US 2610928 A
Description (OCR text may contain errors)
Sept. 16, 1952 w. GRElDl-:R l-:rAL 2,610,928
MINERALIZED BITUMINOUS ROOFING Filed Aug. 7, 1945 5 Sheets-Sheet l hay@ uw A TORNEY5 H. W. GREIDER ET AL MINERALIZED BITUMINOUS ROOFING sept. 16, 1952 5 Sheets-Sheet 2 Filed Aug. 7, 1945 NlUNHIUIWIIIIIPIII iiii Sept. 16, 1952 H. w. GREIDER ETAI.
MINERALIZED BITUMINOUS RooFING 5 Sheets-Sheet 3 Filed Aug. '7, 1943 INVENTORS Sept. 16, 1952 H. w. GREIDER ETAL MINERALIZED BITUMINOUS ROOFING 5 Sheets-Sheet 4 Filed Aug. 7, 1945 H. W. GREIDER ETAL MINERALIZED BITUMINOUS ROOFING Sept. 16, 1952 Filed Aug. '7, 1943 5 Sheets-Sheet, 5
ATTORNEYS ytofore have relatively rlow lire-resistance.
Patented Sept. 16, 1952 MINERALIZED 2,610,928 Y BITUMINoUs RooFIrsicf Harold W. Greider, Wyoming, and George Arthur'n Fasold, Mount Healthy, Ohio, assignors to The Philip Carey Manufacturing Company, a core.
poration ,of Ohio Application August 7, 194s,`seria1N. 497,809 i; Y
This invention nrelates to roofing. trelates f soumis. (C1. 11i-716s); v
particularly;k to roofing embodyingy bituminous material as waterproong. i, .Y
Heretofore bituminous prepared rooting has been ,very extensively manufactured using as a basea brous' web such as roong..felt,.impreg nating the iibrousweb with a' bituminous material, and coating the impregnated web with a weather-resistant bituminous coating composition. g `The bituminouscoating composition usualtype. Class B is an intermediate .rating and is, for example, awarded to rooflngs such as singlecoverage asbestos-cement shingles. A brief description of the Class ACla ss B and Class,A C Kflreretardant tests of Underwriters Laboratories )is contained in ourpending applications for Roofing, ser. No. 370,636,1fi1ed December 18, 1940 (Patent No. 2,326,723), and ser. No.'399,o24,-f11edJune-20y ly contains a mineral llersuch as slate our or powdered limestone in amounts less'than about 40%' by weight ofthe bituminouscoating ccmposition. Usually there is applied to the bituminous `coating on the surface intended to be l exposed to the weather a suitable granular materialsuch as slate granules or more inely divided mineral surfacing material such ras talc or mica. Finely divided materials such as mica akes, talc, silica dust or the like Amay be made adherent to the non-Weather exposed surface of the roofing to prevent sticking of adjacent layers of the rooiing material in the package.
The term "rooiing is used herein in the broad sensei as'referring to watervand weather-resistant coverings'such as shingles (individual vor strip shingles), roofing tiles, cap Sheetssidings, roof deck coverings made Vfromv such preformed materials, built-up roofings, and the like.
The bituminous rooiin-gs of the character` aforesaid that have been manufactured and sold here- The most widely-accepted 'tests for determiningthe rire-resistant properties of roong are those prescribed by Underwriters Laboratories, Inc., of Chicago, Illinois. According to the tests prescribed by Underwriters Laboratories, Inc., fire retardant rooflngs are placed in three classifications, depending upon their ability to pass the tests required for each classiiication, these classications being Class A, Class B and ClassC. The .Class C rating is the i lowest fire-retardant rating and serves to distinguish roolngsjhaving appreciable fire-retardant properties `from rooi-` ings having little or no'iire-retardant properties suchas untreated wood shingles which. of course, are readily ignited and tend to'burn freely. So
far as we are aware, prepared bituminous rooiings of the type heretofore onthejmarket made on an organic liber feltbase have not been able to attain, regardless of the thickness thereof or the number ofl thicknesses, a rating of UnderwritersV Laboratories,v Inc. higher than a `Class C rating.
The Class Arating is the highest rating awardedV l asbestos-cement shinglesgci theLdouble--coverage 194,1 (Patent No. 2,326,724),...-,-
y It is apurpose of this invention .to improvethe fire resistance ,of Vroofings .comprising avlayer of thermoplasticmaterial such asbituminous material. Thus, for;example, we have. found that a roofing material which comprises an organic ber felt base anda bituminous waterprooflngcoating can be made according to. thisI invention, yat .the cost of ordinary-bituminous rooiing material, that is` so highlyl,nre-,retardant that a: three-layer covering lon a combustible. .roof declewill satis.- factorily withstand exposurelto'the .Class Aiireretardant tests -prescribedby Underwriters 'Laboratories, Inc. We have found further that 'such rooting materialem-bodying our invention, when appliedso as toprovide; two-layers, will satis factcrly pass the Class B :lire-retardant tests prescribed by UnderwritersLaboratories, Inc'.
The-.importance of nre-resistant properties for rooiing'is self-"evidente Certainrooiings such as asbestosfcement shingles, 'tile and the like have high .re resistance `but such roongs are very costly as compared with asphalt vfeltrooiings, and for this reason asphalt-felt rooiings are very extensively used on all kindsof structures notwithstanding the limited fire-protection that is aiorded by this type of 'rooiing'. Acccrdinglto, this invention, asphalt-felt roongs can be made without' substantial increase Yi'ncostwhich are comparable in rire-retardant properties torelativelyV much more costly roofingconstructions such as asbestos-cement, tile and the like. j' c `Subs'tar'itially all bituminous r'oongs comprise l a strain-resisting baseer Afoundationv sheetV such as rooiing felt which is coatedwith abituminous In our aforesaid depending application, Ser. No.
` i' raciones 370,636 (Patent No. 2,326,723), we have described and claimed bituminous roofing comprising a bituminous waterproofing composition that, while highly fire resistant, possesses physical properties such as"'pliability and resistance'to iiexure that correspond in a general way with bituminousv roongs of similar character previously manufac-` tured and sold. The bituminous coating composition of the roofing disclosed andclaimed incur application Ser. No. 370,636 contains bitumen having a softening point above-Iv l1430?E.' anciffai the range 45% to '70% by Weight?Ofthcobathn' composition. 'I'he coating compositionV also contains iiller material of the range 30% to 55% by Weight of the coating composition 'andintlie form of finely divided solid water-insoluble heat- 4 resistant mineral material of special characterY that is described, illustrated n i y and ldeiine'd in our application! Ser. No; 370.6363v The present mention' has to# downs-roofingcomprising more highlywmineralizdj bituminous waterproofing coatings than those described and claimed 'in our aforesaidapplcation'- Ser; No2
37 0,6361 namelyf coatingfcompositious containing more Vthan' 55%- by4 Weight' otnelyfldivided `solidl water-insoluble heat resistafrit- 'mineral ii'ller,"
Such roongs at ordinary` tempeatu'resae somewhatrstiffer and lesspliable than the r'o'oing4 disclosed inl our-.application Sei'. .No.37 0,636 andere especially suitable: for` certaintypes -of roofing wheretoughness andi resistance', to exure' are desirable" and a1 high degree of pliabilityfl is not essential.v Y Forl example, theoong off the present invention is? desirabl as a tveather-v andi iire'- resistant surfacelyer otrbuilt-u'ph'.ooimg.v Ordi.- nary' builtL-up f roongr' especially when laid over iibrous or cellular' heatfinsulationfmaterial', j is indented; qutea readilyfra'nd is 1'subject-V t'o injury-4 due'; to peopiepwall-iingfthereon. The roofing-'of the present. invention is suitable; for improving the iire. resistance'AA and: resistance Ito. indentation and rupture of builteup roo'ng'since the.;rooflng: of the present invention notionly has:` veryhigh` nre resistance. butl also;I has. considerably .'more toughness; andresistancetexurexhan. ordinary rooiing-` materials.V user ,asil the .upper layer'. of built-.up roonaroong, material. embodyingr thisinvention mayybemad'e up; into.= sheets-or. may.
be madein. the form. of; vtile-like: pieces adapted to be bonded in placeby a-.lniturninousl adhesive...l The tire-resistantL bituminous composition', of: the present invention maylikewisebe usecliind the.V
manufacture of multi-plyprepared sheets-i con-.-V sisting of av pluralityV oit-:layers oi` bituminized mineral fiber: or vorganic fiber felt or otherviabric having onaor more layer s.o.bituminous com positionA therebetween.Y Thisvl type on rootingis` inherently semi-rigidinfcharacter andthe highly l mineralized rerresis'tant.- bituminous; vcomposition of. this@ invention IisLwll/suitedforuse asa.
weatherand. waterpooiing; layery therein; either between` the plesofp.' fabricv oriv as ahsurface. or-
backing layer or both.` Onetype otroong'm'adef in this way hasan unsaturated sheet-of. asbestos felt as the top layerA sas to. provide resistzanc'e.v
to iire caused, by, falling Asparkssilch. as. arelilely to occur in the vicinity ofrailroads,srnelteratetc.V According` to" the`. present invention, greater weather-resistanceand at the Vsame timegreat'er.
fire-'resistance is obtainable lby'- .providing as the upper or weather-exposed surface; -of; this type of prepared roofing a bituminous" surface layer consisting of the highly mineralized tire-resistant bituminous composition 'offy this invention.
While theroongof this invention is particularly suitedl forVv purposes suoli as those above 4 mentioned, roofing in the form of shingles, siding' and the like may embody the highly fire-resistant bituminous coating composition of this invention. When shingles, either individualerN strip shingles, are preparedv according. tb this invention, they usually are somewhat more stii' than' conven- .tional bituminous prepared roong materials, but
vthey are well suited for use Wherever bituminous shingles andgthelilge may be used, and are thus oi special advantage in regions Where high winds arev likely to bef encountered, as, due to their si'iifness-,lthey'`re's' i'st`- blowing up or "fluttering" in the wind 'iflreiroofings of the present invention usuali'yi'iave higher tensile strength than conventional rooiin'gs and this feature also is advantageous for certain purposes.
In' our application Ser. No. 497,805 which was filed simultaneously with our present application and-.which has .resulted in PatentLNo. 2,424,234,v
we have: described and' claimedfa: bituminouscm'-- position especially adapted'. fox'use. as the inopping asphalt ini the; constrircti'on:` otthuiltlni Y rooiings, the composition possessingfhiglr fixieresistancev :by virtu'efof its` 'fornnilatiort `soz as. to: comprise. bitumen!` having-a1 softening; pointilieif tween, about 80,2 F-.fandz abbut.200F:.a;nd; ot
range; 35% -to 60% ofthe: compositionso: as to'.-y
comprise intimately coinmingled.'and` distributed. uniformly throughoutthe bitumenineiyr-divided' solid. water-insoluble:heateresistant mineral ller' whichl is -of the rang'e 40% 116.65%? by weiglitfot! they composition with,- at 1east% byfwei'ght thereofr passing 'a.100 mesh:v testing; sieve,;-and;'so as".- taf have a Wagner-Bowenplasticity.'value at 4005* E: not substantially'g-reater than? '250-A grams, the iiller inthe compositionhavinga flowresistance' coeiiicient ofV at leavstr'l when' the; composition isf subjected to the now; resistance 4testfthatiis de@ ned in Vthe application. 1 Thef bituminous: coms position disclosed in ourf aforesaid'y application Ser. No. 497,805 successfullysolved:v the; specici problem of providing a; mopping asphalt suitable as the, waterproong; adhesive betweenl the pliesv catedl hereinabove. The-requirementsfonaiord@ ing a highly re. resistive roofing: productaccordisistvemopping-.as'phalt compositie accordingto theinvention. di'sclosed.in,v ours said 'applicationr Ser. No', 497,80'51in scveralsigniiicantrespects one of which. is ,thatwli-lel'the mopping-, asphaltscom position4 disclosedQin our said ,app licatiorris(1i-mitad.l
to one wherein. tIief.Waghe'r.-Bo'wenplasticity-- value .at 400 is not'substantially grease; .than 250. grams, the highly` '-mineralized .coating conv position combinedwitn. a Base. slieetl accqrdina to ourjj presentH invention, compn'ahends,A coating. j
compositionsl whose." Wagner-Bowen plasticity value 'at 4ooF. is-sunstanuanygrear. uamzso grams vWhile4 notzbeing; substantially greater than.` 1500 grams;l Moreover1- the coating ofithe rooilng.
product` of- 'our present invention "comprehends coatings having the ttcmmercialln important advantage..ofheine.hiehlyfblisteteretstantnthecoatft ings in. such case utilizing,... bitumen-.having a:
proofing layer.. overlying abase, sheet.. offfelted.v
ber. orr the like tend tofbesconsumedmhen sulojected toY flame. and to, flow. down an` inclined' roof-l deck leaving. thegunderlying, brous. sheet. exposed to the. destructive; action of, the. heat ,of` the. fla'rne. Thus a llcrumaterialisuch as powdered4 limestone. or.- slate, flourl'elvenvv Wlierrincor.-` porated na.. bituminous composition to an ex.- tent` as fhigh as 55%V by., weight of t1ie.bit uminous coating compositiom has little. eect; in reducing the combu'stibility andresistance to. flowingl of',` thev bituminous. coating composition. Y t "Wey have foundv that in the ormulation of bituminous' coating compositions. suitable for. roofing there. is. apcriticalpoint below which. a finely-divided"A mineral ller exerts little., ifA any, eiectupon. the combustibility andiloyvresistance oi" bituminous coating compositions but. `above whichV evenslight. further additions ofifthemin eral. filler exert a profoundeiectffupon theY combustibility. and'Y flow.. resistance. ofthe bituminous coating composition. This critical point usually is in thev4 neighborhood of 'themaximum amount of the ller in questicnthat canv be successfully mixed'andv spread' as a satisfactory coatingup'on a base sheet'suchas a sheetoasplialtrsaturated" organic fiber felt. This.crticallipointlis.,dierenty for diiferent mineralgkllers, .and.usuallyA is. found' to occur at a mineral iiller content of Vabout 60% to" about. l80% by VWeight-.ofithe-zbitumincus l.composition, dependingY on the particulary mineral filler used; The critcaljpoint also isiiaictediby thel typev ofbitumeni that is used asjtheg. Watere proofing base foib thebiti-iminousI composition.
When reference is madehereinftc bitumen this term' is-usedhereinvr in' reference to asphalt,v
pitch; tar and the like;V by-litselfiandunmixed with filler.'- -When,v on the otherihand: reference` isemade herein to abituminousf'materiali or-a bituminous composition, ora at-bitumineus-coat-Y- ing; or vaalcituminous layer; referencezisvmade-tol av materiaL; composition,V coating f orf layer @com-pris ing bitumen either with or.'without' atller;
It is agfeature; of: this.r inventionathat thereis employedv as .bituminousfcoating composition ofv roofing material, highly rnineralizedfbituminous-r composition Wi-thin: the. Vnarrcivv. zone above. the critical point at which; the coating'. composition becomes highly resistant to ow when exposedV to -ametempera-tureand; b elovvthef. point; at which thecoating becomes-g.ofi-'excessively high?, plasticity or consistency atllfl Whenithei bituminous coating; is formulated.v so; that.: its properties yloe within-thisxzone. We; haveY found. that a satisfactory rooting of high resistancetoI nre is obtained. s Wheny aJ rooi'lngicarrying-xaibi; tuminous composition 'is-s formulateiliA Within. the limits iustrrmentionednweehaveerounmtnat. ther.-
nouncedZ newv resistance -.of.biturnino.us. composif Stable and. erentrand-th holds-thefbtumeni. inplaceisotthatl doesfnot flo. own a inclined?. roofgdeclst si; atroci declinar/instar?! ties-reeine-l 'z cli.Iltiftiorlf-to-V the horizontal..1eavine5-the-under1yeina-material such; as .an combustible' organic; felt-1 base sheet exposed to the iiame. Anoth.` tt i bute of :f the molina isf. thattheiirefresistant tumrions; .coatinezfwhenz .exnoseiistof hiein;tenc..-=v peratlirs :tfor apnroachneiiiame@temperatures;-
' keimassiwvhichv bustble rrocft deck rcmftheaheatiOff thaffamsf f Anothenattrihute he .efresistantrcoatinesisf that I*iti sfhiehlv'resistant .tm-combustion: soit-hat.; if it tends to char upon expDSill :toeaineptheacharringf and combustion aregveryegradual and discontinue. without sulcstantiaflT spreadingii asf soon as exposure; tolfiame is;discontinued:y By.;
formulation of-` they. bituminous coating; VconnV .positionwithin theflimits speciedrherein and-finzi the. claims,4 these eifectsw-herebyjthefiller; r tainsf-Kthe bitumen evenf whenl theicoatingff is;V heated to. a temperaturef at or;agdj.accent;y flamesy temperature and E wherebyithei bitumentuooniexet posure A to; fiamet. carbonizest.- as:y a5; cementitiousv` charred mass-.that formswith the skeletagljmatzofi ber a coherent; lire-,resistant heatinsulating; protective v layer, are attained; andggifjthese1:critifz cal limitsfare departed fromthe roonggno longer.: has the hey resistanceof A the .rooiing;therein.l denedbut fails in fire resistance fon-'such ,areasonsf; as `excessivecombustilcility ofjthegcoatin'g; bleed-- ing and running;l of j the bitumen;; flowing; ofi. the.: coating .as `a Whole so as to expose theiunderlyingY base sheet.. excessive separation from f the;` base.` sheet, disintegration 'ort excessvercraclcin'gfof the .e coating; on exposure V=to ame,jza.nd; thef'like;l
Other features of this` invention.;relate;tof?.- the."vr
n disposition of'V the` special coating-.ymaterim strata in -roof deckfco,veringscvv In the-case of mineral filler.fmaterialsrsuchiasyi slate flour or powdered limestonefthat;'aregnonefiilorouaV theY criticalvpoint at.;Whicllrl;thefpr,,rN
tions when exposed tofiiame;` tempraturesisgat tained', iS'V usuallyA in thev upnempor on; oi fthe:- filler rangementionedj above.;A Theicriticalgpointu. inthecase of such non-iibrollssmineral;llen mar riticakchangezf Willv occury with a4 lesser total; kfiller:` content. byr mixing; with. the f powderednon-brousf` iilleit :ae finely-divided mineral Y fiber; flvllerjf passing.' ai mesh testing sieve and retained on a 200-fmeslfr testing sieve.V Fibrous mineralnller. is..nlore..ei..Y fective inV affording high flow resistance than is a non-:lorous mineral filler, although, as Will be pointed. out more in detail hereinbelow, certain screengradings Vof fibrous minerailler arecon-Lpv j siderably more Yeifectivethan others.V ltiSlQre men in thecomposition as'tot-impart-very-highf;
7gg fexempliiic atieninconnectionWithamtypicalfem:
7 bodiment. The roofing material of this embodiment is composed of strain-resisting roong felt, a top 'weather surface coating of special bituminous coating composition, a surface layer of mineral granules partially embedded in the surface coating, a thinner layer ofthe special coating composition'on the back of the felt base sheet, and finely-divided dusting material adherent to the back layer of the special bituminous coating composition. v
In the exemplary embodiment, the base or foundation sheet is ordinary roofing felt made of vegetable and animal fibers, e. g., a roofing felt made from organic fiber stock weighing about 6 pounds per 100 square feet. The felt is impregnated with a suitable impregnating material, e. g., a conventional bituminous roofing saturant having a softening point of about 120 F. to about 170 F. The base sheet as thus composed has little fire resistance and, when exposed to fire, is consumed quite readily.
A typical example of the special coating composition may be made as follows: The bitumen used in the coating is preferably a residual asphalt iiux from the refining of Mid-Continent petroleum which has been oxidized as by air blowing until it has a softening point o f about 200 to 210 F. and constitutes about 32% by weight of the composition.' With this asphalt there is intimately commingled and distributed uniformly throughout finely-divided mineral iiller which constitutes68% by Weight of the composition. The ller consists of powdered limestone which constitutes about 47% by weight of the composition and asbestos dust which constitutesV about 21% by weight of the composition. The powdered limestone is limestone which has been reduced to a pulverulent condition, about 85% by Weight of it passing a 200 mesh testing sieve. The asbestos dust is such that nearly all passes a 14 mesh testing sieve, with about 75% by weight retained'on a 200 mesh testing sieve and about 25% by weight passing a 200 mesh testing sieve. Suchasbestos dust is considerably nner in particle size kthan the asbestos which is ordinarily placed on the market and which is known in the art as fiber. Heretofore such asbestos vdust has generally been discarded in enormous amounts in dumps at the mines as a waste -product while the usual asbestos fibers of commerce have been recovered and sold.
The screen'g'rading of the asbestos dust used in the coating composition of the exampleof this invention appears below. The vpercentages given are Vpercentages by Weight contained inthe bituv Percent bituminous Screen gradings composition v Total asbestos dust in composition A given screenv gradingV Other screen gradings are indicated contained in t 8 In preparing the special coating material, the asphalt is heated toa heat-liquefied condition and the asbestos dust and limestone dust are thoroughly mixed therewith. The mixing preferably is carried out at a temperature of about 375 F. to 475 F. It is important that the bitumen and finely-divided filler-be thoroughly mixed and intimately commingled so that the composition of the coating with respect to the distribution of the filler therein isl uniform throughout. The composition` should be applied to the felt base sheet while in a thoroughly mixed condition so that the resulting layer is substantially uniform in consistency and in thickness. In the typical embodiment hereindescribed, the coating is applied to the felt base sheet at the rate of about 45 pounds per 100 square feet. Before the coating Vcools toV atmospheric temperature, a conventional surfacing material such as slate granules, can be applied to the surface for weather exposure and these granules,l are partially embedded in the coating composition. The granular surfacing material ispreferably non-combustible and, while employed, is not relied upon to impart re resistance to the roofing. On the opposite side of the roofing material, there may be applied a thin coating of bituminous coating material, e. g., an asphalt having a softening point of about 200 to 240 F., so as'to weigh about 5 pounds per 100 square feet, and finely-divided dusting or antistick material such as talc or mica dust or similar material may be applied and partially embedded in the back coating. Preferably, for maximum iire resistance, the back coating should be special coating composition embodying our invention.
The roofing thus prepared may be packaged in sheet form, or, alternatively, may be cut into sections suitable for shingles or tile-like units. The roofing weighs about pounds per 100 square feet. Of this weight, about 30% by weight is in the form of mineral granules adherent to one side and finely-divided dusting material adhered to the other side, the balanceof the roofing being the felt, the bituminous impregnating material and the bituminous coating material.
The special bituminous coating composition may advantageously be mixed and applied in the manner mentioned in our said application Ser. No. 370,686 (Patent No. 2,326,723). As stated in said application, the coating composition may, if desired in order to increase the resistance of the applied coating to blistering, be applied using the method and apparatus of our Patents Nos. 2,105,531 andv 2,159,587, but this is not essential.
The roofing material above described can be made up into suitable preferred roofing materials and into suitable roofing structures, description of typical roofing structures being facilitated by reference to the accompanying drawings, wherein Fig. 1 is a plan viewof prepared roofing material embodying our'inventionin the form of a rectangular unit;
Fig. .2A is a fragmentary sectional view on an enlralrged scale of the roofing material shown in Fig. 3 is a plan View, somewhat diagrammatic, of a `built-up roofing embodying roong made according to our invention;
Fig. 4 is a fragmentary cross-sectional view on an enlarged scale of the' built-up roofing shown in Fig. 3;
Fig. 5 is a plan View of prepared roofing material embodying ouriinvention that has been cut ina form -suitable for use as a strip shingle;
'Figi is a'fragmentary sectional view onl an enlarged scale of the rooing material shown in Fig.
Fig. '7 is a sectional view of a roof covering composedof strip shingles laid on an inclined roof deck Without' showing the componentl layers of the individual shingles;
y Fig. 8 is an enlarged sectional elevational View cfa portion of the roof shown in Fig. 7;
Fig. 9 is similar to Fig. S'except that the roofing is shown as itappears after exposure to flame temperature;
Fig. l0 isa fragmentary sectional view of an other embodiment of this invention;
Fig. 11 is a side elevation partly in section of a testing device for testing the flow resistance of llermaterial as incorporated in a bituminous composition; I
Fig. 12 is a plan view partly in section of the testing device; A i Y Fig.V 13 is a front elevation of the test panel assembly:
Fig. 14 is a side elevation of the test panel assembly;
Fig. 15 is a plan View of the test panel assembly vwith parts thereof broken away; l
Fig. 16 is a perspective view'of the frame and guard plate used in the test panel assembly;
K Fig. Y17 is a longitudinal sectional detail view on an enlarged scale of the orifice in the gas line leagiipg to the burner of the testing device; 2,8 is an end elevation of the Wagner- Bowet plasticimeter testing device;
Figc-19 is a plan View of the plasticimeter;
Fig.;Y vis a front elevation partly in section of the plasticimeter; l 1 Fig. 2l is a side detail Velevation of the drag -.tooland drag tool support of the plasticimeter;
Fig.n 22A, 22B, and Fig. 22C are views of the smoothing blade of the plasticimeter taken respectively in elevation normal to the line A-A pf Fig. 19, from the bottom, and in elevation from the back in the direction of the line A-A of Fig. 19;
23A, Fig'. 23B, and Fig. 23C are views of vthe mixing bladeof the plasticimeter taken respectively in elevation normal to the line B-B of Fig. 19, from the bottom, and in elevation from the back in the direction of the line B-B of Fig. 19.
Prepared roong material embodying this inventionA may be in the form of a unit 33 which may be of rectangular shape as shown in Fig. 1 or of any other desired shape. The cross section of this embodiment is shown in Fig. 2 and comprisesa base or foundation sheet 3l of bitumen impregnated roong felt. 'Overlying the roofing felt is the coating32 of special coating composition having adherent to the surface thereof and partially embedded therein slate granules 33. Whilethe prepared roofing material is illustrated in the form of a unit of special shape, the roofing material may, of course, be in the form of larger ,sheets or in the form of rolls of indefinite length .of the roofing material.
In Figs. 3 and 4, roong embodying the special I,coating composition of this invention is shown :in connection with built-up roofing. The roof vdeck 3s, has sheets 35 of red rosin paper or the j like applied thereto as a single thickness. Overjlying the red rosin paper are two layers 36 and 331, the layer 35 consisting of bituminized felt 35a and bituminous coating 35h and the layer 31 ,consisting of bituminized felt 31a and bituminous ...coating 31h. The layers 36 and 31 are bonded Vrunning down the roof spreads the lire.
. 10 together by a layer 38 of mopping asphalt; Adi herent to the upper side of layer 31 by a layer of mopping asphalt 39 are a plurality of the tile: j
which comprise the like roofing elements 3B layer of bi'tuminized felt 3|, the layer of special bituminous coating composition 32 and ls'urfacy ing granules 33. In such a built-up roofing the tile-like roofing elements 3S provide a highly fire? resistant surface coating. Moreover, sincethese roofing elements carry a highly mineralized surface coating, they have more rigidityand strength than ordinary roong materialsused.l
for the surface of built-up'rooflngs andprovide a surface that will withstand considerable Walking upon andthe action of other loads that tend to indent or rupture the surface o f the roof' covering.
By causing the layers 36h and 37b ofthe bituminous composition to be of the special char actei' described herein or to be of the special character described in our application Ser; No, 370.636 above mentioned. the built-up moins as. a Whoie'can be made so .as to have extremely high resistance to nre.
'In Fig. 5 prepared roofing embodying the spee cial coating composition of this 4invention is: shown as cut in the form of a strip shingle 43, In cross-section the prepared rooiing appears as in Fig. 6 and comprises a` base or foundation sheet 4| with an overlying layer #l2 of the special bituminous coating composition. rGranules 43 are partially embedded inthe layer 42. Adherent to the back or une roofing material is a layer 44 of the special bituminous coating material in which is partially embedded dusting material 43.
In Fig. 7 is shown a typical roonng structure in place on a roof deck comprising boards 'Sii which serve as a support for the shingles 43. The shingles 4i] may be 16 inches from the butt to the .top and may be laid with a 5-inch eX-' posure, thereby affording triple coverage over all parts of the roof deck except for the double coverage area beneath the cutouts. The comL ponent parts 0I' the individual shingles appear in detail on' the enlarged fragmentary' View snown in Fig. 8.
A roofing structure of the character described in the above example has extremely high fireresistance. Thus a roofing such as that shown in Figs. 7 and 8 comprising three thicknesses of the special roofing of this invention Will Withstand the Class A fire-retardant tests as prescribed by Underwriters Laboratories, Inc., in their published instructions. As mentioned above, we do not know of any commercial prepared bituminous rooiing made on a felt base of organic fibers which, irrespective of the weight of the roofing material or the number of layers or plies that are applied to the roof deck, will successfully pass either the Class A nre-retardant tests or will even pass the Class B lire-retardant tests of Underwriters Laboratories, Inc.V
When ordinary bituminous prepared roong such as ordinary asphalt shingles is' subjected to the Class A burning brand test, the bituminous coating composition When exposed to the burning brand melts and as a mass starts running down the surface of the roof.. The melted asphalt also starts to burn and the burning asphalt in The coating composition that runs down the roof leaves the bituminous organic liber felt base exposed, which. being readily combustiblefstarts quite readily and ignites the combustibleroof deck in a relatively short time.
By way of contrast, our improved roong made as above described by way of example behaves very diiferently when subjected to the same burning brand test. The behavior of the roofing material as applied to a roof deck in three layers, e. g., as shown in Figs; 7 and 8, is indicated roughly in Fig. 9. During exposure to the flame, the bitumen and filler remain in place and the llerprovides a skeletal mat so that, as the bitumen in the coating carbonizes, a coherent protective mat-like layer is formed that shields the underlying roof deck from the heat of the flame. Moreover, especially when a mineral ller such as asbestos dust is present that contains water of constitution liberatable at or adjacent flame temperature, small bubbles 41 form in the residual coherent mat-like mass that tend to augment the heat insulation effectiveness of the carbonized residue. In the roof covering structure as a whole as illustrated in Fig. 9, the upper layer of special coating composition has become expanded and has become somewhat irregular but still remains as a protective coherent heat-insulating mat-like mass. The layer of felt 4l may be carbonized and i to a considerable degree may have disappeared, leaving air pockets 48 with some residual carbonized material. The intermediate layer of special coating material is also expanded and remains in place as a protective mat. The intermediate layer of feit is charred but is better preserved than the uppermost layer of felt. The bottom layer of special coating composition is less severely carbonized than the upper layer and islikewise substantially expanded. The bottom layer of felt is fairly well preserved and the underlying board, if charred at all, has not become ignited. It usually takes the burning brand used in making the Underwriters Class A burning brand test about to 45 minutes to burn out. During this time, the upper surface of the uppermost layer 42 may become red-hot, but the heat insulating eiect of the underlying carbonized residue 'of layers 42 (and to a lesser degree of the thinner layers 44) is so great that the board 46 does not become ignited and in some cases does not even appear scorched. During this test, the effect of the flame on the roofing is confined to the area beneath and closely adjacent to the position of the burning brand, and, when the brand burns out, all charring of the roofing soon ceases and the roofing cools down. The behavior of the roofing hereinabove described under the ClassjA flame exposure test is generally similar tothat just described in connection with the Class A burning brand test. Such roofing also passes the Class A flame spread test. In the case of built-up roofing such as that shown in Figs.V 3 and 4,'the behavior upon exposure to flame, if the layers of coating composition are of the special character herein defined, will be similar to that just described. If roofing is made up so as to provide double coverage instead of triple coverage, roofing of the composition aforesaid will pass the Class B nre-retardant tests of Underwriters Laboratories, Inc. Instead of using strip shingles, the roofing shown in Figs. 7, 8 and 9 may, if desired, be made up with individual shingles embodying the special coating composition of this invention.
The fire-resistance of the bituminous coating composition described in the foregoing exemplary embodiment of this invention is obtainable due to the fact that the filler-asphalt mixture is formulated within the c 'ritical zone or range determined on the one hand by the minimum flow resistance coefficient under the flow resistance test at flame temperaturel to be described below, and, on the other hand, by the maximum plasticity value at 400 F. under the plasticity test which also will be described below. As aforesaid, a filler material such as the ller material used in the foregoing exemplary embodiment of this invention exercises only very slight effect onthe nre-resistance of roofing, which effect is negligible as far as useful increase in nre-resistance is concerned, even when the ller material is used in considerable quantities up to about 55% by weight of the composition. Thus utilizing the filler of the foregoing example which consists substantially of 1 part of asbestos dust for each 2% parts of powdered limestone, the flow resistance coefficient of the filler is only about 50,'even when the filler constitutes about 45 by Weight o! l the composition. the balance of the composition consisting of asphalt having a softening point of 205 F. This is somewhat higher thanfthe flow resistance coefficient of 22 which is obtained when the same asphalt is used but withoutany filler being included therein but still represents a very low and inadequate degree of flow re- Sistance. However, by further addition of the filler material, other conditions of the test and of the tested sample remaining the same, the flow resistance coefficient of the filler increases very rapidly and, in the case of the exemplary embodiment hereinabove described, becomes increased to the maximum possible value of 100, namely, a condition such that there is no flow whatever of the bituminous coating composition when exposed to flame temperature. It 'is apparent, therefore, that there is critical and sharp change that occurs and brings about a greatly modified physical condition of the bituminous composition and at which the action of the filler changes from affording only a low flow resistance coeilicient to affording a very high flow resistance coefficient. When the condition of high flow resistance coefficient is attained, there is a cooperative action between the filler and the bitumen in the coating. On the one hand, the filler material serves to prevent the bitumen under the heat of the flame from running and burning. On the other hand` the bitumen during carbonization as held in place by the filler provides a carbonaceous binder that cements the filler material together as a coherent mass that has substantial inherent strength and that prevents the vfiller from crumbling and being displaced. The result is a mat-like mass of considerable body and o oherence that has very high heat insulating effectiveness and that serves as a very effective barrier in protectingthe underlying roof deckifroxn the heat of the flame.
We have found that the flow resistance coeicient of a filler or ller mixture as dispersed in the bitumen of a bituminous composition is a definite and measurable propertyv that, while a different type phenomenon, may be likened to the property of certain substances of raising or lowering the boiling point of a liquid in which the substance is dissolved. We have also found that high fire-resistance is provided if the flow-resistance coefficient is sufficiently high. In order to ac` curately determine the flow-resistance coeiicient and thereby enable us to precisely define the highly fire-*resistant roongs of this invention, we have devised a test whereby the flow-resistance coefficient r ofi a particularI ller: or.. filler. mixture;
inabituminous composition under. conditionsy ofk sistingof'the bitumen and the.lleroriillermix ture, to be tested, under precisely-controlled conf-l ditions. determined by the construction and opera.- tion ofthe testing apparatus. The following Vis a; description of the controlled conditionsjofthev test, reference. being made. to. Figs. 11` to -11A of. the drawings'.
Samples carrying thgbituminousi composition` containing the ller or ller mixture to -be tested are made by applying the bituminous coatingV composition tothe base sheetmater'ial soY that the coating weighs 30r pounds; plusor.y minus 2. pounds. per 100 square, feet. y
The test is made ina wind tunnel 53 having a fan at one end and a stack 52 atthe other end. The tunnel is made of 1A inch thick'asbestos.- cement lumber Aand has. two Windows 53 and, 54 thereinwhichA can be opened andr closed by any suitable means (not shown),
Within. the tunnel are, the burner. and testing deck which are located between two shields 55 and 551 of the asbestos-cement lumber spacedA 121A inches apart, and whichk are rigidly mounted on the asbestos-cement slab 56. The inclined test deck is indi-cated generally by thereference character 51 and c-omprisesa lower frame-like member 58 having 1A; inch pegsv 59. projecting from the face; adjacent the upper and lower margins. Between the. pegs 59, strips '60 of asbestos-cement boards 1% X 12 X lrinches are. placed. One ply 12 x. 12 inches ofthe prepared coated sample T3 to. be tested is .placed onA the asbestos-cement boards. 60 followed by an Lshaped guard plate 6| Which'covers ther bottom. edge of. thesarnple` The assembly is helddovvn by an iron frame. 62 and held in place by thumb screws 63.
After the test deckv has been assembled, it is placed on theinclined support 54 which has' an opening in the back underneath the. strips 60 and which has side flanges E5 to protect each side of the test panel. The support S4 comprises a bafe 66 to prevent the flame licking around behind the test deck. The'support, which is made of iron, is mounted on the asbestos-cement slab 55'- which measures 12 X 40 X 1 inches. The partsforcarry- In front of thetest deckl is the burner 68 com- ,y
prising an iron. pipehav-inganinside diameter of .472 inch and an outside diameter of .675 inch, with 17 holes 0.078 inch in diameter and M2 inch apart disposed atan angle that is parallel with the plane of the test deck. The'burner is provided with an inlet'line 69 controlled by a shutoff valve i0. In the line 69 is an orice 16, 5,64 inch in diameter, that is located in the housing connections '11. Between the valve 10 and the orice is a manometer 12. By this arrangement. a supply of gas under constant pressure can be obtained, thereby obtaining a steady flame .of constant intensity during the. test.
At the base. of the Vtest deck and betweenthe Y They dimensions of thedifferent .parts ofthe I4.' testing-apparatus shown.. in'the; drawings :asised byusrarezas-.followsz Inches;
a 24 V'o 8 b' 38 `1o 2 b v6. q c 181/2 'r l; d 72 s. 1'2', e 16%, 'tf "l" f 10v uf 'm1/21 g 12124; v "12v 4 h 3 8v w .TT
k 24 y fA Z 24 z' 6 m 40 aa" T12A n 27' bb 1 Inf carrying out the. test, the4 apparatusf is1 first.
assembled` and the burner is lighted so asto provide a. pilot flame-that is about. 1/2 inchin length when the fan is operating, Thewindows 53 and. 54 are then closed and the room in which'V the apparatus is placed is arranged so that there. will be'relatively constant conditions during4 the. test. The temperatureand .relative humidity-.of the room should bev approximately and 40%, respectively. The fan should generate a. wind Velocity of about -155 ft.per minute-atv theportion ofthe deckexposed to the name.
The =Va-lve l is then opened until a. flame-aboutil S to Q-inches long is produced havinga tempera ture of, about'1325-1370 F.. When thevalve '10. is opened to produce such .ameL'a timing device is. started. After. the. sample. has. been exposed.; to the flame. for a period ofl five minutes, their-lama is turned` off and simultaneously the cover 1511s;A
placed over the top of pan 'I4 so as to prevent. any further bituminous, composition that may flow down .the test deck from collecting in the` pan. Before the commencement of the test, the pan 74 .is carefully weighed and at thezconclusionof the test is again weighed, the difference in Weight being the. number of grams of'bituminous coating materialv that' .has owed into thepan.. Before making the testthe weight of the bituminous coating on the. test sample is. determined by weighing the base sheet material before, the bituminous coating is applied thereto` andA Weghingjthe complete sample, the difference, bef'r ing the Weight of thecoating.
The` coeicient of flow resistance is-.oomputed accordingv to following expression.
tv eight infgramso coating collected in panX'lOO total' Weight in grams of coating"priorV to test'.
For example, if the. weight of the bituminous coating on the sample. waslOOQgrams prior .to
testing and 50 grams of the coating were col,-
lected in the. Dan. during the test, the. coefficient. of flow resistance-would be If nov vcoating composition ovvs into thegpan.,v
sistance of the coating, if attained, is due to.- presence of the liiller in an amount'thatequals or exceeds the critical. amount for'the l1erlun` Y .dergoing test. It may be mentioned, however,A
that-the amount of a given finer that is critican will usually vary somewhat depending upon the bitumen that is used in the bituminous composition'.- Thus the critical amount of filler for a so-called cracked asphalt, namely, oxidized asphaltic cracking still residue, is usuallysomewhat less than for a Vstraight run asphalt residue.
Another factor that influences the flow resistance coefficient somewhat is the'character of the surface'to which the bituminous coating compo-V sition is applied. In the manufacture of roofing material, a typical asphalt saturated organic fiber felt base sheet weighs about 30 lbs. per 100 square feet whichA is'saturated to the 'extent of about 175% by weight with asphalt having a softening point of about 150 F., so for most purposes an asphalt'satur'ated "felt such as'this maybe used in making the test. However, for bituminous compositions which have incorporated the critical amount of filler to render the composition highly flow-resistant, the asphalt in an asphalt saturated base sheet exerts an effect as a lubricant at the interface between the base sheet and the coating composition which tends, depending upon the amount of asphalt in the base sheet, to lower somewhat the flow resistance coefficient as determined by the test; This effect can be counteracted by indenting or otherwise causing the surface of the felt base sheet tc be rougher than normal; By using a dry or unsaturated felt base sheet, especially base sheet material having relatively coarse bers, the flow resistance coefficient of the bituminous composition per se is attained without being influenced by an effect that the bitumen in the base sheet may have. However, since the special coating composition of this invention may be utilized overlying the surface of different kinds of base sheet material, it is best to carry out the flow resistance test using as the base sheet for the test sample the kind of base sheet that is to be used in the commercial roofing to be manufactured.
According to this invention, the special reresistant bituminous coating composition can be formulated so that the flow resistance coefficient will be as high as 100. However, greatly improved re resistance is obtained according to the invention when the flow resistance coefficient of the ller in the coating of the roofing in question is 75 or greater, although it is preferable to formulate the bituminous coating compositions so that the flow resistance coeficient of the filler in the bituminous coating composition is 90 or above.
As aforesaid, the different screen gradings of a: fibrous mineral filler such as asbestos dust have been found by us to differ considerably in their effectiveness in imparting flow resistance to a bituminous coating composition. In view of these differences in effectiveness of the different screen gradings of a mineral fiber such as asbestos dust, we have, in order to indicate more definitely the amount of mineral fiber of given screen gradings that is required to effect stabilization of a bituminous composition, assigned to the different screen gradings what we have called the screen factor" for each of the different gradings. Thus if the screen grading 28-l-35') is taken as having a screen factor of unity, any screen grading that requires half the amount as compared with the screen grading 28-1-35) will be twice as effective and will have a screen factor of 2. On the other hand, a screen grading thatr requires twice the amount as compared with the screen grading (-28+35) will only have half the effectiveness and will have a screen gradingl of 0.5;"'InY like manner, screen factors can be assigned to each of the other screen gradings.
The above-described test for measuring the flow resistance coeflcient of a filler in a bituminous composition affords a convenient basis for setting up the screen factors of brous mineral fillers on a definite scale and, when the screen factor of a given screen fraction of a fibrous mineral is referred to herein, the screen factor as determined in the following manner is intended. The test for determining the flow resistance coefficient is carried out using the test apparatus and procedure above described except that in all cases the total filler is 55% by weight of the bituminous composition. The asphalt in all cases is oxidized straight run asphalt having a softening point of about 205 F. Slate flour about by weight of which passes a 200 mesh testing sieve is used in all cases as the standard diluentller, and the amount by Weight of the particular screen grading of fibrous mineral to achieve a flow resistance coefficient of about 75, Ias ascertained by the average of a plurality of runs, is determined. Each sample is prepared using the asphalt saturated organic fiber felt above specified, namely, conventional organic fiber roofing felt weighing about 30 pounds per square feet that has been saturated to the extent of about 175% by Weight with asphalt having a softening point of about F. As a standard, chrysotile asbestos dust; of the grading 28-1-35) is taken as having a screen factor of unity and the factor for each of the other gradings is calculated to this standard. By Way of concrete example, it being the case that substantially 15% by Weight of the bituminous composition of chrysotile asbestos dust having the screen grading -28-l-35) (the total filler being 55% as aforesaid), is required to afford a flow resistance coefficient of substantially 75, and it also being the case that only about 3% by weight of the bituminous composition of chrysotile asbestos of the screen grading (e6-+8.) (the total filler again being 55%), also affords a flow resistance coefficient of about 75, the screen factor of chrysotile asbestos dust having the screen grading (-6+8) is seen to be about 5.
By way of further illustration, the screen facj tors of the different screen gradings of a typicalchrysotile asbestos dust on the basis above mentioned are as follows:
Screen Grading Screen Factor Ito this particular screen grading. Similarly, in
eiectiveness of a iibrousmineral filler. Given the Y percentage by weight of each of the screen gradings of mineral ber contained in a bituminous `composition, the percentage by weight of each .multiplied by the screen factor for each gives what we term herein and in the claims the grading index.for Veach of the screen gradings; and, by :adding the grading indices vfor the several screen gradngs together, 'the grading index for Y.the total mineral fiber is readily determined. By way of illustration, the grading index of the mineral liber .component .of rthe 'above-mentioned typ- It is apparent that in the formulation of .a bituminous coating composition one can, from the screen analysis ofza mineral ber such. asa-sbestos dust, determine the Ygrading index of the mineral fiber employed andjthereby determine the effectiveness of the mineral .fiber inthe amount used in stabilizing the bitumen in the coating composition. As mentioned above, we have .found that in highly mineraliaed coatings one can, by attaining vthey critical point at which there is a sudden increase in the flow resistance coeiiicient, provide a fire-resistant roofing even though -brous mineral 'is not employed. "However, the coating composition is improved 'when mineral ber is present in an amountand of such screen grarlingsl lthat the vratio .ofthe grading vindex to the per cent. by weight of bitumen in the composition is at least 1 to i8 and it is vpreferable that therrat'io beabout '1 5to 5. Thesefratios are applicableior the range from to 45% by Weight of bitumen in the composition Yand are yespecially isutable when the bitumen is Vof the vrange 20% to 35% by weight. 'When the` bitumen content of' the bituminous composition is of the range :35% to .45% by weight, it is usually desirable that vthe ratio of the gradingindextothe percent. by weight vof bitumen be .about .1 -to .6 .and preferably .about l, .to V3. .Referring 'to Athe fforegoing '.example, .the grading' index, of the. brous zmineral was seen `to be 12.9, fand since lthe per cent. by Aweight oi asphalt in the composition .32% by weight, the ratio of .thegrading .index tothe-per cent. by' weightrof asphalt .is .about .1 .to 2:5, which .is well within the minimumratios just mentioned.
When. referenceis .made herein to screen .1fac- .tOrFfand grading vindex 4of `iibrous :mineral ller, the reierencefisA-made .to these'values when deter- .mined-asfhereinabove. described. 'Vi/Then, however, reference .is made tojiiow resistance .ademt-2161.11?
".of a iiller ori-111er mixture, the iiow resistance coeflcient, unless otherwise specied, is that of the ll'er or ller mixture in whatever amount it is present as commingled with the kind of asphalt employed in the bituminous composition.
the bituminous composition being tested as applied to the base sheet ofthe commercial product.
In determining the screen fractions orgradyings of brous or other mineral llers that are referred'to herein, 8 inch diameter testing vsieves of the W. S. Tyler Company sieve series, meeting A. S. T. M. Standard E11-39 for Sieves for Testing Purposes have been used. A quantity of filler to be screened, ranging vfrom 20.0 to 300 grams, iis placed in the uppermost of aseriesof i testing -sieves -a-nd subjected to suitable agitation as in a standard W. S. Tyler Company Ro Tap sieve shaking machine for a `period of ve min- Autes'in-order to separate the original'flller roughly into fractions retained in the diierent testing sieVeS. This loperation is repeated, if necessary, in order `to obtain about to 200 grams lof Vthe .desired screen fraction, which fraction is then individually rescreened for i5 minutes, using the Ro Tap sieve shaking .machine or the `equivalent in `order to remove `any fines contained therein. The resulting screen fraction is the material that has passed the coarser .screen and is Lretaineolfon the finer screen. A
-v As aforesaid, it is essential that the thigh ow resistance coeiiicient be attained in a bituminous ,composition that does not exceed a predetermined lplasticity value at 400 F. The fire-resistant bituminous compositions of this invention fall within the narrow range wherein the iiow resistance coefficient exceeds the minimum .above mentioned, but .have a plasticity value at 400Y that does not exceed 150.0 grams and that preferably deesinotexceed 1009 grams. The Vplasticity value at 40.0 Roi? the bituminous composition described in the :exemplary lembodiment of this -invention is about 1125 grams.
The plasticity valueof the bituminous composition has lbeen determined by us, using -a VWagner- .Bowen -mixing vbowl plasticimeter, 'manufactured by E. E. W. Bowen, Bethesda, Maryland. `For testing bituminous compositions of the character .mentioned herein, `we lhave made certain modifications in this test apparatus. Inview of :this fact and .further :in view of the fact .that We do not know -of .any available publication wherein this type @zi-apparatus :is described in detail, we have show-n in .thedrawings, Fig. 18 to Fig. 23C, the testing apparatus iwrl'iich we have employed and a description of theapparatusand its operationI follows. -When reference is -made herein 'or in the claims tUWagner-Bowon plasticity value, the -plasticityvalue as determinedby'this testis intended.
The Wagner-Bowen pla'sticim'eterconsists of a suitable base |00 which comprises in housing |43 suitable gear means (not shown) for rotating the vertical shaft il by power supplied from the .motor |02. 'The shaft itl carries for rotation at the upper end thereof the horizontally-disposed disk-shaped support H13-to the top of which is .secured the bowl tod rby means of screws |65. By this arrangement, the bowl |04 can be rotated by' operation of the motor |02, vand any suitable means can be provided for maintaining the rotation of the bowl at a predetermined constant speed.
VEmanatingfrom the base |00 are'arms |66 and |65 which carry von the upper ends thereof "the crossv bar |01. At the upper end of each arm |05 19 and is a yoke |08 which is pivoted to'lug |09 and which is providedwith a thumb screw I I0 in threaded engagement therewith so that, by loosening the thumb screw I I0, the yoke |08 can be swung outwardly, permitting removal of the cross bar |01. At each end of the cross bar |01 is a positioning pin by which the position of the cross bar is determined.
The cross bar |01 carries the means determining the plasticity of material in the bowl I 04. Carried at the lower end of shaft |I2 is the mixing blade I I3, the vertical positon of which relative to the bowl I 04 is adjustable by nuts II4 which secure the shaft |I2 to the cross bar |01. Adjacent the end of the mixing blade II3 is the thermometer I I5 carried in a guard I I6 attached to bracket I I 1 which in turn is secured at the upper end to the cross bar |01. Carried by the lower end of the shaft II8 is the smoothing blade ||9. The shaft |I8 and smoothing blade I|9 are urged downwardly by the expansion spring |20 between the annular washer I 22 and the sleeve I2I in which the shaft IIB is vertically slidable. The vertical position of the smoothing blade I I9 is determined by the thumb screw |23 which rests collar |28 is the arm |29 which carries the small cylindrical drag tool |30 at the lower end thereof. Carried by the upper end nf shaft |21 and rotatable therewith is the arm IftI, the outer end of which has a small amount of plav for angular movement with the shaft |21 between opposed adjustable stop screws |32.
A horizontally-disposed stub shaft I 33 is fixedly carried by arm |06' and pivotally mounted thereon is the T-shaped scale beam member comprising the vertically-extending arm v|34 and the arms |35 and |36 extending horizontallyv on opposite sides of the stub shaft |33. Pivotallv secured at the end of the arm |35 is the weight pan I 31 and pivotally secured at the end of arm |36 is the counterweight |38 which substantially counterbalances the weight pan about stub shaft |33. Between the end of arm 3| and the end of arm |34 is the tie rod |39. One end of the tie rod |39 has a turned-down portion |40 which slips through an opening of corresponding size in the end of arm 3| to provide pivotal movement with respect thereto. The other end of tie rod |39 is in threaded engagement with a yoke member |4| which is pivotally mounted with respect to the upper end of arm |34. If desired, a fixed stop arm |44 can be provided for convenience in restraining movement of arm |34 when the tie rod |39 is disengaged from arm I3I. The contents of the bowl |04 can be heated as by the gas burners |42.
In the operation of the plasticimeter, the bowl |04 is rotated in a clockwise direction, and, as the bowl continues to operate, the mixing blade ||3 scrapes the heated contents of the bowl away from the outside bottom portion thereof and the thermometer I|5 records the temperature of the contents of the bowl at this point. The contents of the mixing bowl'are next carried under the smoothing blade II9 which smooths the con- '20 tents of the bowl to a predetermined level above the outer portion of the bottom of the bowl.l The lower end of the rod |24 serves as a check to determine whether the smoothing blade ||9 is smoothing the contents of the mixing bowl to the desired level, and, if it is not, the vertical position of the smoothing blade I |9 is adjusted by thumb screw |23. The heated contents of the bowl at the predetermined desired level therein are then carried past the drag tool |30 and this tends to rotate the shaft |21 in a clockwise direction and to pull the weight pan |31 upwardly through the system of lever' arms and tie rod hereinabovedescribed. The greater the plasticity (i. e., the heavier the consistency) of the contents of the bowl |04, the greater will be the drag on the drag tool I 30 that tends to elevate the weight pan I 31. By placing Weights on the weight pan |31 and while continuing to rotate the bowl |04, the device can be brought into a state of equilibrium so that the end of the arm |3I will be approximately midway between stop screws |32-I32, and the weight in grams required to achieve this condition of equilibrium for a particular composition contained in the mixing bowl is the Wagner-Bowen plasticity value. This value is dependent upon the dimensions of the apparatus and the mannerjof use of the apparatus in making the determination. The essential dimensions of the apparatus shown in the drawings are:
a, 3% inches 134%; inches b, 9% inches s, 11,41 inches aa, 3% inches bb, 2% inches y', 2% inches 7c, 4% inch radius Z, lsinch radius cc, 3A inch m, iinch dd, 5/8 inch n, 2% inches ee, 1A inch o, 11% inches p, 2% inches q, 2312 inches ff, 24 15' angle gg, 5A; inch radius hh, I; inch The dimensions of the mixing blade |I3 and of the smoothing blade |I9 are indicated on the face of the drawings.
The Wagner-Bowen plasticity values at 400 F. given herein are determined in the following way. The height of the lower end of the measuring rod |24 from the bottom of the bowl |04 is adjusted so as to be 'V8 inch. The height o1' the bottom of the drag tool |30 from the bottom of the bowl is set so as to be 1/4 inch. The weight of the composition to be tested is approximately 1500 grams. The weight is not critical provided the thickness of the composition as it leaves the smoothing blade just clears the lower end of the measuring rod |24. 'I'he composition is mixed while in the bowl |04. Throughout the test the bowl |04 is rotated at the rate of 60 rotations per minute. The bitumen that is used in the composition while in a heat-liquefied convdition is poured into the bowl while the bowl is vall been incorporated. The smoothing blade II9 is then adjusted so that the composition as it leaves the smoothing blade just clears the lower .As mentioned above', 'it is .not essential ith'at fa mineral ber `filler 'such :asi'asbestos dustfbe included in the bituminous composition'.` :Thus
`thefasb'estos dustmay beromittedf'and'theiller may consist vonly oilimestone .'dust: or 'fslateioun :In such case, however,` a greater: 'percentage' of 'ller to bitumen iis required, .theacritical"value 'forV powdered limestone 'dust `usually being. 'fin .the neighborhood .of 7 5 ,tot80'% by'weight 'or lime'- 'stone .dust Ain the composition. .'Other: ller :material may. al'sobe used,ibut the criticalfamount -differszin the case of .'eachlller'. :In tthe'lcaseoi each ller, :th'eeiiectof' attainingand 'exceeding I fa .critical valuehas been noted V'by usiforfupon `the addition of` any filler material',i.there isco'm- -paratively little 'eiectv .on 'ow resistance :'coei'- cientup to .the Ycritical point, followed fby a 'sud- -den and very great increase. in flow resistance coefficient as soon;asthe VcriticalV point'i's reached. 'Thusfor slate flour 85% by weight .(14,200) when yused'by itself ,'thezcritical pointiisfusually around v65% rby weight 1 of the :coating composition. In l the :case of silica 'our' '35 .by 'weight'. `A14200) the critical'point iszinkthe 'neighborhood of .'107,` by Weight. of the composition. Kaolinitic'type clays are also suitable.A 'Thus for' 'one .typerof kaolinitic type clayvv which 'is known .commercially as"Girard clayv v(produced.'byrzUnited. Cl'ay Mines Corp., Trenton, New Jersey),.the .critical value vis Yusually Aaround k60%I .by weight vof 'the composition, while for another'type ofkaolinitic type clay which Tis' sold Vunder-the.name 5I!ako" v(produced. icy-Thomas Alabama KaolinfColl, the
critical. point' is usually 'somewhat higher, that "is, around 65%' by weight of the composition. .E'orfone varietyrof talc, the-'critical value-isfabout '70% by weight of' 'the composition. In connection with the foregoing, it may' beiapointed out that the Vfigures above given 'as to critical percentages are .subj ect '.to- 'slight vvariation due to the fact thatV the criticalpercentage fforf a 'given iiller will vary somewhat, kdepending Iupon the manner ofgrinding the'lfiller'to ar-pulVer-ulent condition, thefch'aracter' lof the bitumen with which it Ais' mixed, and the thoroughnessoilthe mixing. However, from thelforegoing,fit'is zsip-- parent that Athere is a critical point'at which for a given iiller-bitumen composition there is 'the sudden `and very great'increasein flow resistance Cri coeiilcient. There 'are a numberno'f` other 'ller Ym'i'tted maximum plasticity value for' Work-a- Also filler mixtures of" variousV 22 bilityiis..:exceer'led.beforewtheircritical-.owfresistb ance; icoeflicientis attained, fand, .if "a particular ii'ller zis'.'of;this character, then such'v filler; mater- `rial .may "not satisfactorily be employed. How'- ever, inithc case .of those :llers which', Withinthe permittediimitof plasticity'value, may beg-added toJobtainthe highow resistance'coefcientaabove mentioned, any iiller in .theiorm of 'finely-divided solid `water-insoluble .heat-.resistant` mineral ifiller may be. employed. By heat-resistant.any'ma- .teria-lisintended which issufiiciently 'heatf-.resisti- .ant 'so Athat it4 will retain *structural integrity when subjected to. ame. temperature .whi'leinf .corporated in; the. roofing.. In. this connection, substances such .as ,chrysotile asbestos, ACanadian -picrolita .hydratedPortland cement.: eter.. .are fregardedas .heatf'resistant even. though-.zthey .contain-:water of 4constitution "which mayfibe drivenY oli at temperatures at 'or below' '.'flame temperatures. .In connectionjwiththe foregoing, it may be pointed .out that the WagnereBowen plasticity value and the` .ow resistance coieicient are diierent' 'properties .that 'aregnot .'afiected proportionally'by increasing theiiamolm of'-lller in'abituminous composition..
As mentioned above, Vit isgdesirable .torzinclud .in the Ybituminous composition as i at .least 'part off 'thegller material a finely-divided 'mineral ber` such as' asbestos, 'the particles; of Whichgare such as to'pass'a 6 mesh-standard .testingsieve .fand'befretained on 1a200 mesh .standard testing sieve. Also asxaforesaid, 'such brous'ininerals .includefractions that, when used 'by-themselves and. in 'amounts `lesstthan 55% by" Weighti .of 'the composition, afford. a jow-'resistance coei'lcient The term mineral Wool includes variou s fibrous- .products obtained by attenuating. into .fibrous 'form suitablefused materials .such-.asrock orslagg.
Another suitable fibrous material` is :a 'comminuted .mixture ofr hydrated Portland cement andv asbestos iiber, the hydrated Portland'cement `having become set with the asbestos fiber distributed therethrough. .A convenient *source of 'such material is asbestos-cement rooiin'gfscrap. Asbestos-cement rooiing scrap Vusually contains about 20% to 35% by weight-of asbestos 'fiber -and' about 65% to 80% by weight of .hydrated Portland cement. Heretofore such scrapha'sbeen yregarded as unavoidable waste of nov commercial value. However, by' subjecting the scrap to `a ldisintegiator, .such 'as .a hammer 'mill 'until'the .particlesize Lis of the order oftliat mentioned vin connection with asbestos fibers, 'the resulting `mass'contains a multiplicity ofrthashort asbestos `fibers to which the hydrated-Portlandzcement'ad- `lieresas nodules, andfor this reason this vmat-erial is essentially a .iibrous 'material .and-is to bere- .garded' as va:nicely-divided iibrousjniineral iiller.. v Anotherzmaterialiwhichis.somewhatsimilar'to lasbestos-'cement .in .that .the imaterial contains mineral .fibers together with .iioniibrous ima- :terial vis .disintegrated ber-bearing serpentine rock. Since :disintegrated fibers-'bearing serpenltinelzrocklcontains fibrous. particles, ysuch' .disine .tegrateidiserpentinerock is regarded asfon'e .form of fibrous mineral'which is suitable for use practicing- 'this invention. However, :depending upon the -physical structure and fibrous-mineral contento! the particular serpentine rock -.that -.i`s used, the proportionbf fiber contained therein is subjectl to some variation, but, as pointed'out below, this merely has the effect of varying somewhat the screen factors of the various screen gradings of the disintegrated serpentine rock as calculated to chrysotile asbestos dust of the screen'grading (-28-i-35) which has a screen factor 'of unity. Moreover, disintegrated serpentine rock is of such character, that in order to liberate the fibrous material contained therein it should pass a 20 mesh testing sieve, and, when reference is made herein to disintegrated fiberbearing serpentine rock, only that serpentine rock which has been disintegrated so that it passes a 20 mesh testing sieve is intended, since the individual particles of such coarser gradings Yare not fibrous in character but granular (are not fibrous mineral as this term is used herein) and since such coarser gradings are ineffective in producing highly nre-resistant roongs.
With regard to the fibrous mineral materials other than asbestiform mineral fibers, it is not necessarily the case that a particular screen grade of, for example, asbestos-cement or mineral wool, ywill have the same screen factor as that of chrysotile asbestos fiber. In fact, even as between different types of asbestiform inineral fiber, there are some variations in this regard. However, utilizing chrysotile asbestos ber as the standard, chrysotile asbestosv fiber of the screen grading (-28-1-35) having a value of unity, the screen factor of the screen gradings of the different fibrous minerals is determinable in the saine Way that the screen factor of each of the various screen gradings of chrysotile asbestos ber is determinable as has been described hereinabove. For example, the screen factor of asbestos cement prepared from asbestos-cement roong scrap and of the screen grading (-28+35)'wil1 be about 3 as compared with the screen factor of unity for chrysotile asbestos fiber of the same screen grading. The screen factor of mixtures of iibrous minerals will bear a similar relationship to the screen factor of unity of chrysotile asbestos of the screen grading (-284-35) When a mixture of fibrous minerals is employed, it is preferable that all or at least a major proportion of the fibrous mineral be selected from asbestiform mineral fibers, disintegrated asbestos-cement, and disintegrated fiber-bearing serpentine rock.
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 approaching flame temperatures. The other asbestiform mineral bers are low in Water of constitution. Some of the non-fibrous ller materials likewise contain water of constitution that is liberatable at or adjacent flame temperatures. Thus kaoli'- nitic type clays, powdered serpentine rock, calcium silicate hydrate and hydrated Portland cement contain to 13% or more of water of constitution that is liberatable at or below flame temperatures, although impure clay may contain as low as 5% of water of constitution. When the iiller material contains water of constitution liberatable at or below flame temperature, the liberation of moisture causes the bituminous composition to develop pores to a greater extent than otherwise when the bituminous composition is exposed to ame temperatures and this is desirable since the pores tend to augment the heat insulating efficiency of the mat-like residue that Cil is formed upon exposure of the bituminous coatingY composition to fiame temperature.v It is desirable that the bituminous coating composition have incorporated therein a filler material containing water of constitution which water of constitution liberatable at or below flame temperature amounts to at least about 5% by weight of the coating composition.
In the selection of filler material for use in the highly fire-resistant bituminous composition of roofings embodying this invention, the materials such as powdered limestone, slate our, talc, silica flour, kaolinitic clays, and the like, may be employed in the state of subdivision in which they ordinarily occur on the market. The bulk of such materials will pass a 200 mesh testing sieve, and it is preferable that at least by weight of the non-fibrous mineral filler material pass a mesh testing sieve. It is ordinarily desirable that the coating composition contain less than about 10% by weight of the total filler in the bituminous composition of granular particles of non-fibrous nller that'are retained on a 14 mesh testing sieve. Referring to the filler as a whole, including possible presence of mineral fiber ller, it is desirable that at least half by weight of the mineral filler pass a 100 mesh testing sieve, and preferably at least 2/3 by weight of the total filler material should pass a 100 mesh testing sieve. As aforesaid, the critical point at which the great increase in fiow resistance value is attained will vary depending somewhat upon the state of subdivision of the filler material, but it is not regarded as necessary herein to prescribe exact limits as to particle size, since proper particle size is inherent provided the filler in question, when incorporated with the bitumen of the bituminous composition, has a f'low resistance coefficient above the minimum hereinabove given and provided the composition has a Wagner-Bowen plasticity value not above the maximum hereinabove given. The Wagner-Bowen maximum plasticity limit also precludes the employment in the composition of an'excessive amount of fibrous mineral material of the coarser screen gradings, since the presence of fiber of substantial length greatly increases the Wagner-Bowen plasticity value. It may be mentioned, however, that such mineral fibers that come up within the grade of asbestos known as fiber according to the classification of the Quebec Asbestos Producers Association and which are the type in general commercial use are undesirable for use in bituminous coating compositions according to this invention. Thus such fibers tend to become entangled in clumps or clots which result in non-uniform distribution so that'the coating istoo irregular to be commercially acceptable, the fire resistance is impaired due to poor adhesion to the base sheet and zones of inadequate protection, the weather resistance is impaired due to zones of inadequate coverage of the base sheet and the like. It is of great practical importance that the fire-resistant coating compositions of this invention are spreadable, that is, can be readily prepared and applied with the production of a good waterproof coating of uniform thickness and consistency and of long weathering life using ordinary roofing machines. The above-mentioned limits as to Wagner-Bowen plasticity-Value of the bituminous coating compositions of this invention insure good spreadability; It is ordinarily desirable, for reasons above mentioned, that the ratio of the grading index of the fibrous `mineral to the percent by weight of 'bitumen in the composition be not 25;? greater than about 1` to..'7.and preferablynot greater thanabout'l'sto l-.` i
ALWith regard .to the bitumen .that 'is employed in the special fire-resistant bituminous:composi-Y tion, it is usually preferable to employ an asphalty Vhaving a softening point of about 180 F. to about Vferred to herein are determined by '.thestandard ring and ballsofteningpoint 'test The 4amount of bitumen,` depending upon theA criticalv point 'for the filler that isused, will -be`lbetween'fabout'v20 and v'45% by weightloff the bituminouscompo'-` sition -(the amount of ller runningifrom-55% to about 80% by weight ofthe-bituminous composition). In addition to asphalts 'derived from Mid-Continent crudes, asphalts from Mexican, Venezuelan and Colombian'crudes are also suitable. Moreover, other bitumens suchas pitches, coal tar and the like may also be used in thepractice of this invention. While it-has been mentioned that the ow resistance coefcient of a filler is usually somewhat higherin -the'case of cracked asphalts as compared with other asphaltic materials, cracked as'phalts do not have as long weathering life, and for this =reasonfit is usually 'preferable to use ,thel usual type 'of roofing asphalt for direct exposure to` sun'r and iweather.
In the foregoing example of the practice vof the invention, the special bituminous coating' material was applied at the rate of 45-pounds per 100v square feet of the frooiing; It is usually desirable to apply the'special;coatingjcomposition to the weather side of the base 'sheet so that the coating layer will weighabout 20 to, about 60 pounds per 100 square feet, although .about 30 to 50 pounds per 100 square feetisusually preferable. In the foregoing example wherein the special bituminous coating contained substantially 68% of ller and the-'coating was applied at 'the rate of 45 'pounds per 100'square feet, the amount of filler in the coating composition constituted about l30 pounds per 100v square feet of the roofingv material. For prepared roofing materials, it is usually desirable-that th'e roofingmaterial contain in one or more-layers such as a surface layer or a backing ,or vother layer, sufcient of the special bituminous coating composition'. so that the roofing material will containv at least and preferably 22 pounds per 100l square feet of the filler material.y By Varying the number and thickness of the layers of special bituminous coating composition in a prepared roofing' `rmaterial or in aroof covering, `varying degrees of fire-retardant effectiveness cantbeattai'ned. The special bituminous composition of this invention is especially'effective when "it ,is disposedin a roofing" so as to occur in a plurality ofv layers separated by.: feNJOr!y other sheet material, for example, as shown in Figs@ and 4 or as shown in Figs. 7 and 8. In such plural'layer'construction, it is preferable that each of at least two of the layers of special bituminous composition contain at least about 1l pounds per 100 square feet and preferably pounds per 100 square feet of the heat-resistant ller material, and that the roof covering as a whole contain at least 22 pounds per 100 square feet and preferably 40 pounds per 100 square feet of the heat-resistant ller material.
Roongs comprising a plurality of layers of the special bituminous coating composition need not necessarily be assembled on the `job but maybe preformedV at the factory.` Such Va multilayer. roofing is illustrated in Fig. 10...?1'Ihis roofingl material'contains .three layers of asphalt im# pregnated felt. Between the layers of felt are layers 8l ofthe special bituminous coating composition. In addition, there is a surfaceY layer 82 of the special .bituminous coating composition. The felt layers may, if desired, be composed of asbestos liber; but,instead of asbestos fiber felt, ordinary organic fiberfelt may be used, since the specialcoating composition of this invention in itself affords highre resistance. The top vlayerv 82 may, if desired, be omitted.- f 1 While felt sheet material has been mentioned hereinabove as the 'strain-resisting element of' roofing Aand roofing structures embodying this invention, it is apparent that any other-suitable sheet material either fibrous or non-fibrous, either foraminous or non-foraminous'adapted to afford desired strength characteristics may be employed.v Thus fabrics other than felt may be employed, such as woven fabrics or'fabrics of unspun bonded fibers. lThe base sheet'may, if desired, be saturated withy a waterproon'g'mae terial or may--bedryv Sheet material such as composition boardl or insulation material may be employed.' Plain or corrugated or indented sheet metal may also be used as the basesheet. Ordinary roofing'ffelt made of organic/fibers is,` however, the most inexpensive sheet material, and notwithstanding the combustibility ofsuch sheet material, roofing' comprising it can, `according to this invention, be made highly nre-resistant. If desired, non-combustible fibers 'can be incorporated in the felt'or other fibrous base sheet to augment the reresistance of the roong.
It is one of the advantages of thisV invention thatthe new roofing herein defined possesses high re resistance without sacrice of other properties required for a roongfand without substantial increase in cost compared with conventional rooiings heretofore manufactured. The
- new` roofing of'this invention "has very good weatheringcharacteristics and -is tough and pliable; Thus a typical preformed roongmaterial'such asav shingle can bebent 180 in two seconds around a 4fcen'timeter mandrel with the fire-'resistant special coating composition on the outsidewithou't cracking the coating through tothe felt base,l thev test being rmade at 77 F. It is'desirable' that a roofing `having a bituminous waterproofing. coating be sufficiently pliable to be bent intwo seconds about'a mandrel 10 centimeters in diameter at '77 F. with the coating on the outsidewithout cracking the coating through to the base on which it is applied, and any lsuch coating or layer is referred to herein' as pliable at ordinary temperatures. In our aforesaid application Serial No. 399,024, 'we havedisclosedI that the problem vof the blistering ofroofings can be 'met-'by effecting a great increasei'n the viscosity and strength of the-bituminous coatingA composition and have claimed such highly blister-resistant roongs wherein the bituminous coating layer contains at least 45% by weight of bitumen. The highly mineralized coatingsof the present invention, which contain less than 45% by weight of bitumen, can be made with the high viscosity and strength characteristics requisite for minimizing blistering but, in order to do so, the softening point of the bitumen should be above 200 F. For purposes of brevity, reference is made herein to the specification of our said application, Ser. No. 399,024 as though'the same were set forth herein. Those'properties given in our aforesaid application as definitive of highly blister-resistant bituminous coatings are that the bituminous coating composition have a softening point above 300 F., have a viscosity at 170 F. greater than 4 107 poises, and have a tensile strength at 170 F. of atleast 150 gm. per sq. cm. For a suitable roofing, 'the coating composition also should have a work capacitance at 77"` F. of at least 2000 gm.cm. per cu. cm. and a per cent. elongation at 77 F. of at least-35. The filler should have a preferential ainity for the bitumen in the composition as against water at 185 F. Preferably, the viscosity at 170 F. of the highly blister-resistant'bituminous composition is at least 20 10rl poises. The measurement and significance of these properties is fully explained in our aforesaid application Ser, No. 399,024. The bituminous coating layer should, in order to provide high blister resistance, be applied at the rate of at least about 20 pounds per 100 square feet. l a
While this invention has been described in connection with certain illustrative embodiments thereof, it is to be understood that this has been done. for the purpose ofexemplication. Accordingly, the scope of this invention is to be governed the language of the following claims construed inthe light of the foregoing description of our invention.
We claim: I,
1. A roofing having high reresistance and high blister resistance comprising sheet-like base material and carried by said sheet-like `base material a waterproofing layer of thermoplastic bituminous* composition, said bituminous composition containing bitumen having a softening point above 200 Ffand not above 275 F. and ofthe range-between 20% and 45% by weight of said ubituminous composition, said bituminous composition containing intimately commingled and distributed uniformly throughout finely-divided solid water-insolublev heat-resistant mineral filler of the range above 5,5% tov80% by weight o f saidmcomposition which has a preferential affinity for said bitumen as against'fwater -at 185 F., said bituminous compositionhaving---a Wagner-Bowen plasticity'value at 400 5F. not greater` than 1500 grams, Yhaving a softening point above 300 F., having a viscosityat170 F. greater than 4x107 *poises, having Ia tensile strength at'170 F.of atleast 150gmfperrsq. cm., having -a -per cent. velongation-at 77-F. of at least 35, and having -a Work capacitance at 77v F. of at least 2000 gm. cm. per cu. cm.,'jthe said filler contained in said bituminous composition having a iiow resistance coefhcient of at least475 when saidjcomposition carried `by' said sheet-like base material is exposed to name temperature under the `flow resistance testas defined herein, and saidbituminous composition providing a pliable weather-resistant layer of the hot-spread coating type Which is integrally bonded with said Vsheet-like base material and is ofa thickness throughout not less than corresponding to about 20 pounds per 10,0 square feet throughout the extent of said layerwhere said layeris designed to provide, blisterfresistance.
2. A roofingmaterial having -high resistance to fire and; high blister resistance comprisinga sheet-like base material and 'carried by said sheet-likebase material a waterprooiing layer of thermoplastic bituminous composition, said bituminous composition containing bitumen having a softening point above 200 F. and not above 275 F. and of therange between 20% and 45% by Weight of said composition, and said bituminous composition containing intimately com mingled and ldistributed uniformly throughout finely-divided solid water-insoluble heat-resistant mineral'filler of the range above 55% to by Weight-of said composition which has a preferential affinity for said-bitumen as against waterat 185 F., said bituminous composition having a Wagner-Bowen plasticity value at 400 F. which is substantially greater than 250 grams and which is not greater than 1500 grams, having a softening point above 300 vF.. having a viscosity at 170 F. of at least 2f0 107 poises, having a tensile strength at 170 F. of at least gm. per sq. om., and having a work capacitance at 77 F. of at least 2000 gm. -cm. per cu. cm., the said ller contained in said bituminous composition having a flow resistance coefficient of at least 75 when said composition carried by said sheet-like base material is exposed toame temperature under the now resistance test defined herein, and-said layer being of the' hot-spread coating type integrally bondedwith said sheet-like base material and being applied to said sheet-like base material at a rate such that the thickness corresponds to about 20 pounds to about 60 pounds per 100 square feet of 'said roofing material and said roofing materialbeingpliablev at 77 F.
HAROLD W. GREIDER. GEORGE ARTHUR FASOLD.
' REFERENCES CITED The following references arel of record -in the file of `this patent: Y
UNITED STATES PATENTS OTHER REFERENCES 'Petroleum `zietscim'ft, v01. XXIX, Nr. 45 (1933),' pp. 1-12.