BRPI0610071A2 - process for preparing a polymer dispersion and a polymer dispersion - Google Patents

Abstract

PROCESS FOR PREPARING A POLYMER DISPERSION AND A POLYMER DISPERSION. The present invention relates to a process for preparing a polymer dispersion comprising polymerizing one or more water-soluble (m 2 -) ananolic monomers and one or more nonionic (m 2 -) vinyl monomers present in a reaction mixture further comprising a polymeric stabilizer (B) and a polymeric co-stabilizer (C). It further relates to a polymer dispersion, the use of polymer dispersion, and a papermaking process.

Description

"PROCESS FOR PREPARATION OF A POLYMER DISPERSION A POLYMER DISPERSION"

The present invention relates to a process for preparing a polymer dispersion. It also suits a polymer dispersion, the use of polymer dispersion, and a papermaking process.

Background of the Invention

An important use of aqueous dispersions of anionic charged polymers is retention aids and dehydration aids in the papermaking industry. Additional uses of such polymer dispersions are as adjuvants in various processes where they act as, for example, flocculants when it comes to pouring water, or assistants in other solid-liquid separation processes, for example in the metal, ceramic, printing, biotechnology industries. and pharmaceuticals. They may also be used as thickeners, for example in the chemical-biotechnology, pharmaceutical, eco -metics, and soil improvement agents.

Generally, these polymer dispersions comprise a dispersed polymer and a dispersant wherein the dispersant is usually a polymeric dispersant.

Anionic polymer dispersions are generally prepared by polymerizing a water soluble anionic and nonionic demonomer reaction mixture in the presence of a salt. The finished polymer will precipitate from the aqueous salt solution and, by use of a suitable dispersant, forms a stable polymer dispersion. WO 01/18063, US 5,837,776 and US 5,605,970 disclose processes for preparing a dispersion of a water-soluble polymer comprising water-soluble polymerisers in an aqueous reaction mixture containing a salt.

Factors to consider are, for example, process viscosity, active content, stability, good retention properties, and ease of preparation of polymer dispersion sometimes including stabilizer preparation. Also, criteria such as environmental and safety aspects are of importance.

There are a number of criteria that the polymer dispersion must meet to give good results in the final application and are of commercial interest. Such criteria are, for example, low production costs, fast performance, effective flocculation or dehydration, and long service life.

Anionic polymer dispersions of the prior art contain significant amounts of salt which make up a large part of the weight of the polymer dispersion. There is currently a desire to reduce, or completely avoid, the use of salt in polymer dispersions due to environmental and economic reasons.

The viscosity of the reaction mixture when producing polymer dispersion, "process viscosity" must be kept low, and viscosity peaks should be avoided, or at least reduced as much as possible, during the production of the polymer dispersion.

Dispersion life, that is, the stability of polymer dispersion over time, is an important property. An efficient dispersant is required to keep the polymer particles stable in the dispersion as a sediment.

An additional factor to consider is the active content, that is, the amount of polymer dispersed in the polymer dispersion. High active content minimizes transport costs and gives easier handling in the final application. By using an efficient dispersant, dispersions with a high active content can be obtained at the same time that viscosity can be kept low. However, an increase in active content above a certain level cannot always improve improved retention and dehydration performance in a papermaking process.

During preparation of a polymer dispersion, polymer deposits form and stick to the reaction vessel and stirrer. This leads to time consuming procedures for cleaning reaction equipment.

It is an object of the present invention to provide a water soluble anionic polymer dispersion, preferably salt-free, having high stability and high active content. Polymer dispersion should also give good retention and dehydration results when using papermaking processes, acting as a good flocculant in other processes such as dump water treatment, acting as a good thickener in various applications such as cosmetic formulations, and also may be used in soil improvement processes. It is a further object of the present invention to provide a process for preparing a water-soluble, preferably salt-free, polymeric dispersion where the process viscosity is kept low and regulating the preparation without large viscosity peaks, and which gives no deposits. Finally, it is an object of the present invention to provide a papermaking process in which polymer dispersion is used.

The Invention

By "stabilizer" is significant herein a polymer function whose function is to maintain polymer dispersed particles / droplets in the dispersion.

By "co-stabilizer" herein is meant a polymer whose function is to produce a polymer formed from the polymerization of one or more monomers to precipitate from the solution into solid particles or liquid droplets.

According to the invention, it has been surprisingly found that a highly stable polymer dispersion having high active content of a dispersed polymer and low process viscosity can be achieved by a process for preparing a polymer dispersion comprising polymerizing one or more nonionic monomers (mi) and one or more nonionic vinyl monomers (1112) present in a reaction mixture further comprising a polymeric stabilizer (B) and a polymeric co-stabilizer (C).

The invention further comprises a polymer dispersion comprising a dispersed polymer (A) of one or more anionic monomers (mi) and one or more nonionic devinyl monomers (1112) / a polymeric stabilizer (B), and a polymeric co-stabilizer (C) .

The reaction medium is suitably an aqueous medium. Polymer dispersion is suitably an aqueous polymer dispersion. The polymer dispersion is suitably water soluble. The polymer particles / droplets have a particle size (thickness) of up to about 25 µm, also suitably from about 0.01 µm to about 25 µm, preferably about 0.05 µm to about 15 µm. om, more preferably from about 0.2 µm to about 10 µm.

Polymeric stabilizer (B) is suitably an organic polymer. Preferably, polymeric stabilizer (B) is a polymer of one or more monomers belonging to the group of acrylic acid, methacrylic acid, itaconic acid, 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), 2-acrylamido-2-methyl -1-Butane Sulfonic Acids (AMBS), Acryloxyethyl Sulfonic Acid, Methacryloxy Sulfonic Acid, Acryloxypropyl Sulfonic Acid, Methacryloxypropyl Sulfonic Acid, Vinyl Sulfonic Acid, Methyl Sulfonic Acid, Styrene Sulfonic Acid, Maleic Acid, Maleamidic Acid, and / or Vinyl Acid phosphonic. Other suitable polymeric stabilizers are copolymers of maleic acid or maleamidic acid, respectively, with styrene or vinyl ethers, or alpha-olefins which may contain additional comonomers. Preferably, polymeric stabilizer (B) is an acrylic or methacrylic acid copolymer with an additional of the listed monomers, preferably 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS).

The weight average molecular weight of polymeric stabilizer (B) is suitably from about 5,000 to about 5,000,000 g / mol, preferably from about 10,000 to about 1,000,000 g / mol, more preferably from about 20,000 to about 1,000. 000 g / mol, and more preferably from about 35,000 to about 500,000g / mol.

The polymer dispersion suitably comprises from about 0.2 to about 5 weight% polymer stabilizer (B) based on the total weight of the dispersion or reaction mixture, preferably from about 0.5 to about 3 weight%, more preferably about from 0.8 to about 1.5 weight%.

The polymeric co-stabilizer (C) is suitably an organic polymer. Preferably, the polymeric co-stabilizer (C) is a polymer of one or more monomers belonging to the group of acrylic acid, methacrylic acid, vinyl sulfonate, styrene sulfonic acid, itaconic acid, vinylphosphonic acid, 2-acrylamido-2-methyl-1-propane Sulfonic Acids (AMPS), 2-Acrylamido-2-methyl-1-butane Sulfonic Acids (AMBS), Acryloxyethyl Sulfonic Acid, Methacryloxyethyl Sulfonic Acid, Acryloxypropyl Sulfonic Acid, and Methacryloxypropyl Sulfonic Acid.

Preferably, two or more co-stabilizers (C) are present in the polymer reaction and dispersion mixture.

The weight average molecular weight of the polymeric co-stabilizer (C) is suitably from about 100 to about 50,000 g / mol, preferably from about 500 to about 30,000 g / mol, more preferably from about 1,000 about 20,000 g / mol, even more preferably from about 1,000 to about 15,000 g / mol, more preferably from about 1,000 to about 10,000 g / mol.

The polymer dispersion suitably comprises from about 2 to about 50 weight% of one or more polymeric co-stabilizers (C) based on the total weight of the dispersion or reaction mixture, preferably from about 3 to about 25 weight%, more preferably about 5a to about 15 weight%.

The polymeric stabilizer (B) and the polymeric co-stabilizer (C) in the polymer reaction or dispersion mixture are preferably composed of different monomers or, if they are composed of the same monomers, contain different monomer ratios.

Polymeric stabilizer (B) or polymeric co-stabilizer (C) is not suitably a dextrin or dextrin derivative. One or more anionic monomers (mi) belongs appropriately to the acrylic acid, methacrylic acid (sulfonic acid styrene), 2-acrylamido- 2-Methyl-1-propane sulfonic acid (AMPS), 2-Acrylamido-2-methyl-1-butane sulfonic acid (AMBS), Acryloxyethyl sulfonic acid, Methacryloxyethyl sulfonic acid, Acrylicoxypropyl sulfonic acid, Methacryloxypropyl sulfonic acid, Sulfonic vinyl acid, and their salts alkaline, alkaline earth or ammonium.

One or more nonionic monomers (1112) suitably belongs to the group of acrylamide, methacrylamide, N-methylacrylamide, N-methylacrylamide, N-ethylacrylamide, N-ethyl methacrylamide, N-isopropyl methacrylamide, N, N-dimethyl, N-dimethyl, butylacrylamide, Nt-butyl methacrylamide, N-hydroxyethylacrylamide, N- (tris- (hydroxymethyl) methyl) acrylamide, N-vinyl formamide, N-vinyl acetamide, hydroxyalkylacrylate or hydroxyalkyl methacrylate with C2 -C4 alkylalkyl or C1-6 alkylacrylate , benzylacrylate or benzyl methacrylate, dihydroxy (methoxyethylene oxide) acrylic or methacrylic acid esters having 1-20 ethylene oxide units, or commonomethoxyhydroxy- (polyethylene oxide) acrylic or methacrylic acid esters having 1-20 ethylene oxide units. Preferably, the one or more nonionic monomers (1112) belong to the deacrylamide group, or acrylate or methacrylate esters. The molar ratio between anionic monomer (mi) and nonionic omomer (ni2) is suitably about 1:99. about 25:75, preferably from about 3:97 to about 20:80, more preferably from about 5:95 to about 15:85.

The weight average molecular weight of the dispersed polymer (A) is suitably from about 1,000,000 to about 15,000,000 g / mol, preferably from about 1,500,000 to about 10,000,000 g / mol, more preferably about 2,000. .000 to about 8,000,000 g / moles.

Polymerization is suitably a free deradical polymerization. The initiator is suitably a deradical former, preferably a water soluble azo initiator, a water soluble peroxide, or a water soluble redox initiator. Preferred initiators include 2,2'-azobis- (amidinpropane) hydrochloride, 2,2'-azobis- (2-methyl-N- (2-hydroxyethyl) propionamide, 4,4'-azobis- (4-acidocyanovaleric), and their alkaline and ammonium salts, t-butylhydroperoxide, perhydrol, peroxydisulfate, or the aforementioned peroxides in combination with a reducing agent, such as sodium metabisulfite, or earth salts.

The polymer dispersion suitably comprises from about 5 to about 40 weight% of the dispersed polymer (A) based on the total weight of the dispersion, preferably from about 10 to about 30 weight%, more preferably from about 12 to about 25 weight. The amount of one or more inorganic salts in the polymer dispersion is suitably from 0 to about 1.9 weight% based on the total weight of the dispersion or mixture mixture, preferably from 0 to about 1 weight%, more preferably from 0 to about 0.5 wt%, more preferably from 0 to about 0.1 wt%, or substantially salt free.

By "inorganic salts" is suitably significant herein any inorganic salt, preferably salts belonging to the group of inorganic alkali metal, earth alkali metal, or ammonium halides, sulfates and phosphates.

The polymer dispersion may also comprise additional substances such as crosslinkers and branching agents.

The polymerization temperature may vary depending, for example, on which monomers and polymerization initiator are being used. Suitably, the polymerization temperature is from about 30 to about 90 ° C, preferably from about 35 to about 70 ° C. The process is suitably a semi-batch process, that is, monomers mi and ni2 are both present at the beginning of the polymerization process, and additionally added at a later stage, or in one or more portions, or continuously over a period of time during the reaction. The reaction mixture is adequately dried during the polymerization process at a suitable agitation rate for the process. Suitably, the agitation rate is from about 100 to about 1000 rpm.

The invention further comprises the use of a polymer dispersion as a retention and dehydration aid for papermaking, as a thickening agent, as a soil enhancing agent, and / or as an additive to increase the dry strength of the paper. More specifically, the invention can be used as a helper in various processes such as flocculants when it comes to dumping water, or aids in other solid-liquid separation processes in, for example, metal, ceramic, printing, biotechnology and pharmaceutical industries. . Polymer dispersion may also be used as a thickener in, for example, the chemical, biotechnology, pharmaceutical and cosmetic industries.

Finally, the present invention comprises a process for producing paper from an aqueous suspension containing cellulosic fibers, and optional fillers, which comprises adding to the suspension an aqueous polymer dispersion according to the invention, forming and draining the suspension onto a wire mesh.

When using the polymer dispersion according to the invention in papermaking processes, the dispersion is added to the cellulosic fiber suspension and optional fillers to be dehydrated in amounts that may vary within wide limits depending on, among others, type. and number of components, supply types, load content, load type, dead point, etc. The dispersed polymer is usually added in an amount of at least 0.001%, often at least 0.005% by weight, based on the dry substance in the stock to be dehydrated, and the upper limit is usually 3%, and suitably 1.5% by weight. The polymer dispersion according to the invention is suitably diluted prior to its addition to the cellulosic suspension. Additional additives which are conventional in papermaking can of course be used in combination with the polymer dispersion according to the invention, such as, for example, silica-based soles, dry strengths, wet strengths, wetting agents. whitening agents, dyes, sizing agents similar to rosin-based sizing agents, and reactive sizing agents of cellulose, for example alkyl and alkenyl ketene dimers, alkyl and alkenyl ketene multimers, and succinic anhydrides, etc. The cellulosic suspension or stock may also contain mineral fillers of conventional types such as, for example, kaolin, porcelain clay, titanium dioxide, gypsum, talc and natural and synthetic calcium carbonates such as chalk, ground marble and calcium carbonate. precipitate. The term "paper" as used herein includes not only paper and its production, but also other sheets containing fibracellulosic, or web-like products, such as, for example, board and cardboard, and the production thereof. The process may be used in the production of paper from different types of cellulose-containing fiber suspensions, and the suspensions shall suitably contain at least 25% by weight, and preferably at least 50% by weight of such fibers, based on the dry substance. The suspension may be based on chemical pulp fibers such as desulfate, sulfite and organosolv pulps, mechanical pulp, such as thermomechanical pulp, chemo-thermomechanical pulp, wood pulping and pulping, both softwood and hardwood, and may also be based on recycled fibers, optionally from unpainted pulps, such mixtures.

The invention will now be further described in conjunction with the following examples which, however, should not be construed as limiting the scope of the invention.

Examples

Example 1

A stabilizer produced from methacrylic acid (MAA) and 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), in an 80:20 molar ratio, was prepared: A mixture of 85g of ultra pure water, 8, 24 g of AMPS (solid), 16.62 g of MAA and 11.5 g of NaOH (50%) was adjusted to pH 7 by half NaOH (50%). 0.02 g EDTA (solid) was added to the mixture. Additional ultra-pure water was added to achieve a total mass of 127 g. This was filled in a 150 ml double wall glass reactor with anchor stirrer, nitrogen inlet, reflux condenser and bottom valve. The mixture was stirred at 150 ° C / minute and purged with nitrogen. The reactor contents were heated to 45 ° C. 0.05 g of V-50 (2,2'-Azobis- (2-amidinopropane) dihydrochloride) was added. After 60 minutes, the temperature was increased to 50 ° C. The mixture was polymerized and isolated by ultrafiltration and freeze-drying. The weight average molecular weight was about 15,000g / mol.

Examples 2-7:

A polymer dispersion was prepared by polymerization of a monomer mixture comprising acrylamide and acrylic acid in the presence of a polymeric stabilizer and a polymeric co-stabilizer.

A mixture of 30 g of water, 24.3 g of polyacrylic acid co-stabilizer (45%, Sigma-Aldrich, Mw1.200), 1.2 g of poly (MAA-co-AMPS) polymer stabilizer (80:20 ) (according to example 1, Mw 15,000), 28.1 g deacrylamide (50 wt%), 1.07 g acrylic acid, 0.04 g sodium deformate, 0.03 g EDTA, and 1, 17 g of NaOH (50 wt%) was stirred, and the pH was adjusted to 7. Water was added to 100 g, and for 8 hours azo-initiator VA-044 (2,2'-azobis- (N, N'- dimethylene isobutyramine) dihydrochloride, Wako) was added (0.5 g in steps). The temperature was kept at 35 ° C. After 16 hours, the stirring was stopped.

Five additional polymer dispersions were prepared using the same procedure as described above, but by changing the ratio of nonionic monomer to anionic monomer, using a second nonionic monomer in the dispersed polymer, and also using as a co-stabilizer. in some cases a combination of polyacrylic acid and polymethacrylic acid. As a stabilizer, 1.2 weight% poly (MMA-co-AMPS) in a 80: 20 molar ratio was used. The active contents (polymer content) in the stabilizer were around 15 weight%. 11% weight of co-stabilizer was used.

In Table 1, the following abbreviations are used:

AAm = acrylamide

AA = acrylic acid

MMA = methyl methacrylate

t-BuA = t-butyl acrylate

n-BuA = n-butyl acrylate

PAA = polyacrylic acid

PMAA = polymethacrylic acidTable 1:

<table> table see original document page 17 </column> </row> <table>

The process viscosity was low (less than 2000 mPas) for all dispersions.

Example 8

The polymer dispersions prepared in Examples 2-4 were tested for retention and dehydration performance in papermaking processes of an available Dynamic Drain Analyzer (DDA) from Akribi, Sweden. The supply used was based on 60 wt.% Targeted 80/20 birch pulp, and 40 wt.% Calcium carbonate. The stock volume was 800 ml, pulp concentration 5 g / l, and conductivity 1.5 mS / cm. The stock was agitated at a speed of 1500 rpm, while the following was added to the stock: a scrap refuse (0.5 kg / t), polymer dispersion (1.0 kg / t), and finally anionic inorganic particles ( 0.5 kg / t). The temperature was 22.5 ° C. A 0.35 bar vacuum was used for analysis. Retention time (sec) and turbidity (NTU) were measured.

Table 2: Polymer Dispersions and Application Tests

<table> table see original document page 18 </column> </row> <table>

It is concluded that the dispersions according to the invention work well in retention and dehydration aids.

Example 9

Shelf life, measured as settling stability, was tested for dispersions according to Examples 2-7. A sample of 10 g each dispersion was centrifuged for 30 minutes at 3000 rpm. The amount of polymer sediment was determined for each sample. None sampled any polymer sediment.

Thus, it is concluded that long useful polymer dispersions can be obtained by the present invention, also at high active contents.

Claims (20)

1. A process for the preparation of a water-soluble polymer dispersion, characterized in that it comprises the polymerization of one or more water-soluble monomers (mi) and one or more nonionic vinyl monomers (m2) present in a reaction mixture comprisingadditionally one. polymeric stabilizer (B) being a polymer of one or more monomers belonging to the group of acrylic acid, methacrylic acid, itaconic acid, 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), 2-acrylamido-2-methyl-1 -butane sulfonic acid (AMBS), acryloxyethyl sulfonic acids, methacryloxy sulfonic acid, sulfonic acryloxypropyl acid, methacryloxypropyl sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, methylene sulfonic acid, styrene sulfonic acid, maleic acid, malamidic acid, and / or a vinyl phosphonic acid maleic or maleamic acid copolymer, respectively, with l ethers or alpha olefins; and a polymeric (C) co-stabilizer being a polymer of one or more monomers belonging to the group of acrylic acid, methacrylic acid, vinyl sulfonate, styrene sulfonic acid, itaconic acid, vinylphosphonic acid, 2-acrylamido-2-methyl-1-propane acid sulfonic acid (AMPS), 2-acrylamido-2-methyl-1-butane sulfonic acid (AMBS), acryloxyethyl sulfonic acid, methacryloxyethyl sulfonic acid, acryloxypropyl sulfonic acid, emethacryloxypropyl sulfonic acid; the weight average molecular weight of polymeric stabilizer (B) is about 20,000 to about 1,000,000 g / mole, and the weight average molecular weight of the polymeric co-stabilizer (C) is from about 1,000 to about -15,000 g / mole. 2.- Water-soluble polymer dispersion, characterized in that it comprises a dispersed polymer (A) of one or more water-soluble monomers (mi) and one or more nonionic vinyl monomers (iri2), - a polymeric stabilizer (B) being a polymer of one or more monomers belonging to the group of acrylic acid, methacrylic acid, itaconic acid, 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), 2-acrylamido-2-methyl-1-methylamide. sulfonic acid butane (AMBS), acryloxyethyl sulfonic acid, methacryloxy sulfonic acid, sulfonic acrylpropyl acid, sulfonic methacryloxypropyl acid, sulfonic vinylacid, allyl sulfonic acid, sulfonic acid styrene, maleic acid, malamidic acid, and / or phosphonic acid vinyl, maleic or maleamidic acid, respectively, comestyrene, vinyl ethers or alpha-olefins; and a polymeric (C) co-stabilizer being a polymer of one or more monomers belonging to the group of acrylic acid, methacrylic acid, vinyl sulfonate, styrene sulfonic acid, itaconic acid, vinylphosphonic acid, 2-acrylamido-2-methyl-1-propane acid Sulfonic Acid (AMPS), 2-Acrylamido-2-Methyl-1-Butane Sulfonic Acid (AMBS), Acryloxyethyl Sulfonic Acid, Methacryloxyethyl Sulfonic Acid, Acryloxypropyl Sulfonic Acid, Emethacryloxypropyl Sulfonic Acid; The weight average molecular weight of the polymeric stabilizer (B) is about 20,000 to about 1,000,000g / mole, and the weight average molecular weight of the polymeric co-stabilizer (C) is about 1,000 to about -15,000g / mole. 3. A process according to claim 1 or a polymer dispersion according to claim 2 wherein the reaction mixture is an aqueous medium and the polymer dispersion is an aqueous polymer dispersion. 4. A process according to any one of claims 1 or 3 or polymer dispersion according to any one of claims 2-3, characterized in that the polymer particles / droplets have an average size of up to about 25 µm. A process according to any one of claims 1 or 3-4 or polymer dispersion according to any one of claims 2-4, characterized in that two or more co-stabilizers (C) are present in the mixture. reaction and polymer dispersion. A process according to any one of claims 1 or 3-5 or polymer dispersion according to any one of claims 2-5, characterized in that the polymeric stabilizer (B) and the polymeric co-stabilizer ( C) Different demonomers are produced. 7. A process according to any one of claims 1 or 3-6 or polymer dispersion according to any one of claims 2-6, wherein the anionic monomer (mi) suitably belongs to the acrylic acid group. , methoxyacrylic acid, (styrene sulfonic acid), 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), 2-acrylamido-2-methyl-1-butane sulfonic acid (AMBS), acryloxyethyl sulfonic acid, methacryloxyethyl sulfonic acid, sulfonic acryloxypropyl acid, methacryloxypropyl sulfonic acid, vinyl sulfonic acid, and their alkaline, alkaline earth or ammonium salts. A process according to any one of claims 1 or 3-7 or polymer dispersion according to any one of claims 2-7, characterized in that the one or more nonionic monomers (1112) belongs to the acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-ethylacrylamide, N-ethylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, N, N-dimethylacrylamide, Nt-butylacrylamide, Nitrile-methylamide (C 2-4 hydroxymethyl) methylacrylamide, N-vinyl formamide, N-vinyl acetamide, hydroxyalkylacrylate or hydroxyalkyl methacrylate with C1 -C4 alkyl, alkylacrylate or alkyl methacrylate with benzylmethacrylate acrylate or dihydroxyacrylate (polyethylene oxide) having 1-20 units of ethylene oxide, or acrylic or methacrylic acid esters commonmethoxyhydroxy- (polyethylene oxide) having 1-20 units of oxide ethylene. 9. A process according to any one of claims 1 or 3-8 or polymer dispersion according to any one of claims 2-8, characterized in that the one or more monomers (m2) belong to the acrylamide group. , or acrylate or methacrylate esters. A process according to any one of claims 1 or 3-9 or polymer dispersion according to any one of claims 2-9, characterized in that the amount of salinorganic is from 0 to about 1.9. weight% based on total weight of dispersion or reaction mixture. 11. A process according to any one of claims 1 or 3-10 or polymer dispersion according to any one of claims 2-10, characterized in that the amount of one or more inorganic salts is from 0 to about 10%. 0.5 weight% based on total amount of dispersion or reaction mixture. 12. A process according to any one of claims 1 or 3-11, characterized in that the reaction mixture comprises from about 3 to about 20 mol% of one or more water-soluble (mi) anionic monomers. 13. A process according to any one of claims 1 or 3-12, characterized in that the reaction mixture comprises from about 80 to about 97 mol% of one or more non-ionic vinyl monomers (m2). 14. A process according to any one of claims 1 or 3-13, characterized in that the reaction mixture comprises from about 0.5 to about 3% by weight of the polymeric stabilizer (B). 15. A process according to any one of claims 1 or 3-14, characterized in that the reaction mixture comprises from about 3 to about 25% by weight of the polymeric co-stabilizer (C). Polymer dispersion according to any one of claims 2-11, characterized in that it comprises from about 10 to about 30 weight% of the polymer dispersed (A). Polymer dispersion according to any one of claims 2-11 or 16, characterized in that it comprises from about 0.5 to about 3 weight% of the polymeric stabilizer (B). Polymer dispersion according to any one of claims 2-11 or 16-17, characterized in that it comprises from about 3 to about 25 weight% of the polymeric co-stabilizer (C). Use of a polymer dispersion according to any one of claims 2-11 or 16-18, characterized in that it is as a retention aid and dehydration aid for papermaking, as an additive to increase the dry strength of paper as a thickening agent. , and / or as a soil enhancing agent. 20. A process for producing paper from an aqueous suspension containing cellulosic fibers and optional fillers, comprising adding to the suspension a polymer dispersion according to any of claims 2-11 or 16-18, forming and draining the suspension into a web. wire