US2249412A - Coating composition and the method of preparing the same - Google Patents

Description

July 15, 1941- F.-w. YEAGER' COATING COMPOSITION AND THE METHOD OF PREPARING THE SAME Filed April 16. 1958 INVENTOR f'ra/zz/r Yeager BY Z 6; (7 ATTORNEY Patented July 15, 1941 NT orrics Y COATING COMPOSITION THE METHOD F PREPARINGTHE SAME V Frank'William Yeager, Cliffside-Park, N. J., as-

signor to The Barrett N. Y., acorp oration of N Company, New York,' ew Jersey Application April 16, 1938, SerialNo. 202,573

' 8 Claims. (Cl. 106-278) This invention relates to coating compositions and more particularly to bituminous coating compositions for the protection of metal surfaces such as the surface of iron or steel pipes.

An object of my invention is to' provide a bituminous coating composition of brushable or sprayable consistency which is not subject'to substantial sedimentation when a stored for long periods of time and which when applied to surfaces to be protected, isself-drying, bonds firmly ith the surfaces and does not become brittle atlow atmospheric temperatures or soften at high atmospheric temperatures such as encountered when subjected to intense summer heat.

Another object of myinvention is to provide a novel process of making a bituminous :coating' composition whichis not subject to objectionable sedimentation upon storage in closed containers for long periods of time and which possesses low susceptibility to temperature changes. Other,

objects and advantages of the invention will appear hereinafter. f '1 The coating composition of myinvention is constituted of a coal-digestion pitch base: i; e., pitch produced by digestion of coal with, coal tar, water gas tar or a mixture of such tar and tar distillate under conditions such that decomposition of the coal occurs (as evidenced for for example by the evolution of the typical liquid and gaseous decomposition products of .coal and the production of a pitch which for a given softening point has a higher penetration at 25, C. than a corresponding pitch produced by the distillation of the tar or mixture'of tar and tar distillate in the absence of coal) and the nonash non-volatile constituents of the decomposed coal form a homogeneous blend with the tar, and a solvent in amount sufiicient to render the composition of brushable or sprayable consistency. Substantial amounts of the mineral ash constituents of the coal may also be and usually are dispersed in my product, the proportion depending somewhat on the physical form of the ash and the digestion conditions. The coaldigestion pitch base and the solvent are of such characteristics and are blended under'such con-' ditions as to produce a free-flowing liquidcomposition, in which composition I objectionable sedimentation does not take place upon storage in closed receptacles. Preferably the composi-, tion' contains from 35 to 55. per cent of solvent of sufficient volatility to'permit drying of the composition by evaporation of the solvent when applied to a pipe or other metal surface and exposed to ordinary atmospheric conditions.-

;mix ture is reduced to 100 F. n composition may then be passed through a colloid mill. The cooling step is an important fea- In accordance with my invention 1 heat coaldigestion pitch, preferably of a softening point (ring and ballloffr'om 150 to about 300 F., "to 'a temperature, considerably above the softening point of'the pitch,- sufficient to reduce the pitch to fluid molten condition and to avoid gel f formation during addition of the solvent. While agitating the molten pitch,-a major portion of the total solvent employed 'is'added' slowly tothe' molten pitch and the resultant mixture of solvent and pitch is quickly cooled to a temperature materially below the softening'point; of the' 'pitch, preferably below- 145 F. The; re-

mainder of the solvent is then added'and the cooling continued until the temperature of'the or lower. The

ture of my invention. I have found that by quickly cooling the mixture between additions of solvent thereto'the mobility of the solution is reduced so as to prevent coagulation of the digested coal particles with consequent produc- "tion of a coating composition in which objectiona-ble sedimentation on storage in a :closed In order that my invention may be more fully understood, 1 shall describe an embodiment thereof in connection with the accompanying drawing wherein, a

'Fig. 1 is a view illustrating somewhat diagrammatically one form ofa paratu's which may beemployed invproducing coal-digestion 'pitch for use in mycompositions; and

i 'Fig. 2 is a diagrammatic view of a mixing tank which'may be employed in the productionof the composition.

' For purposes'of exemplification, I have shown in Fig. l an apparatus which may be employed foriproducing coal-digestion pitch base for my coating compositions involving tank I equipped I with valved tar or oil inlet 2, oscillating stirrer 4 mounted on oscillating shafts 6, which shaft is journalled in the ends of tank I and is driven from motor 8 through oscillating gears illustrated diagrammatically at I 0. Reference numeral. l2 designates a pump situated: incirculating conduit I3 provided with coils llt located' in furnace l6 equipped with a liquid or gaseous fuel burn-er l8 and bafile I9. Pitch outlet 20 is connected to circulating conduit, l3- -A' thermometer, 2! is located in the conduit near the outlet'end. of con l4. Tank l is equippediwith 1' coal charging door 24, thermometer 25 and vapor outlet conduit 21 communicating with a condenser 28. In lieu of a still equipped with a heating coil and circulating pump, a direct fired digesting apparatus; e. g. apparatus involving a digestion tank such as tank I equipped with suitable fuel burners located therebeneath, may be employed.

Coal-digestion pitch may be produced byheating, while agitating, bituminous coal, for example, commercial steam coal, coking coals and certain commercial non-coking bituminous coals, in intimate contact with coal tar, water gas tar, or a mixture of such tar and tar distillate under elevated temperature conditions so that decomposition of the coal occurs and the non-ash, nonvolatile constituents of the decomposed coal are blended homogeneously with the tar or tar distillate in which the coal is digested. The temperature of which the coal and tar or tar distillate are heated may vary from about 270 C. to 360 C. but in general the temperature is around 310 C. The heating period in practice may vary depending upon the quantity of material in the heating vessel, the efficiency of the stirring apparatus, the amount of heating surface, etc.

Y The proportion of coal used, and the temperature and time of digestion, depends upon the particular type of coal and the character of the tar or tar oil employed. Satisfactory commercial products are obtained by carrying the digestion at least to the pointwhere substantial decomposition of the coal occurs or beyond. It is important to control the degree of decomposition of the coal by controlling not only the time of digestion but the temperature to which it is subjected during digestion. If the digestion temperature is too high, excessive decomposition occurs, and the products begin to lose their characteristics properties, such as relatively low susceptibility to temperature change, and approach ordinary pitch.

Successful operation of the digestion process requires careful control to effect the desired degree of decomposition of the coal. It has been found that if the digestion is carried out so that no decomposition or only incipient decomposition of the coal occurs, products of a-quite different nature than those desired are obtained. If, however, the time and temperature of digestion of a given coal are increased a relatively sudden change occurs in the consistency of the product together with marked evolution of typical, volatile coal decomposition products and a reduction in the content of volatile combustible matter in the digested material. While the temperature and time of digestion necessary to produce the coal-digestion pitch may vary for various kinds .1,. coal and tar or tar distillate in which the digestionis carried out, each mixture of coal and tar or tar distillate should be subjected to definite digestion conditions to accomplish the necessary decomposition of the coal.

The following example will illustrate the general characteristics of coal-digestion pitch .products forthe formation of coating compositions in accordance with the invention; a mixture of approximately equal partsby weight of coke-oven tar and coal-tar heavy oil boiling above 250 C. is introduced into the tank I. through inlet 2 and circulated by pump 12 through conduit l3 and heating coils l4 until the temperature of the tar in the tank reaches 150 C. or somewhat higher and the agitator 4 is then started running. Bituminous coal in amount equal to about one-third of the weight of the combined tar and coal- 1 oil charge is then added, preferably in pulverized condition, through charging door 24 and the furnace flame regulated to heat the contents of the still rapidly to a temperature of from about 215 to 240 C. The furnace fire is then regulated to raise the temperature of the efliuent from coil M gradually until the contents of the tank reach a temperature of about 310 C. or somewhat higher. The temperature of the mixture in the tank is maintained at about 310 C. until the non-ash constituents of the mixture form a homogeneous blend with the coal tar and heavy oil to produce a coal-digestion pitch of desired softening point; a substantial fraction of the ash constituents is usually simultaneously permanently dispersed in the product. Operation of the agitator and pump is then stopped and the contents of the still permitted to settle for an hour or more to remove coarse material, e. g. slate, which has not been disintegrated and dispersed by the digestion. The coal-digestion pitch products may be withdrawn from the tank I through valved outlet 20. Vapors escaping through line 21 may be cooled and recovered by means of condenser 28. By carefully controlling the temperatures and time of digestion, coal-digestionpitch of the desired softenin point and penetration may be obtained without cutting back the pitch with tar, creosote or other material.

, Products especially adapted for use as the base for the coating composition of this invention should contain in general from 15 to 30 per cent of coal and should have a penetration at 77 F., 200 grams, 30 seconds, of between 10 and 80 and a softening point (ring and ball) of between and 300 F. Preferably I use a pitch having a penetration of 10 to 40, and a softening point of 180 to 250 F. Softening points and penetrations are determined in accordance with procedure (using standard apparatus) prescribed by the American Society for Testing Materials.v

Coal-digestion pitch produced, for example, as hereinabove described, is charged into mixing apparatus such as shown in Fig. 2, equipped with a mechanical agitatordesignated in the drawing by reference numeral 3!, a cooling and heating jacket, 32 for conveying a cooling agent such as cool water or a heating agent such as steam in heat-exchange relation with the mixer, and a valved bottom outlet 33. The pitch is introduced in, a preheated fluid condition and agitated at a temperature just sufficient to maintain the solu- ]tion beyond the gel stage in order to permit agitation, i, e. a temperature of about 100 F. above its softening point; e. g. pitch of a softening point of 200 F. (ring and ball) may be heatedto a temperature of 290 F. to 300- F. A major portion of the total solvent employed is slowly, added in cool condition; i. e. at a temperature of not more than about 100 F. to the molten pitch. To produce a composition containing about 45 per cent of solvent, preferably about two thirds of the total solvent is added to the pitch in molten. condition at the above mentioned temperature.

The. temperature of the mixture is then quickly 7 reduced below the softening point of the coal-digestion pitch, preferablybelowl45 F. by passing water through the cooling system. The remainder of the solvent in cool condition i. e., at a temperature not higher than 100 F.-is then added and the cooling continued until the temperature of the mixture is reduced to below about 100 F. The contents of the mixer are then passed through a. colloid mill and minor adjustments in .pitch containing talc filler may consistency, if necessary, produced by adding small amounts of solvent.

distillate may be described as boiling within the i For examrange of from about 160 to 220 C. ple, it may have the following distillation range:

' he Per cent Distilled 01f at 170 C 5 Distilled off at 180 C 60 Distilled off at 200 c 95 It will be noted that a major portion of the solvent distills off at a temperature between 170 and 200 C. Lower boiling coal-tar solvents may also be employed. The amount the bitumen may vary from 35 to 55 per centby volume and preferably about 45 per cent is utilized. By careful control of the temperature conditions under which the coal-digestion pitch and solvent are mixed, as hereinabove described, jor portio of the solvent, at a temperature I obtain a free-flowing liquid coating composition of brushable or 'sprayable consistency at atmospheric temperatures which is not subject'to objectionable sedimentation whenstored in closed containers for long periods of time.

, '3 The composition'of this invention may be employed for any purpose for which a bituminous paint is required and is particularly'adapted for priming metal surfaces; e. g., the interior or exterior of metal conduits employed for con-- veying water or other fluids. After the priming coat has dried, an enamel, produced by mixing molten coal-digestion pitch manufactured as hereinabove described, preferably of a softening point (ring and ball) of from 200 to 270 and a penetration at 77 F., 200 grams, seconds, of from 20 to 40, with from 10 to 40 per cent ground mica, talc, or other filler, prefer.- ably 25 to 35 per cent talc, may be applied in molten condition to the primed metal surface and permitted to harden by cooling.

The bituminous coating compositions of this invention bond firmly with surfaces to which they are applied and neither sag nor peel at' elevated atmospheric temperatures, nor become unduly brittle at low atmospheric temperatures.

It has been demonstrated by tests that metal surfaces primed with coating compositions of this invention and coated with coal-digestion a temperature of 160 F. for a period of more than twenty-four hours without sagging or peel- 'i. ing and to a temperature of 0 F. without cracki ing or disbonding of the coatings.

Furthermore, the coatings are tough, chemically inert to water and many aqueous liquids, and possess a smooth surface, thereby minimizing friction losses incident to conveyance of fluids through conduits lined with the coatings. My composition is not subject to settling out of substantial amounts of solid material and may be transported and stored for long periods of time without objectionable sedimentation.

The addition of solvent to the pitch composition in two stages and careful control of the temperature during addition, as abovedescribed, appear to be important factors in the production of coating compositions having minimum tendency to sag or peel when applied or to :de-

of solvent added to mechanism "of this effect is not known but the reduction to a minimum of the period at which solvent and pitch are mixed" at elevated temperatures bymy process clearly contributes to A coal-tar 5 homogeneous dispersion and solution of the base in the solvent. i

The subject matter of this application is related to my copending application Serial No. 202,574, filed April 16, v19 3,8,-novv United States Patent 2,228,102 of Jar'iuary'7,1941.

It is to be understood that the above description should be interpreted as illustrative and not in a limiting sense andjthat this invention is not,

restricted to the above disclosure other than as defined in the appended claims.

I claim: I

1. The process of manufacturing a self-drying, substantially non-'sedimenting, fluid coating composition containing-coal-digestion pitch and a volatile solvent for the coal digestion pitch, comprising melting the' coal-digestion pitch by heatingit to a temperature substantially above its softening point to produce a fluid molten pitch, adding to the molten pitch a mastantially below the temperature of'the pitch, cooling the mixture to a temperature substantially belowthe softening point of the pitch and adding the remainder "of Y the solvent in cool 0 condition to the mixture.

2. The process of making; a self-drying, substantially nonrsedimenting gcoating composition containing a volatile solvent for the coal digestion pitch and coal-digestion" pitch I produced by heating a mixture of bituminous coal and tar together at elevated temperatures until the non-ash constituents of the mixture form a homogeneous blend, comprising heating the pitch to a temperature substantially above its softening point to produce a fluid molten pitch, which temperature is not substantially higher than that required to maintain the mixture of pitch and solvent above the gel stage with a mobility suitable for eflicient mixing, adding to the heated pitch while agitating a major portion of the solvent in cool condition, cooling the mixbe subjected to softening point of the pitch and adding the remainder of the solvent-in cool condition to the mixture.

3. The process of making a self-drying, substantially non-sedimenting bituminous coating composition containing coal-digestion pitch of a softening point (ring and ball) of from 180 to 250 F. and from 35 to 55% the coal digestion pitch, which solvent is volatile at atmospheric temperatures, comprising heating the pitch to a temperature about 100 F. above its softening point to produce a fluid molten pitch, slowly adding to the molten pitch while agitating a major portion of the solvent posit Sediment when stored. The complete at a temperature of not more than F., cooling the mixture to a temperature below the softening point of the pitch and slowly adding the remainder of the solvent.

4. The process of making a substantially nonsedimenting, self-drying bituminous coating composition constituted of coal-digestion pitch of a softening point (ring and ball) of from 180 to 250 F. and from 35 to 55% of solvent the major portion of which boils within the range of to 200 0., comprising heating the pitch to a temperature about 100 F. above its softening point, slowly adding to the molten pitch, while agitating, a major portion of solvent at of a solvent for g a temperature not higher than 100 F.-, cooling the resultant mixture to a: temperature below 145 F., adding the remainder of the solvent at a tempeiature not higher than 100 F. and continuing cooling of the mixture.

5. A substantially non-sedimenting, self-drying bituminous coating composition constituted of coal-digestion pitch of a softening point (ring and ball) of from 180 to 250 F. and from 35 to 55 per cent of solvent, the major portion of which boils within the range of 170 to 200 0., said coating composition being obtainable by heating the pitch to -a temperature about 100 F. above its softening point, slowly adding to the molten pitch, while agitating, a major portion of the solvent at a temperature not higher than 100 F., cooling the resultant mixture to a temperature below 145 F., adding the remainder of the solvent at a ,temperature not: higher than 100 F., and continuing cooling of the mixture.v

6. A substantially non-sedimenting,v bituminous coating composition of brushable and sprayable consistency at atmospheric temperae ture constituted of coal-digestion pitch produced by digestion of bituminous coal in tar until the non-ash constitutents of the mixture form a homogeneous blend, and a solvent for the pitch in amount suflicient to produce a composition of brushable and sprayable consistency, -said solvent being suflicientlyyolatile to evaporate when the composition-isapplied to a surface and exposed to the atmosphere, said coating composition being obtainable by heating coal-digestion pitch to a temperature substantially above its softening pointto produce a fluid molten pitch, adding to the molten pitch while agitating a major portion of the solvent, cooling the resulting mixture to a temperature below the softening point of the pitch, and adding the remainder of the solvent.

'7. The steps in the process of making a substantially non-sedimenting, self-drying, bituminous coating material which comprise adding solvent for a coal digestion pitch, which solvent is volatile at atmospheric temperatures, to the coal digestion pitch at a temperature considerably above its softening point, immediately after the addition of the solvent cooling the mixture to a temperature substantially below the softening point of the coal digestion pitch before any further addition of the solvent to reduce the mobility'of the solution sufficiently to substantially prevent coagulation of the digested coal particles, and. then adding the remainder of the solvent to produce said non-sedimenting coating composition.

8. The process of making a substantially nonsedimenting bituminous coating composition which comprises heating a coal digestion pitch to a temperature considerably above its softening point to produce a fluid molten pitch, slowly adding to the molten pitch while agitating a major portion of solvent for the coal digestion pitch, quickly cooling the resultant mixture to a temperature materially below the softening .point of the pitch, then adding the remainder of said solvent and continuing the cooling until the temperature ofrthe mixture is reduced to below 100 F. I

' FRANK WILLIAM YEAGER.

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