US2581640A

US2581640A - Bituminous composition

Info

Publication number: US2581640A
Application number: US612284A
Authority: US
Inventors: Fasold George Arthur; Harold W Greider
Original assignee: Philip Carey Manufacturing Co
Current assignee: Philip Carey Manufacturing Co
Priority date: 1945-08-23
Filing date: 1945-08-23
Publication date: 1952-01-08
Anticipated expiration: 1969-01-08

Description

Patented Jan. 8, 1952 UNITED} STATES PATENT OFFICE b view ng. Application August 23'," 1945,

Serial' N0.-612,284

' i 3 Claims.

This invention relates tosolvent' thinned-him minous composition adapted to be applied in a fluid or semifluid'state, th'esolventbeingvolatile so that, after application of thecom'position, the composition becomes stiffened due to' lo'ss of the solvent thereirom by evaporation; Thisfin've'n tion relates particularly to solvent thinned bituminous composition adapted for cold process" built-up roofing construction, In cold process built-up roofing construction the bituminous composition is thinned by means of a volatile solvent so that the composition is sufiiciently workable at atmospheric temperatures, or whenonly mildly warmed, to permit manual application of the composition for the purpose of bonding sheets of felt or the like together andprovide layers of waterproofing adhesive between such sheets of felt or the like in a buiid-up-type of bituminous roofing.

it is an object of the invention to aiford a solvent thinned bituminous composition suitable for application to provide a waterproofingtlayer for adhesively uniting the plies of a ibuilt-upiroofing, which bituminous composition as disposed in the fabricated built-dip roofing will have high fire resistance and will impart high fire resistance properties to' the built-up roofing asa whole, While the special bituminous compositionof this invention is especialiy' designed for usebetween plies oi built-up roofing, the special composition 'oi this invention can, if desired; be usedto provide a highly fire resistant surface coating of built-up roofing or to provide a highly fire-resistant; water-resistant adhesive for varioussheet ma-"- terials. i

In the construction of built-up roofing, the plies of felt or the like'aregenerallybonded to ether by so-called mopping-asphalt, namely roofing grade-asphalt having -a'soitening point or" about 140 F; to 206 Frand which can-readily be heatliquefied on the job andtspread with a mop or similar implement. Occasionally i the mopping asphalt contains a mineralfiller-such as. limestone dust or slate flour in an amou ntsuch as 28% to 30% by weight oftthe composition; but incommon practice isused without anyfiller.

Built-up roofings, ifmade of-a sufiicient-num (Ch IMF-282i made haverelatively low'resistan'c'e to spread of flame alongthesurface thereof particularly underthe influence of wind. This poor resistance to spread of flame is due largely to the combustibility of the moppin asphalt. Even when the sheetmaterial is composed of'asbestos felt and even -when the mopping asphalt is used only in layersbeneaththe top layer of felt; the roofing a has'poor resistanceto spread of flame due to the her of plies of sheet material and-particularlytif made up using asbestos felt sheetmaterial for the several plies of the roofing, or if surfaced with properties.

combustible mopping I asphalt and saturant asphaltbleeding out to the surface, and melting and flowing out" from between the plies, thus forming areas which-burn readily and carry the flame-along the suriaceof the roofing. More-- oven-since the mopping asphalt becomes heat liquefied and very thin and non-adhesive upon exposure :of the roofing to flame, any wind is apt to raise up the plies of sheet material, and when this happens the air is taken into thGbOdyOf the roofing the moppingzasphalt is burned rap idlygivand the'entire roofing burns very actively and soon ignites the underlyin roof deck.

The"useofsolvent-thinned asphalt to adhesivelybond the plies of a built-uproofing so that the asphalt may :beapplied as acold composition instead oflina heat liquefied condition, hasbeen very-limited due to the fact that the solvent tends to become entrapped between the plies of the roofingl- It may be added, that whena volatile solventis employed thepresence of the solvent thatis-retained in the finished rooflngaggravates thecomb'ustibility of theroofing. For this reason; the provision of a highly fire resistant cold process built-up v roofing usin a solvent-thinned bituminous composition presents special prob- 181118;

Accordingito this invention, a bituminous composition is provided which is thinned with a volatile solvent for the bitumen in the composition so that the composition can be applied cold, or, if desired in a slightly warmed condition, to adhesively bond-the plies of a bituminous built-up roofing and which, in the finished roofing, not onl-yprovides a good bond between the plies, but also possesses remarkably hish fire resistive propcitiesand imparts a'very high degree ot fire resistiveness to' the built-up roofing as a whole.

In our co-pendingtapplication Ser. No 497,805, filedAugust 7, 1943, for Built-up Roofing and CompositionsTherefor which has resulted in Patent- No.-2,424,234'for Compositions for Built-up Roofing, we have disclosed bituminous compositiens; and built-up i'oofing construction containing-' such'compositions, having.:high fire resistive The bituminous compositions dis- 3 closed in our Patent No. 2,424,234 are of the mopping-asphalt type, namely, adapted for spreading when heated on the job, the bituminous composition being applied hot (usually at a temperature of the order of 350 F. to 425 F.) and the layers of felt being bonded thereto and together while the bituminous composition is still in a heat plasticized condition. As distinguished from our Patent No. 2,424,234, the invention of the present application is concerned with a bi-.

tuminous composition which is suitablefor cold process application, the bitumen being reduced to a fiuid or semi-fluid consistency by the presence of the volatile solvent and the tendency of some of the volatile solvent to remain in the bituminous composition for long periods of time presents special problems which have to be overcome if the composition as used in the built-up roofing is to have high fire resistance. These special problems are due primarily to the effect of the solvent in inducing the running and flowing of the bitumen so as to be in a free burning condition regardless of the infiammabllity or noninfiammability of the volatile solvent. We have found that for cold process application a different formulation of the non-volatile constituents should be employed as compared with mopping asphalt composition disclosed in our Patent No. 2,424,234 as will be apparent from the disclosure of our present invention set forth hereinbelow.

ance with this invention within narrow and critical limits of formulation, and the chief features of our present invention are based upon our discovering that by formulation within the defined limitations of composition a solvent-thinned bituminous composition is provided which can be used in cold-process production of built-up roofings and which in the installed built-up roofing aiforols extraordinarily high resistance to fire.

, In order to facilitate an understanding of this inventiona typical embodiment thereof will first be described for purposes of exemplification. The composition of the example meets all of the requirements mentioned hereinabove, and after .the formulation of the typical embodiment has been described, the critical factors essential to this invention will be explained and defined in detail and applied to the described typical em- The fire resistive bituminous composition;of

this invention results from a combination of a number of factors which are explained and more fully defined hereinbelow. These factors include the amount and softening point of the bitumen that is used, the amounts and kinds of different filler ingredients, the formulation of the composition as a whole, as well as the non-volatile base, within certain limits of consistency. In general the bitumen has a softening point of the range 80 F. to 150 F. and constitutes about 30% to about 55% by weight of the non-volatile constituents, namely, the non-volatile bitumen and filler materials which are referred to hereinafter and in the claims as the non-volatile baseiof. the compositions. The filler material constitutes about to about 70% byweight of the nonvolatile base. The filler comprises what is referred to herein and is defined more in detail below as planar-extended filler. 'Such filler-has special properties which difier quite widely depending upon the particle size, and such properties are defined hereinbelow in terms of the grading index of the planar extended filler. The grading index of the planar-extended filler must, be within certain limits in relation to the per cent. by Weight of the bitumen in the nonvolatile base. Finely particulate filler passing a 100 mesh testing sieve must also be present within certain limits in relation to the per cent. by weight of bitumen in the non-volatile base. The non-volatile base must be within certain limits of consistency as measured by the Wagner- Bowen plasticity value at 400 F. which is defined hereinbelow and likewise the composition bodiment.

In the following example, and elsewhere herein, the percentages given are percentages by weight. One of the ingredients of the composition is asbestos dust. Asbestos dust which passes a 6 mesh standard testing sieve and is retained on an 8 mesh standard testing sieve is indicated for purposes'of brevity as (6+8). Other screen gradings are indicated similarly. The non-volatile base of the composition of the typical example contains the following constituents:

Non-volatile base 1 Per cent Asphalt (130 F. softening point) 40 Asbestos dust gradings Total asbestos dust"; 15 Kaolinitic clay (mostly -200) 45 The non-volatile base above stated is combined witha volatile solvent, the proportions for the purpose of this specific example being 15% by weight (on the composition as a whole) of solvent and 85% by weight of the non-volatile base so that the solvent thinned composition has the following formulation:

4 Per cent Asphalt (130 F. softening point) 34 Asbestos dust 13 Kaolinitic clay 38 Solvent 15 as a whole, including the solvent, must be withij.

in certain limits of Wagner-Bowen plasticity value at 77 F. which is defined hereinbelow. For preferred embodiments, solvents which are capable of affording low viscosity characteristics are employed and which, as a result,-have a speworkable at normal atmospheric temperatures cial effect in reducing fiame spread after the com position is incorporated in a built-up roofing.

It is seen from the foregoing thatthe special fire resistive properties are obtained in accord- -The particular solvent employed in the foregoing example consists of petroleum naphtha having a boiling range between 295 F. and 360 F.

The composition of the formulation above described may be prepared in any suitable way as by thinnin the asphalt with the solvent and incorporating the filler ingredients so that they become thoroughly and uniformly distributed.

The above described composition is easily and can be easily spread at such temperatures by use of a suitable implement so as to bond together the plies of felt material of built-up roofing. In the installation of built-up roofing the i mposition zisisp eadt ou thickness; whereupon. the; wolatilez solvent begins to escape, making. 1,12hfi31s surface tacky and stickyv Class C? ratingaare described briefirc. in 3.01113;

aforesaid Patents N os-.,:=,.2,326,-'Z23,wand: 2.326172%.v which tests are carried outiinrtstingbuilh-un roofings installed in; the .vmanner :aforesaid. Of these ratings gthev Class fCI! rating isgthe:lowest fire-retardant rating and ,servesmto :distinguish rooflngs having: appreciable"fire-retardant pron-1 erties from. roofingschavinglittleazorrno; fire re-; tardant properties suchtas untreated .woodzshina gles; which, of course, are readilyrrignitedxand tend to'burn freely; The Class...A. .:rating is the. highest ratingawarded by Underwriters? Laborae tories, Inc. anduis reserved: forsuchlhighlyfire azlayerrotzidesiredi,

retardant roofings asuasbestos-ycement shingles.

of the double coverage-type; ClassWB, is; an intermediate rating .and. is,. for,-example..;;. awardedto, single coverage asbestos-cementshingles.v So far as we are aware there isrno builteup roofing of the smooth surface, typepther-than that disclosed in our aforesaid Patent-No. 2,424,234 that carries, or is entitled to either the Class-A or Class B rating whether thewpliesot sheet material are composedof asbestos fiber and whether the bituminous waterproofing is applied hot. with: out a volatile solvent or is .thinnedwithavolatile solvent so as to be capable of. cold application. However, built-up roofings ofthe coldprocess type wherein the bitumen is thinned withavolatile solvent have been, prior'to. the. presentinvention, particularlydeficient in fire resistive properties. There are built-up roofingsmhich carry a higher fire retardant rating; whichlhigherrating isachieved by placing over the top ofthe built-up roofing, a very large amount, such as 400 pounds or more per,l00. square feet, of some material such as crushed. rock; or. slag, that pro: tects. the roofings ,from flame,-;but.use, ofrsuch large quantities of crushed ,rock.or.slag.is;undesirable and, frequently as when' an inclined roof deck is to be covered with built-rup roofingbcan not be used at all.

Built-up roofings or the general. construction shown in our aforesaid Patent 1 No. 2,42,234 which have been installed using the specialcold process bituminous composition of this invention that have beendescribed above by way. ofexample will successfullypass all of the, tests prescribed by Underwriters."Laboratories, Inc. for the Class A rating. Moreover, fordifiercnt numbers and arrangements of plies and using possible variations in the formulation ofthe special bituminous composition other built-uproofings within the scope of this invention willsuccessfully pass the Class A? and ClassafB.', fire retardant tests prescribed by Underwriters Laboratories,- Inc. In typicalconstructionof. a built-up roofing using the special bituminous. compositionvof this invention, the composition is applied .at normal temperature as to a layer of roofing ieltalreadyput in place, the volatile solvent is permitted to partially evaporate therefrom causing; the bituminous composition tovbecome tacky and adher .sive, and, while the i bituminous composition.. is

in this: conditions-ano her never; otjt lt isimad adherent thereto, these operations being repeated have .very little effect incounteractingfioweven.

until the a desired. number. of plies haves been installed.

When ordinarily solvent thinned rbituminous compositions are used in the construction of built -up roofings, and. even when. ordinarygmopping asphalt applied in wheat liquefied condition is. used in the construction'of built-up roofing,jthe bituminous material, when'the built-up roofing is subjected: to theme retardant'tests prescribed by Underwriters.Laboratories, Inc., tends to flow outfrom between the plies of felt onto the surface exposed to the flame and burnswithconsiderable vigor. Moreover, the-.wind playing (over the test deck tendsto life up theends-o-f the felt sheets so that the fire gets into the bodyof the roofing ;quite rapidly. Such roofings. are particularly vulnerable to ,the fiame spread test. This is the caseeven though theupper surfaoeof the:- built-up roofing does 'not carry, awate:rproofing layer of the asphalt.

By way of contrast, built-up roofin made with. the special bituminouscomposition of this in-. ventionbehaves very diiferently when exposed to fire. During exposure to the fiame the bitumen and filler in the special bituminous composition remain in place due to the fact that the filler provides a stable skeletal mat in the bitumen, so that the bitumen instead of running out and burning carbonizes and forms with the'filler a protecting mat-like layer that not only is highly resistant to combustion; but also has high'heat insulating effectiveness. Moreover, when amineral filler such as asbestos dust is present that contains: water of constitution liberatable at or adjacent fiame temperature small bubbles form in the residual mat-like mass thatraugm'ent its heat insulating efiectiveness.

Hereinabove it has been pointed out thatthe special bituminous composition of this invention must be formulated within very close limits which are critical to obtaining the desired high fire resistance when. the bituminous composition is incorporated in a built-up roofing and that the desired high fire resistance isdue to a combination of factors. One of these factors is the grading index of the planar-extended fillercomponent of the bituminous composition. The planar-extended filler material is exemplified by fibrousfiller such asasbestos fibers, cotton fibers, etc, and by plate like material such asmica, the particles of which are thin relative to their lateral extent. Such fibrous fillers and platelike fillers are characterized by the fact that at least onedimension is very small relative tolanother more extended dimension, andsuch fibrous and plate-like fillers are referred to generally herein as planar-extended? filler materials thereby indicating that the particles are in the form of fibers or are in the form of plates having anextended dimension that isnconfined essentially to only one ofthe three dimensionalplanes.

The grading index of a planar-extended filler is an index which is indicative of the effectiveness of a particular screen grading or...mixture of screen gradings of planar-extended filler material in promoting flow-resistance of a bituminous composition when. exposed to flame temperature. We have foundthat one of theia'ctors contributing to thefire resistanceof. a .bituminouslayer in. a roofing is that ofbeing resistant to flow when the roofing isexposedtofiame temperature. Fillare as a class have very little effect on such fiow when used in amounts suchas those used in conventional roofings and 'ordinary filler materials when used in relatively large amounts. We'

have found, however, that there is a point where'- at further additions of filler material, even very small additions, result in a very great increase in flow resistance of the bituminous material and that there is a limited zone wherein the bituminous composition, when highly heated, will be stabilized against flowing, even though soft and highly plastic, due to the occurrence of a skeletal mat within the composition which stabi- Iizes the composition and has the further effect of forming with the bitumen a protective heat insulating mat-like mass that carbonizes in situ as a coherent, continuous protective layer that is highly resistant to flame and transmission of heat.

The property of a filler material whereby a bitumen heated to adjacent flame temperature becomes stabilized and resistant to flow is a definite physical property of the filler material that is similar to such properties as solubility, eifect of dissolved salts on boiling point, etc. Moreover, the property is capable of accurate measurement, according to a test procedure which we have devised in order to accurately define the invention which is the result of our research and discoveries. This test procedure enables us to measure the flow resistance of 'a particular filler or filler mixture under conditions of actual exposure to fire. For determining the flow resistance coefficient of a filler contained in the bituminous composition of this invention the bituminous composition is applied in a solvent thinned condition and the solvent is permitted to evaporate until less than 1% by weight of the solvent remains, the test being made on the essentially non-volatile base of the composition. The resulting bituminous layer, as disposed on an inclined test deck, is exposed directly to flame under precisely controlled conditions determined by the construction and operation of the testing apparatus. The test employed is the test for measuring the flow resistance coefficient of a filler which, as regards both apparatus and test procedure, is described in our aforesaid Patent No. 2,42%,234 except that in the preparation of the sample to be tested the solvent-thinned bituminous composition is placed between the piles of the sample by initially applying it in the solvent thinned condition to one or the other of the plies, permitting the solvent to evaporate until the bituminous composition becomes tacky and adhesive, applying the other ply to the tacky surface thereof, and placing the sample in a drying oven at about 170 F. until the solvent has been driven off and less than 1% by weight of the solvent remains. The thickness and weight of the resulting layer should be the same as that mentioned in our Patent No. 2,424,234. as prescribed for the test.

The coefficient of flow resistance is computed according to the following expression:

Weight of total collected bituminous composition X 100 Weight of bituminous ico- composition in exposed area For example, if the weight of the bituminous If none of the coating of bituminous composition flowsinto the pan or onto the exposed portion of ply 13a, then the flow resistance coeflicient is 100, which is the maximum attainable.

The non-volatile base of the bituminous composition of the invention should be such that the filler has a fiow resistance coefficient of or greater, although in preferred embodiments of the present invention the filler has a flow resistant coeiiicient between and 100. The filler employed in the non-volatile base of the example of the present invention that has been described hereinabove, has a flow resistance coefficient of substantially 95. 7

As stated above, We have found that it is essential that the bituminous composition of this invention contains a planar-extended filler material. We have likewise found that the amount of planar-extended filler material that is required depends to a large extent upon the screen analysis of the different screen fractions contained therein, for the different screen fractions are widely different in their effectiveness in imparting flow resistance. This can be illustrated in the case of asbestos dust which is the planarextended filler material that is employed in the above-described typical embodiment of this invention. In the case of chrysotile asbestos dust, we have found that when the screen grading (-28+35) is used and the non-volatile base of the composition contains 6.5% by weight of such specially graded fibers, 53.5% by weight of kaolinitic clay (mostly -200), (total filler 60%) and 40% by weight of asphalt having a softening point of about F., the non-volatile base has a flow resistance coefiicient of about 75. The screen grading (8+10) is considerably more effective since a flow resistance coefiicient of 75 can be achieved when the non-volatile base contains only about .66% by weight of such mineral fiber together with 59.34% of the kaolinitic clay '(total filler 60%) and 40% of the same asphalt.

In other words, using the same total amount of filler consisting of asbestos fiber plus diluent filler that has little flow resistance effectiveness in amounts less than 60% by weight, the coarse fraction (8+10) is much more eifective than the fraction (-28-1-35) in affording a given degree of flow resistance for the non-volatile base. On the other hand, if asbestos fiber (200) is used, it requires about 25% by weight of such fiber to achieve a flow resistance coefficient of about 75'. The efiectiveness of the fibrous filler in the composition just mentioned, and the sur prising effect of only .66% of the (-8+10) fraction, is evidenced by the fact that a non-volatile base consisting of 60% by weight of the same kaolinitic clay and 40% by weight of the same asphalt, has a flow resistance coefficient of only about 33.

In view of the differences in efiectiveness of the different screen gradings of a planar-extended filler, such" as asbestos dust, we have, in order to accurately define the planar-extended filler component of the non-volatile base of the bituminous composition of this invention, assigned to the different screen gradings of planarextended fillers what we have called a screen factor for each of the different gradings. The screen grading of "(-28+35) of chrysotile asbestos fiber has been taken as having a value of unity. Therefore any screen grading that requires only half the amount to achieve the same flow resistance coefiicient as compared with the amount of the grading :-(28j-35) will be twice as aqsinao effective and will have a screen factor of .2. On the other hand, ascreen grading which requires twicethe amount as compared'with'the amount "of the grading (-28+"35) will only have half the effectiveness and will have a screen factor of 0.5. In like manner screen factors can be assigned'to the other screen gradings.

The above-described test for determining the flow resistance coefiicient of a filler 'in the non volatile base of abituminous composition aiiords a each screen "grading togethen'the grading index convenient basis for setting up the screen factors of the screen gradings of the planar-extended fillers on a definite scale, and when the screen "factor of a planar-extended'flller is referred to herein, the screen factor as determined in the following manner, is intended. The test for determining the flow resistance coeflicient is carried out using the test apparatus and procedure abovedescribed. The total filler in all cases is 60% by weight of the non-volatile base and "the asphalt in all cases is an oxidized 'straiight'run asphalt having a softening point of about 135 F. Kao linitic clay, substantially all of which passes a Z'OO-me'sh testing sieve, is used "in all cases as the standard diluent filler, and the amount by weight of a'particu'lar screen grading of p'lanarextended filler to achieve a flow resistance coeflicient of '75, is determined. "Each -sample *is prepared using the materials and construction of the test sample as described hereinabove.

By way of concrete examplefit has been mentionedabovethat chrysotile asbestos *fiber of the screen grading "(-284-35) is taken :as having a screen factor of unity. It being the case that 6.5% by *weight of the non-volatile base of chrystolite asbestos dust of the screen grading (---28+35)the total filler being 60% asafore- -said--istrequired to afford a flow resistance coefiicient ref '75, Land it also being the case that aboutz66-'% by weight of the non-volatilebaseof the screen :grading -(--8+ 1'0), (the total filler being 60%.), :also affords a flow resistance co eflicient of about75,.the screen factor of chryso tile asbestos dust of the'fscreen grading '(8+1!i) is 'seento be about .10. :By way of'further illustration, the fscreen :factors of the different screen gradings of a typical chrysotileasbestos dust on the bases above-mentioned, are as follows:

It is to-be noted thatdnthercase of the .asbestos fiber of the screen grading -(200), .it. .required about .25 .of :the non-volatile base to-achieve 1a flow resistance .coeflicient .of .75 and .that the screen factor .25 .has been (assigned to this particular grading. Similarly, .any .grading of different type .of ..planar-extended filler which requiresmore than-% .by .weightof the monvolatile base .of .the..bituminous. composition to afford a flow resistance c'oe'flicient of about 7:5,.is to be considered as havingga screenfactor of .2.

'The foregoing. affords-"a convenient wayofas-.

of the total asbestos fiber is readily determined. By way of illustration, the grading index of the mineral fibercomponent of the non-volatile base of the above-mentioned typical embodiment of the bituminous-composition of this invention is as follows:

a 4 a y eig creen ra in 50mm Grad-mg of Compo- Factor Index ,sition .or 30 .30 04 10 40 .1 4 -10 3 2. 5 1. 0 1. 5 1. 50 [2. 5 :1 2. 50 2. 0 8 1. 50 1. 25 (ii 75 1. 0 .15 50 1. O '1 40 L3 35 .15 4. 5 i 25 1. 10

.fllotalgrading indexoi asbestos-fiber 10. 65

In determining the screen fractions or gradings of fibrous or other mineralfiller that are referred to herein, 8 inch diameter testing sieves of the W. S. Tyler Company Sieve Series, meeting A. S. T. M. Standard Ell-39 for Sieves for Testing'Purposeshav'e been used. A quantity of filler to be screened ranging from 200 to 3.00 grams is placedin the uppermost of a series of testing sieves and subjected to suitable agitation as in azstandard "W; S.Tyler CompanyRo-Tap sieve sh'akingmachine fora period offive minutes in order to "separate the.origina1 filler roughly into fractions retained in the different testing sieves. "This operationisrepeated if necessary in order to obtain about to 200 grams of the desired screen fraction, which fraction is then individually :re-screenetl for "l5minutes using the Ro-Iap sieve shaking machine or its equivalent in order to remove "any' fines contained therein. The resultingscreenfraction is material that has passed the "coarser. screen and is retained on the finer screen.

--When reference is .made herein to 'screen factor and -g-rading index; the reference is made to those values when determined under "the specific conditions above-specified. -When, however, referenceiis made -to the flow resistance .coefiicient .of the .filler material in the now-volatile base of a bituminous composition, the reference is to the flow resistance coeflicient of the entire filler .content of the composition whatever "the amountmay be and whatever the character of the bitumen, used in-the composition maybe, the non-.volatile base being :tested, :-however, on a sample that ;.is .of the construction and asphaltsaturated felt material, above specified.

The planar-extended. filler. that vispreferred in the .practice of .this ,invention is asbestiform mineral .fiber, ,chrysotile asbestos dust being especially desirable. .O ther asbestiformlmineral fibersof theparticlesize mentioned may likewise beemployefcl, such as Canadian picrolite, .amosite,

, an ophy lit tremnlh and n Another suitable fibrous mineral is a comcertaining thefiow resistance effectiveness ."of a 7; minuted ,lnix ill e vgof lhydrated Portland ecem ent and asbestos fiber, the hydrated Portland cement having become set with the asbestos fiber distributed therethrough. A convenient source of such material is asbestos-cement roofing scrap which usually contains about to by weight of asbestos fiber and about 65% to 80% of hydrated Portland cement. Heretofore such scrap has been regarded as an unavoidable waste of no commercial value. However, by subjecting the scrap to a disintegrator, such as a hammer mill, the resulting mass contains a multiplicity of short asbestos fibers to which the hydrated Portland cement adheres as nodules and for this reason this material is fibrous and is to be included in the term fibrous mineral.

Another material which is somewhat simi ar to asbestos-cement in that the material contains mineral fibers together with some non-fibrous material, is disinte rated fiber-bearing serpentine rock. Since disint grated fiber-bearing serpentine rock contains fibrous particles, such disintegrated serpentine rock is regarded as one form of fibrous mineral which is suitable for use in practicing this invention. Howe er, depending upon the physical structure and fibrous mineral content of the particular serpentine rock that is used, the pro ortion of fiber contained therein is sub ect'to some variation. but, as pointed out be ow, this merely has the effect of varying somewhat the screen factors of the various screen gradin s of the disinte rated serpentine rock as c alculated to chrysot le asbestos dust of the scr en grading 28+35) whichhas a screen factor of unity. 'Moreover, disintegrated fib rbearin ser entine rock is of such character that in order to liberate the fibrous material contained therein. it should pass a 20-mesh testin sieve, and. when reference is made herein to disintegrated fiber-bearing ser entine rock. onlv that s r entine rock which has been disintegrated so that it asses a 20- mesh testing sieve is intended, since individual articles of coarser radings are not fibrous in character but granu ar (are not fibrous mineral as this term is used herein) and since such coarser gradin s are ineffective in pro ucing highly fire-resistant roofings.

While fibrous mineral fillers selected from the group consistin of asbestiform mineral fibers, disintegrated asbestos-cement and disintegra ed fiber-bearin serpentine rock are preferred, other mineral fibers mav likewise be em loyed, such as mineral wool and glass fibers. The'term "mineral wool inclu es various roducts obtained by attenuating into fibrous form suitable fused materials. such as rock or slag. In addition to fibrous minerals, other fibrous fil ers may be emplo ed as the planar-e tend d filler component of the bituminous com osition of this invention although the mineral fibers are preferable for use in the ractice'of this invention and it is desirable that a major proportion by wei ht of the planar-extended filler consist of asbestiform mineral fibers. Thus, any of a wide selection of animal, vegetable and synthetic fibers may be used. Cotton is suitable and, in the very shortgrades is inexpensive and, in fact, has little commercial value.

In addition to cotton, one may employ wood fibers. such as fine sawdust, or defibrated wood and aper and paner fibers, such as round wood. sulphite, and kraft paper pulps. Finely divided wool fiber is also suitable but is much more costly. Synthetic fibers. such as regenerated ce lulose (rayon) and cellulose acetate also may be used.

In addition to fibrous fillers, another filler that is similar to fibrous fillers in that it is effective in varying degrees depending upon the screen grading ormixture of screen gradings that is employed, is mica. Mica is characterized by its occurrence in the form of small plates which are thin relative to their lateral extent. Mica and fibrous materials are characterized by the fact that at least one dimension is very small relative to another more extended dimension, and, as stated above, are referred to herein under the generic term planar-extended filler material. In the case of the filler, such as mica that exists in the form of thin plates, particles which are retained on a l l-mesh testing sieve are undesirable in the composition. With regard to fibrous fillers other than asbestiform mineral fibers, it is not usually the case that a particular screen grading of, for example, asbestos-cement, cotton, wood fiber, etc, will have the same screen factor as that of chrysotile asbestos fiber.- In fact, even as many different types of asbestiform mineral fiber there are some variations in this regard. However, utilizing chrysotile asbestos dust as the standard, chrysotile asbestos dust of the screen grading (-28+35)' having a value of unity, the screen factor of the screen grading of other fibrous fillers is determinable in the same way that the screen factor of the different screen gradings of chrysotile asbestos fiber is determinable as has been described hereinabove. However, fibrous fillers, particularly in the case of wood fibers, cotton and the like, are subject to considerable variation, and for this reason the screen factor and grading index has been calculated to chrysotile asbestos fiber, which is more uniform in its physical characteristics, as the standard; The foregoing, with respect to the screen factors of other fibrous fillers, also applies to planar-extended fillers of the plate type. For example, the screen factor of mica of the screen grading (-28+35) is about 0.9; 'The foregoing also applies to the screen factors of mixtures of planarextended fillers, calculated to chrysotile asbestos dust of the screen grading (-28+35) as the standard.

In ascertaining the grading index of a filler of the planar-extended. type for use in a bituminous composition for cold process application in the construction of built-up roofing, the grading index required will vary with the amount of bitumen in the bituminous composition, the amount of bitumen being, of course, an inverse function ofthe total filler. When the amount of waterproofing bitumen in the non-volatile base of the composition is about 30% by weight, the grading in-. dex of the planar extended filler is desirably at least about 4, while for a total bitumen content of the non-volatile base of about 55% by weight,

the grading index for obtaining similar stabilization of the bitumen will be at least about 8. For bitumen contents of the non-volatile base ranging from 30% by weight to 55% by weight, the minimum required grading index: varies proportionally from about 4 to about 8 respectively, More generally, in the practice of this invention,

it is desirable to employ filler of the planar-ex tended particle type having a grading index the ratio of which to the percent by weight of waterproofing bitumen in the non-volatile base is at leastabout 1 to 8, and preferably is at least about When a filler of thefplanar-extended type is used, such filler should'be used in the finely-di yideddust-lilge formas distinguished from long 13 cotton, wood, or asbestos fibers. Fibrous fillers that are retained one 6 mesh testingsieveareundesirable in the coating composition. It has been mentioned above that mica retained on a 14 mesh testing sieve is undesirable. Accordingly, and somewhat more generally, it is desirable that the filler materialof the planar-extended typ be confined to that which passes a 6 mesh testing sieve and which does not have more than one di mension greater than about .046 inch, which is the width of the opening in a 1ft mesh testing sieve. When-a filler of the planar-extended type is used that is coarser than has been mentioned above, such filler material tends to form into clumps or clots which render the solvent-thinned bituminous composition unspreadablewith desired uniformity and also impairs the fire resistance of the applied coating dueto occurrence of zones of insufficient protection and due to uneven andpoor adhesion to the plies of felt or the like contained in the built-up roofing. For this reason, it is highly desirable to limit the quantity of coarser planar-extended filler to that which can be incorporated in a bituminous composition that, when thinned witha volatile solvent to the usually desirable that'less than 10% by weight of the total non-volatile base of the bituminous composition consist of a filler of the planar=extended type which isretained on a 14 mesh testing sieve, although in-the case of mineral wool a sub- *stantially" greater proportion'of such coarse material can be incorporated in a spreadable composition. While the presence of any fiber retained on a 6 mesh testing sieve isregarded asundesir- "able and while thepresence-of any mica retained on a l l mesh testing sieve is regardedas undesirable, any small quantity of such excessively coarse planar-extended fillerthat may be present while still retaining spreadability is to be regarded as havingascreen factor of 40. Usually it is desirable that the ratio of grading index of the filler of the planar extended type to the per cent. by weight of the bitumen in the composition to be less than about 1 to1.7, and preferably'less than about i to 2.5; so as to avoid the inclusion of'an excessive quantity of the 'coarser screen fractions.

As stated hereinabove, the total filler contained in the non-volatile base of bituminous composi "tion of thisinvention is of the order of to 70% by weight of the non-volatile base. Preferabl'y, the filler constitutes from to 65 by weight of the non-volatile base. While the filler may consist entirely of filler particles of the planar-extended type, provided such filler is used within the aforesaid limits of grading index in relation to the bitumen content of the non-volatile base, it is preferable, and constitutes normal practice of this invention, to include a diluent filler that is not of the planar-extended type. In addition to kaolinitic clay, there are a number of other heat-resistant mineral fillers which may be employed, e. -g slate 'fiour, limestone dusnjsilica flour, other clays, talc, fly ash, hydrate'd'Portland "cement, dead burned calciumsulphate, and precipitated calcium silicate hydrate. Most fillers of 14 this character are of such state of subdivision that about% by-weight thereof will pass a .100 mesh testing sieve.

In addition tomineral fillers, organic lillermateri'als may be employed, although it is usually advantageous to employ a heat-resistant mineral in an amount such that the ratio of the per cent. by weight of heat-resistant mineral filler in the non-volatile base of the bituminous composition to the per cent. by weight of waterproofing bitumen in the bituminous composition is at least 1 to 3 and even more desirably at least 1 to 2. By heat-resistant, any material that retains. structural integrity when a bituminous composition containing it is exposed to flame temperatures is intended and any material such as chrysotile asbestos, kaolin clay, hydrated Portland cement or the like that contains water of constitution liberatable at or below flame temperature is regarded as heat-resistant. The foregoing respecting the proportion of heat-resistant mineral filler in the non-volatile base applies to the total filler including the planar-extended type filler and any di1uent filler used in conjunction therewith.

.Among the organic fillers, examples of "such fillers of the planar-extended type have been given hereinabove. Examples of non-planarextended organic filler materials which may be employed are finely-divided cork, coal, coke, ground hard rubber, ground synthetic resins such as phenol-aldehyde resins) pyrobitumens, and the like. 1

li'li'ore generally, any'linely-divided solid waterinsoluble filler or filler mixture may be employed provided'the filler material has a softening point "above about 500 F. and preferably above about Til in determining the'softeninlg point of the filler 'material, the standard cube-in-air softening point test isreferred to.

In formulating the bituminous composition of this invention, we have found it essential that the filler include particles which are .suiilciently finely-divided to pass a mesh testing sieve. The particles passing a 100 mesh testing sieve may be any of the constituent particles passing a 100 mesh testing" sieve that are contained in the bituminous composition, namely, may be either of the planar-extended type, or diluent filler not of the planar-extended type, or a mixture of both. We have found that for total filler contents of the non-volatile base ranging from 45 to 70 by weight, the filler particles passing a 100 mesh testing sieve should vary from at least'about'20 to at" least about-40% by weight, and preferably from at'least-about 30'%--'to at least about-50% by weight, proportionally. "The presence of such finely-divided filler assists in preventing migration of the bitumen upon 'exposure of the bituminous composition to flame temperature and reduces combustibility and flame spread. Such finely-divided filler also improves the application consistency of the bituminous composition when in solvent-thinned condition suitable for cold process application.

For the preferredrange of total filler content,

namely, 55% to 65% by weight of the nonvolatile base, the filler particles passing a 100 mesh testing sieve should vary from at least about 28% to at least about 35%, and preferably from at leastv about 35% to at leastabout 45% by weight, proportionally.

The presence. of. excessively coarse planarnon-planareextended filler is also undesirable.

. 15 For this reason, it is desirable that the amount of non-planar-extended filler retained on a 14 mesh testing sieve constitute less than by weight of the non-volatile baseof the bituminous composition.

Of the fillers other than planar-extendedtype filler, we prefer to employ kaolinitic type clay, since we have found that the special bituminous compositions of this invention that contain kaolinitic type clay are particularly effective in preventing the separation of the plies of built-up roofing when the roofing is exposed to flame temperature. It is desirable, therefore, that the non-volatile base of the special bituminous composition of this invention contain at least 15% and preferably at least 25% by weight of kaolinitic clay.

Of the filler materials above-mentioned, chrysotile asbestos fiber and Canadian picrolite usually contain about 12% to 15% of water of constitution liberatable at temperatures ap proaching flame temperature. Other asbestiform mineral fibers are low in water of constitution. Some of the non-fibrous'flller materials contain Water of constitution that is liberatable at or adjacent flame temperature. Thus kaolinitic type clays, powdered serpentine rock, calcium silicate hydrate and hydrated Portland cement contain or more of water of constitution that is liberatable at or below flame temperatures. When the filler material contains water of constitution liberatable at or below flame temperature, the liberation of moisture causes the bituminous composition as disposed in a built-up roofing to develop pores to a greater extent than otherwise when the bituminous composition is exposed to flame temperature and this is desirable since the pores tend to augment the heat insulating efiiciency of the matlike residue that is formed upon exposure of the bituminous composition to flame temperature. It is desirable that the bituminous composition of this invention have'incorporated therein a filler material containing water of constitution, which water of constitution is liberatable at or below flame temperature, that amounts to at leas about 5% by weigh of the non-volatile base of the bituminous composition.

In order that there may be a proper overall proportioning of any particular filler or filler mixture to the bitumen, we have found that it is also essential that the non-volatile base of the bituminous composition be formulated within certain limits of plasticity value which has been determined by us, using a Wagner-Bowen mixing bowl plasticimeter, manufactured by E. E. W. Bowen, Bethesda, Maryland, in the modified form illustrated and described in our aforesaid Patent In the formulation of the bituminous composition of this inventionthe 'Wagner-Bowen plasticity value at 400 F. of the non-volatile base of the bituminous composition should be greater than 250 grams but should be less than 1000 grams.

the above described specific examplepf the invention is about 315 grams. The foregoing Wagner-Bowen plasticityvalues are determined using the Wagner-Bowen plasticimeter and the test procedure with reference thereto that are fully disclosed in our aforesaid Patent No. 2,424;-

234 and reference herein or in'the claims to the 16 Wagner-Bowen plasticity value at 400 F. of the non-volatile base of the bituminous composition of this invention is to such pasticity value as .so determined.

It is also important that the bituminous composition as formulated in solvent-thinned condition for cold process application in the construction of built-up roofings be formulated within predetermined limits of Wagner-Bowen plasticity value at 77 F. The Wagner-Bowen plasticimeter that is used for making this determination is identical with that referred to hereinabove and described and illustrated in our aforesaid Patent No. 2,424,234 except that a diiferent type of drag tool is employed. Thus instead of using the drag tool shown in Figs. 19 and 20 and in detail in Figs. 21A and 21B of the drawing of our said patent, the drag tool used is in the form of a simple 'rod inch in diameter which extends horizontally from the collar I28 fixed to the vertical shaft I21 and which has a shorter end portion bent downwardly so as to be to the horizontal portion for penetratin below the surface of the bituminous material in the mixing bowl of the plasticimeter. The foregoing reference characters are those appearing in the drawing of our Patent No. 2,424,234 and the direction of the emanation of the horizontal portion of the rod from the shaft 121 is the same as that of the rod I46 comprised in the drag tool shown in Patent No. 2,424,234. The length of the horizontal portion of the rod measured from the axis of the shaft I21 to the axis of the turned down end portion of the rod is 4 /8 inches. The distance from the axis of the horizontal portion of the rod to the tip of the turned down end portion is 13% inches. The distance between the tip of the turned down end portion of the rod and the upper surface of the bottom of the bowl of the plasticimeter is inch. The turned down end portion of the rod is directed downwardly at an angle of 33 to the vertical in the clockwise direction as regards rotation of the bowl of the plasticimeter about its axis. In carrying' out the test for determining the Wagner- Bowen plasticity value at 77 the depth of the composition in the mixing bowl as it passes the drag tool is one inch, and the lower end of the measuring rod which acts as an indicator respectin the proper depth of the composition in the bowl as shown in our Patent No. 2,424,234 is ad- J'usted so as to be one inch from the bottom of the bowl; Except for the difference in the natureof the drag tool and for the difference in the depth of the composition in the plasticimeter bowl as it passes the drag tool and for the difference in the temperature maintained in the test, the measurement of the Wagner-Bowen plasticity value at 77 F. of a solvent-thinned composition is as described and illustrated in our Patent No. 2,424,234 and reference herein or in the claims to such value is to such value as so determined with the changes described. In formulating the bituminous composition in solvent-thinned condition we have found that the Wagner-Bowen plasticity value at 77 F. should be between 15 and grams and preferably is between 25 and 75 grams. The Wagner-Bowen plasticity value at 77 F. of the solvent-thinned composition of the above described example of this invention is about 52 grams.

With regard to the bitumen that is employed, it has been pointed out above that the softening point of the bitumen may be between 80 F. and F. and that the per cent. by weight thereof on the non-volatile base may be between 30% 17 and 55%. However, in

bitumen used'has a r e re a t et e softening point between 115 F. and 135 F. and constitutes from about 35% to about 45% by weight ofthe non volatile base of the bituminous composition. The softening points referred to are determinedby-the standard ring and ball softening point test. Asphalts from Mid-Continent crudes are desirable although other asphalts are suitable, such as those'obtained from Mexican, Venezuelan, andColom-bian crudes. Moreover, other bitumens, such as pitches, coal tar and the like may also beused in the practice of this invention. We-have found that the now resistance coefficient of a "given amount of filler is usually somewhat higher inthe case of a cracked asphaltas compared with other types of asphalt, andfor'thisreason may be' advantageously employed especially ln's'ubs'tra e! a built-up roofing where there is-to "belittle-direct When, however, the

exposure to the weather. special bituminous composition of this invention is to be used for direct exposure to the weather, it is usually preferably to employ some bituminous or asphaltic material other than cracked asphalt as all, or as the major proportion of, the bitumen content of the non-volatile base of the special bituminous composition.

When reference is made herein to "bitumen," this term is used in reference to asphalt, pitch, tar or the like by itselfand unmixed with'filler; When, on the other hand, referenceis madeherein to bituminous composition or a bituminous ma.- terial Or a bituminous layer, reference "is made to a composition, material or layer comprising bitumen either with or without filler. Any modifier, e. g., of a resinous or oily character that may be mixed with the bitumen'is to be regarded as part of the bitumen content of the compositionl The bituminous composition as made up for cold process built-up roofing has, of course, a solvent for the bitumen in the composition so that the solvent that is present, by dissolving the bitumen, will reduce the bituminous composition to the desired condition of workability and spreada bility. The solvent that is employed shouldlikewise be of such volatility that after the solventthinned composition of this invention hasbeen applied as a layer, the solvent will evaporate therefrom within a reasonable time and cause the layer of bituminous composition to set up because of loss of solvent therefrom. By volatile solvent, as this term is used herein and in the claims, the referenceis to a solvent which is adapted to dissolve the bitumen in the bituminous composition and which, m a bituminous composition such as that hereinabove described as a typical example of the practice of this invention, exhibits fugacity of the order of, or greater than, carbon tetrachloride. In the case of inflammable solvents, it is ordinarily desirable that the solvent not have a flash point below about 80 F.

Any of the solvents for bitumen may be employed, examples bein petroleum fractions of suitable volatility and flash point, those supplied in the naphtha class being preferable.

Turpentine is also suitable.

In addition to the foregoing non-inflammable solvents, solvents such as carbon tetrachloride and tetrachlorethylene may be used. With regard to the employment of non-inflammableisolvents, we have found as a result of ourfresearch that use of non-inflammable solvents contributes only slightly to the fire resistive properties applicationin the construction of 18 of the s pecial'bltuminous composition of this invention'.

While any volatile solvent for the bitumen in the bituminous composition may be employed in the practice of this invention, we have found that the fire resistive properties of the composition are very markedly improved by employment of a solvent having a high solvent power for the bitumen in the bituminous composition, namely, one which reduces the solvent-thinned composition to within the limits of Wagner-Bowen plasticityvalue at 77 F. that have been set forth above (15 to 125 grams) when employed in rela tively small proportion in the bituminous compcsition. 'Qrdinarily it preferable to employ a solvent which reduces the bituminous composition to within theaforesaid limits of Wagnerwen plasticity value at 77 F, when the solvent constitutes 35% or lesser the bituminous composition, and for obtaiiung optimum results the solvent constitutes not morethan 20% by weight of the bituminous composition. In ordinary practice we have found that the best results from the point of view of fire resistance are obtained when the solvent is present within the aforesaid limits while maintaining the Wagner-Bowen plasticity value at 77 F. within the preferred limits above stated for the'value, namely, 25 to grams. 'It is also desirable to employ in preferred embodiments a solventof high fugacity, namely. a solvent which, in a bituminous composition suoh as that of the above described typical example of the practice of this invention, exhibits a fugaoity of the order of, or greater than, petroleum naphtha of the boiling range 300 F. to 400 F., and any such solventis referred to herein and in the claims as a highly fugitive solvent for the bitumen.

The foregoing regarding the f-ugacity and solvent power ofthe solvent is of importance in attaining high fire resistive properties when the bituminous composition is employed as a substratum' in the body of a built-up roofing (namely, under an overlying layer of felt or the like), since we have found that the fire resistive n ss r the roofing is adversely aifected by the retention of volatile solvent, whether the solvent is inflammable or non-inflammable, due to the'tendency of retained solvent to induce flow of bitumen which in turn induces flammability and c'ombustibility' In the construction of builtup roofing by cold process application of bituminous composition, sheet material that overlies a layer of the special bituminous composition is necessarily put in place while the layer of bituminous composition is still somewhat tacky and adhesive due to presence of some retained solvent. This retained solvent thereafter becomes entrapped and many months may elapse before the amount of retained solvent becomes materially reduced as a result of gradual per meation to and escape from an outer surface of the roofing. We have found that the retention of solvent in built-up roofing made from solvent-thinned bituminous composition constitutes the chief reason why this type of built-up roofing has presented a particularly great fire hazzard and why the problem of affording high fire resistance in the case of this type of built-up roofing is especially difiicult. The problem of attainingpigh fire resistance in connection with this type of built-up IOOfillg has been largely attained by'the special formulation of the nonvolatile base of the bituminous composition. However, it is important in attaining very high 193isi640 fire resistance according to this invention that the solvent used be of the type and amount hereinabove defined.

While the composition of this invention is ordinarily made up so as to be suitable for application at ordinary atmospheric temperatures, it is not without the scope of this invention to subject the composition to mild heating, e. g., in cold weather, to increase the fluidity of the composition for application and such mild heating is not inconsistent with cold-process application as distinguished fromthe hot application of ordinary mopping asphalt at temperatures of the order of 300 F.t 350 F. It is apparent that compositions other than the specificexample hereinabove given of a typical embodiment of this invention will meet the. requirements of the definition hereinabove stated for those bituminous compositions which are adapted for cold process production of built-up roofings having high fire resistance although the narrowness and criticality of the limitations imposed by the definition of this invention confine the possible variations within close limits of formulation.

While reference has been made hereinabove to the employment of felt consisting of organic fibers or asbestos fibers, and to the impregnation of felt with a bituminous waterproofing material, it is apparent that any other sheet-like strainresisting material can be employed in the fabrication of built-up roofings employing the special fire resistant bituminous composition of this invention. Thus sheets of woven fabric such as canvas or duck may be employed, or sheets of unspun fibrous material and generally any type of fibrous sheet-like base material, either foraminous or non-foraminous, and impregnated or unimpregnated, may be employed. Moreover,

the impregnating material for the fibrous sheet may be bituminous or some other type of hinder .or waterproofing material.

The bituminous composition of this invention may be used for other purposes than the construction of built-up roofing and is suitable generally as a cementing composition for applica' tion to surfaces and for binding plies of sheet material together with a waterproofing bituminous layer. While the composition as applied contains the volatile solvent, the volatile solvent gradually evaporates during and after application. The non-volatile constituents of the composition of this invention afford the high fire resistive properties that have been referred to hereinabove after the volatile solvent has been evaporated and this invention relates both to the cementing composition in its solvent thinned condition and to the cementing composition in" its wholly or partially dried condition as characterized by the formulaton of the non-volatile constituents.

While this invention has been described in conbase ofthe bituminous composition, and a volatile solvent. for the bitumen in said non-volatile base, said non-volatile base comprising about 35% to about by weight of bitumen having a softening point of the range 115 F. to 135 F. and about to about by weight of finelydivided solid water-insoluble filler having a melting point above 500 F., said filler comprising planar-extended filler consisting of particles which pass a 6 mesh testing sieve and which do not have more than one dimension greater than .046 inch and the grading index of which has a ratio to the. percent; by weight of the bitumen in said non-volatile base of at least 1 to 5, the ratio of the grading index of said planarextended filler to the percentby weight of the bitumen in said non-volatile base being not greater th'an about 1 to 2.5, said finely-divided solid water-insoluble filler comprising material passing a 100 mesh testing sieve'which is any constituent particles passing a 100 mesh testing sieve comprised in the total filler and which constitutes in said non-volatile base'at least about 35% to at least about 45% by weight of said non-volatile base proportionally for total filler contents ranging from 55% to 65% by weight of said non-volatile base, said filler comprising heat-resistant mineral filler the ratio of the percent by weight of which in said nonvolatile base to the percent by weight of bitumen in said non-volatile base is at least 1 to 2, said non-volatile base having a Wagner-Bowen plasticity value at 400 F. greater than 275 grams and less than'700 grams, said volatile solvent constituting notgreater than 20% by weight of said bituminous composition and having iungacity in said'composition at least as great as carbon tetrachloride, and said bituminous composition as thinned by said solvent having a Wagner-Bowen plasticity value at 77 F. between 25 and grams.

2. A solvent-thinned bituminous cementing composition according to claim 1 wherein said volatile solvent is a highly fugitive solvent.

3. A solvent-thinned bituminous cementing composition according to claim 1 wherein said planar-extended mineral filler consists in major proportion by weight of asbestiform mineral fibers.

GEORGE ARTHUR FASOLD. HAROLD W. GREIDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number OTHER REFERENCES v Petroleum Zeitschrift, 1933, vol. 29, No. 45, pp. 1-12; Rosenberg: Micro-asbestos in the Asphalt Industry andRoad Construction.

Claims

1. A SOLVENT-THINNED BITUMINOUS CEMENTING COMPOSITION ADAPTED FOR APPLICATION TO PROVIDE A WATERPROOFING LAYER IN THE CONSTRUCTION OF BUILTUP ROOFING WHICH CONSISTS ESSENTIALLY OF NON-VOLATILE CONSTITUENTS CONSTITUTING THE NON-VOLATILE BASE OF THE BITUMINOUS COMPOSITION, AND A VOLATILE SOLVENT FOR THE BITUMEN IN SAID NON-VOLATILE BASE, SAID NON-VOLATILE BASE COMPRISING ABOUT 35% TO ABOUT 45% BY WEIGHT OF BITUMEN HAVING A SOFTENING POINT OF THE RANGE 115* F. TO 135* F. AND ABOUT 55% TO ABOUT 65% BY WEIGHT OF FINELYDIVIDED SOLID WATER-INSOLUBLE FILLER HAVING A MELTING POINT ABOVE 500* F., SAID FILLER COMPRISING PLANAR-EXTENDED FILLER CONSISTING OF PARTICLES WHICH PASS A 6 MESH TESTING SIEVE AND WHICH DO NOT HAVE MORE THAN ONE DIMENSION GREATER THAN .046 INCH AND THE GRADING INDEX OF WHICH HAS A RATIO TO THE PERCENT BY WEIGHT OF THE BITUMEN IN SAID NON-VOLATILE BASE OF AT LEAST 1 TO 5, THE RATIO OF THE GRADING INDEX OF SAID PLANAREXTENDED FILLER TO THE PERCENT BY WEIGHT OF THE BITUMEN IN SAID NON-VOLATILE BASE BEING NOT GREATER THAN ABOUT 1 TO 2.5, SAID FINELY-DIVIDED SOLID WATER-INSOLUBLE FILLER COMPRISING MATERIAL PASSING A 100-MESH TESTING SIEVE WHICH IS ANY CONSTITUENT PARTICLES PASSING A 100-MESH TESTING SIEVE COMPRISED IN THE TOTAL FILLER AND WHICH CONSTITUTES IN SAID NON-VOLATILE BASE AT LEAST ABOUT 35% TO AT LEAST ABOUT 45% BY WEIGHT OF SAID NON-VOLATILE BASE PROPORTIONALLY FOR TOTAL FILLER CONTENTS RANGING FROM 55% TO 65% BY WEIGHT OF SAID NON-VOLATILE BASE, SAID FILLER COMPRISING HEAT-RESISTANT MINERAL FILLER THE RATIO OF THE PERCENT BY WEIGHT OF WHICH IN SAID NONVOLATILE BASE TO THE PERCENT BY WEIGHT OF BITUMEN IN SAID NON-VOLATILE BASE IS AT LEAST 1 TO 2, SAID NON-VOLATILE BASE HAVING A WAGNER-BOWEN PLASTICITY VALUE AT 400* F. GREATER THAN 275 GRAMS AND LESS THAN 700 GRAMS, SAID VOLATILE SOLVENT CONSTITUTING NOT GREATER THAN 20% BY WEIGHT OF SAID BITUMINOUS COMPOSITION AND HAVING FUNGACITY IN SAID COMPOSITION AT LEAST AS GREAT AS CARBON TETRACHLORIDE, AND SAID BITUMINOUS COUMPOSITION AS THINNED BY SAID SOLVENT HAVING A WAGNER-BOWEN PLASTICITY VALUE AT 77* F. BETWEEN 25 AND 75 GRAMS.