Patent Application
20150041090
Paper and paperboard are produced from an aqueous slurry of cellulosic fiber, depositing this slurry on a moving papermaking wire or fabric, and forming a sheet from the solid components of the slurry by draining the water. This sequence is followed by pressing and drying the sheet to further remove water.
Drainage or dewatering of the fibrous slurry on the papermaking wire or fabric is often the limiting step in achieving faster paper machine speeds. Improved dewatering can also result in a drier sheet in the press and dryer sections, resulting in reduced energy consumption. Chemicals are often added to the fibrous slurry before it reaches the papermaking wire or fabric to improve drainage/dewatering and solids retention; these chemicals are called retention and/or drainage aids.
Dry strength additives are used in paper mill to increase the strength of paper. It increases the strength of paper by increasing internal bond formation. Moreover dry strength additives improve bust strength, tear strength, wax pick values, folding endurance, stiffness, machine runnability, increase levels of paper filler uses etc. Dry strength additives also reduced linting and dusting.
Retention and drainage aids have reduced efficacy in some furnish substrates which contain high levels of soluble organics and salts. Two such examples of these furnishes are neutral sulfite semi chemical (NSSC) and kraft virgin linerboard, where high levels of soluble lignin and other organic materials containing a high anionic charge are present. These highly anionic materials neutralize the charge on the conventional retention and drainage aids, significantly reducing their effectiveness.
It has been discovered that treatment of cellulosic furnish with a polyethylene oxide homo polymer or copolymer (“PEO”) will improve the performance of the drainage or strength agents in cellulosic furnish that contain high levels of soluble lignin where the drainage or strength agents are not typically active. Soluble lignin levels in these cellulosic furnishes range from 25 parts-per-million (ppm) up to 500 ppm.
Without wishing to be bound by theory it is believed that the PEO reacts with the excess lignin and other excess anionic materials in the cellulosic furnish thereby allowing the drainage or strength agent to work without be hindering by reacting with the undesirable materials.
Molecular weights (Mw) are viscosity average molecular weight as determined from intrinsic viscosity determinations.
The PEO can be a homo-polymer of ethylene oxide, or a copolymer of ethylene oxide. Suitable comonomers include propylene oxide or butylene oxide. A homopolymer of polyethylene oxide is the most preferred. Additional suitable comonomers used to make the PEO copolymer can be cationic, anionic, non-ionic or hydrophobic monomers, and any mixture thereof. The molecular weight of the PEO homo-polymer or co-polymer can range from 1000 daltons up to 25,000,000 daltons or 100,000 to 15,000,000 daltons or 1,000,000 to 10,000,000 daltons. Examples of ethylene oxide containing homo polymers or copolymers are Ucarfloc™ 300, 302, 304, and 309 (available from Dow Chemical, Midland, Mich.).
The feed point of the PEO treatment can include the thick stock, thin stock, white water, or process water. The PEO treatment can be added at the blend chest, machine chest, fan pump, cleaners, centriscreen, save-all, white water tray and white water silo.
The PEO treatment dosage can range from 0.01 pounds (lbs) to 10 lbs of PEO polymer per ton of furnish solids. The dosage can also be based upon the furnish volume, ranging from 0.01 parts-per-million (ppm) to 10,000 ppm of PEO per volume of furnish or substrate water. The PEO is generally supplied as a dry powder or granular product, where it is dissolved at the application site. It can also be supplied to the end user as a slurry or dispersion for ease of use, where it can be diluted and fed into the process stream.
The drainage or strength agents, which will function due to the PEO treatment, are generally water-soluble or water-dispersible synthetic polymers, “synthetic polymer”. The synthetic polymers can be nonionic polymers, cationic copolymers or anionic copolymers.
The nonionic monomers used to make the synthetic polymer include, but are not limited to, acrylamide; methacrylamide; N-alkylacrylamides, such as N-methylacrylamide; N,N-dialkylacrylamide, such as N,N-dimethylacrylamide; methyl methacrylate; methyl acrylate; acrylonitrile; N-vinyl methylacetamide; N-vinylformamide; N-vinylmethyl formamide; vinyl acetate; N-vinyl pyrrolidone and mixtures of any of the foregoing. The invention contemplates that other types of nonionic monomer can be used. More than one kind of non-ionic monomer can be used to make the synthetic polymer. Preferable nonionic monomers used are acrylamide; methacrylamide, N-vinylformamide.
The cationic monomers used to make the synthetic polymer include, but are not limited to, cationic ethylenically unsaturated monomers such as the diallyldialkylammonium halides, such as diallyldimethylammonium chloride; the (meth)acrylates of dialkylaminoalkyl compounds, such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethyl aminopropyl (meth)acrylate, 2-hydroxydimethyl aminopropyl (meth)acrylate, aminoethyl (meth)acrylate, and the salts and quaternaries thereof; the N,N-dialkylaminoalkyl(meth)acrylamides, such as N,N-dimethylaminoethylacrylamide, and the salt and quaternaries thereof and mixtures of the foregoing. More than one kind of non-ionic monomer can be used to make the synthetic polymer. Most preferred are diallyldimethylammonium chloride and dimethylaminoethyl (meth)acrylate and the salt and quaternaries thereof and mixtures of the foregoing.
Poly(vinylamine) is also a suitable cationic synthetic polymer for the invention. The polyvinyl amine can be a homopolymer or a copolymer. One method of producing a polyvinylamine polymer is by polymerization of the monomer(s) followed by hydrolysis. The level of hydrolysis can be expressed as“% hydrolysis” or “hydrolysis %” on a molar basis. A hydrolyzed polymer can thus be described by as “% hydrolyzed.” Moreover the level of hydrolysis can be approximated. For the purposes of applicants' invention, a poly(vinylamine) that is referred to as “50% hydrolyzed” means from 40% to 60% hydrolyzed. Likewise, a poly(vinylamine) that is about 100% hydrolyzed means from 80% to 100% hydrolyzed. The hydrolysis reaction results in the conversion of some or all of the monomer(s) to amines, as controlling the hydrolysis reaction can vary the resultant percentage of monomers having amine functionality.
Examples of monomers used to make a poly(vinylamine) include, but are not limited to, N-vinylformamide, N-vinyl methyl formamide, N-vinylphthalimide, N-vinylsuccinimide, N-vinyl-t-butylcarbamate, N-vinylacetamide, and mixtures of any of the foregoing. Most preferred are polymers prepared by the hydrolysis of N-vinylformamide. In the case of copolymers, nonionic monomers, such as those described above, are the preferred comonomers. Alternatively, poly(vinylamine) can be prepared by the derivatization of a polymer. Examples of this process include, but are not limited to, the Hofmann reaction of polyacrylamide. It is contemplated that other synthetic routes to a poly(vinylamine) or polyamine can be utilized.
The molar percentage of nonionic monomer to cationic monomers may fall within the range of about 100:1 to 1:100, or 80:20 to 20 to 80, or 75:25: 25:75 or 40:60 to 60:40, where the molar percentages of nonionic monomers to cationic monomers must add up to 100%. It is to be understood that more than one kind of nonionic or cationic monomer may be present in synthetic polymer.
The anionic monomers used to make the synthetic polymer include, but are not limited to, the free acids and salts of acrylic acid; methacrylic acid; maleic acid; itaconic acid; acrylamidoglycolic acid; 2-acrylamido-2-methyl-1-propanesulfonic acid; 3-allyloxy-2-hydroxy-1-propanesulfonic acid; styrenesulfonic acid; vinylsulfonic acid; vinylphosphonic acid; 2-acrylamido-2-methylpropane phosphonic acid; and mixtures of any of the foregoing. Most common are the free acids or salts of acrylic acid, methacrylic acid, and 2-acrylamido-2-methyl-1-propanesulfonic acid. When a salt form of an acid is used to make an anionic polymer, the salt is selected from Na+, K+ or NH4. More than one kind of anionic monomer can be used to make the synthetic polymer.
The molar percentage of nonionic monomers to anionic monomers may fall within the range of about 100:1 to 1:100, or 90:10 to 30:70, or 40:60 to 70:30, where the molar percentages of nonionic monomers to anionic monomers must add up to 100%. It is to be understood that more than one kind of nonionic may be present. It is also to be understood that more than one kind of cationic monomer may be present.
The synthetic water-soluble or water-dispersible polymers can also be modified to impart additional properties to the synthetic polymer or to modify the synthetic polymer structure. Polymerization of the monomers can occur in the presence of a polyfunctional agent, or the polyfunctional agent can be utilized to treat the polymer post-polymerization. Useful polyfunctional agents comprise compounds having either at least two double bounds, a double bond and a reactive group, or two reactive groups. Illustrative of those containing at least two double bounds are N,N-methylenebisacrylamide; N,N-methylenebismethacrylamide; polyethyleneglycol diacrylate; polyethyleneglycol dimethacrylate; N-vinyl acrylamide; divinylbenzene; triallylammonium salts, and N-methylallylacrylamide. Polyfunctional branching agents containing at least one double bond and at least one reactive group include glycidyl acrylate; glycidyl methacrylate; acrolein; and methylolacrylamide. Polyfunctional branching agents containing at least two reactive groups include dialdehydes, such as glyoxal; and diepoxy compounds; epichlorohydrin.
Examples of synthetic polymers used in the invention include but are not limited to polyvinylamine, glyoxylated cationic polyacrylamide, and cationic polyacrylamide. Preferred are 100% hydrolyzed polyvinylamine, 50% hydrolyzed polyvinylamine and cationic polyacrylamide containing at least 10 mole % cationic monomer. One example would be cationic polyacrylamide containing at least 10 mole % diallyldimethylammonium chloride or 10 mole % dimethylaminoethyl (meth)acrylate. Additional useful polymers of the present invention include Perform™ products such as SP 7200 (anionic polyacrylamide polymer), (Hercules Incorporated, Wilmington Del. Hercobond™ 6350 (polyvinylamine copolymer polymer), Hercobond™ 6363 (polyvinylamine copolymer), Hercobond™ 6950 (polyvinylamine copolymer), Hercobond™ 1307 (modified cationic polyacrylamide), Perform™ PC 8181 (cationic polyacrylamide), Perform™ PC 8179 (cationic polyacrylamide).
The molecular weight of the non-ionic, cationic, or anionic polymers can range from 10,000 to 50,000,000 daltons, or 1,000,000 to 25,000,000 daltons, or 5,000000 to 20,000,000 daltons.
The treatment is effectuated by adding the PEO to the cellulosic furnish (slurry) at a feed point in the papermaking system and adding the water-soluble or water-dispersible synthetic polymers to the treated slurry. The PEO and the synthetic polymers can be added at the same feed point or different feed points. The PEO and the synthetic polymers can be added simultaneously, individual or as a blend. In one embodiment the PEO and the synthetic polymers can be added in sequence to the papermaking system. The slurry is then drained on the papermaking wire to dewater the fibrous slurry and to form a sheet. Improved drainage is observed when the PEO and the synthetic polymers are used in conjunction with one another.
Less synthetic polymer can be used while still maintaining the same performance level (drainage) when the PEO is used in conjunction with the synthetic polymer.
The feed point of the synthetic polymer can include the thick stock or thin stock. Potential addition points of the synthetic polymer can include the blend chest, machine chest, fan pump, cleaners, and before or after the centriscreen. The synthetic polymer dosage can range from 0.01 lbs to 10 lbs. of active polymer per ton of furnish solids or 0.01 to 5, or 0.05 to 5, or 0.1 to 2 lbs. of polymer per ton of furnish solids. The synthetic polymer can be manufactured and supplied to the end user as a dry or granular powder, an aqueous solution or dispersion, or an inverse emulsion.
The weight ratio of the PEO to synthetic water-soluble polymer can range from 100:1 to 1:100 or 80:20 to 20:80 or 50:50 to 10:90.
Suitable cellulosic furnish or fiber pulps for the method of the invention include conventional papermaking stock such as traditional chemical pulp. For instance, bleached and unbleached sulfate pulp and sulfite pulp, mechanical pulp such as groundwood, thermo-mechanical pulp, chemi-thermomechanical pulp, recycled pulp such as old corrugated containers, newsprint, office waste, magazine paper and other non-deinked waste, deinked waste, and mixtures thereof, may be used. The pH of the cellulosic furnish or slurry may range from 4 to 8.
A series of drainage experiments were conducted utilizing a paper machine pulp slurry comprising neutral sulfite semi-chemical (NSSC), virgin kraft, and old corrugated containers (OCC). The drainage performance of the inventive process was evaluated using a vacuum test, where a Buechner funnel is affixed atop a graduated cylinder. 500 milliliters (mls) of the pulp slurry is mixed in a beaker using a mechanical overhead mixer, and the noted polymer treatment are added sequentially. The time required to collect the noted amount of filtrate is recorded, where a lower time is representative of the desired faster drainage. The PEO is a high molecular weight (7 million) homopolymer and Hercobond™ 6950 is a cationic modified polyamine water soluble polymer, (Hercules, Wilmington Del.). The data in Table 1 demonstrated no drainage response with the Hercobond™ 6950 compared to the untreated system. A drainage response is noted with the PEO. A high drainage response is noted by the inventive process, where the pulp slurry is treated first with the PEO, followed by the addition of the Hercobond™ 6950.
This application claims the benefit of U.S. provisional application No. 61/864,262, filed 9 Aug. 2013, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61864262 | Aug 2013 | US |
