US 3642459 A
Copolymers comprising within the range of 40 to 89 wt. percent ethylene, 10 to 40 wt. percent of vinyl ester of C2 to C4 monocarboxylic acid, and 1 to 30 wt. percent of unsaturated ester having a C10 to C22 alkyl group and having number average molecular weights within the range of 1,000 to 50,000, are useful in oil, e.g., as pour point depressants in distillate petroleum fuels and as dewaxing aids.
Description (OCR text may contain errors)
United States Patent Ilnyckyj [4 1 Feb. 15, 1972  COPOLYMERS OF ETI-IYLENE WITH UNSATURATED ESTERS AND OIL COMPOSITIONS CONTAINING SAID COPOLYMERS  Inventor: Stephan Ilnyckyj, Islington, Ontario, Canada I  Assignee: Esso Research and Engineering Company  Filed: Apr. 1, 1968 211 App]. No.2 717,915
 US. Cl ..44/62, 44/70  Int. Cl. ..Cl0l1/18  Field of Search ..44/62, 70; 260/8081  References Cited UNITED STATES PATENTS 3,467,597 9/1969 Tunkel ct a1 ..44/70 Primary Examiner-Daniel E. Wyman Assistant ExaminerY. H. Smith Attorney-Pearlman and Schlager and Frank T. Johmann [5 7] ABSTRACT 3 Claims, No Drawings BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to copolymers of ethylene with vinyl ester of C to C,, monocarboxylic acid and copolymerizable unsaturated esters having C to C alkyl groups, which copolymers are useful as pour point depressants in distillate petroleum fuels and as dewaxing aids.
2. Description of the Prior Art Copolymers of ethylene and vinyl esters of lower fatty acids, particularly vinyl acetate, are described in US. Pat. No. 3,048,479 as effective pour point depressants for middle distillate fuels. These prior pour point depressants, while very effective in treating the distillate oil to lower the pour point, frequently result in wax crystals having large particle sizes ranging from 1 millimeter up to an inch in their largest dimension. While the treated distillate oil containing these large wax crystals exhibits a pour point significantly under the original pour point of the untreated oil, in many cases the large wax crystals will tend to plug filter equipment normally used on delivery trucks and fuel oil storage systems, when the oil is cooled below its cloud point, even though above its pour point. Thus, as the oil containing the pour point depressant is cooled, the cloud point (the point at which the oil becomes cloudy due to crystallization of wax) will be reached at a temperature significantly above the pour point (the point at which the oil can no longer conveniently be poured). As a result, oils below their cloud point and above their pour point will be pourable, but at the same time the wax crystals that have formed, if too large, can result in plugging the filters, that are used as protection against foreign matter, in the dispensing system.
SUMMARY OF THE INVENTION It has now been found that by copolymerizing a small amount of copolymerizable unsaturated ester, having C to C alkyl groups, with ethylene and the lower vinyl esters, e.g., vinyl acetate, that the good pour point reduction of the ethylene-vinyl acetate copolymer is still retained and smaller wax crystals are formed during cooling of the treated oil. Specifically, the maximum size of the wax crystals that are formed on cooling at rates encountered during cold weather are generally significantly reduced to a particle size in the order of about 0.1 millimeter or less. As a result, even though the cloud point of the oil treated with this new polymer is substantially the same as the cloud point when the oil is treated with the old copolymer of ethylene and vinyl acetate, an important improvement in filterability is obtained in actual operating use. Thus, the new polymer eliminates a problem of clogged filters associated with the conventional pumps employed on oil delivery trucks, and also with the usual screens used in conjunction with the oil storage tanks to prevent the accidental inclusion of foreign matter in the oil system. These screens traditionally are in the order of 60 mesh or coarser and have a tendency to clog if the wax crystal size is too large. Also, in many cases, the new polymer is also found more effective in lowering the pour point of the oil than the old copolymers ofethylene and vinyl acetate.
These new polymers of the invention will comprise in the range of about 40 to 89 wt. percent, preferably 50 to 80 wt. percent, of ethylene; to 40 wt. percent, preferably to 35 wt. percent, of vinyl ester of a C to C fatty acid; 1 to 30 wt. percent, preferably 3 to 25 wt. percent, of unsaturated ester having C to C alkyl groups, the resulting polymer being mineral oil soluble and having a number average molecular weight in the range of about 1,000 to 50,000, preferably, about 1,500 to about 5,000.
Examples of the vinyl ester of C to C fatty acids include vinyl acetate, vinyl n-propionate, vinyl n-butyrate, vinyl isopropionate, etc., and any mixtures thereof.
The unsaturated esters with the C to C alkyl groups include those copolymerizable mono-ethylenically unsaturated, monoesters of the general formula:
wherein X is a hydrogen or a methyl group, and Y is a OOCR or COOR wherein R is a C to C preferably a C to C straight chain or branched chain, alkyl group.
Examples of the long chain unsaturated monoesters include the vinyl esters of C to C monocarboxylic acid (i.e., where Y is OOCR) such as vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl arachidate, etc. Other examples of said monoesters are acrylic or methyl acrylic acid esters (i.e., where X is COOR) such as lauryl acrylate, stearyl acrylate, palmityl alcohol ester of alpha-methyl-acrylic acid, C Oxo alcohol ester of methacrylic acid, etc.
A number of ways of carrying out the polymerization is possible to form the polymers of the invention. In general, the techniques taught for ethylene-vinyl ester polymerizations in US. Pat. Nos. 3,048,479, 3,131,168, 3,093,623 'and 3,254,063 can be used. However, a particularly useful technique is as follows: Solvent and a portion of each of the unsaturated esters, e.g., 5 to 30 percent, preferably 10 to 20 percent, of the total amount of each unsaturated ester used in the batch, are charged to a stainless steel pressure vessel which is equipped with a stirrer. The temperature of the pressure vessel is then brought to reaction temperature and pressured to the desired pressure with ethylene. Then a catalyst and additional amounts of each vinyl ester are added to the vessel periodically or continuously during the reaction time. Also during this reaction time, as ethylene is consumed in the polymerization, additional ethylene is supplied through a pressure-controlling regulator so as to maintain the desired reaction pressure fairly constant at all times. Following the completion of the reaction, the liquid phase of the pressure vessel is distilled to remove the solvent and other volatile constituents of the reacted mixture, leaving the polymer as residue. In general, based upon parts by weight of polymer to be produced, then about 100 to 600 parts by weight of solvent, and about one to 10 parts by weight of catalyst, will be used.
The catalyst, or promoter, will generally be of the free radical type, including organic peroxide types such as benzoyl peroxide, ditertiary butyl peroxide, dicumyl peroxide, tertiary butyl perbenzoate, lauroyl peroxide, t-butyl hydroperoxide, and also such nonperoxy compounds as azo-bis-isobutyronitrile, and the like.
The solvent can be any nonreactive organic solvent for furnishing a liquid phase reaction, preferably hydrocarbon solvent such as benzene, or hexane, etc.
Temperatures and pressures employed may vary widely. For example, depending partly on the decomposition temperature of the catalyst, the temperature may range from 100 F. to 450 F. with pressures of 500 to 30,000 p.s.i.g. However, usually the temperature will range between about F. and about 350 F., and relatively moderate pressures of 700 to about 3,000 p.s.i.g. will be used. It is only important that a superatmospheric pressure be employed, which is at least sufficient to maintain a liquid phase medium under the reaction conditions, and is sufficient to maintain the desired concentration of ethylene in solution in the solvent. In general, this pressure is attained by maintaining a continuous pressure on the reaction chamber through controlling the inlet feed of ethylene.
The time of reaction will depend upon, and is interrelated to, the temperature of the reaction, the choice of catalyst, and the pressure employed. In general, however, 1 to 10 hours will complete the reaction.
The polymers of the invention will generally be added to hydrocarbon oils in amounts of 0.001 to 2 wt. percent, generally 0.005 to about 0.5 wt. percent, said wt. percent being based upon the weight of the oil to be treated.
The hydrocarbon oils, which are treated for pour depression with the polymers of this invention, include cracked and virgin distillate oils boiling in the range of 250 to 750 F., such as kerosene, heating oil, diesel fuel oil, etc. Also, fuel oil blends comprising a major amount of distillate oil boiling in the aforesaid 250 to 750 F. range and a minor amount of higher boiling residual oil can also be treated for pour depression. In addition, the polymers of the invention can be used as a dewaxing aid during dewaxing of light distillate lube oil stocks boiling in the 600-1,000 F. range in the manner similar to that taught in U.S. Pat. No. 3,262,873.
The polymers of the invention may be used alone as the sole oil additive, or in combination with other oil additives such as other pour depressants or dewaxing aids; corrosion inhibitors, such as sodium nitrite and dicyclohexyl ammonium nitrite; antioxidants such as octadecylamine; sludge inhibitors; etc.
The invention will be further understood by reference to the following examples which include a preferred embodiment of the invention.
EXAMPLE I A l-gallon stirred autoclave was first flushed with nitrogen and then ethylene. The autoclave charged with 1,145 ml. of benzene as solvent, 50 ml. of vinyl acetate, and ml. of vinyl laurate was then heated to 335 F. and ethylene pressured into the autoclave until the pressure was raised to 1,250 p.s.i.g. Then ditertiary butyl peroxide as catalyst and additional vinyl acetate and vinyl laurate were continuously injected into the autoclave at an even rate. A total of 9 ml. of the peroxide was injected over 1% hours, while 300 ml. of vinyl acetate and 80 ml. of vinyl laurate were injected into the reactor over a period of 1% hours from the start of the injection. At the end of 1% hours, the temperature of the reactor contents was lowered to 200 F. and the product was discharged from the autoclave. The product was then stripped of the solvent and unreacted monomers by distillation under slightly reduced pressure. Next, excess vinyl laurate was removed overhead by high vacuum distillation, that is, under a pressure of about 2 mm. Hg. The final product consisted of 441 grams of terpolymer.
EXAMPLE II A polymer was prepared under the identical conditions of Example 1, except the quantities of vinyl esters had been changed as follows: The initial charges of vinyl acetate and vinyl laurate amounted to 40 ml. and 35 ml., respectively, and 250 ml. of vinyl acetate and 230 ml. of vinyl laurate were each injected over a 1% hour period. 727 grams of the terpolymer were obtained.
COMPARISON A To show the effect of excluding the higher vinyl ester, a copolymerization was carried out under conditions similar to those of Example 1, except vinyl laurate was excluded, the initial charge of vinyl acetate amounted to 55 ml., and 300 ml. of additional vinyl acetate was injected over 1% hours. The copolymer yield amounted to 550 grams.
The above polymers of Examples 1, II and Comparison A, since they were prepared under similar conditions, would have comparable molecular weights, which prior experience indicates would be about 2,000 number average molecular weight.
The polymers prepared above were tested for pour depression in a test fuel oil which was a gas oil distillate fuel oil (50 percent virgin 50 percent cracked) having a pour point of +25 F. and an ASTM final boiling point of 660 F. The compositions of the polymers, the concentrations used in the test fuel oil, and the pour points (ASTM D97) obtained, are summarized in the following table:
TABLE Composition of Polymer, wl. Example Example Comparison I II A Ethylene 65 60 70 Vinyl acetate 28 20 30 Vinyl laurate 7 20 0 Pour Point at 0.0l0 wt. polymer 0 F 5 F. 5 F. Pour Point at 0.015 wt. k polymer 25 F. 20 F. 15 F. Pour Point at v 0.018 wt. polymer 60 F. -35 F. 25 F.
As seen by the above table, the copolymers of Examples l and II at concentrations of 0.015 wt. percent (based on the weight of the test oil) and above, were more effective in reducing the pour point of the oil than the Comparison A polymer which did not contain the higher vinyl ester.
The superiority of the polymers of the invention are further demonstrated by a filterability test. This test was carried out using a straight run distillate paraffin base fuel oil having a boiling range of 336 to 646 F. according to ASTM D-86; an ASTM cloud point of 14 F. and an ASTM pour point of 5 F. The Filterability Test measures the ability of an oil, when cloudy, to pass through filters encountered in oil distribution systems. This test is carried out in a cylindrical jar consisting of two chambers separated by a partition. Each chamber has a capacity of 200 ml. The partition is provided with an opening having an area of 0.2 square inches. A U.S. 40-mesh screen is inserted into the opening which is then plugged with a stopper. 200 ml. of oil are poured into the upper chamber and the tester containing the oil is then chilled at a rate of 1 F. per hour to a temperature 5 F. below the ASTM cloud point of the oil. At this point, the stopper is pulled out from the opening allowing the cloudy oil to flow into the lower chamber. In order to be considered of satisfactory quality, at least 90 percent of the sample has to pass into the lower chamber in no more than 25 seconds. 0.05 wt. percent of the polymer product of Example I in the test oil reduced the pour point a total of 55 F. and gave a percent pass in the filterability test at 7 F. In comparison, 0.05 wt. percent ofa commercial ethylene vinyl acetate pour point depressant consisting of about 70 wt. percent ethylene and 30 wt. percent vinyl acetate and having a number average molecular weight of about 2,000, gave a pour depression of 45 F. but only a 25 percent passage in the filterability test. In addition, examination of the wax crystals formed when the oil containing the 0.05 wt. percent of the polymer of Example I was cooled at the rate of 1 F. down to the pour point, showed that the wax crystals mea sured approximately 0.1 mm. in their longest dimension, while the wax crystals formed using an equal amount of the aforesaid commercial pour depressant measured approximately about 1 mm. across their longest dimension.
As a further illustration of the invention a polymer is prepared in the general manner of Example I, but using stearyl acrylate in place of the vinyl laurate, and 0.1 wt. percent of the resulting terpolymer can be added to the oil used in the aforementioned table.
What is claimed is:
l. A petroleum distillate oil boiling in the range of about 250-1,000 F., containing about 0.001 to about 2 wt. percent of a polymer comprising about 40 to 89 wt. percent ethylene, about 10 to 40 wt. percent vinyl ester ofC to C monocarboxylic acid, about 1 to 30 wt. percent of unsaturated ester represented by the formula:
wherein X is selected from the group consisting of hydrogen and methyl groups, and Y is the OOCR radical in which R is a C to C alkyl group, said polymer having a number average molecular weight of about 1,000 to 50,000.
2. A petroleum distillate oil boiling in the range of about 250-750 F., containing about 0.005 to 0.5 wt. percent of a polymer comprising about 40-89 wt. percent ethylene, about -40 wt. percent vinyl acetate and about 1-30 wt. percent of unsaturated ester represented by the formula: