CA1037891A - Poly (n-alkylacrylate) compounds - Google Patents

Abstract

POLY(n-ALKYLACRYLATE) COMPOUNDS

ABSTRACT OF DISCLOSURE

A method of preparing an interpolymeric poly(n-alkylacrylate) of a molecular weight between about 3000 and 100,000 useful as a pour depressor in petroleum fractions comprising under polymerization conditions periodically introducing free radical polymerization catalyst via multiple time spaced additions in a heated initial mixture of n-alkyl-acrylate monomers, the polymerization being continued until a poly(n-alkylacrylate) is obtained having a molecular weight between about 3000 and 100,000, said initial mixture composed or n-alkylacrylate monomers wherein the alkyl distribution is or at least 18 carbons at least 70 wt. % of said alkyl is of C20 to C24 n-alkyl consisting of between about < and 65 wt. %
of C20 n-alkyl, between about 18 and 65 wt. % C22 n-alkyl and between about 8 and 35 wt. % C24 n-alkyl; the product resulting from said method and a hydrocarbon fraction containing between about 4 and 15 wt. % macrocrystalline paraffin wax having incorporated therein a pour depressing amount of said poly(n-alkylacrylate) product wherein said poly(n-alkylacrylate) is initially introduced into the petroleum fraction at a tempera-ture above a substantial portion of said wax.

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Description

BACKGROUND OF INVENTION

Tnis invention relates to a metho~ of produclng improved novel interpol~meric poly(n-alkylacrylate) pour depre6sor, to the pour depressors per se and to wax con-- taining petroleum fractlons of reduced pour point having `
incorporated therein a pour depressing amount of sald pour depressor . , - .:. -, .
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Heavy wax petroleum fractions, e.g., residual fuel oils, lubricating oil, crude oils and vacuum gas oils 10 having a pour point between about 40 and 1~0F. and a macro- ; -crystalline paraffin wax content aDove 4 wt. % often requlre the use of additives when employed in "cold climates" or exposed to low temperatures to maintain their fluidity or to meet critical pour point speclfications. Additives that are effective for this are called pour depressors. The art dis-closes numerous classes of pour depressors. One of the most ef~ective pour depressors found in significantly reducing s~
the pour of macrocrystalline wax containing heavy petroleum fractions are the interpolymeric poly(n-alkylacrylate) of a - 20 molecular weight-between about 3000 and 100,000 wherein the alkyl portion is of at least 18 carbons and at least 70 wt. -% of the alkyl is of Detween 20 and 24 carbons incluslvely, the C20 to C24 alkyl group containing between aDout 2 and 6~ wt. % of C2U alkyl, between about 18 and 65 wt. % C22 `~
alkyl, and between about 8 and 35 wt. ~ C24 alkyl and was prepared employing a free radical polymerization catalyst -which i6 added in a si le addition at the initiation of polymerization.
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1~37~1 Although the aforementioned prior poly(n-alkyl-acrylate) is a superior pour depressor, thare is a contlnuing ; search for still further lmproved pour depressors, that is, a maximized pour depression for a given adaitive quantity.

SUMMARY OF INVENTION
have discovered and this constltutes my inven-. ,.
tion a novel method for producing poly(n-alkylacrylate) -~ pour deprecsors which results in a novel pour depressor of improved pour depressing properties and improved pour de-pressed waxy petroleum fractions. More specifically, my invention pertains to the dlscovery tnat in the free radical catalyst polymerization preparation of poly(n-alkylacrylate) multlple time-spaced addltions of catalysts in the polymeri-zation as opposed to a single addition of equal catalyst quantity produces a final polymer product of a molecular -~
distribution substantially different from the molecular distribution of the poly(n-alKylacrylate) produced from a single catalyst addition and wherein the former has superior pour cepressing properties over the latter. It lS theorized the multi-addition molecular distribution more effectlvely interferes with or alters the growtn of paraffin crystals in the petroleum fraction to be pour depressed and thus more effectively lowers the pour point o~ the waxy petroleum fractions. I
.' DETAILED DESCRIPTION OF THE INVENTION
The method of the invention comprises first form-ing a mixture of n-alkylacrylate monomers prepared through ':
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the reaction of acrylic acid with n-alkanol mlxtures wherein the reactive n-alkanols have at least 18 carbons and 70 wt. % thereof in the alkanol group of from 20 to 24 car-bons, sald group consisting of between about 2 and 65 wt. %
of eicosanol, between about 18 and 65 wt. % docosanol and between about 8 and 35 wt. % tetracosanol. A standard means -can be employed to produce the poly(n-alkylacrylate) monomer 3~. .
reaction mixture, namely, by reacting (esterifying) the aforementioned alcohol mixture with acrylic acid ln the presence of an esterification catalyst such as p-toluene- -sulfonic acid and a polymerization inhibitor, e.g., hydro-quinone, desirably in the presence of an azeotroping agent for water by-product removal such as benzene. Esterification is conducted, for example, at a temperature between 85 and 95C. and is continued until the amount of water by-product is removed as overhead indicates that esterification is . ~-- ~ - .
essentially complete. The resultant product is a mixture of i n-alkylacrylate monomers and the alkyl distribution therein : .
is the same as the alkyl distribution in the alkanol reactant.
In the preparation of the interpolymer poly(n-alkylacrylate), the aforedescribed n-alkylacrylate monomer mlxture ls optlonally diluted with an inert organic solvent such as benzene, toluene, xylene or petroleum naphtha, pre-ferably greater than about 40 wt. % solution. The diluted or preferably undiluted monomer mixture is then heated to a temperature of between about 60 and 120C., advantageously under a blanket of inert gas such as nitrogen to prevent undesired oxidative side reactions and preferably employing agitation such as stirring or bubbling nitrogen gas through the reaction mixture. During the period of the reaction .~ .

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free radical polymerizatlon catalyst is lntroduced ln at least two separate time spaced additions and up to 10 or more spaced additions, preferably between about 3 and 5 additlons, ~- advantageously each catalyst additlon belng essentially equal or greater than any subsequent addition in amount.
Under preferred conditions, when the polymerization essenti-ally ceases following a catalyst addition as indicated by a levellng off of the refractive index the next catalyst addi-tion is in order. The polymerization reaction period after the last catalyst addition is normally continued until the refractive index remains essentially constant~ that is, +
1.5 units in the fourth decimal, the refractive index being taken at periodic intervals. Normally, the polymerization period ranges between about 1.0 and 15 hours, preferably between about 1.5 and 7 hours.
- At the end of the polymerization period, the inert solvent, if employed, is removed by distillatlon otherwise no further workup of the interpolymer product is generally necessary. The resultant poly(n-alkylacrylate) polymer product has an n-alkyl moiety distribution throughout the monomer reactant mix essentially the same as the n-alkyl distrlbution in the alcohol precursor utilized to manufac-ture the n-alkylacrylate reactant.
One suitable source of precursor alco~q~mixtures ~d~c ~glf~ls~
are the alcohols sold under the tradoname "AlfolE" by Continental Oil Company. "Alfols" are impure mixtures con-taining as the ma~or portion, greater than 50 wt. % n-alkanols of various chain lengths, the remainder consisting of hydrocarbons, ketones and hindered unreactive alcohols.
Typical analysis of two suitable examples of the "Alfol"
alcohols are as follows: ;

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-~ Typical Properties Alfol 20+R Alfol 22+R
Approx. homolog distribution 100% alcohol basis, wt. %
C18 2 1 .-C24 lo 21 Alcohol Content, wt. % approx. 70 60 - .
Hydroxyl No. 123 90 Hydroxyl No. 100% alcohol basis 176 Sap. No. 3 6 -I2 No. 12 13 : ~ `
Carbonyl, wt. % (as C = 0) 0.2 0.3 ,!,. , ':
- Melting range, C. 45-58 45-58 Color, Gardner 12 18 The amount of free radical catalyst employed may range between about 0.1 and 5 wt. %, preferably between about 0.5 and 2 wt. % basis the monomer reactant. Any of the free radical liberatlng type of polymerization initiator catalyst may be employed, but those that are especially suitable are the azo initiators taught in U. S. Patent No. 2,471,959 and perioxide and hydrolperoxide initiators.
Although all of the azo catalyst set forth in U. S.

2,471,959 are suitable in the polymerization procedure con-templated herein, those most particularly suitable are the -alpha-alpha-azobis(cyanoalkane) wherein the cyano alkyl ` 30 groups are of each from 4 to 11 carbons and particularly where each carbon attached to both azo and cyano groups is ,:; -. .' ~:: . ~ ' ,,, .: .. : :

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tertiary. Examples of such azo compounds are alpha-alpha' bisisobutyronitrile, alpha-alpha'-azobismethylbutyronitrile, alpha-alpha'-azobisethylbutryonitrile, alpha-alpha'-azobis-hexylpropionitrile.
Examples of the peroxide and hydroperoxide free radical catalysts are the dialkyl peroxides, diacyl per-oxides, benzoyl peroxides, such as diacetyl peroxides, dido-decyl peroxide, diethyl peroxide, di-t-butyl peroxide, caproperoxide, t-butyl perbenzoate, di-t-butyl diperphthal-ate, diacetyl peroxide and their hydroperoxide counterparts.
One embodiment of the invention are the pourdepressed waxy heavy fuel fractions containing a pour depressing amount of the novel poly(n-alkylacrylate) of products of the method of the invention. Utilizing the products of the invention, pour depressing effects in the heavy petroleum fractions are sometimes evidenced in amounts as small as about 0.01 wt. % and quantities up to 3 wt. %
are usually sufficient. Desirably, quantities ranging be-tween about 0.04 and 0.5 wt. % polyacrylates are employed.
To facilitate blending of the polyacrylate product to the petroleum fraction, the polyacrylate may be diluted with solvent such as a light gas oil of a kinematic viscosity (cs.) of between about 2 and 4 at 100F. to form between about a 10 and 50 wt. % polyacrylate lube oil concentrate.
In compounding the waxy heavy petroleum fraction compositions of the invention, it is essential that the polyacrylate pour depressor be introduced into the fractlon at a temperature above the solution point of the macro-crystalline paraffin wax component. Usually a temperature of about 200~F. or more is required. If the polyacrylate ,~ . :

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is contacted with the wax petroleum component at a tempera-ture substantially below the solution point oP a substantial portion of the wax, there is little or no pour depressing . effect by the polyacrylate.
The heavy petroleum base fractions contemplated herein are a macrocrystalline wax content of between about :-4 and 15 wt. ~, and a pour point of the order of 40-130F.
Examples of these fractions are residual fuel oils, vacuum - -gas oils and lubricating oils of a boiling point range of between 400-1100F. (vacuum or atmospheric) meeting the foregoing wax content and pour point and are more fully described in the aforementioned, coassigned related appli-; cations.
- The following examples further illustrate the method, product and composition of the invention but are not to be construed as limitations thereof.

- EXAMPLE I
This example illustrates the manufacture of the n-alkylacrylate monomer reaction mixture.

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Monomeric n-alkylacrylates of two alcohols were prepared. Composition of these alcohol precursors are as follows:

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10;~7~1 Typical Properties Alkanol A Alkanol B
Approx. homolog distribution 100% alcohol basis, wt. %
n-C18 5 0 n-C20 39 12 n-C 27 47 n-C 4 14 21 n-C 7 10 Alkanol Content, wt. % 70 60 Hydroxyl No. 123 90 Hydroxyl No., 100% alcohol basis 176 90 Sap. No. 3 6 Carbonyl, wt. % (as C=0) 0.2 0.3 Melting Range, C. 45-55 45-55 -Color, Gardner 12 18 The charge materials in the monomer process are 20 as follows: ~

Material Wt. (g) Moles ~ -Hydroqulnone 2 0.02 j`
p-Toluenesulfonic acid 5.6 0.036 Alcohol A (Run 1) 952 2 Alcohol B (Run 2) 1245 2 j-- , Acrylic acid, glacial 144 2 Benzene 536 - ~ ;
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All the above charge except the acrylic acid was melted under nitrogen at about 60C. (140F.). The acrylic 30 acid was then added with stirring and the mixture brought ~ ~
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to reflux with a pot temperature of about 90C. (194F.).
- Air was introduced below the surface of the liquid reaction mixture at a rate of between about 40 and 45 mls./minute as -the water of the reaction was azeotroped off at a reflux rate of 4 mls./minute. About 96 wt. % of the theoretical amount of water was removed in 12 hours and all the water was removed in 21 hours. Benzene was removed by stripping the product to 15 mm Hg. pressure at a pot temperature of about 160C. (320F.).
The product was a monomer mixture of n-alkyl acrylate wherein the n-alkyl distribution therein was essen-tially the same as the alkyl distribution in the alkanol reactive portion of the alcohol precursor.
Physical data for the monomer mixture products were as follows:

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Physical Data Mono- Mono-For Monomer Acrylate A Acrylate B

Sap. No. 115 95 Neut. No. 1.3 1.1 20 Hydroxyl No. 8 14 Sp. Grav., 150F./60F. 0.8316 0.8310 Refractive Index 1.4450 1.4465 Kin. Visc., cs. 150F. 7.39 8.84 210F. 3.90 4.50 Dialysis Residue, wt. % 3 3 Melting Point, C. (approx.) 36 49 .. . .
~ EXAMPLE II

,~ This example illustrates the method of the invention, the products resulting therefrom and pour de-30 pressed compositions containing the poly(n-alkylacrylate) _g_ 1C);~7~

pour depressors manufactured by the method of the inventlon.
In three separate runs 200 grams of Monoacrylate A prepared in Example I were heated to 85C. (185F.) under prepurified nitrogen introduced into the reaction system at a rate of30 mls./minute. The further procedure in each of the three runs was as follows, Run 1 and 2 representative of the method of the invention and Run 3 being comparative method. The runs are as follows:
1. Run 1 - The reaction period was for 7 hours and a total of 3 additions of azobisisobutyronitrile i~ a total amount of 1 wt. % was added during this 7 hour period.
There was initially added 0.5 wt. % catalyst. At the third hour of reaction the refractive index became constant and there was added an additional 0.25 wt. % of catalyst. At the 4.5 hour of reaction the refractive index again became constant and an additional 0.25 wt. % of catalyst was added. ~' The polymer product was designated as Polyacrylate 1. ~ - -2. Run 2 - Four additions of azobisisobutyroni- ;~
trlle were made in this run over a 6 hour 45 minute period.
Initially there was added 0.25 wt. % catalyst. At the end ~, of two hours an additional 0.25 wt. % was added. At the end of 4 hours and 40 minutes an additional 0.25 wt. % was added and at the end of 6 hours and 45 minutes an additional 0.25 wt. % was added. The reaction was conducted for a total period of ~0 hours. The polymer product was designated as Polyacrylate 2. ,

3. Run 3 - In this comparative run there was only one addition of the azoisobutyronitrile catalyst and thls was introduced at zero hours of reaction. The reactlon period was for 3 hours. The polymer product was designated as Polyacrylate 3. -~ 7b~
In all the foregoing three procedures the reac-tion mixture was continuously stirred and periodic refrac-tive index measurements of the mixture were taken. The reaction was continued until the refractive index remained constant after the final catalyst addition, the refractive index being deemed constant when the variation is less than + 1.5 units in the fourth decimal place.
The products prepared were cooled and analyzed and the resultant (poly(n-alkylacrylate) gave the following ~-analysis:

Physical Data Poly- Poly- Poly-(Av. Value) Acrylate 1 Acrylate 2 Acrylate 3 , RI at 54C . 1.4545 1.4545 1.4545 Sp. Grav., 150F./60F. 0.8580 0.8573 0.8580 Melting Point, C. (approx.) 43-44 43-45 39 Kin. Visc., cs 150F . 222.5 206.1 196 210F. 91.9 85.6 81 Dialysis, wt. % Residue 58 55.3 42 Melting Point of 47-51 47-51 20 Dialysis Res., C (approx.) Mol wt. of Dialysis 24,200 28,000 29,000 Residue*
*Membrane Osmometry The distribution of the alkyl groups in the polymer was essentlally that found in the reactive n-alkanol of the alcohol precursor reactant.
The re~ultant polyacrylate products were diluted with a light hydrocarbon oil having a pour point of about 0F. and a kinematic viscosity at 100F. of about 3 to form 30 a 25 wt. % oil concentrate solution of the polyacrylate.
The compositions were then prepared by incorporating the formed polyacrylate concentrates in a heavy waxy residual - ~

7t~1 fuel oil fractlon comprising 50 volume % macrocrystalline wax containing vacuum petroleum residuum and 50 volume %
non waxy hydrotreated gas oil having a boiling point of between about 400 and 652F., an API gravity of 35.3 and a pour point of about -5F. The waxy base fuel fraction (F-30) had the following propertles:

Physical Tests Results Pour Point, F. 85 Wax Content, wt. % 12.7 10 SUS Visc. at 150F. 70.2 ~
API, Gravity 24.1 ~ -Wt. Sulfur 0.18 `

In the preparation of the polyacrylate contain-ing residual fuel compositions, the following procedure -~
was employed.
The petroleum vacuum residuum component of the fuel fraction was heated to 200F. with stirring for ~ ;~
1/2 hour during which time the polyacrylates prepared above were added. Subsequently, the hydrotreated gas oil was blended into the mixture at 150F. followed by stirring at 155F. for an additional 0.5 hour.
The effectiveness of the three polyacrylates (PAA), that is, representative Polyacrylates 1 (PAA-l) and 2 (PAA-2) and comp~rative Polyacrylate 3 (PAA-3) in depress-ing the pour point of the waxy fuel is set forth below in the following table and demonstrates the superiority of the polyacrylates formed from the method of the invention utilizing multiple free radical catalyst addition as opposed to the polyacrylate prepared by the single catalyst 30 addition prior method. The pour points in the following !~

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table were measured in accordance with ASTM Tests D-97.
Further, the pour points were measured after 5 days, 7 days, 12 days and 44 days. The test results are as follows:
-----Pour Point, F., after--------Polymer Conc. wt.% Avg. 5 Days 7 Days 12 Days 44 Days Sample PAA-l 0.07 50 45 55 5 5 0.06 45 50 55 45 35 0.05 60 55 70 70 55 ~ -0.04 65 65 70 75 55 0.02 70 65 75 75 65 -0.01 74 65 85 75 80 PAA-2 0.07 4 35 5 45 35 o.o6 50 55 70 40 35 -0.05 50 55 55 50 35 0.04 60 50 70 65 55 0.03 60 50 70 65 55 ;
0.02 65 65 70 60 65 0.01 80 75 85 85 85 0.03 80 80 80 80 75 .., . `' .
I EXAMPLE III
This example further illustrates the method, product and composition of the invention.
The procedures, materials out llned ln Example II were essentially employed with the followlng modifica-tions.

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1~7~1 Two polyacrylates were prepared representative Polyacrylate 4 (PAA-4) prepared by the multiple catalyst addition method of the invention and comparative Polyacrylate 5 (PAA-5) prepared by the single catalyst addition method: -1. Run 4 - The total reaction period was 10 hours and a total amount of 0.92 wt. % azobisisobutyronitrile was added to the polymerization mixture. There was added to 0.62 wt. % catalyst initially followed by 0.1 wt. % additions after 3.5 hours, 5 hours and 7 hours. ~ ~
2. Run 5 - In the comparative run all the cata- ~ -lysts, namely, 0.92 wt. % was added initially and the reac-tion period was for 3 hours.
The prepared Polyacrylate 4 (PAA-4) and 5 (PAA-5) respectively from Runs 4 and 5 gave the following analysis: :

Physical Data .
(Av. Value) PAA-4 PAA-5 -RI at 54C. 1.4545 1.4545 -~
Sp. Grav., 150F./60F. 0.8642 0.85Bo Melting Point, C. (approx.) 42-43 39 20 Kin. Visc., cs 150F. 430.9 196 210F. 168.5 81 Dialysis, wt. % Residue 60.9 42 Mol. wt. % of Dialysis Residue 29,000 29,000 ~-Melting Point Dialysis 43-46 Residue, C. (approx) The n-a~kyl distribution in the respective Poly-acrylates 4 and 5 was of Alcohol A described in Example I.
Representative PAA-4 and comparative PAA-5 were -incorporated in the residual fuel oil base fraction descrlbed ~ . . . .
in Example II in the manner described therein and the pour points of the resultant compositions were measured over a : - ..., : .,,- .. .
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1037~1 period of 5 to 12 days. The following data illustrates the superior properties re pour depressing of the product result-ing from a multiple catalytic addition as opposed to one pre-pared from a single dose. The results are as follows:
-----Pour Point, F. after------- . - .

Polymer Conc. wt.% Avg. 5 Days 7 Days 12 Days Sample PAA-4 0.07 30 35 3 25 0.06 35 35 45 30 ~ :

0.05 45 45 45 45 0.04 35 40 35 25 0.03 40 35 4 5 :~
0.02 65 70 55 ~0 0.01 80 80 80 85 PAA-5 0.05 50 40 55 50 0.03 55 45 60 55 ', ' .

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Claims (5)

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

1. A waxy heavy petroleum fraction having a microcrystalline wax content between about 4 and 15 wt. %
and a pour point between about 40 and 130°F. containing between about 0.01 and 3 wt. % of an interpolymeric poly(n-alkylacrylate) of a molecular weight between about 3000 and 100,000 wherein said n-alkyl is of at least 18 carbons and at least 70 wt. % of said n-alkyl is of between 20 and 24 carbons inclusively, the C20 to C24 alkyl group consisting of between about 2 and 65 wt. % C20 alkyl, between about 18 and 65 wt. % C22 alkyl and between about 8 and 35 wt. %
C24 alkyl, said interpolymeric poly(n-alkylacrylate) prepared by the method comprising heating a mixture of n-alkylacrylate wherein the n-alkyl distribution in said mixture is as in said interpolymeric poly(n-alkylacrylate) to a temperature between 60 and 120°C. and periodically introducing into said heated mixture in spaced additions of from 2 to 10 in number, a free radical polymerization catalyst in a total amount of between about 0.1 and 5 wt.
%, each addition of said catalyst being about equal weight to or greater than each following addition, said inter-polymeric poly(n-alkylacrylate) being introduced into said fraction at a temperature above the solution point of said wax.

2. A heavy petroleum fraction in accordance with Claim 1 wherein the catalyst additions subsequent to the first addition are made upon cessation of polymerization.

16 9. A waxy heavy petroleum fraction in accordance with Claim 1 wherein said catalyst additions are from 3 to 5 in number and said total amount of said catalyst added is between about 0.5 and 2 wt. %.

4. A waxy heavy petroleum fraction in accordance with Claim 1 wherein said free radical polymerization cata-lyst is a alpha-alpha'-azobis(cyanoalkane) wherein the cyanoalkane groups are each of 4 to 11 carbons.

5. A waxy heavy petroleum fraction in accordance with Claim 1 wherein said catalyst is alpha-alpha'-azobis-isobutronitrile.