Note: Descriptions are shown in the official language in which they were submitted.
'1 ~ D ~ Y
PATENT 186-P-US03715
ACIDIZED FRACTURING FLUIDS CONTAINING HIGH MOLECULAR WEIGHT
POLY(VINYLAMINES) FOh! ENHANCED OIL RECOVERY
TECHNICAL FIELD
The invention relates to the use of high molecular weight
poly~vinylamines) in acidized fracturing fluids compositions.
; BACKGROUND OF THE INVENTION
Water soluble polymers such as polytN-vinylamides), frequently re-
10 guire high molecular weight to develop satisfactory properties for high
performance applications. Low to medium molecular weight poly(N-vinyl-
formamide) and poly(N-vinylacetamide) have been pre~ared by conventional
solution polymerization in water and alcohols using oil-soluble and
water-soluble initiators. However, poly(N-~inylamides) of high molecuiar
15 weight are difficult to produce by conventional solution polymeri~ation
in that the polymer product obtained under useful conditions is a gel
~ ~ which is difficult to handle. In addition, problems with high solu~ion
;~ viscosity and poor heat transfer ma~e such synthesis impraotical on a
commercial scale.
Nonetheles~, it was believed by the present inventors that the ap-
~,
plications performance of polytvinylamides) and poly(vinylamines) could
be er~anced by the preparation and use of homopolymers of ~ery high
molecular weight ~>106),
U.S. 4,500,437 discloses acrylamide copol~mers and terpolymers con-
2~ taining N-vinylformamid~ and N-vinylacetamide~prepared by inverse emul-
sion p~lymerization in Examples 67-70 with the polymers of Examples 68
and 70 having a molecular weight below 100,000, i.e ~105. Example 20
shows the preparation of poly~vinylformamide) by solution polymerizatiorl.
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V.S. 4,421,602 discloses linear basic polymers containing from 90 to
10 mole~ of copolymerized vinylamine units and from 10 to 90 mole% of
copolymerized N-vinylformamide units. This patent teaches that the
polymers can be prepared by solution polymerization in water, a water-
soluble solvent or a mixture of water and a water-soluble solvent and
actually shows such solution polymerization in the examples. It is
suggested that the polymerization can also be carried out as a water-
in-oil emulsion polymerization in a ~ater-immiscible solvent, but there
are no examples of such polymerization.
U.S. 4,018,826 discloses the ~r~earation of poly~vinylamine) salts
of mineral acids by polymerizing vinylacetamide with a free radical
polymerization catalyst, and hydrolyzing the poly(vinylacetamide) to the
desired amine salts by contacting the poly(vinylacetamide~ with an
aqueous solution of the corresponding mineral acid. Poly(vinylamine)
15 product of about 3,000 to about 700,00Q molecular weight ~4,000 to about
; 1,000,000 for the salt product) is suggested.
U.S. 3,558,581 discloses homo- and copolymers of N-vinyl-N-methyl-
amine by hydrolysis of the corresponding polymers of N-vinyl-N-methyl-
formamide with mineral acids.
U.S. 3,597,314 discloses a water-soluble polymer consisting
essentially of units derived from N-vinyl-N-methylformamide having
60-100% of the formic acid radicals of the polymer split off by acid
hydrolysis. There is no disclosure regarding inverse emulsion polymer-
ization.
GB 2,152,929 is directed to a process for producing N-substituted
formamides for use in producing N-vinylformamide by thermally decomposing
- N-(alpha-alkoxyethyl~formamide in the gas phase. It is suggested that
the N-vinylformamide can be bulk polymerized, solution polymerized using
an aqueous solution or an organic solukion, or emulsion polymerized
singly or together with a monomer used conventionally for producing
water-soluble polymers suitable for making flocculants, in the presence
of a polymerization initiator of azo compounds. The thu~ obtainPd
poly(vinylformamide) is hydrolyzed under acidic or basic conditions to
obtain a cationic polymer of poly(vinylamines).
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D. J. Dawson, et al., "2O1y(vinylamine hydrochloride). Synthesis
and Utilization for thq Preparation of Water-Soluble Polymeric Dyes,"
J. Am. Chem. Soc., 98:19, 5996 ~1976) discloses the pre~aration of
N-vinylacetamide and its polymerizaticn in solution followed by acid
hydrolysis to poly~N-vinylamine hydrochloride).
Representative o~ the numerous prior art references relating to
water-in-oil emulsion polymerization of water-soluble monomers are the
following patents: U.S. 2,982,749: 3,278,506: 3,284,393; 3,957,739;
3,975,341; ~,078,133; and ~,312,969.
R. H. Summerville, et al., "Synthesis of N-vinyl Acetamide and
Preparation of Some Polymers and Copolymers," Polym. Reprints, 2~, lZ
(1983) discloses that the inverse emulsion polymeri~ation of
N-vinylacetamide initiated by sodium persulfate in water and cyclohexane
using *Igepal surfactancts was tried without success.
U.S. 4,217,214 discloses that polyvinylamine hydrochloride having a
molecular weight of about 5 x 105 or greater has been found to be
particularly effective as a flocculating agent in wastewater systems.
The exam~les disclose the use of a poly(vinylamine) hydrochloride having
a molecular weight of 2 x 106 and state that the poIy~vinylamine)
' 20 hydrochloride used is prepared as described in U.S. 4,018,826.
U.S. 4,623,699 discloses linear, basic polymer powders which contain
units of the formula -CH2-C~(MH2)- and have a Fikentscher K value
from 10 to 200 are ~repared by eliminating the formyl groups from
N-vinylformamide polymer powders with a gaseous hydrogen halide in the
presence of not more than 5~ by weight, based on the polymer used, of
water.
JP 61~1417l2 discloses a method for producing N-vinylcarboxylic acid
amide polymers by a procedure in which an aqueous solution of
N-vinylcarboxylic acid amide is dispersed in a hydrocarbon-type
dispersing medium using an oil-soluble eolymer dispersion stabilizer
followed by radical ~olymeri~ation.
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SUMMARY OF THE INVENTION
According to the present invention, very high molecular weight
poly(N-vinylamides) can be prepared by an inverse amulsion polymeriza-
tion process. The present invention provides an inverse homopolymer
emulsion consisting essentially of 10-70 wt% of an aqueous solution
containing 10-90 wt~ of a homopolymer of an N-vinylamide of the formula
O
ll 2
R
wherein R and R represent hydrogen or a Cl-C4 alkyl group, colloidally
dispersed in a hydrocarbon liguid which is a C5-Clo alkane and, in ad-
dition, toluene and xylene when R=alkyl, a xylene compound, the homo-
polymer being at least 10 average molecular weight and the emulsionpossessing a viscosity less than 10 cps at 15~ solids, 60 rpm Brookfield
~7.9 sec 1) and 20C.
The method for preparing the inverse, or water-in-oil, emulsion
involves colloidally dispersing an aqueous solution containing 10-90 wt%
water-soluble N-vinylamide of the above formula in the hydrocarbon liquid
using a surfactant having an HLB value from 4 to 9, the weight ratio of
monomer-containing aqueous solution to hydrocarbon liquid being prefer-
ably in the range from 1:2 to 2:1, and polymerizing the monomer using an
azo-type free radical initiator.
The resultant very high molecular wei~ht polymer emulsion has a low
viscosity ranging from 2 to less than 10 cps at 15% solids, 60 rpm Broo~-
field and 20C, thus eliminating problems of solution viscosity which
arise when the polymer is prepared by a solution polymerization process.
In addition, the low viscosity homopolymer emulsion is easy to handle and
can be used directly.
One such use of the vinylamide homopolymer emulsions is in the pre-
paration of vinylamine homopolymers of at least a 106 average molecular
weight by acid or base catalyzed hydrolysis of the homopolymer, prefer-
; ably as the emulsion. The use o~ the mineral acid in the hydrolysis step
or in acidifying the base hydrolysis product ~rovides the poly~vinyl-
amine) as the salt of such acid.
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The very high molecular weight, water~soluble poly(N-vinylamides)
and the derived poly(vinylamines) have applications in the fields of
water treatment, enhanced oil recovery and pa~ermaking. For example, the
derived poly(vinylamines) can be used as an important component in oil
field chemical compositions such as drilling mud compositions, cements
for drilling holes, completion fluids, and acidized fractusing fluids.
Solution rheology ~thickening efficiency and viscosity ses~onse to shear
rates in the range of l to l,000 sec ]L) of the poly~v;nylamines) at a
0.5 to l~ concentration in low level salt solutions, e.g. Z~ KCl solu-
tion, is important in oil field chemical compositions for many applica-
t;ons. The very high molecular weight of the polymers affords better
viscoiEying and rheology.
In enhanced oil recovery (EOR) applications the poly~vinylamines) of
the invention provide compositions having improved viscosity stability at
90C and improved viscosity retention in sea water, Most commercially
available eolymers fail under both these conditions. Hydrolyzed poly-
acrylamides fail in sea water solution at elevated temperatures due to
precipitation of the polymer in the presence of calcium ions in the sea
water. Xanthan polymer is insensitive to calcium ions. However, at high
2~ temperatures the polymer chains uncoil and lose their viscosifying
efficiency.
In general such EOR compositions would comprise sea water containing
about lO00 to 2000 ppm of the poly(vinylamine) and have a l0 to 20 cps
Brookfield viscosity at 7.9 sec l (60 rpm) and 90C. Very high molecu-
lar weight vinylamine polymers according to the invention seem to showimproved stability at high temperature and calcium salin;ty - a set of
conditions useful in hi~h temperature EOR viscosifying applications.
When used in acidized fracturing fluids, the poly(vinylamines) of
the invention result in improvad viscosity stability in concentrated
hydrochloric acid solution at 70C. ~ost commercial cellulosic polymers
currently used in this application fail due to the breakdown of the poly-
mer backbone under these conditions. Such fluids comprise about 0.2 to
2 % poly~vinylamine1 and 5 to 28 % aqueous hydrochloric acid-a~d hsv; ~
:*FANN 35 viscosity of l0 to l00 cps at 300 rmp, 510 sec and
RlBl sensor
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Thus there is also provided a process for well stimulation by
fracture acidi~ing with an agueous acidic solution wherein the acidic
solution is injected into the well to contact a formation under pressure
sufficient to fracture the formation, the acidic solution containing as a
viscosifier a vinylamine homopolymer having a molecular weight greater
than 106.
A further emhodiment of the present invention is a drilling mud
com~osition with good rheology. Such drilling mud compositions comprise
0.1 to 1 wt% poly~vinylamine), 0 to 10 wtX salt and 0.5 to 5 wt~ clay
10 dispersed in water.
Also provided by the invention are completion fluids exhibiting high
viscosity in saturated brine solution as well as high temperature vis-
cosity stability. A typical completion fluid comprises a saturated salt
solution containing 0.2 to 2 wt% poly(vinylamine).
The present invention also provides an increase in retention, drain-
age rate and flocculation in a papermaking process comprising the depo-
sition of a pulp stoc~ to form a nonwoven shePt by adding to the pulp
stock polytvinylamines) according to the invent;on.
BRIEF DESCRIPTION OF THE DRAWING
The sole Figure is a graphic representation of the effect of high
molecular weight poly(vinylamine) and poly~N-vinylacetamide) according
to the invention and other prior art polymers in the flocculation o~
kaolinite clay.
2~
DETAILED DESCRIPTION OF THE INVENTION
Poly(N-vinylamides) of molecular weight at least 106, preerably
3 x 106 to 15 x 106, are prepared via an inverse emulsion polymeriza-
tion process by reacting the following composition under an inert atmo-
30 sphere:
1. water-soluble N-vinylamide monomer,
2. water,
3. hydrocarbon liquid,
4. water-in-oil emulsifying agent, and
5. a nitrogen-containing ree radical initiator.
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The aqueous solution comprising the first two components contains
10 to 90 wt~, preferably 50 to 70 wt~, of a water-soluble N-vinylamide of
the formula
O
11
R~-N~H=CH2
where R and R1 represent hydrogen or an alkyl group having 1-4, prefer-
ably 1-2, carbon atoms, especially a methyl group. The weight ratio of
10 monomer-containing aqueous solution to hydrocarbon liguid may be varied
widely depending upon the monomer used, but preferably is about 1:2 to
2:1.
The suitable hydrocarbon liquids for use in the invention are
immiscible with water and do not significantly dissolve the monomers
in the presence of water. Such hydrocarbon liquids are exemplified by
acyclic and cyclic C5-ClQ alkanes such as hexane, octane, decane, and
decahydronaphthalene (decalin) and, in addition, certain aromatic hydro-
carbons for N-vinylacetamides and the aromatic hydrocarbons toluene and
xylene. Contemplated as the functional equivalent o~ toluene and xylene
when R is an alkyl group in the monomer formula are ethylbenzene and
tetrahydronaphthalene (tetralin). The preferred hydrocarbon liquids
are the C5-C10 acyclic alkanes.
The stabili~ing system comprises suitable emulsifying agents, or
; surfactants, having a hydrophilic lipophilic balance (HLB? Yalue from
4 to 9, preferably 4 to 7.5, and include sorbitan fatty acid esters such
as sorbitan monostearate~ oleate, laurate or palmitate: polyoxyethylene-
sorbitan fatty acid esters, i.e. reaction products of one mole of the
aforementioned sorbltan fatty acid esters with from 4 to 40 moles of
ethylene oxide: polyoxyethylene sorbitol esters~of fatty acids; and mix-
tures~thereof. The preferable quantity of surfactant is 5 to 20 wt%based on the monomer-containing agueous solution.
The free radical initiator should be one of the azo compounds well
known in the polymerization art such as 2,2'-azobis(isobutyronitrile);
2,2'-azobist2-amidinopropane) hydrochloride; 4,~'-a~obis(4'-cyano
pe~ntanoic acid~ and the llhe~ Persulfates and hydrogen peroxide have
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- been found not to be suitable in practicing the invention. Redox
catalyst systems may also be used comprising the azo initiators with a
reducing agent typically used in the art. The amount of free radical
initiator can be varied widely depending upon reaction te~peratures, rate
of polymerization, degree of polymer;zation to be obtained, but prefer-
ably is in the range of 0.001 to 0.5 mole% of the monomer used.
; The polymeriæation is usually carried out under an inert atmosphere,
preferably under nitrogen. The reaction temperature is preferably in the
range of 40-60C. A high temperature, i.e. >60C, may cause side reac-
tions unfavorable to the polymer such as crosslinking or chain transfer.
A lower temperature may be impractical bscause of long reaction times.
The homopolymer product can be isolated from the emulsion by adding
a flocculating agent and filtering. The precipitated product is then
washed and dried. Generally, a polar organic solvent which is a good
solvent for the surfactant but a poor solvent for the polymer, e.g.
acetone, is used to aggregate the polymer. The precipitated polymer is
filtered and washed to remove the surfactant. The dried and purified
polymer of very high molecular weight i5 in the form of a fine powder and
is water soluble.
The vinylamide homopolymer products are hydroly~ed to vinylamine
homopolymers of at least 106 a~erage molecular weight in the presence
of acids or bases. More desirably, vinylamine homopolymers of 1.8 x 106
to 9 x Io6 molecular weight or more are obtained. The vinylamine homo-
polymers suitable for use in acidized fracturing fluids are greater than
about 50% hydrolyzed, preferably greater than about 90%, to about 99+%
hydrolyzed.
Suitable acids for the hydrolysis include mineral acids such as
hydrochloric, hydrobromic, sulfuric, phosphoric and perchloric acid; and
organic acids such as trifIuoroacetic acids and methanesulfonic acid.
The bases which can be employed include alkali and alkaline earth hy-
droxides such as sodium hydroxide, potassium hydroxide, calcium hydroxide
and barium hydroxide; and quaternary ammonium hydroxides such as tetra-
methyl ammonium hydroxide. The quantity of the acid or base reguired may
vary widely, depending upon the degree of hydrolysis desired and reaction
~5 conditions. Approximately, l to 3 equivalents of the acid or base per
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g
e~uivalent of the polymer is preferred to achieve essentially complete
hydrolysis.
The hydrolysis can be performed in various solvents, including
water; liquid ammonia, alcohols such as methanol, ethanol, isopropanol,
and t-butanol; amines such as methylamine, dimethylamine, ethylamine and
the like; and hydroxy amines such as ethanolamine. However, it is much
preferred to simply add the acid or base in water to the water-in-oil
emulsion.
The temperature of the hydrolysis may range from 20 to 200C
depending upon the type of polymer and hydrolysis employed. Generally,
hydrolysis proceeds more rapidly for poly(N-vinylformamide) than for
poly(N-vinylacetamide). Thus, hydrolysis of poly(N-vinylformamide) can
be carried on under milder conditions, i.e. at lower temperatures and
shorter reaction times than for poly(N-vinylacetamide~. The preferable
temperature range of a base hydrolysis is 70 to 100C which is lower than
that of acid or base hydrolysis of N-vinylacetamide in the range of 110
to 200C.
The hydrolyzed polymer products thus obtained comprise the repeating
free amino-containing units of the formula
~H2CHtn
NH2
in the case of base hydrolysis, and amino-containing units of the formula
~CH~CH~n
NH3 X
in the case of acid hydrolysis, where X represents the anion corres-
ponding to the acid employed in the hydrolysis.
Poly~vinylamine) is preferably iso]ated in the salt form to prevent
adsorption of a~mospheric carbon dioxide. The polymer salt is isolated
by acidifying the hydrolysis mixture to cause the polymer to precipitate.
Th~ precipitated polymer generally is a gum, but a fibrous material can
` 35 be obtained after redissolving, followed by reprecipitation in methanol.
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The products of this invention are high molecular weight poly(N-
vinylamides), especially poly(N-vinylformamide) of 3-15 x 106 mol wt
and poly(N-vinylacetamide) of 1.3-5 x 10 mol wt, and the derived
poly(vinylamine) and poly(vinylamine) salts.
These polymeric materials, which may also contain up to 25 wt~
copolymeri~able monomers such as, for example, acrylamide and
N-vinylpyrrolidone, provided the polymer maintains sufficient water
solubility, are particularly useful as flocculants, retention agents, and
thickeners in the areas of water treatment, enhanced oil recovery and
papermaking. These polymers may also be used as corrosion inhibitors,
photograehic chemicals, surfactants, protein hardeners, ion exchange
resins, and as ingredients in the preparation of drugs, food dyes,
herbicides and pesticides.
With regard to acidized fracturing fluids for well stimulation, such
compositions would comprise 0.2 to 2~, preferably about 0.5%, high
molecular weight polytvinylamine) according to the invention as a
viscosifier in 5 to 28% aqueous hydrochloric acid and optionally 0.5 to
1% crosslinking agent, based on weight of poly~vinylamine), Suitable
crosslinking agents include, for example, organic titanate complexes,
20 epichlorohydcin, hexamethylene diisocyanate, glyoxal, butylene diol
diacrylate, terephthalaldehyde and glutaraldehyde with the latter two
~ preferred a' lo-~er pH. 5he fracturing fluid CompOSit~QnS should have a
`~ FANN 35 viscosity of 10 to 100 cps at 300 rpm, 510 sec and RlL
sensor.
These acidi~ed fracturing fluids are injected under pressure into a
well to contact a formation. The pressure must be sufficisnt to ~racture
the formation.
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EXAMPLE 1
This Example shows a preparation of a very high molecular weight
; poly~N-vinylformamide) by inverse emulsion polymeri2ation.
`~ Sorbitan monostearate*(spAN 60 surfactant, HLB 4.7, 2.5g) was dis-
solved in octane (90g) and the resulting solution was transfer~ed to a
reaction kettle. The reactor was purged with nitrogen and kept in a
r~
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nitrogen atmosphere throughout the polymeri~ation. The N-vinylformamide
solution (lSg in 30g of water) was degassed and added to the reactor at
the rate of 2.5 ml/min with vigorous agitation. ~The N-~rinylformamide
was purified hy vacuum distillation at 70C, 1 torr, prior to use.)
While the reaction mixture was heated to 50C, 2,2'-azobis(2,4-dimethyl-
pentanitrile) ~Vazo 52 initiator, 0.05g) was charged. After 3 hours at
50C with agitation, a stable polym~ric emulsion was produced having a
viscosity of 3 cps. The solid polymer product was recovered by breaking
the emulsion by the addition of acetone. The isolated N-vinylformamide
homopolymer had a molecular weight of 6.7 x 10~ as measured by light
scattering and a viscosity of Zl,OOO cps as a 5% aqueous solution.
EXAMPLE 2
The vinylformamide homopolymer (lOg) of Example 1 was dissolved in
water (990g) and then mixed with 50% aqueous sodium hydroxide (11.3g).
The resulting mixture was heated for 8 hours at 80C under a nitrogen
atmosphere. To the reaction mixture was added concentrated hydrochloric
acid until the polymer precipitated. The acid solution was decanted.
The precipitated polymer was redissolved in water and reprecipitated with
methanol. The vinylamine homopolymer hydrochloride salt had a viscosity
of 400 cps at 1% aqueous solution.
EXAMP~E 3
This Example shows the preparation of a ~ery high molecular weight
~5 poly(N-vinylacetamide) by inverse emulsion polymerization.
The N-vinylacetamide was prepared according to the method taught in
U.S. Patent 4,018,82~. The N-vinylacetamide was purified as follows:
The crude N-vinylacetamide (1 ~g) was flash distilled at 70-7~C, 1 torr.
Approximately two-thirds of the material was distilled to give a 70:30
N-vinylacetamide/acetamide mixture. This mixture (lOOg) and toluene
(600g) were placed in a 1000 ml beaker and the resulting mixture was
stirred well. The yellow toluene solution was decanted from insoluble
solids which were washed twice with 50g of fresh toluene. The toluene
solutions were combined and washed with 25g of brine. The yellow brine
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solution was discarded. The toluene solution was then extracted four
times with 130 ml of water. The aqueous solution was back extracted with
25 ml of methylene chloride. The methylene chloride solution was dis~
carded. The agueous solution was saturated with sodium chloride and
extracted four times with 330 ml methylene chloride. After removing the
methylene chloride under reduced pressure, 42g of pure N-vinylacetamide
(60% recovery) was obtained.
A mixture of N-vinylacetamide (15g), water (45g), xylene t90g), and
SPAN 60 surfactant t4g) was polymerized in the same manner as described
in Exam~le 1, using 2,2'-azobis(2-methylpropionitrile) AIBN t0.08g) as an
initiator. The N-vinylacetamide homopolymer was precipitated by addition
of acetone, and had a molecular weight of 1.5 x 106, as determined by
gel permeation chromatography.
EXAMPLE 4
The N-vinylacetamide homopolymer of Example 3 (lQ g~ was dissolved
in water and mixed with concentrated hydrochloric acid t2 mole eguiv-
alents). The resulting mixture was heated to reflux (about 110C) for
48 hours. To the reaction mixture was added concentrated hydrochloric
acid until the polymer precipitated. The acid solution was decanted.
~ The precipitated polymer was redissolved in water and reprecipitated with
- methanol yielding 8.8g of product having a viscosity of 324 cps as a 1 %
aqueous solution.
EXAMPLES 5-9
N-vinylformamide ~NVF) was polymerized in the same manner as de-
scribed in Example l. The data regarding the polymerization recipes and
` the resulting emulsions are set forth in Tables 1 and 2, respectively.
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T A B L E
SPAN VAZO
EXAMPLE ~ g~ WATER(g) XYDROCARBONtq) 60tq) 52tq) ADDITIVE(q)
Octane 55 2.5 0.05 ---
6 15 30 Octane 55 2.5 0.05 0.25 Vinol 125
35 7 15 10 Octane 75 2.5 0,05 ___
j 8 15 ~0 Hexane 90 2.5 0.05 ---
9 lS 30 Hexane 90 2.5 0.05 0.25 Poly(vinylamine)
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T A B 1 E 2
EMULSION HOMOPOLYMER
EXAMPLE VISCOSITY (cps)MOLECULAR WEIG}IT
4 7 x 106
6 4 7 x 106
7 4 6 x 106
8 4 6 x 106
9 4 6 x 106
EXAM;PLE 10
In this exampla the inverse emulsion polymerization of N-vinyl-
formamide according to Example 1 was attempted using toluene, xylene
and kerosene individually as the hydrocarbon liquid phase. In each
instance a high molecular weight N-vinylformamide polymer was obtained,
but the emulsions were unstable and broke.
EXAMPLE 11
This example shows the need to use an azo-type initiator. Follow-
ing the procedure of Example 1 using sodium or ammonium persulfate as the
initiator resulted in failure in that no polymer was obtained. This
failure is believed due to a possible redox reaction occurring between
the monomer and the persulfate.
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EXAMPLE 12
In this example poly(N-~inylformamide) was prepared accordinq to the
solution polymerization procedure of Example 12 in U.S. Pate~t 4,421,602.
The isolated polymer was determined as having a molecular weight o~
1.4 x 105 by aqueous qas phase chromatography~(GPC).
EXAMPLE 13
A poly(N-vinylformamide~ emulsion was prepared according to the
procedure of Example 69 in U.S. Patent 4,500,437. The resultant pol~ner
emulsion was paste-like and unstable. The isolated poly(N-vinylformamide)
had a molecular weiqht of 5.1 x 10 as detennined by a~ueous GPC.
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EXAMPLE 14
The polymerization of N-vinylformamide was performed according to
the procedure of Example 20 in U.S. Patent 4,500,437. The product was
a viscous liquid indicating a molecular we;ght of less than 5 x 103.
EXP~IPLE 15
The effect of poly(vinylamine), poly(vinylamine hydrochloride1 and
poly(N-vinylacetamide) according to the invention in flocculation of
kalonite clay was tested and compared to commercial polymers, namely,
lO polyacrylamide, polyacrylic acid ancl Guar gum.
A 0.01% polymer solution (12.5 ml) was added to an equal volume of a
stock kaolinite clay slurry ~5.5g in 200 ml of a 2% agueous KCl solution)
in a 25 ml stoppered graduated cylinder. The cylinder was inverted five
times. The clay level was measured after 3, 6, 9, 15, 30, 45 and 60 min-
15 utes. Results are shown in Fi~ure l. It can be seen that the high mo
lecular weight poly(vinylamine) has excsllent flocculation activity. The
rate of sedimentation and the compact nature of floc are o~ interest in
water treatment applications.
EXAMPLE 16
This E~ample shows the application of a poly(vinylamine) according
to the invention in enhanced oil recovery. Two vinylamine homopolymers
and two commercially available polymers, namely xanthan and a hydrolyzed
polyacrylamide, were evaluated at 1500 ppm in synthetic sea water using a
low shear Brookfield ~iscosity at 7.9 sec 1,
T A B L E 3
Low Shear Rheoloqv in Sea Watera
Brookfield Viscosity ~cps)b
Polymer Conc (ppm)R.T. 90C
~inylamine (7 MM) 1500 16 13
Vinylamine (O.6 MM) 1500 6 2
Xanthan XC (2 ~M~ 1500 S0 4
Hydrolyzed Polyacrylamide (2 MM) 150015 3
~ Sea Water = 3% NaCl ~ 0.3~ CaC12; pH - 6
b Nodel LVF, 7.9 sec~l
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It can be seen from Table 3 that the vinylamine homopolymer of about
ixlO molecular weight outperformed the com~ercially available polymers
as well as the lower molecular weight poly(vinylamine). The vinylamine
homoeolymer demonstrated much imp~oved viscosity stability at,the
elevated (90C) temperature compared to the other polymers.
EXU~PLE 17
In this Example the very high and the low molecuiar weight vinyl-
amine (VAm) homopolymers were compared with guar having a molecular
10 weight of about ZMM for use in a fractllre acidi~ing composition. The
polymer concentration was 0.5% and the viscosity was measured using a
FANN 35 viscometer, Rl~l sensor at 510 sec
T A B L E 4
Fracture Acidizinq
Room Temperature 70C - 3HR
HCl VAm (0.6 MM) VAm ~7 MM) Guar VAm S0 6 MM) VAm ~7 MM) Guar
028 129 37 }a 68 34
10 10 22 26 3 12.5 2
2~ lS 6 6.5 11 2 9 2
The 7 million molecular weight vinylamine homopolymer had the higher
viscosity behavior compared to the lower molecular weight homopolymer and
also outperformed the commercially available control, i.e. guar, at higher
temperature.
EXAMPLE 18
In this Example the enhanced performance of a drilling mud con-
taining a vinylamine homopolymer of the invention was demonstrated.
A typical drilling mud formulation can be prepared as follows:
Clay Dispersion A:
ll.lg *~qua Gel Gold seal Bentonite clay
8g Potassium chloride
400g Water
Clay is dispersed to hydrate overnight.
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Polymer Solution B:
2g of pol~mer are dissolved in 400g water, mixed for 2 to
4 hours and pH adjusted to 6.
Dispersion A ~200g) is added to polymer solution B ~200g) and mixed
for 4 hours. Rheology measurements were made using a FANN-35 viscometer
at 300 and 600 rpm using standard API procedure.
T A B L E 5
Apparent Plastic Gel Strength Yield Point
Polymer Viscosity tcps) Viscosity (cps) lOsec/lOmin lb/lOOft
VAm (80 M) 3.7 2.5 0 2.5
VAm (0.6 MM) 6.0 4.5 0 3.0
15 VAm (7 ~M) 14.0 11.0 3/4 6.0
Xanthan ~2 MM) 8.8 5.5 3/4 6.5
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Table 5 shows that the very high molecular weigXt vinylamine homo- -
polymer had the best performance at room temperature.
EXAMPLE l9
The high molecular weight vinylamine homopolymer demonstrated a
surprisingly hiqh viscosity in saturated brine solutions. This property
is important in completion fluids used in oil wells.
25The saturated salt solution was prepared by mixing 19 of a polymer
into lOOg of saturated salt solution and measuring the viscosity.
T A B L E 6
Viscosit~ in Saturated Salt Solution (cps)
Polymer NaCl CaC12
VAm (0.6 MM) 3 100
VAm ~7 MM) 11.5 300
*Hercules 250 HHR (2-4 MM)
Hydroxyethylcellulose 4 250
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EXAMPLE 20
This Example demonstrates the use of the vinylamine homopolymer as
a dry strength additive in paper mak;ng application.
Paper chromatography grade stoclc of uniform size was irnmersed in
water, metered through squee~e rolls and weighed. Water pick-up was
calculated and determined consistent from sheet to sheet. The weight of
polymer required per unit water volume to impart 0.5% polymsr pick-up on
sheet weight (dr,y/dry) was deterrnined.
The low molecular weight (80M) vinylamine homo~olyrner and polyvinyl
10 alcohol were applied at 0.75%. The high molecular weight ~7MM) vinyl-
amine homopol~ner which was an extremely high 3200 cps in viqcosity was
diluted to 0.1~8% solids and assumed to be 0.125~, the add-on level of
the others. The pol~ners were adjusted to pH 4.5 prior to sheet satura-
tion.
T A B L B 7
Polymer Instron Tensile Mullen Burst
Saturant lb/in lb/in2 Tear CMD
Blank 11.5 0.6 71
20 VAm (80 M) 13.5 2.5 77
VAm t7 MM)a 14.5 3.1 89
*VINOL 107 PV ~ (60 M) 12.5 2.0 80
a 0.125~ add-on compared to 0.5~ for the others.
b Polyvinyl alcohol marketed by Air Products and Chemicals, Inc.
It can be seen that the very high molecular weight vinylamine homo-
polymer was an effective dry strength additive in paperrnaking at 1/4 the
dosage compared to the low molecular weight vinylamine homopolyrner.
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3~ EXAMPLE 21
This Example shows the retention characteristics of the vinylamine
homopolymer in papermaking.
Immediately prior to hand sheet ereparations, softwood and hardwood
bleached kraft pulps were each suspended at 1.5% consistency in deionized
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water. The pulps were then blended 1:1 by weight and an amount equiv-
alent to 30g (oven dry basis) was utili~ed in preparing each set of hand
sheets. Ten percent of anatase TiO2 based on fiber weight was added
followed by 5 minutes of stirring. ~'rhe TiO2 was predispersed at 10%
solids in deionized water). Sufficient pulp to form a Z.5g hand sheet
was removed and treated with polymer followed by 30 seconds of moderate
stirring. The treated fiber suspension was then adde~ to a Noble and
Wood sheet mold containing sufficient deioni3ed water to provide a form-
; ing consistency of 0.04~. Hand sheets formed from the fiber suspensions
10 were pressed 5 minutes at 50 psig between blotter stock and then drumdried 7 minutes at 220F in contact with one blotter.
Following this procedure the polymers were added to the fiber sus-
pension at 0.5~ consistency at addition levels of 0, 0.01, 0.05, 0.1, 0.2
and 1% based on fiber. The pH was maintained at 5. Hand sheets prepared
in the manner described were conditioned at 50% RH and 73F and tested
for filler retention using TAPPI standard method.
T A B L E 8
Polymer ~ % TiOz Retention
VAm t7 MM) 93.1
VAm (80 Ml 83.3
*Hercules 834 ~ terofloc
2~ High Mol. Wt./High Charge Density, PAM t2-4 ~M) 85.6
; ~ ~ Allied Colloid *D6R 1256
Low Mol. Wt./Low Charge Density, PAN t~1 MM) 54.0
PAM = Polyacrylam~de
It can be seen that the 7MM molecular weight polytvinylamine)
demonstrated a superior TiO2 retention at 0.1-0.2% addition level to
;~ wood pulp.
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TATEMENT OF IN~USTRIAL APPLICATION
The present invention provides very high molecular weight poly(N-
vinylamides) by inverse emulsion polymerization and derived poly~vinyl-
amines) having applications in water treatment, enhanced oil recovery and
papermaking fields.
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