WO2016032844A1

WO2016032844A1 - Cationic copolymer latexes useful as additives for oil field applications

Info

Publication number: WO2016032844A1
Application number: PCT/US2015/046072
Authority: WO
Inventors: Hongwei SHEN; Disha JAIN; Kurt J. MAGNI; Joseph Manna; Wen-Shiue YOUNG
Original assignee: Dow Global Technologies Llc; Rohm And Haas Company
Priority date: 2014-08-28
Filing date: 2015-08-20
Publication date: 2016-03-03
Also published as: AR102813A1

Abstract

Oil-water dispersions and emulsions derived from petroleum industry operations are demulsified and clarified using a cationic copolymer clarifier composition. Said cationic copolymer comprises the polymerization product of (i) one or more (meth)acryl monomers, (ii) a cationic monomer, and (iii) optionally one or more (substituted)styrene monomer.

Description

CATIONIC COPOLYMER LATEXES USEFUL AS ADDITIVES FOR OIL FIELD

APPLICATIONS

FIELD OF THE INVENTION

The present invention relates to cationic copolymers, in particularly water-insoluble cationic copolymer latexes, and use thereof, for the separation of oil and water phases in emulsions and dispersions, in particular, oil field produced waste waters.

BACKGROUND OF THE INVENTION

As oil field reservoirs age and become depleted, one method to increase oil production is to maintain the pressure in the formation by injecting water or steam into the formation. The water or steam forces the oil out of the formation and to the surface. This method for sustaining oil production is referred to as secondary oil recovery. Secondary recovering is one of the most widely used recovery methods.

In secondary oil recovery, the produced fluids include the injected water emulsified with the oil. In order for the oil to be sold, it must first be separated from the water. The oil separation process is, however, not totally efficient. Some amount (200-10,000 ppm) of oil remains emulsified in the produced water. It is this waste water which is of concern. The produced water must be treated in some manner to remove and collect the residual oil before discharge.

The emulsified oil in the produced water is typically present in the range of several hundred to tens of thousands of ppm. It is critical to remove this residual oil not only from an economic standpoint of selling the oil, but also from an environmental standpoint. The United States Environmental Protection Agency has placed tight restrictions on total oil and grease (TOG) limits for water that is to be discharged into public drinking water supplies or into open bodies of water. In addition to the governmental regulations, the residual oil must be removed in order to maintain a clean source of water or steam for reinjection into the underground formation. Failure to do so would result in eventual plugging of the formation and decreased production.

Cationic polymers are used as clarifiers in oil field produced water, see

USP 5,021,167 and USP 7,470,744; as opacifiers in home and personal care compositions, see USP 8,192,504 and US Publications 2008/0216978 and 2013/0259812; and for use in waste water disposal and paper making, see USP 5,006,590. There exists a strong desire in the oil recovery industry to identify new materials for use as oil-in-water clarifiers. The water-insoluble cationic polymers of the present invention and use thereof, offer a new solution for the treatment of oil-in-water emulsions, in particular, oil field produced waste waters.

SUMMARY OF THE INVENTION

The present invention is a cationic copolymer latex comprising the polymerization product of

(i) one or more different (meth)acryl monomers described by the following structure:

wherein R is hydrogen or a methyl group,

A is an oxygen atom or NH,

R¹ is an alkylene group of 1 to 8 carbon atoms, preferably an alkylene group of 1 to

4 carbon atoms, more preferably an alkylene group of 1 or 2 carbon atoms, and

R² is hydrogen, methyl, OH, NR³R⁴, or N⁺R³R⁴R⁵X^" wherein R³, R⁴, and R⁵ are independently hydrogen or methyl, and X^" is an anionic counter ion; (ii) a cationic monomer, preferably in an amount equal to or greater than 3 weight percent, having the following structure:

wherein R' is hydrogen or a methyl group,

B is an oxygen atom or NH, preferably an oxygen atom,

R⁶ is an alkylene group of 2 to 6 carbon atoms, preferably an alkylene group having 2 or 4 carbon atoms, more preferably an alkylene group having 2 carbon atoms, and

X^" is an anionic counter ion, preferably CI^";

and

(iii) optionally one or more styrene monomer described by the following structure:

wherein R⁷ is hydrogen or a vinyl group, wherein weight percent is based on the total weight of the cationic polymer.

In one embodiment of the cationic copolymer described herein above, the one or more (meth)acryl monomer is ethyl acrylate (EA), butyl acrylate (BA), hydroxy methacrylate (HEMA), methacrylamidopropyltrimethylammonium chloride (MAPTAC), or dimethylaminoethyl methacrylate (DMAEMA); the cationic monomer is 2-(acryloxy)-N- benzyl-N,N-dimethylethanaminium chloride; and if present the styrene monomer is styrene or divinyl benzene.

In one embodiment of the present invention, the cationic copolymer latex described herein above is polymerized by an emulsion polymerization process.

In one embodiment of the present invention, the cationic copolymer latex described herein above is prepared by a polymerization process initiated using a catalyst or initiation agent.

In one embodiment of the present invention, the (meth)acryl monomer subunit is present in an amount of from 15 to 85 weight percent, the cationic monomer subunit is present in an amount of from 1 to 50, preferably 3 to 50 weight percent, and the styrene monomer subunit is present in an amount of from 0 to 90 weight percent based on the total weight of the water-insoluble cationic copolymer.

In one embodiment of the present invention, the cationic copolymer latex emulsions described herein above have a mean diameter particle size range of from 80 to 600 nm.

Another embodiment of the present invention is a method of separating oil and water in an oil- water emulsion from an oil field produced water, the method comprising the steps of treating the oil-containing water with an effective amount, preferably from 1 ppm to 10,000 ppm, of the cationic copolymer latex described herein above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph showing oil-in- water emulsions treated with water-insoluble cationic copolymer latexes of the present invention compared to an oil-in-water emulsion with no clarifier.

DETAILED DESCRIPTION OF THE INVENTION

A "polymer," as used herein and as defined by FW Billmeyer, JR. in Textbook of Polymer Science, second edition, 1971, is a relatively large molecule made up of the reaction products of smaller chemical repeat units. Polymers may have structures that are linear, branched, star shaped, looped, hyperbranched, crosslinked, or a combination thereof; polymers may have a single type of repeat unit ("homopolymers") or they may have more than one type of repeat unit ("copolymers"). Copolymers may have the various types of repeat units arranged randomly, in sequence, in blocks, in other arrangements, or in any mixture or combination thereof. Chemicals that react with each other to form the repeat units of a polymer are known herein as "monomers," and a polymer is said herein to be made of, or comprise, "polymerized units" of the monomers that reacted to form the repeat units. The chemical reaction or reactions in which monomers react to become polymerized units of a polymer, whether a homopolymer or any type of copolymer, are known herein as "polymerizing" or "polymerization."

A copolymer comprises two or more monomers, for example it may comprise two, three, four, five, six, or more monomers. However, if a copolymer is described as

"consisting of two monomers (for example monomers A and B), the copolymer is made up of only the two monomers (i.e., A and B). In other words, the phrase "a copolymer consisting of the polymerization product of monomers A and B" means that the copolymer is made up of only the monomeric subunits of A and B.

Alternatively, if a copolymer is described as consisting of three monomers selected from monomers A, B, C, D, E, and F, the copolymer is made up of any selection of only three monomers from the group of A, B, C, D, E, and F, for example A, B, and C; or A, C, and D; or A, C, and E; etc.

In all of the compositions herein the weight percentages will always total 100 percent. Thus, the percentages stated hereinbelow to describe the proportions of the various monomeric components in the polymer are all based on the total weight of the polymer, with the total being 100 percent.

As used herein, the prefix "(meth)acryl" means "methacryl or acryl", for example (meth)acrylate means methacrylate or acrylate or (meth)acrylamide means methacrylamide or acrylamide.

As used herein, the prefix "(meth)acrylate" means "methacrylate or acrylate."

The term "petroleum industry operations," as used herein, includes, but not is limited to, activities and processes for exploration, production, refining and chemical processing of hydrocarbons including, but not limited to, crude oil, gas and their derivatives. For example, exploration often involves the initial drilling of wells wherein drilling fluid, or drilling mud, which is typically a mixture of liquid and gaseous fluids and solids, is used as lubricant and heat sink. Suitable dispersants are helpful to stabilize such mud to a homogenous composition. Production operations include, but are not limited to, pumping large quantities of water into the ground, as described above, which commensurately generates large quantities of "formation water," an oil-in- water dispersion or emulsion. Breaking of such emulsions with additives to remove and recover oil from the produced water is a common and beneficial practice. Oil refining processes, for example, include but are not limited to, the removal of inorganic solids and salts (referred to as "desalting") from produced oil. Desalting operations produce oil in water mixtures which require clarification and/or demulsifying prior to discharge or reuse. Lastly, chemical processing in the petroleum industry includes many various activities such as, for example, without limitation, production of ethylene by fractionation which involves water quench operations. The quench operations of ethylene manufacturing generate quench waters containing heavy, middle and light hydrocarbons and, therefore, require demulsifying and/or clarification. Persons of ordinary skill in the art will readily recognize the many various operations performed in the petroleum industry to which the present invention is reasonably applicable and the invention is intended to include all such applications.

The term "oil-water emulsion," as used herein, includes dispersions even where a stable emulsion does not exist and also includes water-in-oil emulsions and oil-in-water emulsions, as well as multiple emulsions, such as water-in-oil-in-water. Oil is the continuous, or external, phase in water-in-oil emulsions. For oil-in-water emulsions, the continuous, or external, phase is water.

Endpoints of ranges are considered to be definite and are recognized to incorporate within their tolerance other values within the knowledge of persons of ordinary skill in the art, including, but not limited to, those which are insignificantly different from the respective endpoint as related to this invention (in other words, endpoints are to be construed to incorporate values "about" or "close" or "near" to each respective endpoint). The range and ratio limits, recited herein, are combinable. For example, if ranges of 1-20 and 5-15 are recited for a particular parameter, it is understood that ranges of 1-5, 1-15, 5- 20, or 15-20 are also contemplated and encompassed thereby.

The present invention provides a water-insoluble cationic copolymer latex water clarifying composition and a method for use thereof to separate oil and water phases of an oil-water dispersion or emulsion derived from petroleum industry operations. The clarifying composition of the present invention is a copolymer latex comprising the polymerization product of one or more (meth)acryl monomer, a cationic monomer, and optionally one or more of a styrene monomer.

Suitable (meth)acryl monomers have the following structure:

wherein R is hydrogen or a methyl group,

A is an oxygen atom or NH, preferably an oxygen atom,

4 carbon atoms, more preferably an alkylene group of 1 or 2 carbon atoms, and

R² is hydrogen, methyl, OH, NR³R⁴, or N⁺R³R⁴R⁵X^" wherein R³, R⁴, and R⁵ are independently hydrogen or methyl, and X^" is an anionic counter ion.

Suitable cationic monomers have the following structure:

wherein R' is hydrogen or a methyl group,

B is an oxygen atom or NH, preferably an oxygen atom,

R⁶ is an alkylene group of 2 to 6 carbon atoms, preferably an alkylene group having 2 to 4 carbon atoms, more preferably an alkylene group having 2 carbon atoms, and

X^" is an anionic counter ion, preferably CI^".

The water-insoluble cationic polymer of the present invention may further comprise more of a styrene monomer subunit. Suitable styrene monomers have the structure:

wherein R⁷ is hydrogen or a vinyl group.

Preferably the (meth)acryl monomer is ethyl acrylate (EA), butyl acrylate (BA), hydroxy methacrylate (HEM A), methacrylamidopropyltrimethylammonium chloride (MAPTAC), or dimethylaminoethyl methacrylate (DMAEMA).

Preferably the cationic monomer is 2-(acryloxy)-N-benzyl-N,N- dimethylethanaminium chloride.

Preferably the styrene monomer is styrene or divinyl benzene.

In one embodiment, the water-insoluble cationic copolymer of the present invention comprises one or more additional monomer (i.e., a monomer that is neither a (meth)acryl monomer, cationic monomer, nor a styrene monomer). The total amount of all additional monomer or monomers present as polymerized units in a cationic polymer, by weight based on the dry weight of that cationic copolymer. Some suitable additional monomers include, for example, anionic monomers, lower-alkyl(meth)acrylate esters, higher- aliphatic(meth)acrylate esters, HE/A monomers (as defined herein above), crosslinking monomers, substituted or unsubstituted amides of (meth)acrylic acid, other monomers capable of copolymerizing with cationic monomer and aromatic monomer, and mixtures thereof.

Crosslinking monomers are compounds that are capable of copolymerizing with the

(meth)acryl monomer, cationic monomer, and optional styrene monomer and are capable of forming crosslinks in the water-insoluble cationic copolymer of the present invention. Among embodiments in which crosslinking monomer is used, some suitable crosslinking monomers, for example, are multi-ethylenically unsaturated compounds (i.e., compounds with more than one carbon-carbon double bond). Some suitable crosslinking monomers are, for example, divinyl benzene, diallyl phthalate, and esters of (meth)acrylic acid with a polyol (i.e., a compound with two or more hydroxyl groups, i.e., ethylene glycol dimethacrylate).

If a crosslinking monomer is present it is present in an amount of from 0.05 to 2 weight percent by weight of the water-insoluble cationic copolymer.

Another class of additives useful with the invention is chain transfer agents. Chain transfer agents may be useful in some embodiments for controlling molecular weight growth. Optional chain transfer agents include mercaptans such as alkyl and/or aryl alkyl mercaptans. Examples of specific chain transfer agents include n-octyl mercaptan, n- dodecyl mercaptan, t-octyl mercaptan, t-dodecyl mercaptan, tridecyl mercaptan, tetradecyl mercaptan, hexadecyl mercaptan and the like, as well as mixtures thereof.

If a chain transfer agent is present it is present in an amount of from 0.05 to 2 weight percent by weight of the water-insoluble cationic copolymer.

The comonomers are polymerized in water under conditions sufficient to prepare a copolymer, but copolymers of this invention can be prepared by emulsion polymerization. Methods used to synthesize copolymers include, but are not limited to: emulsion polymerization, microemulsion polymerization, or miniemulsion polymerization.

The comonomers are polymerized in water under conditions sufficient to prepare a copolymer, but copolymers of this invention can be prepared with any technique that is known to one of ordinary skill in the art of preparing polymers and copolymers. Methods used to synthesize copolymers include, but are not limited to: emulsion polymerization, microemulsion polymerization, miniemulsion polymerization, inverse emulsion

polymerization, precipitation polymerization, dispersion polymerization, and suspension polymerization. The preferred process is emulsion polymerization.

In a preferred embodiment of the present invention, the one or more acryl monomers, the cationic monomer, and the optional styrene monomer are used to form a latex such as that described in US 8,192,504, the entirety of which is incorporated by reference herein.

In the preparation of aqueous copolymers by emulsion polymerization, distinctions are generally made between batch, semibatch, and continuous processes, and different methods of adding the monomers to the reaction vessel are described. For example, in a semibatch process the monomer mixture or emulsion is prepared in a separate batching vessel and the mixture or emulsion is passed continuously into a polymerization reactor, where it is polymerized. According to a general procedure for a semibatch process, the feed stream may comprise all of the ingredients used, such as monomers, water, and additives, with the aqueous monomer mixture or emulsion being prepared in a separate batching vessel, referred to as the feed tank.

In other embodiments of the invention, the copolymer is prepared by a continuous process or a batch process. In a continuous process, the monomers are admixed and fed continuously into the reactor, while in a batch process, the monomers are admixed and reacted without the further addition of monomer. Any method of polymerization may be used with the present invention.

The copolymer may be prepared using a catalyst or, in the alternative, the copolymer may be prepared using thermal energy to initiate polymerization. Any method of catalyzing and/or initiating polymerization of an aqueous dispersion of monomers having one or more polymerizable double bonds may be used with the present invention. For example, the monomers may be heated to from about 30°C to about 95 °C to initiate polymerization, or may be conducted at room temperature with the proper initiating system.

When the copolymer is prepared using a catalyst, in one embodiment a free-radical catalyst is used. Suitable free-radical polymerization initiators include all those which are capable of setting off a free-radical polymerization. They may comprise either peroxides, e.g., alkali metal peroxodisulfates or organic peroxides, or azo compounds. Use may also be made of combined systems which are composed of at least one organic or inorganic reductant and at least one peroxide and/or hydroperoxide, an example being tert-butyl hydroperoxide with the sodium salt of hydroxymethanesulfonic acid or hydrogen peroxide with ascorbic acid.

Combined catalyst systems may be used which include a small amount of a metal compound which is soluble in the polymerization medium and whose metallic component is able to exist in a plurality of valence states, e.g., ascorbic acid/iron(II) sulfate/hydrogen peroxide, in which in many cases the ascorbic acid may be replaced by the sodium salt of hydroxymethanesulfonic acid, sodium sulfite, sodium hydrogen sulfite or sodium bisulfite and the hydrogen peroxide by tert-butyl hydroperoxide or alkali peroxodisulfates and/or ammonium peroxodisulfate. Preferred initiators are the ammonium or alkali metal salts of peroxosulfates or peroxodisulfates, especially sodium or potassium peroxodisulfate, and V- 50 (2,2'-azobis(2-methylpropionamidine) dihydrochloride), an azo initiator.

Exemplary protective colloids include polyvinyl alcohols, cellulose derivatives, or copolymers based on vinylpyrrolidone. Suitable emulsifiers are, in particular, anionic and nonionic emulsifiers, such as ethoxylated mono-, di- and trialkylphenols, ethoxylates of long chain alkanols, alkali metal salts and ammonium salts of alkyl sulfates, of sulfuric monoesters with ethoxylated alkanols and ethoxylated alkylphenols, of alkylsulfonic acids and of alkylarylsulfonic acids.

Nonionic emulsifiers which can be used include arylaliphatic or aliphatic nonionic emulsifiers, examples being ethoxylated mono-, di- and trialkylphenols (degree of ethoxylation: from 3 to 50, alkyl radical: C4-C1₀), ethoxylates of long-chain alcohols (degree of ethoxylation: from 3 to 50, alkyl radical: C8-C36), and also polyethylene

oxide/polypropylene oxide block copolymers.

Suitable cationic emulsifiers for use with the present invention include quaternary ammonium halides, e.g., trimethylcetylammonium chloride, methyltrioctylammonium chloride, benzyltriethylammonium chloride, or quaternary compounds of N— (C₆- C2o)alkyl)pyridines, N-(C6-C₂o)alkyl morpholines or N-(C6-C₂o)alkyl imidazoles, e.g., N- laurylpyridinium chloride.

The copolymers of the invention may also be prepared in other solvents and/or mixture of solvents besides water. Any solvent known to be useful to those of ordinary skill in the art of preparing polymer and copolymers may be used. Examples of such solvents include organic solvents, but are not limited to: polyvinylpyrrolidone, N-methyl-2- pyrrolidinone (also called N-methyl-2-pyrrolidone), 2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, lactic acid, methanol, ethanol, tetrahydrofuran, isopropanol, 3-pentanol, n-propanol, glycerol, butylene glycol (butanediol), ethylene glycol, propylene glycol, mono- and diacylated monoglycerides (such as glyceryl caprylate), dimethyl isosorbide, acetone, dimethylformamide, 1,4-dioxane, polyethylene glycol (for example, PEG4, PEG-8, PEG-9, PEG-12, PEG-14, PEG-16, PEG-120, PEG-75, PEG-150) polyethylene glycol esters (examples such as PEG4 dilaurate, PEG- 20 dilaurate, PEG-6 isostearate, PEG-8

palmitostearate, PEG-150 palmitostearate), polyethylene glycol sorbitans (such as PEG-20 sorbitan isostearate), polyethylene glycol monoalkyl ethers (examples such as PEG-3 dimethyl ether, PEG4 dimethyl ether), polypropylene glycol (PPG), polypropylene alginate, PPG-10 butanediol, PPG-10 methyl glucose ether, PPG-20 methyl glucose ether, PPG-15 stearyl ether, propylene glycol dicaprylate/dicaprate, propylene glycol laurate. Other solvents include saturated aliphatic hydrocarbons such as butane, pentane, hexane and heptane; saturated cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; monoolefins such as 1-butene and 2-butene; aromatic hydrocarbons such as benzene and toluene; halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, trichloroethylene, perchloroethylene, 1,2-dichloroethane, chlorobenzene, bromobenzene and chlorotoluene.

In the copolymers of the present invention each acryl monomer subunit (i) can comprise from 1 percent to 90 percent by weight of the copolymer, preferably from 5 percent to 90 percent, more preferably from 10 percent to 85 percent, more preferably from 15 percent to 85 percent by weight of the copolymer.

In the copolymers of the present invention the cationic monomer subunit (ii) can comprise from 1 percent to 50 percent by weight of the copolymer, preferably from 3 percent to 40 percent, more preferably from 3 percent to 30 percent, more preferably from 3 percent to 20 percent by weight of the copolymer.

In the copolymers of the present invention if the styrene monomer subunit (iii) is present, it can comprise from 1 percent to 85 percent by weight of the copolymer, preferably from 1 percent to 60 percent, more preferably from 1 percent to 30 percent by weight of the copolymer.

The composition of the present invention comprises one or more water-insoluble cationic copolymer that is in the form of a latex emulsion. A latex is a collection of (co)polymer particles that form a stable dispersion in an aqueous medium. The water- insoluble cationic copolymer latex emulsions of the present invention have a solids content in weight percent of from 5 to 70 weight percent, preferably of from 10 to 60 weight percent, more preferably of from 20 to 40 weight percent.

The particles in a latex can usefully be characterized by the mean diameter of the particles, which can be determined by well known methods, for example light scattering. In some embodiments, the water-insoluble cationic copolymer latexes of the present invention have a mean diameter particle size of from 80 to 600 nm.

The copolymer latexes of the present invention are particularly useful in production fluid demulsification and water clarification and flocculation. For the purposes of this invention, a production fluid is the often multiphase admixture of hydrocarbons, water, soluble inorganic materials and particulate matter produced from an oil and gas well. The copolymers of the present invention may be used, optionally in combination with other additives, to treat production fluid downhole, at the surface in a separator, or even downstream from the production well to facilitate the separation of the hydrocarbon from the water in the production fluid to produce a hydrocarbon phase that can be efficiently and cost effectively transferred and refined. In another embodiment, the copolymers of the present invention may be used down hole in conjunction with, for example, a descaler, to penetrate and break emulsions in the producing formation to facilitate the flow of hydrocarbons into an oil well bore. The copolymers of the present invention may be used in any way known to those of ordinary skill in the art of producing oil and gas to be useful.

An effective amount of the copolymer of the present invention useful for clarification of emulsified oil from an oil field produced water is from 1 to 10,000 ppm and preferably from 5 to 500 ppm, more preferably from 5 to 200 ppm.

In clarification applications, the copolymers of the present invention may be used to clarify process or waste water. In one embodiment, the copolymers of the present invention are admixed with waste water to produce a floe which can then be separated from the water using a separator device. In another embodiment, the copolymers of the present invention may be added to process water to reduce turbidity. The copolymers of the present invention maybe used in any way known to those of ordinary skill in the art of treating process and waste water to be useful.

The copolymers of the present invention are used in the form of a copolymer solution, preferably a copolymer latex emulsion.

A preferred embodiment of the present invention is a method of separating oil and water in an oil- water emulsion from an oil field produced water, the method comprising the steps of treating the oil-containing water with an effective amount of a water-insoluble cationic copolymer of the present invention.

EXAMPLES

A description of the raw materials used in the Examples is as follows, all chemicals are available from Sigma Aldrich unless otherwise noted.

TERGITOL 15-S-40 is a 70 weight percent aqueous solution of

polyethylene glycol (41) trimethylnonyl ether available from the Dow Chemical Company,

EG is ethylene glycol,

STY is styrene,

EA is ethyl acrylate, BA is butyl acrylate,

EDTA is ethylenediaminetetraacetic acid,

DMAEMA is dimethylaminoethyl methacrylate,

IAA is D-isoascorbic acid IAA,

t-BHP is tert-butyl hydroxyl peroxide

t-AHP is tert-amyl hydroxyl peroxide,

CTAC is cetyl trimethyl ammonium chloride,

VAZO™ 56 is 2,2'-azobis(2-methylpropionamidine)

dihydrochloride a free radical initiator available from

DuPont, and

AD AMQU AT BZ80 (BZ80) is 80 weight percent 2-(acryloxy)-N-benzyl-N,N- dimethylethanaminium chloride available from Whyte Chemicals Limited. Example 1

To a 1 liter, 4 neck, round bottom flask equipped with overhead stirring, thermocouple and controller, water cooled condenser and under nitrogen ( N₂) blanket is filled with a kettle charge of 100 grams (g) of di-ionized water (DIH₂0), 6 g BZ80 and 3 g EA and heated to 70°C +/- 1°C with stirring. A monomer mixture is prepared by adding 10 g of EA and then 15 g of BA in a 500mL glass jar equipped with a magnetic stir bar placed on a magnetically driven stirring plate. At reaction temperature of 70°C, a solution of 0.1 g VAZO 56 in 10 g DIH₂0 is added into reactor and the reactor is held at 70°C for 15 min. Then, the prepared monomer mixture and a solution of 0.2 g t-AHP in 20 g DIH₂0 are gradually fed into reactor separately over 65 min. After holding for 30 min at the end of the feed, 1 g of a 0.1 weight percent EDTA and 1 g of a 0.1 weight percent ferrous sulfate are added. A solution of 0.5 g t-AHP in 10 g DIH₂0 and a solution of 0.35 g IAA in 10 g DIH₂0 are gradually added over 60 min in separate feed lines. The emulsion polymer is then cooled to room temperature before taking out of the reactor for analysis and performance tests.

Example 2

Using the same setup and process in Example 3, the kettle charge includes 293.6 g DIH₂0, 0.94 sodium carbonate, 1.7 g TERGITOL 15-S-40, and 30.2 g DMAEMA. The reactor is heated to 75°C with stirring. A monomer emulsion (ME) is prepared by adding the following slowly in the order of 104.8 g DIH₂0, 11.3g TERGITOL 15-S-40, 30.2 g BA, 40.3 g of STY, and 100.6 g EA in the glass jar with stirring to form a stable emulsion. At the set temperature of 75°C, 29 g of prepared ME is charged into reactor at once. A solution of 0.51 g VAZO 56 in 11.1 g DIH₂0 is added into reactor and the reactor is held at temperature for 10 min. During this hold, 10.1 g BZ80 and 60.4 g DMAEMA are added into the remainder of the ME with stirring. The resulting ME is gradually fed into the reactor over 120 min. Simultaneously, a solution of 0.65 g VAZO 56 in 33.8 g DIH₂0 is co-fed into reactor separately over 140 min. The temperature is held at 75°C. After holding for 20 min at the end of the ME feed, 3.7 g of a 0.15 weight percent ferrous sulfate aqueous solution is added. A solution of 1.5 g t-BHP in 13.1 g DIH₂0 and a solution of 0.9 g IAA in 13.1 g DIH₂0 are gradually added over 60 min in separate feed lines. The emulsion polymer is cooled to room temperature before taking out of the reactor for analysis and performance tests.

Example 3

Using the same setup and process in Example 2, the kettle charge includes 291.6 g

DIH₂0, 1.7 g TERGITOL 15-S-40, and 5.1 g BZ80. The reactor is heated to 80°C with stirring. A monomer emulsion (ME) is prepared by adding the following slowly in the order of 106.1 g DIH₂0, 11.4 g TERGITOL 15-S-40, 30.6 g BA, 40.8 g of STY, and 101.9 g EA in the glass jar with stirring to form a stable emulsion. At a reaction temperature of 80°C, 29.4 g of prepared ME is charged into reactor at once. A solution of 0.51 g VAZO 56 in 11.3 g DIH₂0 is added into reactor and the reactor is held at temperature for 20 min and then sets to 83°C. During this hold, 12.7 g BZ80 is added into the remainder of the ME with stirring. The resulting ME is gradually fed into the reactor over 120 min.

Simultaneously, a solution of 0.66 g VAZO 56 in 34.3 g DIH₂0 is co-fed into reactor separately over 140 min. After holding for 20 min at the end of the ME feed, 3.8 g of a 0.15 weight percent ferrous sulfate aqueous solution is added. A solution of 1.5 g t-BHP in 13.3 g DIH₂0 and a solution of 0.9 g IAA in 13.3 g DIH₂0 are gradually added over 60 min in separate feed lines. The reactor is held at 83°C for additional 20 min after the end of the two-solution feed. The emulsion polymer is then cooled to room temperature before taking out of the reactor for analysis and performance tests.

Example 4

A 500 mL, 4 neck, round bottom flask equipped with overhead stirring,

thermocouple and controller, water cooled condenser and under N₂ blanket is filled with 145.3 g DIH₂0, 50.3 g of the product in Example 4 and 6 g benzyl chloride. The reactor is heated to 80°C +/- 1°C with stirring. At the set temperature, the reactor is held for 5 hours before cooling down to room temperature for taking the emulsion polymer out of the reactor for analysis and performance tests.

Compositions for Examples 1 to 4 are summarized in Table 1.

Table 1

Latex Characterization

Latex particle size (diameter) is determined using Malvern's zeta-sizer ZS equipped with a standard 633 nm laser and analyzed at 90° scattering angle. A drop of a latex polymer is added in a 12 mm square polystyrene cuvette and then diluted with de-ionized water to become a translucent dispersion. Once placing the cuvette with the latex polymer into the zeta-sizer ZS, the particle size in diameter is analyzed by Malvern's particle sizing software automatically using the dynamic light scattering principle. The reported latex diameter in Table 2 is the average of three repeat measurements on each emulsion polymer.

Solid weight percentage or solid content for each emulsion polymer is measured using Mettler Toledo HR83 moisture analyzer. The analyzer with a fresh piece of filter paper inside an aluminum pan is tarred before about 1 gram of latex polymer is placed on the filter paper. Then, the latex polymer is weighted. The analyzer is heated and held at 105°C. In 10 to 20 min, the percentage of solid or solid content in the latex polymer is reported from the instrument once the measured weight from the instrument is stabilized. All the solid contents are also reported in Table 2. Table 2

Examples are tested for their clarification ability to resolve oil-in- water emulsions in 3 different test conditions in either synthetic produced water or fresh produced water. The results are summarized in Table 3.

Method 1

A synthetic produced oil-in- water emulsion is prepared by adding 250 μΕ of 2 weight percent aqueous NaOH solution to 650 mL of DI water and then mixing in 6.5 mL of mid-gravity Middle Eastern crude oil for about 10 seconds under high shear (12,000 rpm). Continue the agitation of the synthetic produced oil-in-water emulsion for a further 2 minutes under high shear of 12,000 rpm. The resultant synthetic produced oil-in-water emulsion has a pH of about 8.5. 100 ml of these emulsions are added quickly to 6 ounce clear glass bottles and inverted several times to coat the bottles with emulsified oils. The resultant emulsion is dosed with a cationic copolymer to a final dosage of 50 ppm. A bottle without any treated chemical is chosen as the blank. The bottles are agitated 50 times by hand. Observations such as water clarity is depicted as either positive or negative, where positive in water clarity ratings indicates that emulsions are clear to near clear (i.e., Ex. 2 and Ex. 4) and negative in water clarity ratings refers that the emulsions are not cleared, (i.e., the blank), see FIG. 1.

Method 2

For each test, a 6 ounce clear glass bottle is filled with 100 mL fresh produced water (field 1) and inverted several times to coat the bottles with emulsified oils. The resultant emulsion is dosed with a cationic copolymer to a final dosage of 50 ppm. A bottle without any treated chemical is chosen as the blank. The bottles are agitated 100 times by hand. Observations such as water clarity are depicted as either positive or negative, as those defined in Method 1. Method 3

For each test, a 6 ounce clear glass bottle is filled with 100 mL fresh produced water (field 2) kept at 146 F and inverted several times to coat the bottles with emulsified oils. The resultant emulsion is dosed with a cationic copolymer to a final dosage of 300 ppm. A bottle without any treated chemical is chosen as the blank. The bottles are agitated 200 times by hand. Observations such as water clarity are depicted as either positive or negative, as those defined in Method 1.

Table 3

FIG. 1 shows the results for Example 2, Example 4, and the blank following treatment according to Method 2.

Claims

claimed is:

A cationic copolymer latex comprising the polymerization product of i one or more different (meth)acryl monomers described by the following structure:

wherein R is hydrogen or a methyl group,

A is an oxygen atom or NH,

R¹ is an alkylene group of 1 to 8 carbon atoms,

and

R² is hydrogen, methyl, OH, NR³R⁴, or N⁺R³R⁴R⁵X^" wherein R³, R⁴, and R⁵ are independently hydrogen or methyl, and X^" is an anionic counter ion. ii a cationic monomer in an amount of 3 weight percent or greater having the following structure:

wherein R' is hydrogen or a methyl group,

B is an oxygen atom or NH,

R⁶ is an alkylene group of 2 to 6 carbon atoms,

and

X^" is an anionic counter ion. iii optionally one or more styrene monomer described by the following structure:

wherein R⁷ is hydrogen or a vinyl group,

wherein weight percent is based on the total weight of the cationic copolymer.

2. The cationic copolymer latex of Claim 1 wherein the one or more (meth)acryl monomer is ethyl acrylate (EA), butyl acrylate (BA), hydroxy methacrylate (HEMA), methacrylamidopropyltrimethylammonium chloride (MAPTAC), or dimethylaminoethyl methacrylate (DMAEMA); the cationic monomer is 2-(acryloxy)-N-benzyl-N,N- dimethylethanaminium chloride; and if present the styrene monomer is styrene or divinyl benzene.

3. The cationic copolymer latex of Claim 1 wherein the polymerization conditions comprise an emulsion polymerization process.

4. The cationic copolymer latex of Claim 1 wherein the copolymer is prepared by a polymerization process initiated using a catalyst or initiation agent.

5. The cationic copolymer latex of Claim 1 wherein the (meth)acryl monomer subunit is present in an amount of from 15 to 85 weight percent, the cationic monomer subunit is present in an amount of from 3 to 50 weight percent, and the styrene monomer subunit is present in an amount of from 0 to 90 weight percent based on the total weight of the cationic copolymer..

6. The cationic copolymer latex of Claim 1 wherein the copolymer has a mean diameter particle size of from 80 to 600 nm.

7. A method of separating oil and water in an oil-water emulsion from an oil field produced water, the method comprising the steps of treating the oil-containing water with an effective amount of a cationic copolymer latex comprising of the polymerization product of i one or more different (meth)acryl monomers described by the following structure:

wherein R is hydrogen or a methyl group,

A is an oxygen atom or NH,

R¹ is an alkylene group of 1 to 8 carbon atoms,

and

R² is hydrogen, methyl, OH, NR³R⁴, or N⁺R³R⁴R⁵X^" wherein R³, R⁴, and R⁵ are independently hydrogen or methyl, and X^" is an anionic counter ion. a cationic monomer having the following structure:

wherein R' is hydrogen or a methyl group,

B is an oxygen atom or NH,

R⁶ is an alkylene group of 2 to 6 carbon atoms,

and

X^" is an anionic counter ion.

and

iii optionally one or more styrene monomer described by the following structure:

wherein R⁷ is hydrogen or a vinyl group.

8. The process of Claim 7 wherein the one or more (meth)acryl monomer is ethyl acrylate (EA), butyl acrylate (BA), hydroxy methacrylate (HEM A),

methacrylamidopropyltrimethylammonium chloride (MAPTAC), or dimethylaminoethyl methacrylate (DMAEMA); the cationic monomer is 2-(acryloxy)-N-benzyl-N,N- dimethylethanaminium chloride; and if present the styrene monomer is styrene or divinyl benzene.

9. The process of Claim 7 wherein the cationic copolymer latex is used in an amount of from 1 ppm to 10,000 ppm.