US2718479A

US2718479A - Asphalt coated sheet

Info

Publication number: US2718479A
Application number: US60273A
Authority: US
Inventors: Lester A Bierly
Original assignee: Presque Isles Lab & Manufacturing Inc
Current assignee: Presque Isles Lab & Manufacturing Inc; Presque Isles Laboratories & Manufacturing Inc
Priority date: 1948-11-16
Filing date: 1948-11-16
Publication date: 1955-09-20
Anticipated expiration: 1972-09-20

Description

Sept. 20, 1955 A. BIERLY ASPHALT COATED SHEET Filed Nov. 16, 1948 Y M w x M W,

IN V EN TOR.

Isl 4 2,718,479 Patented Sept. 20, 1955 ASPHALT COATED SHEET Lester A. Bierly, Chautauqua, N. Y., assignor to Presque Isles Laboratories & Manufacturing, Inc., Erie, Pa., a corporation of Pennsylvania Application November 16, 1948, Serial No. 60,273

2 Claims. (Cl. 117-168) This application is a continuation in part of my application, S. N. 6,017, filed February 3, 1948, and now abandoned.

This invention is intended to increase the fire resistance of asphalt compositions or of articles containing, or coated with, asphalt compositions. One use is in asphalt shingles or roofing where it is possible to so increase the fire resistance as to obtain a class A rating as described in Patents 2,326,723, Fasold et al.; 2,326,724, Fasold et al.; and 2,424,234, Greider et al. Another use is in asphalt coated paper where it is possible to make a paper which is self-extinguishing in the sense that it will burn only in the immediate presence of an externally created flame. The fire resistance is obtained from materials which, in the presence of flame, react with the burning or heated asphalt to produce a foamy porous mass having a bl'i'sterl'ike crust serving as a thermal insulator and as a mechanical stabilizer holding the asphalt in place. Materials having this property in various degrees of effectiveness are glass wool, rock wool, asbestos, hydrated lime, mixtures of hydrated lime and mineral fillers, and chlorinated paraflin. Chl'orinated paraflin, in addition, has the property of releasing chlorides which have a snufiing action on the flame. Further objects and advantages appear in the specification and claims.

In, the drawing, Figs. 1 and 2 are sections through a.

built; up and shingle roofs having felt impregnated or coated with an asphalt composition embodying my invention; Fig. 3 is a section through an asphalt coatedpaper;

Fig. 4 is a section through an asphalt tile, and Figs. 5 and 6 are sections through a glass fiber base shingle.

In Fig. 1' is shown a typical type of built up roof in.

3 indicates layers of asphalt impregnated roofing felt; .4. indicates layers of mopping asphalt, and S'indicates'the surfacing mineral granules, e. g., slate or ceramic granul'es. Except for the layers ofmopping asphalt, which.

will' be hereinafter described, the roofing is, ormay be, of common construction.

In, Fig. 2 is shown a typical asphalt shingle roof in which 6 indicates the roofing boards to which. are applied asphalt shingles having aLlayer. 7 of. asphalt impregnated felt, a layer 8 of flexible asphalt coating composition, and a surfacing layer 9 of mineral or ceramic. granules. Except for the flexible asphalt coating composition. the roof, is, or,may be, of common construction.

As. explained. in. the. Fasold et. al.. and. Greider' et al. patents, the. common. constructions. ofasphalt built up or shingled. roofs satisfactorily pass the tests of the Underwriters Laboratories, Inc. for aclass C*rating and fail topassthe-moresevereclass A'and class "B tests which are reserved for highlyfire resistant'roofs such as slator asbestos cement shingles; or for built up roofs having a very heavy mineral surface'coating. These patents describe particular asphalt coating.com-

positions which enables the built up and shingled roofs to pass the class A or class B tests.

The present invention uses an improved mopping asphalt or flexible asphalt coating composition which likewise has sufficient fire resistance to enable the roofing to pass the class A and class B tests. The

- asphalt composition (usable as a mopping asphalt in the built up roofing and as a flexible asphalt coating or impregnating composition in the shingle roofing) comprises any of the commercially used flexible coating asphalts which ordinarily have a softening temperature 'in' the region of 225 F. but may have a wide range of serves as a: heat insulator for the layers of asphalt comsoftening points, e. g., 125-300 F. to which has been added dried sludge resulting from the manufacture of soda ash by the Solvay Process. This sludge has the following chemical composition:

- Per cent CaCOa 60.0

Ca(OH)2 29.3

CaSO4 2.21 CaCla 1.16 Mg(OH)2 I 1.9

FeaOzplus A120 1.1

SiOz 1.9

NaCl 0.64

It is believed that the active ingredients in this sludge which impart the fire resisting properties are derived from the hydrated lime (Ca(OI-I)2 and Mg(OH)2). The hydrated lime is a material which is substantially increasedin volume (from 1.7 to 3.3 times) by the water of composition added during hydration. The water ofcomposition of the calcium hydroxide is rapidly released at the temperature of 1076 F. The water of composition of magnesium hydroxide is rapidly released at a temperature of 662 F. Both of these temperatunes are below flame temperatures used in the Underwriters tests. The portion of the asphalt coating in contact with: the'fl'am'e breaks down the hydrated calcium. and magnesium oxides. The release of the water of. composition produces a foaming action on the heated or. burning asphalt, resulting in a cellular structure which position n'otf in contact with the flame. The cellular on porous" structure is further increased by the expulsion of? thewater'of composition caused by decomposition at flame temperatures from the molecules of hydrated oxidesof calcium-'- and m'a'gnesium. Both of these oxides have the-property of substantially increasing in physical volume upon hydration so that upon de-hydration a porous. structure results.

Anotherirnportant property'of the hydrated oxides of .calciurni and magnesium is the reduction in viscosity of the asphalt coating composition. For example, the substitutionf in. the preferred flexible asphalt shingle coating composition, based upon the disclosure of the Fasold et al and' 'Greider et'al. patents, 0f 50% (byweight) dried sludge for 50% (by weight)'of the fibrous asbestos dust results. iir a lowering of the Wagner-Bowen plasticity value, as-disclosed in'Greider et'al. patent, No. 2,424,234,

from approximately 300 grams to approximately grams? This reduction in Viscosity may permit pumping of the asphalt composition sincethe Fasold et al. and

Greider-I et al; compositions-are too stiff for pumping and must be spread. This reduction in viscosity does not affect: the fire resisting properties, although the teachings of the Fasoldetal. and Greider et al. patents" would indioate that .a reduction in-viscosity would decrease the fire resistance.

' The-other-ingredients-in the sludge'are not believed to cienbfire resisting .effect. Possiblythis is due to the high temperature at which the calcium carbonate breaks down, and to the slowness of break down at this elevated temperature. Furthermore, the carbon dioxide released upon break down is less effective in producing or causing foaming of the asphalt. The calcium chloride in the dried sludge does not contain any water, and if it did contain any Water, the water would be released at the application of temperatures of 400500 F. The calcium sulphate likewise has its water of composition released prior to the application of the coating to the roofing. The silicon dioxide, sodium chloride, iron oxide and aluminum oxide are not believed to have any substantial effect in increasing the fire resistance, either due to the properties of the material or to the small amounts present.

The fire resisting properties of roofing having an asphalt coating composition containing hydrated lime (hydrated calcium oxide and magnesium oxide) has been demonstrated in a comparative test run between asphalt shingles constructed in accordance with the preferred teachings of the Fasold et al. and Greider et al. patents in which the flexible asphalt coating composition applied to the asphalt impregnated felt consisted of blown asphalt having a softening temperature in the range of 220-240 F., in which is mixed from 3550% by weight of fibrous asbestos dust. In the first test an equal Weight of dried sludge was substituted for one half of the preferred Fasold and Greider asbestos dust. In the second test all of the Fasold and Greider asbestos dust was omitted and an equal weight of dried sludge substituted in its place. These shingles were subjected to a torch test, determined to be equivalent to the Underwriters class A test. In the torch test the shingle (with or without surface granules) is placed at an angle of 30 degrees to the horizontal and an oxyacetylene flame, having a temperature of approximately 2000 F. is positioned at right angles to the shingle so that the tip of the blue-white cone of the flame touches, or is in contact with, the shingle. If the flame does not burn through the shingle in two minutes, the shingle will successfully pass the Underwriters class A tests described in the Fasold and Greider patents. The torch test is, in effect, an accelerated class A test. Asphalt shingles of five well-known manufacturers failed in the torch test in from 30 to 55 seconds. Both of the shingles containing the dried sludge passed the test. The shingle containing half sludge was indistinguishable from the Fasold and Greider shingle. The shingle containing no asbestos dust exhibited a tendency for the asphalt coating composition to run off the shingle, indicating that a small amount of anchoring eifect obtained from the asbestos, glass wool, rock wool or any other incombustible fibers are desirable. The shingle containing 100% of sludge however did pass the test although there was a tendency for the asphalt to slide. The sludge containing asphalt coating composition had a substantially lower viscosity at the application temperature of 400-500 R,

which made the coating easier to apply.

The behavior of the sludge or hydrated lime containing asphalt coating composition in the presence of a flame is such as to protect the roof boards from combustion. The asphalt composition in immediate contact with the flame burns and produces a fluffy or foamy mass which serves as a thermal insulator, protecting the lower layers and roofing boards from the flame. After removal of the flame the asphalt burns for from one half to two minutes and then dies out. The burning of the asphalt is sufficiently confined to the immediate region of the flame so that the shingles satisfy the class A Underwriters test.

The burning of the asphalt composition in the presence of the flame results in the formation of an outer crust which, although it may become red hot, is sufliciently separated or spaced from the lower layers of the roofing as to prevent or retard the transmission of the flame.

The following are examples of flexible asphalt coating compositions all using commercial asphalt having a softening point of 225 F. (all percentages by weight) which produce roll or shingle roofing passing the Underwriters class A tests:

(impregnating Owens-Corning glass fiber cyclone mat) 3. Asphalt 70 Glass fibers 30 4. Asphalt 70 Sludge 10 Sand 15 Glass fibers 5 5. Asphalt 70 Rock wool 30 6. Asphalt Sludge 15 Sand 15 Glass fibers 5 7. Asphalt 65 Sand l5 Hydrated lime 15 Glass fibers 5 8. Asphalt 60 Sludge 25.7 Rock wool 14.3 9. Asphalt 60 Sludge 15 Sand 20 Glass fibers 5 10. Asphalt 58.8 Sludge 11.8 Glass fibers 29.4

11. Asphalt 58.8 Sludge 11.8 Asbestos (fine fibers) 29.4

12. Asphalt 57 Sludge 28.75 Asbestos fibers 14.25

13. Asphalt 55 Glass fibers 16.6 Limestone dust 28.4

14. Asphalt 55 Sludge 40 Rock wool 5 Asphalt 53.4 Sludge 40 Glass fibers 6.6

16. Asphalt 53.4 Glass fibers 6.6 Limestone dust 40 17. Asphalt 53.4

Sludge 40 Asbestos (long fibers) 6.6

18. Asphalt 50 Sludge 5O 19. Asphalt 50 Sludge 30 Glass fibers 20 (base, glass fiber pipe wrap) 20. Asphalt 50 Sludge 40 Rock wool 10 21. Asphalt 50 Sludge 20 Sand 25 Rock wool- 5 22. Asphalt a 50 Glass fibers" l0 Limestone dust 4O 23. Asphalt 47 Sludge 23.5 Sand 24.8

Asbestos fiber 4.7

Per cent 24. Asphalt 44.5 Sand 27.7 Asbestos fiber; 5.5 Hydrated lime 22.3 25. Asphalt 44.5 Sludge 22.3 Sand 27.7 Asbestos fiber 5.5 26. Asphalt 44.5 Sand 27.7 Asbestos fiber 5.5 Limestone dust 22.3 27. Asphalt 43.5 Sand 43.5 Glass fiber 2.2 70% chlorinated parafiin 10.8

In all of the examples using asbestos fiber the length of fiber was immaterial. The minimum amount of asbestos fiber was substantially as effective as greater amounts, and apparently had only a physical anchoring effect. Fibers which fuse together at flame temperatures (glass or rock wool) are more effective than asbestos fibers. The fused matted fibers form a harder crust having greater physical strength and superior heat resistance. The glass or rock wool fibers should be long enough to have a felting effect. For flat or slightly pitched roofs, no fiber is necessary.

The examples are subject to modification due to differences in the softening point of the asphalt, the term used in this application to designate asphalt derived from pe troleum, natural asphalt, pitch, coal tar, and other similar bituminous material. The asphalt having lower softening points require a greater percentage of fire resistant material while the asphalt having higher softening points require less fire resistant material. i

The fire resisting properties appear to be due to:

1. A physical anchoring effect which prevents running of the asphalt and thereby limits the spreading of the ha m'- e h hr ps h h hh-hhmh ht b e m ne l matter 9l F h ha t h s rs h hs h vo me o ksl lhhls ih 1F 2 ???w hihh am an also. Serves asa barrier between particles of asphalt.

3. The formation by the fire resistant material. of a porous mass having a blister-like coating which serves as a thermal insulator.

The physical anchoring effect is imparted by the fibers h as sbe tos 81 $$WQL hh W 0 e he greater effectiveness of. the glass androck wool is due to the fact that these fibers fuse in the presence of flameand produce a h hihhlly tron r st h blistr wh hhmor c eqtivsly tsx t sshs at of the heme Bsh h f the increased, physical strength of the blister, the, brand or source of the flame is better supported or, heldaway from, or, above, the underlying shinglesand roofing boards. The asbestos fibers do not fuse, but merely lose mechanical strength under the effect of flame. All of the ingredients of the composition, being inorganic or mineral matter, hhthh t h h and, e e o sdhse h ahwhh f asphalt which can burn in the presence of flame This property alone is insufficient to impart sufficient fire resistance to pass the class A Underwriters test. For example, sand and limestone dust, two of the commonly used fi llersfoi' asphalt shingles and roofing, have little fire resistance when used alone. The porosity of the blistenlike mass inicontact with the flame is due inpart tot he fusing of the glass or rock wool fibers, in part to the breaking down of the hydrated lime, releasing its water of. composition by decomposition, and in part to the breaking down of the asbestos fibers (if the fibers havewater of-constitution) The porous blister-like mass formed by the, hydrated lime alsohas an anchoring effect on the asphalt; in, addition. to the. heat insulating or, shielding effect. Chlorinated paraffin in the presence of flame re.- acts with the asphalt to produce a foamy mass which has a pronounced heat shielding effect and at the same time there is a release of chlorides which have a snuffing action on the flame so the asphalt is self-extinguishing in the sense that it will burn only in the presence of an externally created flame. This reaction of chlorinated paraffin takes place at temperatures of from 350-450 F. and even at these temperatures there is a permanent chemical and physical change in the asphalt which prevents the return of the foamy mass to the liquid or solid state upon cooling. The reaction of chlorinated paraflin is different from the reaction of other chlorinated hydrocarbons such as chlorinated naphthalene. In the presence of flame, an asphaltwchlorinated naphthalene mixture becomes very liquid, has little or no bubble formation, and apparently has no reaction with the asphalt even though the chlorides released by the naphthalene do have a snufling action on the flame. The heat shielding effect is a property peculiar to chlorinated paraflin.

In Example 2, the asphalt with 30% sludge filler impregnates a glass fiber felt base 10 producing the shingle illustrated in Fig. 5. In the manufacture of this shingle a sheet of glass Wool (or asbestos or rock wool) felt having a thickness about 50% greater than the finished shingle thickness and a weight of l0-20% of the finished shingle is dipped in asphalt composition and then passed through rolls which squeeze out the excess asphalt. Because the felt is loose or open the asphalt and mineral filler penetrates uniformly and after passing through the squeezing rolls, the. fibers are uniformly dispersed throughout the shingle. This method of making shingles avoids the stiffening effect of fibers on'the asphalt. The addi tion of sand, sludge, limestone dust and other mineral fillers within the ranges disclosed does not materially increase the viscosity of the asphalt. However after the mineral filler has been added; the glass, rock wool, or abestos fibers rapidly stiffen the composition even, at temperatures in the range of 450-50091? By flowing the: hot asphalt composition into a glass, rock wool, oras-.. bestos felt, the. fluid asphalt composition readily penetrates the felt. An asphalt composition containing the; same percent fiber as the impregnated felt would be. much, stiffer and. harder to. handle. Flowing the asphalt composition into felt is. an easier way of producing a fiber containing. fire resistant coating. The asphalt content: of, the. impregnated felt may be in the range of 10-70% by weight of the impregnated felt.

The glass wool felt. impregnatedshingle has greatly superior mechanical strength and toughness, has a grip? ping or sealing action onnails, and has by far the greatest heat resistance of; any of theexamples. The porous. blister formed. in. the presence of the flame is-v very uniform and free from cracks and the v asphalt around the blister is substantially unaffected, While two minutes. under the torch; test" is sufficient for class A, this shingle. withstood 10 minutes and gave no indication that the torch could not: have been held much longer without failure, The use of mineral fillers in. the asphalt, while not necessary for heat. resistance, may be desirable to reduce costs, to. improve weather resistance, or for any of the reasons the roofing industry considers fillers desirable.

In Example 19, glass fiber pipe wrap 11, a. thin foraminous glass cloth, is substituted for the conventional asphalt impregnated. paper roofing felt producing the shingle illustrated in Fig. 6 in which the coating is indicated at 1-2. The pipe wrap results in a shingle having.

greater strength and lighter weight.

In Example 27, the shingles" are self-extinguishing in,

thedsense thatthe asphaltwill not support combustion except. in; the immediate presence of flame. The selfegctinguishing properties come from the chlorinated-paraffin The chlorinated paraffin also contributes to class A? fire resistance by causing a. violent foaming of the asphalt which serves as a thermal insulator if itismechanically stabilized or anchored by the incombustible fibers. The mineral filler (which may be any of the inert mineral fillers used in the shingle industry such as sand, slate flour, limestone dust, or active mineral fillers having heat resistant properties, such as sludge, hydrated lime, asbestos dust) gives some body to the foaming asphalt so that it is better able to support the weight of the brand used in the class A Underwriters test. It is not necessary that the mineral filler be of the sort capable of imparting fire resistance. The inert mineral fillers are equally satisfactory and usually cheaper. lf the mineral fillers are of the sort producing fire resistance, such as sludge, hydrated lime, chrysotile asbestos dust, the amount of chlorinated paraffin may be decreased. The heat resistant mineral fillers produce a foaming action and an excess of foaming action produces no beneficial result.

The fire resisting effect of the mineral filler is affected by the particle size in the sense that smaller particles have a greater surface than larger particles. Another factor is the adhesion between particles of filler. This effect is more pronounced in the case of fibrous particles having felting properties such as asbestos, and is still more pronounced in the case of particles which fuse together such as glass or rock wool fiber. The porosity of the particle at flame temperature is important both from the point of view of the interlocking action on the asphalt coating, and from the point of view of thermal insulation. Hydrated lime appears to be particularly effective in this respect. Hydrated lime, although soluble in water, does not tend to pick up moisture and develops its porosity at flame temperature. Any hydrated lime which becomes exposed during the weathering of the asphalt coating will tend to react with the carbon dioxide in the air and produce a protective skin of calcium carbonate.

The particle size of the dried sludge used in Examples 2, 4, 6, 8, 9, 10, 11, 12, 14, 15, 17, 18, 19, 20, 21, 22, and 25, is such that 99% passes a 50 mesh sieve, 95% passes a 100 mesh sieve, and 80% passes a 140 mesh sieve. It is very difiicult to get the dried sludge to go through a 200 mesh sieve as the sludge is light and fluffy and the particles tend to ball up and adhere to each other. Under transmitted light the sludge particles appear to be round and very uniform in size. The particles at room temperature are slippery and have the feel of hydrated lime.

The sand used in Examples 4, 6, 7, 9, 21, 23, 24, 26, and 27 was the sand such as that used in mixing cement. The sand alone did not impart the class A heat resistant properties, since some commercial shingles having from 40% to 50% sand filler in the asphalt coating only have class C fire resistance.

The limestone dust used in Examples 13, 16, 22, and 26 is a waste limestone material used in road building. This limestone dust contains a number of larger particles. Pulverized agricultural limestone, which has an average particle size finer than the limestone dust, is superior but neither form of limestone alone produces the class A heat resistant properties.

The chlorinated parafiin used in Example 27 preferably has a stabilizer which raises the break down temperature of the chlorinated paraffin above 350 F. It is desirable that the break down temperature of the chlorinated paraffin be at least 450 P. so that the chlorinated paraffin will not break down when the asphalt coating is heated for application to the roofing. Without stabilizers the chlorinated parafiin breaks down at about 300 F. to 350 F. and causes a foaming of the asphalt. Apparently this results in a permanent physical and chemical change, since the asphalt foam does not return to the solid or liquid state upon cooling and is substantially impossible to reheat as local hot spots set off the breakdown of the chlorinated paraffin into a progressive foam producing reaction. The action of the chlorinated parafiin is improved by the addition of antimony oxide which serves as a catalyst accelerating the breakdown and also as a flame retardant preventing after-glow due to the formation of antimony chloride, a heavy gas. rinated paraffin are well known. Sludge or powdered limestone act as stabilizers. Some other stabilizers are derivatives of ethylene oxide, propylene oxide, butylene oxide, phenyl ethylene oxide, tolyl ethylene oxide, diphenyl ethylene oxide, phenoxy propylene oxide, diethyl ethylene oxide, benzyl ethylene oxide, epichlorhydrin, glycide or its ethers, such as methyl-, ethyl-, propyl-, tolyl-, alpha or beta naphthyl-, also cyclopentene oxide, cyclohexene oxide; alkaline earth metal salts of aliphatic acids having from five to ten carbon atoms, of which strontium caprylate is an example; tetra aryl and alkyl substituted compounds of tin in which the alkyl or aryl groups have from four to twelve carbon atoms and of which tetra butyl tin, tetra phenyl tin, dibutyl diphenyl tin, and dibutyl tin dilaurate are examples.

As disclosed in Fasold et a1. Patents 2,326,723 and 2,326,724, it has been considered that the granule surface coating for shingles or roll roofing should be made from a flexible coating asphalt which is the term applied by the roofing industry to asphalts having a softening point in the range of over 160 F., and most commonly having a softening point in the region of 225 F. The flexible coating asphalt is not necessary. By increasing the mineral filler content class A fire resistance can be obtained when the shingle coating is made from lower softening point asphalts, known in the roofing industry as penetrating asphalt. These penetrating asphalts have softening points in the range of 160 F., and commonly have a softening point in the region of F. By mixing higher percentages of asbestos dust and the other mineral fillers disclosed in the Fasold and Greider patents, or the mineral fillers disclosed in this application, class A asphalt shingle coating can be made which have, in addition to the class A fire resistance, superior toughness and flexibility.

Examples of asphalt coating all using asphalt having a softening point of 125 F. are as follows:

Stabilizers for chlo- Per cent 28. Asphalt 41.2 Sludge 52.9 Glass fibers 5.9

29. Asphalt 38.4

Sludge 54 Glass fibers 7.6

30. Asphalt 70 (half 225 F. softening point asphalt, and half 125 F. softening point asphalt) Sludge 30 (impregnating Owens-Corning glass fiber cyclone mat) 31. Asphalt 70 Sludge 30 (impregnating Owens-Corning glass fiber cyclone mat) 32. Asphalt (125) 66% Asbestos fiber 33% (Passed A testdid not run at 212 F. on 30 incline (2 hours).)

33. Asphalt 57 Sludge 14 Asbestos 28 All of these shingles passed the class A torch test. In Examples 28, 29, 32, and 33 the coating was applied to the ordinary asphalt impregnated paper roofing felt commonly used in the roofing industry as a shingle base. In Examples 30 and 31 the glass fiber cyclone mat, a glass felt having a thickness somewhat greater than the finished shingle thickness, served both as the base and as the body of the shingle. It is apparent from these examples that the use of high softening point asphalt for shingle coatings is unnecessary. The lower softening point asphalts which have not been oxidized by blowing and which have lower viscosity and greater flexihllity. and are accordingly j to liaiidle, adaptable gle coating asphalt. The superior flexibility of the ower ,sortenia pp'int pehetratihg asphalt is a desirable property sinee t e shingles are easier to handle and less likely to crack when laid during cold Weather. I, a v e behavior of the shingles in Examples 28-33 under the "Ii tLes t Was siibs't'antially the same as iii the other shineswhich passed class A torch test. The i contact with the to hc flame burned and a dim was produced which se' eda's h Th S iis' i'n E a p w ich, cehtage of p enetrating hsp alt xhihi'ted the te c'y for the asphalt to run, Ht the class A fire resistance was not impaired. Unexpectedly. the penetrating asphalt did not prove to be inflammable than the coating asphalt to destroy the class A fire resistance. The si'ze of theblister intheregion of the torchfiame was not appreciably greater thanthe size of the'blister in the shingle using coating asphalt. The penetrating asphalt, due to its lower yiscosity, was appreciably easier to handlewhich is. an important manufacturing advantage. ,Another unexpected property ofthe penetrating edually a'sphaltco atingnwasits stability at roof temperatures.

The shingle of Example 32, when subjected to 212 F. for two. hours, showed, no tendency town. This means that the shingles having a penetrating asphalt coating will. be satisfactory since roof temperatures never reach While Fasold and Greider teach the use of coating asphalt, it has not been heretofore appreciated that a shingle coating could be made with a penetrating asphalt" having a softening point well below summer roof temperatures. With the mineral fillers disclosed in this application and the mineral fillers disclosed in Fasold et al. Patent 2,326,723, a class A fire resistant shingle coating can be made from penetrating asphalt" if the percentage of mineral filler is slightly increased. In the trade, the line of division between coating asphalt and penetrating asphalt is 160 F. Asphalts having a softening point above 160 F. are known as coating asphalts. Asphalts having a softening point below 160 F. are known as penetrating asphalts. Most commonly the coating asphalts" will have a softening point of 225 F. and the penetrating asphalts will have a softening point of 125 F.

In all of the examples, 1 through 33 inclusive, the shingles were tested inclined 30 to the horizontal as in the Underwriters class A test requirements. The asphalt coating was accordingly subjected to a gravity force tending to slide the coating from beneath the torch flame and to expose the base. In order to demonstrate the fire resisting effect of hydrated lime and sludge, the following tests were run with the shingles level so that there was no gravity force tending to slide the coating. These tests demonstrate the fire resistance of sludge and hydrated lime and eliminate the need for mechanical anchoring elfect. These tests were not run on the glass wool or fiber containing coatings because the fibers had suflicient mechanical anchoring etfect to hold the coatings in place upon the inclined shingle, and so long as the coating was held in place its fire resistance would be the same on the incline as on the horizontal.

In examples 34, 35, and 36, the coating was applied to standard asphalt impregnated paper felt used as a shingle base by the roofing industry. The asphalt was flexible bii'rn'ed through, indicating that the sludge and hydrated lime had sufiicient' fire resistance to give class A fire resistaitce, although the presence of some other materials to; mechanically anchor the coating in place is required. Iii Example 36, the hydrated lime content is approximately 6%, indicating that one gram of hydrated lime plus two grams of limestone is capable of imparting class A fire resistance to twelve grams of asphalt. Example 34 indicates that one gram of hydrated lime is capable of imparting class A fire resistance to nine gr ms of asphalt; Ordinary commercial shingles containing from 50 60'% asphalt and from 40 '50% mineral filler such as sand, powdered limestone, when subjegted to the same test as Examples 34, 35, and 36 failed in three fourths to one and one half minutes. It isconclud'e'd from these examples that an asphalt coating mechanically anchored, for example, by any sort of fiber, will have class A fir'e resistance by the addition of a small amount of hydrated lim'e. Sludge is a cheap source of hydrated lime which, in addition, contains powdered limestone, one of the fillers commonly used in the roofing industry. The problem of mechanically ancho'ring an asphalt coating composition under the heat of flame temperatures is well understood in the art and many diiferent expedients are available.

As a guide in formulating asphalt shingle coating compositions, it can be concluded that class A" fire resistance will be imparted to asphalt in the following proportions: 1 part hydrated lime to 9 parts asphalt; 1 part sludge to 4 parts asphalt; 1 part glass or rock wool to 4 parts asphalt. The glass or rock wool also serves to mechanically anchor the coating. The sludge and hydrated lime, While having some anchoring eflFect, should for best results be supplemented by some fibrous or other material which will prevent sliding of the coating. For asphalt coating compositions having -30% asphalt and 20-70% mineral filler, fire resistance will be imparted by 3-22.3% hydrated lime and 4.729.4% mineral fiber, all percentages being by weight of the coating composition.

In Fig. 3 is shown a self-extinguishing asphalt coated paper which, for example, may be used to enclose mineral wool insulating bats. The paper 13 may be ordinary kraft paper, or kraft paper which has been fireproofed by the addition of common fireproofing agents, such as a bath in a mild solution of sodium silicate followed by a bath in a mild solution of ammonium sulphate or ammonium phosphate, or a bath in a mild solution of ammonium phosphate alone without the preceding bath in a sodium silicate solution. The fireproofing of the kraft paper is insutficient to prevent the spread of flame through the asphalt coating 14. The asphalt coated paper (with or without preliminary fireproofing of the paper) is made self-extinguishing by the addition of from 5 to 25% 70% chlorinated paraffin and from 5 to 25% antimony oxide. Higher percentages of chlorinated parafiin and antimony oxide may be used, but are not necessary. The asphalt is the ordinary coating asphalt used in coating roofing.

In Fig. 4 is shown a commercial asphalt tile 15 which has been made self-extinguishing by the addition of chlorinated paraflin. The commercial asphalt tile consists of asphalt heavily loaded with mineral fillers. Due to the presence of asphalt the tile ordinarily will burn completely once combustion has started. Upon the addition of 5% to 25 of chlorinated paratfin and 5% to 25% antimony oxide the tile becomes self-extinguishing 11 in the sense that it will burn only in the immediate presence of flame. As in the case of the other applications of chlorinated paraffin, suitable stabilizers are added.

The paraffin is preferably chlorinated sufficiently to be a solid at room temperatures. 70% chlorinated paraffin is a readily available solid.

Chlorinated paraffin is also usable for fireproofing asphalt emulsions and paint. The asphalt emulsions usually have either a soap or clay base and have the consistency of soft butter. The emulsions may be thinned with water. Upon adding from 525% of 70% chlorinated paraffin and from 5-25% antimony oxide, a fireproof emulsion is obtained. No stabilizer is necessary for this application as the chlorinated paraffin may be mixed with the emulsion without heat. Mineral fillers may be added, such as sludge or hydrated lime.

Asphalt paints consist of asphalt thinned with a solvent, usually a petroleum oil. Since the solvents for asphalt are also solvents for chlorinated paraflin, asphalt paints may be fireproofed by the addition of from 525 of 70% chlorinated parafiin and from 5-25% of antimony oxide.

In the emulsions and paints the fireproofing properties of the chlorinated parafiin result from foaming of the asphalt in the presence of the flame, producing a thermal insulating product which protects the coated material, and from the breakdown of the chlorinated paraffin, releasing chlorides which have a snuffing action on the flame and producing antimony chloride, a heavy gas. While the emulsions and paints will burn in the presence of an externally created flame as soon as the flame is removed the combustion of the asphalt emulsions or paint is immediately extinguished.

; mineral filler containing 322.3%

What I claim as new is:

1. A roof covering having a high resistance to fire comprising a base sheet carrying an asphalt coating flexible when cool and heat plasticizable to a fiowable consistency having uniformly distributed therein 2070% of hydrated lime and 4.7-29.4% mineral fiber, all percentages by weight of the asphalt coating.

2. A prepared sheet roofing having high resistance to fire comprising a base sheet carrying a weather surface coating of asphalt flexible when cool and heat plasticizable to a flowable consistency having uniformly dispersed therein 322.3% hydrated lime and 4.729.4% mineral fiber fusible under roof flame temperatures, all percentages by weight of the asphalt coating.

References Cited in the file of this patent UNETED STATES PATENTS 929,813 Aimes Aug. 3, 1909 1,885,870 Snyder Nov. 1, 1932 2,248,749 Engelhardt et al. July 8, 1941 2,299,612 Clayton et al Oct. 20, 1942 2,332,260 Roediger Oct. 19, 1943 2,326,723 Fasold et al. Aug. 10, 1943 2,326,724 Fasold et a1 Aug. 10, 1943 2,384,671 Fratis Sept. 11, 1945 2,420,644 Athy et al. May 20, 1947 2,424,234 Greider et al. July 22, 1947 2,458,143 Burns et al. Ian. 4, 1949 2,463,983 Leatherman Mar. 8, 1949

Claims

1. A ROOF COVERING HAVING A HIGH RESISTANCE TO FIRE COMPRISING A BASE SHEET CARRYING AN ASPHALT COATING FLEXIABLE WHEN COOL AND HEAT PLASTICIZABLE TO A FLOWABLE CONSISTENCY HAVING UNIFORMLY DISTRIBUTED THEREIN 20-70% MINERAL FILLER CONTAINING 3-22.3% OF HYDRATED LIME AND 4.7-29.4% MINERAL FIBER, ALL PERCENTAGES BY WEIGHT OF THE ASPHALT COATING.