US2472100A - Bituminous mastic coated metal sheet - Google Patents

Description

June 7, 1949. I w, 4|=', FMR, JR 2,472,100

BITUMINOUS MASTIC COATED METAL SHEET Filed Nov. 6, 1943 2 ,Sheets-Sheet 1 METAL @7555i MAST/c /MPFOVED /TUN//VOUS MA .S77 C METL June 7, 1949. w. F. FAIR, JR 2,472,100 BITUMINOUS MASTIC COATED METAL SHEET I Filed Nov. 6, 1943 2 Sheets-Sheet 2 31W: www.'

Patented June 7, l1949 UNITED STATES PATENT oEFicE BITUMINOUS MASTIC COATED METAL SHEET william F, Fsir,'Jr., Pittsburgh, Pa., assigner, by n mesne assignments, to Koppers Company, Inc.,

a corporation of Delaware Application November 6, 1943, Serial No. 509,302

thereby providing metal structural means hav- 1 Claim. (Cl. 154-458) ing heat-insulating, soundproof, waterproof and weather-resistant surfaces.

To provide such surfaces on metals, particularly of a type that does not crack or is not readily broken loose from metal by sudden shock or otherwise, a mastic is prepared from coaldigestion pitch, a finely divided filler, and fibers` preferably precoated with bituminous material. Coal-digestion pitch comprises coal dispersed by digestion in a heat-liguefiablebituminous medium which contains heavy hydrocarbon oil, or to which heavy hydrocarbon oil containing a preponderating proportion of aromatic hydrocarbons or constituents is added during or preferably after the digestion and dispersion process, or during or preferably after thermal decomposition of coal in such process.

In preparing the coal-digestion pitch, coal, such as bituminous coals or coking coals including either high or low' volatile bituminous coal, and certain commercial non-Coking bituminous coals, is heated While admxedwith tar or pitch. The temperature of the mixture while stirring the latter, is gradually increased over an extended period of time to substantially 300 C. or

preferably to a temperature in the approximate range of 300 C. to 310 C. The temperature employed is generally not lower than about 270 C. nor higher than about 350 C.

To obtain a vpitch of highly desirable characteristics for the purposes of the present invention, either before but preferably after dispersion of coal in the tarr and/or pitch in the .digestion process, therev is added the above-mentioned heavy hydrocarbon oil which is preferably heavy water gas tar heavy oil and which latter is preferred above ,light water gas tar heavy oil andabove coal tar heavy oil. These heavy hydrocarbon oils are high-boiling distillates obtained by distilling the corresponding tars and separating the distillate recoverable above approximately 300 C. Only a minor proportion (about per center less) of the oil boils below 300 C.

. 2 The boiling points may be within the approximate range of 250 C. to 450 C.

Heavy water gas tar heavy oils, which are substantially aromatic in character, are obtained by distillationrfrom heavy water gastar which in turn is obtained from water-gas generator plants in which Bunker-C or similar grades of residual petroleum fuel oil are used for carburetting. Heavy water gas tar is also known as residuum tar and is thus termed to distinguish it from whatl was formerly known as water gas tar or is known today specifically as light water gas tar. Light water gas tar heavy oil is obtained from light water gas tar which is produced in the carbul retter of a water gas plant when petroleum distillates are used as carburetting agents.

Depending upon the proportions of coal, tar and/or pitch, and/or heavy oil, in the coal-digestion pitches, the latter pitch products have'been preparedV with ring and ball softening points in the approximate range of 35 C. to 150 C., all

exhibiting improved rheological properties, as well as" considerablyv better temperature sus-` ceptibilities (less change in viscosity with temperature change) and greater resistance to ow than the commonly used bitumens. This is particularly true when the heavy oil employed in the pitch is heavy Water gas tar heavy eiland is even more apparent when this oil is used in conjunction with heavy water gas tar or pitch as the heat-liqueable bitumen. Though the same proportions of coal, tar and oil are used in preparing these pitches and though the products have the same softening points, they have different penetrations depending on the oilused. By A,including heavy water gas tar heavy oil,l coaldigestion pitches of higher softening point, lo r with the same softening point as other coaldigestion pitches similarly prepared withy other oils, are producible with higher penetrations at low temperatures.

The following, by Way of illustration, are ex-A amples of coal-digestion pitchvthat is employed in the present invention:

A. About 187 parts by weight of heavy water' y g over a period of approximately five 4and one-half hours. This temperature is maintained lfor about four hours during which time there resultsa' distillate of labout 5 to 6% based on the tar. At the end of this time heating is discontinued and the-v mixturepermitted to cool. After about forty ,to cool.

anarco 'and the penetration at 32 1". is 14;`at 77 F. is 20.5; and at 115 F. is 40.

B. A mixture prepared from approximately 174 parts by weight of coke oven tar and approximately 58 parts by weight of pulverized bituminous coal is heated to about 300 C. over a period of seven to eight hours, The heating is discontinued and about 72 parts by weight of heavy water gas tar heavy oil are added whereupon the heating is resumed at about 300 C. for an additional one to two hours. Then another 15 parts by weight of heavy water gas tar heavy oil are added whereafter the heating is discontinued and after thorough mixing the product is permitted The softening 'point of the product is about l89 C. and the penetration at 32 F. is 24; at 77 F. is 38; and at 115 F. is 67.

In either Example A or B, the heavy water gas tar heavy oil may be substituted by light water gas tar heavy oil provided high melting coke oven pitch is included in the composition; though the heavy water gas tar heavy oil alone is preferred. Without the high melting coke oven pitch, less light water gas tar heavy oil may be included, which tends to result in a material of poorer weather resistance.

C. A still is charged with 310 parts by weight 'of crude light water gas tar and 40 parts of lightwater gas tar heavy oil. To this mixture 40 parts of molten high melting coke oven pitch having a melting point of 145 C. (cube in air), and

72parts of pulverized coal, are added. This mix- 4 if a tar derived composition isto be used in the mastic.

The precoating of the bers is preferably accomplished in a Banbury mixer, though this is also done by dip-coating and then centrifuging to remove the excess coating material. In a Banbury mixer, about 15 parts by weight of coaldigestion pitch, such as exemplified above, satis-- factorily coats about 85 parts by weight of ber.

A rubber roll. mill, pug mill, or a Banbury mixer may be used to prepare the mastic. The fillers and bituminous material used in the mastic are rst mixed together and then the bers, either precoated or untreated. are added and mixed with' the rst two ingredients. When using a rubber roll mill, the bituminous material is melted on the heated rolls and then the ller and bers are successively added and mixed. When using a ture is heated to 300 C. in approximately one -h O-,urani maintained at about300 C. forapprox- V imately three hours withiagitation, 23 .-parts of `distillate being removed. Thel residual pitch has alsofteningpoint of 88 C. (ring and ball) and penetrations-'at 32 F. (200 grams, 60 seconds) of 20, at 77 F. (100 grams. 5 seconds) of 32 and atnc'F. 'isofgrams 5 seconds) of 61.

In some cases, one to two parts by weight of sulfur may be included in the coal-digestion mix-x ture, or air may be introduced for varying periods. The air and sulfur serve as dehydrogenating agents by which with subsequent additionof heavy water gas tar heavy oil, the characteristics of the pitch may alternatively be adjusted.

The liers employed in the mastic maybe sand,

clay, slate dust and the like or mixtures thereof.

The bers may be mineral, vegetable or animal bers or mixtures thereof including asbestos, cotton (such as that reclaimed from tires), hair and so forth. As previously indicated, it is preferable,

particularly ii the mastic is not subsequently dip-coated, to precoat the bers. For this purpose there are employed tars such as coal tars including lcoke oven tar, horizontal retort tar, and

1 vertical retort tar; heavy water gas tar andl light water gas tar; oil-gas tar, Pintsch gas tar; wood tar; pitches of such tars; oils from such tars;

asphalt: mixtures of these bituminous substances;

' patible with the bituminous material in the mastic. For instance, a non-aromatic petroleum dis-V tillate should not be used to precoat the bers,

Specifically, and for purposes of illustration,

pug mill, the melted bituminous material and lier are mixed in the mill, and the bers are mixed with the resulting mixture in a pug mill, a rubber mill or in a Banbury mixer.

The proportions of constituents employed in the mastic may vary widely. Too much of the bituminous material of a low softening point should not be used if the mastic is to be pliable and yet retain its pressure-molded form. To avoid brittleness, the coal-digestion pitch should not be too high-melting or be present in too small proportions. In other words, pliability is increased while retaining the non-flowing properties of the mastic by increasing the amount of bituminousl material or bers, or by using a bituminous material of lower softening point'.` Less pliable prodl has a-penetration of not less than 10 at 32 F.

and not more than about '1o at 115 F. In the stiffer mastics for instance the penetration of the bituminous constituent having a softening point of at least '75 C. is 0 at 32 F., 0 to 5 at 77 F., and 15 to 35 at 115 F.

as to the proportions of the constituents oi the mastic, the bituminous constituent varies from about 25 percent by weight to about 60 percent by weight (generally about 30 to about 50); the bers are present to the extent of at least about 10 percent by weight; and the lier up to about 65 percent by weight, but generally of the order of 40 to 55 percent.

Examples of mastics employed in products of the present invention, and as illustrated in the accompanying drawings, are as follows:

Example 1.-A pliable but non-flowing mastic surface for flat and corrugated metal sheets is prepared by adding to 52 parts by weight of molten coal-digestion pitch, such as that exemplied above and more particularly in Example A, 40 parts by weight of slate dust and 8 parts by weight of ber precoated with 15% by weight (based on the weight of ber) of the coal-digestion pitch.

The pitch and slate dust are first mixed on a rubber mill or in a pug mill or in a Banbury mix- 'er, and the coated ber is incorporated in the resulting mixture in a Banbury mixer.

l'krample 2.-A less pliable mastic is prepared by compounding 325 parts by weight of coaldigestion pitch of about '75 C. softening point (ring and ball), 575 parts by weight of slate dust. and 100 parts by weight of fiber precoated with 15% by weight (based on the weight of fiber) of coal-digestion pitch, coal tar pitch or other pitch, tar. or high-boiling tar distillate.

Mastic-coated metal sheets of the types illustrated herein, are manufactured by sheeting out the mastic between calender rolls to-a desired thickness. The resulting mastic sheet while still warm, but not necessarily so, is superposed on the metal which is preferably precoated with coaldigestion pitch of substantially the same composition and physical characteristics (melting point and penetrations) as the coal-digestion pitch in the mastic, or is precoated with a suitable adhesive, though the mastic adheres strongly without either upon compression. Moderate pressure and heat are applied to the,metal and/or to the mastic to complete the coating operation.

Sticking of the mastic to molding faces is minimized by applying a thin lm of a lubricating oil or grease preferably of petroleum origin to the mold surfaces, or by applying a light covering of finely divided mineral aggregate such as ground talc or slate dust or stone dust o1' thelike, or by simultaneous use of both of these treatments.

coatin-g the metal with this pitch or with cement made from this pitch; and by dip-coating the mastic-coated metal with this pitch. Various types of surface treatments are then applied as illustrated below.

For certain purposes, the mastic is alternatively prepared from asphalt of about 100 C. (or above) softening point, or is'prepared from coal tar pitch or other pitches of high softening pointsl(120 to 140 C.) mixed with 30% to 40% heavy oil such as heavy water gastar heavy oil or other oil of high aromaticity and with a boiling `point above about 300 C. These bituminous substances are mixed-with the desired proportion of filler and fiber (preferably precoated), after which the mastic is sheeted and applied to bitumen-coated metal surfaces. The mastic-coated metal product, prepared with mastics compounded with these alternative'materials, is preferably finally coated with coal-digestion pitch, particularly of the type described in Example A, for reasons set forth below. l

Products of the present invention 'including preformed or other structural means are diagrammatically illustrated by way of example in time granules or mineral dusts 5 `may be impressed into the surface of the mastic.

In Figs. 2 and 6, the articles illustrated include a precoated metal sheet l and 4, respectively.

The thick mastic layers 6 and 1 respectively, are

' lbonded to the precoated sheets I and 4 with moderate 'pressure and while the mastic is warm.

Whether or not a mastic layer is prepared from coal-digestion pitch, it is preferred to coat the metal with non-brittle and non-flowing coaldigestion pitch. This is applied by dipping the metal in a bath of the molten pitch and slowly in bonding the mastic layers I2 and 13, respec' tively, in place. With a mastic layer prepared from coal-digestion pitch or with such layer and the metal surfacev precoated with a coating M y containing coal-digestion pitch, a cement having the accompanying drawings in which Figs. 1 to 8 are cross-sectional views of fragments of masticcoated metal structures. Similar reference characters in the various figures designate similar or substantially similar features.

In Fig. 1, a sectional view is shown of a fragment of a flat mastic-coated metal sheet l in which a thick layer 2 of the herein-described improved type of mastic containing coal-digestion pitch is dirctly bonded to the metal surface by application of moderate heat and pressure. A similar view of a corrugated mastic-coated metal sheet is shown in Fig. 5 in which the mastic layer 3 may be pre-corrugated to conform with the corrugations of the metal sheet 4, or it may be impressed on the metal surface to form a uniformly coated corrugated sheet. At the same a similar pitch base is preferably employed. A solvent employed in the cement assists in furtheringthe interpenetration, referred to above, of the materials of contacting layers and thereby further enhances the bonding qualities of coal-di-gestion pitch surfaces.

In preparing the above-mentioned bituminous cement in a preferred manner for cold application, a low-boiling solvent, such as coal tar naphtha, is added slowly at room temperature to molten coal-digestion pitch with agitation. The

agitation is continued until all the solvent has been introduced, and the temperature of the iinal mixture has dropped to a substantial extent below the boiling point of the solvent.

Solvent naphtha in the above procedure may in whole or in part be replaced by other lowboiling coal tar solvents; fractions of heavy water gas tar and of light water gas tar distillates; and petroleum distillates of high aromaticity or containing a preponderating proportion of aromatics. The boiling'point ranges of these solvents may be fromabout C., or 135 C., or from 150 C. to about 200 C., depending upon the drying properties desired. The boiling points may also range higher than 200 C., as shown in the following table, depending upon the use of the cement:

Distillatzon of typical solvents Sample Source (l) l (2) Heavy Liiit C081 Ta C051 Tar w. curar w. G. Tar

c. 0. c. 10' First Drop 105 145 14o 148 5% 127 160 153 175 138 165 163 187 148 169 173 201 157 171 182 209 164 174 191 218 168 176 203 225 173 177 207 228 175 179 216 233 179 182 225 241 184 188 242 258 198 258 280 The relative rate of evaporation of solvent and consequent setting-up time of the adhesive at atmospheric temperatures may be changed as deof an aromatic solvent or Ythe lower boiling solvents of any of the sources mentioned may be selected for use, but if slower setting cements are required the higher boiling fractions are selected for incorporation in the cement. In the above table, solvents (1) and (2) provide a relatively quick-drying cement; (3) provides a slightly slower drying cement; and (4) a considerably slower drying cement.

Coal tar solvent naphtha, when employed in the cement, is prepared from coal tar distillate from which most of the tar acids, and in some instances the tar bases, have been removed. Material boiling below 100 C. is preferably removed to prevent too rapid setting of the cement upon application, and to minim fire hazards arising from too low boiling distillates if present. Coal tar solvents and solvents of high aromaticity are particularly compatible with coal-digestion pitches and prevent undesirable sludging and separation of different ingredients into layers.

The proportion of these solvents to be used in the cement depends upon the desired consistency of the product. A relatively viscous product, suitable preferably for warm weather or warm climate use, and better for daubing, rather than brush application, is made from a mix of approximately 80% by weight of coal-digestion pitch (softening point about 75 C. to about 125 C.),

and 20% by weight of a selected solvent. A more fluid product, suitable for easy application in warm weather or warm climates, is made with` about 75% by weight of such coal-digestion pitch and 25% by weight of a selected solvent. A product fluid enough (specific Engler viscosity, 50 c. c. at 50 C., of approximately 18) for convenient application at low to moderate temperatures is madewith about 70% by weight of such coaldigestion pitch and by weight of a selected solvent.

A very fluid cement for brush or spray application is made with 60 parts by weight of coal-digesheavy water gas tar heavy oil-coal-digestion pitch in the mastic and a coal tar-heavy water gas tar heavy oil-coal-digestion pitch in the dipcoating or in the cement, or vice versa; or a light water gas tar-.light water gas tar heavy oilcoal-digestion pitch in the mastic and a heavy water gas tar-heavy water gas tar heavy oilcoal-digestion pitch in the dip-coating material or in the cement, or vice versa: and so forth.

Figs. 'l and 8 are illustrative of a mastic-coated metal sheet product that is dlp-coated as a unit in molten coal-digestion pitch. After a metal sheet is mastic-coated, a dip-coat I5 and Ii (Figs. 7 and 8, respectively) is particularly applied if the ber in the mastic has not been precoated as set forth above. Such a dip-coat is also applied if the mastic coat is prepared from bituminous materials less weather-resistant or having'less desirable rheological properties than mastics prepared from coal-digestion pitch particularly ofthe type described in Example A. Only a thin coating of such coal-digestion pitch is needed on ordinary asphaltic, or conventional tar or pitch or other bituminous mastic coating I1. to provide structural means having superior weather-resistant and rheological properties over wide temperature ranges. These properties are improved by increase of depth of penetration of the dip-coating material into the mastic layer.

In some instances the hot dip-coating is subsituted by the cold application of compositions such as the above-described cements with selected solvents.

An article to be hot dip-coated is submerged `may also be obtained by applying pressure. The

withdrawal of an article, particularly masticcoated metal sheets or panels of large dimensions, is preferably at a decelerating rate to obtain a uniform coating. The total time of submergence of the lowermostportions of a sheet should not be such as to result in any substantially 200 C.), thus producing an adhesive, quick drying bituminous cement, that is applied cold, and

.having an Engler specific viscosity of approxi. mately 8 to 15 (50 c. c. at 25 0.).

Fillers, such as,slate dust or ou'r, iinelydivided talc or clay maybe 'added to the cement, if desired, to the extent of 25 to 30%; or 'evenup to fin the cement or dip-coating since better bonding is obtained than in cases where the compositions are different as indicated above.l The same is .true in the case of the coalfdigestion pitches described in the other examples. Advantageous results lare obtained however for bonding purposes 35% to provide a desired weather-resistant adhec different change in physical or structural condition of a lowermost portion from that of an uppermost portion.

The articles in Figs. 5, 6, '7 and 8 exemplify the application of granulesfor 'dusts A5 or i8 either lightly or deeply impressed, and bonded with or without a coating such as .a dip-coat of coaldigestion pitch, or cold-applied cement coat prepared from coal-digestion pitch and solvent, or a` bituminous paint coat with or without inert filler. The surfacing granules or dusts, including slate dust, clay, sand and others, as well as mica, are solid, inert, oiland water-insoluble,

- heat-resistant mineral, or metallic, or artificial lanchoring the surfacing particles to mastic-coated metal. For certain purposes pigmented bituminous paints or metal paints such as aluminum or bronze paints vcontaining a bituminous vehicle vmay be applied for heat and light reflection.

In forming and bonding the mastic layer to a by employing for instance a heavy water gas tar` 7.5 metal sheet, molding temperatures and pressures respectively are employed, for instance, of about 75 C. to about 150 C. depending upon the melting point of the binder, and of from about 200 lbs. per sq. in. to about 2000 lbs. per sq. in. depending upon the thickness of a sheet and amount of compression required.

, Besides the desirable characteristics referred to above, the mastic-coated metal article of the present invention has unique water-repelling properties, thereby eliminating corrosionor rusting of the metal. In comparative tests with conventional mastic coats, after immersing in water for ten days at room temperature and also at 50 C., a change in weight of only 1% is noted in the improved mastic coat; whereas other commercially known bituminous mastics submitted to similar tests show increases in weight of 15% to 25%. The hot dip application of the improved pitch as a precoat, dries a metal surface, and the nally hardened coat prevents rusting, and furtherance of rusting if the metal surface is rusted before coating; and prevents rusting even of unpickled metal surfaces.

An improved pitch of the type used herein tolerates excessive bending while also adhering strongly to a metal surface. In the use of the improved pitch coating on metal such as galvanized iron, the adhesion of the coating is strikingly demonstrated by gently peeling 01T or stripping the coating with a knife or other sharp-edged instrument. In the peeling operation the galvanizing coat is removed with thepitch coating.

What is claimed is:

In a metal structural element having a layer of iillerand fiber-containing bituminous mastic bonded directly to metal surface of said element, the said layer of mastic and said metal element both being in sealed-in relationship to a coating 10 of coal-digestion pitch containing heavy water gas tar heavy oil, said pitch in combination with said C.'to about 150 C. and penetrations of not less than 10 at 32 F. and not more than 70 at 115 F., and the said pitch containing the said oil preventing penetration of water to the metal surface and 'being non-owing at high atmospheric temperatures and being non-embrittling at low atmospheric temperatures, thereby preventirfg removal of said layer from said metal surface.

WILLIAM F. FAIR, JR.

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

UNITED STATES PATENTS Number Name Date 407,195 Garrison July 16, 1889 441,036 Siebel Nov. 18,'1890 1,277,755 Robertson Sept. 3, 1918 1,289,537 Porter Dec. 31, 1918 1,362,888 Mullin Dec. 21, 1920 1,698,267 Kirschbraun Jan. 8, 192'9 1,701,926 V Kirschbraun Feb. 12, 1929 1,863,186 Burns June 14, 1932 1,864,971 Young et al June 29, 1932 1,875,458 Hill Sept. 6, 1932 1,925,005 Rose Aug. 29, 1933 2,158,772 Beckwith 'May 16,1939 2,184,139 Cunnington Dec. 19, 1939 2,212,122 Miller Aug. 20, 1940 2,249,412 Yeager July 15, 1941 2,304,773 Anderton Dec. 15, 1942 2,325,594 Denman Aug. 3, 1943 2,395,041 Fair Feb. 19, 1946 2,395,853 Fair Mar. 5, 1946 oil having a softening point of about

Images