Water soluble graft copolymers of lignin and methods of making the same

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FIELD OF THE INVENTION

The present invention relates to water-soluble graft copolymers of lignin-(2-propenamide)-(2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct- 1-ene chloride or methylsulfate), methods of making the same and uses therefor.

BACKGROUND OF THE INVENTION

Aqueous solutions which flow at a controlled rate under a given shear stress are required throughout a variety of industrial applications. Such control of viscosity of water is achieved by adding to the water agents such as clays, large amounts of polar organic compounds such as polyacrylates or high concentrations of salts. These aqueous solutions suspend finely divided solids and will flow slowly when exposed to shear stress. Such solutions also flow more uniformly in situations where numerous paths, providing different resistances to flow, are open to the fluids.

However, each of these conventional agents has attendant disadvantages particularly when used to recover oil from subterranean wells. The application of these agents to flow control and flocculation-deflocculation control requires careful adjustment of the concentration of an active agent in the solution and control of adsorption of the active agent onto suspended solids or the matrix of the porous media. Such control is impossible when negatively charged agents are introduced into systems containing positively-charged surfaces such as calcite. The negatively-charged agents are completely adsorbed onto the solid. Further, if the solution contains divalent cations, the negatively-charged agents associate with the cations and precipitate. Hence, a need continues to exist for new agents which are capable of suitably thickening water and aqueous solutions to produce aqueous solutions having the desirable properties as outlined below but which are free of attendant disadvantages in the prior art agents.

SUMMARY OF THE INVENTION

A water-soluble graft copolymer of lignin-(2-propenamide)-(2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct- 1-ene chloride or methylsulfate) having a central lignin network and at least one grafted side chain, R, having randomly repeating units of the formulas: ##STR2## such that the central lignin network has a molecular weight of about 1,000 to 150,000 and the total number of random units in the grafted side chain or chains is in the range of 50 to 300,000 units, such that the total copolymer molecular weight is in the range of 15,000 to 30,000,000. The resulting molecule bears multiple positive charges.

Objects, features and advantages of the present invention are to provide a positively-charged lignin graft copolymer; provide simplistic and reliable processes for preparing such lignin graft copolymer; provide a method for using a positively-charged lignin graft copolymer in preparing highly viscous, aqueous solutions which are particularly useful in oil recovery from subterranean wells into carbonate reservoirs; and to provide a method of boosting or enhancing polymer molecular weights during polymerization reactions.

DETAILED DESCRIPTION

In accordance with the present invention, there is provided a high molecular weight graft copolymer containing lignin as the backbone network and poly((1-amidoethylene)-co-(1-methyl-1-(N5,N5-dimethyl-5-ammonium-1-oxo-2-o xyhexyl) ethylene)) with appropriate counter ion as the grafted side chain.

Lignin [8068-00-6] is derived from woody plants. In fact, after cellulose, it is the principal constituent of the woody structure of higher plants. Lignin, which makes up about 25% of the weight of dry wood, acts as a cementing agent to bind the matrix of cellulose fibers together into a rigid woody structure. See Biochemistry by A. L. Lehninger (Worth Publishers, 1970).

Moreover, lignin sources are abundant. Although the wood and bark waste from the lumber industry and wastes from agricultural operations could provide extremely large quantities of lignin, perhaps the most accessible, albeit smaller, source is the pulp and paper industry. For example, for 1978, it has been estimated that the U.S. chemical-pulp industry produced 1.55.times.10.sup.7 metric tons of alkali lignin and 1.6.times.10.sup.6 tons of lignosulfonic acids. See Encyclopedia of Chemical Technology, vol. 14 (Kirk-Othmer, 1981).

In general, the molecular structure of the repeating lignin units and the appropriate numbering thereof is as follows: ##STR3##

It appears that, regardless of origin, lignin [8068-00-6] is a complex, oxyphenylpropene polymer. In the natural state, lignin is a highly branched and partially cross-linked polymer. However, there appears to be some structural variation in branching depending upon whether the lignin is derived from coniferous or deciduous species or from bark, cambium, sapwood or heartwood. During recovery, the lignin is chemically altered and is available in relatively pure form as a derivative having a molecular weight of about 1,000 to 150,000. Suitable lignins which may be used according to the present invention are alkali lignins, HCl lignins, milled wood lignins (MWL) and 1,4-dioxane lignins, for example.

Alkali lignins are used in the examples of this application. However, reactions can be run on solvent-extracted lignin, kraft lignin, pine lignin, aspen lignin and steam-exploded lignin. Alkali lignins are tan, brown or black powders. When free of metal cations such as sodium or potassium, alkali lignins are water-insoluble materials and are commonly called "free acid" or "acid free" lignin. When containing metal cations, such as sodium or potassium, the alkali lignins are slightly water soluble materials which increase in water solubility as the pH increases from 7 toward 14 and become completely soluble in 5 wt. % aqueous sodium hydroxide solutions. Alkali lignins have, as a basic repeating unit, the oxyphenylpropyl unit: ##STR4##

The aromatic ring is often alkoxy substituted, as shown, and the propene group often has a hydroxyl group attached in place of one hydrogen. Alkyl groups appear on some of the aromatic groups of the polymer and sulfur may be chemically bound to parts of the polymer, though few, if any, sulfonate groups occur.

Bonding between repeat units in alkali lignin is complex and involves carbon-carbon bonds between aromatic and/or alkyl carbons as well as ether bonds between aromatic and/or alkyl carbons. Labile hydrogens exist in the material and may be replaced by metal cations, such as sodium, potassium, calcium, or ammonium ions, to form alkali lignin salts. Alkali lignins are readily identified by method of production and are a familiar class of compounds to those versed in the paper making art.

In accordance with the present invention, to the lignin macromolecule, specifically to the oxyphenylpropene repeat unit, is grafted repeating units of 1-amidoethylene: ##STR5## in combination with positively-charged repeating units of (1-methyl-1-(N5,N5,-dimethyl-5-ammonium-1-oxo-2-oxyhexyl) ethylene): ##STR6##

For example, when using alkali lignins in accordance with the present invention, a lignin graft copolymer of the following formula is produced: ##STR7##

In this structural formula, the subscripts m and n are used to show that large numbers of the repeating units can be attached to the lignin backbone but the formula does not mean that these repeat units occur in strings of one type followed by strings of another type. Usually, the graft copolymers formed have random copolymer side chains with the two repeat units occurring in random sequence in the chain.

The preparation of this copolymer is accomplished, in general, under oxygen-free conditions by adding a redox initiator, a chloride salt, 2-propenamide, and 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene chloride or methylsulfate, ##STR8## to a lignin dispersion in a suitable solvent and allowing time for graft polymerization to occur.

Preparation of alkali lignin-(2-propenamide)-(2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct- 1-ene chloride or methylsulfate) graft copolymer in dimethylsulfoxide will now be illustrated for a sample composed of between 0.32 and 3.0 weight percent lignin, 1.2 and 7.6 weight percent 2-propenamide, 0.1 to 11.0 weight percent 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene (chloride or methylsulfate), 0.6 to 15.3 weight percent calcium chloride, 0.0 to 6.1 weight percent aqueous solution of cerium (+IV), and 60 to 97 weight percent solvent.

Significant variation in reaction mixture composition is possible as will be illustrated in the examples to follow. The synthesis method for these copolymers will now be described, generally.

As a suitable solvent for the graft copolymerization of the present invention, it should be noted that, in general, organic solvents are used and, of these, the polar, aprotic solvents are preferred. Particularly noteworthy are the solvents dimethyl sulfoxide (DMSO), dimethyl acetamide (DMAc), dimethyl formamide (DMF), 1,4-dioxane, 1-methyl-2-pyrrolidianone and pyridine. Of course, mixtures of these solvents can also be used such as 50/50 (vol/vol) mixtures of DMSO and 1,4-dioxane However, it is also possible to use various mixtures of the above solvents, such as a 50/50 (vol/vol) mixture of DMSO with water.

An aliquot of about 20 mL of purified solvent is placed in a 125 mL conical flask or stopperable test tube. Lignin and finely ground anhydrous calcium chloride are added to the pure solvent and the mixture is stirred for about 20 minutes while being bubbled with nitrogen. After 10 minutes of nitrogen saturation, a hydroperoxide such as hydrogen peroxide or 2-hydroperoxy-1,4-dioxycyclohexane is added to the reaction mixture. This addition can be made by adding an aqueous solution of the peroxide for safe handling or the peroxide can be added directly. Solid 2-propenamide and a nitrogen-saturated solution of 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene chloride or methylsulfate in solvent are added while nitrogen gas is bubbled into the mixture. After about 10 minutes, a sufficient volume of 0.05M ceric sulfate in water may be added, the flask is sealed under nitrogen, and the slurry is stirred for 10 more minutes. The reaction starts immediately. The flask contents will often thicken slowly but may even solidify into a precipitate-laden, viscous slurry.

The reaction flask is placed in a 30.degree. C. bath and allowed to sit for two days The reaction is then terminated with 0.5 mL of 1 wt % of hydroquinone in water. The reaction mixture is diluted with 100 mL of water and stirred until a uniform reaction product is precipitated by adding the dilute reaction mixture dropwise to 1 liter of 2-propanone or other suitable nonsolvent for the graft copolymer. The solid is recovered from 2-propanone by filtration and dried under vacuum at 40.degree. C. To obtain a higher purity product which is more readily soluble, the reaction product is recovered from nonsolvent by filtration and redissolved in water. The same number of moles of disodium oxalate is added to the product as there were moles of calcium chloride in the reaction mixture to precipitate the calcium ion in the product. The aqueous solution with precipitate is dialyzed against pure water using a 3,500-upper-molecular-weight-permeable, dialysis membrane for several days. The polymer solution is centrifuged at 6000 rpm for 35 minutes to sediment the precipitate and the supernate, pure polymer solution is poured off. The aqueous solution containing the solid is then freeze-dried.

It is preferred that all reagents used be of reagent grade purity but less pure materials may be used if they do not contain inhibitors for the reaction. Other concentrations of cerium (+IV) ion solution in other nonreactive solvents can be used to add this reagent to the reaction and, indeed, this reagent is not necessary for the reaction. The 0.05M cerium (+IV) sulfate solution is stable and convenient to use. However, the concentration of the ceric sulfate solution used can vary from about 0.01M to 0.3M. Other reagents that may be used in place of a ceric ion (Ce.sup.4+) include vanadium (V.sup.+5) or manganese ions (Mn.sup.3+,Mn.sup.4+,Mn.sup.7+). It is preferred that the metal salt be added as an aqueous solution. Moreover, ceric salts are a preferred reagent for the graft polymerization. The reaction can be run without adding cerium or other oxidizing metal ions but slightly higher yields and better solubility properties are obtained when the oxidizing metal ion is added. The graft copolymer can and will be produced if this reagent is not added to the synthesis mixture but product properties are improved by the addition of cerium (+4) solution. Other changes in this procedure, evident to those skilled in synthesis or chemical manufacture can be made. The graft copolymer can also be produced by adding nitrogen-saturated 2-propenamide to the reaction mixture in another solvent.

Other hydroperoxides, such as inorganic hydroperoxides or t-butyl hydroperoxide, may be used in place of the hydrogen peroxide listed above. The graft copolymerization reaction can be conducted with or without stirring once the monomer and metal salt have been dispersed in the reaction mixture. The reaction is allowed to proceed for 1 to 200 hours, with 48 hours being a typical reaction time. It is preferred to terminate the copolymerization by addition of a free radical scavenger such as hydroquinone.

The graft terpolymer is easily recovered from a liquid reaction mixture. If the reaction mixture is a gel or thick slurry, it can be made pourable by mixing therewith 1 to 3 times its volume of distilled or deionized water under low shear conditions until a homogeneous, pourable system is formed. The reaction mixture is added to 2-20, preferably 5-10, times its volume of a nonsolvent for the polymer, such as 2-propanone. Preferably the nonsolvent is stirred vigorously so as to form a vortex and the copolymer solution is slowly drained directly into the center of this vortex. The precipitated graft copolymer is then removed from the nonsolvent solution by filtration, washed with nonsolvent, filtered, and vacuum-dried to a constant weight. A purer product can be obtained by the dialysis-freeze drying process described above.

The following examples illustrate certain embodiments of this invention wherein parts and percentages are by weight and temperatures are in centigrade unless otherwise indicated. Indulin AT, a commercial lignin product of the Westvaco Corporation, and Eastman reageat-grade 2-propenamide were used in these synthesis. The compound 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene chloride was obtained from Alcolac Specialty Chemicals of 3440 Fairfield Road, Baltimore, Md. 21226, as a 75 weight percent solution in water. It was purified by freeze drying to remove water and recrystallized from ethanol-(2-propanone)(20:80 mixture by volume). The purified crystals were dried under vacuum and stored in a freezer. The compound 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene methylsulfate was obtained from CPS Chemical Company, Inc., of P.O. Box 162, Old Bridge, N.J. 08857, as an 80 weight percent solution in water. It was purified by freeze drying to remove water and recrystallized from ethanol-(2-propanone)(20:80 mixture by volume). The purified crystals were dried under vacuum and stored in a freezer. Paradioxane and dimethyl sulfoxide, of reagent grade, from Mallinckrodt Chemical Company and anhydrous calcium chloride also therefrom were used in these examples. Ceric sulfate solution was prepared from reagent grade ceric sulfate and distilled water. The hydroquinone solution was 1 wt % hydroquinone in distilled water. The limiting viscosity number of the product in pure water was determined using the Fuoss equation (a) to extrapolate several viscosity measurements, .eta., to zero polymer concentration.

C/.eta..sub.sp =1/[.eta.]+Q.sub.f C.sup.1/2

Here .eta..sub.sp =(.eta.-.eta.o)/.eta..sub.o, C is polymer concentration in g/dL, Q.sub.f is a fitting constant, and [.eta.] is limiting viscosity number. See J. Poly. Sci., 3,603-604 (1948).

The present invention will now be further illustrated by certain examples and references which are provided for purposes of illustration only and are not intended to limit the present invention.

Yield was calculated from the formula: (g=grams) ##EQU1##

EXAMPLES

Example 1

A total of 0.5 g of lignin and 0.38 g of calcium chloride were placed in a 125 mL test tube containing 20.0 g of dimethylsulfoxide. The mixture was stir-bubbled with nitrogen (N.sub.2) for about 2 minutes before 0.50 mL of 30 percent, aqueous hydrogen peroxide was added to the reaction mixture. N.sub.2 was bubbled through the reaction mixture for about 2 more minutes, the system was stirred for about 20 minutes, and 1.40 g of 2-propenamide (I) was then added. After about 2 minutes of stirring and N.sub.2 bubbling, 1.18 g of 2-propenamide (I) and 1.94 g of 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene chloride (II) in 11.08 g of dimethylsulfoxide were added. After 10 minutes of stirring and bubbling N.sub.2 through the reaction mixture, the flask was stoppered and placed in a 30.degree. C. bath for 2 days. The mole ratio of monomer I to II in the reaction solution was 4 to 1. The chloride content of the reaction mixture was 1.554 weight percent. The reaction was then terminated by adding 0.5 mL of 1% hydroquinone and 100 mL of water thereto. The stirred reaction mixture was precipitated in 1/2 L of 2-propanone and recovered by filtration. The recovered solid was dissolved in 100 mL of water and 0.46 g of disodium oxalate was added to the produce to precipitate the calcium ion in the product. The aqueous solution with precipitate was dialyzed against pure water using a 3,500-upper-molecular-weight-permeable, dialysis membrane from 3 days. The polymer solution was centrifuged at 6000 rpm for 35 minutes to sediment the precipitate and the supernate, pure polymer solution was poured off. The dilute reaction product from the dialysis tube was recovered by freeze drying and found to weigh 4.59 g. The product was labeled 24-136-1. Yield=91.43 wt %. The nitrogen content of the product was 11.62 weight percent. Limiting viscosity number, [.eta.], of the product was 13.07 dL/g.

Example 2

A total of 0.5 g of lignin and 0.26 g of calcium chloride were placed in a 125 mL test tube containing 20.0 g of dimethylsulfoxide. The mixture was stir-bubbled with nitrogen (N.sub.2) for about 2 minutes before 0.50 mL of 30 percent, aqueous hydrogen peroxide were added to the reaction mixture. N.sub.2 was bubbled through the reaction mixture for about 2 more minutes, the system was stirred for about 20 minutes, and 1.40 g of 2propenamide (I) was then added. After about 2 minutes of stirring and N.sub.2 bubbling, 0.85 g of 2-propenamide (I) and 2.82 g of 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene chloride (II) in 14.82 g of dimethylsulfoxide were added. After about 10 minutes of stirring and bubbling N.sub.2 through the reaction mixture, the flask was stoppered and placed in a 30.degree. C. bath for 2 days. The mole ratio of monomer I to II in the reaction solution was 7 to 3. The chloride content of the reaction mixture was 1.570 weight percent. The reaction was then terminated by adding 0.5 mL of 1% hydroquinone and 100 mL of water thereto. The stirred reaction mixture was precipitated in 1/2 L of 2-propanone and recovered by filtration. The recovered solid was dissolved in 100 mL of water and 0.32 g of disodium oxalate was added to the product to precipitate the calcium ion in the product. The aqueous solution with precipitate was dialyzed against pure water for 3 days. The polymer solution was centrifuged at 6000 rpm for 35 minutes to sediment the precipitate and the supernate, pure polymer solution was poured off. The dilute reaction product from the dialysis tube was recovered by freeze drying and found to weight 5.24 g. The product was labeled 24-136-2. Yield=94.07 wt %. The nitrogen content of the product was 10.36 weight percent. Limiting viscosity number, [.eta.], of the product was 16.07 dL/g.

Example 3

A total of 0.5 g of lignin and 0.11 g of calcium chloride were placed in a 125 mL test tube containing 20.0 g of dimethylsulfoxide. The mixture was stir-bubbled with nitrogen (N.sub.2) for about 2 minutes before 0.50 mL of 30 percent, aqueous hydrogen peroxide was added to the reaction mixture. N.sub.2 was bubbled through the reaction mixture for about 2 more minutes, the system was stirred for about 20 minutes, and 1.41 g of 2propenamide (I) was then added. After about 2 minutes of stirring and N.sub.2 bubbling, 0.52 g of 2-propenamide (I) and 3.73 g of 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene chloride (II) in 19.40 g of dimethylsulfoxide were added. After about 10 minutes of stirring and bubbling N.sub.2 through the reaction mixture, the flask was stoppered and placed in a 30.degree. C. bath for 2 days. The mole ratio of monomer I to II in the reaction solution was 3 to 2. The chloride content of the reaction mixture was 1.534 weight percent. The reaction was then terminated by adding 0.5 mL of 1% hydroquinone and 100 mL of water thereto. The stirred reaction mixture was precipitated in 1/2 L of 2-propanone and recovered by filtration. The recovered solid was dissolved in 100 mL of water and 0.13 g of disodium oxalate was added to the product to precipitate the calcium ion in the product. The aqueous solution with precipitate was dialyzed against pure water for 3 days. The polymer solution was centrifuged at 6000 rpm for 35 minutes to sediment the precipitate and the supernate, pure polymer solution was poured off. The dilute reaction product from the dialysis tube was recovered by freeze drying and found to weigh 5.62 g. The product was labeled 24-136-3. Yield=91.23 wt %. The nitrogen content of the product as 9.09 weight percent. Limiting viscosity number, [.eta.], of the product was 39.84 dL/g.

Example 4

A total of 0.5 g of lignin and 0.01 g of calcium chloride were placed in a 125 mL test tube containing 20.0 g of dimethylsulfoxide. The mixture was stir-bubbled with nitrogen (N.sub.2) for about 2 minutes before 0.50 mL of 30 percent, aqueous hydrogen peroxide was added to the reaction mixture. N.sub.2 was bubbled through the reaction mixture for about 2 more minutes, the system was stirred for about 20 minutes, and 1.40 g of 2-propenamide (I) was then added. After about 2 minutes of stirring and N.sub.2 bubbling, 0.21 g of 2-propenamide (I) and 4.67 g of 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene chloride (II) in 25.31 g of dimethylsulfoxide were added. After about 10 minutes of stirring and bubbling N.sub.2 through the reaction mixture, the flask was stoppered and placed in a 30.degree. C. bath for 2 days. The mole ratio of monomer I to II in the reaction mixture was 1 to 1. The chloride content of the reaction mixture was 1.530 weight percent. The reaction was then terminated by adding 0.5 mL of 1% hydroquinone and 100 mL of water thereto. The stirred reaction mixture was precipitated in 1/2 L of 2-propanone and recovered by filtration. The recovered solid was dissolved in 100 mL of water and 0.01 g of disodium oxalate was added to the product to precipitate the calcium ion in the product. The aqueous solution with precipitate was dialyzed against pure water for 3 days. The polymer solution was centrifuged and the supernate, pure polymer solution was poured off. The dilute reaction product from the dialysis tube was recovered by freeze drying and found to weigh 6.15 g. The product was labeled 24-136-4. Yield=90.71 wt %. The nitrogen content of the product was 7.76 weight percent. Limiting viscosity number, [.eta.], of the product was 39.85 dL/g.

Note that these four examples, numbers 1 to 4, show that different mole ratios of monomers can be used to produce product in yields in excess of 90 weight percent if the chloride ion content of the reaction mixture is maintained at between 1.53 and 1.57 weight percent. This optimum chloride ion content must be found for a given solvent system by experimental tests. It is maintained by lowering the amount of calcium chloride added to the reaction to compensate for the amount of chloride ion contained in the positively charged monomer.

Example 5

A total of 0.51 g of lignin and 0.88 g of calcium chloride were placed in a 125 mL test tube containing 10.0 g of dimethylsulfoxide. The mixture was stir-bubbled with nitrogen (N.sub.2) for about 2 minutes before 0.50 mL of 30 percent, aqueous hydrogen peroxide was added to the reaction mixture. N.sub.2 was bubbled through the reaction mixture for about 2 more minutes, the system was stirred for about 20 minutes, and 1.39 g of 2propenamide (I) in 10.0 g of dimethylsulfoxide was then added. After about 2 minutes of stirring and N.sub.2 bubbling, 1.17 g of 2-propenamide (I) and 2.55 g of 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene methylsulfate (II) in 10.08 g of dimethylsulfoxide were added. After 10 minutes of stirring and bubbling N.sub.2 through the reaction mixture, the flask was stoppered and placed in a 30.degree. C. bath for 2 days. The mole ratio of monomer I to II in the reaction solution was 4 to 1. The chloride content of the reaction mixture was 1.519 weight percent. The solids content of the reaction mixture was 18.89 weight percent. The reaction was then terminated by adding 0.5 mL of 1% hydroquinone and 100 mL of water thereto. The stirred reaction mixture was precipitated in 1/2 L of 2-propanone and recovered by filtration. The recovered solid was dissolved in 100 mL of water and 1.06 g of disodium oxalate was added to the product to precipitate the calcium ion in the product. The aqueous solution with precipitate was dialyzed against pure water using a 3,500-upper-molecular-weight-permeable, dialysis membrane for 3 days. The polymer solution was centrifuged at 6000 rpm for 35 minutes to sediment the precipitate and the supernate, pure polymer solution was poured off. The dilute reaction product from the dialysis tube was recovered by freeze drying and found to weigh 4.34 g. The product was labeled 24-139-1. Yield=77.22 wt %. Limiting viscosity number, [.eta.], of the product was 5.07 dL/g.

Example 6

A total of 0.50 g of lignin and 0.93 g of calcium chloride were placed in a 125 mL test tube containing 10.0 g of dimethylsulfoxide. The mixture was stir-bubbled with nitrogen (N.sub.2) for about 2 minutes before 0.50 mL of 30 percent, aqueous hydrogen peroxide were added to the reaction mixture. N.sub.2 was bubbled through the reaction mixture for about 2 more minutes, the system was stirred for about 20 minutes, and 1.39 g of 2-propenamide (I) in 10.0 g of dimethylsulfoxide was then added. After about 2 minutes of stirring and N.sub.2 bubbling, 0.53 g of 2-propenamide (I) and 5.15 g of 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene methylsulfate (II) in 10.72 g of dimethylsulfoxide were added. After 10 minutes of stirring and bubbling N.sub.2 through the reaction mixture, the flask was stoppered and placed in a 30.degree. C. bath for 2 days. The mole ratio of monomer I to II in the reaction solution was 3 to 2. The chloride content of the reaction mixture was 1.500 weight percent. The calcium chloride content was 2.34 weight percent. The solids content of the reaction mixture was 22.66 weight percent. The reaction was then terminated by adding 0.5 mL of 1% hydroquinone and 100 mL of water thereto. The stirred reaction mixture was precipitated in 1/2 L of 2-propanone and recovered by filtration. The recovered solid was dissolved in 100 mL of water and 1.12 g of disodium oxalate was added to the product to precipitate the calcium ion in the product. The aqueous solution with precipitate was dialyzed against water for 3 days. The polymer solution was centrifuged at 6000 rpm for 35 minutes to sediment the precipitate and the supernate, pure polymer solution was poured off. The dilute reaction product from the centrifugation was recovered by freeze drying and found to weigh 6.07 g. The product was labeled 24-139-2. Yield=80.18 wt %. Limiting viscosity number, [.eta.], of the product was 23.41 dL.

Example 7

A total of 0.50 g of lignin and 0.99 g of calcium chloride were placed in a 125 mL test tube containing 10.0 g of dimethylsulfoxide. The mixture was stir-bubbled with nitrogen (N.sub.2) for about 2 minutes before 0.50 mL of 30 percent, aqueous hydrogen peroxide was added to the reaction mixture. N.sub.2 was bubbled through the reaction mixture for about 5 more minutes. Then 1.29 g of 2-propenamide (I) and 8.36 g of 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene methylsulfate (II) in 19.28 g of dimethylsulfoxide were added. After 10 minutes of stirring and bubbling N.sub.2 through the reaction mixture, the flask was stoppered and placed in a 30.degree. C. bath for 2 days. The mole ratio of monomer I to II in the reaction solution was 2 to 3. The chloride content of the reaction mixture was 1.547 weight percent. The calcium chloride content was 2.42 weight percent. The solids content of the reaction mixture was 28.45 weight percent. The reaction was then terminated by adding 0.5 mL of 1% hydroquinone and 100 mL of water thereto. The stirred reaction mixture was precipitated in 1/2 L of 2-propanone and recovered by filtration. The recovered solid was dissolved in 100 mL of water and 1.19 g of disodium oxalate was added to the product to precipitate the calcium ion in the product. The aqueous solution with precipitate was dialyzed against water for 3 days. The polymer solution was centrifuged to sediment the precipitate and the supernate, pure polymer solution was poured off. The dilute reaction product from the centrifugation was recovered by freeze drying and found to weigh 7.15 g. The product was labeled 24-139-3. Yield=70.44 wt %. Limiting viscosity number, [.eta.], of the product was 41.73 dL/g.

Example 8

A total of 0.50 g of lignin and 1.02 g of calcium chloride were placed in a 125 mL test tube containing 10.0 g of dimethylsulfoxide. The mixture was stir-bubbled with nitrogen (N.sub.2) for about 2 minutes before 0.50 mL of 30 percent, aqueous hydrogen peroxide was added to the reaction mixture. N.sub.2 was bubbled through the reaction mixture for about 5 more minutes. Then 0.64 g of 2-propenamide (I) and 10.21 g of 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene methylsulfate (II) in 21.40 g of dimethylsulfoxide were added. After 10 minutes of stirring and bubbling N.sub.2 through the reaction mixture, the flask was stoppered and placed in a 30.degree. C. bath for 2 days. The mole ratio of monomer I to II in the reaction solution was 1 to 4. The chloride content of the reaction mixture was 1.474 weight percent. The calcium chloride content was 2.304 weight percent. The solids content of the reaction mixture was 29.07 weight percent. The reaction was then terminated by adding 0.5 mL of 1% hydroquinone and 100 mL of water thereto. The stirred reaction mixture was precipitated in 1/2 L of 2-propanone and recovered by filtration. The recovered solid was dissolved in 100 mL of water and 1.23 g of disodium oxalate was added to the product to precipitate the calcium ion in the product. The aqueous solution with precipitate was dialyzed against water for 3 days. The polymer solution was centrifuged to sediment the precipitate and the supernate, pure polymer solution was poured off. The dilute reaction product from the centrifugation was recovered by freeze drying and found to weigh 10.33 g. The product was labeled 24-139-4. Yield=91.40 wt %. Limiting viscosity number, [.eta.], of the product was 55.03 dL/g.

Note that these reactions, examples 5 to 8, yield more than 80 weight percent product but yields are not as high as those of examples 1 to 4. Thus, these reactions, while not run at an optimum concentration of chloride ion in the reaction mixture, still produce a large yield of graft polymer. Further, these products also have different amounts of charged and uncharged repeat units in the product and that difference is produced by varying the monomer ratio between the two repeat units.

Example 9

A total of 0.50 g of lignin and 1.07 g of calcium chloride were placed in a 125 mL test tube containing 10.0 g of dimethylsulfoxide. The mixture was stir-bubbled with nitrogen (N.sub.2) for about 2 minutes before 0.50 mL of 30 percent, aqueous hydrogen peroxide was added to the reaction mixture. N.sub.2 was bubbled through the reaction mixture for about 5 more minutes. Then 12.77 g of 2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct-1-ene methylsulfate (II) in 21.40 g of dimethylsulfoxide was added. After 10 minutes of stirring and bubbling N.sub.2 through the reaction mixture, the flask was stoppered and placed in a 30.degree. C. bath for 2 days. The mole ratio of monomer I to II in the reaction solution was 0 to 100. This sample utilized only II monomer to form poly(lignin-g-(1-methyl-1-(N5,N5-dimethyl-5-ammonium-1-oxo-2-oxyhexyl)ethy lene methylsulfate)), a graft copolymer with a one repeat unit sidechain. The chloride content of the reaction mixture was 1.503 weight percent. The calcium chloride content was 2.350 weight percent. The solids content of the reaction mixture was 32.58 weight percent. The reaction was then terminated by adding 0.5 mL of 1% hydroquinone and 100 mL of water thereto. The stirred reaction mixture was precipitated in 1/2 L of 2-propanone and recovered by filtration. The recovered solid was dissolved in 100 mL of water and 1.29 g of disodium oxalate was added to the product to precipitate the calcium ion in the product. The aqueous solution with precipitate was dialyzed against water for 3 days. The polymer solution was centrifuged to sediment the precipitate and the supernate, pure polymer solution was poured off. The dilute reaction product from the centrifugation was recovered by freeze drying and found to weigh 9.40 g. The product was labeled 24-139-5. Yield=70.91 wt %. Limiting viscosity number, [.eta.], of the product was 85.64 dL/g.

The product of Example 9 is poly(lignin-co-(1-methyl-1-(N5,N5-dimethyl-5-ammonium-1-oxo-2-oxyhexyl) ethylene)), a graft copolymer with all charged repeat units in the sidechain.

The data of the following Table I shows that the products of this invention are effective viscosifiers for water.

TABLE 1 __________________________________________________________________________ Viscosities of Aqueous Solutions of Graft Terpolymer *Viscosity when product concentration in water Product from Sample is (wt %): Example Number Number 1.0 0.298 0.199 0.0997 0.050 __________________________________________________________________________ 9 24-139-5 -- 5.115 4.373 3.182 2.323 0.300 0.197 0.1003 0.0501 0.025 0.0099 8 24-139-4 4.424 3.618 2.749 2.013 1.481 1.108 0.1 0.0747 0.037 0.015 0.0099 7 24-139-3 1.904 1.918 1.501 1.134 1.019 0.102 0.0597 0.030 0.0100 6 24-139-2 1.557 1.321 1.113 0.923 0.298 0.154 0.102 0.0703 5 24-139-1 1.413 1.166 1.057 0.958 1.0 0.322 0.165 0.0997 0.0502 4 24-136-4