NO823519L - PODE COPOLYMERS CONTAINING QUARTERLY AMMONIUM GROUPS - Google Patents

Description

The present invention relates to new cationic graft copolymers and their applications as flocculants, dry strength additives for paper and color retention agents.

More particularly, the present invention applies to quaternary

ammonium graft copolymers prepared by graft polymerization

of water-soluble vinyl monomers on ion polymers containing quaternary ammonium groups. The present invention relates to the flocculation of suspended matter using the aforementioned polymers, and paper with improved strength and color retention produced by the use of the aforementioned polymers.

A number of methods are known in the art for manufacturing

of graft copolymers. These include radiation methods, both high-energy radiation from gamma rays or electron accelerators

tors and actinic, i.e. photochemical radiation.- Chemical catalysts that are also ■ used include free radical initiators

systems such as the ferro-ion-hydrogen peroxide reaction which is very effective in promoting graft polymerization.

The present invention has been limited to a single method for initiating the polymerization. The cerium ion initiation system taught by Mino, et al: (U.S. Patent No.

2,923,768) is particularly attractive. In this method it is assumed

that the cerium ion reacts directly with a free reactive group such as a hydroxyl group on it. the polymeric substrate.- The radical resulting from this initial reaction can then react

with vinyl monomers. which is present in solution to give 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 polymers of the ion type containing polyquaternary ammonium groups are active. substra.ter. for graft polymerizations.. Graft polymers produced by cerium ion-catalyzed graft polymerization ions on the. aforesaid polymers containing polyquaternary ammonium groups are usually effective as flocculants, dry strength agents for paper, and coloring agents.

Water soluble cationic polymers are used in a variety of applications including the pulp and paper industry to increase strength, and. the dye's ion-n, in water treatment to flocculate suspended solids, and in waste treatment to help

dewatering of sludge. New materials that are effective in these applications are constantly being synthesized and evaluated, and materials with . improved properties would be readily accepted.

An object of the present invention is to provide

new cationic graft copolymers. Another object of the present invention is to provide new. polymers effective in such unspecified applications as flocculation of suspended inorganic and organic matter, color retention and dry strength paper additives, and sludge dewatering.

It is another object of the present invention to provide methods for improving drainage and increasing the retention of fine particles, dyes, pigments, fillers in starch in the papermaking process, as well as increasing strength, improving sizing, and increasing the electrical conductivity of paper

and cardboard. It is another object of the invention to provide methods for improving the dewatering of sewage sludge.

It is another object of the present invention to provide methods for flocculating pollutants in water and methods for. to improve waste treatment...

These and other purposes and advantages of the new polymers and methods according to the invention will be apparent from a subsequent description.

The present invention provides new high molecular weight graft copolymers with quaternary ammonium groups comprising a substrate part and a grafted part. The substrate is a water-soluble polymeric compound with quaternary ammonium groups with a number of hydroxypropylene groups. with. as. general structure

Oil

- A - CH2- CHCH2- A. -

in which A is a tertiary or quaternary.nitrogen atom characteris-. characterized by the number of quaternary nitrogen atoms exceeding the number of tertiary nitrogen atoms. The graft part comprises polymer!ser te, . water-soluble, non-ionic, anionic and cationic vinyl addition monomers. The amount of grafted vinyl addition polymer can vary between one tenth and one hundred times the amount of substrate polymer with polyquaternary ammonium groups. '.

The graft copolymers described above are used to flocculate suspended, inorganic and organic substances in aqueous solutions, to improve drainage and/or retention in the production of

paper, to increase the dry strength of paper, to increase•colour retention,

as well as other applications.

The graft copolymers according to the invention comprise a substrate part, i.e. a previously prepared polymer, and a grafted part.

The substrate polymer is a cationic polymer of the ion type with polyquaternary ammonium groups. In general, these substrate polymers are produced by the reaction between a ditertiary amine and . epichlorhydr in. A suitable method for the preparation of cationic polymers with polyquaternary ammonium groups suitable for use in the present invention is that described in US Pat. 4,054,542. the reactants as well as methods; for production can be found there. These polymers have a molecular weight of approximately 40,000.

In addition to the polymers described above, other polymers described in US patent 4,018,592 can be used. These polymer molecules have molecular weights in the range of 5,000.

A polymer with polyquaternary ammonium groups can be derived from a polyamine by the functionality of the nitrogen atoms in the polymer. In a polymer with polyquaternary ammonium groups, most of the nitrogen atoms are quaternized, i.e. they are covalently bound to 4 carbon atoms. In a polyamine, most of the nitrogen atoms are not quaternized. Polyamines will have nitrogen atoms that are primary, i.e. they are attached to 1 carbon atom and 2 hydrogen atoms, secondary, i.e. they are attached to 2 carbon atoms and 1 hydrogen atom, and tertiary, i.e. they are attached to 3 carbon atoms. I. supplement can

the polyamines have some nitrogen atoms which are quaternary, but these quaternary nitrogen atoms will comprise substantially less than half of the total number of nitrogen atoms.

One. polymer with. polyquaternary ammonium groups are produced

■from a ditertiary amine and another difunctional monomer, such as epichlorohydrin. The reaction between the two monomers for- ; binds a carbon atom from the di.functional monomer to a nitrogen atom on a tertiary nitrogen atom to produce a quaternary.. nitrogen atom. "

In the process which produces polyamines, only one minor amount of reactions takes place which leads to quaternary ammonium-. groups.. In general, a polyamine is prepared from. a multifunctional amine, such as diethylenetriamine, which will contain some primary and some secondary nitrogen atoms. The polymerization ion reactions between the multifunctional amines and the difunctional monomers, such as epichlorohydrins, will change primary nitrogen atoms ' to secondary nitrogen atoms and ' secondary nitrogen atoms to tertiary nitrogen atoms. Inevitably, some of the tertiary nitrogen atoms formed from the preceding reactions will be converted into quaternary groups, but significantly less than half of the nitrogen atoms will be quaternized. Polyamines can also be prepared from methylamine and epichlorohydrin, as taught in US patent 3: 567 659. In this method, a conscious attempt is made to reduce the amount of cross-links by reducing the formation of quaternary nitrogen atoms. The polyamine produced in the aforementioned patent has the structure In solutions with an acidic pH, these polyamines are converted to the: cationic form, for example the hydrochloride salt The structure of a typical polymer with polyquaternary ammonium groups which is used as a substrate in the present invention hair. the general formula

where A is a tertiary or quaternary nitrogen atom, characterized by the number of quaternary nitrogen atoms always exceeding

the number of tertiary nitrogen atoms.

In methods used to prepare polymers

with polyquaternary ammonium groups, a deliberate attempt is made to

to have as many nitrogen atoms as possible in quaternary form. Above. 5 0% of the nitrogen atoms in polymers with. polyquaternary ammonium groups are quaternary nitrogen atoms.

The grafted part of the polymers according to the invention is produced by graft polymerization of water-soluble. vinyl monomers to the hbved chain in the substrate. The water-soluble monomers used in the present invention include acrylamide, methacrylamide, acrylic acid,. methacrylic acid, dimethylaminoethyl methacrylate, N,N-dimethylacrylamide, dimethylaminopropylmethacrylamide, methacrylamidopropyltrimethylammonium chloride, ■dimethyldiallylammonium chloride, the quaternization product between dimethylaminoethyl methacrylate and methyl chloride, the quaternization product between dimethylaminoethyl methacrylate and dimethylsulphate, and other water-soluble monomers which the person skilled in the art will readily come across. Mixtures of two or more of

the water-soluble vinyl monomers can also be used..

Preferred mixtures include acrylamide with one or more of the other monomers listed above. The most preferred mixtures are acrylamide and acrylic acid, acrylamide and dimethylaminoethyl methacrylate, acrylamide and the quaternization product between dimethylaminoethyl methacrylate and dimethyl sulfate, and acrylics,

■amide and the quaternization product between dimethylaminoethyl methacrylate and methyl chloride. • Also included are mixtures of three or more monomers, such as acrylamidacrylic acid and the quaternization product between dimethylaminoethyl methacrylate and dimethyl sulfate.

The graft polymerization can be initiated in one of several ways.

High energy radiation such as gamma rays or electron accelerators are appropriate methods to use in many graft polymerizations. Likewise, photochemical initiation is a convenient source of radicals that are effective in promoting;

graft polymerizations.

The preferred method of initiating polymerization for. to produce the cationic graft copolymers with polyquaternary ammonium groups according to the invention is the use of chemical cata-

lysators. The reaction between ferrous ion and hydrogen peroxide is

Such a preferred catalytic converter system. Other chemical catalysts are obvious to the person skilled in the art.

A highly preferred method of initiating these graft polymers isas ions is to use cerium salts. It is assumed that the cerium ion reacts with free hydroxyl groups present in the substrate polymer. These hydroxyl groups are obtained by the reaction between

epichlorohydrin and a ditertiary amine. The reaction product from this reaction is a polymer containing alternating,

quaternary ammonium units with hydroxypropylene units.

The radical that arises from the reaction between cerium-ion

and the hydroxyl groups are reactive towards vinyl monomers. The polymerization then continues by adding further vinyl monomers and forming a new polymer grafted chain, one end of which is co-

valently bound to the .substrate polymer. The result of this graft polymerization is the cationic graft copolymer with polyquaternary ammonium groups according to the present invention.

The reaction conditions can be varied within wide limits. The graft copolymers according to the present invention can be prepared under conditions in which the amounts expressed in weight of. the polymer with polyquaternary ammonium groups (substrate) and the vinyl monomer (grafting) are approximately the same. For example, the weight ratio between substrate and vinyl monomer can be in the range of 10 to 1 to 1 to 10. Graft copolymers with molecular weights. up to a million or more have been produced using this method.

It has been found that graft copolymers of even higher molecular weight are obtained. when the weight ratio between substrate and monomer

is significantly lower than one-to-ten. For example, graft copolymers with exceptionally high molecular weights are obtained when the ratio

■between substrate and monomer is approx. one-to-fifty. Products made by using these ratios of reactants are quite effective flocculants.

If products with a lower molecular weight are desired, high weight ratios between substrate and monomer are preferred. In addition, as taught in US Patent 3,711,573, isopropanol or other chain transfer agents can be added to the reaction mixture to reduce the molecular weight.

In general, it is desirable to obtain a final product which has a high content of polymer solids. Container costs and shipping costs for polymer solutions with a low solids content will increase the product cost by making it uneconomical itself. about polymer- .

the properties can be superior.. Water-soluble polymers whose polymer weights.are approx.;, a million or. higher, gives very viscous 'aqueous, solutions. The upper limit of polymer content in one aqueous solution of a high molecular weight water-soluble polymer is less than 10% for molecular weights close to one million. Solutions that have high . polymer solids content is too viscous for use in many situations.

In a preferred embodiment. in the process for producing such high molecular weight graft copolymers while

a high total content of polymer solids is maintained, an- . a small weight ratio between substrate polymer and monomer is reversed. The total solids content (substrate polymer plus monomer) is kept high, greater than 10 The reaction is initiated with cerium

ion-catalyst' and polymer in the sa-s the ion continues; To prevent gel formation, as viscosity begins to build up, additional amounts of low molecular weight polymer with polyquaternary ammonium groups (substrate) are added. Since the polymer content in the substrate solution can be 2-5% or higher, it does not decrease. total content of polymer solids in graft copolymer solutionsi. In order to further regulate the viscosity in the graft copolymer solution, isopropanol or other chain transfer agents can also be added, either before, at the same time as, or after the addition of a further amount of polymer substrate solution.

Depending on the amount of monomer in the original batch, and the amount of substrate polymer with polyquaternary ammonium groups added in the second batch, the final polymer solids content can vary from 5 to 25% or higher. - The conditions necessary for effective graft polymerization are not critical. The solution must have an acidic pH, in the range from 1 to 4 pH units. The monomer does not need to be of high purity. For example, acrylamide is often added in the form of a 50% aqueous solution containing copper ion as a polymerization inhibitor. Although a certain advantage can be obtained by removing copper by ion exchange, something can be achieved. higher molecular weights, this purification step is not critical or necessary.

The temperature is also not a critical parameter. Good grafting efficiency is achieved at ambient temperatures as well as at higher temperatures. Removal of oxygen from the solution is often used so that graft copolymers with higher molecular weight 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 known 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 is the case in graft copolymer isa ions.. For certain applications., for example sludge dewatering„ is . it found that high ratios between a cationic monomer,' such as dimethyl sulfate quaternization-. the product of dimethylaminoethyl methacrylate, and acrylamide will give a product with superior properties. For other uses, for

-example water purification, the best results are 'achieved' when the grafted part contains only small amounts of cationic monomer or even when the grafted part is completely non-ionic, i.e. a "polyacryl-

amide grafting..

In order to describe the present invention even more clearly, the following illustrative examples shall be given. It is to be understood, however, that the invention shall not be limited to the specific conditions or details set forth in these examples, except: to the extent that such limitations are specified in the accompanying claims... .Parts as used herein and in the accompanying requirements are weight-parts.

EXAMPLE 1

This illustrates the production of a polymer with polyquaternary ammonium groups which is suitable as a substrate polymer in the subsequent graft polymerizations.

An epichlorohydrin-methylamine prepolymer was prepared by reacting . 800 parts of a 50% aqueous methylamine solution with 2424 parts of epichlorohydrin.'• The reaction was carried out at 35°C in 600 parts of n-propanol solvent. When the reaction was complete, 272 parts of concentrated sulfuric acid were added. The polymer with polyquaternary ammonium groups was then prepared by adding 2007 parts of water and 2275 parts of an aqueous solution containing 60% N,N,N',N'-tetramethylethylenediamine. The mixture was heated to 70-75°C until the contents of the vessel became viscous, at which point the reactants were diluted with 7678 parts water. The mixture was heated again and the reaction continued until the viscosity again increased. The polymerization reaction was stopped by the addition of 402 parts .sulphuric acid and 298 parts ' water. The final solution contained 25% by weight polymer solids. Over 80% of the nitrogen atoms in this polymer are quaternary nitrogen atoms.

EXAMPLE 2

This example describes a method for producing a

graft copolymer according to the present invention..

250 grams were added to approximately 1 liter glass reaction vessel equipped with a stirrer, thermometer and nitrogen injection tube

of the polymer with polyquaternary ammonium groups from example 1, 100 grams of a 50% aqueous acrylamide solution and 147 grams of de-ionized water. The solution was stirred and purged with nitrogen to remove dissolved air. To this mixture was added 3 ml of a catalyst solution consisting of 0.ln cerium ammonium nitrate in ln nitric acid.

A reaction occurred immediately. The temperature rose and the solution became viscous during approx. 5 minutes. The reaction got…

continue for 2 hours. The resulting solution contained 22.5% graft copolymer with polyquaternary ammonium groups in which approx.

55.6% of the graft copolymer originates from the substrate and approx. 44.4% of the graft copolymer is polymerized acrylamide.

EXAMPLE 3

This example describes the preparation of another: polymer with polyquaternary ammonium groups, which is suitable as substrate polymer in subsequent graft polymerizations. ■ -

The ionomer polymer, poly[hydroxyethylene(dimethylimino)ethylene-(dimethylimino)methylene dichloride] was prepared by mixing 375 parts of an aqueous solution containing 60% of N,N,N'. ,'N'-

.tetramethylethylenediamine (TMEDA) and 44.96 parts hydrochloric acid (31.5%

HC1) at a temperature below 50°C. While the temperature was maintained

at 4.0-50°C upon cooling/3,588 parts of epichlorohydrin were added. The mixture was further stirred for half an hour and then heated to 60-7-0°C, at which temperature it became. held while 3750 parts of additional aqueous solution of TMEDA was added. The concentration was adjusted to 60% polymer solids by distilling some of the water from the product. The product's molecular weight: is approx. 5-000. All the nitrogen atoms in this polymer are quaternary

nitrogen atoms.

EXAMPLE 4

This illustrates a method for producing graft copolymers using the polymer from example 3 as a substrate.

,The general procedure from Example 2 was used except that. 313 grams of water, .100 grams of a 50% acrylamide solution and 84. grams of the polymer with. polyquaternary ammonium groups.. from example 3 were added to the reaction vessel. 3 ml of the cerium catalyst was added and a viscous polymer solution was produced within a few minutes. 25 minutes after the addition of the first 3 ml of catalyst, an additional 3 ml of catalyst was added. 25 minutes after this second catalyst charge, was

another 3 ml of cerium catalyst. added. The resulting clear, viscous solution contained approx. 20.1 wt% polymer, in which approx. half was grafted acrylamide and the rest came from the substrate polymer with quaternary ammonium groups from example 3.

EXAMPLES- 5- 11

The general procedure from Example 2 was used except that 118.5 grams of water, 7.5 grams of isopropanol, 70 grams of acrylamide and 250 grams of polymer with polyquaternary. ammonium groups from. Example. 1 was stirred. in the reaction flask. In addition to the acrylic amide, the water-soluble vinyl addition monomers listed in Table 1 were used in separate preparations. In each case, 30 grams of the listed monomers were added. 3 ml'. ser ium catalyst was. added. In each case the temperature rose, and the solution became viscous, indicating that graft polymerization is occurring. Additional cerium catalyst (.3 mL for each addition) was added. A total of 24 ml of catalyst was added in each example except in Example 11 where only 12 ml was added. In this case the solution was already extremely viscous.

EXAMPLE 12

The procedure of Example 2 was followed with the exception that the cerium catalyst was not used. 250 grams of the polymer from example 1 with quaternary ammonium groups, 100 grams of a 50% acrylamide solution and 147 grams of water were added to the reaction vessel. The pH was adjusted to 3.5 with a 50% sodium hydroxide solution. 2 ml of 0.35% hydrogen peroxide was added, to the flask, quickly, followed by 2 ml of a solution consisting of 0.1 ml of ferro-ammonium sulphate in 1 ml of sulfuric acid. An instant temperature rise stepped., followed by an increase in viscosity. • The reaction was allowed to continue, for 40 minutes, after which 7.5 ml of isopropanol was added, followed by a further batch of the catalyst, i.e. 2 ml of 0.35%

•hydrogen peroxide and 2 ml of ferrous solutionsv. During the following 2 hours, two further additions of the catalyst system (ferro solution and r^C^) were made.' The resulting solution had a similar appearance and composition to the product of Example 2, except that the product in this example contains slightly less polymer solids, 21.6%."

EXAMPLE 13

The following example • describes the production line of the graft copolymer with polyquaternary ammonium groups according to the present invention using a combination of two catalyst systems.

The same procedure as. in example 2 was followed. To the reaction vessel was added 250 grams of the polymer from example 1, 100 grams of one. 50% acrylamide solution and 147 grams of water. 3 ml of the cerium catalyst was added. The temperature rose and the solution became viscous. 2 hours after the reaction had been injected, 7.5 ml of isopropanol was added, followed by 2 ml of 0.35% hydrogen peroxide solution and 2 ml of ferrous sulphate. solution described in Example 12. A significant amount of unreacted monomer was present after the first addition of the cerium catalyst. since there was an immediate rise in temperature and a small increase in viscosity. Two further additions of 2 ml each of the peroxide and the ferrous solutions were carried out. There was no apparent reaction. after the last catalyst addition. The product from this example was very similar to the product from example 12 in terms of appearance and composition.

EXAMPLE 14

The following illustrates another method of manufacture

of the graft copolymers according to the invention..

The general procedure from example 2 was followed except that two reaction vessels were added with 100 grams of a 50.%ig

■acrylamide solution, 147 grams of water and 4 grams of polymer with polyquaternary ammonium groups ■ from.. example 1. The ratio between . acrylamide and polymer with polyquaternary ammonium groups were there for 50 to 1 on a solids basis. ■, 3 ml of the cerium catalyst solution was added to each vessel. 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 began..'to creep up'the stirrer shaft, -250 .ml of water was added to it

first chosen, solution 14A and. 250 ml of the polymer with polyquaternary ammonium groups from example 1 was added to the second vessel, -. solution ,14B. The reactions continued as. it proved. by a slow rise in temperature and a noticeable increase in viscosity. 2 hours after the original addition of kåta- . • lysator, a further 300 ml of water was added to solution 14A'.

Then to each solution was added 7.5 ml of isopropanol, followed by the addition of -2 ml of dilute hydrogen peroxide and 2 ml of the ferrous solution described in Example 12. A second batch of 2 ml of each of the ferrous solution and peroxide solution was added to each solution.

The resulting solutions had approx. 6.3% polymer solids

in solution-14A and- 2i;8% in solution 14B.

EXAMPLE 15.'

The graft polymers with polyquaternary ammonium groups according to the invention were tested for effectiveness as flocculants in laboratory glass tests. 1500 ml of a 0.4% suspension of Fuller's earth (Kaolih) was added to each glass and stirred with stirrers at one speed of 100 revolutions per minute. minute. Different quantities: of the polymer solution to be tested

was added and stirring was continued for 1 minute after which stirring--." none was stopped and the suspension was allowed to settle for 5 minutes.

Observations were made on the flocculation rate, i.e. the deposition rate, as well as the final clarity of the above solutions after 5 minutes.

The flocculation rate was assessed/qualitatively and the polymers were ranked in order of their flocculation rate. The clarity of the test detachment was graded on a scale from 0 to 5 (0 means no deposition and 5 means a clear overlying layer) after deposition for 5 minutes.

Table 2 compares the properties of the graft copolymer which

is produced in example 2 with. two commercially available products that are both used to treat water to remove suspended solids. Commercial product A has 25% by weight and commercial product B has 40% by weight of polymer solids. A dilute solution (1500 ppm): av. each polymeric product to be tested was first prepared.' Then 2., 4, or 8 ml of these were diluted

. the polymer solutions added to the Kaolin suspension .. The usage of each polymeric dilution product was therefore 2, 4 or 8 ppm. Since the products differ on a solids-percent basis, is

however, the amount of use on a total polymer-solids basis naturally differs...-

The product from Example 2 gave the fastest deposition rate for each application amount. It can be seen in table 2 that they the two commercial products provide good clarity at these usage amounts with a maximum effect close to 4 ppm. The product from example 2, in addition to having the fastest deposition rates, provides significantly better clarity at a somewhat higher amount of use, without diminishing effectiveness. tet at higher usage quantities. Excellent efficiency occurs over a wide application rate range.

EXAMPLE 16

This illustrates the effectiveness of the graft copolymers with . polyquaternary ammonium groups when it comes to flocculating suspended matter when the grafted portion of the polymeric product is a mixture of acrylamide and other water-soluble vinyl addition monomers...

The procedure from example 15' was followed. The polymer release agents tested were prepared from the products of Example 5. t il .10, as well as example 2. The results are shown in table 3 below.

All the graft copolymers in the above table exhibit excellent fioculation properties.

EXAMPLE 17 This example illustrates the effectiveness of the graft copolymers.

according to the present invention as flocculating agents, for sewage sludge......

The apparatus consisted of a No. 1 Buchner funnel placed directly above a ..250 ml graduated cylinder. A piece of filter cloth was cut to the same dimensions as. No. 1 f 11 wood paper and. this, the filter cloth

was placed'in the Buchner tract;. This filter cloth was of the same type used in sludge dewatering presses.

5% dilutions of the polymer solutions to be tested were prepared. For each test, 500 ml of sewage sludge (3.4%

solids) placed in a beaker. The desired amount of diluted polymer solution was placed in another glass beaker.

The slurry was 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 Buchner funnel.•

The solution was allowed to drain by gravity, ie no pressure or vacuum was applied. The amount of liquid collected in the graduated cylinder was recorded after 15, 30, . 60

and 120 Seconds. The better the sludge dewatering efficiency of the polymer, the more liquid will be collected at a given time.

Two graft polymers were prepared for the testing. The procedure from example 6 was used to prepare solution D. To the reaction vessel was added 147 grams of water, 250 grams of polymer with polyquaternary ammonium groups from example 1, 70 grams of a 50% acrylamide solution and 30 grams of an 80% aqueous solution of di -methylaminoethyl methacrylate methosulfate. Cerium catalyst was added nine times in 3 ml portions over the next four hours.

Solution E was produced on a slightly larger scale. A 2 liter reaction vessel was added with 828 grams of water, 1000 grams of polymer with polyquaternary ammonium groups from example 1, 160 grams of a

5.0% acrylamide solution and 40 grams of isopropanol. 12. ml serium-ka ta light a two r ble. added.

Table "4 shows the sludge removal efficiency of the solutions

D and E compared to the efficiency .to. one commercial to-.,

.common, cationic polyacrylamide polymer used in sludge dewatering applications.

The table shows that graft copolymers according to the present invention are effective for dewatering sewage sludge.

EXAMPLE 18

The polymeric mixtures from Example 15 according to the invention were tested for their effectiveness when it comes to retention of total solids in a pulp slurry using the method described in Example 15 in US Pat. 4. 250 269, which description is hereby made into. part of the present application. Fractionation of the pulp slurry showed that the slurry contained 27% fines. The percentage retention of fines could then be calculated when the retention of total solids and the percentage of fines in the original slurry were known. Table 5 shows that the acrylamide graft copolymer with polyquaternary ammonium groups from example 2 is superior to the ungrafted polymers with polyquaternary ammonium groups from example 1, a product that is often used as a retention aid.

EXAMPLE 19

This example illustrates the effectiveness of the graft copolymers. according to the present invention to increase the dry strength of paper.

"Hå.ndark was prepared and tested using a Scott Internal Bond Tester. 300 grams of a 1.5.<%>ig harder Kraft pulp which-was-refined to a. Canadian Stand .Freeness of 540 ml, was added , to 300 ml of water. The desired amount of dilute polymer solution was added to achieve the usage amounts shown in Table 6 below. Solutions tested were the product of Example 2

in which the grafted part comprises only acrylamide, the product from example 7 in which the grafted part comprises acrylamide and dimethylaminoethyl methacrylate methyl chloride and the product from example 11 in which the grafted part comprises acrylamide and N,N-dimethylacrylamide. The graft copolymers listed above were compared with. the product of Example 1, an ungrafted polymer with polyquaternary

ammonium groups which are currently used in the paper industry to increase the bond strength.

The graft copolymers according to the present invention give increased bond strength and the presence of cationic comonomers in the grafted part gives the best improvement.

While particular embodiments of the invention have been described, it should of course be understood that the invention is not limited to these since many modifications can be made. It is therefore believed that the accompanying requirements should cover all such modifications

.which falls within the scope of the invention.

Claims (16)

1. Water-soluble, high molecular weight graft copolymer with quaternary ammonium groups comprising as a substrate, - a water-soluble, polymeric compound with quaternary ammonium groups with a number of hydroxy-•propylene groups with the structure wherein A is a tertiary or quaternary nitrogen atom, . characterized in that the number of quaternary nitrogen atoms always exceeds the number of tertiary nitrogen atoms. -and comprising as the grafted part of the product a polymeric compound- selected from the group consisting- of water-soluble, non-ionic, anionic and cationic vinyl addition polymers, and further characterized in that the amount of grafted vinyl addition polymers varies between one tenth and a hundred times the amount of the substrate polymer with polyquaternary ammonium groups.. 2. Graft copolymer according to claim 1, characterized in that the vinyl addition graft polymer is polyacrylamide. 3. Graft copolymer according to claim 1, characterized in that the vinyl addition graft polymer is a copolymer of acrylamide and acrylic acid. 4. Graft copolymer according to claim 1, characterized in that the vinyl addition graft polymer is a copolymer of acrylamide and the quaternization product of dimethylaminoethyl methacrylate with dimethylsulphate. 5. Graft copolymer according to claim 1, characterized in that the vinyl addition graft polymer is a copolymer of acrylamide and the quaternization product of dimethylaminoethyl methacrylate with methyl chloride. 6. Graft copolymer according to claim 1, characterized in that the vinyl addition graft polymer is a terpolymer of acrylamide, acrylic acid and the quaternization product of dimethylaminoethyl methacrylate with dimethyl sulfate. 7. Graft copolymers according to claim 1, characterized in that the vinyl addition graft polymer is a terpolymer of. acrylamide, acrylic acid and the quaternization product of dimethylamino ethyl methacrylate with methyl chloride. 8 . Graft copolymer according to claim 1, characterized in that the substrate is a water-soluble polymer compound, with quaternary ammonium groups obtained from methylamine, epichlorohydrin and N,N,N',N'-tetramethylethylenediamine. 9. Graft copolymer according to claim 1, characterized in that the substrate is a water-soluble/polymeric compound with quaternary ammonium groups obtained from epichlorohydrin and N,N,N',N'-tetramethylethylenediamine. 10. Graft copolymer according to claim 1, characterized in that . the substrate is a water-soluble polymeric compound with quaternary ammonium groups obtained from methylamine, epichlorohydrin and N,N,N1,N'-tetramethylethylenediamine and the vinyl addition graft polymer is polyacrylamide. 11. Method for increasing the rate of water removal from wet fibrous tissues during the production of paper and cardboard, characterized in that for paper production .system, the graft copolymer from claim 1 is added in an amount sufficient to achieve the desired increase in water removal. 12. Method for improving the retention of the components in the papermaking process in the wet fibrous tissue during the production of paper and cardboard, characterized in that the graft copolymer, according to claim 1, is added to the papermaking system in an amount that is sufficient to achieve the desired 'increase in retention. 13. Method for increasing the strength in paper and cardboard, characterized by . that the graft copolymer according to claim 1 is added to the papermaking system in an amount sufficient to. to achieve the desired increase in strength. 14. Method for gluing paper or cardboard, characterized in that the graft copolymer according to claim 1 is added to the paper production system in an amount sufficient to glue said paper and cardboard. 15. Procedure for flocculation of solids from an aqueous system containing suspended or dissolved solids, k a 'r -a c t e r i s e r t . in that the graft copolymer according to claim 1 is added to said aqueous system as a flocculating agent in an amount sufficient to cause flocculation of said solids. 16.. Method for increasing the rate of water removal • during dewatering of wet sludge obtained from municipal and industrial . outlet, characterized in that the graft copolymer according to claim 1 is added to the wet sludge in an amount which is sufficient to increase the rate of water removal.