US2697697A - Joint sealing compounds comprising a vinyl chloride-vinyl acetate copolymer, coal digestion pitch and tar heavy oil - Google Patents

Description

United States Patent JOINT SEALING COMPOUNDS COMPRISING A VINYL CHLORIDE-VINYL ACETATE COPOLY- MER, COAL DIGESTION PITCH AND TAR HEAVY OIL Harold R. Beck, Westfield, N. J., and Robert S. Detrick, Pittsburgh, Pa., assignors to Koppers Company, Inc., a corporation of Delaware No Drawing. Application November 24, 1952, Serial No. 322,364

5 Claims. (Cl. 260-285) This invention relates to compositions of matter and is particularly directed to compositions useful as joint sealers for sealing joints in concrete pavements and like structures. More particularly the invention is directed to joint sealing compositions which are resistant to jet fuels which compositions comprise a mixture of a major proportion of coal digestion pitch, a minor proportion of a high molecular weight vinyl chloride-vinyl acetate copolymer-containing up to vinyl acetate, and crystal-free tar heavy oil in proportions to give a product having a cone penetration of from 50 to 90 decirnillimeters at 77 F.

In the construction of pavements and like concrete structures, it is customary to fill the expansion joints with a joint sealer to keep water and other foreign material from interfering with the function of the expansion joint or otherwise disrupting the structure as a result of seasonal temperature changes. Sealing compositions used for this purpose must have a high degree of plasticity, a high degree of adhesiveness for the concrete, and low temperature susceptibility, that is, lack of brittleness at low ambient temperatures and lack of excessive flow at high ambient temperatures. Jet-fuel-resistant joint sealing compositions additionally must retain these desirable characteristics of plasticity, adhesiveness, and temperature susceptibility after repeated contact with jet fuel.

While it is customary to use asphalt base compositions as joint sealers in ordinary pavements, such compositions have little, if any, value as joint sealers for runways and hangar floors in airports servicing jet planes because of their lack of resistance to jet fuels. it has been proposed, therefore to use plastic compositions compounded largely of synthetic rubbers. Such compositions, however, are expensive not only because of the basic raw materials used but also because they require special equipment such as high-horsepower mixers for their preparation.

It has now been found that joint sealing compositions meeting Army Air Force specifications for jet-fuel-resistant joint sealer compositions can be prepared in accordance with this invention by mixing a major portion of coal digestion pitch with a minor proportion of a high molecular weight vinyl chloride-vinyl acetate copolymer containing up to 15 of vinyl acetate and fluxing the mixture with sufiicient crystal-free tar heavy oil to give a cone penetration between 50 and 90 decimillimeters at 77 F. Compositions thus prepared are not only economical but conform to specification 686.61 issued July 8, 1952 (plus supplements) by the Ofiice of the Chief of Engineers, Department of the Army, titled Jet-Fuel- Resistant Joint Sealing Compounds for Airfield Pavements.

The term coal digestion pitc is applied in the tar industry to modified pitches made by digesting powdered bituminous coal in ordinary pitch and fluxing the mixture with tar heavy oil as required to give the properties desired in softening point and penetration and is so used herein. Coal digestion pitch is distinguished from ordinary pitch of like softening point by improved temperature susceptibility, that is, by being less brittle at low ambient temperature and resistant to flow at high ambient temperature. The improved temperature susceptibility of coal digestion pitch makes it particularly suitable for steep-roof coatings and like coatings where lack of brittleness at low ambient temperatures and resistance to flow .at high ambient temperatures are needed.

The term pitch as used herein and as understood in "ice the tar industry is intended to refer to a residue of tar distillation having a consistency ranging from that of heavy tar to that of hard pitch or semi-coke. Pitch, therefore, may be characterized as a residue of tar having a softening point of about 100 to 300 F. (Softening points given herein are by the ring and ball method unless otherwise specified.)

The term tar heavy oil is used herein to designate a tar fraction having not more than 1% distillate at 300 C. and between 18 and 25% distillate at 355 C. It also has a minimum specific gravity of 1.140, not more than 0.5% water, and not more than 1% benzol-toluol insolubles. By crystal-free tar heavy oil is meant a tar heavy oil containing less than 5% crystals at 25 C.

In forming coal digestion pitch, powdered bituminous coal is digested with pitch at a temperature of about 300 C. until a homogeneous dispersion of the coal in the pitch is obtained, and the product is fluxed to the desired softening point and penetration with tar heavy oil. Ordinarily the amount of coal ranges between about 20 and 25% and the relative amounts of pitch and heavy oil are adjusted according to the properties of the particular pitch and the particular heavy oil and according to the softening point and penetration desired in the product. Thus more tar heavy oil will be required to flux a coal digestion pitch prepared from a hard pitch than one prepared from a soft pitch. Ordinarily it is desirable to use soft pitches, that is, those having a softening point between about 100 and 200 F. especially as in the case of this invention where a coal digestion pitch having a softening point between 175 and 250 F. is desired. The

dispersion of coal in the soft pitch effected by the digestion raises its softening point high enough so that it can be fluxed back to the desired softening point by incorporating a suflicient quantity of the tar heavy oil.

The following compositions in which the parts are byv weight unless otherwise specified illustrate typical coal digestion pitches useful in preparing joint sealing compositions according to the invention:

Coal digestion pitch A digestion as required to give a product having a softening point of 220 to 240 F. and an ASTM penetration at 32 F. of 12 to 18 decimillimeters. In a typical case, 38 parts of heavy water-gas pitch (softening point 140 F.), 40 parts coke oven tar heavy oil, and 22 parts of powdered bituminous coal are thus processed to give a product having a softening point of 228 F. and an ASTM penetration at 32 F. of 12 decimillimeters.

Coal digestion pitch B The procedure of A is repeated substituting coal tar pitch for the water-gas tar pitch. The proportions are adjusted to give a softening point of 210 to 220 F. and an ASTM penetration at 77 F. of 9 to 12 decimillimeters. In a typical case, 40 parts of coal tar pitch (130 F. softening point), 35 parts of coal tar heavy oil, and 25 parts of powdered bituminous coal are thus processed to give a product having a softening point of 215 F. and an ASTM penetration of 11 decimillimeters at 77 F.

Coal digestion pitch C produced in situ (in the digestion step) from a tar distillate having the components of tar heavy oil plus some more volatile components. If desired, the pitch and part of the required heavy oil can be formed in situ because the temperature of the digestion being around 300 C. is

sufiiciently high so that when tar is used, the volatile com ponents are driven off leaving a mixture of pitch and heavy oil. The amount of coal ranges ordinarily from about 20 to about 25% though more or less is sometimes used and the amount of pitch and tar heavy oil are variable as already pointed out according to the nature of the pitch and heavy oil and the properties desired. Desirably, the pitch should have a softening point between 120 and 180 F. Softer pitches than these contain volatile components which are lost in the digestion and would not have been present in the pitch had the original tar distillation been carried out to give a pitch having a softening point of 120 F. or more. Harder pitches can be used also since it is only necessary to cut them back with more fluxing oil. They are undesirable, however, because additional expense is involved in preparing such pitches. While it is not practical in view of the multitude of factors involved to give particular proportions of pitch and tar heavy oil, the preferred pitches will ordinarily need from 4 to 9 parts of tar heavy oil for every 6 parts of pitch (usually in the neighborhood of l to l) in order to effect the desired fluxing.

Joint sealer compositions according to the invention are prepared by mixing coal digestion pitch, high molecular weight copolymer of vinyl chloride and vinyl acetate containing about 1 to about vinyl acetate, and crystalfree tar heavy oil at a temperature of 120-150 C. Lower temperatures can be used if sufficiently powerful mixers are available, but higher temperatures should be avoided if decomposition of the vinyl chloride copolymer is to be avoided. The vinyl chloride copolymer is kept as a minor component relative to the coal digestion pitch and ordinarily will range from about 5 to of the total composition and the relative proportions of crystal-free tar heavy oil and coal digestion pitch is adjusted to give products having the desired cone penetration. With the heavier coal digestion pitches, more crystal-free tar heavy oil is required to flux the resin-coal digestion pitch mixture and with the light coal digestion pitches, less is required. More or less crystal-free tar heavy oil, therefore, is added as needed to give a product having the desired cone penetration at 77 F. of 50-90 decirnillimeters. With the preferred coal digestion pitches, this will ordinarily range from about 1 to 2 parts for each part of coal digestion pitch. Some or all of the tar heavy oil required may be incorporated into the coal digestion pitch before the resin is added thereto, and in such cases, some or all of it may be added in the actual digestion of the coal.

When the tar heavy oil used for fluxing the resin-coal digestion pitch mixture contains substantial amounts of a material which crystallizes out at ordinary temperature, the crystals can be removed by settling and decanting, centrifuging, or other standard methods for separating crystals from liquids. The crystal content should be reduced to less than 5% crystals at C., because when oil containing 5% or more of crystals at 25 C. is used to flux the resin-coal digestion pitch mixture, blooming or efiluorescence may result when a joint seal is poured.

The vinyl chloride-vinyl acetate copolymer is a standard polyvinyl resin of commerce. The vinyl acetate content ranges from about 1% to about 15 By high molecular weight is meant, copolymers having an intrinsic viscosity in cyclohexanone of at least 1.1. A vinyl chloride-vinyl acetate copolymer containing 5% vinyl acetate and an intrinsic viscosity of 1.25 in cyclohexanone is typical and is advantageously used in the compositions of this invention.

The invention may be more fully understood by reference to the following examples in which the parts are by weight unless otherwise specified.

Example I Percent Coal digestion pitch 36 Vinyl chloride-vinyl acetate copolymerm 10 Coal tar heavy oil 54 The ingredients were mixed at 138 C. for rninutes. The product had a cone penetration of 88=deerm1llu11eters at 77 F., and a flow of zero at 140 F. and in other respects conformed with the standard specification for jetfuel-resistant joint sealing compounds.

Example II The coal digestion pitch used in this example is the same as that of the typical case of Coal Digestion Pitch A and the vinyl chloride-vinyl acetate copolymer is the same as in Example I. These ingredients are mixed and fluxed with coke oven tar heavy oil as in Example I to give a product having the following composition:

Per cent Coal digestion, pitch-.. 40 Vinyl chloride-vinyl acetate copolymer 10 Coal tar heavy oil 50 The product has a cone penetration of 87 decimillimeters at 77 F. and a how of zero at 140 F. and otherwise meets the standard specifications for jet-fuel-resistant joint sealing compounds.

Having thus set forth in the examples the best mode devised for carrying out the invention, it is to be understood that the invention is not limited thereto but that variations may be made in the processes and compositions disclosed without departing from the spirit and scope of the invention as set forth in the specification and claims.

The invention having been thus fully described and illustrated, what is claimed to be new and patentabie is:

l. A jet-fuel-resistant joint sealing composition consisting essentially of 5 to 20% of a vinyl chloride-vinyl acetate copolymer containing from 1 to 15% vinyl acetate and having an intrinsic viscosity in cyclohexanone of at least 1.1 and the balance coal digestion pitch and from about 1 to 2 parts of a crystal-free tar fraction having not more than 1% distillate at 300 C. and between 18 and 25% distillate at 355 C. for each part of coal digestion pitch to give a product having a cone penetration at 77 F. of from 50 to 90 decimillimeters.

2. A jet-fuel-resistant joint sealing composition comprising a mixture of a major proportion of coal digestion pitch and from 5 to 20% of high molecular weight vinyl chloride-vinyl acetate copolymer containing not more than about 15% of vinyl acetate and from 1 to 2 parts of a crystal-free tar fraction having not more than 1% distillate at 300 C. and between 18 and 25% distillate at 355 C. for each part of coal digestion pitch, said mixture having a cone penetration at 77 F. of from 50 to 90 decimillimeters.

3. A jet-fuel-resistant joint sealing composition comprising a mixture of a major proportion of coal tar coal digestion pitch having a softening point of from 210 to 220 F. and an ASTM penetration at 77 F. of from 9 to 12 decimillimeters and from 5 to 20% of a vinyl chloridevinyl acetate copolymer containing about 5% vinyl acctate and having an intrinsic viscosity in cyclohexanone of 1.25 and 1 to 2 parts of a crystal-free coke oven tar fraction having not more than 1% distillate at 300 C. and between 18 and 25% distillate at 355 C. for each part of coal digestion pitch, said mixture having a cone penetration at 77 F. of 50 to 90 decimillimeters.

4. The process of making a, jet-fuel-resistant joint sealing composition which comprises digesting a mixture of 20 to 25% powdered bituminous coal and a mixture of coal tar pitch and tar fraction having not more than 1% distillate at 300 C. and between 18 and 25% distillate at 355 C. at a temperature of about 300 C., said pitch having a softening point between and 200 F. and the amount of said tar fraction being sufficient to produce a coal digestion pitch having a softening point between 175 and 250 F.; blending with said coal digestion pitch from 5 to 20% high molecular weight vinyl chloridevinyl acetate copolymer containing 1 to 15% vinyl acetate at a temperature of -150 C. and fluxing the mixture with from about 1 to about 2 parts of a crystalfree tar fraction having not more than 1% distillate at 300 C. and between 18 and 25% distillate at 355 C. for each part of coal digestion pitch to give a product having a cone penetration at 77 F. of 50 to 90 decimillimeters.

5. The process of making a jet-fuel-resistant joint seal.- ing composition which comprises preparing a coal digestion pitch by digesting 20 to 25 of powdered bituminous coal the percentage being based on the coal digestion pitch and a mixture of coal tar pitch having a softening point of from 100 to 200 F. and a tar fraction having not more than 1% distillate at 300 C. and portions of about 1 to 2 parts for each part of coal dibetween 18 and 25% distillate at 355 C. in proportions gestion pitch to give a product having a cone penetration of from 4 to 9 parts of said far fraction for each 6 parts at 77 F. of S0 to 90 deeimillmeters.

of pitch, said digestion being continued at a temperature of {about 3001"1 C. unltil a homogeneous produetqis obtained; 5 References Cited in the file of this patent lending t e resu ting product with 5 to 20 0 of a high molecular weight vinyl chloride-vinyl acetate copolymer UNITED STATES PATENTS containing 1 to 15% vinyl acetate and crystal-free tar Number Name Date fraction having not more than 1% distillate at 300 C. 2,464,263 Rudd Mar. 25, 1949 and between 18 and 25% distillate at 355 C. in pro- 10

Claims (1)

1. A JET-FUEL-RESISTANT JOINT SEALING COMPOSITION CONSISTING ESSENTIALLY OF 5 TO 20% OF A VINYL CHLORIDE-VINYL ACETATE TATE COPOLYMER CONTAINING FROM 1 TO 15% VINYL ACETATE AND HAVING AN INTRINSIC VISCOSITY IN CYCLOHEXANONE OF AT LEAST 1.1 AND THE BALANCE COAL DIGESTION PITCH AND FROM ABOUT 1 TO 2 PARTS OF A CRYSTAL-FREE TAR FRACTION HAVING NOT MORE THAN 1% DISTILLATE AT 300* C. AND BETWEEN 18 AND 25% DISTILLATE AT 355* C. FOR EACH PART OF COAL DIGESTION PITCH TO GIVE A PRODUCT HAVING A CONE PANETRATION AT 77* F. OF FROM 50 TO 90 DECIMILIMETERS.