DE4436317C2 - Process for improving the retention of mineral fillers and cellulose fibers on a cellulose fiber sheet - Google Patents

Description

The invention relates to the technical field of papermaking, it relates in particular the technical field of wet-end additives (additives in the wet section) to the papermaking entry in the manufacture of paper. The invention specifically relates to a method for improving retention of mineral fillers and cellulose fibers on a cellulose fiber sheet, the steps of (a) preparing a cellulose pulp slurry, (b) Zu at least one water-soluble anionic polymer flocculant to the cellulose pulp slurry, (c) adding at least one water soluble cationic copolymer flocculant to the cellulose pulp Slurry and (d) forming a cellulose fiber sheet from the cellulo pulp slurry containing both the anionic polymer (s) Flocculant as well as the cationic copolymer flocculant (s) contains.  

In the production of paper, an aqueous cellulo sesuspension or slurry to a paper sheet (Paper sheet) shaped. The cellulose slurry is applied in general to a consistency of less than 1% (Dry weight percent solids in the slurry) diluted. Often a slurry with a consi less than 0.5% immediately before used to run the paper machine. The finished paper sheet However, (paper sheet) must have a water content of less than about 6% by weight. Therefore, the drainage is at paper making extremely important for efficiency and the cost of production.

The most cost effective dewatering process is the simple one draining (drainage). To more expensive Ver driving that are used include the vacuum hand treatment, pressing, felt dewatering and pressing and drying. In practice, a combination this method applied for drainage or the Sheet of paper is ge up to the desired water content dries. Since the drainage (draining) both the first used and the cheapest Ent watering method is represented by an Ver Improving the efficiency of the Siebentwässerung the What amount of water which must be removed by other means, reduced and thus the overall efficiency of the Drainage improves and the costs are ver Ringert.

Another aspect of papermaking, for us degree of efficiency and the cost of production are extremely important is, is the retention of the components of the substance input (the paper raw materials), on and within the fiber fleece, which is formed during papermaking. The Pa pier maker entry generally contains particles, their size ranges from 2 to 3 mm Cellulo fibers up to fillers of a size of some  few μm and up to colloids. Within this In the area there are cellulose fines, mineral Fillers (used to control the opacity, Whiteness and other paper properties) and other small particles, generally without adding egg or more retention aids to a signifi edge share the cavities (pores) between the cellulosic fibers in the paper-making process Fiber fleece would happen.

A method for improving the retention of Cellu loose fines, mineral fillers and other ones Support components on the nonwoven fabric is the use of egg A coagulant / flocculant system that is used is added to the headbox of the paper machine. In egg Such a system will first be a coagulant, For example, a synthetic cationic polymer with a low molecular weight or a cationic mo modified starch added to the substance entry, wherein the Coagulants generally on the particles in the entry, especially on the cellulose fines and the mineral fillers, existing negative top reduces surface charges and thereby agglomeration This particle causes, what the addition of a Floc connecting means. This flocculant is in the general an anionic, cationic or not ionic synthetic polymer with a high molecular weight Weight, the particles and / or agglomerates by Off formation of bridges between the surfaces with each other connects, which ent from the particles large agglomerates stand. The presence of these large agglomerates in the Entry when the fibrous web of the paper sheet shaped increases the retention of the particles in the nonwoven fabric. The agglomerates are filtered out of the water and deposited on the nonwoven web, of which the non-woven agglomerated particles to a large extent such Paper nonwoven web would happen.  

Although a flocculated agglomerate is generally the Screen drainage (dripping) of the nonwoven fabric to such a degree as it would occur if the entry would be pulpy or a lot of mushy ma contained, not affected when these flakes be filtered through the nonwoven web, whose pores up are reduced to a certain extent, thereby becomes the Efficiency of the Siebentwässerung (drainage) reduced. The retention is therefore increased, but at the same time the occurrence of an adverse effect on the seventh drainage.

Another system for achieving an improved combination of reins tion and drainage is known from US Pat. Nos. 4,753,710 and 4,913,775 known. In the process described therein, the aqueous cellulose Papermaking suspension first an organic cationic polymer added with a high molecular weight, followed by the addition of Bentonite as an anionic polymer flocculant after shearing closes. The shearing is done in one or more stages and This will cause the large flocs that come through the organic polymer high molecular weight, crushed into microflakes and By adding the bentonite particles, a further agglomeration will occur achieved. Both cationic and anionic polymer flocculation mediums are added at the same place. This also applies to the Finnish U.S. Patent Nos. 67,735 and 67,736, to which reference is made in U.S. Patent 4,753,710 and in which also the use of inorganic anio nischer polymer flocculant (polysilicic acid) is recommended in the Mixture with the organic cationic polymer flocculant at the be added to the same place.

From US Pat. No. 4,388,150 it is known to use a combination of ka cationic starch and colloidal silica, the amount of Web of retained material, d. H. the filler retention, increase. According to a variant of this method disclosed in US Pat. Nos. 4,643,801 and 4,750,974, in addition to a cationic starch  and to colloidal silica, a high anionic polymer Used molecular weight.

U.S. Patent 4,795,531 discloses the use of a retention and sieve bentwässerungs system, which consists of a cationic polymer Low molecular weight flocculant, colloidal silica di oxide sol and an anionic or cationically charged polymer Flocculant with a high molecular weight.

Other systems for improving drainage and retention are in South African Patent 2 389/90, in which a single cationic High molecular weight polymer is used, as well as in the US Pat. No. 5,098,520, which discloses a cellulose papermaking Slurry containing a mineral filler with a cationic (Meth) acrylamide polymer with a high molecular weight is treated, followed by the performance of a shear stage and the addition of an anioni low molecular weight polymer.

According to DE-A-29 34 007 is to improve the Füllstoff-Rückhaltevermö gens in papermaking a cationic polymer flocculant with a molecular weight of the order of 5 million and an anionic beautiful polymer flocculant with a molecular weight of the order of magnitude 15 million in the same place, with white in front of everyone addition a reaction time of 1 to 2 min is to be observed.

From US Patent 5,185,062 it is also known in the manufacture of Paper with improved drainage and retention properties Cellulose pulp slurry first a cationic polymer flocculation high molecular weight (greater than 5 million) and then an anioni beautiful polymer flocculant with an average molecular weight (30,000 to 5 000 000), in which case both flocculants on the same place and between both polymer flocculants. Additives the pulp is subjected to a shear treatment. After the Anga ben in this document are the best results in terms of the Filler Retention achieved by using anionic organi shear polymer flocculant having a molecular weight in the range from 200,000 to 750,000.  

Drainage in general and especially the Seventh drainage (draining by draining, drainage) is believed to improve when the pores of the Paper web are less clogged, and it is on assumed that the retention by adsorption in comparison For retention by filtration, this pore clogging ver decreases.

Better retention of fines and fillers allows for a given paper quality the reduction the cellulose fiber content of this paper. Since pulp with a lower quality used to the paper Reduce manufacturing costs is the retention aspect in papermaking all the more important because of the content on ultrafine parts of these lower quality pulps is generally higher than that of the pulps with a higher quality.

Through a better retention of the finest parts, fillers and other slurry components becomes the amount These substances, which are connected to the white water (also called white water) lost, degraded and thus be the amount of material waste, the cost of the Waste treatment and waste disposal and the resulting resulting adverse effects on the environment siege.

Another important characteristic of a given Pa The production process of the pier is the formation of the structure paper sheet. The formation is determined by the Cloudiness (change of light transmission) of a paper bow and a strong cloudiness is an indication of a bad formation. When the retention goes up to a high value, for example a retention value of 80 or 90%, the formation parameters go in general my abrupt return from a good formation to one  bad formation. At least in theory is assumed men, that if the retention mechanisms of a gege papermaking process is different from a Filtra tion to adsorption, the adverse Ef Effect on the formation when achieving high retention values Becomes, decreases and a good combination of high Reten tion and good formation is disclosed in US Pat. No. 4,913,775 attributed to the use of bentonite.

In general, it is desirable to reduce the amount of material in a papermaking process for a given The purpose is to reduce, without the ange ange aspired to deteriorate earnings. Such addie Reductions can be both material cost savings as well as benefits to the handha handling and processing.

It is also desirable to use additives corresponding to the Pa machine can be fed without excessive Problems occur. Additives that are easy in water dissolve or disperse, minimize the cost and the Energy required to make it the paper machine and provide a more reliable unit the feed as additives that are not easy be dissolved or dispersed.

The object of the invention is therefore to pursue a papermaking process ben, in which the filler retention is improved without the formation deteriorates and has no detrimental effect on drainage Properties.

This object is achieved in that the Cellulosepul pen slurry at least one water-soluble anionic polymer Flocculants with a molecular weight of 5 million to 25 million and at least one cationic copolymer flocculant in each case specific amount at a distance of 10 to 80 cm, preferably 30 to 50 cm, added between the addition points of the two flocculants  wherein the order of addition of the above-mentioned two poly mer flocculant is arbitrary.

According to a first embodiment, the invention relates to a method for improving the retention of mineral fillers and cellulose fibers on a cellulose fiber sheet comprising the steps of:

• a) Preparation of a Cellulose Pulp Slurry
• b) adding at least one water-soluble anionic polymer Flocculant to the cellulose pulp slurry,
• c) adding at least one water-soluble cationic copolymer Flocculant to the cellulose pulp slurry and
• d) forming a cellulose fiber sheet from the cellulose pulp slurry containing both the anionic polymer flocculant and the cationic copolymer flocculating agent (s),
  characterized in that is
• e) b ₁ ) in step (b) a water-soluble anionic polymer flocculant having a molecular weight of 5,000,000 to 25,000,000 in an amount of 0.001 to 0.5 wt .-%, based on the total solids content of the cellulose pulps Slurry, is used;
• f) c ₁ ) in step (c) a water-soluble cationic copolymer flocculant having a molecular weight of 5,000,000 to 15,000,000 in an amount of 0.001 to 0.5 wt .-%, based on the total solids content of the cellulose pulps Slurry, is used and
• g) c ₂ ) the cationic copolymer flocculant is added at a point 10 to 80 cm from the point of addition of the anionic polymer flocculant.

According to a second embodiment, the invention relates to a method for improving the retention of mineral fillers and cellulose fibers on a cellulose fiber sheet comprising the steps of:

• a) Preparation of a Cellulose Pulp Slurry  
• b) adding at least one water-soluble cationic copolymer Flocculant to the cellulose pulp slurry,
• c) adding at least one water-soluble anionic polymer Flocculant to the cellulose pulp slurry and
• d) forming a cellulosic fiber sheet from the cellulose pulp slurry containing both the cationic copolymer flocculant and the anionic polymer flocculant (s),
  characterized in that is
• e) b ₁ ) in step (b) a water-soluble cationic copolymer flocculant having a molecular weight of 5,000,000 to 15,000,000 in an amount of 0.001 to 0.5 wt .-%, based on the total solids content of the cellulose pulps Slurry, is used;
• f) c ₁ ) in step (c) a water-soluble anionic polymer flocculant having a molecular weight of 5,000,000 to 25,000,000 in an amount of 0.001 to 0.5 wt .-%, based on the total solids content of the cellulose pulps Slurry, is used and
• g) c ₂ ) the anionic polymer flocculant is added at a point 10 to 80 cm from the point of addition of the cationic copolymer flocculant.

In both embodiments, the cellulose pulp slurry is added between preferably exposed to the steps (b) and (c) a shearing force.

By the method according to the invention, it is possible in the papermaking To improve the filler retention considerably, without increasing the formation deteriorate and without affecting the drainage properties In this case, filler retention values of ≧ 40% are achieved, the far upper half of the usually achievable values of 26 to 30%.

When carrying out the process according to the invention, the addition takes place cationic (or anionic) water-soluble polymer flocculent with the high molecular weight mentioned above to the cellulose pulp Slurry within the aforementioned short distance of 10 to 80  cm, preferably 30 to 50 cm, to the addition point of the anionic (or ka tionischen) water-soluble polymer flocculant with the aforementioned high molecular weight immediately before the formation of a nonwoven fabric.

As the anionic polymer flocculant is preferably a wasserlösli used a vinyl polymer or copolymer containing at least 5 mol% Units with an anionic charge, preferably 5 to 95 mol% anionic Mer unit, in particular from 20 to 80 mol% of anionic mer units, contains.

The anionic polymer flocculant used in the invention has preferably a degree of substitution of at least 0.01, in particular of at least 0.05, and more preferably from at least 0.10 to 0.50.

Particularly suitable as anionic polymer flocculant is a polymer or copolymer of acrylic acid or methacrylic acid or their water-soluble alkali metal salts, hydrolyzed polyacrylamide, hydrolyzed poly methacrylamide or a copolymer of a non-ionic monomer the group acrylamide, methacrylamide, methyl or ethyl acrylate, methyl or Ethyl methacrylate, N-methylacrylamide and N-methylmethacrylamide, and a anionically charged monomer from the group propanesulfonic acid, vinyl sulfonate and sulfonate or phosphonate substituted monomer.

Particularly preferred is the use of a homo- or copolymer with a reduced specific viscosity (also referred to as intrinsic viscosity net) from 20 to 55 as an anionic polymer flocculant.

The anionic polymer flocculant is preferably in an amount from 0.005 to 0.25% by weight, especially from 0.005 to 0.1% by weight, especially from 0.005 to 0.075 weight percent, based on the total solids content of the Cel cellulose pulp slurry.

Particularly preferred is the use of an anionic polymer Flocculant selected from the group of acrylic acid polymer,  Methacrylic acid polymer, hydrolyzed polyacrylamide, hydrolyzed poly methacrylamide, the (meth) acrylamide / (meth) acrylic acid copolymers, the Me ethyl or ethyl (meth) acrylate / (meth) acrylic acid copolymers and N-methyl (meth) acrylamide / propanesulfonic acid or vinyl sulfonate copolymers.

As the cationic copolymer flocculant is preferably a copolymer from an uncharged monomer from the group acrylamide, methacrylamide, Methyl or ethyl acrylate and methyl or ethyl methacrylate, and a katio nisch charged monomer from the group dimethylaminoethyl, Dime thylaminoethyl methacrylate, dimethylaminoethyl (meth) acrylate-butyl chloride quat., Dimethylaminoethyl (meth) acrylate-benzoyl chloride quat., [3- (meth) acrylo ylaminopropyl] trimethyl ammonium chloride, N- [3- (dimethylamino) pro pyl] (meth) acrylamide and diallyldimethylammonium chloride.

As the cationic copolymer flocculant is preferably a copolymer used, the 2.5 to 60, especially 20 to 55, especially 30 to 50, all most preferably 40 to 50 mol%, of cationic mer units.

Particularly preferred is the use of a cationic copolymer Flocculant with a reduced specific viscosity of 3 to 30, preferably from 4 to 22, especially from 4 to 9, especially from about 5.

The cationic copolymer flocculant is preferably in an amount from 0.005 to 0.25 wt .-%, in particular from 0.005 to 0.1 wt .-%, be more preferably from 0.005 to 0.075 wt .-%, based on the total solids content of the pulp slurry.

In the cationic copolymer flocculation used in the invention is preferably a copolymer from the group of (Meth) acrylamide / dimethylaminoethyl (meth) acrylate, dimethyl amino (meth) acrylate-methyl chloride quat., dimethylaminoethyl (meth) acrylate benzyl chloride quat., [3- (meth) acryloylaminopropyl] trimethylammonium chloride,  N- [3- (dimethylamino) propyl] (meth) acrylamide and diallyldimethylam monium chloride copolymers is used.

As the cationic copolymer flocculant, particularly preferred is Acrylamide / diallyldimethylammonium chloride copolymer containing 20 to 60 mol% Contains diallyldimethylammonium chloride-mer units and a reduced specific viscosity of 4 to 30.

The implementation of the method according to the invention in its two off variant versions is explained in more detail below.  

A method for improving the retention of mineral Fillers and cellulose fibers on a cellulose fiber Arch includes several steps. A stage is used the production of a cellulose pulp (pulp) on slurry. To the pulp slurry is then a effective amount of a copolymer flocculant added. The copolymer flocculant is preferably a cation niche acrylamide / diallyldimethylammonium chloride copolymer high molecular weight. The copolymer flocculant preferably contains 20 to 60 mol% Diallyl dimethyl ammonium chloride mer units. The copoly in particular contains 30 to 40 mol% Diallyl dimethyl ammonium chloride mer units.

After optionally shearing the cationic copolymer flocculation medium containing cellulose pulp slurry the cellulose pulp slurry contains an effective amount of egg a water-soluble anionic flocculant with a high molecular weight added. The anionic Flocculant is preferably within a distance from 10 to 80 cm, preferably from 30 to 50 cm, from the addition point of the cationic high Mo copolymer molecular weight added. Then, from the cellulose Pul pen slurry formed a cellulose fiber sheet which contains both the cationic copolymer flocculant and the anionic flocculant.

In another embodiment of the invention, the Order of the respective addition of cationic and anionic flocculant be reversed, the Add first of anionic flocculant and afterwards of cationic flocculant is particularly preferred.  

The use of polymers of various types for Purposes of improving the Siebentwässerungs- and Reten tion behavior in papermaking processes is general my known. Such polymers are in the range of "natural polymers" such as starches up to synthetic Polyelectrolytes of various kinds. For examples such polyelectrolytes include anionic polymers, cationic polymers and amphoteric polymers. For examples such polymers also include nonionic polymers, z. As the non-ionic, but polar polyacrylamides. These polymers are at the concentrations used usually water-soluble.

In a conventional retention aid system known as "dual polymer system" is called a cationic beautiful low molecular weight polymer coagulant weight, followed by the addition of an anionic High molecular weight polymer flocculant closes.

The functional expressions "coagulants" and Naturally, "flocculants" are based on the effect that has a polymer on the cellulose slurry particles. A "coagulant" generally neutralizes one Surface charge on a particle, wherein a kationi beautiful coagulant a negative surface charge neutralized on a particle. A flocculant Detects itself in places on a variety of such particles while creating a bridging effect. What the Structural properties that are a polymer coagulati differ from a polymer flocculant, so that a coagulant is a polymer with a low molecular weight is while a floc kungsmittel a polymer with a high molecular weight is. A coagulant must also be cationic, to recreate the negative surface charges of the particles  neutralize. A flocculant is generally, ever but not necessarily, anionic.

Cationic polymer flocculants with a high mole kulargewicht were already used by the papermaker as substitutes for the anionic floc high molecular weight polymer of the dual polymer Retention and Drainage Remedy System used. These cationic flocculants have been so far however, polymers with a relatively low Charge density, the mole percentages of cationic mer- Units of about 10% and charge densities in the Order of magnitude of 1.0 or 1.2 equivalents of cationic Nitrogen per kg of dry polymer or less exhibited. Unlike the cationic coagulation They have been hitherto low molecular weight agents used together with those that are usually high in La have densities, z. B. Charge densities of 4 to 8 equivalents of cationic nitrogen per kg of troc kenem polymer.

The cationic polymer flocculants with a (relatively) high charge density and a high Molekularge according to the invention as a component of the Component Retention and Drainage Aids Systems used usually contain 2.5 to 60 mole% or less cationic mer units. virtue They contain 20 to 60 mol% of cationic mer-one units. Most preferably, the invention contains high molecular weight cationic polymer 30 to 50 Mole%, especially 40 to 50 mole%, of cationic mer units.

The cationic flocculants used in the present invention Teles usually have charge densities of 2 to 4 equivalents of cationic nitrogen per kg dry Polymer and preferably they have a charge density from 2.5 to 3.4 equivalents of cationic stick  substance per kg of dry polymer. An inventive ver Reversible particularly preferred polymer has a La density of about 2.8 equivalents of cationic stick substance per kg of dry polymer. This charge density is much lower than that of the cationic koagu prior art agents that replace them, however, it is generally higher than the charge densities the cationic flocculant, already known as floc in two-component coagulation with tel / flocculant systems are used.

The cationic polymer Floc used according to the invention The cationic agents differ from the cationic koagu laterial materials which they replace, in that they have much higher molecular weights. While that Molecular weight of a typical cationic coagulati in the range of several thousand to 200,000 can lie, the molecular weight of erfindungsge Usable cationic polymers in the range of 5,000,000 to 15,000,000 the molecular weight of the poly used in the invention do not mers for the cationic polymer flocculants can be specified exactly, have the invention usable polymers reduced specific viscosities (also as Intrinsic viscosities) in the range of 4 to 22 or higher compared to cationic coagulants, the generally reduced specific viscosities have less than 1.

In the cationic copoly used in the invention Mer flocculant is preferably a copolymer an uncharged monomer selected from the group Acrylamide, methacrylamide, the vinyl ester, such as methyl or ethyl acrylate or methyl or ethyl methacrylate, and a cationically charged monomer selected from Group dimethylaminoethyl acrylate, dimethylaminoethylme thacrylate, dimethylaminoethyl (meth) acrylate-butyl chloride  quat., dimethylaminoethyl (meth) acrylate benzoyl chloride quat., [3- (meth) acryloylaminopropyl] trimethylammonium chloride, N- [3- (dimethylamino) propyl] (meth) acrylamide and Diallyl dimethyl ammonium chloride. Preferably, as cationic copolymer flocculant a copo lymer from the group of (meth) acrylamide / dimethylamino ethyl (meth) acrylate, dimethylamino (meth) acrylate-methylchloro chloride, dimethylaminoethyl (meth) acrylate benzyl chloride quat., [3- (meth) acryloylaminopropyl] trimethylammonium chloride, N- [3- (dimethylamino) propyl] (meth) acrylamide or Diallyl dimethyl ammonium chloride copolymers used.

The inventively usable, particularly preferred cationic polymer flocculants are acrylamide / di allyldimethylammonium chloride (DADMAC) copolymers. He used according to the invention preferred cationic poly Mer flocculants contain, as indicated above, from 2.5 to 60 mole% diallyldimethylammonium chloride, and preferably 20 to 55 mol% diallyldimethylammonium chloride. Most The present invention preferably contains cationic polymer flocculant 40 to 50 mol% Diallyl dimethyl ammonium chloride. Although acrylamide is a be preferred comonomer in the preparation of these polymers is because it is commercially available and because of its non-ionic character, also other non-ioni used as long as the resulting monomers Polymer remains water soluble and no noticeable anioni contains a load. Examples of other non-ioni cal monomers, which together with diallyl dimethylammonium chloride can be polymerized, gehö ren methacrylamide and vinyl esters, z. For example, methyl methacrylate.

Under the term "(meth) acrylic ..." or "... (meth) acrylic ..." are both the corresponding acrylic acid compounds as well as the corresponding methacrylic to understand acid compounds.  

The molecular weight of the invention used cationic flocculants materials can vary greatly ming. The cationic floc usable according to the invention Kungsmittel materials have molecular weights of Minde at least 5,000,000. Although the molecular weights are only diminished can be estimated, have preferred polymers redu graced specific viscosities from 3 to 9, preferably from 4 to 7. A particularly be preferred acrylamide / diallyldimethylammonium chloride copoly mer has a reduced specific viscosity from about 5.

The synthesis of these types of polymers is well known such as in U.S. Patent 4,077,930 or in U.S. Patent 3,624,019 to which reference is expressly made becomes. The copolymer flocculation used according to the invention medium, in particular the diallyldimethylammonium chloride Copolymer flocculants may also be in the form of a ver thin aqueous solution, although these Methods are not preferred.

The water-soluble anionic flocculant component high molecular weight of the invention used Retention and drainage aids is general my known. The usable anionic polymer High molecular weight flocculants water-soluble polymers with a high Molekularge weight, which is a molecular weight in the Be rich between 5,000,000 and 25,000,000. Molecular weights in this range correspond in the Re gel of a reduced specific viscosity from 20 to 55.  

An anionic polymer flocculant is erfindungsge preferably a polymer or copolymer of acrylic acid or methacrylic acid or its water-soluble alka limestone salts, hydrolyzed polyacrylamide, hydrolyzed polymethacrylamide or a copolymer of a non ionic monomer, such as acrylamide, methacrylamide, methyl or ethyl acrylate, methyl or ethyl methacrylate, N-methyl acrylamide or N-methyl-methacrylamide, and a anionically charged monomer such as propanesulfonic acid, vinyl sulfonate or a by sulfonate or phosphonate substitu Used monomer. Particularly preferred is the use of egg anionic polymer flocculant selected is from the group acrylic acid polymer, methacrylic acid-Po lymer, hydrolyzed polyacrylamide, hydrolyzed poly methacrylamide, the (meth) acrylamide / (meth) acrylic acid copo lymeren, the methyl or ethyl (meth) acrylate / (meth) acrylic acid copolymers and the N-methyl (meth) acrylamide / propane sulfonic acid or vinyl sulfonate copolymers.

The anionic polymer flocculants are water soluble Vinyl polymers containing at least 5 mol% mer units with an anionic charge, preferably 5 to 95 mol% anionic mer units, and most preferably 20 to 80 mole% anionic mer units. Usually these polymers are polymers or copolymers of acrylic acid or methacrylic acid or its water-soluble alka limetal salts, hydrolyzed polyacrylamide, copolymers of acrylamidomethyl / propanesulfonic acid, vinylsulfonate or other sulfonate-containing monomers. In general becomes the anionic charged monomer with a non-ioni monomer, such as acrylamide, methacrylamide, methyl or Ethyl acrylate copolymerized. The anionic Polymers can also contain sulfonate or phosphonate Be polymers that have been synthesized by Modifi of acrylamide polymers in such a way that they have a Contain sulfonate or phosphonate substitution, or Mi of it. The anionic polymers can be in the form  of a solid, in powder form, after dissolving in Water or in the form of water-in-oil emulsions wherein the polymer is in the dispersed water phase of these emulsions is solved.

The anionic polymers have a degree of substitution of at least 0.01, preferably a degree of substitution of at least 0.05, and most preferably a substituent degree of at least 0.10 to 0.50. Under the Substitution degree is to be understood here that the polymers arbitrarily distributed repeating monomer units contain chemical functionalities that, when dissolved in water, are charged anionically, z. As carboxylate groups, sulfonate groups, phosphonate Groups. For example, one has Acrylamide / acrylic acid copolymer wherein the monomer mole ratio of acrylamide to acrylic acid is 90:10, a degree of substitution of 0.10. In a similar way have acrylamide / acrylic acid copolymers with monomer Molver ratios of 50:50 have an anionic degree of substitution from 0.5.

In the practice of the invention will cationic water-soluble flocculants with high moles kulargewicht preferably the pulp (pulp) slurry at a certain point according to the machine material bütte and before shearing in the mixing pump added, so that the cationic flocculant in the pulp Sludging is present when, as in a typical Papermaking process, the white water is added to the system. The anionic flocculant is preferably added to the pulp (pulp) slurry set immediately before performing a shear stage and / or after the printing screen, the headbox for Paper machine precedes. It is essential that the distance between the addition points of cationic and anionic flocculant to the pulp sludge 10 to 80 cm, preferably 30 to 50 cm.  

The cationic flocculant is generally in egg ner amount of 0.001 to 0.5 wt .-%, in particular 0.005 to 0.250 wt .-%, Based on the Total solids content of the pulps Slurry, added. Preferably, the cationic Flocculants in an amount of 0.005 to 0.1% by weight, most be Preferably in an amount of 0.005 to 0.075 wt .-%, based on the Total solids content the pulp slurry, added. This amount ent speaks a typical addition of 0.01 to 0.5 wt .-% Polymer solids, based on the total solids content, when cationic coagulants such as ethylene dichloride Ammonia or epichlorohydrin-dimethylamine condensation polymers in conventional "dual polymer" retention and Severe drainage programs are used.

The anionic flocculant is generally in ei ner amount of 0.001 to 0.5 wt .-%, especially from 0.005 to 0.25 wt .-%, based on the Total solids content of Pul pen slurry, added. Preferably, the anioni flocculants in an amount of 0.005 to 0.1% by weight, and most of all preferably in an amount of 0.005 to 0.075 wt .-%, based on the Total solids content the pulp slurry, added.

The following examples show the invention achieved advantages. All percentages contained therein refer to Unless otherwise indicated, by weight.

Standard test method for determination of retention

The test procedure described below is a laboratory Method simulating a paper machine and data be plus the retention, drainage and drainage provides other action parameters. The ones with these Test data obtained are comparable to the those involved in a commercial papermaking procedure that is simulated can be obtained.

It becomes a 500 ml sample of a standard pulp (Cellulose slurry) used. Any settings lungs, which are required in terms of consistency of the substance and the pH are carried out before management of a treatment and / or before the start of mixing. A Britt test device, as z. From PRM Incorporated, Syracuse, New York, is available as a mixing container used to achieve a standard degree of shear. These Device consists of a chamber with a capacity of about 1 liter and is equipped with a variable Ge engine equipped with a speed of 5.1 cm Three-blade propeller drives. The standard substance sample is first placed in the Britt tank and then becomes added the treatment agent. The substance / treatment medium combination is then combined with the desired Ge speed and for the desired period of time, then the filtrate is collected for 10 seconds.

Then the transmission (or turbidity) of the filtrate in Comparison to a blank. The increase in Transmission (decrease of turbidity) gives an increase of Retention of fines, mineral fillers and fibers on the fleece again. The sieve residue is removed from the Britt container and placed in a drainage system Test device introduced, which consists of a Büchner Funnel mounted on a graduated 250 ml cylinder is set. A coarse filter paper is placed on the Büchner Funnel placed and it is a vacuum of 0.1 MPa  created. 250 ml Siebrückstand be on the Poured filter paper and the time to 200 ml of water ent are removed as drainage time records. The resulting shaped web is combined with the coarse filter is removed and weighed to the Determine consistency in percent. The consistency in Pro cent is an indication of the solids content in percent The formed fleece and it is based on the weight of the formed web plus the filter paper minus the weight of known pulps and solids Filter paper. This result provides the weight of the Water in the formed fleece, from which easily the consi percent in percent (or percent solids) can be expected. The in all cases for this Standard variables used in the Table I below.

Britt tank test conditions for the polymeric floc kung medium test Pulp: typical paper mill fabric, 35% BHWK ¹ - 35% BSWK ² , 30% rejects, 20% by weight commercial precipitated calcium carbonate Britt tester: Commercially available standard container with three-blade stirrer Scree: 100R (100 mesh according to ASTM)

¹

bleached long fiber sulphate pulp
²

bleached short-fiber sulphate cellulose

Drainage (drainage): 5 ml disposable pipette, 80-90 ml / 30 s tip rpm: 1000 AL = L <timing: (Time sequence) t = 0 s; Start of mixing and adding the substance t = 10 s; Addition of commercial cationic starch @ t = 40 s; Addition of alum (if any) @ t = 45 s; Addition of coagulant or cationic flocculant according to the invention t = 55 s; Addition of anionic flocculant @ t = 65 s; Beginning of collecting the filtrate @ t = 95 s; Stop collecting the filtrate and end the experiment

example 1

This example describes a laboratory retention test. Of the Test was done with the following samples and below carried out under the conditions:

1) Paper machine fabric, typical for a 80 g / m ² -Ko paper

20% long fiber pine sulphate pulp
80% short fiber birch sulphate pulp
15% coated waste paper treated with 2.5-3.0 kg / t commercial epichlorohydrin / dimethylamine copolymer
26% filler CaCO ₃

of marble type, cationic di dispersed, charge +0,5 megv.
pH 7.2
without starch
optical brightener
Gluing: with 1.2% ketene dimer (AKD) starch, based on solid

2) Laboratory evaluation

Laboratory evaluation was carried out in comparison between the efficiency of a non-dispersed filler of chalk CaCO ₃ type having a whiter dispersed cationic type filler CaCO ₃ -Marmor type in the production of high-quality filled Ko pierpapieren (with a filler content of 27% CaCO ₃ ) under neutral papermaking conditions.

The laboratory retention ratings were compared with commercially available Alchem and Britt container testing devices.

The laboratory tests showed that the already existing retention systems, such as high molecular weight anionic polyacrylic acid, only high molecular weight cationic polyacrylic acid and combinations of a (low molecular weight) coagulant and one or both of the above systems together with the cationic dispersed CaCO ₃ did not work well.

A good performance was achieved with a Combination of 400 g per tonne (g / t) of a Acrylamide / sodium acrylate (70/30) copolymer and a Dosage of 200 g / t of a water-in-oil emulsion egg acrylamide / dimethylaminoethyl methacrylate Methyl chloride quaternary (DMAEM-McQ) (90/10) copoly mers with 36% polymer active ingredients (commercial product Nalco 46-19)  after the addition of the acrylic amide / sodium acrylate copolymer. Another re tentionsverbesserung was possible by a Vorbe treatment with 0.5 kg / t epichlorohydrin-dimethylamine (Epi-DMA) copolymer.

Example 2

In this example, a new cationic dispersed CaCO ₃ filler of the marble type and a combination of an acrylamide / sodium acrylate (70/30) copolymer and a water-in-oil emulsion of an acrylamide / dimethylaminoethyl methacrylate methyl chloride quat. (DMAEM-McQ) (90/10) copolymer.

The water-in-oil emulsion of an acrylamide / dimethylamino ethyl methacrylate methyl chloride quat. (DMAEM-McQ) (90/10) - Copolymer was filled in with 2.5% commercial activator (a biocide wetting agent mixture) in egg concentration of 1.5%. It was fresh water of Pa pier factory used. The inversion system used was the Commercial product NALMAT® B, a device for converting a W-O emulsion into an O-W emulsion.

The acrylamide / sodium acrylate (70/30) copolymer was washed with 2.5% activator in a concentration of 0.8% filled. Fresh water was used by the paper mill. The inversion system used was the o. G. Commercial product NALMAT® B.

In both examples, the two polymers were added in diluted form with warm fresh water together with perforated pipe lances in the pipe between the vertical seal and the headbox of the Papermaking process.

The acrylamide / sodium acrylate (70/30) copolymer became first added in the flow direction, followed by the addition of the Water-in-oil emulsion of the DMAEM-McQ copolymer in one  Distance of about 40 cm from the addition of the first polymer and connected in the flow direction.

Results

As a significant result, it was found that the first Addition of 300 g / t of acrylamide / sodium acrylate (70/30) - Copolymer and a second addition of 300 g / t of Acrylamide / DMAEM-McQ copolymer at a distance of about 40 cm gave the best results. There were filling fabric retention values of about <40% achieved. The Be bill is based on the filler in the headbox and the filler in the paper. The nominal amount of filler in the paper was 26%.

Claims (17)

A process for improving the retention of mineral fillers and cellulosic fibers on a cellulose fiber sheet comprising the steps of:

• a) Preparation of a Cellulose Pulp Slurry
• b) adding at least one water-soluble anionic polymer flocculant to the cellulose pulp slurry;
• c) adding at least one water-soluble cationic copolymer flocculant to the cellulose pulp slurry and
• d) forming a cellulose fiber sheet from the cellulose pulp slurry containing both the anionic polymer flocculant and the cationic copolymer flocculating agent (s),

characterized in that

• 1. b ₁ ) in step (b) a water-soluble anionic polymer flocculant having a molecular weight of 5,000,000 to 25,000,000 in an amount of 0.001 to 0.5 wt .-%, based on the total solids content of the cellulose pulps Slurry, is used;
• 2. c ₁ ) in step (c) a water-soluble cationic copolymer flocculant having a molecular weight of 5,000,000 to 15,000,000 in an amount of 0.001 to 0.5 wt .-%, based on the total solids content of the cellulose pulps Slurry, is used and
• 3. c ₂ ) the cationic copolymer flocculant is added at a point 10 to 80 cm from the point of addition of the anionic polymer flocculant.

2. The method according to claim 1, characterized in that as anioni beautiful polymer flocculant a water-soluble vinyl polymer or Copolymer containing at least 5 mol% Mer units with a anionic charge, preferably 5 to 95 mol% of anionic mer units, in particular from 20 to 80 mol% of anionic mer units. 3. The method according to claim 1 or 2, characterized in that a anionic polymer flocculant is used which has a substitution degree of at least 0.01, preferably of at least 0.05 and especially preferably of at least 0.10 to 0.50. 4. The method according to at least one of claims 1 to 3, characterized ge indicates that the anionic polymer flocculant is a polymer or Copolymer of acrylic acid or methacrylic acid or its water-soluble Alkali metal salts, hydrolyzed polyacrylamide, hydrolyzed polymethacry lamid or a copolymer of a nonionic monomer from the group Acrylamide, methacrylamide, methyl or ethyl acrylate, methyl or ethyl methacrylate, N-methylacrylamide and N-methylmethacrylamide, and an anio nisch-charged monomer from the group propanesulfonic acid, vinyl sulfonate and sulfonate or phosphonate substituted monomer is used. 5. The method according to at least one of claims 1 to 4, characterized ge indicates that as anionic polymer flocculant a homo- or  Copolymer with a reduced specific viscosity of 20 to 55 verwen it becomes. 6. The method according to at least one of claims 1 to 5, characterized ge indicates that the anionic polymer flocculant in an amount from 0.005 to 0.25% by weight, especially from 0.005 to 0.1% by weight, especially from 0.005 to 0.075 wt .-%, based on the total solids content of the Pul Pen slurry is used. 7. The method according to at least one of claims 1 to 6, characterized ge indicates that the anionic polymer flocculant is selected from the group acrylic acid polymer, methacrylic acid polymer, hydrolyzed Polyacrylamide, hydrolyzed polymethacrylamide, of (meth) acrylamide / (Meth) acrylic acid copolymers containing methyl or ethyl (meth) acrylate / (meth) Acrylic acid copolymers and the N-methyl- (meth) acrylamide / propanesulfonic acid or vinyl sulfonate copolymers. 8. The method according to at least one of claims 1 to 7, characterized ge indicates the distance between polymer addition points 30 to 50 cm is. 9. The method according to at least one of claims 1 to 8, characterized ge indicates that the cationic copolymer flocculant is a copolymer from an uncharged monomer from the group acrylamide, methacrylamide, Methyl or ethyl acrylate and methyl or ethyl methacrylate, and a katio nisch charged monomer from the group dimethylaminoethyl, Dime thylaminoethyl methacrylate, dimethylaminoethyl (meth) acrylate-butyl chloride quat., Dimethylaminoethyl (meth) acrylate-benzoyl chloride quat., [3- (meth) acrylo ylaminopropyl] trimethyl ammonium chloride, N- [3- (dimethylamino) pro pyl] (meth) acrylamide and diallyldimethylammonium chloride.   10. The method according to at least one of claims 1 to 9, characterized ge indicates that the cationic copolymer flocculant is a copolymer is used, which is 2.5 to 60, preferably 20 to 55, in particular 30 to Contains 50, especially 40 to 50 mol% of cationic Mereinheiten. 11. The method according to at least one of claims 1 to 10, characterized ge indicates that a cationic copolymer flocculant with a re reduced specific viscosity of from 3 to 30, preferably from 4 to 22, ins particular from 4 to 9, especially from about 5, is used. 12. The method according to at least one of claims 1 to 11, characterized ge indicates that the cationic copolymer flocculant is present in an amount from 0.005 to 0.25% by weight, preferably from 0.005 to 0.1% by weight, especially preferably from 0.005 to 0.075 wt .-%, based on the Gesamtfeststoffge the pulp slurry is used. 13. The method according to at least one of claims 1 to 12, characterized ge indicates that the cationic copolymer flocculant is a copolymer from the group of (meth) acrylamide / dimethylaminoethyl (meth) acrylate, Dime thylamino (meth) acrylate-methyl chloride quat., dimethylaminoethyl (meth) acrylate benzyl chloride quat., [3- (meth) acryloylaminopropyl] trimethylammonium chloride, N- [3- (dimethylamino) propyl] (meth) acrylamide and diallyldimethylam monium chloride copolymers is used. 14. The method according to at least one of claims 1 to 13, characterized ge indicates that the cationic copolymer flocculant is an acrylate mid / diallyldimethylammonium chloride copolymer is used, the 20 to 60 Contains mol% diallyldimethylammonium chloride mer units and a redu having a specific viscosity of from 4 to 30. A method for improving the retention of mineral fillers and cellulosic fibers on a cellulose fiber sheet comprising the steps of:

• a) Preparation of a Cellulose Pulp Slurry
• b) adding at least one water-soluble cationic copolymer flocculant to the cellulose pulp slurry;
• c) adding at least one water-soluble anionic polymer flocculant to the cellulose pulp slurry and
• d) forming a cellulosic fiber sheet from the cellulose pulp slurry containing both the cationic copolymer flocculant and the anionic polymer flocculant (s),

characterized in that

• 1. b ₁ ) in the step (b) a water-soluble cationic copolymer flocculant having a molecular weight of 5,000,000 to 15,000,000 in an amount of 0.001 to 0.5 wt .-%, based on the total solids content of the cellulose pulps Slurry, is used;
• 2. c ₁ ) in step (c) a water-soluble anionic polymer flocculant having a molecular weight of 5,000,000 to 25,000,000 in an amount of 0.001 to 0.5 wt .-%, based on the total solids content of the cellulose pulps Slurry, is used and
• 3. c ₂ ) the anionic polymer flocculant is added at a point 10 to 80 cm from the point of addition of the cationic copolymer flocculant.

16. The method according to at least one of claims 1 to 15, characterized ge indicates that the cellulose pulp slurry is between the stages (b) and (c) is sheared. 17. The method according to claim 15, characterized in that the Ab stood between the polymer addition points 30 to 50 cm.