CA1303353C - Derivatives of polyether glycol esters of polycarboxylic acids as rheological additives for coal-water slurries - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE Coal-water slurries containing a rheological additive are disclosed. The rheological additives employed for the preparation of the present coal-water slurries are ester products obtained from the reaction of a poly-carboxylic organic acid with two or more hydroxylic compounds. Salts of these reaction products may also be employed. The rheological additive is employed in an amount from about 0.1 to about 4 percent by weight of the slurry, the slurry having from about 60 to about 80 percent by weight solids, the balance being water.

Description

~3~3~;3 DD-T

OF POLYCARBOXYLIC ACIDS AS RHEOLOGICAL
ADDITIVES FOR COAL-WATER SLURRIES
~his invention relates to a coal-water slurry 5 having a rheological additive which is the reaction product of a polycarboxylic organic acid and two or more hydroxylic compounds, one of which is necessarily a polyether glycol.
The ester reaction product is employed in an amount from about 0~1 to about~% by weight of the coal-water slurry, the slurry having from about 60 to about 80~ by weight of solids, the balance being water.
In recent years a great deal of interest has developed in utilizing coal-water slurries in lieu of oil for electric power generation not only because of the lower ~5 cost of coal but also because of its availability.
Coal-water slurries have been produced with solids contents of about 60 to about 75% which are fluid and handle in about the same way as petroleum fuels. These coal-water slurries may be burned directly without need of dewatering the mixture. The heat generated during combustion is sufficiently high so that the water in the slurry does not prevent it from being used to generate power. Naturally, as the solids of the coal-water slurry increase, the fuel value of the slurry also increases. For this reason, slurries having less than about 50 to 55~ solids are unsuitable primarily for economic reasons.
One of the difficulties encountered with coal-water slurries at a solids content of about 60% and higher is tha~ the dispersion of coal in water becomes an immobile mass and when burned it has to be handled in the same manner as lump coal. Handling in this respect includes not only .. .. . . .

~3V~3S~

transporta~ion of the coal from the mine source but also the delivery of the coal to a combustion chamber such as the firebox of a steam boiler. Unless coal-water slur-ries have the same liquidity as oil at these higher solids content so that they may be transported by pipe-line and injected into a firebox by spraying, the advan-tage of using a liquid carrier (i.e., water) for the coal is lost. Stated otherwise, the particles of coal in the slurry at these higher solids levels tend to lo convert the li~uid carrier (water) into a plastic mass whereby the advantage of employing a liquid carrier is lost.
The prior art has overcome some of these difficul-ties by providing additives which may be used in rela-tively small amounts to assure that the coal-water slurry at high solids content is fluid. Examples of these additives are given by Kovacs in U.S. Patent 4,435,306, Sakaria U.S. Patent 4,398,919 and in European Patent Application 0131558, published January 16, 1985.
20 Coal-fuel slurries containing a dispersing agent are also described by Schmolka et al. in U.S. Patent 4,288,232, Naka et al. U.S. Patent 4,251,229 and Shimizu et al. U.S. Patent 4,187,078.
, _ The present invention relates to coal-water slurries prepared using novel rheological additives comprising the reaction product of a polycarboxylic organic acid having from about 16 to 60 carbon atoms and from 2 up to 4 carboxyl groups selected from the group consisting of dimer acids, trimer acids, adducts unsaturated monocarboxylic acids or dimer acids with maleic anhydride in molar ratio of about 1:1, adducts of linoleic acid or similar unsaturated monocarboxylic acids with acrylic type acids in a molar ratio of about 1:1 and adducts of olefins having about 12 to about 40 carbon atoms with maleic acid or maleic anhydride in a ~3033S3 - 2a -molar ratio of 1:1 with (a) a polyether glycol having recurring oxyalkylene groups eontaining up to 4 earbon atoms and a molecular weight from about 1,000 to about 20,000 and (b) an organic hydroxylic aliphatie eompound having a molecular weight less than 1,000 and containing 1 to 2 hydroxyl groups. The .

~, .
^ ~

1 polycarboxylic acid has at least 55 percent up to essentially 100 percent of the available carboxyl groups reacted and the molar ratio of (a) to (b) ranges from about 4:1 to 1:4 and, more preferably, 2:1 to 1:2. The rheological 5 additive is employed in an amount from about 0.1 percent to about 4 percent and, more preferably, from 0.25 to 1.5 percent in slurries containing from about 60 to about 80 percent by weight solids.
PolycarboxyliC acids used for the preparation 10 of the additives of the invention are selected from the group consisting of dimer acids, trimer acids, adducts of unsaturated monocarboxylic acids or dimer acids with maleic anhydride in a molar ration of about 1:1, adducts of linoleic acid or similar unsaturated monocarboxylic 15 acids with acrylic-type acids in a molar ratio of about 1:1, and adducts of olefins having about 12 to about 40 carbon atoms with maleic acid or maleic anhydride in a molar ratio of about 1:1.
The polyether glycol (a) is selected from the group consisting of polyethylene glycol, polypropylene glycol, and poly(ethylene-propylene) glycol Polyethylene glycol having a molecular weight from abou 3,000 to 12,000 is particularly useful for the preparation of the rheological additives o~ this invention.
Especially useful hydroxylic compounds (b) are selected from the group consisting of n-decyl alcohol, 2-ethyl-1,3-hexanediol, dipropylene glycol, polyethylene glycol having a molecular weight from 200 to 600, polypropylene glycol having a molecular weight frcm 400 to 450, and 3 N-methyldiethanolamine.

,. , , -~3V3~

l The resulting ester products have more than55 percent and, more generally, greater than 75 percent of the carboxyl functionality reacted. In one embodiment of the invention, all or a portion of any remaining carboxyl 5 groups are converted to a salt formO Salts of ammonia and the group IA and IIA metals, especially sodium or potassium, are particularly useful for this purpose.
The rheological additives of this invention are predominantly ester products obtained by reacting a 10 polycarboxylic acid with a mixture of hydroxylic compounds.
One of the hydroxylic compounds is necessarily a polyether glycol of relatively high molecular weight while the second hydroxylic compound may be a lower molecular weight polyether glycol or another type hydroxylic material. The polycarboxylic 15 acid can be fully esterified or a portion of the carboxyl moieties can remain unreacted. In preparing the ester products, the polycarboxylic acid may be reacted with a mixture of the first polyether glycol and second hydroxylic compound or the esterification may be carried out in a 20 sequential, i.e., stepwise, manner. The complete or partial ester products of this invention are useful as rheological additives for coal-water slurries.
Po~ycarboxylic organic acids employed to obtain the ester products of the invention have from about 16 25 to about 60 carbon atoms, especially from 21 to about 54 carbon atoms, and from 2 up to about 4 carboxyl groups.
The acids may be either dimer acids, trimer acids, adducts of unsaturated monocarboxylic acids or dimer acids with maleic anhydride in a molar ratio of about l:l, adducts 30 of linoleic acid and similar unsaturated monocarboxylic acids with acrylic-type acids in a molar ratio of about -.

~3~33;~53 .

1:1, or adducts of olefins having about 12 to about 40 carbon atoms with maleic acid or maleic anhydride in a molar ratio of about 1:1.
Dimer acids are known in the art and described by Barrett _t al. in U.S. Patent 2,793,220 and Myers et al. U.S.__ _ __ Patent 2,955,121. Trimer acids are also known in the art and are described by Barrett _t al. in U.S. Patent 3,097,220 The dimer acid is obtained by oligomerizing an unsaturated 18 carbon atom naturally occurring unsaturated acyclic monocarboxylic fatty acid such as oleic acid, linoleic acid, linolenic acld and the like to obtain a 36 carbon atom dicarboxylic acid whereas the trimer acid is obtained by oligomerizing the foregoing unsaturated monocarboxylic acids to obtain a 54 carbon atom tricarboxylic acid. In both of these reactions, other products are obtained; however, the reaction is conducted in a manner so that the reaction product is principally the dimer acid or the trimer acid.
other un saturated acyclic monocarboxylic acids having at least one ethylenically unsaturated position and from about 10 to about 22 carbon atoms can also be used to make the polycarboxylic acids of the present invention ~hese include decenoic, undecenoic, pentadecenoic, hexadecenoic acids and the like. unsaturated acyclic monocarboxylic acids oE the above type may be obtained from natural fats and oils such a tall oil, linseed oil, tung oil, soy oil, rapeseed oil, corn oil, fish oil, beef tallow and mixtures thereof.
Dimer acid prepared as described in the foregoing references containing 75% or more o~ dimer acid is preferred whereas trimer acid prepared according ~o the foregoing 3~ references having 60% or more of trimer acids is preferred Mixtures of dimer acid and trimer acid are also useful and advantageously employed.
Adducts of maleic anhydride tor acid) with unsaturated monocarboxylic acids and dimer acids are known in the art and are described in U.S. patents 2,902,499 and .

3~333~S

2,975,133, These adducts are prepared by heating maleic anhydride and an unsaturated acid at a temperature from about 100C to about 300C until the addition reaction is completed, The molar ratio of the maleic anhydride to unsaturated acid is generally about 1:1.
A 21 carbon atom dicarboxylic acid designated Westvaco 1550 ~trademark~ may be employed as the polycarboxylic acid and comprises the addition product of an 18 carbon atom monocarboxylic unsaturated acid (linoleic lo acid) and acrylic acid. Equivalent unsaturated monocarhoxylic acids having at least two ethylenically unsaturated positions and from about 10 to about 22 carbon atoms reacted with an acrylic-type acid to produce a dicarboxylic acid may also be employed as the polycarboxylic acid. other acrylic-type acids which may be used include angelic acid, tiglic acid, senecioic acid, crotonic acid, isocrotonic acid, vinylacetic acid, methacrylic acid and the like and mixtures thereof.
The polycarboxylic acid can also be an adduct of maleic acid or maleic anhydride with an olefin, where the olefin has from about 12 to 40 carbon atoms and one or two unsaturated positions.

~3~13~

1 At least one polyether glycol, a higher molecular weight poly(lower oxyalkylene) glycol is reacted with the above-described polycarboxylic acids to obtain the reaction products of the present invention. The molecular weight 5 of the polyether glycol ranges from about 1,000 to about 20,000 and, more preferably, from about 3,000 to about 12,000. The recurring oxyalkylene groups contain up to about 4 carbon atoms and preferably have frorn 2 to 3 carbon atoms. Polyethylene glycol having a molecular weight from 10 about 3,000 to about 12,000 is particularly useful for the preparation of the rheological additives of the present invention, however, polypropylene glycol and poly(ethylene-propylene) glycols within the above-described molecular weight ranges are also useful.
The various polyether glycols noted herein may have either a broad or a narrow molecular weight distri-bution so lony as the molecular weight, on average, is within the aforementioned ranges. These ranges apply not only to polyether glycols falling within the range, but 20 also to polyether glycol mixtures having an average molecular weight within the aforesaid range. The commercial glycols employed according to the present invenLion are within the aforementioned molecular weight ranges and the molecular - weights thereof are average molecular weights. Some commercial 25 polyethylene glycols that may be employed according to the present invention have average molecular weights of 1000, 3350, 8000, and 20000 and are sold under the trademark Carbowax 1000, 3350, 8000 and 20000.
Lower alkoxy poly(lower oxyalkylene) glycols~
i.e., wherein one of the terminal hydroxyl groups is "capped"
with an alkyl group having from 1 to about 4 carbon atoms ~3~33S~
~ -8-1 may also be employed. These lower alkoxy poly(lower oxyalky~
lene) glycols also are within the molecular weigh~ range as defined above ~or the polyether glycols. The terminal hydroxyl group generally is "capped" with a methyl group, 5 such as methoxypolyethylene glycol.
Mixtures of the above-described polyether glycols may also be used.
The second organic hydroxylic compound, which can be combined with the polyether glycol and reacted with the polycarboxylic acid or reacted separately therewith, is an aliphatic compound having a molecular weight less than 1000 and may contain one or two hydroxyl groups.
Compounds having higher hydroxyl functionality can also be utilized, but preferably only as a por-tion of the total charge, where precautions are taken to minimize polymer formation via polycondensation. Useful hydroxylic compounds of the above types include aliphatic monohydric alcohols having from 3 to 22 and, more preferably, 6 to 18 carbon atoms; aliphatic dihydric alcohols having from 3 to 20 and, more preferably, 3 to 12 carbon atoms; either diols, including polyether diols, having from 4 to 40 carbon atoms and from 1 to 20 et-her moieties; and alkanolamines having 1 to 3-hydroxyl groups and 2 to 12 carbon atoms.
The various aliphatic monohydric alcohols that may be employed according to the present invention include isopropyl, n-propyl, n-butyl, 2-ethylhexyl, n-decyl, and cetyl alcohols or the like. ~liphatic dihydric alcohols may include butylene glycol, hexylene glycol, 2-ethyl-1,3-hexane diol and the like. Useful ether diols include diethylene glycol, dipropylene glycol, dibutylene glycol, polyether diols having average molecular weights less than 1,000 including triethylene glycol, tetraethylene glycol and ; 35 ~3~33S3 ,. g l appropriate higher homologs thereof.
Representative alkanolamines which can be employed include monoethanolamine, diethanolamine, triethanolamine, N-methyl ethanolamine, N-ethyl ethanolamine, N-methyl diethano-5 lamine, N-ethyl diethanola~ine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, N-aminoethylethanolamine and the like. Polyglyco amines, such as H-163 manufactured by Union Carbide Corporation, can also be employed.
In addition to the above-described hydroxylic 10 compounds, acyclic ester diols having a molecular weight of from about 150 to about 400 may also be employed. Esterdiol ~04 ~trademark), a diol ester having a molecular weight of 204 may be employed in this respect. Esterdiol 204 is a commercial designation for the monoester of neopentyl 15 glycol and 2,2-dimethyl-3-hydroxy propanoic acid. Hydroxy acids, such as ricinoleic acid and glycolic acid, may also be useful.
The rheological additives of the present invention are reaction products of the aforementioned polycarboxylic acids, a higher molecular weight polyether glycol and a second hydroxylic compound and are produced in accordance with conventional esterification procedures. For the esteri~
fication, all of the reactants may be added to the reaction as a unit charge and reacted or the polycarboxylic acid can first be partially reacted with the polyether glycol and then, in a subsequent step, the remaining unreacted carboxyl groups can be esterified with the second hydroxylic compound. In the latter type reaction, i.e., sequential reaction, the two steps may be carried out under different conditions. Polymerization is avoided or minimized by controlling the degreeof reaction and the molar ratio of '.: . :
.

~L3V3353 1 reactants. While an effort is made to react virtually all of the carboxyl functionali-ty of the polycarboxylic acid, some unreacted hydroxylic compound and carboxylic acid can remain in the reaction product and is not removed.
The acid value (AV) is generally used to determine the extent of reaction. At least 55% and up to 100% of the available carboxyl functionality is reacted as measured by the acid value of the final product versus the acid value of thé reactant mixture. Generally, more than 55%
10 of the carboxyl groups are reacted except possibly in the case where the polycarboxylic acid is a tetracarboxylic acid. More usually, when di- and tricarboxylic acids are used, 75% or more of the carboxyl functionality is reacted with the polyether glycol and second hydroxlyic compound.
15 In a particularly useful embodiment of the invention, 90%
or more of the carboxyl groups of the polycarboxylic acid are reacted. The ratio of polyether glycol to second hydroxylic compound can range from about 4:1 to 1:4 but is more generally from about 2:1 to 1:2, on a molar basis.
In another embodiment o~ the invention, all or a portion of any remaining carboxylic acid groups are converted to a salt form. These salts are also useful as rheological additives. Salts of ammonia and the Group IA or Group IIA Metals of the Periodic Table of the Elements, 25 especially sodium or potassium, are particularly useful.
The salts may be formed by reacting the ester containing free carboxyl groups with the hydroxides of the aforemented metals or with ammonium hydroxide in an arnount from about 50% to about 100% of the free carboxylic acid groups.
3o ~3V~33~

1 ~alts may also be obtained from alkanolamines or heterocyclic nitrogen compounds having up to about 10 carbon atoms and 1 or 2 nitrogen atoms by reacting with the alkanolamine or heterocyclic nitrogen compound in a 5 conventional manner. Various heterocyclic nitrogen compounds that may be employed comprise pyridine, piperidine,! piper-azine, morpholine, and alkyl-substituted imidazolines.
Useful alkanolamines include ethanolamine,~ diethanolamine,, triethanolamine and the like. In the case of alkanolamines,, I0 a portion of the alkanolamine may be reacted and serve as the second hydroxylic moiety,! and a portion may be associ-ated in sal~ form.
Especially advantageous rheological stabiliæers of the invention are:
I. Esters of a dimer acid wherein approxlmately one-half of the carboxyl groups are esterified with a poly-ethylene glycol having a molecular weight from about 3,000 to about 12,000,~ and all or a portion of the remaining carboxyl groups are reacted with a hydroxylic co~pound selected from (a) n-decyl alcohol, (b) 2-ethyl-1,,3-hexanediol,, (d) dipropylene glycol, (d) polyethylene glycol having an average molecular weight from 200 to 600,, (e) polypropylene glycol having an average molecular weight from 400 to 450, and (f) N-methyl diethanolamine;
II. Esters of trimer acid wherein approximately one-third to two-thirds of the carboxyl groups of the trimer acid are esterified with a polyethylene glycol having a molecular weight from about 3,000 to about 12,000 and all or a portion of the remaining carboxyl groups are reacted 3 with an alcohol or diol (a)-(f) as defined above for I;

~3~3~ii3 III. Esters o~ a polycarboxylic acid which is essentially a 1:1 adduct of dimer acid with maleic acid or maleic anhydride wherein approximately one-quarter to three-quarters of the carbo~yl groups are esterified with a polyethylene glycol having a molecular weight o~ about 3,000 to about 12 ,000 and all or a portion of the remaining carboxyl groups are reacted with an alcohol or diol (a)-~f) as defined above for I; and IV. Ammonium, alkali metal and alkanolamine salts lo of I, II and III.
The coal-water slurries of the present invention are made from pulverized or powdered coal which has a particle size such that about 60~ to about 90~ will pass through a 200 mesh U.S. standard screen (a 75 micron sie~e).
powdered or pulverized coal that may be converted into a water slurry is generally described by Funk in U.S. patents 4,282,006 and 4,416,666. The mixing of the powdered coal with water to form a slurry is also described by Funk in U.S.
Patent 4,477,260 at column 21 The rheological additives of the present invention are combined with water and the water in turn is mixed with the coal in a mixer such as a ~obart (trademark) mixer or the various art known equivalents thereof.
The coal slurry is made by adding about 0.1% to about 4% and, more preferably, 0.25 to 1.5% by wei~ht, based on total slurry, of the rheological additive as defined herein to the water used in the coal-water slurry to form a coal-water slurry having anywhere from about 60 to about s~l3 .
.

~3~3~

1 80% solids by weight. By use of the rheological additives of the present invention the slurries are liquid at room temperature and easily pourable. Without the ad~itives, the coal-water slurry is a non-pourable mass that,! at room 5 temperatures is solid. The slurries containing the rheolo~ical additives of the present invention should be maintained from about 0C up to about 95C preferably from about 2C
to about 75C and most preferably less than 50C.
The following Examples are illustrative.

EXAMPLE I
A mixed ester was prepared utili~ing polyethylene glycol having an average molecular weight of 3350 (PEG
15 3350) ~! dipropylene glycol and dimer acid. The dimer acid was a dimerized linoleic acid produced by Emery Chemicals (AV 189-197; SV 191-199; dibasic acid 77%). For the reaction,;
176.7g (0.6142 equivalents) dimer acid and 1028.8g (0.6142 equivalents) PEG 3350 were charged to a two-liter four-neck round bottom flask equipped with nitrogen inlet tube,! thermometer,~
and water trap. The reaction was run at 200C for 11 hours resulting in a drop in acid value of from 28.5 for the starting blend to 15.8.
2~0.9g (0.0617 equivalents) of the resulting partial ester and 9.1g (0.0678 moles) of dipropylene glycol were combined in a 500ml four-neck round bottom flask equipped with subsurface nitrogen, thermometer and water trap.
This reaction mixture was heated to 225C for 6.5 hours.
When approximately half of the available carboxyl functionality 3 was reacted (acid value 8.8),, heating was terminated and the reaction was allowed to cool.

~3~3~

1 The mixed ester product thus obtained was evaluated as a rheological additive as follows: 1.75g of the mixed ester product was dissolved in 62.2 grams o~ tap water with 0.18g commercial defoamer and 4.38g of a 1% aqueous 5 solution of xanthan gum and 0.5% formaldehyde in the bowl of a Hobart mixer. The rnixer bowl was then charged with 177.0 grams of freshly milled low-ash, low-sulfur Kanawha County West Virginia bituminous coal. This coal 98.8%
dry matter was milled to 98.3% smaller than 50 mesh (300 10 microns), 73.7~ smaller than 200 mesh (75 microns~, 61~1%
smaller than 325 mesh (45 microns). The coal had an ash content of 7.14% and sulfur content of 0.65% dry basis.
The dispersant, additives and coal were allowed to rnix at low speed (No. 1) for approximately 1 hour. Small water additions were made to account for evaporative losses.
The coal-water slurry was transferred to an 8-ounce bottle for viscosity determination using a srookfield Viscometer LVF with a Helipath stand adaptor and an F spindle.
Viscosity readings were made over a two inch volume of the slurry and averaged. The Broo~field viscometer was also used to measure a series of conventional viscosities using a number 4 spindle without the Helipath stand. Solids content of -the slurry was determined by evaporation of water from a weighed portion of the slurry and found to be 72.3% solids. pH was determined with a Cole Parmer pH Wand as 5.4. The viscosity at 6 rpm using the Helipath stand was initially 7000 cP and 1250 cP at 60 rpm by conven-tional determination. After 7 days no separation or settling was observed. The viscosity after 7 days was 14,800 cP
at 6 rpm with the Helipath stand and 1400 cP at 60 rpm by conventional means.

q?3353 EX~MPLE I I
In a manner similar to that of Example I I PEG
3350 and dipropylene glycol were reacted with a commercial polybasic acid having an average carboxyl functionality 5 of approximately three obtained from the addition of dirner acid and maleic anhydride. Approximately one-half of the carboxyl groups of the polycarboxylic acid was esterified with PEG 3350 and approximately one-half esterified with dipropylene glycol. For the reaction, 238.7g (1.0562 equiva-10 lents) of the polybasic acid and 1769.7g (1.0562 equivalents)PEG 3350 were charged to a 3 liter four-neck round bottom flask equipped with nitrogen inlet tube, thermometer and water trap and reacted at 210C for 5 hours until the acid value dropped from 29.6 ~o 15.8.
125g (0.0330 equivalents) of the above partial ester were transferred to a 500ml four-neck round bottom flask and 4.9g (0.0363 equivalents) o~ dipropylene glycol charged thereto. The reaction rnixture was heated to 225C
îor 9.5 hours resulting ln a further drop of acid value 20 from 15.5 to 8.8.
To a Hobart mixer bowl were charged 1.75 grarns of the above-prepared dispersant, '~.38g of a lgo aqueous solution of xanthan gum with 0.5% formaldehyde, 0.18g defoamer and 62.19g tap water. The dispersant was allowed to dissolve 25 and 177.0g (98.8~d dry matter) low-ash, low-sulfur Kanawha West Virginia bituminous coal added. The dispersant, additives and coal were allowed to mi~ at low speed (No. 1) for appro~i-mately 1 hour. Small adjustments were made to account for evaporative losses.
3o --~ iL3~3335;~

1 l~he slurry was transferred to an 8-ounce bottle and viscosity determinations were made as previously described above. The solids content of the slurry was determined to be 72.3~ and pH was initially found to be 5.4. The 5 viscosity at 6 rpm with the Helipath stand was initially 4700 cP and 1050 cP by conventional methods at 60 rpm.
After 7 days' storage,, no separation of settling was observed and the viscosity was found to be 8600 cP at 6 rpm with the ~elipath stand 1150 cP by conventional methods at 60 10 rpm.

EXAMPLES III - VIII
Following the procedure of Example I,, the partial dimer-PEG 3350 ester prepared therein was reacted with 15 a series of different hydroxylic compounds. For each reaction,, 1.1 mole of the hydroxylic compound was charged and reacted as described for each 1.0 equivalent (1 molar on average) of carboxyl present in the partial ester as follows:

Example No. Hydroxylic Com~ound Final AV
III n-decanol 7.35 IV n-decanol 3.2 V polypropylene glycol (Avg. MW 425) 8.32 VI pol~propylene glycol (Avg. MW 425) 3.3 VII N-methyl diethanolamine 2.8 VIII 2-ethyl-1,3 hexanediol 8.6 3o ~3~3~

1 Slurries were prepared from 1~ (based on coal weight) of each of the above dispersants with the Kanawha West Virginia coal and supplemental additives as previously deseribed.
Viscosity determination was made as previously described with the following results:

Viscositv in cP
Dispersant Inltial 1~ Day Storage of % 6 rpm 60 rpm 6 rpm 60 rpm Example -Sclids HeliDath Conventional Heli~ath Conventional . . _ 10III 72.5 ,~00 1,000 11,700 1,450 IV 72.6 9,400 1,100 10,100 1,000 V72.2 8,600 1,100 10,900 1,300 VI 72.5 10,900 1,350 10,100 1,400 VII 72.5 7,800 950 11,200 1,200 VIII 72.5 9,400 ~00 8,600 1,500 15 All o, the a~ove slurries were stable during storage.
EXAMPLE IX
A mixed ester of trimer acid (trimerized linoleic acid produced by Emery Chemicals; AV 175-192; SV 192-200;
tribasic acid 80-o ) with polyethylene glycol and polypropylene 20 glycol was prepared and evaluated as a dispersant for coal-water slurries. The mixed ester was prepared by first reacting 184.8g (0.609~ equivalents) trimer acid with 1020.7g (0.6094 equivalents) PEG 3350 as previously described at 200C
for 8.5 hours until a drop in acid value of from 28.4 to a 15.1 was achieved.
181.3 grams (0.0460 equivalents) of the resulting partial ester product were then reacted with 19.6g (0.0460 moles) of polypropylene glycol (avg. MW 425) at a temperature of 225C for 14.5 hours. The final product had an AV of 3 0.18 and was an effective rheological stabilizer for a coal slurry prepared from pulverized bituminous eastern Kentucy coal.

' EXAMPLES X--XIV
A series of mixed esters w~re prepared using the general sequential reaction p~ocedure previously described and the resulting products evaluated as rheological additives 5 for the preparation of coal-water slurries. The various polycarboxylic acids and hydroxylic compounds used for the reactions as well as the approximate amount of total carboxyl functionality reacted with teach hydroxylic compound were as follows:

Example Polycarbo~ylie Hydroxylie ~lo. Aeid Com~our.ds .
X Dodecenylsueeinic PEG 3350 (50%) Anhydride PPG 425 (50%) XI Dimer Acid PEG 6000 (50Sc) Dipropylene Glycol (50~) XII Acrylie Acid/Linoleic PEG 3350 (50~) ~cid Adduct (1:1) Dipropylene Glycol (25%) XIII Dimer Acid/Maleie PEG 8000 (67%) Anhydride Adduet (1:1) N-methyl diethanolamine (33 G ) A11 of the above-described mixed ester products 25 were effeetive rheologieal additives and produeed stable mobile coal-water slurries with pulverized eastern Kentucky bituminous low-sulfur (~1%) coal. For example,, a coal-water slurry (70~ eoal solids) containing 0.7 weight pereent of the mixed ester produet of Example XI and 29.3 percent 3 water had an initial viseosity 24,,000 cP as measured at 6 rpm (Spindle F) using a Brookfield Viscometer LVF with a Helipath stand adaptor.

~ . . ..

Claims (16)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED
AS FOLLOWS:

1. A coal-water slurry having a rheological additive comprising the reaction product of a poly-carboxylic organic acid having from about 16 to 60 carbon atoms and from 2 to 4 carboxyl groups selected from the group consisting of dimer acids, trimer acids, adducts of unsaturated monocarboxylic acids or dimer acids with maleic anhydride in a molar ratio of about 1:1, adducts of linoleic acid or similar unsaturated monocarboxylic acids with acrylic type acids in a molar ratio of about 1:1 and adducts of olefins having about 12 to about 40 carbon atoms with maleic acid or maleic anhydride in a molar ratio of 1:1 with (a) a polyether glycol having recurring oxyalkylene groups containing up to 4 carbon atoms and a molecular weight of from about 1,000 to about 20,000 and (b) an organic hydroxylic compound having a molecular weight of less than about 1,000 and containing 1 to 2 hydroxyl groups; said polycarboxylic acid having at least 55 percent to essen-tially 100 percent of the available carboxyl groups reacted and the molar ratio of (a) to (b) ranging from about 4:1 to 1:4.

2. The coal-water slurry of claim 1 wherein the rheological additive is present in an amount from about 0.1 percent to about 4 percent.

3. The coal-water slurry of claim 2 which contains about 60 to about 80 percent solids by weight and 0.25 to 1.5 percent rheological additive.

4. The coal-water slurry of claim 3 wherein the coal has a particle size such that about 60 percent to about 90 percent will pass through a 200 mesh U.S.
standard sieve.

5. The coal-water slurry of claim 4 wherein the temperature of the slurry is maintained over a range from about 2°c to about 75°C.

6. The coal-water slurry of claim 1 wherein (a) is selected from the group consisting of polyethylene gly-col, polypropylene glycol, and poly(ethylene-propylene) glycol and (b) is selected from the group consisting of aliphatic monohydric alcohols having from 3 to 22 carbon atoms, aliphatic dihydric alcohols having from 3 to 20 carbon atoms, ether diols having from 4 to 40 carbon atoms and from 1 to 20 ether moieties, and alkanolamines having l to 3 hydroxyl groups and 2 to 12 carbon atoms.

7. The coal-water slurry of claim 6, wherein the polycarboxylic acid has 75 percent or more of the car-boxyl functionality reacted.

8. The coal-water slurry of claim 7 wherein the polyether glycol (a) is a polyethylene glycol having a molecular weight from about 3,000 to about 12,000.

9. The coal-water slurry of claim 8 wherein 90 percent or more of the carboxyl groups of the polycar-boxylic acid are reacted.

10. The coal-water slurry of claim 9 wherein the molar ratio of (a):(b) ranges from 2:1 to 1:2.

11. The coal-water slurry of claim 9 wherein the rheological additive is an ester of dimer acid having approximately one-half of the carboxyl groups esterified with a polyethylene glycol having a molecular weight from about 3,000 to about 12,000 and all or a portion of the remaining carboxyl groups reacted with a hydroxylic compound selected from the group consisting of n-decyl alcohol, 2-ethyl-1,3-hexanediol, dipropylene glycol, polyethylene glycol having a molecular weight from 200 to 600, polypropylene glycol having a molecular weight from 400 to 450, and N-methyldiethanolamine.

12. The coal-water slurry of claim 9 wherein the rheological additive is an ester of trimer acid wherein approximately one-third to two-thirds of the carboxyl groups are esterified with a polyethylene glycol having a molecular weight from about 3,000 to about 12,000 and all or a portion of the remaining carboxyl groups are reacted with a hydroxylic compound selected from the group consisting of n-decyl alcohol, 2-ethyl-1,3-hexanediol, dipropylene glycol, polyethylene glycol having a molecular weight from 200 to 600, polypropylene glycol having a molecular weight from 400 to 450, and N-methyldiethanolamine.

13. The coal-water slurry of claim 9 wherein the rheological additive is an ester of a carboxylic acid which is essentially a 1:1 adduct of dimer acid with maleic acid or maleic anhydride wherein approximately one-quarter to three-quarters of the carboxyl groups are esterified with a polyethylene glycol having a molecular weight of about 3,000 to about 12,000 and all or a por-tion of the remaining carboxyl groups are reacted with a hydroxylic compound selected from the group consisting of n-decyl alcohol, 2-ethyl-1,3-hexanediol, dipropylene glycol, polyethylene glycol having a molecular weight from 200 to 600, polypropylene glycol having a molecular weight from 400 to 450, and N-methyldiethanolamine.

14. The coal-water slurry of claim 1 wherein all or a portion of any unreacted carboxyl groups of the rheo-logical additive are converted to a salt form.

15. The coal-water slurry of claim 14 wherein the salt is a salt of ammonia, a Group IA or IIA metal, an alkanolamine or a heterocyclic nitrogen compound con-taining up to about 10 carbon atoms and 1 or 2 nitrogen atoms.

16. The coal-water slurry of claim 15, wherein the salt is a salt of ammonia, sodium or potassium.