Note: Descriptions are shown in the official language in which they were submitted.
~ 305~2CA
CM BON DIOXIDE TREATMENT CF EPOXY RESIN CONPOSITIONS
_
~ackground of the Invention
This invention relates to epoxy resin compositions. It further
relates to the curing of epoxy resins. In another aspect, it relates to
cure retardation of epoxy resin compositions for use as film-for~ing
corrosion inhibitors.
-- Epoxy resins are useful ma-terials for applications requiring a
fluid substance which can harden into a tough coating or mass after
application. Epoxy resins are used for such purposes as paint ~ases~
corrosion-resistant coatings for metal surfaces, and sand consolidation
compositions.
The mechanism by which a fluid epoxy resin solution hardens
into a tough substance involves a chemical reaction between the epoxy
resin an~ a curing agent such as an amine. The curing agent is mixed
with the epoxy resin prior to application of the resin for its intended
use and the curing reaction proceeds over a period of time which varies
depending npon the individual resin and curing agent.
For certain commonly-used types of epoxy resin/curing agent
formulations, the cure rate o~ the resin is so rapid that premixing and
transportation of the total formulation to the desired location is not
possible. This requires that mixing of the epoxy resin and the curing
agent ta~e place at the site of application, and thus increases the time
and expense of application of the epoxy formulation. The burden of
mixing the components of the composition is particularly great if the
site for application is remote from the sources of the chemicals or
presents particu].ar difficulties of tramsportation and physical mixing of
the chemicals.
2 ~ 3'7~
Such difficulties are encountered for example, in preparing
epoxy resin compositions for application to downhole metal surfaces in
oil and gas wells for protec-tion of the metal sur:Eaces against corrosion.
The oil and gas wells are often in locations remote from the source of
the chemicals. The most serious problems are posed by oEfshore oil
wells, in which preparation and application of such a
corrosion-inhibiting formulation must take place under very severe
environmental conditions and limita-tions of space, personnel and
equipment. Transportation of the separate chemicals and of equipment for
mixing them on site must be arranged, and additional personnel must be
assigned and trained. The expense of using cured epoxy resin
compositions could thus be reduced if the epoxy resin and the curing
agent could be premixed and transported to the site without significantly
reducing the effectiveness of the composition ~or its intended purpose.
It is therefore an object of the invention to provide a curing
composition for an epoxy resin.
It is a further object to provide a method for retarding the
cure of an epoxy resin composition.
Summary of the Inven-tion
According to the invention, there is provided a method of
retarding the cure of an epoxy resin. In the method, -the epoxy
resin/curing agent composition is contacted with carbon dioxide. The
carbon dioxide can be a constituent of a curing agent solution or of an
epoxy solution prior to mixing of the two solution~ to prepare the epoxy
resin/curing agent composition, or the carbon dioxide can be added to the
prepared composition. The carbon dioxide can be added to and maintained
in the composition in the form of a gas under pressure. The carbon
dioxide containing epoxy composition can be stored or transported to the
site of application and applied in the usual manner. The utility of the
epoxy composition, for example, as a corrosion-inhibiting formulation, is
not adversely effected by the carbon dioxide treatment.
- 3 ~ 3~
Brief Descr-ipt on of the Drawing
The Figure illustrates the corrosion inhibiting e~fectiveness
of the premixed epoxy/amine composi-tions prepared in Example II. The
presence of carbon dioxide in the premixed composition
significantly increases its shelf life
Detailed Descri~ of the Inven-tion
In the method of the invention, an epoxy resin composition
containing carbon dioxide is prepared. The carbon dioxide can be added
as a component of any constituent of the epoxy resin composition prior to
the preparation of the composition, or -the carbon dioxide can be added to
the prepared epoxy resin composition following mixing of the epoxy resin
and curing agent.
Preferably, the curing agent is treated with carbon dioxide
prior to the preparation of the epoxy resin/curing agent composition. In
this method, the carbon dioxide as a gas is added to an anhydrous
solution of the curing agent, and the resulting C02-rontaining curing
solution ls then mixed with a solution of the epoxy resin.
The addi~ion of carbon dioxide gas to the epoxy composition or
to a constituent of it can be carried out over a range of treatment
pressures from zero psig to 6000 psig but is preferably about 0~5 to
about 100 psig C02. The temperature at which CO2 treatment can be
carried out can vary widely but will generally be in the range of 0C to
100C. Ambient laboratory temperatures have been found to be suitable,
but colder and warmer temperatures encountered at well sites or other
application locations are acceptable.
The pressure of the C02 treatment can be any pressure effective
for addlng gaseous C02 to a solution of the epoxy resin or curing agent.
At room temperature in appropriate pressure equipment, the pressure of
the gaseous C02 would generally be within the range of about zero psig to
about 6000 psig, preferably 0.5 to lO0 psig.
The epoxy compositions of the invention include an amount of
carbon dioxide which is effective for retarding curing of the epoxy
resin. When used in a composition containing an amine curing agent, the
molar ratio of carbon dioxide to amine generally ranges from about lOO:l
37~
to about 1:100, preferclbly about 10:1 to ]:10, most preferably about 2:1
to about 1:2.
The invention method is applicable to any curable epoxy resin
having, on -the average, more than one vicinal epoxide group per molecule.
The epoxy resin can be saturated or unsaturated, aliphatic,
cycloaliphatic, aromatic or heterocyclic3 and may bear substituents which
do not materially interEere with the curing reaction. They may be
monomeric or polymeric.
Suitable epoxy resins include glycidyl ethers
prepared by the reaction of epichlorohydrin with a compound containing at
least one hydroxyl group carried out under alkaline reaction
conditions. The epoxy resin products obtained when the hydroxyl group
containing compo~lnd is bisphenol A are represented below by structure I
wherein n is zero or a number greater than O, commonly in the range of
O to 10, preferably in the range of 0 to 2.
/ O\ CH3
CH2 _ CHCH2Cl + HO ~ C ~ OH NaOH ~D
EPICHLORO~ RIN CH3
BISPHENOL-A
CN2--~ NCN20 ~ ~ OCN21N-CNz ~ ~ ~ C( ~ ~O-CN2CH--CN2
Other sui.table epoxy resins can be prepared by the reaction of
epich10rohydrin with mononuclear di- and tri-hydro~y phenolic compounds
such as resorcinol and phloroglucinol, selected po:Lynuclear polyhydroxy
5 ~ 7~
phenolic compounds such as bis(p-hydroxyphenyl)methane and 4,4'-dihydroxy
blphenyl, or aliphatic polyols such as 1,4-butanediol and glycerol.
Epoxy resins suitable for use in the invention have molecular
weights generally within the range of 50 to abou-~ 10,000, preferably
about 200 to about 1500~ The commercially available Epon~ 828 epoxy
resin, a reaction product of epichl.orohydrin and
2,2-bis(/~-hydroxyphenyl~propane ~bisphenol A) and having a molecular
weight of about 400, an epoxide equivalen-t (ASTM D-1652) of about
185-192, and an n value in structure I above of about 0.2, is presently
preferred because of the superior effectiveness, as shown in field tests,
of a composition containing Epon~ 828.
Additional epoxy-containing materials suitable for use in the
present invention include the epoxidized derivatives of natural oils such
as the triesters of glycerol with mixed long~chain saturated and
15 unsaturated acids which contain, e.g., 16, 18 and 20 carbon atoms. Such
natural oils are represented by formula Il:
H~C - 0 - C - R
HC - 0 - C - R
H2C - 0 - C - R
wherein R represents alkyl and/or alkenyl groups containing 15 to 19
carbon atoms with the proviso that epoxidation of said oils yields a
polyepoxide having more than one vicinal-epoxy group per molecule of
epoxidized oil. Soybean oil is a typical triglyceride which can be
converted to a polyepoxide sui~able for use in the instant invention.
Other polyepoxides suitable for use in the present invention
are derived from esters of polycarboxylic ac:ids such as maleic acid,
terephthalic acid, oxalic acid, succinic acid, azelaic acid, malonic
3~
acid, tartaric acid, adipic acid and the like with unsaturated alcohols
as described by formula III:
/ C - 0 R'
C 0 - R'
III
wherein Q represents a valence bond, or the following groupings:
1,2-phenylene, 1,4-phPnylene, methylene, dimethylene, heptamethylene,
vinylene, 1,2-cyclohexylene, 1,4-cyclohexylene 1,2-ethylenediol and the
like, and R' represents alkylene and branched alkylene groups containing
4 to 14 carbon atoms. Representative epoxidized esters derived from
materials described by structure (III) include the following:
di(2,3-epoxybutyl) tetrahydrophthalate, di(2,3-epoxyoctyl) oxalate,
di(2,3-epoxyisobutyl) adipate, di(3,4-epoxypentyl) succina-te,
di(4,5-epoxydodecyl) terephthalate, di(3,4-epoxyhexyl) phthalate,
di(2,3-epoxybutyl) tartrate, di(7,8-epoxytetradecyl) adipate,
di(e,4-epoxybutyl) glutarate~ di(2,3-epoxyhexyl) pimelate,
di(3,4-epoxyoctyl) suberate, di(4,5-epoxydecyl) azelate,
di(2,3-eopxyisohexyl) tetrahydroterephthalate and the like.
In addition to the foregoing, it is contemplated that suitable
polyepoxides can be derived from esters prepared from unsatura~ed
alcohols and unsaturated carboxylic acids described by formula IV:
3~7~
R"O - C - R"'
IV
wherein R" represents alkenyl and cycloalkenyl groups containing 4 to 12
carbon atoms and R"' represents alkenyl and cycloal~enyl groups
containing 4 to 12 carbon atoms. Reprlesentative epoxidized esters
include the following: 2,3-epoxypentyl 3,4-epoxybutyrate; 2,3-epoxybutyl
3,4-epoxyhexanoate; 3,4-epoxyoctyl 2,3-epoxycyclohexane carboxylate;
2,3-epoxydodecyl 4,5-epoxyoctanoate; 2,3-epoxyisobutyl
4,5-epoxydodecanoate; 2,3-epoxycyclododecyl 3,4-epoxypentanoate;
3,4-epoxyoctyl 2,3-epoxycyclododecane carboxy:Late and the like.
Other unsatura-ted materials which can be epoxidi~ed to give
resins suitable for use in the instant process include butadiene based
polymers such as butadiene-styrene copolymers, polyes-ters available as
derivatives of polyols such as ethylene glycol with unsaturated acid
anhydrides such as maleic anhydride, and esters of unsaturated
polycarboxylic acids. Representative polyepoxides derived from the
latter include the following: dimethyl 3,4,7,8-diepoxydecanedioate;
dibutyl 3,4,5,~-diepoxycyclohexan-1,2-carboxylate; dioctyl
3,4,7,8-diepoxyhexadecanedioate; diethyl
5,6,9,10-diepoxytetradecanedioa-te and the like.
Dimers of dienes such as ~-vinylcyclohexene-l from butadiene
and dicyclopentadiene from cyclopentadiene can be converted to epoxidized
derivatives which are suitable for use in the instant process.
Any agenk suitable for curing epoxy resins may be used in the
invention composition and method. Curing agents for epoxy resins include
amines, acids, anhydrides and aldehyde resins. The curing agent is used
in an amount effective for curing the amount of epoxy resin used.
Curing agen-ts suitable for use in the invention composition and
process include compounds having amino hydro~en atoms. These include
aliphatlc, cycloaliphatic, aromatic and heterocyclic amines. Examples of
curing compounds include aliphatic polyamines such as ethylene diamine,
diethylene triamine, triethylene tetramine, tetraethylene pentamine,
1,4-aminobutane, l,3-diaminobutane, hexamethylene diamine,
8 ~ 7~
3-(n-isopropylamino)propylamine, N,N'-diethyl-1,3-propanediamine,
hexapropylene heptamine, pen-ta(l-methyl propylene)hexamine,
tetrabutylenepentamine, hexa-(l,l-dimethylethylene)-heptamine,
di(l-methylbutylene)triamine, pen-taamylene hexamine,
tri(l,2,-trimethylethylene tetramine,
tetra(l,3-dimethylpropylene)pentamine,
penta(l,5-dimethylamylene)hexamine, 5-3lethylnonanediamine,
pen-ta(1,2-dimethyl-1-isopropylethylene)hexamine and
N,N'-dibutyl-1,6-hexanediamine.
A class of polyamines particularly suitable for use in the
invention are ~-alkyl- and N~alkenyl-substituted 1,3-diaminopropanes and
mixtures thereof. Examples of such polyamines include N-hexadecyl-
1,3-diaminopropane, N-tetradecyl-1,3-diaminopropane, N-octadecyl-1,3-
diaminopropane, N-pentadecyl-1,3-diaminopropane, N-heptadecyl-1,3-
diaminopropane, N-nonadecyl-l,3-diaminopropane, and N-octadecenyl-1,3-
diaminopropane. Various commercially available mixtures of N-alkylated
and N-alkenylated diamines can be used in the inven-tion. The presently
preferred polya~ine is a commercial product sold under the trademark
Duomeen~ T. This product is N-tallow-1,3-diaminopropane in which the
ma~jority of the tallow substituent groups are alkyl and alkenyl
containing from 16 to 18 carbon atoms each, wi-th a minority of
substituent groups having 14 carbon atoms each. It is presently believed
that the effectiveness of Duomeen~ T in the corrosion-inhibiting
composition stems from i-ts relatively high molecular weight, which
produces a long chain "net" to cover the metal surface, its
polyfunctionality, and its relatively high boiling poin-t, which permits
its use in high-temperature environments. Other commercially available
materials include N-coco-1,3-diaminopropane in which the majority of the
coco suostituent groups contain 12 to 14 carbon atoms, commercially
available under the trademane Duomeen~ C, and N-soya-1,3-diaminopropane,
which contains C18 alkenyl groups along with a minor proportion oi C16
alkyl groups.
Additional polyamines suitable ~or use ;n the invention can
contain 3 or more nitrogen atoms as illustrated by the following
examples: N-dodecyl-diethylene triamine, N-tetradecyl-diethylene
3'7~3
triamine, N-tetradecyl-dipropylene triamine, N--tetradecyl triethylene
tetramine and the corresponding N-alkenyl triamines.
Other curing axents which can be used include polyfunctiona]
nitrogen-containing compounds such as, for example, amino acids, amino
alcohols, amino nitriles, and amino ketones; sulfonic acids; carboxylic
acids; and organic anhydrides.
~ lcohols sui-table for use as optional components of the
invention system include alkanols containing at least one -0~1 functional
group. These include alcohols con-taining 1 to about 15 carbon atoms such
as methanol, ethanol, 1-propanol, 2-propanol, butanols, pentanols,
hexanols, heptanols, octanols, l-pentadecanol, and mixtures of these.
Polyols containing 2 to 5 carbon atoms such as ethylene glycol,
1,3-propanediol, 2,3-butanediol, glycerol and pentaerythritol can also be
use. Presently, methanol is preferred, particularly in an epoxy
composition containing xylene as the aromatic hydrocarbon diluent, Epon~
828 as the epoxy resin, and Duomeen~ T as the polyamine, because Duomeen~
T is soluble in methanol at room temperature and because of the
effectiveness of the resulting C02-treated corrosion inhibiting system.
When present in the composition, alcohol constitutes about 1 to abou-t 99,
preferably about 10 to about 60, most preferably about 20 to about 40
weight precent of the weight of the composition.
A hydrocarbon diluent can be used for the epoxy resin
compositions. Examples of hydrocarbon diluents suitable ~or use in such
compositions include the isomeric xylenes, toluene, benzene, naphtha,
cyclohexylbenzene, fuel oil, diesel oil, heavy aromatic oils, Stoddart
solvent, crude oil, and condensate from gas wells. Presently, xylene
is the preferred hydrocarbon diluent because it is an effective solvent
for the other preferred componen-ts and because of the corrosion-inhibiting
effectiveness of the resulting C02-treated composition.
The higher-boiling aromatic hydrocarbons are particularly
useful for epoxy resin compositions for application in deeper wells with
higher downhole temperatures and in high-temperature gas and oil wells
generally .
The components of the cure-retarded epoxy compositions can be
mixed in any order but it is presently preEerred to carry out the carbon
3~
dioxide treatment on a first solution of the curing agent prior to mixing
with a second solution o the epoxy resin. For example, a representative
curing agent solution contains xylene diluent, methanol and Duomeen~ T
(an N-alkyl-1,3-propanediamine) in about a 1:1:1 (mL:mL:g) ratio. A
representative epoxy solution contains an epoxy resin such as Epon~ 828
and xylene diluent with a resin:xylene ratio of 3:1 (g:mL). The
cure-retarded epoxy composition is pre]pared by first bubbling carbon
dioxide gas through the curing agent solu-tion at about 5 psig at room
temperature, and then mixing the CO2-containing curing solution with the
epoxy solution in pressure equip~ent while maintaining about 5 psig with
CO2. The resulting epoxy composition is then s-tored under pressure until
applied for its intended purpose.
The C02-con-taining composition can be stored and transported,
preferably under pressure, for a time which varies depending upon the
components of the system and the C02 treatment received. For the
representative CO2-retarded Epon~ 828 composition described above, the
effective shelf life would be expected to be at least 1-7 days. The
compositions~ when used within the time of effective C02 cure
retardation, are suitable for the same uses as untreated compositions.
Upon application of the composition to a surface, the cure reaction
proceeds and the resin sets to a coating or film.
The invention C02-treated epoxy composi~ion is usefwl for any
purpose for which conventional epoxy resin compositions are used. For
example, the epoxy composition can be used for protecting oxidizable
metal surfaces, particularly surfaces of objects made of iron and steel.
It is useful for treating metal surfaces of equipment in oil, gas and
geothermal wells which are subjected to high temperatures and pressures
and corrosive chemical agents. It is also useful for treating pipelines
in which water-con-taining fluids are transported.
~own-hole treatments with the epoxy compositions can be
effected by a variety of methods known in the art depending upon the
particular chemical and physical characteristics of the well being
trea-ted. In practice, a CO2-treatecl corrosion-inhibiting epoxy
composition can be maintained in storage tanks or drums for about a week
3~ or more prior to pumping the mixture downhole.
L37~
Example I
Preparation of CO2-Containing Solutions
A 25g portion of a first cllring agen-t solution containing equal
weights of Duomeen~ T methanol and xylene was charged to a 150 mL
pressure bottle equipped wi~h a magnetic stirrer and pressure gauge. For
30 minutes a-t ambient conditions, carbon dioxide gas was introduced into
the stirred solution at 5 psig pressure. The weight of the system
increased by 1.23 g due to absorption of carbon dioxide. This represents
a molar ratio of CO2 to amine of approximately 1:1. An epoxy resin
solu-tion was separately prepared by mixing ~pon~ 828 and xylene in an
epoxy resin:xylene weight ratio oE 3:1. One volwne of the
epoxy resin solution was then mixed with four volumes of the CO2-treated
amine solution. The resulting composition was stored under CO2 pressure
until used for the corrosion tests described below.
Example II
Corrosion Inhibition Tests with CO2-Containing Solutions
A series of laboratory corrosion inhibition tests was carried
out in l-liter Erlenmeyer flasks equipped with magnetic stirring bars,
under laboratory conditions designed to simulate corrosive oil-water
environments -typical of field drilling sites. A chaxge of 50 mL of crude
oil and 950 m~ of synthetic brine was used in each run. A slow stream of
carbon dioxide was bubbled through the solution during each test to
maintain the mixture near saturation with CO2 at ambient conditions.
Af-ter 950 m~ of syn-thetic North Sea water (93.1g CaCl2 2H2O, 46.4g
NgCl2 6H2O and 781.1g NaCl per 5 gal distilled H2O) was charged into the
Erlenmeyer flask, the CO2-treated corrosion inhibitor system containing
amine, epoxy resin, alcohol and hydrocarbon diluent was charged to the
flask followed by addition of Teesside crude oil. A carbon steel probe
was suspended in the s-tirred oil-wa-ter mixture maintained a-t about 49C
during each run. The rate o~ corrosion and the pitting index were
3t7~D
dete~mined using a Corrator~ monitoring system available from
Rohrback instrl~ents. Results are summarized in Table I.
7~
TABLE I
Time l:lapseda
Run Before C02 Corrosion Pitting
No. Testing (Hrs) Treatmen-t Rate mpy Index
. ~ ,
1 0 YES ~.02 0.02
2 0 N0 0.04 0.0
3 1 ~S 0.06 0.03
4 l N0 0.10 1.03
4a 1.5 N0 0.41 1.2
2 YES 0.02 0.02
6 2 N0 5.6 1.6
7 4 'nES 0.07 0.0
8 4 N0 5.8 2.6
9 24 YES 0.02 0.01
24 N0 5.6 3.1
11 672 YES 2.8 0.8
12 672 N0 5.2 2.8
a The time elapsed before testing indicates the time in
hours that the total compositions were stored on the shelf at ambient
temperature before the corrosion test was run. The invention system was
maintained under positive C02 pressure throughout the aging period of
about 28 days.
Invention runs 1,3,5,7, and 9 demonstrate that the carbon
dioxide pressured system containing epoxy resin, polyamine, methanol and
xylene has longer shelf life than a similar unpressured system of control
runs 2,4,4a,6, 8 and 10. Referring to i~vention run 5 and control run 6,
it can be seen -that use oE the C02-pressured composition resulted in a
lower corro.sion rate (0.02 mpy) than did the unpressured control system
(5.6 mpy). It is noteworthy that the invention composition of run 9,
even after storage under C02 pressure for 24 hours, gave a low corrosion
rate of 0.02 mpy compared with the much higher corrosion rate of 5.6 mpy
of the 24-hour control run 10. A review of the pitting index values
confirms the increased effectiveness of the system when stored under C02.
The run at 672 hours shows the superiority of the C02-treated system over
an extended period of time.
