GRAFT COPOLYMERS OF LIGNIN (2-PROPENAMIDB)- (1-PHENYLETHENE) METHOD OF MAKING SAME AND USES THEREFOR

Field of the Invention

Thepresent invention relates tograft copolymers of lignin-(2-propenamide)-(l-phenylethene), methods of making the same, and uses therefore.

Background of the Invention

Thermoset and thermoplastic materials have provided significant performance advantages because of their relatively high strength compared to weight. In devices ranging from consumer items to complex industrial equipment, the utility of the devices would be greatly enhanced by such advantages. Often it is not cost effective to make goods from pure thermosets and thermoplastics because of the high material and formation costs of the article. It would be advantageous to produce parts in a standard thermoplastic molding process, where the parts are strong, two component materials that contain a large amount of an industrial waste product, lignin. By this means, the disadvantages of high formation and chemical costs would be offset.

Attempts to produce grafted lignin-containing- material with water-soluble, intermediate polarity monomers such as 2-propenamide have been successful in the past. However, problems are encountered in grafting lignin- containing-material if similarly subsituted ethenes with a different dipole moment and sharply reduced water solubility are used in place of 2-propenamide in previously disclosed synthesis methods. With ethene monomers with dipole moments below 1.2 or above 1.8 and water solubilities of less than 5.0g of monomer per lOOg of water at 30°C, reactions run according to previously disclosed procedures and without a critial step give zero yield of graft copolymer.

The invention provides a method to convert birch, red oak, poplar, or other lignin into a useful and desirable r commodity. The material is a graft copolymer of lignin and styrene and/or 2-propenamide. It is a hard, strong, thermoplastic that can be molded, cast, and extruded into parts, equipment, and consumer items. Without the chemistry described herein, a mixture of lignin and polyd- phenylethylene) or its copolymers would phase separate. Such a two phase mixture cannot be used to form parts and articles.

Summary of the Invention

The invention comprises a graft copolymer of. lignin which is a lignin containing material which is at least one of lignin, wood, wood fiber and wood pulp, the lignin having a central lignin network and at least one grafted side chain having randomly repeating units R and R2 wherein at least one of Ri and R2 is a substituted ethene polymerizable by free radical polymerization, and l and R2 are selected from the group of alkanes, alkenes, amides, acids, alcohols, alkoxides, esters and such groups substituted with one or more selected from the group of halogens, cycloalkane, phenol and nitrile groups and such groups further substituted with one or more groups.

The invention provides a lignin graft copolymer which possesses the desirable properties of a thermoplastic: strength, impact resistance, and deformability at higher temperature; and a method of boosting or enhancing polymer molecular weights and polymer yields during polymerization reactions. In a preferred embodiment, the invention comprises a graft copolymer of lignin-(2-propenamide)-(l- phenylethene) having a central lignin network and at least one grafted side chain, R, having randomly repeating units of the formulas:

- (CH ₂ -CH ) _m -

C=0 \ NH ₂

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 5 to 300,000 units, such that the total copolymer molecular weight is in the range of 7,000 to 30,000,000. The resulting molecule can bear multiple side chains. Preferably, the fraction of amide versus phenyl repeating units ranges from about 0.0 to 99.8 molar percent and the fraction of phenyl versus amide repeating units ranges from 100.0 to 0.2 molar percent.

The present invention also provides a process for making a lignin graft copolymer at high yield or lignin content which possesses the desirable properties of a thermoplastic. The method enhances polymer molecular weights andpolymer yields during polymerization reactions.

as compared to the prior art methods, such as described in U.S. Patent No. 4,889,902.

A preferred method includes a series of steps to synthesize a graft copolymer of lignin and a monomer having a central lignin network and at least one grafted side chain, R, having randomly repeating units of the formulas:

-(CH ₂ -CH) _m -

I R

where R could be a phenyl unit to give a repeat unit of the formula -

or R could be

C=0

\

NH ₂

or any other substituent producing a substituted ethene polymerizable by free radical polymerization.

Detailed Description of the Preferred Embodiaent

In accordance with the present invention, there is provided a high molecular weight graft copolymer. The invention comprises a graft copolymer of lignin which is a lignin containing material which is at least one of lignin, wood, wood fiber and wood pulp, the lignin having a central lignin network and at least one grafted side chain having randomly repeating units Ri and R2 wherein at least one of Ri and R is a substituted ethene polymerizable by free radical polymerization, and the side groups on i and 2 are selected from the group of alkanes, alkenes, amides, acids, alcohols, alkoxides, esters, halogens, cycloalkane, phenol and nitrile groups and such groups further substituted with one or more groups. The invention provides a lignin graft copolymer which possesses the desirable properties of a thermoplastic: strength, impact resistance, and deformability at higher temperature; and a method of boosting or enhancing polymer molecularweights andpolymer yields during polymerization reactions.

In a preferred embodiment, the invention comprises a graft copolymer of lignin-(2-propenamide)-(l- phenylethene) having a central lignin network and at least one grafted side chain, R, having randomly repeating units of the formulas:

- (CH ₂ -CH ) _m -

C=0

\

NH ₂

and

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 5 to 300,000 units, such that the total copolymer molecular weight is in the range of 1,000 to 30,000,000. The resulting molecule can bear multiple side chains. Preferably, the fraction of amide versus phenyl repeating units ranges from bout 0.0 to 99.8 molar percent and the fraction of phenyl versus amide repeating units ranges from 100.0 to 0.2 molar percent.

The present invention also provides a process for making a lignin graft copolymer at high yield or lignin

content which possesses the desirable properties of a thermoplastic. The method enhances polymer molecular weights andpolymer yields during polymerization reactions, as compared to the prior art methods, such as described in U.S. Patent No. 4,889,902.

This new method circumvents the synthesis failures which are encountered when 2-propenamide is replaced by another substituted ethene with a different dipole moment and sharply reduced water-solubility. To react ethene monomers with dipole moments below 1.2 or above 1.8 and water solubilities of less than 5.0g of monomer per lOOg of water at 30°C with a lignin-contining- material to produce grafted lignin-containing product requires continous stirring during the reaction, preferrably at a controlled stirring rate such stirring is critical and in the absence of stirring, a grafted copolymer of lignin simply cannot be produced.

A preferred method includes a series of steps to synthesize a graft copolymer of lignin and a monomer having a central lignin network and at least one grafted side chain, R, having randomly repeating units of the formulas:

- (CH ₂ -CH ) _m -

I Rl

where R! could be a phenyl unit to give a repeat unit of the formula

or Rl could be

C=0 \ H ₂

or any other substituent producing a substituted ethene polymerizable by free radical polymerization. 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, in 1978, _it has been estimated that the U.S. chemical-pulp industry produced 1.55xl0 ⁷ metric tons of alkali lignin and 1.6xlθ6 metric 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:

lt 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. Of the lignins which may be used according to the present invention, there may be mentioned alkali lignins, HC1 lignins, milled wood lignins (MWL) and 1,4-dioxane lignins, for example.

Alkali lignins are used in some of the examples which follow below. 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 material which increase in water solubility as the pH increases from 7 toward 14 and become completely soluble in 5 weight percent aqueous sodium hydroxide solutions. Alkali lignins have, as a basic repeating unit, the oxyphenylpropyl unit:

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 andmay be replaced bymetal cations, such as sodium, potassium, calcium, or ammonium ions, to form alkali lignin salts. Alkali lignins are readily identified bymethod of production and are

a familiar class of compounds to those versed in the paper making art.

In preparing the graft copolymer of lignin, there is grafted to the lignin macromolecule, perhaps to the aromatic ring of the oxyphenylpropene moiety, repeating units of 1- a idoethylene:

-(CH ₂ -CH) _m -

C=0

\

NH ₂

in combination with repeating units of (1-phenylethylene):

or any other substituted ethene polymerizable by free radical polymerization,

-(CH ₂ -CH) _m -

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

Lignin ♦ n

Lignin-(-CH ₂ -CH-) _t -(-CH ₂ -CH-).-

C=0 I NH ₂

when m =_ 0 , a lignin graft copolymer of the following formula is produced:

Lignin + n

The preparation of this copolymer is accomplished, in general, under oxygen-free conditions by adding a redox initiator; a halide salt, chloride salt preferred; 2- propenamide; and 1-phenylethene to a lignin dispersion in a suitable solvent and allowing time for graft polymerization to occur.

Example A

This example. Example A, provides the basic, non- quantitative, method. Significant variation in reaction mixture composition and preparation procedure are possible as will be illustrated in subsequent examples which follow Example A.

The basic method for the preparation of lignin-(2- propenamide)-(l-phenylethene) graft copolymer in dimethylsulfoxide for a sample composed of between 0.32 and 10.0 weight percent lignin; 0.0 and 7.6 weight percent 2- propenamide; 0.1 and 30.0 weight percent 1-phenylethene; 0.3

to 15.3 weight percent calcium halide salt, chloride salt preferred; and 50 to 97 weight percent solvent; are presented here.

The method generally comprises: a) An aliquot of one-half to all of the purified solvent is placed in a sealable reaction vessel. Some suitable solvents for the reaction are listed in Table 1. b) Lignin and finely ground anhydrous halide salt, chloride salt preferred are added to the pure solvent. Typical lignins used in the reaction are listed in Table 2A and typical salts are listed in Table 2B. c) The mixture is stirred for about 20 minutes to dissolve the solids while being bubbled with nitrogen. d) After 10 minutes of nitrogen saturation, a hydroperoxide such as hydrogen peroxide or 2-hydroperoxy-l,4- dioxycyclohexane is added to the reaction mixture. A selection of suitable hydroperoxides for the graft copolymerization are shown in Table 3. e) An ethene monomer polymerizable by free radical reaction is added to the reaction vessel under a gas blanket inert to free radical reactions. The monomer may be in gaseous, liquid, or solid form but should be saturated with and maintained under the inert atmosphere. Preferred methods are to add the monomer as a nitrogen-saturated solid or nitrogen-saturated liquid. The most preferred method for this disclosure is to

add nitrogen-saturated: (1) solid 2-propenamide, (2) pure 1- phenylethene, and/or (3) any solution of (1) and/or (2) in the remaining fraction of the solvent not added in step (a). f) After about 10 minutes, 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. g) The reaction flask is placed in a 30°C bath and is continuously stirred for two days. The rate of stirring depends upon the amount of 1-phenylethylene monomer in the monomer mixture and the shape and structure of the reaction vessel. The duration of the reaction can be readily varied. h) The reaction is then terminated by addition of 1 weight percent of hydroquinone in water or exposure to air. i) The reaction mixture is dripped into a volume of water equal to about 10 times the volume of the reaction and stirred until a uniform reaction product is precipitated. j) If the reaction mixture contained no 2- propenamide, about 2 volume percent of the water used in the precipitation step (i), is 2M HC1, and the product is allowed to settle from the resulting slurry. k) The solid is recovered by filtration and dried under vacuum at 30°C.

Organic liquids are a suitable solvent for the graft copolymerization and preferably an organic polar, aprotic solvent, such as dimethyl sulfoxide (DMSO) , dimethyl acetamide (DMAc), dimethyl formamide (DMF), 1,4-dioxane, l-methyl-2- pyrrolidianone and/or pyridine is used. Mixtures of these solvents in various proportions can also be used such as 50/50 (vol/vol) mixtures of DMSO and 1,4-dioxane; and a 50/50 (vol/vol) mixture of DMSO with water.

TABLE 1 Liquids Used in Solution Polymerization of Graft

Copolymers

Dimethyl Sulfoxide (DMS0) ^a Dimethylacetaraide

1,4-Dioxacyclohexane ^a Dimethylformamide

Water ^a l-Methyl-2-pyrroli- Pyridine dinone

Most frequently used liquids

The choice of lignin is apparently general. That is, a whole series of lignins withdrawn from wood by different techniques have been grafted by this method, as shown by the data of Table 2.

TABLE 2

Lignins Grafted with this Chemistry and Salts

Dsed

A. LIGNINS Source

Calcium Chloride CaCl2 Sodium Bromide NaBr Magnesium Chloride MgCl2 Potassium Bromide KBr Sodium Chloride NaCI Lithium Bromide LiBr Potassium Chloride KC1 Calcium Fluoride CaF Lithium Chloride LiCl Magnesium Fluoride MgF2 Calcium Bromide CaBr2 Sodium Fluoride NaF Magnesium Bromide MgBr2 Potassium Fluoride KF Lithium Fluoride LiF

^a Pine lignins from the Westvaco Corporation of

Charleston, S.C. ^D Aspen lignins from the Solar Energy Research

Laboratories of Golden, CO ^c Yellow Poplar lignins from BioRegional Energy Associates of Floyd, VA

All of the multitude of samples received were used "as is" and were laboratory, pilot plant, or commercially-produced lignins.

TABLE 3

Hydroperoxides Useful in Polymerization of Graft

Copolymers

hydrogen peroxide 2-hydroperoxy-l,4 -dioxycyclohexane

3,3 dimethyl-l,2-dioxybutane

Anhydrous Solid Peroxides sodium peroxyborate magnesium sodium percarbonate peroxyphthalate

The hydroperoxide 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 nitrogen- saturated solution of 1-phenylethene, pure or in solvent, are added while nitrogen gas is bubbled into the mixture. Yield is calculated from the formula:

weight percent (q polymer recovered) yield g lignin + g monomer added added; where g=grams

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 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.

The reaction is allowed to proceed for 1 to 200 hours, with 48 hours being a typical reaction time. It is common to terminate the copolymerization by addition of a free radical scavenger such as hydroquinone.

In the examples, parts and percentages are by weight and temperatures are in centigrade unless otherwise indicated.

Indulin AT, a commercial ligninproduct of the Westvaco Corporation, and Eastman reagent-grade 2-propenamide were used inmost of these syntheses. Yellowpoplar lignin-fromBioRegional Energy Associates of Floyd, Virginia were used in some of the reactions. Some of the lignin used in the copolymerizations described below was extracted with benzene for 48 hours at a ratio of 1 g lignin to 10 to 15 mL of benzene using a Soxhlet apparatus. This removed the low molecular weight portion of the lignin (approximately 3 to 5 weight percent) and allowed certain fractionation experiments to be done on the graft copolymer. This extraction process is not necessary for successful copolymerization of the lignin, however.

The compound 1-phenylethene was obtained from the Laboratory and Research Products Division of Kodak, Rochester, New York 14650. The 1-phenylethene was purified to remove the stabilizer by washing the monomer three times with aqueous base at a ratio of 1 g 1-phenylethene to 1 mL of 2N NaOH. The

stabilizer-free monomer was washed with distilled water to pH = 7 and dried with anhydrous calcium chloride for 2 days. It was then distilled under vacuum at 40°C and 20 mm Hg pressure. The central cut was collected in dark bottles and stored in a refrigerator.

Paradioxane and dimethyl sulfoxide, of reagent grade, are from Mallinckrodt Chemical Company and anhydrous calcium chloride is also from Mallinckrodt. Other halide salts used in the experiments came from Fisher, J.T. Baker, and Merck Companies. The hydroquinone solution was 1 weight percent hydroquinone in distilled water.

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. r

Example 1

A total of 1.00 g of yellow poplar lignin and 1.30 g of calcium chloride were placed in a 125 mL conical flask containing 22.56 g of dimethylsulfoxide. This was labeled solution A.

A total of 6.07 g of 2-propenamide and 0.46 g of 1- phenylethene were placed in a 125 mL conical flask containing 22.57 g of dimethylsulfoxide. This was labeled solution B. Solution A was stir-bubbled with nitrogen (N > for about 11

minutes before 0.964 mL of 29.86 percent, aqueous hydrogen peroxide were added to the reaction mixture. 2 was bubbled through the reaction mixture (A) and it was stirred for about 5 more minutes. Solution A was then added to solution B, which had been stirred and bubbled with 2 for 19 minutes while A was being initiated with hydroperoxide.

After a short period of stirring and bubbling 2 through the reaction mixture, the flask was stoppered and placed in a 30°C bath for 2 days. The reaction was not stirred while in the 30°C bath. The reaction was then terminated by adding 7 mL of 1.% hydroquinone thereto. The reaction mixture was diluted with 100 mL of water and allowed to dialyze against pure water for several days. The dilute reaction product from the dialysis tube was recovered by freeze drying and found to weight 5.5 g. The productwas labeled 25-128-LSP1. Yield = 73.0 weightpercent.

Table 4 gives the results from a series of reactions run to determine if 1-phenylethylene side chains could be attached to lignin. Example numbers of these reactions are shown in parentheses. The synthesis procedure is that described in Example 1. The results of Table 4 show that yield falls off as the amount of 1-phenylethene in the reaction increases to more than 50 weight percent of all monomer in the reaction. The data shows that graft copolymer can be made using this reaction but that yields of the order of 25 to 40 weight percent are common when more than half of the monomer added to the

lignin is 1-phenylethene, a nonpolar monomer. These yields are low and make this an impractical polymerization technique for forming graft copolymers.

Further tests were then run to find solvent, reagent and reaction conditions that would maximize yield from the reaction. Some of these reactions are listed in Table 5.

TABLE 4 Grafting of Yellow Poplar Lignin with Monomer Mixtures*

0

All reactions initiated with calcium chloride and hydrogen peroxide.

TABLE 5 0- of Different Solvent, in Grafting Reaction

Sample Number Solvent Used Lignin Material Added (g) -phenylethene NaCI Yield

30-79-1 (7a) Dimethyl acetamide 0.50 5222 SSL ( %)

4.69 0.68

30-79-2 (8a) 0.48 Dimethyl sulfoxide 0.50 0.14 2.7 4.69 0.66

30-79-3 (9a) 0.48 Dioxane 0.50 0.17 3.3 4.70 0.68 0.48 0.31 5.6

Sample Number Solvent Used Lignin Material Added tη .

10 1- ^p nenvmtιhene c Cacl_ , , Yield

30-131-1 ⁽ 7b ⁾ Tetrahydrofuran -.29.2 2.00 SE _1 T

18.79 2.01 2.02 30-131-2 ^(β b ⁾ Dimethylformamlde 1- 7 β.61 2.00 18.79 2.00 30-130-3 (9b) Dioxane 2.02 5.1 24.72 2.00 18.77 2.01 2.02 1.88 9.05

TΛB B 6 Use of Different βalts in Grafting Reaction

10

Low solvent content reaction High solvent content reaction

The dioxane reaction had a higher yield but the lignin did not dissolve completely. As a result, dimethylsulfoxide was chosen for further tests. The data of Table 5 also shows that changing the halide salt used as the coinitiator in a given solvent can sharply boost yield.

The next series of tests focused upon which salt to use to provide chloride ion in the reaction and what amount of solvent to use in the reaction (concentration effects). Some of these datas are given in Table 6. This next set of reactions were run on a larger scale and showed that calcium chloride was the preferred coinitator. Other halide salts can be used in grafting, as the data of Table 6 shows, but yield and conversion of monomer to copolymer is highest when calcium chloride is used in the reaction.

The phase behavior seen in examples 10 and 11 of Table 6 dictated that the reaction be stirred throughout the synthesis. The stirring rate and force will depend on: 1) the amount of 1-phenylethylene monomer in the monomer mixture with higher mole fractions of 1- phenylethylene requiring higher rates of stirring; and 2) the shape and structure of the reaction vessel.

Examples 12 and 13 of Table 6 show the effect of continuous stirring of the reactor with reaction yields of over 94 weight percent from each reaction. The yield for

a comparable, static reaction, example 6 of Table 4, was 40.7 weight percent and the amount of product produced is proximate to the amount of lignin charged to the reactor. It is probable that very little grafting took place in example 6. The data of Tables 4 and 6 thus show that for high yield and extensive grafting, a reaction mixture containing more than 50 weight percent or 30 mol percent nonpolar monomer must be continuously stirred.

The reaction mixture should have a shear rate perpendicular to the direction of stirred flow of between 0.01 per second and 6,000 per second. High shear rates in the reaction should be avoided because they will cause the formed polymer to mechanically degrade. The preferred stirring rate in the conical flask used in laboratory synthesis is 3 to 5 Hertz. This produced a shear rate of approximately 10 to 200 per second in the reaction mixture and this is the preferred shear rate for high yield synthesis.

Reaction 30-87-3, a blank, shows that a hydroperoxide is critical to the reaction since when the hydroperoxide is omitted, the yield of the reaction drops below the amount of lignin added to the reaction. This shows that graft copolymerization is not occurring and that the unreacted lignin starting material is not quantitatively recovered.

Table 7 shows data for a spectrum of reactions run to optimize yield and create samples of different molecular weight and composition. All of these reactions were stirred at a rate of about 4 Hz throughout the synthesis.

TABLE 7 Composition and Yisld of Copolymer Reaction Mixtures

These products have been shown to be poly(lignin-g (1-phenylethylene)) by a series of solubility and extractio tests and are formed with 90% or more grafting efficiency. Thi shows that the reaction being run on lignin is:

Lignin + „ CH ₂ Lignin-fCHj-CH),-

The results of reactions 15 to 20 show th ^ό at there is an optimum ratio of peroxide to chloride to lignin that produces maximum yield and styrene conversion. The spectrum of mole ratios of hydroperoxide to chloride ion tested in these 6 experiments is 0.271 to 1.357 with the optimum yield occurring at a ratio of 0.814. At this ratio, quantitative conversion of styrene to polymer occurs. A 100% conversion of reactants to products is rarely achieved in chemistry. The reactions given above show that we have developed method refinements to synthesize this product routinely with 95 percent or better yield. This is a critical accomplishment since commercial polymer synthesis requires high yield for commercial viability.

The data from samples 21 to 24 and 39 to 41 show that there is a broad range of halide ion concentrations that produce high but not maximum yield. Maximum yield of copolymer can be

obtained only when a specific concentration ratio exists betwe chloride ion, hydroperoxide, and lignin.

The data of reactions 25 to 39 show that virtuall any combination of lignin and styrene can be grafted togethe to give a copolymer. The copolymer ^! s lignin content can thu be varied between 0 and 100 weight percent to give any particula lignin content desired.

The yields of reactions 33 to 38 are altered by th amount of base added to the reaction mixture. As the pH of th reaction mixture increases, the yield of the product goes down

Samples 30 to 32 were run to test the effects o changing the sequence of additions in the reaction, alterin the time between additions, and duration of nitrogen saturatio in the reaction mixture. None of these procedural changes ha any significant effect on the reaction or its yield. Thus, thi is a very versatile and flexible means to modify lignin.

Most of the examples of Table 7 were terminated b opening the reaction vessel to air.

Example 48 A total of 6.02 of calcium chloride were placed in

250 mL conical flask containing 40.04 g of dimethylsulfoxide The mixture was stirred on a magnetic stirrer for several hour to dissolve the CaCl2 in the solvent. The uniform solution when formed, had a temperature of over 35°C. The sample wa

stirred and bubbled with nitrogen (N2) for about 10 minute before 8.0 mL of 30 percent, aqueous hydrogen peroxide fro Fisher Chemical Company were added to the reaction mixtur followed by 9.39 g of 1-phenylethene. The reaction foamed an spewed out of the reaction vessel, resulting in a zero yield and recovery of product. The reaction was labeled 35-106-1. Yield = 0.0 weight percent.

Example 48 was run as a blank to see how much polymerization would occur in the absence of lignin in the reaction mixture. It shows a potential problem with the reaction process, however. Reaction reagents that are warm when mixed can cause foaming or an explosion. Examples 49, 50 and 51 were run in an altered fashion to avoid the danger of reaction explosion. This altered method is illustrated with the following detailed procedure for Example 49.

Example 49

A sample of 300 g of clarifier sludge from the Masonite Corporation, Hardboard Group, P.O. Box 1048, South 4th Avenue, Laurel, Mississippi 39441-1048 was extracted with aqueous, 2 M NaOH. The dissolved lignin was precipitated in aqueous HC1 and recovered by filtration. A total of 4.00 g of this extracted, hardwood lignin and 3.00 g of calcium chloride were placed in a 250 mL conical flask containing 30.18 g of dimethylsulfoxide. The solution was cooled to 30°C to minimize

the possibility of explosion or foaming. This solution was stir-bubbled with nitrogen (N2- for about 10 minutes before 4.0 mL of 29.86 percent, aqueous hydrogen peroxide were added to the reaction mixture. N2 was bubbled through the reaction mixture and it was stirred for about 5 more minutes. Next, 14.07 g of 1-phenylethene were added to the reaction. This polymerizable material in the reaction contained 22.1 weight percent hardwood lignin. After a short period of stirring and bubbling N2 through the reaction mixture, the flask was stoppered, placed in a 30°C bath for 2 days, and stirred continuously. Within an hour, the unique reactivity of this lignin in this chemistry was evident. The reaction thickened and became turbid. These changes often take 14 or more hours with other lignins. By the end of the reaction, this sample was a thick, viscous, opaque, dark brown slurry. The reaction was then terminated by adding 7 mL of 1% hydroquinone thereto. The reaction mixture was poured into 1.0 L of water and precipitated. The reaction product from the precipitation was recovered by filtration and found to weigh 17.11 g. The product was labeled 35-127-1. Yield = 94.69 weight percent.

More reactions with the base-extracted, hardwood lignin are listed in Table 8.

TABLE 8 ^C ~po.it,-- _„_ __ _{βld of Re} - _{ction MlχturM on Barawd}

Composition _(q) *

Example Hardwood Number 1 -Phenyl Lignin ethene H ₂ 0

CaCl2 (mL) Yield

49 Solvent Notebook

4.00 <g> / (wt.%)

14.07 Number

3.00 4.0

50 30.18

4.01 17.11 / 94.69

9.38 35-127-1

3.02 4.0

51 30.00

4.05 12-33 / 92.08

4.69 35-127-2

3.00 4.0

52 30.07 ⁷ -53 / 86.16 23.25 35-127-3

6.0 8.0 40.0

4-97 / 21.38 35-124-1

By the end of the 48 hour reaction period, sample 35-127-1, example 49, was a thick, viscous, opaque, dark brown slurry. Sample 35-127-2, example 50, was a very thick, non-stirrable, opaque, yellow-brown slurry. To keep the reaction mixed and reacting effectively, it was occasionally taken from the bath and swirled until uniform during the last 24 hours of the reaction. Sample 35-127- 3, example 51, was bubbly, almost solidified, non- stirrable, opaque, pale yellow-brown slurry. Example 51 was also occasionally taken from the bath and swirled until uniform during the last 24 hours of the reaction. The rapid and extensive thickening of examples 49 to 51 display the high reactivity of base-extracted, HCl-precipated, hardwood lignin. Comparing the results of examples 49, 50 and 51 to those of example 48 also shows the benefit of cooling the components of the reaction mixture to below 30°C before combining them. There was no foaming nor an explosion. The cool lignin solution may fail to exothermically decompose the hydroperoxide, thus avoiding a self- propagatiπg process of decomposition, heating and decomposition that can result in a spontaneous expulsion of the reactor contents from the reaction vessel, as occurred in example 48. Pre-reaction cooling thus not only promotes high yield, it also increases the safety of

the polymerization process. Example 52 shows that the presence of lignin is critical to forming graft copolymer. In example 52, a yield of only 21.38 weight percent of polymerizable monomer as poly(l-phenylethylene) homopolymer is produced when lignin is not added to the reaction mixture. The absence of backbone sharply reduces yield in the reaction and shows that lignin is apparently critical to the initiation of the reaction. This reaction was run by the procedure of example 49 and started at a temperature of 30°C, reaching a temperature of 45°C when peroxide was added.

More reactions with the Kraft, pine lignin are listed in Table 9.

TABLE 9 Co-position and *i. _{ld o£} ^^ ^ ^ ^ ^ ^^

Example number θolvønt Yield Notebook ^(q) / <w _τ *F

53 —.W.. Mumber

28.10 6.00 8.0 40.14 33.02/91.47

54 35-120-1 ^β .02/30.0 18.69 6.00 8.0 40.24 23.25/87.05

55 35-120-2

8.05/46.0 9.34 6.00 8.0 40.05

JO 15.53/89.30

56 35-120-3

8.07/80.0 2.00 6.07 8.0 40.37 8.73/86.69

57 35-129-2

8.03/88.9 1.00 6.00 8.0 40.20 7.81/86.5 35-129-3

The data and the examples of Table 9 show that this chemistry allows mixtures of all mass ratios or mole ratios of lignin to monomer, to be graft copolymerized at high yield. This process therefore makes unique materials that can not be obtained by any other method of grafting. To obtain high purity research samples, some further purification steps are used. The original solid precipitated upon terminating the reaction is labeled ⁽ sample number A) and is extracted with benzene for 48

10 hours. The benzene-soluble material is recovered by evaporating the benzene and thematerial is labeled fraction BenEx. The solids not dissolved in benzene are labeled fraction B and is washed with 0.5 M sodium hydroxide. This solution is filtered and the filtrate is dialyzed against

J.-3 water for 3 to 5 days using dialysis tubing. The solid, filtered from the base, is dried and labeled fraction C. The diluted solution is then dried or freeze dried to recover product fraction D. This process converts the original sample, (sample numberA), to four different 0 fractions: ⁽ sample numberBenEx) , (sample numberB) , (sample numberC ⁾ , and (sample numberD) .

None of these fractions are pure. Fraction BenEx, the benzene-soluble part of the product, contains styrene homopolymer (poly(l-phenylethylene) and the graft 5 copolymer that has long 1-phenylethylene chains on it.

Product C contains graft copolymer with medium-sized 1- phenylethylene chains on it. Product D is unreacted lignin and graft copolymer with tiny 1-phenylethylene chains on it. These fractions and kraft pine lignin were tested for chemical composition by Fourier transform infrared spectroscopy. Lignin showed a small absorbence peak at 14.66 micrometers wavelength with an intensity of 54 milliabsorbence units. Poly(1-phenylethylene) shows a strong absorbence peak at 14.29 micrometers wavelength. The absorbence peaks, while proximate, are distinct and allow the materials to be distinguished. The next measurements were made on sample 35-102-3, example 35 of Table 7. Example 35 showed a tall absorbence peak at 14.35 micrometers wavelength with an intensity of over 300 milliabsorbence units. Example 35 fraction B, showed a small absorbence peak at 14.19 micrometers wavelength with an intensity of 64 milliabsorbence units. Example 35 fraction BenEx, showed a tall absorbence peak at 14.35 micrometers wavelength with an intensity of over 400 milliabsorbence units. Further tests were made on sample 35-136-2 and 35-136-3, examples 16 and 17 of Table 7. Example 16 fraction C, showed a strong absorbence peak at 14.22 micrometers wavelength with an intensity of over 150 milliabsorbence units. Example 17 fraction D, showed a small absorbence peak at 14.27 micrometers wavelength with

an intensity of 40 milliabsorbence units. The infrared spectroscopy results show that the two components of the reaction product, lignin and 1-phenylethylene, are distributed throughout the product's fractions and must be chemically bound.

Further tests were run on previously synthesized samples of poly(lignin-gd-phenylethylene) ) to observe and display its thermoplastic properties. A sample of the graft copolymer was placed between two teflon sheets and the assemblage placed on top of a hot plate and weighed down with a second hot plate. The lower hot plate was already heated to 167 +/- 2°C and the upper hot plate was already heated to 164 +/- 2°C. The copolymer samples were kept between the hot plates for 40 to 60 seconds and then the assemblage was allowed to cool. Compression was 1 to 1.5 metric tons. Upon opening the enveloping teflon plates, a hard, brittle sheet was found to have been compression cast from the powdered copolymer. The sheets were clear to opaque, brown plastics with a thickness of approximately 0.5 to 1 mm. The physical properties of the sheet and its color varied according to which copolymer had been chosen for compression casting. All were dark brown and were a darker brown than the powder taken to cast the sheet. The copolymers cast were checked for color and brittleness. The results of the tests are summarized in Table 10.

TABLE 10 Experiments la .forming Plastic Mime from Copolymer

^β ample

⁽ Example) Lignin

Number in Reaction in Original Brlttlsneββ and Mixture Product Yisld Darknsββ of (Weight l» Plaatlc Films

1-134-4 100. 100.

35-105-3Λ. 1) Maximum

46.0 50.41 91.37

35-110-3λ(58) Great but Decreasing

30.0 32.17 93.09

35-l30-3λ(59) Large but Decreasing

22.1 27.32 81.11

10 35-lll-lA(28) Msdium but Decreasin

9.68 10.30 93.98

Polyd-phenyl Lower and Decreasing

0.0 •thylønø) 0.0

Leaat

The pure lignin sample was the material used as a reagent in a number of the grafting reactions previously described. Poly(1-phenylethylene) was a commercial product supplied by the manufacturer and used as a comparison material. Examination of the films by eye and twisting the films to break them were used to rank the materials for tint and stiffness. The results clearly show that the lignin graft copolymer is a more ductile and thermoplastic material than the starting lignin.

In the following examples, the compound 2-propene nitrile, trivial name acrylonitrile, was obtained from the Eastman Division of Kodak, Rochester, New York 14650. The 2-propene nitrile was purified by distillation to remove the stabilizer. It was distilled under vacuum at 35 to 40°C. The central cut was collected in dark bottles and stored in a freezer.

2-Propene Nitrile CH ₂ =CH

C=N

Example 60

A total of 4.10 g of kraft pine lignin and 3.05 g of calcium chloride were placed in a 125 mL conical flask

containing 20.04 g of dimethylsulfoxide. This was labeled solution A. Next, a total of more than 9.35 g of 2-propene nitrile were placed in a vial nested in dry ice. This was labeled solution B. Solution A was stir-bubbled with nitrogen ( 2) for about 30 minutes before 4.0 mL of 29.86 percent, aqueous hydrogen peroxide were added to the reaction mixture. 2 was bubbled through the reaction mixture (A) and it was stirred for about 3 more minutes. A total of 9.35 g of solution B was then added to solution A, the mixture was stirred and bubbled with N2 for 3 minutes, the flask was stoppered, and was placed in a 29°C bath for 2 days. The reaction was stirred continuously while in the bath until it solidified. The reaction was then terminated by adding 2 mL of 1% hydroquinone thereto. The reaction mixture was a solid block. It was broken in half and each half was dissolved in either 200 g of DMSO or 200 g of dimethylformamide. The solutions were then added dropwise to 3 L of water to precipitate and purify the copolymer. The slurries were centrifuged at 5,000 rpm for 45 minutes to separate the solids and the pelleted solids were placed in drying dishes in a vacuum oven to remove the last traces of solvent. The sample recovered from DMSO was labeled 26-77-1 and that recovered from dimethylformamide was labeled 26-77-2. The amount of solid recovered was 26-77-1 = 7.95 g and 26-77-2 = 5.91 g. Total

solid is the yield of reaction 26-74-2 and is 13.86 g of material or (13.86/13.45)* 100 = 103.04 weight percent of reactable solids in the original mixture. Yield = 103.04 weight percent. The higher than quantitative yield in the first reaction of this series may be due to: 1) contamination of the product with traces of solvent; 2) contamination of the product with traces of calcium chloride; or 3) contamination of the product with small amounts of polyvinyl chloride (Saran Wrap) which was used to cover the product solutions before theywere precipitated. When the solutions were prepared for precipitation, the wrap was found to have partially dissolved in the solvents, particularly in the dimethylformamide. For later examples of this chemistry, clear wrap was not allowed in contact with the copolymer solutions. Further, once the solid was separated from the aqueous precipitation solution, the solid was redispersed in pure water and washed before being centrifuged again to recover the copolymer. A series of copolymers were made by the procedures of examples 1 to 5 and are listed in Table 11. These data show that increasing the amount of 2-propene nitrile in the unstirred reaction mixture sharply reduces the yield of the reaction. Further study showed that yield could be made quantitative by using the mixed reaction procedure

of example 60. A series of copolymers made by the mixed reaction procedure of example 60 are listed in Table 12. These data clearly show that the synthesis procedure with continuous mixing produces much higher yield and more efficient polymerization.

TABLE 11 ***ctio ^ββ t ftorm αrsft Copoly_aer*

Polymer _ Reaganta Number Kraϊt

Pine

Lignin 2-Propene Yield -nltrllø 2-Propen

Psrcsnt -smldø in Grama

19-145-9(61) 0.50 0.35 4.17 4.82 l9-14 ^β - ^β (62) 0.50 0.78 0 3.74 4.91 19-147-7(63) 0.50 1.19 3.33 19-150-8(64) 3.50

0.50 0.79 3.75 3.28

TABLB 12 Composition and Yield of Copolymer Reaction Mixtures

Com oaition ( )

Yield (q)/(wt. %)

13.86/103.0 9.83/ 98.0 6.34/ 88.30

10.14/ 99.71

10 9.29/ 94.29

In the following examples, the compound 2-methyl- 1,3-butadiene_78-79-5] , trivial name isoprene, was obtained from the Aldrich Chemical Company as product number 1-9,551-1. The 2-methyl-l,3-butadiene was purified by washing with base and distillation to remove the stabilizer. A 100 mL sample of the monomer was washed in sequence with two 10 mL aliquotes of 0.1 molar, sodium hydroxide. It was then distilled under vacuum at room temperature, approximately 24°C. The central cut was collected in a round bottom flask and stored in a freezer.

2-Methyl-l,3-Butadiene

CH ₂ =C-CH ₃

I CH=CH ₂

Example 70

A total of 4.11 g of kraft pine lignin and 3.02 g of calcium chloride were placed in a 125 mL conical flask containing 20.29 g of dimethylsulfoxide. This was labeled solution A. Next, a total of more than 9.32 g of 2-methyl- 1,3-butadiene were placed in a vial nested in dry ice. This was labeled solution B. Solution A was stir-bubbled with nitrogen (N ₂ ) for about 14 minutes before 4.0 mL of 29.86 percent, aqueous hydrogen peroxide were added to the reaction mixture. N ₂ was bubbled through the reaction

mixture (A) and it was stirred for about 6 more minutes. A total of 9.32 g of solution B was then added to solution A, the mixture was stirred and bubbled with N2 for 3 minutes, the flask was stoppered, and was placed in a 29°C bath for 2 days. The reaction was stirred continuously while in the bath and quickly became a "foamy", emulsion¬ like mixture. The reaction was then terminated by adding 2 mL of 1% hydroquinone thereto. The reaction mixture was a fluid solution. The solution was added dropwise to 200 mL of 2 M, aqueous hydrochloric acid to precipitate and purify the copolymer. The slurries were centrifuged at 5,000 rpm for 45 minutes to separate the solids and the pelleted solids were washed and recentrifuged to purify the product. A water slurry of the pelleted solids was placed on a freeze dryer to remove the last traces of water. The solid recovered was labeled 26-71-2. The amount of solid recovered was 4.21 g. The yield of reaction 26-71-2 is (4.21/13.43)* 100 - 31.27 weight percent of reactable solids in the original mixture.

Examples 71-72

A series of copolymers were made by the mixed reaction procedure of example 70 and are listed in Table 13.

TABLE 13 Composition and Yield of Copolymer Reaction Mixtures

Reaction Composition (g) Number 2-methyl-l,3-

Lignin Butadien CaCl- Yield

26-71-2(70) 4.11 ⁽ q ⁾ /(

9.32 3.02

26-71-3(71) 4.01 4.21/3

3.14 3.05

26-71-4(72) 3.98 4.39/6

6.27 3.07

3.71/3

These data clearly show that numerous, different graft copolymers can be made by conducting this reaction with lignin and monomers that react by free radical polymerization.

Example 73

The compound may be made from lignin extracted by almost any method from virtually any plant; 1- chloroethene; and possibly, 2-propenamide. The structure of the last two compounds is:

CH ₂ =CHC1

and

CH ₂ =CH

C=0

H2.

These components can be polymerized in any one of a series of solvents by dissolving lignin and any of a series of chloride-containing salts, with calcium chloride the preferred salt, in the solvent. Typical solvents are dimethylsulfoxide, dimethylformamide, 1,4- dioxacyclohexane, and a 50/50 by volume mixture of water and dimethylsulfoxide. Other solvents can be used. The

polymerization is initiated by adding hydrogen peroxide to the lignin-chloride solution. A condensation of 1- chloroethene and possibly, 2-propenamide in solvent is added to the lignin solution and the reaction is allowed to proceed for 48 hours with vigorous stirring. The gaseous monomer may be added by bubbling. The polymer is recovered by precipitation in nonsolvent. The structure of the product is:

Lignin-(-CH2"CH) _n -

I Cl

or, with 2-propenamide in the reaction,

Lignin-(-CH ₂ -CH) _n -(CH ₂ -CH) _m -

I I

Cl C=0

\

NH2-

Different bondings through the 1-chloroethene monomer unit are possible ( syndiotactic , isotactic , etc . ) .

Example 74

The method of Example 73 is used except that the compound is made from lignin extracted by almost any method from virtually any plant; ethene; and possibly, 2- propenamide. The structure of the last two compounds is:

CH2=CH ₂

and

CH2=CH

I C=0

I

NH ₂ .

The structure of the product is:

Lignin- ⁽ -CH2- ⁾ n

or, with 2-propenamide in the reaction,

Lignin-(CH2) _n -(CH2- H)----

I C=0

\

NH ₂ -

Example 75

The method of Example 73 is used except that the compound is made from lignin extracted by almost any method from virtually any plant; perfluoroethene; and possibly, 2-propenamide. The structure of the last two compounds is:

CF ₂ =CF ₂

and

CH2=CH

I C=0

I

NH ₂ .

The structure of the product is:

Lignin- ⁽ -CF2- ⁾ _n

or, with 2-propenamide in the reaction,

Lignin- ⁽ CF2 ⁾ _n - ^(CH 2- ^{CH }} m-

C=0 \ NH2-

Example 76

The method of Example 70 is used except that the compound is made from lignin extracted by almost any method from virtually any plant; 2-chloro-l,3-butadiene; and possibly, 2-propenamide. The structure of the last two compounds is:

CH2=CC1-CH=CH2

and

CH ₂ =CH

C=0

NH ₂ .

The polymer is recovered by precipitation in nonsolvent. The compound produced by this reaction will be 1)

Poly(lignin-g-(2-chlorobut-l,4-diyl-2-ene) or any of the structural enantomers of the free-radical polymerization of 2-chloro-l,3-butadiene) or 2) Poly(lignin-g-( (1- amidoethylene)-co-(2-chlorobut-l,4-diyl-2-ene) or any of the structural enantomers of the free-radical polymerization of 2-chloro-l,3-butadiene) ) . The structure of the product is:

Lignin-(-CH ₂ -CC1=CH-CH ₂ -) _n -

or with 2-propenamide in the reaction,

Lignin-(-CH2-CC1=CH-CH ₂ -) _n -(CH ₂ -CH) _m -

C=0

\ NH ₂

Different bondings through the 2-chloro-l,3-butadiene monomer unit are possible such as 1,2-ylene bonding.

Example 77

The method of Example 73 is used except that the compound is made from lignin extracted from almost any method from virtually any plant; dichloroethene; and

possibly, 2-propenamide. The structure of the last two compounds is:

CH2=CC1 ₂ or CHC1=CHC1

and

CH2=CH

C=0

I

NH ₂ .

One structure of the product is:

Lignin-(-CH2-CCI2) _n ~

or, with 2-propenamide in the reaction,

Lignin-(-CC1H-CC1H) _n -(CH ₂ -CH) _m -

C=0 \ NH ₂ .

Different bondings through the dichloroethene monomer unit are possible (syndiotactic, isotactic- head-to-tail, etc. ) .

Example 78

The method of Example 73 is used except that the compound is made from lignin extracted by almost any method from virtually any plant; 1-propene; and possibly, 2- propenamide. The structure of the last two compounds is:

CH2=CHCH ₃

and

CH ₂ =CH

I C=0

I

NH ₂ .

The structure of the product is:

Lignin- ( -CH ₂ -CH- ) _n -

I CH3

or, with 2-propenamide in the reaction,

Lignin-(-CH2~CH-) _n -(CH ₂ -CH) _m -

I I

CH3 C=0

\

NH ₂ .

Different bondings through the 1-propene monomer unit are possible (syndiotactic, isotactic, etc.).

Example 79

The method of Example 70 is used except that the compound is made from lignin extracted by almost any method from virtually any plant; 1-phenylethene; and 2-propene nitrile. The structure of the last two compounds is:

-.•Phenylethene

and

CH ₂ =CH

I

C= N

2-Propene Nitrite

The structure of the product is illustrated by the following reactions:

Lignin + Redox Complex Lignin ^u Reduced Complex

Lignin ^■ n Lignin

Lignin " + n CHjsCH Lignin — (-CH ₂ -CH-) _f

CsN C≡N

Different bondings through the 1-phenylethene and 2-propene nitrile monomer units are possible. In particular, the side chain is often a random copolymer.

Example 80

The method of Example 70 is used except that the compound was made from lignin extracted by almost any method from virtually any plant; 2-propenoic acid; and possibly, 2-propenamide. The structure of the last two compounds is:

CH ₂ =CH-C=0

I

OH

and

CH2=CH

I c=o

I

NH ₂ .

The structure of the product is:

Lignin-(CH ₂ -CH) _n -

I c=o

OH

or, with 2-propenamide in the reaction,

Lignin-(-CH ₂ -CH-) _n -(CH ₂ -CH) _m -

I I

C=0 C=0

I \

OH H2-

Different bondings through the 2-propenoic acid monomer unit are possible.

Example 81

The method of Example 70 is used except that the compound is made from lignin extracted by almost any method from virtually any plant; 4-methyl-2-oxy-3-oxopent-4-ene; and possibly, 2-propenamide. The structure of the last two compounds is:

CH3

I CH ₂ =C-C=0

OCH3

and

CH ₂ =CH

C=0

NH ₂ .

The structure of the product is:

CH ₃

I

Lignin-(-CH ₂ -C-) _n -

C=0

I 0CH3

or, with 2-propenamide in the reaction,

CH ₃

I Lignin-(-CH -C-) _n -(CH ₂ -CH) _m -

I I

C=0 C=0

I \

OCH3 NH2-

Different bondings through the 4-methyl-2-oxy-3-oxopent-4-ene monomer unit are possible.

Example 82 The method of Example 70 is used except that the compound is made from lignin extracted by almost any method from virtually any plant; 2-oxy-3-oxopent-4-ene; and possibly, 2-propenamide. The structure of the last two compounds is:

CH ₂ =CH-C=0

OCH3

and

CH2=CH

I C=0

I

NH ₂ .

The structure of the product is:

Lignin-(CH ₂ -CH-) _n -

I c=o

I 0CH3

or, with 2-propenamide in the reaction,

Lignin-(-CH ₂ -CH-) _n -(CH ₂ -CH) _m -

I I

C=0 C=0

I \

OCH3 NH ₂ .

Different bondings through the 2-oxy-3-oxopent-4-ene monomer unit are possible (heat to tail, etc.).

Example 83

The method of Example 70 is used except that the compound is made from lignin extracted by almost any method from virtually any plant; 2-oxo-3-oxypent-4-ene; and possibly, 2-propenamide. The structure of the last two compounds is:

CH ₂ =CH-0-C=0

I CH ₃

and

CH2=CH

I

C=0

I

NH ₂ .

The structure of the product is:

Lignin-(-CH ₂ -CH-) _n -

I o

I c=o

I

CH ₃

or, with 2-propenamide in the reaction,

Lignin-(-CH ₂ -CH-) _n -(CH ₂ -CH) _m -

I I

0 c=o

1 \

C=0 NH ₂ .

I CH3

Different bondings through the 2-oxo-3-oxypent-4-ene monomer unit are possible (syndiotactic, isotactic, etc.).

Example 84

The method of Example 70 is used except that the compound is made from lignin extracted by almost any method from virtually any plant; 2-methyl-2-propenoic acid; and possibly, 2-propenamide. The structure of the last two compounds is:

CH3

I

CH2=C-C=0

I

OH

and

CH ₂ =CH

I c=o

I

NH ₂ .

The structure of the product is:

CH3

I

Lignin-(-CH ₂ -C-) _n -

C=0

I

OH

or, with 2-propenamide in the reaction,

CH ₃

I

Lignin-(-CH ₂ -C-) _n -(CH ₂ -CH) _m -

I I

C=0 C=0

I \

OH NH2.

Different bondings through the 2-methyl-2-propenoic acid monomer unit are possible.

Example 85

A total of 0.50 g of lignin and 0.63 g of calcium chloride were placed in a 125 mL erlenmeyer flask containing 11.28 g of dimethylsulfoxide and were dissolved. The mixture was stir-bubbled with nitrogen (N ₂ ) for about 2 minutes before 0.482 mL of hydrogen peroxide were added to the reaction mixture. N2 was bubbled through the reaction mixture for about 2 more minutes, the system was stirred for about 3 minutes, and 4.52 g of 2N-methyl-2-imino-3-oxopent-4-ene (I) was added. After about 4 minutes of stirring and bubbling N2 through the reaction mixture, the flask was stoppered. It was then placed in a 28°C bath for 2 days. The reaction was then terminated by adding 0.5 mL of 1% hydroquinone and 100 mL of water thereto. The solution remained single phase during this dilution and smelled sweet. The dilute solution was placed in a dialysis tubing and dialyzed against water for 3 days. The dilute reaction product in the dialysis tube was centrifuged at 5000 rpm for 40 minutes in a Sorvall centrifuge using a GSA head. The solids in the supernate were recovered by freeze drying and found to weigh 1.92 g. The product was labeled 26-16-1. Yield = 38.24 weight percent.

The soluble or crosslinked lignin graft copolymers of the present invention can also be used advantageously in a conventional manner for cleaning, fire fighting, riot suppression, or enhanced recovery of oil in subterranean wells. Typically, in such processes, the graft copolymer is dispersed or solubilized in water and the aqueous solution may then be

bubbled, aerated, sparged, or screened to make foam. In enhanced oil recovery, water is often injected into the subterranean formation, and the injected water is then moved through the formation acting as a hydraulic ram, thereby pushing the resident oil to a production well. However, the particular chemistry of this material makes a much more economical method of oil production possible. If the oil is pushed to a prodcution well by an air-aqueous foam, the cost of the pushing agent is much lower and the oil is recovered at much lower cost. These complex copolymers are particularly suited to forming such a foam, as shown by the following example.

Example 86

A glass column, 1.22 meters tall and 2.8 cm in internal diameter, was mounted vertically with a single hole, rubber stopper in the bottom of the column. The single hole of the rubber stopper was sealed with a glass capillary through which nitrogen gas could be introduced to the column. Nitrogen was bubbled into the column at a rate of 32.9 mL of dry gas per second, measured at 24°C and 1 atmosphere pressure. A 0.24 gram sample of the product of example 85 was introduced into 49.92 g of distilled water and dissolved by rapid stirring. The concentration of active agent in the solution was 4785 parts per million. This solution, when introduced into the column apparatus described above made a 6.9 cm high block of fluid

above the nitrogen inlet at the bottom of the column. In 60.4 seconds of bubbling, the fluid had produced stable foam bubbles which had risen up the column to a total height of 86.5 cm abovethe surface of the fluid in the column. Within 2 minutes, foam had reached 1.15 cm above the surface of the liquid, the column was then cleaned and filled with water. In 60 seconds of bubbling, the distilled water had produced foam bubbles which had risen up the column to a total height of 2 cm above the surface of the fluid in the column. The addition of 0.48 weight percent copolymer to the water had increased its capacity to form bubbles, useful in foam flooding of an oil-bearing formation, 43 fold. It is noted that the particular amounts and composition of the present lignin graft copolymer effective for such use as well as other particulars of this use would be within the gambit of one skilled in the art having read the present disclosure.

As already noted, the grafted side chain or chains are made of randomunits of 2-propenamide and 2N-methyl-2-imino- 3-oxopent-4-ene. Moreover, the actual content of the grafted side chain or chains depends upon the molar ratio of monomer reactants employed. According to the present invention, it is acceptable to use from about 0.00 molar percent to 99 molar percent of 2-propenamide to about 100 molar percent to 1 molar percent of 2N-methyl-2-imino-3-oxopent-4-ene. However, it is preferable to use a molar percent in the range determined by

the application. Better foaming agents will be made with 100 mole percent 2N-methyl-2-imino-3-oxopent-4-ene in the product if the molecular weight is kept low. Higher molecular weight and more water soluble materials can be made by increasing the mole fraction of 2-propenamide in the reaction mixture. The grafted side chain or chains appear to attach at one or more of the 2-, 5- or 6-aromatic ring positions on the oxyphenylpropene moiety. Of course the precise content of the grafted side chain or chains depends upon the comtemplated use. For example, in uses where water solubility is required, more of the 2- propenamide monomer should be used. Conversely, where water soluble character is less desired, more of the 2N-methyl-2- imino-3-oxopent-4-ene monomer should be used.

The lignin-containing-material upon which grafting takes place can be any substance of which lignin is a part, with wood being the most common example. In view of the complex nature of wood and the number of compounds that can obstruct a free-radical reaction, it is amazing but now proven that this chemistry will graft contiguous wood as well as free, extracted lignin. The data of Table 14 show that the polymerization occurs when wood is used as the lignjn-containing-material but does not occur when cotton; a lignin-free, cellulose-based, plant product; is used in the reaction. Further, extraction with benzene for between 2 and 4.25 days shows that the wood has undergone a permanent, 50 to 375 weight percent gain in

mass due to grafted sidechains being attached to the wood. These reaction were all stirred at rate of 4Hz.

Table 14: Co ol merixation Reactions of Li nln-Containln -Materials and l-Phen leth lene

10

* Example Numbers in parentheses. This is the reaction on Degreased Cotton. Only cotton recovered.

The previous examples and discussion have shown that reactions conducted with hydreohobic monomers will not produce grafting unless the reaction is continuously stirred. Further, the rate of stirring depends on the monomer being reacted with the lignin-containing-material. The rate of stirring which produces grafting and allows high yield of graft copolymer must be determined from the monomer's dipole moment and its solubility in water. The symbol for dipole moment is u and the property is expressed in units of debye, abbreviated as a "D". The dipole moment of a molecule is the distance in centimeters between separated accumulations of positive and negative charge times the magnitude of one of the accumulations of charge, expressed in electostatic units. These charge separations are structural features of a molecule caused by its atomic structure and are therefore characteristic of the molecule. The dipole moments and solubility limits of a group common monomers are given in Table 15. Those monomers that have a solubility in water at 30°C of more that 200g of monomer per lOOg of water and a dipole moment of more than 1.2, need not be stirred to produce graft copolymer. Those monomers that have a solubility less than 5g of monomer per lOOg of water at 30°C and a dipole moment of less than 1.8, must be stirred to produce graft copolymer

from the grafting reaction. The rate of stirring is determined by the dipole moment is expressed in debye units, D, where 1 D = 3.33564 X 10~ ³⁰ coulomb-meter. Note that there is no contradiction betewwn the solubility- dipole moment limits just propounded. The monomer must simultaneously have a solubility of less than 5g of monomer per lOOg of water at 30°C and a dipole moment of less than 1.8, must be stirred to produce graft copolymer from the grafting reaction. If the absolute value of the stirring rate of the solution in Hz is labeled |x| and related to the dipole moment of the monomer, a quadratic equation is produced that acts as guide for the design of a reaction. The equation relating absolute value of stirring rate to dipole moment is a|x| ² + b|x| + c = u, where a = 0.024719 D/Hz ² ,b = '-0.3516 D/HZ, and c = 1.381 D. Stirring rate is actually controlling "tip speed" of the stirring bar. "Tip speed" is the velocity of the ends of the stir bar or paddle in the reaction tank. This "tip speed" is a critical variable in mixing. Shear rate is approximately 12 times stirring rate in Hz. Shear stress is equal to viscosity times shear rate and shear stress is the fundamental value controlling the mechanochemistry of phase stability and mixing in the reaction. Thus, bar and reactor design will alter the preferred stirring rate for a given reaction in a given reactor.

Table 15: Dipole Moments and Solubility Limits of Some Common Monomers

Solubility

Limit

Monomer Name

1-Bromoethen

1-Chloroethene

1-Fluoroethene

1,3-Butadiene 2-Propenamide

2-Methylprop-2-enoic Acid

3-Oxy-2-oxopent-4-ene

Cyclopentene

Pentyne 2-Methyl-l , 3-butadiene

1, 3-Pentadiene

4-Methyl-2-oxy-3-oxopent-4-ene

1-Phenylethene

# Data from "tables of Experimental Dipole Moments, Aubrey Lester McClellan, W.H. Freeman and Company, San Francisco, (1963)

# Dipole moment calculated from an AMI quantum mechanical calculation on the planar 2-propenamide molecule.

The molecular weight of the lignin copolymers of the present invention are in the range of about 20,000 to about 30,000,000 as determined by size exclusion chromatography using known techniques. Under the process conditions of the present invention already described, it is possible to obtain molecular weights of about 15,000 to 300,000. Under these conditions, the polymer molecular weight is generally increased by increasing the ratio of moles of monomer to moles of hydroperoxide. The converse is true when diminishing the molecular weight. However, by utilizing another aspect of the present invention, it has now been found possible to greatly boost or increase the molecular

weight of the growing polymer during polymerization by conducting the reaction essentially in a gelated state. Preferably, the fraction of amide versus phenyl repeating units ranges from about 0.0 to 99.8 molar percent and the fraction of phenyl versus amide repeating units ranges from 100.0 to 0.2 molar percent.

Generally, the gelated state can be formed by essentially repeating the procedures already described for synthesizing the graft copolymer, but by reducing the amount of dimethylsulfoxide (DMSO) solvent by a factor of 0.25 or more. In other words, instead of using about 30 mL of solvent for the reaction as described in the Examples, about 23 or less mL are used instead. It has been theorized that by conducting the polymerization reaction in the gelated state, the propagation reaction continues, while the termination reaction is greatly diminished. It is also possible that the higher concentration of backbone and repeat units allows crosslinking in these lower- solvent-content reactions. In general, the gelation occurs at room temperature with no heating being necessary. Reaction times are somewhat variable and on the order of from 1 to about 48 hours with reaction yields as high as 80 weight percent possible in about 10 hours.

Although the polymerization reaction of the present invention is a free-radical polymerization, the scope of the present invention clearly extends the concept of gel-state

reactions to other types of polymerization reactions such as anionic or cationic chain polymerization or step polymerizations.

These copolymers can be used to form any plastic or solid object by extrusion, blow molding, sheet casting, or injection molding.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described.