GB2112005A - Quaternary ammonium graft polymers - Google Patents

Abstract

Water-soluble cationic polyquaternary ammonium graft copolymers are prepared by graft polymerizing (a) one or more water-soluble vinyl monomers onto (b) a water-soluble cationic polyquaternary ammonium polymer which contains hydroxyalkylene groups. (a) is typically acrylamide, optionally mixed with acrylic acid, dimethyl diallyl ammonium chloride and/or dimethyl aminoethyl methacrylate methosulphate. (b) contains units of -A-CH2- CH(OH).CH2-A- where A is tertiary or quaternary nitrogen, and is typically the quaternized reaction product of epichlorhydrin with N,N,N',N'- tetramethylethylene diamine and optionally methylamine. The polymers are useful as flocculants, dry strength additives for paper, and retention agents.

Description

SPECIFICATION Quaternary ammonium graft polymers The present invention relates to novel cationic graft copolymers and their uses for example as flocculants, dry strength additives for paper, and dye retention agents. More particularly, the present invention relates to quaternary ammonium graft copolymers prepared by graft polymerizing watersoluble vinyl monomers to quaternary ammonium ionene type polymers. This invention is related to the flocculation of suspended matter by the aforesaid polymers, and to paper of improved strength and dye retention prepared by use of the aforesaid polymers.

A number of methods are known in the art for the preparation of graft copolymers. These include radiation methods, both high energy radiation from gamma rays or electron accelerators and actinic, i.e.

photochemical radiation. Chemical catalysts which are also used include free radical initiator systems such as the ferrous ion-hydrogen peroxide reaction which is very effective in promoting graft polymerization.

The present invention is not limited to any single method for initiation of the polymerization. However, the ceric ion initiation system taught by Mino, et al. (U.S. Patent No, 2,923,768) is particularly attractive. In this method it is believed that ceric ions react directly with a pendant reactive group such as hydroxyl group on the polymeric substrate. The radical which results from this initial reaction then may react with vinyl monomers present in solution yielding a graft copolymer. Relatively little homopolymer is produced by this technique unless large amounts of chain transfer agents are added.

It has now been discovered that certain polyqu-.

aternary ammonium polymers of the ionene type are active substrates for graft polymerizations. Graft polymers produced by ceric ion-catalyzed graft polymerizations onto the aforesaid polyquaternary ammonium polymers are unusually effective as flocculants, dry strength agents for paper, and dye retention agents.

Water-soluble cationic polymers have been used in a number of applications including the pulp and paper industry to increase strength and dye retention, in water treatment to flocculate suspended solids, and in waste treatment to help dewater sludge. New materials which are effective in these applications are constantly being synthesized and evaluated, and materials with improved properties would be accepted readily.

The present invention provides water-soluble high-molecular-weight qaternary ammonium graft copolymers comprising a substrate portion and a graft portion. The substrate portion is derived from a water-soluble polymeric quaternary ammonium composition having a plurality of hydroxypropylene groups having the structure

wherein A is a tertiary or quaternary nitrogen, and in which the number of quaternary nitrogen atoms exceeds the number of tertiary nitrogen atoms. The graft portion is derived from a polymeric composition comprising polymerized water-soluble nonionic, anionic and/or cationic vinyl addition monomers. The amount of grafted vinyl addition polymer can vary between one-tenth and one hundred times the amount of substrate polyquaternary ammonium polymer.

The above-described graft copolymers may be used to flocculate suspended inorganic and organic matter in aqueous solutions and may thus be useful for flocculating impurities in water and in processing wastes. They can also be used for dewatering sewage sludge.

Furthermore, the copolymers of the invention may be useful in improving drainage and retention, e.g.

of fines, dyes, pigments, fillers and starch in the manufacture of paper and may thus be used to increase strength, improve sizing and increase the electroconductivity of paper and paperboard.

The present invention further provides a process for the preparation of a graft copolymer as decined above which comprises reacting a water-soluble polymeric quaternary ammonium composition as defined in claim 1 with one or more water-soluble nonionic, anionic or cationic vinyl addition monomers, in the presence of a polymerisation catalyst.

The graft copolymers of the present invention comprise a substrate portion, i.e., a previously made polymer, and a grafted portion. The substrate polymer is a cationic polyquaternary ammonium polymer of the ionen type. In general, these substrate polymers are made by the reaction of a ditertiary amine with epichlorohydrin. A convenient method to produce cationic polyquaternary ammonium polymers suitable for use in this invention is that described by Buckman, et al. in U.S. Patent 4,054,542. Complete descriptions concerning the details of the reactant species as well as the methods of preparation are contained therein. These polymers have a molecular weight of approximately 40,000.

In addition to the polymers described above, other polymers described by Buckman, et al. in U.S. Patent 4,018,592 can be utilized. These polymer molecules have molecular weights in the range of 5,000.

A polyquaternary ammonium polymer may be distinguished from a polyamine by the functionality of the nitrogen atoms in the polymer. In a polyquaternary ammonium polymer most of the nitrogens are quaternized, i.e., they are convalently bonded to four carbon atoms. In a poiyamite, most of the nitrogen atoms are not quaternized. Polyamines will have nitrogen atoms which are primary, i.e., they are bonded to one carbon atom and two hydrogen atoms, secondary, i.e., they are bonded to two This print takes account of replacement documents later filed to enable the application to comply with the formal requirements of the Patents Rules 1982.

carbons and one hydrogen, and tertiary, i.e., they are bonded to three carbons. In addition, polyamines may have some nitrogens which are quaternary; but these quaternary nitrogens will comprise considerably less than half of the total number of nitrogen atoms.

A polyquaternary ammonium polymer is made from a ditertiary amine and another difunctional monomer, such as epichlorohydrin. The reaction between the two monomers joins a carbon from the difunctional monomer to a nitrogen on a tertiary nitrogen to product a quaternary nitrogen.

In the process which produces polyamines only a minor amount of reactions occur which lead to quaternary ammonium groups. In general, a polyamine is made from a multifunctional amine, such as diethylene triamine, which will contain some primary and some secondary nitrogens. The polymerization reactions between the multifunction al amines and difunctional monomers, such as epichlorohydrins, will change primary nitrogens to secondary nitrogens and secondary nitrogens to tertiary nitrogens. Inevitably some of the tertiary nitrogens formed from previous reactions will be converted to quaternary groups, but considerably less than half of the nitrogens will be quaternized.

Polyamines may also be made from methylamine and epichlorohydrin, as taught by Nagy in U.S.

Patent 3,567,659. In this process a deliberate attempt is made to reduce the amount of cross-linkages by minimizing the formation of quaternary nitrogens.

The polyamine made by Nagy has the structure

In solutions with an acid pH, these polyamines convert to the cationic form, e.g., the hydrochloride salt.

The structure of a typical polyquaternary ammonium polymer used as a substrate in the present invention has the general formula

where A is a tertiary or quaternary nitrogen atom, and in which the number of quaternary nitrogen atoms always exceeds the number of tertiary nitrogen atoms.

In processes employed to make polyquaternary ammonium polymers, a deliberate attempt is made to have as many nitrogen atoms as possible in the quaternary form. Over fifty percent of the nitrogen atoms in polyquaternary ammonium polymers are quaternary nitrogen atoms.

The grafted portion of the polymers of the present invention is made by the graft polymerization of water-soluble vinyl monomers on the backbone of the substrate. The water-soluble monomers employed in the present process include acrylamide, methacrylamide, acrylic acid, methacrylic acid, dimethylaminoethyl methacrylate, N,N-dimethylacrylamide, dimethylaminopropylmethacrylamide, methacrylamidopropyltrimethylammonium chloride, dimethyldiallylammonium chloride, the quaternization product of dimethylaminoethyl methacrylate with methyl chloride, the quaternization product of dimethylaminoethyl methacrylate with dimethyl sulfate, and other water-soluble monomers which are readily apparent to those skilled in the art.

Mixtures of two or more of the water-soluble vinyl monomers may also be used.

Preferred mixtures include acrylamide with one or more of the other monomers listed above. Most preferred mixtures are acrylamide and acrylic acid, acrylamide and dimethylaminoethyl methacrylate, acrylamide and the quaternization product of dimethylaminoethyl methacrylate with dimethyl sulfate, and acrylamide and the quaternization product of dimethylaminoethyl methacrylate with methyl chloride. Also included are mixtures of three of more monomers, such as acrylamide, acrylic acid, and the quaternization product of dimethylaminoethyl methacrylate with dimethyl sulfate.

The graft polymerization can be initiated in one of several ways. High energy radiation such as gamma rays or electrons accelerators are convenient methods to use in many graft polymerizations.

Likewise, photochemical initiation is a convenient source of radicals which are effective in promoting graft polymerizations.

The preferred method to initiate polymerization to produce the cationic polyquaternary ammonium graft copolymers of the present invention is use of chemical catalysts. The reaction between ferrous ion and hydrogen peroxide is one such preferred catalyst system. Other chemical catalysts are apparent to those skilled in the art.

A much preferred method to initiate these graft polymerizations is by use of ceric salts. It is believed that ceric ion reacts with pendant hydroxyl groups present in the substrate polymer. The hydroxyl groups result from the reaction of epichlorohydrin with a ditertiary amine. The product of this reaction is a polymer containing alternating quaternary ammonium units with hydroxypropylene units.

The radical resulting from the reaction of ceric ion with the hydroxyl groups is reactive toward vinyl monomers. Polymerization then proceeds, adding further vinyl monomers and forming a new polymeric grafted chain one end of which is covalently bonded to the substrate polymer. The result of this graft polymerization is the cationic polyquaternary ammonium graft copolymer of the present invention.

The reaction conditions can be varied over wide limits. The graft copolymers of the present invention can be made under conditions in which the amounts, by weight, of the polyquaternary ammonium polym er (substrate) and the vinyl monomer (graft) are approximately equal. For example, the weight ratio of substrate to vinyl monomer may be in the range of, say, ten to one to one to ten. Graft copolymers with molecule weights up to one million or more are produced by this process.

We have found that even higher molecular weight grafts are produced when the weight ratio of substrate to monomer is substantially lower than one-toten. For example, exceptionally high molecular weight graft copolymers are produced when the ratio of substrate to monomer is about one-to-fifty.

Products made utilizing these ratios of reactants are quite effective flocculants.

If lower molecular weight products are desired, high weight ratios of substrate to monomer are preferred. In addition, as taught by Nagy in U.S.

Patent 3,711,573, isopropanol or other chain transfer agents may be added to the reaction mixture to reduce the molecular weight.

In general, it is desirable to have a final product which has a high polymer solids content. Container costs and shipping costs of low solids content polymer solutions will increase the cost of the product and make it uneconomical even though the polymer properties may be superior. Water-soluble polymers whose molecular weights are about one million or higher yield very viscous aqueous soiutions. The upper limit of polymer content in an aqueous solution of a high molecular weight watersoluble polymer is less than ten percent for molecularweights near one million. Solutions containing higher polymer solids content are too viscous for use in many situations.

In a preferred embodiment of the process for making such high molecular weight graft copolymers while retaining high total polymer solids content, a small weight ratio of substrate polymer to monomer is employed. The total solids (substrate polymer plus monomer) is kept high, greater than ten percent. The reaction is initiated with ceric ion catalyst and polymerization proceeds. To prevent gel formation, as the viscosity begins to build, additional low molecular weight polyquaternary ammonium polymer (substrate) is added. Since the polymer content of the substrate solution can be twenty-five percent or higher, the total polymer solids content in the graft copolymer solution does not decrease.To further control the viscosity of the graft copolymer solution, isopropanol or other chain transfer agents may be added as well, either previous to, at the same time as, or subsequent to the addition of the added polymer substrate solution.

Depending upon the amount of monomer in the initial charge and the amount of polyquaternary ammonium substrate polymer added in the second charge, the final polymer solids content may vary from five to twenty-five percent or higher.

The conditions necessary for efficient graft polymerization are not critical. The pH of the solution should be acidic, in the range of one to four pH units.

The monomer need not be of high purity. For example, acrylamide is often supplied as a fifty percent aqueous solution containing copper ion as a polymerization inhibitor. While some advantage is gained by removal of the copper by ion-exchange in that somewhat higher molecular weights are obtainable, this purification step is not critical or necessary.

Temperature is likewise not a critical parameter.

Good grafting efficiency is obtained at ambient temperatures as well as at higher temperature.

Removal of oxygen from the solution is often employed so that higher molecular weight grafts are obtained, but this is not critical. Adequate polymerization efficiency and molecular weights are obtained when no effort is made to remove oxygen.

it is well recognized in the art that when two or more monomers are copolymerized, different properties are obtained when the relative concentrations of the monomers are different. The same holds true in graft copolymerizations. For certain applications, e.g., sludge dewatering, it has been found that high ratios of a cationic monomer, such as the dimethyl sulfate quaternization product of dimethylaminoethyl methacrylate, to acrylamide will give a product having superior properties. For other applications, e.g. water clarification, best results have been obtained when the grafted portion contains only small amounts of cationic monomer or even when the graft portion is completely non-ionic, i.e. a polyacrylamide graft.

In order to disclose the nature of the present invention still more clearly, the following illustrative examples will be given. It is to be understood, however, that the invention is not to be limited to the specific conditions or details set forth in these examples except insofar as such limitations are specified in the appended claims.

Parts as used herein and in the appended claims are parts by weight.

EXAMPLE 1 This illustrates the preparation of a polyquaternary ammonium polymer which is suitable as the substrate polymer graft polymerizations.

An epichlorohydrin - methylamine prepolymer was prepared by reacting 800 parts of a fifty percent aqueous methylamine solution with 2424 parts of epichlorohydrin. The reaction was carried out at 350C in 600 parts of n- propanol solvent. When the reaction was completed, 272 parts of concentrated sulfuric acid was added.

The polyquaternary ammonium polymer was then prepared by adding 2007 parts of water and 2275 parts of an aqueous solution containing 60 percent N,N,N',N' - tetramethylethylenediamine. The mix ture was heated to 70-75 C until the contents of the vessel became viscous, at which point the reactants were diluted with 7678 parts of water. The mixture was reheated and the reaction continued until the viscosity increased again. The polymerization reac tion was stopped by adding 402 parts of sulfuric acid and 298 parts of water. The final solution contained 25 percent by weight of polymeric solids, Over eighty percent of the nitrogen atoms in this polymer are quaternary nitrogen atoms.

EXAMPLE 2 This example describes a method for the prepara tion of a graft copolymer of the present invention.

Into a one liter glass reaction kettle fitted with an agitator, thermometer, and nitrogen sparge tube was added 250 grams of the polyquaternary ammo nium polymer of Example 1, 100 grams of a 50 percent aqueous acrylamide solution, and 147 grams of deionized water. The solution was agitated and purged with nitrogen to remove dissolved air.

Into this mixture was added three milliliters of a catalyst solution consisting of 0.1 N ceric ammonium nitrate in 1 N nitric acid.

A reaction occurred immediately. The temperature rose and the solution became very viscous in about five minutes. The reaction was allowed to continue for two hours. The resulting solution contained 22.5 percent of the polyquaternary ammonium-acrylamide graft copolymer wherein about 55.6 percent of the graft copolymer arises from the substrate and about 44.4 percent of the graft copolymer is polymerized acrylamide.

EXAMPLE 3 This example describes the preparation of another polyquaternary ammonium polymer which is suitable as a substrate in subsequent graft polymerizations.

The ionene polymer, poly[hydroxyethylene (dimethylimino)ethylene(dimethylimino)methylene dichloride] was prepared by mixing 375 parts of an aqueous solution containing 60 percent of N,N,N',N' - tetramethylethylenediamine (TMEDA) and 4496 parts of muriatic acid (31.5 percent HCI) at a temperature below 50"C. While the temperature was maintained at400-500C by cooling, 3588 parts of epichlorohydrin were added, The mixture was further agitated for one-half hour and then heated to 60 -70 C at which temperature it was maintained while 3750 parts of additional aqueous solution of TMEDA were added. The concentration was adjusted to 60 percent polymer solids by distilling some of the water from the product The molecular weight of the product is about 5,000.All of the nitrogen atoms in this polymer are quaternary nitrogen atoms.

EXAMPLE 4 This illustrates a method for the preparation of graft copolymers using as the substrate the polymer of Example 3.

The general procedure of Example 2 was used except that 313 grams of water, 100 grams of a 50 percent acrylamide solution, and 84 grams of the polyquaternary ammonium polymer of Example 3 were added to the reaction kettle. Three milliliters of ceric catalyst were added and a viscous polymer solution was produced in a few minutes. Twenty-five minutes after the addition of the first three milliliters of catalyst, another three milliliters of catalyst were added. Twenty-five minutes after this second catalyst charge, another three milliliters of ceric catalyst were added. The resulting clear, viscous solution was approximately 20.1 percent polymer by weight wherein approximately half was grafted acrylamide and the remainder came from the substrate polyquaternary ammonium polymer of Exam ple 3.

EXAMPLES 5-11 The general procedure of Example 2 was utilized except that 118.5 grams of water, 7.5 grams of isppropanol, 70 grams of acrylamide, and 250 grams of the polyquaternary polymer of Example 1 were agitated in the reaction flask. In addition to the acrylamide, the water-soluble vinyl addition monomers listed in Table 1 were utilized in separate preparations. In each case, 30 grams of the listed monomers were added. Three milliliters of ceric catalyst were added. In each case the temperature rose, and the solution became viscous, indicating that a graft polymerization occurred. Additional ceric catalyst (three milliliters per each addition) was added. A total of 24 milliliters of catalyst was added to each except for Example 11 where only 12 milliliters were added. In this case, the solution was already extremely viscous.

Table 1 Comonomer Used with Acrylamide Total Example To Form Graft Copolymer Polymer Solids 5 dimethylaminoethylmethacrylate metho- 24.3 sulfate (80% solution) 6 dimethylaminoethylmethacrylate 24.0 methylchloride (75% solution) 7 dimethylaminopropylmethacrylamide 25.5 8 methacrylamidopropyltrimethyl ammonium 22.5 chloride (50% solution) 9 dimethyldiallylammonium chloride 25.5 10 N,N dimethylacrylamide 25.5 ii acrylic acid 26.1 EXAMPLE 12 The procedure of Example 2 was followed with the exception that the ceric catalyst was not used. Into the reaction kettle were added 250 g of the polyquaternary ammonium polymer of Example 1, 100 g of a 50 percent acrylamide solution and 147 g of water.

The pH was adjusted to 3.5 with 50 percent sodium hydroxide.

Two milliliters of 0.35 percent hydrogen peroxide were added to the flask, quickly followed by two milliliters of a solution consisting of 0.1 M ferrous ammonium sulfate in 1 M sulfuric acid. An immediate temperature rise occured, accompanied by an increase in viscosity. The reaction was allowed to continueforfortyminutesafterwhich 7.5 milliliters of ispropanol were added, followed by an additional charge of the catalyst, that is, two milliliters of 0.35 percent hydrogen peroxide and two milliliters of the ferrous solution. During the next two hours two more additions of the catalyst system (ferrous solution and H202) were made. The resulting solution was similar in appearance and composition to the product of Example 2, except that the product of this example contains slightly less polymer solids, 21.6 percent.

EXAMPLE 13 The following example describes the preparation of the polyquaternary ammonium graft copolymer of the present invention utilizing a combination of two catalyst systems.

The same procedure of Example 2 was followed.

Into the reaction kettle was added 250 g of the polymer of Example 1,100 g of a 50 percent acrylamide solution and 147 g of water. Three milliliters of the ceric catalyst were added. The temperature rose and the solution became viscous.

Two hours after the reaction was initiated, 7.5 milliliters of isopropanol were added, followed by two milliliters of 0.35 percent hydrogen peroxide and two milliliters of the ferrous sulfate described in Example 12. A substantial amount of unreacted monomer was present following the first addition of the ceric catalyst since an immediate rise in temperature and a slight increase in viscosity occurred. Two more additions of two milliliters of each of the peroxide and ferrous solutions were made. No obvious reaction occurred following the last catalyst addition. The product of this Example was very similar in appearance and composition to the product of Example 12.

EXAMPLE 14 The following illustrates another method for preparation of the graft copolymers of the present invention.

The general procedure of Example 2 was followed except that two reaction kettles were charged with 100 g of a 50 percent acrylamide solution, 147 g of water and 4 g of the polyquaternary ammonium polymer of Example 1. The ratio of acrylamide to polyquaternary ammonium polymer was, therefore, 50 to 1 on a solids basis. Three milliliters of ceric catalyst solution were added to each kettle. An immediate increase in temperature occurred in each solution, followed by a rapid increase in viscosity.

When the viscosity became so great that the solution to climb the agitator shaft, 250 milliliters of water were added to the first kettle, Solution 14A, and 250 milliliters of the polyquaternary ammonium polymer of Example 1 were added to the second kettle, Solution 14B. The reactions continued as evidenced by a slow climb in temperature and a noticeable increase in viscosity. Two hours after the initial charges of catalyst, an additional 300 milliliters of water were added to Solution 14A. Then to each solution 7.5 milliliters of isopropanol were added, followed by the addition of two milliliters of dilute hydrogen peroxide and two milliliters of the ferrous solution described in Example 12. A second charge of two milliliters of each of the ferrous solution and the peroxide solution was made to each solution.

The resulting solutions were approximately 6.3 percent polymer solids for Solution 14A and 21.8 percent in Solution 14B.

EXAMPLE 15 The polyquaternary ammonium graft polymers of this invention were tested for their effectiveness as flocculants in laboratory jar tests. Fifteen hundred milliliters of a 0.4 percent by weight suspension of Fuller's Earth (Kaolin) were added to each jar and agitated by paddles turning at 100 rpm. Varying quantities of the polymer solution to be tested were added and agitation was continued for one minute after which agitation was stopped and the suspension allowed to settle for five minutes, Observations were made on the flocculation speed, i.e. the settling rate, as well as the final clarity of the supernatant solution after five minutes.

The flocculation speed was judged qualitatively and the polymers were ranked in order of their flocculation speed. The clarity of the test solution was graded on a scale of 0 to 5 (0 means no settling and 5 signifies a clear supernatant layer) after allowing for settling for five minutes.

Table 2 compares the qualities of the graft copolymer prepared in Example 2 with two commercially available products both of which are used to treat water, to remove suspended matter. Commercial product A is 25 percent by weight and commercial product B is 40 percent by weight of polymer solids.

A dilute solution (1500 ppm) of each polymeric product to be tested was first made up. Then 2,4 or 8 milliliters of these dilute polymer solutions were added to the Kaolin suspension. The usage rate of each polymeric dilution product was, therefore,2,4, or 8 ppm. However, since the products differ on a percent solids basis, usage rate on a total polymer solids basis is, of course, different.

Table 2 Clarity Rating at Usage Rate of 2 ppm 4 ppm 8 ppm Product of Example 2 (22.5 percent) 3.1 3.5 4.4 Commercial Product A (25 percent) 3.4 3.8 3.5 Commercial Product B (40 percent) 3.2 3.4 3.3 The product of Example 2 at each usage rate gave the fastest settling rate. it is seen in Table 2 that the two commercial products give good clarity at these usage rates with a maximum effect near 4 ppm. The product of Example 2, in addition to having the fastest settling rates, gives substantially better clarity at somewhat higher usage rates, with no decrease in effectiveness at higher usage rates.

Excellent effectiveness occurs over a wider range in usage rates.

EXAMPLE 16 This illustrates the effectiveness of the polyquater nary ammonium graft copolymers in fiocculating suspended matter when the grafted portion of the polymeric product is a mixture of acrylamide and other water-soluble vinyl addition monomers.

The procedure of Example 15 was followed.

Polymer solutions tested were made from the pro ducts of Example 5 through 10, as well as Example 2.

The results are shown in Table 3 below.

Table 3 Clarity at Example Comonomer Usage Rate of 2ppm ppm 2 Acrylamide alone 3.1 4.0 5 Dimethylaminoethyl 3.4 4.2 methacrylate methosu Ifate 6 Dimethylaminoethyl 3.1 4.0 methacrylate methylchioride 7 Dimethylaminopropyl 2.8 3.7 methacrylamide 8 Methacrylamidiopropyl 2.9 3.8 trimethyl ammonium chloride 9 Dimethyldiallyl 2.8 3.8 ammonium chloride 10 N,N Dimethylacrylamide 2.9 3.9 All of the graft copolymers in the table above show excellent flocculating properties.

EXAMPLE 17 This example illustrates the effectiveness of the graft copolymers of the present invention as flocculants for sewage sludge.

The apparatus consisted of No. 1 Büchner funnel positioned directly over a 250 ml graduated cylinder.

A piece & filter cloth was cut Xo the same dimension as No. 1 filter paper and this filter cloth was placed in the Büchnerfunnel. This filter cloth was of the same type used in sludge dewatering presses.

Five percent dilutions of the polymer solutions to be tested were prepared. For each test 500 milliliters of sewage sludge (3.4 percent solids) were placed in a beaker. The desired amount of dilute polymer solution was placed in a second beaker. The sludge was then poured back and forth between the beakers three times to ensure complete mixing. The resulting mixture was then poured onto the filter cloth in the Büchner funnei.

The solution was allowed to drain by gravity, i.e., no pressure or vacuum was appled. The amount of liquid collected in the graduated cylinder was recorded after 15,30,60 and 120 seconds. The better the sludge dewatering effectiveness of the polymer, the more liquid will be collected at any given time.

Two graft polymers were prepared for testing. The procedure of Example 6 was used to make Solution D. The reaction kettle was charged with 147 g of water, 250 g of the polyquaternary ammonium polymer of Example 1,70 g of a 50 percent acrylamide solution, and 30 g of an 80 percent aqueous solution of dimethylaminoethyl methylacrylatemethosulfate. Ceric catalyst was added nine times in three milliliter increments over the next four hours.

Solution E was prepared in a slightly larger scale.

A two-lite# reaction kettle was charged with 828 g of water, 1000 g of the polyquaternary ammonium polymer of Example 1, 160 g of a 50 percent acrylamide solution and 40 g of isopropanol. Twelve milliliters of ceric catalyst were added.

Table 4 shows the sludge dewatering effectiveness of Solutions D and E compared to the effectiveness of a commercially available cationic polyacrylamide polymer used in sludge dewatering operations.

Table 4 Volume of 5% Solution Polymer Volume in Milliliters Tested Solution Added Collected After Milliliters 15 sec. 30 sec. 60 sec. 120 sec.

Solution D 4 26 38 53 73 6 45 65 78 93 8 60 80 98 116 Solution E 4 27 35 50 65 6 50 65 83 100 8 55 75 93 105 Commercial 4 19 23 31 41 Cationic 6 32 45 60 75 Polyacrylamide 8 52 70 85 101 The table demonstrates that graft copolymers of the present invention are effective in dewatering sewage sludge.

EXAMPLE 18 The polymeric mixtures of Example 15 of this invention were tested for their effectiveness in the retention of total solids in a paper pulp slurry using the method described in Example 15 of U.S. Patent 4,250,269 which disclosure is hereby made a part of this application.

Fractionation of the paper pulp slurry showed that the slurry contained 27 percent fines. Percent fines retention could then be calculated once the total solids retantion and the percent fines in the original slurry were known. Table 5 shows that the polyquaternary ammonium acrylamide graft copolymer of Example 2 is superior to the ungrafted polyquater naryammonium polymer of Example 1, a product which is presently used as a retention aid.

Table 5 Use Rate Percent Product Pounds per Retention Tested Ton of Pulp of Fines Control with no 0 59.6 retention aid Example 1 0.75 65.3 1.50 69.6 2.50 71.5 5.00 71.2 Example 2 0.675 67.3 1.35 69.2 2.25 74.3 4.50 81.8 EXAMPLE 19 This example illustrates the effectiveness of the graft copolymers of the present invention in increas ing the dry strength of paper.

Handsheets were made and tested using a Scott Internal Bond Tester. Three hundred grams of a 1.5 percent hardwood Kraft pulp which was refined to a Canadian Stand Freeness of 540 milliliters were added to 300 milliliters of water. The desired amount of diluted polymer solution was added to achieve the usage rates shown in Table 6 below. Solutions tested were the product of Example 2 wherein the grafted portion comprises acrylamide alone, the product of Example 7 wherein the grafted portion comprises acrylamide and dimethylaminomethacrylate methyl chloride, and the product of Example 11 wherein the grafted portion comprises acrylamide and N,N-dimethylacrylamide. The graft copolymers listed above were compared to the product of Example 1, an ungrafted polyquaternary ammonium polymer which is presently used by the paper industry to increase bond strength.

Table 6 Use Rate Increase in Product Pounds per Percent Scott Tested ton of Pulp Bond Strength Example 1 10 14 Example 2 10 16 Example 7 10 24 Example 11 10 18 The graft copolymers of the present invention give increased bond strength and the presence of cationic comonomers in the grafted portion brings about the best improvement.

While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited thereto since many modifications may be made thereof. It is, therefore, contemplated to cover by the appended claims any such modifications as fall within the true spirit and scope of the invention.

The invention having thus been described, what is claimed and desired to be secured by Letters Patent is:

Claims (25)

1. A water-soluble high-molecular-weight quaternary ammonium graft copolymer comprising a substrate portion and a graft portion, the substrate portion being derived from a water-soluble polymeric quaternary ammonium composition having a plurality of hydroxypropylene groups with the structure

wherein A is a tertiary or quaternary nitrogen atom, and in which the number of quaternary nitrogen atoms exceeds the number of tertiary nitrogen atoms, and the graft portion being derived from a polymeric composition comprising polymerised water-soluble nonionic, anionic andlor cationic vinyl addition monomers, the ratio of graft portion to substrate portion varying from 1:10 to 100:1 by weight.

2. A graft copolymer as claimed in claim 1 wherein the graft portion is derived from polyacrylamide.

3. A graft copolymer as claimed in claim 1 wherein the graft portion is derived from a copolymer of acrylamide and acrylic acid.

4. A graft copolymer as claimed in claim 1 wherein the graft portion is derived from a copolymer of acrylamide and the quaternization product of diniethylaminoethyl methacrylate with dimethyl sulfate

5. A graft copolymer as claimed in claim 9 wherein the graft portion is derived from a copolymer of acrylamide and the q#aternization product of dimethylaminoethyl methacrylate with methyl chlor- ide.

6. A graft copolymer as claimed in claim 1 wherein the graft portion is derived from a terpolym er of acrylamide, acrylic acid, and the quaternization product of dimethylami noethyl methacrylate with dimetnyl sulfate.

7. A graft copolymer as claimed in claim 1 wherein the graft portion is derived from a terpolym er of acrylamide, acrylic acid, and the quaternization product of dimethylamino ethyl methacrylate with methyl chloride.

8. A graft copolymer as claimed in any one of the preceding claims wherein the substrate portion comprises a water-soluble polymeric quaternary ammonium composition derived from methylamine, epichlorohydrin and N,N,N',N' - tetramethyi- ethylenediamine.

9. A graft copolymer as claimed in any one of claims 1 to 7 wherein the substrate portion comprises a water-soluble polymeric quaternary ammonium composition derived from epichlorohydrin and N,N,N',N' - tetramethylethylenediamine.

10. A graft copolymer as claimed in claim 1 wherein the substrate portion comprises a watersoluble polymeric quaternary ammonium composition derived from methylene, epichlorohydrin and N,N,N',N' - tetramethylethylenediamine and the graft portion is derived from polyacrylamide.

11. A graft polymer as claimed in claim 1 substantially as herein described with reference to Examples 2 and 4-15.

12. A process for the preparation of a graft copolymer as claimed in any one of claims 1-11 which comprises reacting a water-soluble polymeric quaternary ammonium composition as defined in claim 1 with one or more water-soluble nonionic, anionic or cationic vinyl addition monomers, in the presence of a polymerisation catalyst.

13. A process as claimed in claim 12 wherein the catalyst comprises a system generating ceric ion.

14. A process as claimed in claim 12 wherein the catalyst comprises a ferrous salt and hydrogen peroxide.

15. A process as claimed in claim 12 substantially as herein described.

16. A process as claimed in claim 12 substantially as herein described in any one of Examples 2 and 4-15.

17. A graft copolymer defined in claim 1 whenever prepared by a process as claimed in any one of claims 12-16.

18. A method of increasing the rate of water removal from wet fibrous webs during the manufacture of paper and paperboard which comprises adding to the papermaking system a graft copolym eras claimed in any one of claims 1 to 11 in an amount sufficient to achieve the desired increase of water removal.

19. A method of improving the retention of the components of a papermaking furnish in the wet fibrous web during the manufactjre of paper and paperboard which comprises adding to the paper making system a graft copolymer as claimed in any one of claims 1 to 91 in an amount sufficient to achieve the desired increase in retention.

20. A method of increasing the strength of paper and paperboard which comprises adding to the papermaking system a graft copolymer as claimed in any one of claims 1 to 11 in an amount sufficient to achieve the desired increase in strength.

21. A method of sizing paper or paperboard which comprises adding to the papermaking system a graft copolymer as claimed in any one of claims 1 to 11 in an amount sufficient to size said paper and paperboard.

22. A method of flocculating solids from an aqueous system containing suspended or dissolved solids which comprises adding to said aqueous system as a flocculant a graft polymer as claimed in any one of claims 1 to 11 in an amount sufficient to cause flocculation of said solids.

23. A method of increasing the rate of water removal during the dewatering of wet sludges which comprises adding to the wet sludges a graft copolymer as claimed in any one of claims 1 to 11 in an amount sufficient to increase the rate of water removal.

24. A method as claimed in claim 23 wherein the wet sludges are derived from municipal and/or industrial effluent.

25. Paper or paperboard whenever manufactured by a process employing, as an additive, a graft copolymer as claimed in any one of claims 1 to 11.