US 2400563 A
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Patented May 21, 1946 ASPHALT AND ASPHALT COATED ROOFING COLIBOSITION S Francis L. Mark, Redondo Beach, Calif.
Serial No. 460,920
No Drawing. Application ctober5, 1942,
4 clams. Thi invention relates to filled asphaltic cements and to filled asphaltic coating composition employing balanced mixtures of finely divided (c1. roe-281) mineral matter, such as fine mineral dust, and
diatomaceous earths. Filled asphalt containing mineral dust, such as rock dust and diatomaceous earths have been employed during the past for various uses. It has been observed that the addition of diatomaceous earth to steam refined asphalts has the effect of imparting to such asphalt some of the properties of air-blown asphalt, the addition 01' the diatomaceous earth increasing the softening point and lowering the penetration of steam refined asphalt. The addition of diatomaceous earth also has the efiect of increasing the tensile strength of steam refined asphalt. However,'such mixtures of asphalt and diatomaceous earth do not have the pliability ofairin diameter. when this un is unwound at low temperatures transverse cracks appear inthe coating and often carry clear through the base felt itself. As a result, the roofing cap sheet disintegrates -,and allows water to enter the underlying roof structure. This may result in leaks and in moisture blisters on the surface.
In order to limit this cold weather cracking it has been necessary in the past to use relatively soft. asphalts. This was made particularly imperative by the fact that the filler added to the asphalt had the effect or actually increasing the brittleness of the asphalt. The manufacturer'of asphalt roofing was'then on the horns of a dilemma. He could have asphaltic roofing which would not run and excessively soften at the high temperatures to which the roofing might be blown asphalt mixtures and. at low temperatures are brittle. This brittleness of such asphalts has excluded them from use in one of the most important fields of asphalt application, that is in prepared roofing.
Prepared roofing, whether of the rolled sheet type or the shingle type. is prepared by saturating felted material with a saturating asphalt, after which the asphalt saturated sheet is coated with a filled type asphalt material. The coated asphalt may be sprinkled with rock granules while the asphalt is softand the granules are pressed-into the asphalt,
The type of asphalt which has been employed for thiscoating purpose has been an air-blown asphalt because the steam blown asphalts, even though they are filled, are too. brittle at low tem "v peratures and too soft at high temperatures.
Fillers are employed in the asphalt for'the purexposed in the summertime by using an asphalt of a relatively high melting point andadding sufilcient filler and as a result sufier the cracks and shattering effect whichfollow from the brittleness of such mixtures at low temperatures. He could use a soft asphalt and limit his filler content to obtain proper pliability at low temperatures, but suffer the consequences of a running asphalt at high temperatures. phalts at high temperatures becomedisplaced when asphalt roofings are positioned at any angle and since the granules of aggregate employed as a coating become displaced, due to the softness of the asphalt, such'asphalt roofings are impractical.
facturer was forced to sufier the consequences of lack of low temperature pliability of his filled asa phalt type of coating.
pose of stiffening the. asphalt and rendering it less the roofing may be exposed in construction or use. One of the most serious of these difiiculties is the cracking or shattering or the asphalt at low temperatures. Thus the asphalt coated roofing may not be laid at temperature much below about to.60 F. Shingles when laid at this temperature are shattered when nails are driven through the shingles. Rolled roofing is wound into rolls usually on a mandrel core or 4" to 5" While this typ of coatsceptible to temperature change. The minera I have now made the discovery that diatomaceous earth when used in proportioned mixes with mineral dust in oxidized asphalt givesa balanced mix which removes the manufacturer from the horns of the dilemma. It gives the, high temperature stability together with the low tempera-- ture pliability.
Diatomaceous earth, as employed in this in-' vention, produces a marked increase in the softening point of the asphalt. Less than ten per cent of this material when used-with mineral dust in proper-proportion will raisethe softening point of a blown asphalt from abeut; F. to 230 resulting in a coating of greatly improved pliability and higher tensile strength and resistance -to Since such as-v Since the latter considerations are more im-l portant and in many cases controlling, the inanu- .my invention is given by and to free mixture of water.
. is then added. The diatomaceous earth has the 2 the pliability of the asphalt has permitted me to make roofing material which may be handled as low as 5 F. without any cracking. In unrolling such a rolled roofing no cracking has been apparent, even down to' the last portion with sharpest curvature. Repeated flexing of this material has shown that it is entirely pliable so that it may be handled without cracking. When using this material on shingles it may be-nailed at temperatures well below freezing without shattering.
Asphalt roofing may contain small amounts of water even though the asphalt is carried to 500 F. in its preparation. It is present due to absorption in the felted sheet and may be present under the roofing laid over an old roof or it may enter through seams. When this moisture expands into vapor it causes blistering of the surface and a destruction of the coating. I have found that the addition of this diatomaceousearth in proper proportion, mixed with minera filler material gives a tougher surface which prevents blistering. This arises from the fact that;
the diatomaceous earth will increase the tensile strength of the asphalt.
The ability of the .diatomaceous earth to raise the melting point while improving the low temperature pliability has permitted me to use lower softening point oxidized asphalts and thus I have phalts because I have been able to impart this high temperature stability by the use or diatomaceous earth. This lower-softening point has improved the adhesive properties of the asphalt mix and I have been able to overcome the tendency of the asphalt to run and the granules to be displaced at high temperatures.
' The diatomaceousearth also results asphalt of improved weathering properties when subjected to the standard Weatherometefl test in which the asphalt was subject to rays at 140 F. and frozen at F. in repeated operations. The diatomaceous earth filled asphalts of my invention-show an improvement in weathering characteristics showing a resistance to failure of one-third or more. In other words, they may be exposed to the above treatment for a 3, /a% greater period than the rock dust filled type of oxidized asphalt before failure occurs. V
The following exampleof one embodiment of not for the purpose of limiting my invention:
In making the filled asphalt of my invention,
. I employ an air-blown asphalt having a ball and. ring softeningrpoint of 190 to 205 F. The
phalt is heated to a astemperature of about 350" to use kilndried diatomaceous earth that is uncalcined material having a water content of about 6% or less.
, centrifuge tube which is filled to the 1,5 centiother proportions and specifications will give a for rolled roofing.
int. filled ultra-violet way of illustration and I or higher, sumcient to impart fluidity to theasphalt. To'this asphalt'is added mineral filler of the conventional type, to-wit: rcckdust, pulverized limestone, fine silica sand. round mica, talc, volcanic ash, clays, ground asbestos, powdered meter mark. The tube is whirled at 1800 revolutions. per minute and the volum occupied by the diatomaceous earth is read and converted into pounds per cubic foot.
The asphalt and diatomaceous earth and powdered mineral filler are proportioned to give the following properties. The'ball and ring melting point should be 210 F. or better. The viscosity of the mixture when read at 360 by the Brookfield Viscosimeter should be in the range of about 5,000 to 20,000 centipoises'. The penetration, when measured on the standard penetrometer, according to ASTM specifications, employing grams for five seconds at 77 F. should range from about 1.2 to 1.7 millimeters. I proportion the. asphalt, rock dust, and diatomaceous earth to obtain the above specifications. While useful result and I do not desire to be limited to the'illustration of my preferred embodiment, I have found that the above limits give a highly advantageous result when employed as a coating In the following tabla which illustrates various examples of compositions employed, the symbol S. P. represents the softening point of the asphalt.
The symbol P. D. represents paving dust and D represents diatomaceous earth and B. 8: R. standsfor ball and ring softening point. Table 1 Asphalt 55% of S. P. 62% Of 195 S. P.
Filler 39% P. D.,'6% D. 8% D.,30% P. D. Softening point 230 219 v Penetration-77 F. v 1.7 1.7 ViS. at 360 9,200 C. 5,000 C. P.
Table 2 0 Percent Percent Softening Penetra- Perceut a i at? at? as 11 100 195- 26 55 7.6 31.4 229 16 55 c 22s 1c In choosing the diatomaceous earth to be employed in my composition, by a proper selection of the type of. diatoms which I use I have been able to obtain a highly improved result in increasing the melting point and tensile strength as well as the pliability of filled asphalt. This improvement in these properties is ofgeneral utility ploying' diatomaceous earth, such as in pipe line coating, road'construction and in all places where filled asphalt has been employed asan asphaltic shells, slate flour. Diatomaceous earth is also i added. I find that I obtain superior results by first dispersing the diatomaceous earth in the asphalt, agitating the. mixture to ensure dispersal The mineral filler mineral filler to prevent undue settling. I prefer,
cement. There are over 10,000 different types ,0! diatoms. Of these types are those whose length is markedlygreater than their width. The round or disc shaped diatoms,
For best results, diatomaceous earthshould have a wet density ofabout 18 or lesspounds per cubic foot.
I have discoveredthat in filled asphalts em- I I there is one class of diatoms which is termed the elongated type.
The type of diatoms which are here'referred to their dimensions of length and width nearly equal, do not have as great an effect. This type of diatom may be employed, but must be used in larger amounts nor do they have the eflect of improving the low temperature pliability and the tensile strength that is obtained with the elongated type. These elongated forms are characterized by skeletons which are wide and thin or long and narrow. These elongated" diatoms are to'be contrasted with the smallheavy walled type. This classification is well understood in this art. See 1, 2, 3, and 9, and 12 to 18 of Diatomaceous Earth by Calvert, A. C. S. Monogram Series 52, Edition of 1930.? Some examples of the elongated type appear in Fig. 16. Examples of the round type appear in Fig.13. I have found that when employing these elongated diatoms I may obtain a better result in improvement of tensile strength and low temperature pliability than when employing diatoms whose dimensions of length and breadth more closely approach each other, as in the case of the round type of diatom.
It is to be understood that the foregoing examples are for purposes of illustration and are not to be considered as limiting of the invention. Various changes and modifications may be made therein without departing from the spirit of the appended claims.
I claim: 1. A filled asphalt comprising an oxidized asphalt having a bail and ring softening point or about 190 to about 205 F. and mineral filler and kiln dried diatomaceous earth whose diatoms, in preponderant proportion, are of the elongated type. having a wet density of less than about 18, said mixture of asphalt, filler, and diatomaceous earth having a ball and ring softening point of at least 210 F., and higher than said oxidized asphalt, a viscosity of about 5,000 to 20,000 centipoi ses at 360 1". and a penetration of 1.2 to 1.7 millimeters when measured at 7'1 1"., employing loo-gram weight for five seconds.
2. A filled asphalt comprising an oxidized asphalt having a ball and ring softening point of about 190 to about 205' I". and mineral fillerand kiln dried diatomaceous earth having less 5 than about 6% moisture, said mixture of asphalt,
filler and diatomaceous earth, whose diatoms in preponderant proportion are of the elongated type, having a ball and ring softening point of at least 210 F. and higher than said oxidized l0 asphalt, a viscosity of about 5,000 to 20,000 centi-- poises at 360 F. and a penetration of 1.2 to 1.7
100-gram weight for five seconds.
3. Prepared roofing comprising-sheet material millimeters when measured at 77 F., employing coated with a filled asphalt comprising an oxidized asphalt having a ball and ring softening point of about 190 to about 205 F. and mineral filler and kiln dried diatomaceous earth whose diatoms, in preponderant proportions, are of the go elongated species, having a wet density of less than about 18, said mixture of asphalt, filler and diatomaoeous-earth having a ball and ring softening point of 210 F. or betten-and higher than said oxidized asphalt, a viscosity of about 5,000 to 20,000 centipoises at 360? F. and a penetration of 1.2 to 1.7 millimeters when measured at 77 F., employing IOU-gram weight for five seconds.
' 4. Prepared roofing comprising sheet material coated with a filled asphalt comprising an oxiso dized asphalt having a ball and ring softening point of about 190 to about 205 F. and mineral filler and kiln dried diatomaceous earth whose diatoms, in preponderant proportions, are of elongated species, having less than about 6% moisture, said mixture of asphalt, filler and di-- atomaceous earth having a ball and ring softening' point of 1 210 1". or better, and higher than said oxidized asphalt. a viscosity of about 5,000 to 20,000 centipoises at 380? F. and a penetration of 40 1.2 to 1.! millimeters when measured at 77 1'2,
employing -gram weight for five seconds.