in' Vthe pre-saturating section I5 of about 21/2 ft. and irl -tll'e main saturating section I1 ofab'out 51/`'6ft; Ordinarily, the amount of the organicsilicone employed in the bath will be about one part per million by volume; although it is found thatfonce having dispersed this'anount of the organic silicone effectively throughout the saturating bath, its Yanti-foam properties will be preserved without further 'en'ce the saturatng section I1 of the bath.

As pointed 'out above, one of the features of the presfnt invention resides in the operation of 'the saturating step with the proper controlled amount of the organic silicone 'within the small critica-lly 'range' vspecified above, together with maintenance of the temperature and depth ofY the so Vthetraveling vfelt sheet is with-- dlflwp vthelfjtll iria `fcondtic'ln in which it retains a1 substantial,"` surface lm of molten Vvasphalt thereon; :providing 'a characteristic irglossy Wet or shiny appearance, which surface film then rapidly penetrates the Withdrawn felt. While the reason for this unusual effect has not been definitely ascertained, it is postulated that the organic silicone, in addition to inhibiting foaming of the bath, also inhibits the accumulation of a retarding or insulating film of water vapor on the surface of the immersed sheet, thereby permitting more rapid penetration of the impregnating asphalt and also enabling a thicker surface film of asphalt to be retained as the sheet is withdrawn from the bath, and then facilitating the rapid penetration of this surface film into the sheet. In addition to the eiiect on the glossy surface film, the use of larger proportions of the organic silicone also appears undesirable from the standpoints of deleteriously affecting the adhesive properties of the saturated sheet for the subsequent granular coating, as well as affecting the compatibility of the sheet for the subsequent filled coating. Whatever the action may be, it has been found that operation in accordance with the foregoing principles uniformly gives a saturated felt sheet with a minimum of at least 85% voids filled with asphalt and generally in excess of 87% voids filled.

The organic silicones useful for purposes of the present invention include any of the polymeric organic silicon oxide condensation products which have heretofore been proposed as anti-foam agents for certain organic liquids, particularly mineral lubricating oils at normalatmospheric or mildly elevated temperatures (see Trautman et a1. No. 2,416,504 and Larsen et al. No.y

2,375,007). structurally, these compounds are composed essentially of a plurality of silicon atoms linked together through oxygen atoms, with each silicon atom having attached to it at least one organic radical, these products also being known as organo-siloxanes. The oily liquid condensation products obtained by polymerization of organo-silane diols (each silicon atom having attached 2 organic radicals), such as, for example, the dimethyl silicone, are particularly advantageous for purposes of the present invention. As is well known, these compounds may be obtained by hydrolyzing a Grignard reaction product of an organic magnesium halide and an ether solution of silicon tetrachloride, followed by evaporation of the ether and condensation or polymerization of the resulting hydrolyzed Grignard reaction product by heat in the presence of air. The condensation process proceeds through a liquid product of lower molecular weight to a solid plastic of higher molecular weight. For purposes of the.present invention, the liquid organic silicones which are usually insoluble in heavy oils of the character of mineral lubricating oil are employed. A dimethyl silicone polymer obtained from the Dow-Corning Corporation under the trade name of Dow-Corning Fluid has been used with very satisfactory results. This liquid material is marketed in varying viscosities ranging from about 100 to 1,000 centistokes at 77 F. Analyses of representative samples of this material are as follows:

6 rated in the asphalt saturant by rst forming a naphtha or kerosene solution thereof, and then incorporating the resulting silicone concentrate in the molten asphalt. For example, a kerosene concentrate containing one part of the silicone to 999 parts by volume of the kerosene is then added in the proportion of 1 cc. of the concentrate to 1,000 cc. of the molten asphalt to give one part per million by volume of the organic silicone dispersed in the asphalt.

The saturated felt sheet Withdrawn from the saturating tank I8 with its glossy surface iilm, as previously described, then passes to a wet looper indicated at 22 where the travelling sheet is formed into a series of loops 23 providing time for cooling. The natural shrinkage of the asphalt, upon cooling, causes the excess surface film of asphalt to be drawn into the felt, thereby resulting in improved saturation.

The travelling sheet then passes by guide rolls 24 and 25 to the coating section Where a surface coating of filled molten asphalt is applied to both the top and bottom surfaces of the sheet. For this purpose, molten asphalt is fed from storage tank 2l into a suitable mixer or agitator such as the turbomixer indicated at 28, into which the finely divided solid llerfsuch 'as ground oyster shell, dolomite and the like, is supplied by the travelling conveyor 29. For example, a suitable coating mix may be composed of about 35-60% by weight of ground oyster shell, and about (i5-40% by weight of a hard coating asphalt having an ASTM penetration at 77 F. of about l5-25. The resulting mix from agitator 28 is supplied to the asphalt coating storage tank 30 from which it is fed to the applicators 3l and 32 extending across the top and bottom of the travelling sheet. The coating mix is applied to the travelling sheet at a temperature of about 350-400o F., preferably around 385 F., in order to secure satisfactory adhesion of the hard filled coating.

As noted above, considerable diiiiculty has been experienced in the past due to the entrainment of air and Water vapor bubbles in the viscous mix formed in agitator 28. A large proportion of these entrained bubbles persist in the coating mixture held Within storage tank 30 and then supplied to the applicators 3l and 32, with the result that the Surface coating layers applied to the travelling 'sheet have a characteristic mottled appearance due to the entrained vapor bubbles. This, of course, affects the uniformity of the coating even though subsequent processing may largely break and eliminate the trapped bubbles.

In accordance with the present invention, this difiiculty has been overcome by incorporating in the molten asphalt in supply tank 21 a very small amount of the same type of liquid organic sili-v cone used in the saturating bath. Here again, the proportion of organic silicone used is within the range of 0.1 to 10 parts per million based on the volume of the molten asphalt, and preferably about on'e part per million. By having the silicone present in the molten asphalt at the time the solid filler is mixed therewith in agitator 28, it has been found that vapor entranment in the viscous mix is substantially eliminated. The net result'is that the surface coating layers applied to the top and bottom of the travelling sheet are essentially free from entrained vapor bubbles, and desired uniformity of the coating across the width of the sheet is assured.

Following the application of the'top and bottom coating layers,. the travelling sheetv then passes. through. the coating. squeeze rolls Sindiing squeeze rolls closer together, a larger proportion of thecoating layers is removed to decrease the weight of the sheet per `unit area; and conversely by separating the squeeze rolls, the Weight of the sheet is increased. The travelling sheet is then subjected to finishing operations in a conventional manner. These operationsV are not illustrated since theyformno part of the present invention. Thus, where a mineral surfaced roll roofing or shingle is being manufactured, the mineral particles are applied to the upper surface of the sheet following the squeeze rolls 33. Where a smooth surfaced roll roong is being made, mineral particles are, of course, not added but a layer of talc is applied. The sheet is then run througha series of press and cooling rolls or drums, thence to a iinishingilooper where the nal cooling for handling takes place, and finally to a roll roong Winder or to the shingle cutter, as the Vcase maybe.

rIhe following example is given to illustrate the present invention. During the manufacture of a ninety pound'mineral surfaced roll roofing in accordance with the conventional old procedure, it was found that the line could not be operated at a speed of more than 135 ft. per minute, and, moreover, had to be stopped for short intervals'in order to prevent the saturator partper million by volume. Operation with this setup was compared'.y withV the operation, inithe`- absenceV of. the silicone, andY also Witha setup in;

' which the same'proportion of siliconewas added from foaming over. At this time, the depth of molten asphalt in the saturator had been reduced to'21/2 ft., and there was a blanket of foam on the surface thereof 4 to 5 ft. deep. One hundred ccs. of a kerosene solution of the dimethyl silicone polymer, prepared by adding one part of the silicone to 999 parts of the kerosene was then added to the` saturator in the presaturating section f 5 at the point Where the felt enters the asphalt; and the foam immediately subsided almost to the saturant level. Eight hundred ccs. of the kerosene-silicone concentrate were add'- tionally added at different points in the saturating tank and in the saturant storage tank (not shown but connected with the saturating tank I) so that the silicone was distributed, as quicklyas possible, throughout the saturator system holding 635 barrels of asphalt, thereby providing one part per million of silicone by volume on the basis of' the molten asphalt in the system. Within five minutes after adding the silicone, the line speed was increased to 185 ft. per minute, the. saturant level was raised to a point about 18" from the top of the tank, and there was not more than 1" of foam on the surface. of the saturant at any point in the tank. Moreover, at the endV of the tank where the saturated felt was withdrawn from the saturator, the surface of the. molten asphalt was free from bubbles. The withdrawnY sheet had a glossy wet appearancek which rapidly penetrated Yinto the withdrawn sheet. Production continued at a line speed of 185 ft'. per minute Without any further difculty, resulting in increased production by about 85 rollsV per hour. It was further observed.'A

that the asphaltsurface lm on the travelling4 sheet withdrawn from the saturator appeared Vto dry in more rapidly than during normal operto the coating storage tank -following thexmixing of. the. solid v filler with'. the coating asphalt. The presence of. entrained vapory bubbles on the.

coated surface of the travelling sheet persisted in both of the lastv mentioned operations, whereas withithe first mentioned operation in which the'silicone was present at the time of mixing the solidV filler with the asphalt, entrained bubblesin the coating were practically eliminated. The

coated'sheet passing to thesubsequent sections of the machine was smoother and brighter in appearanceA than in either of the'other two cases.

The following Table I sets forth data obtained` during the foregoing operations, with the data in column A representing operation in the absence ci" added silicone in boththe saturating' and coating sections, and the data in column Bf representing operation with added silicone in the saturant and also silicone added to the coating asphalt prior to mixing of the filler therewith.

TableV I Asphalt Saturant A B Dow-Corning Fluid, P. P. M. by vol None l Melting point, ball and ring, "F 119 120 Penetration at 77 F., ASTM 90 92. Flash, COC, F 530 550 Fire, GOC, F 630 650 Operating Conditions:

Asphalt level iu sature/tor low high Temperature in saturator inlet, F 450 450 Temperature in coating pan, F 385y 390 Line speed. itJmin 135 185 Depth of foam in saturator 4-5 1'. Tests on Saturated Felt:

Per cent voids lled 86 90 Per cent saturation 178 199 Test on Finished Roon Accelerated blistcring at 225 F Severe Slight The foregoing data shows that the very small amount of. added silicone has substantially no effect on the physical properties of the asphalt saturant except for an increase in the flash and fire points which is advantageous. Operation in accordance with the present invention gave a saturated felt having 90% of the voids lled with asphalt with a percentage saturation based on the weight of the felt of 199 representing a substantial improvement over the operation in the absence of the added silicone in the saturant. Moreover, the combination-cf the treated saturant with the treated coating gave a finished roofing ywhich showed only slight blistering in the conventional accelerated blistering test at Y225" F., in comparison to severe blistering for the finished roofing prepared in the-absence of the added silicone.

The data in the following Table II illustrates the effect of the saturant consistency on the blistering tendency oi roll roof-ings subjected to atmospheric exposure:

Table 'II Y ASTM Pene tration at 6 Months Atmospheric Exposure 75-90 30 No. of roll 'roolngs sampled 47 53 Per cent of samples showing severe to moderate blistering 89. 5 22. 5

Thus, of the large number of roll roongs pre.-` j

pared with the conventional asphalt saturant having a penetration of l-90 at `7'7" F., 89.5% of these showed severe to moderate blistering after six months atmospheric exposure. On the other hand, a large number of roll roofings prepared by the same procedure except employing a harder asphalt of about 30 penetration at 77 F. showed greatly improved weatherability,` as evidenced by the fact that only 22.5% showed the same degree of blistering after six months atmospheric exposure.

While the organic silicones have heretofore been proposed as anti-foam additives for organic liquids at atmospheric or mildly elevated temperatures, it could not be foretold in the absence of actual trial that these materials would function to suppress the copious type of foam formed on the surface of the molten asphalt saturant at the high temperatures employed. Moreover, it is considered truly remarkable that the very minute quantity of dispersed silicone within the range specified herein proved capable of handling this severe foaming problem, and at the same time, the desired physical properties of the saturant and the asphalt roofing were not deleteriously affected. Further, the added function of the silicone in providing a heavier surface lm of asphalt of Icharacteristic glossy appearance on the surface of the travelling sheet. emerging from the saturating bath, which then rapidly dried in during the subsequent cooling period to give substantially improved saturation and percentage of voids filled, was unexpected. Finally, it could not be predicted that the silicone, in the very small proportion employed, would satisfactorily solve the different problem of bubble entrainment in the coating section. The combined steps of the process, as herein described, have resulted in the uniform production of a high quality of asphalt roofing over long periods of continuous operation without difculty, and without the close attention on the part of the operators as formerly required.

Obviously many modifications and variations Y of the invention, as hereinbefore set forth, may

be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

l. In the manufacture of asphalt roofing, the method which comprises continuously passing a sheet of felt through a saturating bath of molten normally solid asphalt having an ASTM penetration at 77 F. of about 253-125 maintained at a temperature of 25o-450 F, and containing about 0.1-l0 parts per million by volume of a liquid dihydrocarbon silicone polymer having anti-foam properties in organic liquids and which is effective to substantially inhibit foaming of said molten asphalt bath, said bath being maintained of sufficient depth and elevated temperature to effectively eliminate moisture from the felt sheet and thoroughly impregnato the same with asphalt, withdrawing the traveling felt sheet from the bath while retaining a substantial surface film of molten asphalt on both sides thereof providing a glossy wet sheet which is then cooled to permit the surface film to rapidly dry in to provide a saturated felt sheet with minimum of 85% voids lled with asphalt, and then applying a surface coating to the sheet of a mix prepared by adding finely divided solid inorganic filler to previously mixed molten normally solid asphalt and about 0.1-l0 parts Der millionjby volume based on' the'asphalt of a liquid" dihydrocarbon silicone: polymer `having `anti-foam properties inorganic liquids` and which isl sufficient to inhibit entrainment of vapor bubbles in the coating.

2; The method accordingto claim l, wherein the asphalt in the Vsaturating bath has an ASTM vpenetration at 77. F. of about 30-60, and the silicone polymer is present in thefsaturatingbath in the proportion ofabout 0.1.to'lfpart per million by volume based on the asphalt.

3; -The method according to claim 1, wherein the saturated felt sheet passing to the coating step has a minimum ofV 87% voids filled with asphalt, and the silicone polymer is present in both the saturating bath and the coating mix in the proportion of about 1 part per million by volume based on the asphalt.

4. In the manufacture of asphalt roofing, the steps comprising continuously passing a sheet of felt at a depth of immersion not substantially exceeding about 21/2 feet through a presaturating stage of a bath of molten normally solid asphalt having an ASTM penetration at 77 F. of about 20-125 maintained at a temperature of Z50-450 F. and containing about 0.1-l0 parts per million by volume of a liquid dihydrocarbon silicone polymer having anti-foam properties in organic liquids, such operation being effective to vaporize moisture in the felt and provide rapid release of the water vapor from the bath without substantial foaming thereof, removing the felt from the presaturating stage and then passing the felt at a substantially greater depth of immersion more than twice that of the presaturating stage through a saturating stage of the said bath while avoiding the accumulation of a retarding film of vapor on the surface of the immersed sheet to thereby thoroughly impregnate the sheet with asphalt, withdrawing the impregnated sheet from the impregnating bath while retaining a substantial surface film of molten asphalt on both sides thereof providing a glossy wet sheet, and finally looping the traveling sheet to provide for cooling and the rapid drying in of the surface lm to give a saturated felt sheet with a minimum of voids filled with asphalt. Y

5. The method according to claim 4, wherein the asphalt in the bath has an ASTM penetration at '77 F. of about 30-60, and the silicone polymer is present in the combined presaturating and saturating bath inthe proportion of about 0.1 to 1 part per million by volume based on the asphalt.

6. In the manufacture of asphalt roofing, the steps comprising mixing at an elevated temperature finely divided solid inorganic filler with a previously mixed molten normally solid hard coating asphalt and about 0.1-10 parts per million by Volume based on the asphalt of a liquid dihydrocarbon silicone polymer having antifoam properties in organic liquids, and then applying the resultant mix at an elevated temperature as a surface coating to a traveling sheet of asphalt-saturated felt to provide a coating thereon which is substantially free from entrained vapor bubbles.

7. The method according to claim 6, wherein the coating asphalt has an ASTM penetration at 77 F. of about 15-30, the mix is applied at a temperature of about S70-400 F., and the silicone polymer is present in the coating mix in the proportion of about 1 part per million by volume based on the asphalt.

il L12 7Bf-Th method iazccording 'to laim I6, Vwwlrhlerein REFERENCES CITED v fthe 'liquid "dihydm'crbon'smcone palme? is a The following referencesare of recordinhe methyl silicone ',polymer, and .is'present 1n th me of this patent:

fcoaing "asphalt in'the rpropnrtton o about v Y part 13er million by'volumefbasedtonthe asphalt. 5 UNITED STATES PATENTS "1 5.9.;71he methodfawording ,tofclaim 4, rwlfusrein Number Name Date lthliquicl -ihydroca'rbnnsilicbne p'olymer is a. 1,667,201 Finley Apr. 24, 1928 iiimbhylsllcone'rpolymen and izpresent -in the 1,776,586 Heppes Sept. 23, 1930 mltenfaphaltfbathfinlthe,proportionfof-about 2,258,218 Roc-,how Oct. '7, 1941 11 -part'lpermillion by lvolma 110 2,322,059 Ruediger June 15, 1943 2,350,649 Spelshouse June 6, 1944 j; .gMcmmlAN. .2,375,007 Larsen May 1,1945

Claims

1. IN THE MANUFACTURE OF ASPHALT ROOFING, THE METHOD WHICH COMPRISES CONTINUOUSLY PASSING A SHEET OF FELT THROUGH A SATURATING BATH OF MOLTEN NORMALLY SOLID ASPHALT HAVING AN ASTM PENETRATION AT 77* F. OF ABOUT 20-15 MAINTAINED AT A TEMPERATURE OF 250-450* F. AND CONTAINING ABOUT 0.1-10 PARTS PER MILLION BY VOLUME OF A LIQUID DIHYDROCARBON SILICONE POLYMER HAVING ANTI-FOAM PROPERTIES IN ORGANIC LIQUIDS AND WHICH IS EFFECTIVE TO SUBSTANTIALLY INHIBIT FOAMING OF SAID MOLTEN ASPHALT BATH, SAID BATH BEING MAINTAINED OF SUFFICIENT DEPTH AND ELEVATED TEMPERATURE TO EFFECTIVELY ELIMINATE MOISTURE FROM THE FELT SHEET AND THOROUGHLY IMPREGNATE THE SAME WITH ASPHALT, WITHDRAWING THE TRAVELING FELT SHEET FROM THE BATH WHILE RETAINING A SUBSTANTIAL SURFACE FILM OF MOLTEN ASPHALT ON BOTH SIDES THEREOF PROVIDING A GLOSSY WET SHEET WHICH IS THEN COOLED TO PERMIT THE SURFACE FILM TO RAPIDLY DRY IN TO PROVIDE A SATURATED FELT SHEET WITH A MINIMUM OF 85% VOIDS FILLED WITH ASPHALT, AND THEN APPLYING A SURFACE COATING TO THE SHEET OF A MIX PREPARED BY ADDING FINELY DIVIDED SOLID INORGANIC FILLER TO PREVIOUSLY MIXED MOLTEN NORMALLY SOLID ASPHALT AND ABOUT 0.1-10 PARTS PER MILLION BY VOLUME BASED ON THE ASPHALT OF A LIQUID DIHYDROCARBON SILICONE POLYMER HAVING ANTI-FOAM PROPERTIES IN ORGANIC LIQUIDS AND WHICH IS SUFFICIENT TO INHIBIT ENTRAINMENT OF VAPOR BUBBLES IN THE COATING.