CA1047664A - Asphalt-based coating compositions - Google Patents

Abstract

ASPHALT-BASED COMPOSITIONS
ABSTRACT
A composition, especially useful for making coating compositions, and having unusually good properties, comprises at least one solvent extracted hard asphalt, at least one polyhydroxy polymer, and, optionally, at least one filler and at least one stable, non-volatile, tertiary amine catalyst.
This composition, where combined with at least one poly-isocyanate, forms a composition especially useful for coatings, particularly finish coatings.

Description

BACKGROUND OF THE INVENTION
The present invention relates to a composition, especially coating compositions; a substrate such as pipe coated therewith; and a precursor composition and precursor component for use in preparing the coating composition.
Pipelines, such as crude oil and gas pipelines, which are buri~ed in the ground are protected against deteriora-tion by providing the pipelines with a protective coating.
Such protective coatings are generally those prepared from an asphalt base. Although the presently available protective coatings have proved adequate when used for pipelines laid in the temperate and torrid zones of the world, they are not satisfactory in regard to their physical properties when used interchangeably either for pipelines laid in the frigid zones of the world where temperatures of -30F. to -65F. may be encountered, such as the northern slopes of Alaska, the :
Northern Territories of Canada and Siberia, where oil and gas deposits have been recently discovered, or for hot gas pipe-lines where temperatures of 200F. to 250F. are encountered downstream of compressor stations.

.~: .

:

76~ `
SUMMARY OF rHE BROAD EMBODIMENrS OF THE INVENTION
Accordingly, the principal object of this invention is to provide new compositions that are particularly useful as coatings and especially as finish coatings.
Another object is to provide substrates coated, at least partially, with the compositions of this invention, particularly where the com-positions form finish coatings on such substrates.
The precursor component comprises at least one solvent extracted hard asphalt having a penetration at 77F. of about 0 to about 10, pre-ferably about 0 to about 5,mm/10 as measured byASTM D-5-65, and a softening point of about 165F. to about 215F. preferably about 170F. as measured by ASTM D-36-70, and at least one intermediate polyhydroxy polymer having an average of at least about 1.8 predominantly primary, terminal, allylic hydroxyl groups per molecule that is an addition polymer of about 0 to about 75% by weight of an alpha-olefinic monomer of

2 to about 12 carbon atoms, and about 25% to 100% of a 1,3-cliene hydrocar-bon of 4 to about 12 carbon atoms, and having a viscosity at 30 C. of about 15 to about 5,000 poises, the majority of its unsaturation in the main carbon chain, and a number average molecular weight of about 400 to about 10,000. Preferably, the precursor component also comprises ~ ;
at least one mineral filler, including but not limited to fine mineral fillers. Preferably,the precursor component also comprises at least J one stable, nonvolatile tertiary amine catalyst. Advantageously,thQprecursor component comprises at least one mineral filler and at least ~
one stable, nonvolatlle tertiary amine. These compositions are sur- 1 -prisingly stable a-t standard temperature and pressure, and ha~e long shelf life, often sev~ral months or n~ore. it~
By contrast to air-blown or vacuum distilled asphall:s of comparable hardness, the asphalts of this invention are nc~n-air-b1Ovvn, 6~
and are prepared simply by solvent extr'actiOn. For example, these asphalts may be prepared by mixing an asphaltic flux or penetration grade asphalt with propane or a propane-C4 and/or propane-C5 hydro-carbon mixture and allowing the ingredients to separate into two layers. The solvent extracted asphalt is recovered from -the ~ottom layer. Particularly useful solverit extracted asphalts are those prepared from a residuum of South Arkansas crude oil, although other crude oils may be used. These asphalts constitute about fi0 to about 35, preferably - ~ .
about 70 to about ~5, and most preferably about 70 to about 80, percent by weight of the precursor component.
The intermediate' polyhydroxy polymer constitutes about 5 to about 40, preferably about 15 to about 30, and most preferably about 18 to about - 22% by weight of the precursor component of this inven~ion. These polymers are described in detail in U.S. Patent 3,637,558, columns 3,4 and S.
However, the ran'ges of viscosities and molecular weights of the polymers . .
suitable for use in the precursor component of this invention are those , .
set forth above, The most highly preferred polymer is a liquid (at STP) ' hydroxyl terminated polybutadiene resin, most preferably having a ~ . .
' molecular weight of about 2500. ' ~
.
- Generally" the mineral filler may be one kind or two or more ~ -different kinds o~ such fillers. Preferably, the Eiller is a finely divided ~` solid'with more than about 99% passing through a number 325 mesh , . . . .
~ screen. Examples of solid fillers are powdered limestone, pulverized ~ ~ ' ,. , ~ , , ~ , sand, silicas, clays, slate flour, and the like~ Where filler forms a pa~ of the precursor component of the invention, filler constitutes about ~' ' :
10 to about 29, preferably about 14 to about 24, and most preferably about 20% by weight of thè precursor component.
' The tertiary amine ~catalyst must be stable and nonvolatile for long periods, typically 24 hours or more, and at the processing temperatures -~ 3-. , , , ~. . , i . .
. .
: ' . . .

~7~
of about 300F. and higher at which these precursor components are employed. Amine catalysts cons~itute about 0.3 to about 2, preferably about 0 .5 toabout 1, percent by weiybt of the precursor component composition.
The precursor may be made by mixing asphalt and filler, where filler is added, and heating the mixture to a temperature sufficient to dispel a substantial q[uantity of air and moisture, generally about 400 to about 500F., and where necessary, adding one or more - desiccants. The asphalt/filler mixture is then cooled, if necessaryt to a temperature below which degradation of the other'ingredients is substantially avoided. Thus, the mixture may be cooled to about 400F., and mixed in a moisture-free environrnent with the intermediate poly-. .
hydroxy polymer. The mixture is cooled to about ~25F., and ~he tertiary amine, if any ls desired~ is added and mixed with the other ingredients to form the desired composition.
.
The precursor composition is especially useful ~or making compositions useful as coatings particularly finish coatings. These ; .................. , . . : . .
~ ' composïtions comprise the ingredients of the precursor composition .,. . . . . ~.
. plus at least one polyisocyanate,~preferably a diisocyanate, and ' more preferably a polyphenyXméthylene'polyisocyanate. The weight - ratio of the precursor to the polyisocyanate is determined by sub-stantially equalizing the sum of the reactivities of the polyhydroxy polymer in the precursor with the reactivity of the polyisocyanate.
In general, the w'eis~ht ratio of precursor to polyisocyanate is about . . .
25- 31 to 1 to about 61 to 1, preferably about 42 to 1 to about 52 to 1, ~ . .
and mos~ preferably about 50 to 1. ~ Upon mixing, the precursor and polyisocyanate react to produce a composition containmg at least - one urethane polymer, at least one solvent extracted asphaltand, optionally~, ' mineral filler and/or tertlary amine catalystv ' ' ~ ' .. . . . ' .:

-.
. ~ . , - .

The precurso~po~yisocyanate compositions of this invention are particularly useul for coating suhstrates, especially metal sub-strates such as metallic pipe. In particular, the coating is advantageous for applying finish coatings to such substrates as steel and aluminum pipe. Generally, the coating may be from about 20 to about 150, pre-Eerably about 50 to about 110, and most preferably about 80, mils in thickness and will contain about 5 to about 40 , preferably 15 to about 30 percent by weight urethane elastomer, and correspondingly, about 95 t Q about 60 , and preferably about 85 to about 70 percent by weight of solverit extracted asphalt, and, where desired, filler and/or tertiary amine. Surprisingly, these compositions produce coatings of high tensile strength and elasticity, yet are quite tough and hard.
The coating may be applied by conventional techniques such as spraying. The rate of cure increases as the temperature , of the precursor ~. increases. The precursor is best kept warm arid delivered to spray nozzles at about 330 F. or higher. Cure is accelerated by heating the coating at 150~. and higher after -application.

- SUMMARY OF TH~ PREFERRED EMBODIMENTS
; OF TH~ INVENTION

An object of the present invention is to provide a piPe .
coating;~composition and pipe coated th&rewith which will not only withstand the r~gorou~ low~temperature climatic conditions enoountered in the frigid zones of the world but will also withstand the elevated temperatures encountered in hot gas pipelines. A ~rther ~
object of the present invention is to provide a safe and effacious pre-cursor composition and precursor component for use in preparing the-pipe coatin~ composition.

The present invention thus provides an improved pipe coating . ~ ' ~ S : ' ' ' ' -' ,,, , , . - . ;

composition which comprises, in general, an asphalt, an in situ formed polyurethane elastomer, a filler and a catalyst, as well as pipe coated therewith. In addition, the present inVentiOn further provides a polyurethane~forming precursor composition and precursor component for use in preparing the improved pipe coating composition. The pipe coating composition possesses an unusual combination of physical properties not heretofore achieved which makes it ideally suitable for the coating of pipe to be laid under extremely cold climatic conditions or to 10 be used for hot gas pipelines. The polyurethane-forming pre-cursor composition and precursor component from which the pipe coating composition is prepared are suchthat the pipe coating composition can be prepared with safety and rapidity and without pollution by volatiles.
Thus, in accordance with the present teachings, a pipe line coating composition precursor component is provided ~ -~
which comprises a blend of from 50% to 95% by weight of at least one solvent extracted hard asphalt which has a penetration at 77F. o~ from 0 to 10 mm/10 and a softening point of from 165F, 20 to 215F. and from 5~ to 40% by weight of at least one intermediate polyhydroxy polymer which has an average of at least 1.8 predominantly primary terminal allylic hydro~yl groups per molecule, which is an addition polymer of from 0 to 75% by weight of an alpha-olefinic monomer of from 2 to 12 ; carbon atoms and from 25% to 100% of a 1,3-diene hvdrocarbon of from 4 to 12 carbon atoms, which has a viscosity at 30~C
of from 15 to 5,000 poises and which has the majority of its unsaturation in the main carbon chain and which has an average -~
molecular weight of from ~00 to 10,000.
In accordance with a further aspect there is provided a pipe line coating composition component which comprises a blend o 55% to 65% by weight hard asphalt, 18%
-6~

to 22% resin, 15% to 25% filler and from 0.5% to 1~ of a stable non volatile tertiary amine catalyst together with the poly-isocyanate in a weight ratio of from 31:1 to 61:1.
In accordance with a further aspect and more specifically a pipe line coating composition component is provided which comprises a blend of 60.5% by weight hard asphalt which has a concentration of from 0 to 5 and a softening : point of about 170F, 18.5% by weight of liquid hydroxyl-terminated polybutadiene resin which has a molecular weight of about 2,500, 20% by weight slate flour of less than 44~m and 1% by weight of methyl di-octadecylamine together with poly- .
isocyanate in a weight ratio of 50 DESCRIPTION OF THE PREFERRED EMBODIMENTS
The precursor component for use in preparing the pipe coating composition comprises a blend of (a) from about : 50~ to about 75%, usually from about 55~ to about 65%, and preferably about 60.5~, by weight of a solvent ex~racted hard :
asphalt having a penetration at 77~. of from 0 to 10 mm/10, prefera~ly from 0 to 5 mm/10 (ASTM D-5-65), and a softening point of from about 165F. to about 215F., preferably about 170F. (ASTM D-36-70), (b) from about 10% to about 30~, usually from about 15% to about 25%, and preferably about 20%, by weight :
of a fine mineral filler, such as minus 325 mesh slate flour .
or silica, (c~ from about 15~ to about 30%, usually from about 18% to about 22%, and preferably about 18.5~, by weight of a ~ :
liquid hydroxyl-terminated polybutadiene resin having a molecular weight of about 2500, such as the polyol resin R-45-~T of Arco*Chemical Company, and (d) from about 0.3% to about 2%, ::-usually from about 0.5% to about 1%, and preferably ahout 1%, `~
by weight of ~ stab~e, nonYolatile~ ter~iary amine catalyst, ~' . :"''. ' ', * Trademark ~ ~ 3 -6a-i ;~' ' 7~
* *
such as methyl di-octadecyl amine ~Armeen M2HT of Armak Company).
The low penetration or hard solvent extracted asphalt, rather than an ~air blown or vacuum distilled asphalt of comparable hardness, and tlle above resin are used to insure their compatibility or miscibility with one another and to achieve the unusual physical properties for the pipe coating. A tertlary amine catalyst which is stable and-nonvolatile at the lengthy (up to 2~ hours) processing temperature conditions of about 30ûF.-350F., rather than the unstable and volatile primary, secondary or tertiary amines, is used to insure safety and efficacy without pollution by volatiles and to provide a satisfactory rapid pro-cessing and curing period. The presence of a fine mineral filler i~nproves the physical properties of the pipe coating which would otherwise re-quire a firm outer wrap.
The above precursor component, referred to hereinafter as Component (1), is prepared by heating the-;asphalt~to about 400F.
and adding the filler while agitating the mixture. Some steam evolution ., .
occurs and entrapped air from the filler, so it is necessary to heat-and slowly stir the mixture for about 20-60 minutes to obtain a smooth mixture free of bubbles. The resin is then added. The temperature of the added resin and the temperature of the filler-asphalt mixture are adjuste:l or controlled so that the temperature of the resultant mixture thereof does not exceed about 350F. The mixture is agitated a few minutes to insure a uniform mixture and then the catalyst is added. ;`
ThP total mixture is stirred for about 20 minutes at above 300F. to aid in the removal of traces of moisture that may remain. It can then be pac:kaged in steel drums.
The precursor compositlon from which the pipe coating composi-~ion is prepared comprises the combination of a segrega~ed or iLndividual~y packaged two component system of the above Component (1) and a 7~ ;
.

.. . . * 'I`r~-lQm;~rlc , ', ~ 76~
Component (2), namely, a polyphenylmethylene polyisocyanate, such as Mondur MRS ~Mobay Chemical Company) or Papi (The Upjohn Company).
The weight ratio of Component (1) to Component l~2) in the two component system is determined by matching the reactivities of the hydroxylated resin (0.8 milliequivalents/gram) and the polyisocyanate (7.5 milli-equivalents/gram). Thus the weight ratio of Component (1) to Component (2) is from about 31:1 to about 61:1, usually from about 42:1 to about 52:1, and preferably about 50:1 .
The pipe coating composition of the invention comprises (a) `~
from about 49% to about 73%, usually from about 54% to abc)ut 6'1%, and preferably about 59%, by weight of a solvent extracted hard asphalt having a peneLration at 77F. of from 0 to 10 mm/10, preferably from 0 to 5 mm/10, ;
and a softening point of from about 165F. to about 215F., preferably about 170F., (b) from about 10% to about 29%, usually from about 14%
lS to about 24% and preferably about 20%, by weight of a fine mineral filler, such as minus 325 mesh slate flour or silica, (c) ~rom about 17% to about 32%, usually from about 18% to about 21%, and preferably about 20%, by weight of an in situ formed polyurethane elastomer which is the re-action product of a liquid hydroxyl-terminated polybutadiene resin having 2~ a molecular weight of about 2500 and a polyphenylmethylene polyisocyanate ., .

and (d) from about 0.3% to about 2%, usually from about 0.5% to about . :
1%, and preferably about 1%, by weight of a stable, nonvolatlle, tertiary amine catalyst, such as methyl di-octadecylamine. -~ ~: ~
The pipe coating compositlon is prepared ~rom its precursor 25 ~ composition containlng Components (1) and (2) and applied to steel ;
pipe in the following manner. The pipe to be coated is cleaned by shot blasting and warmed to about 150Fo ~ because the coating adheres ~ . . : :
better to warm steel than to cold steel. A primer, such as an aromatic solvent (xylene or toluene~ or an aromatic solvent containing equal weight * Trademark ~766~ ~-quantities OI a bitumen or aromatic tar and a high viscosity grade of chlorinated rubber, may be used and should be sprayed on the pipe a short time before application of the coating. Although the ~rimer may be dry to the touch, some retained solvent will improve the adhesion of the applied coating.
To apply the coating, Component (1) is heatPd to about 350F.
; and pumped in a steady proportioned flow into an inline rnixer. The small amount of Component (2) at about 80F. to about 120F. is also proportioned into the inlet of the inline mi~er vrhere it is thoroughly O mixed with Component (1) at about 3S0F. Once mixed, the mixture will gel to a very high viscosity n~ass within about 45 to about 65 seconds. Thus, the fresh mixture is immediately sprayed on the warmed pipe so as to have time to flow out smooth before gelling occurs and - also to thoroughly mix at the overlap edye with the coating already S sprayed on the pipe. Generally, the spray is applied in a spiral pattern by rotating the pipe while the spray unit moves down the plpe, or the pipe moves by the spray unit. It may be desired in many cases, due to the flexibili-ty of the coating, to apply a conventional pipeline Eelt or a polyethylene tape as an outer wrap to the coated pipe so as to impart greater skin resistance to the coating. In this case, the outer wrap is applied before gelling occurs.
To insure an advanced stage reaction well beyond the gelling ¦
' . : ~.
stage, the warm pipe (about 150F.) is removed from the coating operation on end hooks, or o~her supports, so as to remain warm for i about 20 minutes. It is then sprayed with cooling water and rolled onto the storage rackO Some reaction of the active ingredients will con,inue to occur for the next ~ew days, the compleie reaCtiOIl depending upon the storage temperature of the pipe.
The ~musual and highly deslrable combinatlon of physiccll ~1147~

properties possessed by the pipe coating composition of the invention are illustr~ted by the physical properties of the preferred pipe coating tabulated in Table I below. Th~ prefe~red pipe coating whose properties are set forth in Table I was made by reacting 48 to 50 parts of Component (1) with 1 part of Component (2) where Component (1) consists of 60.5%
by weight of solvent extracted asphalt having a penetration of 3-5 and a softening point of 168 F. to about 176F., 20%
by weight of -325 mesh slate flour, 18 . 5% by weight of a polybutadiene homopolymer having a viscosity of 50 poises at 30C., a hydroxyl 0' content of 0.95 milliequivalents per gram, a hydroxyl nu~nber (millieq. KOH/
gram) of 53, and average molecularweight of 2200 to 2500, about 2.1 to 2.2 predominantly primary, terminal, allylic hydroxyl groups, and an iodine number of 398 ~rco Chemical Company's R45HT), and 1% by weight of Armeen ~I2HT, a tertiary amine catalyst. Component (2) was the polyphenylmethylene polyisocyanate sold under the trade na~ne Papi -,, ~, (Upjohn Company). A typical analysis of this material is~
Isocyanate Equivalent (I~butylamineReaction) 133.5 Viscosity ~ 77F, C2ntipoises 250 Specific 5ravi~y 1 . 2 Flash Point, Çleveland Open Cup, F. 425 NCO Content by Weight, ~/O 31 . 5 ;

TEST VALUE -Hardness (Shore "A'~ at 77F. 45/55 Tensile Strength, 77F., lbs.j'in.2 180/220 Elongation at break, % 400/500 Impact Resistance ~A.S.T.M. G-14-72) Inch Pounds @ 77F. 35/45 ~ -@ 0F. 45/60 ~?-30F. -Low TemPerature (~rack (coated pipe exposed to -65~. temperature for 6 hours) No C~acks High Temperature lFlow (coated pipe exposed to 225F. temperature for 6 hours) l!Jo lFlc>w - Abrasion Resistance, 10 passes with sandblaster 2 No Loss of Coating Cathodic Disbonding, 7 days, in.
~AoS~T~M~ G-8-72) ` 0.10 0- . ~

7~6~ -From the above table, it will be noted that the pipe coating composition of the invention not only possesses unusually high re-sistance to low-temperature cracking and high temperature Elow, resistance to cathodic disbonding and resistance to low temperature impact damage, but also possesses unusually high tensile strength and elasticity. As a consequence, the pipe coating composition is capable of recovery from a deformed position caused by tension or compression. Thus, complete recovery occurs from a tension or com-pression distortion of 20% when the force is removed. Almost complete recovery occurs with much larger distortions, but severàl hours are required to do so.
The pipe coating composition of the invention, as noted above, is especially suitable for use on pipes in northern regions where the -coated pipes are often subjected to very low tempera-ures before they are welded and buried in the ground. The pipe coating is also useful Oll -hot gas pipelines. Because of the elastomer present in the coating, ``
it will resist higher temperature without slumping than conventional .
asphalt coatings, so it is useful f~or many pipelines in regions of more moderate temperatures. Since it is stronger than conventional asphalt ; 20 coatings, it is also useful in areas where soil stress is a problem in deforming the pipe coatings.
:
Althouyh the coating composition of the invention finds particular utility in the coating of steel pipe subjected to either very low temp-eratures or elevated temperatures, it can also be used in roofing membranes; in a liner for canals, irrigation and drainage ditches whlch are sprayed in place; as a coating for structurai steel and steel tanks; as a coahng for the protection OL insulation from the weather;
and as an adhesive for insulation.
Although, as mentioned above, the precursor composltion is ' ~J .

~., . - ~, . ~, , 76~

normally a combination or kit of a segregated or individually pac!cacJed two component system of Component (1) and Component (2), one could, if desired, subdivide the materials of Component ~1) into a number of individual packages, for example, a package containing the asphalt and filler and a package or packages containing the resin and~or catalyst, - provided care is exercised in proportioning or metering together the various materials to form either Component (1) or form the final coatirg composition.

1~ ' "... ' .: "
~ ' ' "'.

~15 '';.'~
;' ' , ' ~'.'~

a~
, : ' ' : .'

Claims (8)

The embodiments of the invention in which an exclusive property or privilege is defined as follows:

1. A pipeline coating composition precursor component comprising a blend of (a) from 50% to 95% by weight of at least one solvent extracted hard asphalt having a penetration at 77°F. of from 0 to 10 mm/10 and a softening point of from 165°F. to 215°F. and (b) from 5% to 40% by weight of at least one intermediate polyhydroxy polymer having an average of at least 1.8 predominatly primary terminal allylic hydroxyl groups per molecule, which is an addition polymer of from 0 to 75% by weight of an alpha-olefinic monomer of from 2 to 12 carbon atoms and from 25% to 100% of a 1,3-diene hydrocarbon of from 4 to 12 carbon atoms, which has a viscosity at 30°C.
of from 15 to 5,000 poises, which has the majority of its unsaturation in the main carbon chain and which has an average molecular weight of from 400 to 10,000.

2. The pipeline composition of claim 1 which includes from 10% to 30% by weight of mineral filler together with a polyisocyanate in a weight ratio of from 31:1 to 61:1.

3. The pipeline composition of claim 1 which includes from 0.3% to 2% by weight of stable, nonvolatile tertiary amine catalyst together with a polyisocyanate in a weight ratio of from 31:1 to 61:1.

4. The pipeline composition of claim 2 which includes from 0.3% to 2% by weight of stable, nonvolatile tertiary amine catalyst together with a polyisocyanate in a weight ratio of from 31:1 to 61:1.

5. The pipeline composition of claims 2, 3 or 4 wherein the polyisocyanate is in a weight ratio of from 42:1 to 52:1.

6. A pipeline coating composition precursor component comprising a blend of (a) 50% to 75% by weight hard asphalt and (b) 15% to 30% by weight of liquid hydroxyl-terminated poly-butadiene resin having a molecular weight of about 2,500 according to claim 1.

7. A pipeline coating composition component comprising a blend of (a) 55% to 65% by weight hard asphalt, (b) 18% to 22% resin, (c) 15% to 25% filler and (d) 0.5% to 1% catalyst according to claim 4.

8. A pipeline coating composition component comprising a blend of (a) 60.5% by weight hard asphalt having a penetration of from 0 to 5 and a softening point of about 170°F., (b) 18.5% by weight of liquid hydroxyl-terminated polybutadiene resin having a molecular weight of about 2,500, (c) 20% by weight slate flour of less than 44 µm and (d) 1%
by weight of methyl di-octadecylamine together with poly-isocyanate in a weight ratio of 50:1.