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| United States Patent |
5,772,706
|
|
Schield
, et al.
|
June 30, 1998
|
Methods and compositions for improvement of low temperature fluidity of
fuel oils
Abstract
Adding to a fuel oil a composition of from about 1 to about 40 parts by
weight ethylene/vinyl acetate copolymer having a vinyl acetate content of
from about 10% by weight to about 50% by weight and a weight average
molecular weight of from about 2,000 to about 10,000, and 1 part by weight
esterified copolymer of at least one generally linear .alpha.-olefin of
from about 18 to about 50 carbon atoms and maleic anhydride in an
.alpha.-olefin to maleic anhydride molar ratio of from about 4:1 to about
1:2, the copolymer having a weight average molecular weight of from about
2,000 to about 20,000, the esterified copolymer having been esterified
with a plurality of aliphatic alcohols having from about four to about
forty carbon atoms, imparts to the fuel oil surprisingly improved low
temperature fluidity, provided that the alcohols include an eight carbon
alcohol making up from about 50 to about 85 molar percent of the alcohols.
| Inventors:
|
Schield; John A. (Chesterfield, MO);
Weers; Jerry J. (Richmond, TX)
|
| Assignee:
|
Baker Hughes Incorporated (Houston, TX)
|
| Appl. No.:
|
928289 |
| Filed:
|
September 12, 1997 |
| Intern'l Class: |
C10L 001/18 |
| Field of Search: |
44/395,393,403
|
References Cited
U.S. Patent Documents
| 4153422 | May., 1979 | Wisotsky | 44/395.
|
| 4240916 | Dec., 1980 | Rossi | 508/306.
|
| 4481013 | Nov., 1984 | Tack et al. | 44/394.
|
| 4652611 | Mar., 1987 | Karoda et al. | 44/393.
|
| 5441545 | Aug., 1995 | Lewtas et al. | 44/395.
|
| 5478368 | Dec., 1995 | Lewtas et al. | 44/395.
|
| 5503645 | Apr., 1996 | Jung et al. | 44/395.
|
Primary Examiner: Howard; Jacqueline V.
Attorney, Agent or Firm: Howell & Haferkamp, LC
Claims
What is claimed is:
1. A composition useful for improvement of low temperature fluidity of fuel
oils, comprising from about 1 to about 40 parts by weight ethylene/vinyl
acetate copolymer having a vinyl acetate content of from about 10% by
weight to about 50% by weight and a weight average molecular weight of
from about 2,000 to about 10,000, per 1 part by weight esterified
copolymer of at least one generally linear .alpha.-olefin of from about 18
to about 50 carbon atoms and maleic anhydride in an .alpha.-olefin to
maleic anhydride molar ratio of from about 4:1 to about 1:2, the copolymer
having a weight average molecular weight of from about 2,000 to about
20,000, the esterified copolymer having been esterified with a plurality
of aliphatic alcohols having from about four to about forty carbon atoms,
including at least one eight carbon alcohol, the at least one eight carbon
alcohol making up from about 50 to about 85 molar percent of the alcohols.
2. A composition as set forth in claim 1 wherein the .alpha.-olefin
contains from about eighteen to about thirty carbon atoms.
3. A composition as set forth in claim 2 wherein the .alpha.-olefin
contains about thirty carbon atoms.
4. A composition as set forth in claim 1 wherein the .alpha.-olefin to
maleic anhydride molar ratio is about 1:1.
5. A composition as set forth in claim 1 wherein the copolymer of the
.alpha.-olefin and the maleic anhydride has a weight average molecular
weight of from about 5,000 to about 8,000.
6. A composition as set forth in claim 1 wherein each of the at least one
eight carbon alcohol is a branched aliphatic alcohol.
7. A composition as set forth in claim 6 wherein each of the at least one
eight carbon alcohol is an ethylhexyl alcohol.
8. A composition as set forth in claim 7 wherein the at least one eight
carbon alcohol is one eight carbon alcohol, namely 2-ethylhexyl alcohol.
9. A composition as set forth in claim 1 wherein the composition comprises
from about 1 to about 20 parts by weight of the ethylene/vinyl acetate
copolymer per 1 part by weight of the esterified copolymer.
10. A composition as set forth in claim 1 wherein the composition comprises
from about 3 to about 10 parts by weight of the ethylene/vinyl acetate
copolymer per 1 part by weight of the esterified copolymer.
11. A method for improving low temperature fluidity of fuel oils,
comprising adding to the fuel oil an effective amount of a composition
useful for improvement of low temperature fluidity of fuel oils,
comprising from about 1 to about 40 parts by weight ethylene/vinyl acetate
copolymer having a vinyl acetate content of from about 10% by weight to
about 50% by weight and a weight average molecular weight of from about
2,000 to about 10,000, and about 1 part by weight esterified copolymer of
at least one generally linear .alpha.-olefin of from about 18 to about 50
carbon atoms and maleic anhydride in an .alpha.-olefin to maleic anhydride
molar ratio of from about 4:1 to about 1:2, the copolymer having a weight
average molecular weight of from about 2,000 to about 20,000, the
esterified copolymer having been esterified with a plurality of aliphatic
alcohols having from about four to about forty carbon atoms, including at
least one eight carbon alcohol, the at least one eight carbon alcohol
making up from about 50 to about 85 molar percent of the alcohols.
12. A method as set forth in claim 11 wherein the .alpha.-olefin contains
from about eighteen to about thirty carbon atoms.
13. A method as set forth in claim 12 wherein the .alpha.-olefin contains
about thirty carbon atoms.
14. A method as set forth in claim 11 wherein the .alpha.-olefin to maleic
anhydride molar ratio is about 1:1.
15. A method as set forth in claim 11 wherein the copolymer of the
.alpha.-olefin and the maleic anhydride has a weight average molecular
weight of from about 5,000 to about 8,000.
16. A method as set forth in claim 11 wherein each of the at least one
eight carbon alcohol is a branched aliphatic alcohol.
17. A method as set forth in claim 16 wherein each of the at least one
eight carbon alcohol is an ethylhexyl alcohol.
18. A method as set forth in claim 17 wherein the at least one eight carbon
alcohol is one eight carbon alcohol, namely 2-ethylhexyl alcohol.
19. A method as set forth in claim 11 wherein the composition comprises
from about 1 to about 20 parts by weight of the ethylene/vinyl acetate
copolymer per 1 part by weight of the esterified copolymer.
20. A method as set forth in claim 11 wherein the composition comprises
from about 3 to about 10 parts by weight of the ethylene/vinyl acetate
copolymer per 1 part by weight of the esterified copolymer.
21. A fuel oil composition of improved low temperature fluidity comprising
fuel oil and a sufficient amount of a combination of an ethylene/vinyl
acetate copolymer and at least one esterified .alpha.-olefin/maleic
anhydride copolymer to impart to the fuel oil improved temperature
fluidity, the ethylene/vinyl acetate copolymer having a vinyl acetate
content of from about 10% by weight to about 50% by weight and a weight
average molecular weight of from about 2,000 to about 10,000, the at least
one esterified copolymer being selected from the group consisting of
esters of copolymers of generally linear .alpha.-olefins of from about 18
to about 50 carbon atoms and maleic anhydride in an .alpha.-olefin to
maleic anhydride molar ratio of from about 4:1 to about 1:2, the copolymer
having a weight average molecular weight of from about 2,000 to about
20,000, the esterified copolymer having been esterified with a plurality
of aliphatic alcohols having from about four to about forty carbon atoms,
including at least one eight carbon alcohol, the at least one eight carbon
alcohol making up from about 50 to about 85 molar percent of the alcohols.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvement of low temperature fluidity of
fuel oils, and more particularly to chemical treatment of fuel oils to
improve their low temperature fluidity.
2. Description of the Prior Art
Upon encountering low temperatures, fuel oils tend to develop fluidity
problems. In particular, paraffins in the fuel agglomerate at low
temperatures to form a waxy semi-solid or gel-like material that plugs
pipes and filters, inhibiting transmission of the fuel to, for example, an
engine.
Conventionally, this problem is treated by adding to the fuel a chemical
composition called a low temperature fluidity modifier. The low
temperature fluidity modifier can co-crystalize with or adsorb the
paraffins in the fuel oil to precipitate the paraffin before agglomeration
or to modify paraffin crystal growth so that the resulting irregularity in
size and shape of the crystals inhibits agglomeration or efficient packing
of the crystals, thereby reducing the tendency toward plug formation. By
contrast, pour point depressants are directed simply to viscosity
reduction of fluids. Thus, while studies have shown a relation between low
temperature fluidity of a fuel and the pour point or cloud point of the
fuel, the mechanism of low temperature fluidity modifier operation and the
problem to which low temperature fluidity modifiers are directed differ
significantly from those of pour point depressants. Therefore, despite the
apparent relationship between low temperature fluidity and pour point,
they typically require different treatments.
Because low temperature modifiers operate by affecting the crystal growth
of the paraffins in the fuel being treated, the selection and composition
of a low temperature fluidity modifier for a particular fuel is based on
the nature of the paraffins in that fuel. For example, low temperature
modifiers typically are coordinated with the paraffins in the fuel so that
the solubility characteristics of the modifier added to the fuel match the
solubility characteristics of the paraffins in the fuel. Thus, if a fuel
contains C.sub.20-24 paraffins that crystallize at 10.degree. F., the
modifier is typically designed to crystallize at about 10.degree. F. as
well, thereby to interfere with the crystallization of the paraffins.
Accordingly, it is well known to those of ordinary skill in the art of low
temperature fluidity modification to select and to adjust the array of
aliphatic chain lengths to balance overall solubility based on the
paraffin content of the fuel to cause the additive to precipitate out of
the fuel at the desired temperature. In fact, it is common to produce
esterified olefin/maleic anhydride copolymers for use in low temperature
fluidity modifier additive compositions by esterifying certain
olefin/maleic anhydride copolymers with an array of aliphatic alcohols
having chain lengths in the range of from about four to about forty carbon
atoms, and to select the distribution of aliphatic chain lengths in that
range in coordination with the paraffins in the fuel as discussed above.
Despite the existence of a variety of low temperature fluidity modifiers,
none provides completely satisfactory performance in all fuels. In fact,
because of the disparities in the characteristics of fuel oils, particular
low temperature fluidity modifiers meet with varying success from fuel to
fuel. Thus, there is a continual search for ever more effective low
temperature fluidity modifiers, particularly for use in various fuels.
SUMMARY OF THE INVENTION
The present invention, therefore, is directed to a novel composition useful
for improvement of low temperature fluidity of fuel oils. The composition
comprises from about 1 to about 40 parts by weight ethylene/vinyl acetate
copolymer having a vinyl acetate content of from about 10% by weight to
about 50% by weight and a weight average molecular weight of from about
2,000 to about 10,000, per 1 part by weight esterified copolymer of at
least one generally linear .alpha.-olefin of from about 18 to about 50
carbon atoms and maleic anhydride in an .alpha.-olefin to maleic anhydride
molar ratio of from about 4:1 to about 1:2, the copolymer having a weight
average molecular weight of from about 2,000 to about 20,000. The
esterified copolymer has been esterified with a plurality of aliphatic
alcohols having from about four to about forty carbon atoms, including at
least one eight carbon alcohol, the at least one eight carbon alcohol
making up from about 50 to about 85 molar percent of the alcohols.
The present invention is also directed to a novel method for improving low
temperature fluidity of fuel oils. The method comprises adding to the fuel
oil an effective amount of a composition as described in the preceding
paragraph.
The present invention is further directed to a novel fuel oil composition
of improved low temperature fluidity comprising fuel oil and a sufficient
amount of a combination of an ethylene/vinyl acetate copolymer and at
least one esterified .alpha.-olefin/maleic anhydride copolymer to impart
to the fuel oil improved temperature fluidity. The ethylene/vinyl acetate
copolymer has a vinyl acetate content of from about 30% by weight to about
50% by weight and a weight average molecular weight of from about 2,000 to
about 10,000. The esterified copolymers are selected from among esters of
copolymers of generally linear .alpha.-olefins of from about 18 to about
50 carbon atoms and maleic anhydride in an .alpha.-olefin to maleic
anhydride molar ratio of from about 4:1 to about 1:2, the copolymer having
a weight average molecular weight of from about 2,000 to about 20,000. The
esterified copolymer has been esterified with a plurality of aliphatic
alcohols having from about four to about forty carbon atoms, provided that
one of the alcohols is an eight carbon alcohol that is present in a
concentration of from about 10% by weight to about 25% by weight based on
the total composition, including at least one eight carbon alcohol, the at
least one eight carbon alcohol making up from about 50 to about 85 molar
percent of the alcohols.
Among the several advantages of this invention, may be noted the provision
of a low temperature fluidity modifier of improved efficacy, particularly
in fuels where conventional modifiers have been less effective than
desired; the provision of a method for improving low temperature fluidity
of fuel oils; and the provision of fuel oil compositions for improved low
temperature fluidity.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the present invention, it has been discovered that
adding to a fuel oil a composition of from about 1 to about 40 parts by
weight ethylene/vinyl acetate copolymer having a vinyl acetate content of
from about 10% by weight to about 50% by weight and a weight average
molecular weight of from about 2,000 to about 10,000, and 1 part by weight
esterified copolymer of at least one generally linear .alpha.-olefin of
from about 18 to about 50 carbon atoms and maleic anhydride in an
.alpha.-olefin to maleic anhydride molar ratio of from about 4:1 to about
1:2, the copolymer having a weight average molecular weight of from about
2,000 to about 20,000, the esterified copolymer having been esterified
with a plurality of aliphatic alcohols having from about four to about
forty carbon atoms, imparts to the fuel oil surprisingly improved low
temperature fluidity, provided that the alcohols include an eight carbon
alcohol making up from about 50 to about 85 molar percent of the alcohols.
The ethylene/vinyl acetate copolymer is well known for use in low
temperature fluidity modifiers as well as pour point depressants. Such
copolymers are described, for example, in Japanese Patent Application
Kokai: Sho 54-86505 to Takeshi, Nichihara et al. and, in a low vinyl
acetate content form, in U.S. Pat. No. 4,481,013 to Tack et al., bith of
which are incorporated herein by reference. As noted above, the copolymer
typically comprises about 10 to about 50 percent by weight vinyl acetate
monomer and has a weight average molecular weight of from about 2,000 to
about 10,000. Preferably, however, the vinyl acetate content is from about
30 to about 50 percent by weight and the weight average molecular weight
is from about 3,000 to about 7,000.
The esterified copolymer in the additive composition is derived from
esterification of an olefin/maleic anhydride copolymer of at least one
generally linear .alpha.-olefin and maleic anhydride in an .alpha.-olefin
to maleic anhydride molar ratio of from about 4:1 to about 1:2. Such
copolymers and esters thereof are well known, as are their methods of
preparation, and have been disclosed as being useful in pour point
depressants. See, for example, U.S. Pat. No. 4,240,916 to Rossi,
incorporated herein by reference. The generally linear .alpha.-olefin
contains from about 18 to about 50 carbon atoms. By "generally linear",
what is meant is that the .alpha.-olefin takes the form CH.sub.2
:CH(CH.sub.2).sub.x H, wherein x is an integer from about 16 to about 48,
or (less preferably) such form with minor aliphatic branching,
particularly up to about five methyl or ethyl groups. The most preferred
.alpha.-olefin is linear. Although it has been found that longer chain
lengths are most desirable, .alpha.-olefins up to only about 30 carbon
atoms are readily available. Thus, .alpha.-olefins of from about 18 to
about 30 carbon atoms (x=about 16 to about 28) are preferred, with the
most desirable having about 30 carbon atoms.
The molar ratio of .alpha.-olefin to maleic anhydride in the olefin/maleic
anhydride copolymer may be anywhere in the range of from about 4:1 to
about 1:2, although a molar ratio of about 1:1 is preferred. The
olefin/maleic anhydride copolymer has a weight average molecular weight of
from about 2,000 to about 20,000, preferably about 2,000 to about 20,000,
more preferably about 5,000 to about 8,000, most preferably about 6,000 to
about 7,000 as measured by GPC with polypropylene glycol as a reference
standard.
The olefin/maleic anhydride copolymer is esterified with a plurality of
aliphatic alcohols of from about four to about forty carbon atoms. The
alcohols are preferably saturated, and may be linear or branched. The
esterification may be carried out in any conventional manner except,
however, that at least one of the alcohols is an eight carbon alcohol. The
distribution of alcohols from four to forty carbon atoms is selected in
the manner well known in the prior art for coordination with the nature of
the paraffins in that fuel. In particular, as noted above, selection of
the array of aliphatic alcohol chain lengths to balance overall solubility
based on the paraffin content of the fuel to cause the additive to
precipitate out of the fuel at the desired temperature is well known.
Usually, the array of alcohols is a combination of aliphatic alcohols in
the range of from about eighteen to twenty-six or thirty carbon atoms. For
example, Alfol 20+, a mixture of 1-octadecanol (1-2% by weight),
1-eicosanol (49% by weight), 1-docosanol (30% by weight) and
1-tetracosanol (20% by weight), has been found to be an appropriate array
of alcohols for preparation of a low temperature fluidity modifier in many
fuels. However, it now has been found that inclusion in that array of
certain eight carbon alcohols achieves the surprising advantages noted
above.
A single eight carbon alcohol may be employed, but a mixture of eight
carbon aliphatic alcohols may be used. Preferably the eight carbon alcohol
is a branched aliphatic alcohol (with for example, one or, less
preferably, two methyl or ethyl branches), especially an ethylhexyl
alcohol, and optimally 2-ethylhexyl alcohol.
Complete esterification is desired, and so the alcohols are reacted with
the olefin/maleic anhydride copolymer in an optimal alcohol to maleic
anhydride molar ratio of about 2:1. However, complete esterification may
not be achieved and levels as low as 50% may be acceptable and 80% may be
typical. Thus, the alcohol to maleic anhydride molar ratio may be as low
as 1:1 or higher than 2:1 (such as 3:1), although generally there is no
commercial advantage to deviating significantly from 2:1.
The molar ratio of the eight carbon alcohol to the other alcohols in the
esterification reaction should be about 1:1 to about 5:1, preferably about
2:1 to about 3:1, such as about 2.5:1. Thus, about 50% to about 85%,
preferably about 65% to about 75%, such as about 70%, of the moles of
alcohols should be one or more eight carbon alcohols, and the same
percentage of the acid groups of the olefin/maleic anhydride copolymer
that have been esterified are esterified with the eight carbon alcohol.
Generally, the EVA copolymer and the olefin/maleic anhydride are mixed
together in a ratio of from about 1 to about 40 parts by weight
ethylene/vinyl acetate copolymer per 1 part by weight esterified
copolymer. Preferably, the weight ratio is from about 1:1 to about 20:1,
more preferably about 3:1 to about 10:1, even more preferably about 3:1 to
about 10:1. Generally, the esterified olefin/maleic anhydride copolymer is
present in a concentration of from about 2% by weight to about 30% by
weight, preferably from about 5% by weight to about 25% by weight, more
preferably about 10% by weight to about 20% by weight, such as about 15%
by weight, based on the total weight of the EVA copolymer and the
esterified olefin/maleic anhydride copolymer.
A sufficient amount of the additive mixture may be added to the fuel oil of
concern in a concentration sufficient to improve the low temperature
fluidity of the fuel oil. Thus, as used herein, "an effective amount" of
the composition is that amount that improves the low temperature fluidity
of the fuel oil. Generally, such amount provides from about 50 to about
2,500 ppm by weight of the two copolymers in the fuel oil, preferably from
about 100 to about 1,000 ppm by weight, such as from about 100 to about
500 ppm by weight. The additive may be incorporated into the fuel oil by
any of the standard known techniques.
The following examples describe preferred embodiments of the invention.
Other embodiments within the scope of the claims herein will be apparent
to one skilled in the art from consideration of the specification or
practice of the invention as disclosed herein. It is intended that the
specification, together with the examples, be considered exemplary only,
with the scope and spirit of the invention being indicated by the claims
which follow the example. In the examples, all percentages are given on a
weight basis unless otherwise indicated.
EXAMPLE 1
Esterification of a coplymer of aliphatic C.sub.30 olefin and maleic
anhydride (1:1 molar ratio, weight average molecular weight of 6700 as
determined by GPC with polypropylene glycol reference) was carried out as
follows. To a clean, dry 750-gallon stainless steel reactor were added, in
series, the coplymer (1,830 lbs.), Alfol 20+ (described earlier) (540
lbs.), 2-ethylhexanol (565 lbs.), a mixture of Witco 1298 Acid Soft and
CF1528 G.E. antifoam (11.75 lbs.; equivalent to 1 quart per 3,000 gallon
batch), and Solvent 14 (505 lbs.). The copolymer and the Alfol 20+ were
maintained prior to addition at 80.degree. C. and added at that
temperature. The resulting mixture was then heated to 120.degree. C. and
held at that temperature for 0.5 hours and the heat control was set at
165.degree. C. and the steam was throttled in 5.degree. C. increments to
165.degree. C. over a two-hour period. When the solvent covered the
standpipe of the reactor, the solvent return line to the reactor was
opened. Distilled by-product water was drained off from the decanter as
necessary. After the reaction mass reached 165.degree.-170.degree. C., it
was held there with a steady reflux for six hours or more to produce a
98.5% yield.
EXAMPLE 2
Samples of the copolymer ester prepared in Example 1, above, were mixed
with a commercially available thylene/vinyl acetate (EVA) copolymer having
a vinyl acetate content of from about 30% to about 44% and a molecular
weight in the range of from about 2,980 to about 6,150. Mixtures of the
copolymer ester of Example 1 and the EVA copolymer were prepared at
various concentrations of the copolymer ester; 5%, 15% and 30* by weight.
The mixtures were tested in various fuels under standard CFPP (cold filter
plugging point) procedures against the EVA copolymer with no copolymer
ester added, against the EVA copolymer with corresponding concentrations
of the olefin/maleic anhydride copolymer esters that were not prepared
with an equivalent array of alcohols as in Example 1, above, but without
the eight carbon alcohol, and against other related additives. The tables
below show the results that were obtained, with the numbers referring to
CFPP temperatures in .degree.F. and wherein Additive Concentration refers
to the concentration of the noted additive in the mixture with EVA,
"C.sub.x OMA" (x being a number or a range, such as 16 or 16-18) refers to
a copolymer of a C.sub.X olefin and maleic anhydride and "X" means
"reacted with". For Fuel A, the concentration of the mixture in the fuel
was 500 ppm, for Fuel B, the concentration of the mixture in the fuel was
300 ppm, and for Fuel C, the concentration of the mixture in the fuel was
1,000 ppm.
______________________________________
Fuel A (cloud point = -10.degree. F.; CFPP = -16.degree. F.)
Additive Concentration
Additive 5% 15% 30%
______________________________________
None.sup.1 -26 -26 -26
C.sub.16-18 OMA X cocoamine -32 -36
C.sub.16 OMA X Alfol 18+ and tallowamine
-20 -26
C.sub.16 OMA X Alfol 20+ and tallowamine
-20 -20
C.sub.18 OMA X Alfol 18+ and tallowamine
-16 -20
C.sub.20 OMA X Alfol 20+ and tallowamine
-16 -12
C.sub.16 OMA X Alfol 18+ and -18 -16
ditallowamine
Example 1.sup.2 -42 -46 -44
______________________________________
.sup.1 EVA copolymer with no additive was used and so the additive
concentration was 0. The CFPP results are shown for each concentration fo
comparison purposes.
.sup.2 The copolymer ester of Example 1, above, within the scope of the
invention.
______________________________________
Additive Concentration
Additive 5% 15% 30%
______________________________________
Fuel B (cloud point = 4.degree. F.; CFPP = -6.degree. F.)
None.sup.3 -20
C.sub.16-18 OMA X cocoamine -14
C.sub.16 OMA X Alfol 18+ and tallowamine
-6
C.sub.16 OMA X Alfol 20+ and tallowamine
-2
C.sub.18 OMA X Alfol 18+ and tallowamine
-6
C.sub.20 OMA X Alfol 20+ and tallowamine
-6
C.sub.16 OMA X Alfol 18+ and -6
ditallowamine
Example 1.sup.4 -20
Fuel C (cloud point = -22.degree. F.; CFPP = -28.degree. F.)
C.sub.16-18 OMA X cocoamine -38
C.sub.16 OMA X Alfol 18+ and tallowamine
-38
C.sub.16 OMA X Alfol 20+ and tallowamine
-34
C.sub.18 OMA X Alfol 18+ and tallowamine
-38
C.sub.20 OMA X Alfol 20+ and tallowamine
-34
C.sub.16 OMA X Alfol 18+ and -38
ditallowamine
Example 1.sup.5 -32 -34
______________________________________
.sup.3 EVA copolymer with no additive was used and so the additive
concentration was 0. The CFPP results are shown for each concentration fo
comparison purposes.
.sup.4 The copolymer ester of Example 1, above, within the scope of the
invention.
.sup.5 The copolymer ester of Example 1, above, within the scope of the
invention.
In view of the above, it will be seen that the several advantages of the
invention are achieved and other advantageous results attained.
As various changes could be made in the above methods and compositions
without departing from the scope of the invention, it is intended that all
matter contained in the above description shall be interpreted as
illustrative and not in a limiting sense.
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