CA2780597A1 - Process for enhancing dry strength of paper by treatment with vinylamine-containing polymers and acrylamide-containing polymers - Google Patents

Abstract

A process is disclosed for the production of paper with enhanced dry strength comprising adding to the wet end of a paper machine, (a) a vinylamine-containing aqueous solution polymer having a molecular weight of from 75,000 daltons to 750,000 dalions and (b) an amphoteric or cationic acrylamide-containing aqueous solution polymer having a molecular weight of from 75,000 daltons to 1,500,000 daltons, wherein the sum of the anionic and cationic monomers comprises at least 5% on a molar basis of the composition of the acrylamide-containing polymer.

Description

2 PCT/US2010/061750 PROCESS FOR ENHANCING DRY STRENGTII OF PAPER BY TREATMENT Vv'ITII
VINY1:AMJNE-CONT.ATNING POLYMERS AND ACRY.L:AM.IDE-CONTAINLNG
POLYMERS
FIELD OF THE TNVENTTON
[0001,1 This invention relates to enhanced day strength in paper using a process of treating a pulp slurry with a combination of a vinylamine-containing polymer and a cationic or amphoteric acrylarnide-containing polymer.

BACKGROUND OF THE INVENTION
[0002] The papermaking industry is constantly seeking new synthetic additives to improve the dry strength of paper products. Improved city strength can give a higher performance product, but also may allow the paperanaker to use less cellulosic fiber to achieve a particular performance target. Furthermore, the increased usage of recycled fiber results in a weaker sheet, forcing the paperrnaker to either increase basis weight of the sheet or employ synthetic strength additives. The options that are known have various economic and technical limitations. For- instance, according to US Patent No.
6,939,443, the use of combinations of po.lyaaniide-epichlorohycirian (PAE) resins with anionic polyacrylamide additives with specific charge densities and molecular weights can enhance the cry strength of a paper product. However, these. combinations also may elevate the wet strength of the resultant paper to the point that repulping broke paper is extremely difficult and inefficient.

[0003] Polymers of acrylanaide or copolymers incorporating acrylamide and a monomer such as cliallyldianethylamnaouiurta chloride. when treated with a dialdehyde compound such as glyoxal, are widely known to result in resins that can also enhance the dry strength of paper signilicantty, yet have very limited permanent wet strength properties, allowin the, papenuaker to easily rcparlp broke paper. However, these resins also have their limitations. These additives either have a very short sltelflife due to viscosity instability, or are shipped at very low active solids content. Furtlhermore, when added in the larger amounts, the performance of such dialdehyde-modified acrylamide-containing polymers tends to reach a plateau, making a high-perfornmance product difficult to manufacture.

[0004] Polyvinylamine resins have become popular in the paperanmaking industry not only because they endow a sheet with increased dry strength, but also because of their easy handling and application as well as the increased retention and drainage they afford the paper machine. However, when added in ever increasing amounts, they have the negative effect of overflocculating the sheet because of the heavy cationic charge these resins carry.
Overflocculation results in a poorly formed, weaker finished product.

[0005] Other inventions have sought to augment the positive effects of polyvinylamine. According to IUS Patent No. 6,824,650 and European Patent No.
1,579,071, the combination of polyvinylamine with glyoxalated polyacrylamide resins in a pulp slurry results in enhanced product dry strength. However, the aforementioned drawbacks of glyoxalated polyacrylamides, namely low active solids of the product and limited viscosity stability of the product, are clearly in play.

[0006] -US Patent No. 6,132,558 discloses a paperniaking system wherein a pulp slurry is treated first ;kith a highly cationic polymer, including vinylamine-containing polymers, of molar mass of 5,000 to 3,000,000 daitons, and subsequently with a second cationic acrylamidc-containing polymer of molar mass of more than 4,000,000 daltons, subjected to a shearing stage, then treated. with a finely divided inorganic flocculating agent, such as bentonite, colloidal silica, or clay.

[0007] US Patent Publication 2008/0000601 discloses a process of papermaking where the pulp slurry is treated with a polymer, including vinylamine-containing polymers, of molar tuass of more than 1,000,000 daltons, as well as a second polymer, including cationic ae;rylamide -containing polymers, with a molar mass of more than 2,500,000 daltons, all in the absence of finely divided inorganic flocculating agents.

[0008] US Patent No. 6,746,542 discloses a method of papermaking wherein a pulp slurry is treated with starch that has been modified at a temperature above the starch gelatinzation temperature with a highly cationic: polymer, including vinylamine-containing polymers, of molar mass of less than 1,000,000 daltons. The pulp slurrv is subsequently treated with a second polymer, including cationic acrylamide-containing polymers, with a molar mass ofrnore than 1,000,000 daltons.

[0009] US Patent Publication 2008/0196852 discloses a retention aid system for papernmaking which comprises at least one polymer, including vinylamine-containing polymers, at least one linear, anionic polymer of molar mass of more than 1,000,000 daltons, and at least one particulate, anionic, crosslinked, organic polymer.

[001()] Combining vinylamine-containing polymers with acrylamide-containing polymers may he both the simplest and most effective means for producing a high performance paper product while maintaining paper machine productivity and repulping broke paper. However, examples from the prior art that may include these polymers have significant drawbacks. For instance, previous examples may require special metering apparatuses, additional steps for treating starch prior to addition to the pulp slurry, or high molar mass polymers that may result in over0oceulation of the pulp slurry when added in sufficient amounts to affect dry strength.

BRIEF DESCRIPTION OF THE IINIVENTION
[00111 Treatment of a p<,ulp slurry with a vinylarnine-containing aqueous solution polymer in combination with a cationic or amplioteric actylan~ide-containing aqueous solution polymers result in paper with enhanced dry strength.

[0012] This combination is most effective when the active polymer solids content of the acryl:amide-containing aqueous solution polymer ranges from Sig to 50% o by weight, and the content of the suns of the cationic and anionic monomers in the acrylarnide-containing polymer ranges from 5% to 50% on a molar basis of the total monomer content, and the molecular weight of the acrylamuide-containing polymer ranges from 75,000 daltons to 1,500,000 daltons.

[0013] The vinylamine-containing polymer is most effective when it contains at least 50% on a molar basis of N-vinylformami.de monomer, at least 10% of which has been hydrolyzed in the feral product and has a molecular weight in the range of from 75,000 daltons to 750,000 daltons. The aqueous solution containing the vinvlamine-containing polymer has a total polymer solids content of from 5% to 30% by weight,.

[0014] One embodiment of the invention is a process for the production of paper, board, and cardboard with enhanced dry strength comprising adding to the wet end of a paper machine (a) a vinylainine-containing aqueous solution polymer having a molecular weight of from 75,000 daltons to 750,000 daltons and (b) an amphoteric or cationic acryl<unide-containing aqueous solution polymer having a molecular weight of from 75.000 daltons to 1,500,000 daltons, where the sum of the anionic and cationic monomers comprise at least 5%
on. a molar basis of the composition of the acrylamide-containing monomer.

[00151 In one embodiment of the process the vinylamine-containing polymer has an AT-vinylformamide content of at least 5044, on a molar basis of the total monomer charged, at beast I0% of Which has been hydrolyzed in the final polymer, and an active polymer content of from 5% to 30% on a weight basis.

[00161 in one embodiment of the process the acrylamide-containing aqueous solution polymer contains a sum cationic and/or amphoteric monomer charge of from 5% to 50% on a molar basis, and has an active polymer content of from 5% to 50% on a weight basis.

[0017] In one embodiment of the process the acs ~~lamide containi.ixg aqueous solution polymer is of an aqueous dispersion polynier.

[00151 In one embodiment of the process the acrylamide-containing aqueous solution polymer contains a cationic monomer charge of from 5% to 50% on a molar basis, has an active polymer content of from 54% to 50% on a weight basis, and comprises a leas', one cationic monomer selected from the group consisting of diallyldi-m ethylarnmoniuni chloride (DAD AAC), 2-(d imetliy[amino)ethyl aciylate, 2-(dimethylamino)ethyl methacrylate, 2--(diethyiaminoe.thyl) acrylate, 2-(diethylainino)ethyl ineethacrylate, 34dimethylamino)propyl acrylate, 3-(diniethylamino)propyl methacrylate, 3-(diethylanlino)propyl acrylate, 3-(diethylamino)propyl niethacrylate, i-[3-(dimetlrylamino)propyllacrylanide, N--[3--(dimethylanrino)propyl]methacrylaniide, A~-[3-(dietlry%larnino)propyl]acrylamidc, N-[3-(diethylamino)propyllniethaci-ylamide, [2-(acry;Ioyloxy)ethyl1trunnethylarnnroi.iu,7i chloride, [2-(methacryloyloxy)eddy::]trimethyianimoniunm chloride, [3-(acryloyloxy)propyltrime.thylanmmnium chloride, [3-11 (metlracrvloyloxy)propylltriniethylammoniurn chloride, 3-(acrylainiidopropyl)trinretl.,ylaniinoniuin chloride, and 3-(netliacrylam idopropyl)trimethylanunonium chloride.

[0019] In one. embodiment of the process the acrylamide- containing aqueous solution polymer has an overall aniphoteric charge.

[00201 In one embodiment of the process the amphoteric acrylamide-containing aqueous solution is comprised of a polyelectrolyte complex consisting of an acrylamide-containing aqueous solution polymer and a cofactor carrying an opposing charge, [0021 ] In one embodiment of the process the vinylamine-containing polymer and the acrylamide-containing polymer are a single product blend and the cationic portion of the anmphoteric acr lamide-containing polymer is generated by at least one monomer selected from the group consisting of dial lyldinrethylammonium chloride (DADIVIAC), N..[3..
(din?ethylamni;?o)propyl]acrylamide, :'U-[3-(diniethylan?ino)propyl:(methacryla?nide, V-[3-((Iiethylanino)propyl]acrylamide, N-[3-((liethylap?ino)propyl]rnethacrylamide, (acrylamx?idopropyl)trinmethylanimoniuÃm. chloride, and 3-(n?ethactylatnidopropyl)triniethylat??n?opium chloride.

[0022] In one embodiment of the process the vinylamine-co??taining polymer and the acrylamide-containing polymer are added to the wet end of a paper machine in a ratio of vinyia a?inc coirtaiuing polymer to ac~ylauride contain?ing polymer of from

10:1 to 1:50 up to a sum total of 1.25% on a weight basis of the dry pulp, based on the active polymer solids of the polymeric products.

[0023] One embodiment of the invention is the paper product produced by the process of adding to the wet end of a paper machine (a) a vinylamine-containing aqueous solution polymer having a molecular weight of from 75,01;0 daltons to 750,000 daltons and (b) an an?pi}oteric or cationic acrylamide-containing aqueous solution polymer having a molecular weight of from 75,000 daltons to 1,500,000 daltons, where the sum of the anionic and cationic monomers comprise at least 5% on a molar basis of the composition of the acrylam?de-containing monomer.

[0024] hr another embocunient, the invention relates to the method. of treating a cellulosic pulp slurry in the wet end of a paper machine with (a) a vinylanliirc. staining polymer and (b) a cationic or amphoteric acrylamide-containing aqueous solution polymer. it is preferred that the vinylamine--containing polymer is added to the pulp slurry first, followed by the acrylainide-containing polymer.

DETAILED DESCRIPTION OF THE INVENTION
[0025] As used herein, the singular terms "a" and "the" are synonymous and used interchangeably with "one or more" or "at least one" unless the context clearly indicates a contrary meaning. Accordingly, for example, reference to "a compound" herein or in the appended claims can refer to a single compound or more than one compound.

[0026] As used herein and unless otherwise stated, the terms "vinylarine-containing polymers," is tnrderstood to mean inonnopolymers of vinylamitne (e.g., polyvinylarnine or fully hydrolyzedpolyvinyltorniamide}, copolymers of vinytarnine with other ct nmoomeas, partially hydrolyzed polyvinylformamide, partially hydrolyzed vinylformamid.e copolymers, Vinylamine terpolynier:s, vinylarnirnc home.- and copolymers manufactured by the Hofmann modification of acrylarnnide polymers, or virtylarnine containing polymers that are chemically modified after polymerization. Examples may include those described in US
Patent.
Publication number 2009/0043051 or number 2008/0196851.

[00271 As used herein and unless otherwise stated, the term "ac3ylaniide-containing polymer" refers to the cationic or amphoter-ic acrylamide-containing aqueous solution polymer.

[00281 As used herein and unless otherwise stated, the term "aqueous solution polymer" refers to a polymer that forms a fully homogenous solution in water when diluted to I% on a dry solids basis, in the absence of any cosolvent. For instance, an aqueous solution polymer does not include oil-in-water or water-in-oil emulsions. Examples of aqueous solution polymers may include aqueous dispersion polymers, such as are described in US
Patents 5,541,252 and 7,323,510 as well as US Patent Publications number 2002/198317 and number 2008/0033094.

[00291 The invention is based in the discovery that the performance of a paper machine and the paper products derived thereby can be greatly enhanced by the treatment of th.e pulp slurry with a vinylannin containing polymer in combination with an acrylamide-containing polymer with particular molecular weight and charge attributes as described below. Use of a vinylarmne-containing polymer alone provides both strength and drainage pe"fo-i mance in the papemiaking system; liovv'ever, when added in ever-increasing amounts, the performance of the paper product first levels oft, and then deteriorates, largely due to overflocculation of the forming paper web. It has une.xpec-tly been found that the addition of vinylamiae-containing polymer- in conjunction with the addition of aqueous solution acrtila.nido-co ntaining polymers having substantial amphoteric or cationic charge results in a product with strength performance beyond that which can be attained by using vinylamine-containing or aerylamide-containing polymers alone; moreover, the excellent drainage performance achieved by using a vinyÃamine-containing polymer can be substantially maintained using such a combination of polymers.

[0030j The vinylarnine-containing polymer is most effective when its molecular weight is from 75,000 daltons to 750,000 daltons, more preferably of from 100,000 daltons to 600,000 daltons, most preferably of from 150,000 daltons to 500,000 daltons.
The molecular weight can be from 150,000 daltons to 400,000 daltons. Below the molecular weight threshold of 75,000 daltons, little to no strength performance is observed, and substantial drainage performance enhancement is not observed. The vinylarmine-containing polymer is not cooked with starch prior to addition to the pulp slurry. A vinylanine-containing polymer above the molecular weight of 750,000 daltons will generally negatively affect formation at dosages required for dry strength enhancement because of the tendency to overllocculate the sheet, resulting in lower strength. An. aqueous solution vinylarnine-containing polymer above 750,000 daltons either is typically made at such high viscosities as to render product handling extremely difficult, or alternatively is made in such low product polymer solids as to render the product not cost effective to store and ship.

[00311 The active polymer solids percentage of the vinylarnine-containing polymer ranges of from 5% to 30%, more preferably from l % to 20% by weight of the total vinylarnine-containing polymer product content. Below 5%:% active polymer solids, higher molecular weight aqueous solution polymers may be possible, but the product becomes ineffective with respect when shipping and transportation costs are accounted for. On the other hand, as the active polymer solids rises, the molecular weight of the polymer must decrease overall so that the aqueous solution is still easily pumpablc. Thus, a practical relationship can be drawn/ between the total polymer solids of the virryhrrnirre containinf;
polymer product and the molecular weight of such a poly.ner, and a correlation can be drawn between these parameters and polymer performance.

[0032 i l:he performance of the vinylamine-containing polymer is influenced by the amount of primary amine present in the product. The vinylarnine moiety is typically generated by acidic or basic hydrolysis of N" vinylacylarnide groups, such as N-vinylformamide, N-vinylacetamide, or 11r-vinyl propionaFnide, most preferably N-viny1formamicle. The vinylarnine-containing polymer is most effective in enhancing the dry strength of a paper product and/or the drainage performance of a papermaking system when the amount of N'-vin 1formamide is at least 50% on a molar basis of the hydrolyzed polymer.
After hydrolysis, at least 10% of the N-vinylforrnamide originally incorporated into the resultant polymer should be hydrolyzed. Without wishing to be bound by theory, the hydrolyzed N-vinylforzmamide group may exist in various structures in the final polymer '7 product such as primary or substituted amine, amidine, guanidine, or amide structures, either in open chain or cyclical forms after hydrolysis.

[0033) The acrylamide-containing polymer is most effective when it contains a substantial amount of a positively charged conronomer(s). Without wishing to be bound by theory, the positively charged monomer allows the acrylamide-containing polymer to adhere to the cellulose fibers due to a charge-charge interaction with negatively charged substances in the pulp slurry, including, but not limited to: pulp fibers, hemicellulose, oxidized starch commonly found in recycled cellulose funaish, anionic strength aids such as carboxymethylcelhdose, and anionic trash. The incorporation of cationic groups into the acrylarnide-containing polymer is generally not detrimental to the drainage performance of the paperniaking system. Without wishing to be bound by theory, the hydrogen-bonding components of the acry laniide-containing polymer, such as amide groups, are effective in enhancing the dry strength of the paper product.

[0034j Suitable cofnononiers used to impart cationic charge to tile. polymer include, but are not limited to, diallyldirnethylanimoniuni chloride (DADMIAC), 2-(dimethylamino)ethyl acrylate, (dig iethylaniii;o)ethyl ntethacrylate, 2-(diethylaminoethyl) acrylate, 2-(diethylatnino)ethyl nmethacrylate, 3-(dimetliylamino)propyl acrylate, 3-(dimethylamino)propyl meihacrylate, 3-(dieth_ylamino)propyl acrylate, 3-(dii t?tylarnino)itropyl rnethacrylate, ,~% [3 (diitlethylariiino)prc>l;yl]aerylanaide, I [3 (dime.thylamino)propyl]methaciylamide, N t -(dietliylamino)propyljaerylanncle, (diethylanrino)propyI)methacryla:nide, [2-(acryloyluxy)ethyljtrirnethylam;noniuIn chloride, [2-(anetlracryloyloxy)etlt}~l]trirnethylarrunoniuur chloride, [3-(acry loyloxy)p-opyljtrimethylanmmtnaium chloride, [3-(tnetliacryloyloxy)propyljtrimethiylammmiiiunt chloride, 3-(acrylanridopropyl)trirnethylainmonium chloride, and 3-(rnethacrylarnidopropy1)trimethylamrnoniLit' a chloride. Such cationic monomers Can affect.
the performance of the cationic or arnphoteric polymer when incorporated into the polymer backbone.

[0035.1 The amount of cationic monomer incorporated into a polymer may be from 5% to 50% on a molar basis of all the monomers incorporated into the aacrylamide-containing polymer in the case of a cationic polymer. In the case of an amphoteric polymer, the amount of the cationic monomer plus the amount of an anionic monomer described below may be from 515; to 50`.%;, more preferably from 15% to 40%, on a molar basis of all the monomers incorporated into the acrylarnide-containing polymer. The acrylamide-containing polymer may be cross-linked with an agent such as methylene bisacrylainide (NIBA) provided the molecular weight and charge guidelines are met as described herein.

[0036] The incorporation of an anionic con-ionomer into the acry lamide-containing polymer along with the cationic comonomer, forming an aniphoteric acrylarnide-containing polymer, is also effective in enhancing the dry strength of a paper product made thereby.
Without wishing to be bound by theory, the anionic corooromer allows the ampl:oteric polymer to forin a coacervate complex with a wide variety of substances fotmd in a recycled pulp shun-y, including, but not limited to: a vinylamine-containing polymer, a cationicaily charged flocculant or coagulant, cationic or amphoterie starch, polya midoarriine epichlorohydrhi wet strength aids, or another amphoteric acrylamide--containing polymer.
Moreover, the combination of cationic and anionic monomers in the acrylarnide-containing polymer either enhances or does not negatively affect the drainage performance of a papermaking system when compared to an acrylaniide-containing polymer using only an anionic coniononner. Suitable anionic conionomers include, but are not limited to, acrylic acid, inethacrylic acid, itneonic acid, itaconic anhydride, rnaleic anhydride, rnnleie acid, styrene sulfon:tafe, vinyl sralfonate, 2-acrylan ado 2 niethylpropane sulfonate (AMPS).
Alternatively, such substructures may be generated by hydrolysis of a precursor stnicture (e.g. generation of inethacaylic acid in the polymer backbone via hydrolysis of methyl n:rethacrylate af}er the formal polyrnerizatiorr). The amount ofcharged monomer incorporated into the a,,rylanridc-containing polymer May affect the performance of the polymer. Such anionic monomers may be used in an anrphoteric acrylamide-containing polymer, and the amount of the anionic monomer plus the amount of a cationic monomer described above may be from 5% to 50% e on a molar basis of all. t e moiririners incorporated into doe acrylamida-containing polymer. The acrylarnide--containing polymer may be cross-linked with an agent such as nrethyiene bisacrylaniicie (MBA) provided the molecular weight and charge guidelines are motet as described herein.

[003-7] The properties of an amphoteric aqueous solution acrylarnide-containing polymer as defined above can also be effectively produced by the use of an acrylarnide-=
containing polyelectrolyte complex. When combined with a vinylaniine-containing polymer, such an acrylarnide-containing polyelectrolyte complex may also produce benefits similar to those described above. when vinylainine-containing polymers are combined with cationic or amphoteric acrylamide-containing polymers. Although polyelectrolyte complexes in various forms have been disclosed, such as in European Patent Publication No-1,918,455 Al, herein we disclose the unexpected result that the effectiveness of such polyelectrolyte complexes in generating dry strength beyond what the polyelectrolyte complex may provide on its own, may be achieved when they are used in combination with vinylamnine-containing polymers.
An acrylaside-containing polyelectrolyte complex contains an acrylamide-containing polymer of either cationic, amphoteric, or anionic charge, as well as a second polymer of a.
complementary charge. For example, an anionic ac ylamide-containing polymer made by polymerization of acrylarnide with one of the suitable anionic monomers listed above can form a polyelieetrolvte complex with a cationic polymer, which may or may non include acrylannide. Such cationic polymers include, but are not limited to, allylamine-epichlorohydrin polymers, cationic acrylamide--containing polymers as described above, polyarnutoatnire-elnicinloralrydrin polymers, aodpolyethyl~neimine polymers.
The acrylamide-containing polyelectrolyte complex may also comprise a cationic acrylamide-containin polymer and an anionic polymer. Such anionic polymers include, but are not limited to, polymers and copolymers of (meth)acrylic acid, polymers and copolymers of tnaleic acid, and carboxymethyl cellulose. The acrylannide-containing polyelectrolyte complex may be added to the papermaking slurry either as a single blended product or as two separate products, most preferably as a single blended product. The amphoteric polyelectrolyte complex carries a net charge, expressed in milliegnivalents per gram (meq/g) of polymer active content. The amphoteric polyelectrolyte complex is generally most stable and useftal in combination with vinylamine-containing polymers when the net charge is in the range of from -2 meq/g to 1-2 cneglg, more preferably of from -1 mecllg to -t-1 inteq/g. The particle size is also an important parameter of the amphoteric polyclecarolyte complex. The complex is most useful when the particle size ranges of from 0.1 microns to 50 microns, more preferably from 0.2 to 5 microns. Other guidelines for active polymer solids, the preferred methods for adding the acrylarnide-containing polviner to the pulp slurry, and the ratio of the vinylanmiac=containing polymer to the acrylautide-containing polymer apply to the total formulation of the actylamide-containing polyelectrolyte complex, not only the acrylamide-containing polymer portion of the complex.

[0038] The act.ylamide-containing aqueous solution polymer, whether it is characteristically a cationic polymer, amphoteric polymer, or amphoterie polyelectrolyte complex as defined above, most effectively enhances the dry strength of a paper product when its molecular weight is greater than 75,000 daltons. A molecular weight less than 75,000 daltons is not easily retained in the sheet, and above all does not endow paper with significant dry strength properties, although it could be manufactured in such a way is to have a polymer solids content above 50% on a % eight basis. However, an acrylamide-containing polymer of greater than 1,500,000 daltons, and especially greater than 2,500,000 daltons may shove significant drawbacks. Although at lower dosages, such high molar mass polymers may give wood drainage performance, attaining high dry strength typically requires higher dosages of polymers. Such a polymer can significantly overflocculate the sheet when added at a dosage that might significantly impact dry strew-igth, thereby resulting in poor formation anchor poor dry strength. to one embodiment, the molecular- weights of the cationic or amphoter-ic acrylan,ide-containing aqueous solution polymers can be in the range of from 7 5,000 to less than 1,500,000 daltons, or can be from 100,000 to less than 1,250,000 daltons, or can be from 100,000 to less than 1,000,000 daltons. Moreover, it polymer of this molecular weight is generally synthesized via emulsion or reverse emulsion polymerization, thereby adding significant cost, inconvenience, and environmental and safety risk. For instance, oil or other hydrocarbon, such as mineral oil, is required in the formulation of a reverse emulsion product which acids significant cost to the product but does not by itself add value to the product; significant additional make-down equipment used to store, agitate, dilute, and invert the emulsions; additional chemicals are needed to break or invert the emulsion; and emulsion- or reverse elnillsion-type polymers also contain significant amounts of Volatile organic cotnpounds, creating a significant health arcdior safety hazard. An aqueous solution aeaylamide-containing polymer of molecular weight greater than 1,500,000 daltons may in theory be achieved in a product; however, such a product would likely be less than 5%
o polymer -solids, rendering= such a product less useful, cost effective, and convenient to a papernial e-r, or would be made be of such a high viscosity that the product handling would be extremely difficult. Thus, a practical relationship between the total polymer solids and molecular weight generally exists and a general correlation can be drawn between these parameters and polymer performance.

[0039] in one embodiment, the acrylamide-ecntai.ning polymer is an aqueous dispersion polymer. Acrylamidc-containing polymers made by way of aqueous dispersion polymerization of either a cationic or anlphoteric nature are of special practical importance when combined with vinylamine -cotitainirtg polymers. Specific examples are described in U'S Patent No. 7,323,510 as well as US Patent Publication No. 2008,0033094. `
hese aqueous ii WO 20111090672 PCT/17s2010/061750 solution polymers may have molecular weights of from 300,000 daltons to 1,500,000 daltons, or from 400,000 daltons to less than 1,250,000 daltons, while maintaining polymer solids content of from. 10% to 50% on a weight basis. These polymers are of a molecular weight that is somewhat less than traditional flocculants, and are thus less effective than higher molecular weight acryla.nide containing polymers as retention and drainage polymers at low dosage levels, but may generate excellent drainage performance when used at dosage levels adequate for dry strength enhancement without overffiocculating a forming cellulosic sheet.
Without wishing to be bound by theory, the interaction ofvinylansi,_e.--containing polymers either with aqueous dispersion aezvlamide-containing polymers or with other components of a paperrnaking system including but not limited to oxidized starch, heanicellulose, or anionic trash. may create especially extensive hydrogen-bonding networks, providing additional dry strength to a paper product without any substantial negative effects On the drainage performance of the papermaking system.

[00401 The viny lamine-containing polymer and the acrylamide-con taiflirt g polymer may be combined together in a single.-prod.iuct blend. Ratios of the vinylamine-containing polymer to the acrylamide containing polymer range of from 10:1 to 1:50, more preferably in the range of fi=oni 5:1 to 1:10, more preferably in the range of from 3:1 to 1:5, most preferably in the range of from 2:1 to 1:4.

[00411 Total amounts of the polymer blend may be added to the pulp slurry in the wet end of the paper machine in amounts of from 0.05% to 1.25% of the weight of dry pulp on a total polymer solids basis. Blends can be made with vinylamine containing polymers and either cationic or amphoteric acrylannide-containing polymers, but most preferably with cationic. acrylamide-containing polymers. Withoutwrishing to be hound by theory, annionic components of amphoteric a iylalnide-containing polymers may interact in all ionic fashion with cationic components of vinylatnine-c(ntaisningpolymers, particularly primary amine groups, to form gels and hi h viscosity products that are not useful for paper-naking.
Without wishing to be bound by theory, polymers containing cationic monomers with ester groups, for example, 2- [(acryloyloxy)ethyl;ltricnethylamrnonirrni chloride, can react in aqueous solutions with primary amine groups in the vinylamine-containing polymer to form amide groups, or can hydrolyze to generate the above-mentioned anionic moieties, either of which may form a gelled or prohibitively high viscosity product which is not useful in papernraling. Moreover, the hydrolysis of the relatively expensive cationic acrylate group represents a significant financial loss when considering the cationic aciylanii.de-containing polymer. Without wishing to be bound by theory, amide-containing cationic monomers, such as 3-(a cry] arrtidopropyl)trime thylarTmonium chloride or diallyldintethylamrnouiurrt chloride (1:3A_DivMAC) are resistant both to hydrolysis in aqueous solutions as well as reaction with primary amine groups, making them preferred as cationic monomers in the aciylamide-containing polymer to be blended with the vinylamine-containing polymer.

[0042] Vitrylaraine containing polymers and acrylamide-containing polymers can be added during the papermakinz process in the wet end either in the thick stock, or in the thick stock; either before or after a shear point. The acivlamide-con taining polymer may be added first in the wet end of the paper machine, followed by the vinylaminc-containing polymer; the acrylamide-containing polymer may be added at the same point separately in the wet end of the, paper machine as the vinylaniine-containing polymer; the acaylamide-containing polymer may be added at the same point in the wet end ofa paper machine as a single product 'blend;
or, more preferably, the yinyfamine-containing polymer may be added first in the wet end of the paper machine, followed by the acrylamide-containing polymer. The vinylantine-containing polymer is not reacted with starch prior to addition to the pulp slurry.

[0043] The vinylainine-containing polymer and the acrylarnide-containing polymer may be added to the wet end of a paper machine in a ratio of from 1:50 to 10:1 of vinylarnine-containing polymer to acrylamide-containing polymer as a ratio ofpolyrier solids; more preferably in a ratio of from 1:10 to 5:1, more preferably in the range of from 1:5 to 3:1, most preferably in the range of from 1:5 to 2:1. Total amounts of the polymer blend may be added to the pulp slurry in the wet end of the paper machine in amounts of 0.05% to 1.2534% of the weight of dry pulp on a total polymer solids basis.

[0044] In another embodiment, this invention can be applied to any of the various grades of paper that benefit froni enhanced dry strength including but not limited to linerboard, bag, boxboard, copy paper, container board, corrugating medium, file tbdder, ttewsprirtt, paper board, packaging board, printing and writing, tissue, towel, and publication.
These paper grades can be comprised of any typical pulp fibers including groundwood, bleached or unbleached Kraft, sulfafe, semi-mechanical, mechanical, semi-chemical, and recycled. They may or may not include inorganic fillers.

[0045] The embodiments of the invention are defined in the following Examples.
It should be understood that these Examples are given by way of illustration only. Thus various modifications of the present invention in addition to those shown and described herein will be apparent to those skilled in the art from the foregoing description. Although the invention has been described with reference to particular means, materials and embodiments, it is to be understood that the invention is not limited to the particulars disclosed, and extends to all equivalents within the scope of the appended claims.

EXAMPLES
[0046:1 Polyvinylamine is abbreviated as PVAm. Size exclusion chromatography (SEC) was used to measure molecular weight. The analysis was accomplished using gel permeation columns (CATSEC 4000 + 1000 + 300 + 100) and Waters 515 series chromatographic equipment with a mixture of 1 % NaNO3/0.1 '%o Trifluoroace.tic acid in 50:50 H20:CIIC7jNI as the mobile phase. The flow rate was 1.0 mL/nlin. The detector was a Hewlett[ Packard 1017A differential refractometer. Column temperature was set at 40 C and the detector temperature was at 35 `C. The number average (elfõ) and weight average molecular weight (,'IA,) of the polymers were calculated relative to the commercially available narrow molecular weight standard poly(2-vinyl pyridine).

[0047] The net charges or charge densities (Miitek) of the ionized polymers in the present invention were measured at pH 7.0 using a colloid titration method.
Charge density (meq/g) is the amount of net charge per unit weight, in miliiequivalents per grain of active polymer. The polymer sample is titrated with a titrant of opposing charge. For net cationic polymers, the titrant used is potassium polyvinyl sulfate (PVSK), and for net anionic polymers the titrant used is polydimethyldiallylammonium chloride (DADMAC).
The titrant is added until a 0 mV potential is achieved using an autotitrator (Brinkmann Titriuo) at a fixed titration rate (0.1 ml./dose, 5 sect and a tvlatek particle charge detector (Model PCD 03, ETC, Mtitek Analytic Inc., 3141 Kingston Ct., :Marietta, GA, USA) signifying end point detection.

[0048] Linerboard paper was made using a paperrnaking machine. The paper pulp was a 100 % recycled medium with 50 ppm hardness, 25 ppm alkalinity, 2.5 % GPC

oxidized starch (Grain Processing Corp., Muscatine, TA) and 2000 uSicm conductivity. The system pH was 7.0 unless indicated otherwise, and the pulp freeness was about 380 CSF with the stock temperature at 52 "C. The basis weight was 100 IN per 3000 fat.
Unless otherwise indicated, Stalok 300 cationic starch (fate & Lyle PLC, London, UK) and PerFornr'~z PC
8713 floeculant (Hercules Incorporated, Wilmington, DE) were added to the wet end of the paper machine in the amount of 0.5% and 0.0125% of dry pulp, respectively.
Vinylamine-containing and acrylam ide-containing polymers as described in the above examples were added as dry strength agents to the wet end of the paperniaking machine at the indicated levels, expressed as a percentage of weight of polymer active versus dry paper pulp. It is generally accepted that the dosages typically used for dry strength polymers on the pilot paper machine are much greater (i.e. at least double) what a commercial paper machine may use. Ring crush, dry Mullen burst, and dry tensile tests were used to measure the dry strength effects. All city strength results are expressed as a percentage of the dry strength of paper made without a dry strength resin.

1-00491 Drainage efficiency of the various polymeric systems was compared using one of two tests. One test is the Canadian Standard Freeness (CSF) Test. The dose of polymer active varied as is indicated in the tables. The results are sununarized in the following tables and the drainage performances of these compositions are expressed as percentage increase over the blank.

[00501 Another method for evaluation of the performance of the drainage process is the vacuum drainage test (VDT). `.the device setup is similar to the Buchner funnel test as described in various filtration reference books, for example see Ferry's Chemical E'ngineers' Handbook, 7th edition, (McGraw-Hill, New York, 1999.) pp. 18-78. The VDT
consists of a 300-ml magnetic Gelman filter funnel, a 250-ml graduated cylinder, a quick disconnect, a water trap, and a vacuum pump with a. vacuum gauge and regulator. The VDT test was conducted by first setting the vacuum to 10 inches Hg, and placing the funnel properly on the cylinder. Next, 250 g of 0.5 wt. % paper stock was charged into a beaker and then the required additives according to treatment program (e.g., starch, vinylarnine-containing polymer, actytamide-containing; polymer, locculants) were added to the stock under the agitation provided by an overhead mixer. The stock was then poured into the filter funnel and the vacuum pump was turned on while simultaneously starting a stopwatch. The drainage efficacy is reported as the time required to obtain 230 nil, of tiltrate. The results of the two drainage tests were normalized and expressed as a percentage of the drainage performance observed versus a system that did not include the vinylatnine-containing and acrylamide.-containing polymers.

[0051, Polymer A is a vinylatnine-containing polymer such as Hercobond % 6363 (available from Hercules Incorporated, Wilmington, DE) with a molecular weight in the range of 100,000 daltons to 500,000 daltons with an active polymer solids content of 9% to 15%, an N-vinylforma_nide charge off om 75% to 100%, with a range of hydrolysis from 50% to 100%.

[00521 Polymer B is a vinylamine-containing polymer such as such as flercobond 6350 (available from Hercules Incorporated, Wilmington, DE) with a molecular weight in the range of 100,000 daltons to 500,000 daltons with an active polymer solids content of 9% to 15%, an N-vinylformamide charge of from 75% to 100%, with a range of hydrolysis from 301,/0 to 75%.

[00531 Polymer C is an amphotÃ;ric acrylaniide containing polymer such as Hereobond 1205 (available fivm Hercules Incorporated, Wilmington, DE) smith a molecular weight in the range of 100,000 daltons to 500,000 daltons with an active polymer solids content of 10% to 25% and a sure total monomer charge of anionic and cationic monomers of from 8% to 20% of the total monomer charge.

[0051] Polymer t) is a cationic acrvlanride containing polymer such as Hercobond 1200 (available from Hercules incorporated, Wilmington, DE) with a molecular weight in the range of 100,000 daltons to 500,000 daltons, an active polymer solids content of 10% to 25%n and a cationic monomer charge of 20% to 40%.

[00551 Comparative Polymer E is an anionic acrylamide-containing polymer such as Hercobond 2000 (available from Hercules Incorporated, Wilmington, DE) with an anionic monomer charge in the range of from 5% to 20%.

[0056] Polymer F and Polymer C are cationic acrylamide-containing aqueous dispersion polymers such as Praestaret 1(325 and 3(350, respectively (available from Ashland Inc., Covington, KY) with a molecular weight it, the range of 500,000 daltons to 1,500,000 daltons, an active polymer solids content of 20"+, to 45% and a cationic monomer charge of 10% to 40%.

[0057.1 Polymer 1-1 is an amphoteric acrylarnide-containing polyelectrolyte complex such as HercohondQ? 1822 (available from Hercules incorporated, Wilmington, DL) with a molecular weight in the range of 100,000 daltons to 500,000 daltons with an active polymer solids content of 10% to 25%, and a net charge of from -2 mneq/g to 2 n?egi'g.

[0058] Polymer K is a cationic acrylamrmitle-containing polymer such as Praestamin Cf., (available from Ashland Inc., Covington, KY) with a molecular weight in the range of 100,000 daitons to 400,000 daitons with an active -polymer solids content of 15% to 30x1,.
The cationic coznononler in Polymer K is 3-(acrylanridopropyl)lri-urelllylaliunoln.ium chloride.
Polymer K. can be blended with vinylamine-containing= polymers such as Polymer A and Polymer B to form a single product.

EXAMPLE I
[005911 Table 1 shows the results or a pilot paper machine trial using Polymer A, airpholeric Polymer C. and cationic Polymer D. Thy nil of the system was adjusted to 6.5.
Alum (Croydtnr, PA) and HipHase 35 rosin sire (Hercules, Inc., Wilmington, DE) were used in the amount of 0.5% and 0.3% of dry pulp, respectively. OptiPlus 1030 amphoteric starch (National Starch, Bridgewater, N.J) was added in the place of Stalok 300 cationic starch, still used at 0.5% of dry pulp.

Table 1. Strength and drainage properties of paper made with Polymer A and an acrylaenidc containing polymer.

Entry Add lire I `:u Additive 2 % Dry `t'ensile Dry Mullen Burst Xing, Crosh Drainage 100 100 100 1(10 Polymer A 0.050 -- 102.4 106.2 105.7 1 i 0 ..................... ----------- -----------------.............................. ........................ 3 Polymer%, 0.125 -- -103.2 110.1. ?08.7 131 4 -- Polymer C 0.100 104.5 105. 104.8 107 -- I olymer C 0.250 163.5 i 13.0 110.1 11 e 6 Foly er A 0.090 Polyrorr C 0.100 1618 108.0 1110-4 121 .._.._........-_..-.._.......-_ -...................._............._....._.........._...._............._...__...
.....__..._........__.....
7 Polymcr A 0.125 Polymer C 0.100 11-.8 i 16.S 112.E 142 8 Polvu,er A 0.088 Polymer C 6-175 106,5 i I2.7 117.5 137 --------------- --------------------- ............. - .......... ...._...---------- .... ......
9 Polymcr: A 0.05(1 1'oiS'r.icl'C. 6.250 11 )s :011).2 114.2 121 (0 Polyaacc A 0. i 25 Polymer t `. 0-250 108.9 121,0 1111).9 153 _2-9,

11 .......... ---....... ....... _.------ --Polymer-- .1_7 . _.. 0_.._....---------103--- .2 - -- 9-3-1 ----------------...._.Ø4..6 ---------_----_1.9 .. .100 1

12 -- Polvune-r D 0.250 106.5 106.2 109.9 150 -- ---- - ------------------------.... ----------..... .......... ....--------------------------- ----- -------..-..--; -- ....

13 PolymcrA 0.05(1 Polymer)) 0.100 1103.2 98.2 107.0 137

14 Polyne:rA 0.125 PolymÃri) 0.1.00 105.1 1083 111.4 137 -------------------------- ------ .. ....................
i:, Polymer A 0.085 Polymer D OA 75 75 107.7 1:3.0 110.9 1511 ----------- ------------1u PolymerA 0.050 Pol-ymer1) 0.250 104.6 107.'1 1'09.5 142 ............ ......... ................ _..... .......-............................... _................ .................---...._.............-.._....
17 Polymer A 0.125 Polymer D 0.250 106.8 17A 107.2 147 [00601 Table l shows that strength could be markedly improved by addition of the acrylantide-containing polymer, and that drainage perfoiniance was maintained if not improved by adding more of the acrylamide-containing polymer, It is noted that the dosages typically used for dry strength polymers on the pilot paper machine are much greater (i.e, at least double) than what is curllparably effective on a commercial paper machine . For example i'0.10 % of additive is an effective, amount for o dry strength polymer on the pilot paper machine then. the effective amount on the commercial machine would be about 0.05%
or less.

[0061] Table 2 slows the drainage performance ol'three different acrylamide-containing polymer additives using the same wh:itewater and pulp as indicated in the strength testing illustrated in Table 1. The drainage performance was evaluated using the CSF test as indicated above. Entries 18 to 23 are shown for comparison.

Tabla. 2 t}radAtigr proprrtics of pitl1) inade able} vans' s acA-yt;noidc-rantaiairig Iad yinars w ills Polymer Entry Additive t. % of drypull Additive, 2, 9b of dry pulp % of drainago _-___..--...... .-------.-2 P~lymerA 0.0 ..0 - -- IiO
3 Polymer A 131 PolymerC 0.100 ICI%
-------------------------------------------------------------------------------- ------------Polymer C 0.230 1 t0 6 Polymer A 0.050 1' tyn.ec C 0.100 121 7 Polymer A 01.125 Polymer C 0.100 142 8 Polyr.~=r A 0.000 Pot; n e' C 0.1 7 5 137 9 Polymer A 0.050 Polymer C 0.250 121 Polyn,er A 0.125 Polymer C 0.250 1: 3 1 I Polymer D 0.100 129 ---- -------- ----- --------- ------ _------- ............ .-.---..-_.._......_.....---....----..-----------------------------__...-.._....--- --......--------12 Polymer D 0.150 150 13 Polymer A OA50 Poly-mmer D 0.100 137 .... ........... ............-.._...........-=---....._.........._......._.._......._.._..-..._......_.._..._.._.._................-._......-- -- ....
14 Polymer A 0.125 Polymer r) 0.100 137 Polymer A 1058 i'olymer D 0.175 I50 --- ----_------ __--'_-_----------------------,------------------ ..----.-._._...--- ---- ---------.._._... __.--16 Polymer A 0.050 Polymer D 0.250 142 17 Polymer A Ø 123 Polymer 0 0.250 1,47 is 1S Comparative Polymer 13 0.100 96 14 CompanaticePolytncr1. 0250 94 20 Polvmcrfr 0.050 Comparative Polymer 13 (1.100 110 21 Polymer A 0.125 Comparative Polymer E 0-100 134 22 Polymer A 0.088 Comparative Polymer It 0.175 l 13 23 Polymer A 0 050W_ Comparative Polymer Ti - 0.2 50 104 24 Polytn:r A 0.125 Comparative Polymer E 0.250 134 [0062] Table 2 demonstrates that the drainage performance of the pulp slurry is weaker when the anionic acrylamide-containing polymer (Comparative Polymer E) is used compared to the amphot.eric and cationic acrylamide-containing polymers (Polymer C and Polymer D). It is noted that the dosages typically used for dry strength polymers on the pilot paper nlaclline are. much greater (i.e. at least double) than what is comparably effective on a coiiunercial p>_3per machine. For example if 0.10 % of additive is an effective amount for a dry strength polymer on the pilot paper machine then the effective amount on the conunercial machine would be about 0.05% or less.

[0063.1 Table 3 shows results of a pilot paper machine trial using a vulylamine-0ntaming polyÃl'ret- an(d a cationic acrylan-nde conttainiing poli=mer-. In this example, as in all following examples, the p; l was (nai-ntained at 7.0, no alma was included in the furnish, and no sizing agents were employed.

Table 3. Results of pilot paper trtacbiuc trial at i?117.0 and in the presence of Polymer B and cafiniile act slatiaicle-critat.riniti!; Polymer D.
k;ntry- Additive 7 "1 Additive 2 Dry'rensiie Dry Mullen lfttrst Ring Crasit Draiaaag.

............................. ............................ .... ..---------------2 Polymer B ;.100 96.3 9i 7 100 9 f5 3 Polymer B 0.300 102.5 104.0 112A 137 - ....-...
------------- --------------- ............... ..................
4 Polyme. t) 0.100 104.5 108.6 1(17.1 104 Polymer D 0.300 105.7 1074 106.0 115 6 Polymer B 0-100 Polymer D 0.100 100.8 95.2 105.6 134 7 Polymer B 0-300 Polymer D 0.100 110.1 109.9 116-6 120 ....;7- ....................._......__........_.._..
_..._...._......._......__..._-......_......._.-------- ----- --r- ------....__-- _.._.._......_-_......._..-----8 Polymer B 0.200 Polymer D 0.200 112.9 115.8 1 19.9 118 9 Polymer B U-100 Polynerl) 0-300 115_'1 12, C0 113,7 1 i5 --------..-------= ...._._._........
i 0 Polymer B 0.300 Polymer D 0.300 110.4 120 2 111.3 112 [0064] Table 3 demonstrates that high dosages of the two polymers, excellent strength performance can he achieved when the two chemicals were added together compared to their performance alone. This method allows the paperl-naker to achieve greater efficiency in chemical use, and the added strength achieved when the two chemicals are.
added together allows the papermaker to reduce the usage of the expensive vinylamine-containing Polymer B. It is noted that the dosages typically used for dry strength polymers on the pilotpaper machine are much greater (i.e. at least double) than what is comparably effective on a commercial paper machine. For example if 0.10 % ofadditive is an efective amount for a dry strength polymer on the pilot paper machine then the effective amount on the commercial machine would be about 0.05% or lass.

[0065] Table 4 shows a pilot paper machine trial employing an amiphoteric acrylarnide-containing polymer in combination with the vinylamine-containing polymer.
This trial was pertbrmed under conditions similar to Example 3 above. However, in this case, the amphoteric acrylanlidc-containing Polymer C was used, rather than the cationic acrylanmle-containit1iQ. Polymer El.

Table 4. Results of pilot paper machine trial with Polymer Rand amphoteric acrytamide-contnhtitrg Polymer C.
Entry Additive I % Additive 2 % Dry 1'ensiÃe Dry Morten Burst Ring Crush Drsinage -- -- - ton too 100.0 too Polymer B 0.1010 ... .. 98.9 104.7 ;02.2 105 -------- _-------------...._..-..------3 Polymer B 0.3300 -- 1043 123.5 103.0 143 ---4 ~_. - -- PoiymerC 0.101) 100.4 03.0 `:02.4 102 -- -- PotymerC 0.300 100.9 101.9 103.9 109 ................... ..................................................... ....
...._.. _._........... ...._......_.._ _......-'------'---_...----------"---- ----------------- ..._._.... _...............
F Polymer B 0.100 Polymer C 0.100 102.1 104.1 104.1 95 ............ ......................... .. -............................................._.........--- --'-'-- - ---------7 Polyriez' $ 0.300 Polymer C 0.100 10 11.2 i 16.4 110.'1 142 8 Polymer B 0,200 Potymcr C 0300 103.3 112.3 109.8 119 --- .__-........-- ------------- ------------------- ------------- ._...--------- - -..._..----._._...._.... ...---------- --- --- ----- --- ---------9 Polym r B 0.100 Polymer C 0300 103.0 11'.'..4 105.3 105 Polymer B 0.300 Polymer C 0.300 106 i 07.9 117.1 131 [0066] I-able 4 shows that Mullen Burst and Ring Crush can be especially enhanced with the treatment with the two polymers in tandem versus the polymers in isolation. The drainage performance was affected only marginally. It is noted that the dosages typically.

WO 2011/090672 PCT/U52010/0617.50 used for dry strength polymers on the pilot paper machine are much greater (i.e, at least double) than what is comparably effective on it commercial paper machine. For example if 0.10 % of additive is an effective amount for a dry strength polymer on the pilot paper machine then the effective amount on the commercial machine would be about 0.05% or less.
EXAMPLE 5.
[0067;1 Table 5 shows the effect of combining aqueous dispersion polymers with the vinylamine-containing Polymer 13.

-'3tfle 5..4E1<titiofa of aqueous dispersion Polymers 1 and to to Folymer 13 to achieve ezthancett strength Entry pct<iitlyc I % Additive 2 54 3arq Tensile illy- Mullen Burst icing (:nisei Drainage 2 Polyracr B 0.100 99.0 107.6 105.4 1 17 3 Polymer 73 0 300 - 101.3 109.8 107.7 138 4 -- -- PolymerF 0.100 101.0 105.3 144.0 124 ....- ._.._...
.............. -------------------------- ................- --------------._.......................... ..... ................ .....................
.._..._...............
Polymer F 0 300 10231 102.4 110.0 135 6 Polymer B 0.1O0 Polymer F 0.100 97.5 104.6 104.1 135 7 Polymer 14 0.3011 Polymer F O.100 104.2 111.8 111.0 135 8 Polymer 13 0.2 D0 Polymer F 0:200 1(14.1 116.9 1103 140 9 Polymer 15 0.100 Polymer F 0.300 1055 i 10.4 109.1 157 --------0 Poly mer B !'300 ?nl vmer F 0 300 108.3 19.2 114.6 125 11 - Polymer G 0.100 956 9561 102.' 123 Polymer G 0.300 99.5 10.%.3 101.2 15 i l3 Polymer l3 0. i 00 Polymer G 0.100 101.1 :01.0 106.7 134 E4 Polymer B 1}.300 Polymer G 0.100 104.9 i 155 W~ - 108.9 142 Polymer B 0.200 Poyymm G 0. %00 103.6 114.8 110.2 145 i 6 Polynmrr B 0. 11M Polymer G 0.300 109.4 :09.7 106.7 15-; 17 Polymer B
0.300 Polymer 0 0.300 107.2 T- 150.0 111.7 139 [0068] 'fable 5 demonstrates that drainage can be maintained while achieving significantly enhanced levels of dry strength With aqueous dispersion polymers. Ibis noted that the dosages typically used for dry strength polymers on the pilot paper machine are much greater (i.e. at least double) than what is comparably effective on a commercial paper machine. For example if 0.10 % of additive is an effective amount for a dry strength polymer on the pilot paper machine then the effective amount on the commercial machine would be about 0.05% or less.

[00691 Table 6 shows the combination of vinylamine-containing Polymer 13 with an amphoteric acrylamid.e-containirgr polyelÃctrolyte complex Polymer H.

Table 6. Pilot paper machine trial osi)ng an amplnaterie acrylamide.eotrt;tining polyeieetrolytc eotaplts Polymer. 1Ã with Polymer B.
Entry 1'olynrer it added (%) Polymer 11 added (%) Dry Tensile Dry Mullen Bum Ring Crnlx ----------- -0 0 0.0 100 loo ! 00 2 0.0 99.9 100.8 100.6 3 0.0 0.4 101.1 104.0 1019 4 0.0 0.6 103.6 101.5 - -----------0.1 t 97.7 97.0 ..... ..... ............_.._..................__..-...._.._._..__._ 6 0.1 0.2 96.6 93-8 100.9 ........................ _......._.___.._....... -- -................ .... -........ ............................. ................. --............. -'r---.........-.._--...------"--0.1 0.4 102A 102-9 11)0.9 8 0.1 0.6 102.0 103.5 102.3 --------------------- ------ --------- ---.-_..------ -------------- --------------------------------- -------------- ------------------------------- -----..-..-...
9 D.2 0.0 96.6 97.8 101.4 0.2 0.2 101.8 107.3 101).1 ................----....._....--------- --.....-.---..._-....._._._..............-- ......................-............................_.-_........................... ..... ...... -11 0.2 0.4 I09 109.5 110-3 12 0.2 0.6 110.4 114.4 112.4 ............... ...._ ................................ ...... .............
...................................._....._..._-----......_..----........---------------...........'---.............
1.3 0.3 0.t) 97.5 102.4 105.3 14 0.3 02 107.4 116.0 112.6 --- -- ---------------- ------ ---0.3 0.4 1156 122.1 115.1 I6 0.3 0.6 114.1 111.6 116.2 [0070] Table 6 shows that results comparable to amphoteric acrylami.de containing polymers can be achieved by using the amphoteric acrylamide containing polyelectrolyte complex. Excellent dry strength levels were achieved, at additive levels at which performance typically begins to level off. It is noted that the dosages typically used for dry strength polymers on the pilot paper machine are much greater (i.e. at least double) than what is comparably effective on a commercial paper machine. For example if 0.10 `.%
of additive is an effective arnoultt for a dry strength polymer on the pilot paper machine then the.
effective amount on. the commercial machine would be about 0.05% or less.

[00711 Table 7 shows dry strength and drainage testing results using a single product blend of Polymer K. and Polymer R. Regardless of the ratio of the two polymers in the blend, the additive was used at a dosage level of 0.3% versus the dr~ pulp.

Table 7. Use of a single-product blend of Polymer K and B to achieve enhanced dry strength Fury Polymer K. Active solids Dry Dry Mullen thug Crush Wet Drainage Polymer E1 (%) Th,sile Hirst Tensile I 0:4 12.7 101.9 105.5 109.6 3 73.7 I59.6 2 L:3 14.6 105.7 110.7 109.4 3479 149.0 .-..._ . ................----..-...-- ---------------------- ------------------...-..
3 i:1 17.x. 107.9 ( 108.7 11)8.0 297.5 127.2 4 3:1 20.8 108.2 I 3 08.8 109.7 2009 109.0 [00721 Table 7 illustrates that using a single product blend of a vinylamine-containing polymer and a cationic acrylantide-containing polymer, imprmed dry strength results care be obtained in the dry tensile and dry inullen burst caÃegories while ofthring comparable ring crush results. The single product blend is especially useful in that it offers the papettnaker the ease of adding a single product to the paper machine, but the different blend ratios make it possible to tune the product to the paperfnaker's needs. 1 or instance, il' lower wet streai tlt is needed to reduce repulping energy, a single product blend can be made to meet that need ;.chile maintaining or improving dry strength properties. Or, if the paper machine is already running near its maximum speed, the. amount of drainage the product provides can be matched to the papennaker's need without compromising dry strength.
Furthermore, th.e single product blend can have a significantly higher active solids content without negatively impacting dry strength, thus reducing ecological impact due to transportation oflow solids content freight to the paper mill.

Claims (18)

1. A process for the production of paper, board, and cardboard with enhanced dry strength comprising adding to the wet end of a paper machine (a) a vinylamine-containing aqueous solution polymer having a molecular weight of from 75,000 daltons to 750,000 daltons and (b) an amphoteric or cationic acrylamide-containing aqueous solution polymer having a molecular weight of from 75,000 daltons to 1,500,000 daltons, wherein the sum of the anionic and cationic monomers comprises at least 5% on a molar basis of the composition of the acrylamide-containing monomer.

2. The process according to claim 1 wherein the active polymer content of the vinylamine containing aqueous solution polymer is from 5% to 30% on a dry weight basis and wherein the vinylamine-containing polymer has an N-vinylformamide content of at least 50% on a molar basis of the total monomer charged prior to hydrolysis, and at least 10%
of the N-vinylformamide has been hydrolyzed in the final polymer..

3. The process according to claim 1 wherein the vinylamine-containing polymer has a molecular weight of from 150,000 daltons to 500,000 daltons.

4. The process according to claim 1 wherein the acrylamide-containing aqueous solution polymer contains a sum cationic and/or amphoteric monomer charge of from 5% to 50%
on a molar basis, and has an active polymer content of from 5% to 50% on a weight basis.

5. The process according to claim 1 wherein the acrylamide-containing aqueous solution polymer is cationic and has a molecular weight of from 75,000 daltons to 750,000 daltons.

6. The process according to claim 1 wherein the acrylamide-containing aqueous solution polymer is an aqueous dispersion polymer.

7. The process according to claim 6 wherein the acrylamide-containing aqueous solution polymer is an aqueous dispersion polymer having a molecular weight of from 300,000 daltons to 1,500,000 daltons.

8. The process according to claim 6 wherein the acrylamide-containing aqueous solution polymer is an aqueous dispersion polymer having a molecular weight of from 400,000 daltons to less than 1,250,000 daltons.

9. The process according to claim 1, wherein the acrylamide-containing aqueous solution polymer contains a cationic monomer charge of from 5% to 50% on a molar basis, has an active polymer content of from 5% to 50% on a weight basis, and comprises a least one cationic monomer selected from the group consisting of :
diallyldimethylammonium chloride (DADMAC), 2-(dimethylamino)ethyl acrylate, 2-(dimethylamino)ethyl methacrylate, 2-(diethylaminoethyl) acrylate, 2-(diethylamino)ethyl methacrylate, 3-(dimethylamino)propyl acrylate, 3 -(dimethylamino)propyl methacrylate, 3-(diethylamino)propyl acrylate, 3-(diethylamino)propyl methacrylate, N-[3-(dimethylamino)propyl]acrylamide, N-[3-(dimethylamino)propyl]methacrylamide, N-[3-(diethylamino)propyl]acrylamide, N-[3-(diethylamino)propyl]methacrylamide, [2-(acryloyloxy)ethyl]trimethylammonium chloride, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, [3-(acryloyloxy)propyl]trimethylammonium chloride, [3-(methacryloyloxy)propyl]trimethylammonium chloride, 3-(acrylamidopropyl)trimethylammonium chloride, and 3-(methacrylamidopropyl)trimethylammonium chloride.

10. The process according to claim 4, wherein the acrylamide-containing aqueous solution polymer has an overall amphoteric charge.

11. The process according to claim 10 wherein the acrylamide-containing aqueous solution polymer is amphoteric and has a molecular weight of from 75,000 daltons to 750,000 daltons.

12. The process according to claim 10, wherein the amphoteric acrylamide-containing aqueous solution is comprised of a polyelectrolyte complex consisting of an acrylamide-containing aqueous solution polymer and a cofactor carrying a complementary charge.

13. The process according to claim 12, wherein the amphoteric acrylamide-containing aqueous solution is comprised of a polyelectrolyte complex having a molecular weight of from 100,000 daltons to less than 1,000,000 daltons.

14. The process according to claim 1, wherein the vinylamine-containing polymer and the acrylamide-containing polymer are added to the papermachine as a single product blend.

15. The process according to claim 14, wherein the cationic portion of the acrylamide-containing polymer is generated by at least one monomer selected from the group consisting of diallyldimethylammonium chloride (DADMAC), N-[3-(dimethylamino)propyl]acrylamide, N- [3 -(dimethylamino)propyl]methacrylamide, N-[3-(diethylamino)propyl]acrylamide, N-[3-(diethylamino)propyl]methacrylamide, 3-(acrylamidopropyl)trimethylammonium chloride, and 3-(methacrylamidopropyl)trimethylammonium chloride.

16. The process according to claim 15, wherein the cationic portion of the acrylamide-containing polymer is generated by at least one monomer selected from the group consisting of diallyldimethylammonium chloride (DADMAC), N-[3-(dimethylamino)propyl]acrylamide, N-[3-(dimethylamino)propyl]methacrylamide, 3-(acrylamidopropyl)trimethylammonium chloride, and 3-(methacrylamidopropyl)trimethylammonium chloride.

17. The process according to claim 1, wherein the vinylamine-containing polymer and the acrylamide-containing polymer are added to the wet end of a paper machine in a ratio of vinylamine-containing polymer to acrylamide-containing polymer of from 10: 1 to 1 :50 up to a sum total of 1.25% on a weight basis of the dry pulp, based on the active polymer solids of the polymeric products.

18. A paper product produced by the process of claim 1.