EP1819875B1 - Method for producing paper with a high substance weight - Google Patents

Description

The present invention relates to a process for producing high basis weight papers, especially paperboard and paperboard by dewatering a stock on a wire in the presence of a combination of at least one amino group-containing polymer and at least one branched cationic polyacrylamide as retention and dewatering agents to form sheets and dry them Leaves.

Polyethyleneimines and modified polyethyleneimines as retention and drainage agents are known, for example, from the German Offenlegungsschrift DE 24 34 816 known. In the DE 24 34 816 and the literature cited therein describes the reactions of polyethyleneimine with crosslinkers such as epichlorohydrin, reactions of polyethylenimine or other oligoamines with oligocarboxylic acids to form polyamidoamines, crosslinked products of these polyamidoamines and reactions of the polyamidoamines with ethyleneimine and bifunctional crosslinkers.

Other modified polyethyleneimines are made WO 00/67884 A1 and WO 97/25367 known. In the processes described therein, the modified polyethyleneimines are obtained by ultrafiltration.

These modified polyethyleneimines are characterized in particular by a good drainage acceleration and formation, but weaknesses in the filler and fiber retention are known from practice.

It is likewise possible to use cationic polyacrylamides as retention aids, it being difficult to achieve an equivalent or improved dewatering effect with such retention aids. Such polyacrylamides are for example EP 0 176 757 A2 known.

Cationic polyacrylamides are also known in combination with other components as so-called microparticle systems. Generally, in the microparticle system, polymers such as modified polyethyleneimines or polyacrylamides are added as flocculants which are further flocculated by subsequent addition of inorganic microparticles such as bentonite or colloidal silica. The order of addition of the components can also be reversed.

EP 0 608 986 A1 discloses a process for producing filler-containing paper by adding an anionic component, such as bentonite, to the thick stock and then adding a cationic polymer to the stock.

Another microparticle system is out EP 0 335 575 A2 known, wherein a high molecular weight cationic polymer such as polyacrylamide is metered before the last shear stage to the fiber suspension. Subsequently, an inorganic component, which may be either bentonite or colloidal silica, is added after the last shear stage. For contaminant fixation, a modified polyethylenimine can also be used.

From the WO 98/01623 A1 there is known a process for the production of paper and board in which two different water-soluble polymers are added prior to a shear stage, wherein the polymers are a polyethyleneimine and another component selected from linear polyacrylamides, cationic starch or polymers containing vinylamine units , can act. After the shear stage, the addition of bentonite, colloidal silica or clay takes place.

Also the US 6,103,065 describes a microparticle system consisting of a cationic polymer, which may also be a polyethyleneimine, with a charge density> 4 meq / g, another cationic polymer such as a lower charge density linear polyacrylamide and a bentonite.

The "Wochenblatt für Papierfabrikation", 1977, 11/12, p. 397 et seq., Describes the combination of linear polyacrylamides and polyethylenimines. By this combination, both a good drainage by the polyethyleneimine and a good retention by the polyacrylamide should be achieved. Although this method is described as unsuccessful in the article, this combination is now recommended and used in practice to improve retention and drainage alike.

The EP 0 278 336 A2 describes aqueous solutions consisting of a modified polyamidoamine and a cationic, linear polyacrylamide. As the cationic group, the quaternization product of dimethylaminopropylacrylamide is described. This product is intended to simplify the handling of both types of paper adjuvant and also improve both retention and drainage.

All combinations have in common that either only retention or drainage can be improved.

However, especially for papers with high basis weights such as packaging papers and cardboard, both retention and drainage are equally important. This can not be achieved with the method known from the prior art.

It is an object of the present invention to provide a process for producing high basis weight papers using a papermaking system that improves both retention and drainage.

1. (a) mindestens ein aminogruppenhaltiges Polymer
   und
2. (b) mindestens ein verzweigtes kationisches Polyacrylamid

einsetzt.The object has been achieved by a method for producing high basis weight papers by dewatering a stock on a wire in the presence of a combination of at least two polymers as a retention and dewatering system to sheet and dry the sheets, wherein the sheet formation in the absence of finely divided inorganic Flocculants and one as retention and dehydrating agents

1. (a) at least one amino group-containing polymer
   and
2. (B) at least one branched cationic polyacrylamide

starts.

For the purposes of this invention, papers having high basis weights are understood as meaning those papers whose basis weight is at least 300 g / m ² , preferably at least 500 g / m ² , more preferably at least 750 g / m ² , very particularly preferably at least 1000 g / m ² and in particular at least 1500 g / m ² . There are no limits to the basis weights. Papers with basis weights of 2000 g / m ² or even 2500 g / m ² and more are quite common.

Papers with such high basis weights are, for example, packaging papers, cardboard and cardboard.

Amino-containing polymers are described in the literature. The individual references are hereby expressly and fully incorporated by reference.

1. a) die in der deutschen Offenlegungsschrift DE 24 34 816 beschriebenen stickstoffhaltigen Kondensationsprodukte. Diese werden durch Umsetzung von Polyamidoaminverbindungen mit Polyalkylenoxidderivaten, die an den endständigen Hydroxylgruppen mit Epichlorhydrin umgesetzt sind, erhalten. Die Umsetzung wird durchgeführt, in dem man
   1. (i) ein Gewichtsteil eines Polyamidoamins, das aus 1 Molteil einer Dicarbonsäure mit 4 bis 10 Kohlenstoffatomen und 0,8 bis 1,4 Molteilen eines Polyalkylenpolyamins mit 3 bis 10 Alkylenimineinheiten, das gegebenenfalls bis zu 10 Gew.-% eines Diamins enthält, erhalten worden ist und das gegebenenfalls bis zu 8 Ethylenimineinheiten pro basischer Stickstoffgruppierung aufgepfropft enthält, mit
   2. (ii) 0,3 bis 2 Gewichtsteilen eines Polyalkylenoxidderivates, das an den endständigen OH-Gruppen mit mindestens äquivalenten Mengen Epichlorhydrin umgesetzt ist, bei 20 bis 100°C reagieren lässt, und die reaktion bis zur Bildung hochmolekularer gerade noch wasserlöslicher Harze führt, die eine Viskosität von > 300 mPas (gemessen auf einem Brookfield-Viskosimeter in 20 %iger wässriger Lösung bei 20°C).
   
   Zur Herstellung solcher Kondensationsprodukte wird ausdrücklich und in vollem Umfang auf die Offenbarung der DE 24 34 816 verwiesen, insbesondere auf die Passage von Seite 4, 3. Absatz bis Seite 6 einschließlich.
2. b) die z. B. in der WO 97/25367 A1 beschriebenen Reaktionsprodukte von Alkylendiaminen oder Polyalkylenpolyaminen mit mindestens zwei funktionelle Gruppen enthaltenden Vernetzern. So erhältliche Polyethylenimine haben in der Regel eine breite Molmassenverteilung und mittlere Molmassen M_w, von beispielsweise 120 bis 2·10⁶, vorzugsweise 430 bis 1·10⁶. Zu dieser Gruppe gehören auch mit Ethylenimin gepfropfte und mit Bisglycidylethern von Polyethylenglykolen vernetzte Polyamidoamine, die in der US 4 144 123 beschrieben werden.
3. c) Reaktionsprodukte, die erhältlich sind durch Umsetzung von Michaeladditionsprodukten aus Polyalkylenpolyaminen, Polyamidoaminen, mit Ethylenimin gepfropften Polyamidoaminen sowie Mischungen der genannten Verbindungen und monoethylenisch ungesättigten Carbonsäuren, Salzen, Estern, Amiden oder Nitrilen mit mindestens bifunktionellen Vernetzern. Solche Reaktionsprodukte sind beispielsweise aus der WO 94/14873 A1 bekannt. Zu ihrer Herstellung kommen außer den halogenhaltigen Vernetzern besonders die beschriebenen Klassen von halogenfreien Vernetzern in Betracht.
4. d) wasserlösliche, vernetzte, teilweise amidierte Polyethylenimine, die aus der WO 94/12560 A1 bekannt und erhältlich sind durch
   • Reaktion von Polyethyleniminen mit einbasischen Carbonsäuren oder ihren Estern, Anhydriden, Säurechloriden oder Säureamiden unter Amidbildung und
   • Umsetzung der amidierten Polyethylenimine mit mindestens zwei funktionelle Gruppen enthaltenden Vernetzern.
   
   Die mittleren Molmassen M_w der in Betracht kommenden Polyethylenimine können bis zu 2 Mio. betragen und liegen vorzugsweise in dem Bereich von 1 000 bis 50 000. Die Polyethylenimine werden partiell mit einbasischen Carbonsäuren amidiert, so dass beispielsweise 0,1 bis 90, vorzugsweise 1 bis 50 %, der amidierbaren Stickstoffatome in den Polyethyleniminen als Amidgruppe vorliegt. Geeignete, mindestens zwei funktionelle Doppelbindungen enthaltende Vernetzer sind oben genannt. Vorzugsweise werden halogenfreie Vernetzer eingesetzt.
5. e) Polyethylenimine sowie quaternisierte Polyethylenimine. Es kommen hierfür z. B. sowohl Homopolymerisate von Ethylenimin als auch Polymere in Betracht, die beispielsweise Ethylenimin (Aziridin) aufgepfropft enthalten. Die Homopolymerisate werden beispielsweise durch Polymerisieren von Ethylenimin in wässriger Lösung in Gegenwart von Säuren, Lewis-Säuren oder Alkylierungsmitteln wie Methylchlorid, Ethylchlorid, Propylchlorid, Ethylenchlorid, Chloroform oder Tetrachlorethylen hergestellt. Die so erhältlichen Polyethylenimine haben eine breite Molmassenverteilung und mittlere Molmassen M_w, von beispielsweise 120 bis 2·10⁶, vorzugsweise 430 bis 1·10⁶.
   Die Polyethylenimine und die quaternisierten Polyethylenimine können gegebenenfalls mit einem mindestens zwei funktionelle Gruppen enthaltenden Vernetzer (siehe oben) umgesetzt sein. Die Quaternisierung der Polyethylenimine kann beispielsweise mit Alkylhalogeniden wie Methylchlorid, Ethylchlorid, Hexylchlorid, Benzylchlorid oder Laurylchlorid sowie mit beispielsweise Dimethylsulfat vorgenommen werden. Weitere geeignete modifizierte Polyethylenimine sind durch Strecker-Reaktion modifizierte Polyethylenimine, z. B. die Umsetzungsprodukte von Polyethyleniminen mit Formaldehyd und Natriumcyanid unter Hydrolyse der dabei entstehenden Nitrile zu den entsprechenden Carbonsäuren. Diese Produkte können gegebenenfalls mit einem mindestens zwei funktionelle Gruppen enthaltenden Vernetzer (siehe oben) umgesetzt sein.
   Außerdem eignen sich phosphonomethylierte Polyethylenimine und alkoxylierte Polyethylenimine, die beispielsweise durch Umsetzung von Polyethylenimin mit Ethylenoxid und/oder Propylenoxid erhältlich und in der WO 97/25367 A1 beschrieben sind. Die phosphonomethylierten und die alkoxylierten Polyethylenimine können gegebenenfalls mit einem mindestens zwei funktionelle Gruppen enthaltenden Vernetzer (siehe oben) umgesetzt sein.
6. f) weitere aminogruppenhaltige Polymere im Sinne der vorliegenden Erfindung sind alle unter a) bis e) genannten Polymere, die anschließend einer Ultrafiltration wie in WO 00/67884 A1 und WO97/23567 A1 beschrieben, unterzogen werden.

The polymers containing amino groups are generally water-soluble or dispersible amino group-containing polymers, in particular polyethyleneimines or modified polyethyleneimines. For the purposes of the present invention, these may be, in particular, the following amino-containing polymers or modified polyethylenimines:

1. a) in the German Offenlegungsschrift DE 24 34 816 described nitrogenous condensation products. These are obtained by reacting polyamidoamine compounds with polyalkylene oxide derivatives at the terminal Hydroxyl groups are reacted with epichlorohydrin. The implementation is carried out in which one
   1. (i) one part by weight of a polyamidoamine obtained from 1 part by mole of a dicarboxylic acid having 4 to 10 carbon atoms and 0.8 to 1.4 parts by mole of a polyalkylenepolyamine having 3 to 10 alkyleneimine units optionally containing up to 10% by weight of a diamine and optionally containing up to 8 ethyleneimine units per basic nitrogen group grafted with
   2. (ii) 0.3 to 2 parts by weight of a polyalkylene oxide derivative reacted at the terminal OH groups with at least equivalent amounts of epichlorohydrin, allowed to react at 20 to 100 ° C, and the reaction leads to the formation of high molecular weight just water-soluble resins, the a viscosity of> 300 mPas (measured on a Brookfield viscometer in 20% aqueous solution at 20 ° C).
   
   For the preparation of such condensation products is expressly and fully based on the disclosure of DE 24 34 816 including the passage from page 4, paragraph 3 to page 6 inclusive.
2. b) the z. B. in the WO 97/25367 A1 described reaction products of alkylenediamines or polyalkylenepolyamines with crosslinkers containing at least two functional groups. Polyethyleneimines thus obtainable generally have a broad molecular weight distribution and average molecular weights M _{w of} , for example, 120 to 2 × 10 ⁶ , preferably 430 to 1 × 10 ⁶ . Polyamidoamines grafted with ethyleneimine and crosslinked with bisglycidyl ethers of polyethylene glycols are also included in this group US 4,144,123 to be discribed.
3. c) reaction products which are obtainable by reaction of Michael addition products of polyalkylenepolyamines, polyamidoamines, ethyleneimine-grafted polyamidoamines and mixtures of said compounds and monoethylenically unsaturated carboxylic acids, salts, esters, amides or nitriles with at least bifunctional crosslinkers. Such reaction products are for example from WO 94/14873 A1 known. Apart from the halogen-containing crosslinkers, the described classes of halogen-free crosslinkers are particularly suitable for their preparation.
4. d) water-soluble, crosslinked, partially amidated polyethyleneimines which are known from the WO 94/12560 A1 are known and available through
   • Reaction of polyethyleneimines with monobasic carboxylic acids or their esters, anhydrides, acid chlorides or acid amides with amide formation and
   • Reaction of the amidated polyethyleneimines with crosslinkers containing at least two functional groups.
   
   The average molecular weights _{M.sub.w of} the polyethyleneimines contemplated can be up to 2 million and are preferably in the range from 1,000 to 50,000. The polyethylenimines are partially amidated with monobasic carboxylic acids such that, for example, 0.1 to 90, preferably 1 to 50% of the amidatable nitrogen atoms in the polyethyleneimines is present as the amide group. Suitable crosslinkers containing at least two functional double bonds are mentioned above. Preferably, halogen-free crosslinkers are used.
5. e) Polyethyleneimines and quaternized polyethyleneimines. It come for this z. B. both homopolymers of ethyleneimine and polymers into consideration, for example, ethyleneimine (aziridine) grafted contain. The homopolymers are prepared, for example, by polymerizing ethyleneimine in aqueous solution in the presence of acids, Lewis acids or alkylating agents such as methyl chloride, ethyl chloride, propyl chloride, ethylene chloride, chloroform or tetrachlorethylene. The polyethyleneimines thus obtainable have a broad molecular weight distribution and average molecular weights M _{w of} , for example, 120 to 2 × 10 ⁶ , preferably 430 to 1 × 10 ⁶ .
   The polyethyleneimines and the quaternized polyethyleneimines may optionally be reacted with a crosslinker containing at least two functional groups (see above). The quaternization of the polyethyleneimines can be carried out, for example, with alkyl halides, such as methyl chloride, ethyl chloride, hexyl chloride, benzyl chloride or lauryl chloride, and with, for example, dimethyl sulfate. Other suitable modified polyethyleneimines are Strecker reaction modified polyethyleneimines, e.g. As the reaction products of polyethyleneimines with formaldehyde and sodium cyanide with hydrolysis of the resulting nitriles to the corresponding carboxylic acids. These products may optionally be reacted with a crosslinker containing at least two functional groups (see above).
   Also suitable are phosphonomethylierte Polyethylenimine and alkoxylated polyethyleneimines, for example, by reacting polyethyleneimine with ethylene oxide and / or propylene oxide available and in the WO 97/25367 A1 are described. The phosphonomethylated and the alkoxylated polyethyleneimines may optionally be reacted with a crosslinker containing at least two functional groups (see above).
6. f) further polymers containing amino groups for the purposes of the present invention are all polymers mentioned under a) to e), which are subsequently subjected to ultrafiltration as in WO 00/67884 A1 and WO97 / 23567 A1 be described.

The amino-containing polymers or modified polyethylenimines are preferably selected from polyalkyleneimines, polyalkylenepolyamines, polyamidoamines, polyalkyleneglycol polyamines, polyamidoamines grafted with ethyleneimine and subsequently reacted with at least bifunctional crosslinkers, and mixtures and copolymers thereof. Preference is given to polyalkyleneimines, in particular polyethyleneimines, and the derivatives thereof. Particularly preferred are polyamidoamines which have been grafted with ethyleneimine and subsequently reacted with at least bifunctional crosslinkers.

In particular, the above-mentioned amino group-containing polymers under the in the DE 24 34 816 described polymers and in the WO 00/67884 A1 selected ultrafiltered amino group-containing polymers selected. These publications are hereby incorporated by reference.

In a particularly preferred embodiment of the process according to the invention, polymers are used as component (a) by condensation of C ₂ -C ₁₂ dicarboxylic acids, in particular adipic acid, with poly (alkylenediamines), in particular diethylenetriamine, triethylenetetramine and tetraethylenepentamine, or mono-, bis -, tris or tetra (aminopropyl) ethylenediamine or mixtures thereof, grafting of the polyamidoamines obtained in the condensation with ethyleneimine and subsequent crosslinking are available. It is preferred to graft with as much ethyleneimine that the polyamidoamine per grafted nitrogen basic group contains 2 to 50, preferably 5 to 10 Ethyleniminein grafted units. The grafted polyamidoamine is crosslinked by reaction with halogen-free, at least bifunctional crosslinkers, preferably bisglycidyl ethers of a polyalkylene glycol. Particularly preferred are bis-glycidyl ethers of polyethylene glycols having molecular weights between 400 and 5,000, in particular 500 to 3,000, such as. B. about 600 or about 2,000.

Component (b) of the retention and dewatering agent are those branched cationic polyacrylamides which, apart from acrylamide and at least one permanently cationic comonomer, contain a third difunctional or trifunctional unsaturated component which leads to the branching of the polymer chains. Such branched cationic polymers are, for example, in US 20030150575 described.

Preferably, in practice, the branched (co) polyacrylamide is a cationic copolymer of acrylamide and a non-saturated cationic ethylene monomer selected from dimethylaminoethyl acrylate (ADAME), dimethylaminoethylacrylamide, dimethylaminoethyl methacrylate (MADAME) which are quaternized or salified by various acids and quaternizing agents such as benzyl chloride, methyl chloride, alkyl or aryl chloride, dimethyl sulfate, furthermore dimethyldiallylammonium chloride (DADMAC), acrylamidopropyltrimethylammonium chloride (APTAC) and methacrylamidopropyltrimethylammonium chloride (MAPTAC). Preferred cationic comonomers are dimethylaminoethyl acrylate methochloride and dimethylaminoethylacrylamide methochloride, which are obtained by alkylation of dimethylaminoethyl acrylate or dimethylaminoethylacrylamide with methyl chloride.

This copolymer is branched, as known to those skilled in the art, through a branching agent consisting of a compound having at least two reactive moieties selected from the group comprising double, aldehyde or epoxy bonds. These compounds are known and are for example in the document EP 0 374 458 A1 described.

As is known, a branched polymer is a polymer having branches, groups or branches in its entirety, which are not arranged in three directions as a whole in one plane and in contrast to a cross-linked polymer; such high molecular weight branched polymers are well known as flocculants in papermaking. These branched polyacrylamides differ from the crosslinked polyacrylamides in the fact that in these latter groupings are arranged three-dimensionally to result in practically insoluble products of infinite molecular weight.

The branching may preferably be accomplished during (or optionally after) the polymerization, for example by reaction of two soluble polymers having counterions, or by reaction via formaldehyde or a polyvalent metal compound. Often the branching takes place during polymerization by the addition of a branching agent, this solution being preferred in practice. Branching polymerization processes are well known.

These branching agents which can be incorporated include ionic branching agents such as polyvalent metal salts, formaldehyde, glyoxal or, preferably, covalent crosslinking agents which copolymerize with the monomers, preferably diethylene-unsaturated monomers (such as the family of diacrylate esters such as the diacrylates of polyethylene glycols PEG ), or polyethylene-unsaturated monomers of the type conventionally used for crosslinking water-soluble polymers especially methylene bisacrylamide (MBA) or any of the other known acrylic branching agents.

These agents are often identical to the crosslinking agents, but if a branched and uncrosslinked polymer is to be obtained, crosslinking can be achieved by optimizing polymerization conditions such as concentration in the polymerization, type and amount of the transfer agent, temperature, type and amount of the initiators like, can be prevented.

In practice, the branching agent is methylenebisacrylamide (MBA), which is added at five to two hundred (5 to 200), preferably 5 to 50, moles per million moles of the monomer.

The degree of branching of the branched cationic polyacrylamides is referred to as so-called "ionic regain" (ionic recovery RI). This is a difference in the cationic charge density in meq / g before and after shearing the sample to be measured (RI = (XY) / Y x 100, with RI = ion recovery, X = charge density after shear in meq / g, Y = Charge density before shearing in meq / g). This method is in US 20030150575 described in more detail.

In erfindungsgmäßen method are preferably those branched cationic polyacrylamides used which have an RI of> 20%, preferably> 40%.

Of course, it is also possible to use branched cationic polyacrylamides which consist of a mixture of branched and linear polyacrylamides, as described in the prior art, by the process according to the invention. Such a mixture usually consists of a branched cationic polyacrylamide as described above and a linear polyacrylamide in a ratio of 99: 1 to 1: 2, preferably in a ratio of 90: 1 to 2: 1, and particularly preferably in a ratio of 90: 1 to 3: 1.

In the case of a mixture of branched cationic polyacrylamides and linear polyacrylamides, mixtures are preferably used in which at least 10 mol% of a cationic monomer, as listed above for component (b), preferably at least 20 mol% of a cationic monomer.

In the process according to the invention, components (a) and (b) are preferably used as water-in-oil emulsions.

In the process according to the invention, component (a) is preferably fixed in an amount of 100 g to 3 kg, ie pure active substance without solvent of the emulsion, based on one ton of dry paper, preferably in the range of 150 g 2.0 kg, based on one ton of dry paper and more preferably in the range of 200 g to 1.2 kg, based on one ton of dry paper

The component (b) is fixed in a range of from 50 g to 800 g, i. pure active substance without solvent of the emulsion, based on one ton of dry paper, preferably in the range from 65 g to 600 g, based on one ton of dry paper and more preferably in the range of 80 g to 400 g, based on one ton of dry paper.

Although the ratio of components (a) and (b) can be chosen as desired, components (a) and (b) are preferably used in a ratio of at least 2: 1, preferably at least 3: 1 and more preferably at least 4: 1. The retention and dehydrating agent system can be fed to the paper stock-as a rule, the dosing of the retention and dewatering agent takes place in the thin material-for example in the form of a mixture of components (a) and (b). However, it is also possible to proceed by metering component (a) and then component (b) first, for example after the last shear stage in front of the headbox. However, both components can also be introduced into the thin material separately from one another before or after a shear stage. Most advantageously, at least one compound of component (a) is metered in, followed by at least one compound of component (b). The compound of component (a) can be supplied to the stock, for example, before a shear stage and the compound of component (b) after the last shear stage before the headbox. However, both compounds can be dosed before the last shear stage before the headbox or after the last stage before the headbox for pulp. However, it is also possible to meter the component (a) into the thin material at various points and to allow shearing forces to act on the system and to add the component before or after the last shear stage before the headbox. It is likewise possible first to add component (b) to the paper stock and then to meter component (a) of the retention agent.

1. (a) mindestens einem aminogruppenhaltigen Polymer
   und
2. (b) mindestens einem verzweigten kationischen Polyacrylamid

als alleiniges Retentions- und Entwässerungsmittel in einem Verfahren zur Herstellung von Papieren mit hohen Flächengewichten, wobei das Flächengewicht des Papiers wenigstens 300 g/m² beträgt.The present invention is also the use of the combination of

1. (a) at least one amino group-containing polymer
   and
2. (B) at least one branched cationic polyacrylamide

as a sole retention and drainage agent in a process for producing high basis weight papers, wherein the basis weight of the paper is at least 300 g / m ² .

In particular, papers of high basis weight can be produced by the process according to the invention, as described above. For example, wood pulp, thermo-mechanical pulp (TMP), chemo-thermo-mechanical pulp (CTMP), pressure pulp (PGW) and sulfite and sulfate pulp can be used. As raw materials for the production of pulp and pulp and mechanical pulp as well as waste paper and coated broke into consideration. Wood pulp and pulp are further processed into paper, especially in the so-called integrated paper mills, in more or less moist form directly without prior thickening or drying. Due to the impurities not completely removed therefrom, these fiber materials still contain substances that greatly disrupt the usual papermaking process. If such pulps are used, it is advisable to work in the presence of a fixative. In particular, 100% recovered paper is used for the production of high basis weight papers

Both unfilled and filler-containing papers can be produced by the process according to the invention. The filler content in the paper may be up to a maximum of 40% by weight and is preferably in the range of 5 to 30% by weight. Examples of suitable fillers are clay, kaolin, native and precipitated chalk, titanium dioxide, talc, calcium sulfate, barium sulfate, aluminum oxide, satin white or mixtures of the stated fillers.

The papermaking can be carried out in the presence of the usual process chemicals in the usual amounts, e.g. bulk sizing agents, such as in particular alkyldiketene dispersions, rosin size, alkenylsuccinimide dispersions or sizing polymer dispersions, solidifying agents such as epichlorohydrin-crosslinked polyamidoamines, polyvinylamines of average molecular weight or strength, fixatives, biocides, dyes and fillers. The dosage of the usual process auxiliaries is preferably carried out in the thin material.

The process according to the invention gives papers of high basis weights with improved retention, especially in the case of fillers, and dewatering, as compared with the products prepared by known processes. Furthermore, the process according to the invention is simpler to carry out in comparison with the microparticle processes.

In the examples, the percentages for the starting materials always mean percent by weight.

• Polyethylenimin (PEI): HM Polymin^® der BASF Aktiengesellschaft
• Polymer A: lineares kationisches Polyacrylamid, mittelmolekular mit 30 mol-% kationischem Anteil (Polymin^® KE 2035 der BASF Aktiengesellschaft)
• Polymer B: lineares kationisches Polyacrylamid, hochmolekular mit 30 mol-% kationischem Anteil (Polymin^® PR 8241 der BASF Aktiengesellschaft)
• Polymer C: lineares kationisches Polyacrylamid, hochmolekular mit 50 mol-% kationischem Anteil
• Polymer D: verzweigtes kationisches Polyacrylamid, RI = 70 % mit 30 mol-% kationischem Anteil (Polymin^® PR 8282 der BASF Aktiengesellschaft)
• Polymer E: verzweigtes kationisches Polyacrylamid, RI = 50 % mit 30 mol-% kationischem Anteil
• Polymer F: verzweigtes kationisches Polyacrylamid, RI = 50 % mit 50 mol-% kationischem Anteil

The following polymers were used in the examples:

• Polyethyleneimine (PEI): HM Polymin® ^® from BASF Aktiengesellschaft
• Polymer A: linear polyacrylamide, cationic, medium molecular with 30 mole% cationic portion (Polymin ^® KE 2035 BASF Aktiengesellschaft)
• Polymer B: linear cationic polyacrylamide, high molecular weight with 30 mole% cationic portion (Polymin ^® PR 8241 of BASF Aktiengesellschaft)
• Polymer C: linear cationic polyacrylamide, high molecular weight with 50 mol% cationic content
• Polymer D: branched cationic polyacrylamide, RI = 70% with 30 mole% cationic portion (Polymin ^® PR 8282 of BASF Aktiengesellschaft)
• Polymer E: branched cationic polyacrylamide, RI = 50% with 30 mol% cationic portion
• Polymer F: branched cationic polyacrylamide, RI = 50% with 50 mol% cationic portion

example

• In einem 1 l Becherglas wurde 1 I einer 1 gew.-%igen Stoffsuspension aus 100 % Altpapier eingefüllt. In einem zweiten 1 l Becherglas wurden die in der Tabelle 1 angegebenen Mengen des Retentions- und Entwässerungssystems bestehend aus HM Polymin^® und den entsprechenden Polymere A bis F gefüllt. Die Stoffsuspension wurde zum Retentions- und Entwässerungssystem gegeben und durch mehrmaliges Umschütteln miteinander vermischt. Anschließend wird das Gemisch mit Hilfe eines Vakuums über ein Filtersieb zügig abgesaugt, wobei Turbulenzen zu vermeiden sind. Sobald das Vakuum ein Minimum erreicht hat, wird der Druck (P1) gemessen. Nach einer Minute wird der angestiegene Druck (P2) erneut gemessen. Das Vakuum wird entfernt und die feuchte Fasermatte wird vom Sieb genommen und gewogen (Gewicht G1). Anschließend wird die Fasermatte bei 105°C bis zur Massenkonstanz getrocknet und erneut gewogen (Gewicht G2). Der Trockengehalt in % und damit die Entwässerungsleistung ergibt sich aus (G1 - G2)/G2 x 100.

Dewatering time for high basis weight papers is determined under vacuum according to the following method:

• 1 l of a 1% by weight stock suspension made from 100% waste paper was introduced into a 1 l beaker. In a second 1 L beaker, the amounts of the retention and drainage system shown in the Table 1 were filled consisting of Polymin ^® HM and the respective Polymers A-F. The stock suspension was added to the retention and drainage system and mixed by shaking several times. Subsequently, the mixture is rapidly sucked off with the aid of a vacuum via a filter screen, whereby turbulences are to be avoided. Once the vacuum has reached a minimum, the pressure (P1) is measured. After one minute, the increased pressure (P2) is measured again. The vacuum is removed and the wet fiber mat is removed from the sieve and weighed (weight G1). Subsequently, the fiber mat is dried at 105 ° C to constant mass and weighed again (weight G2). The dry content in% and thus the dewatering performance results from (G1 - G2) / G2 x 100.

With the different polymer combinations two series of experiments I and II were carried out with different concentrations.

In the experiments 2 to 7, the data for the dosage amounts to the polymers A to F. In all experiments 2 to 7 were additionally 0.8 kg solid / t dry paper used. Table 1 Experiment No. polymers Dosing amount [kg solid / t dry paper] Dry content [%] I II I II 1 HM Polymin® ^® 0.4 0.8 26.8 26.2 2 Polymin ^® HM + Polymer A 0.2 0.3 25.9 24.5 3 Polymin ^® HM + Polymer B 0.2 0.3 26.3 25.5 4 Polymin ^® HM + Polymer C 0.2 0.3 25.9 25.3 5 Polymin ^® HM + Polymer D 0.2 0.3 28.0 27.5 6 HM Polymin® ^® + Polymer E 0.2 0.3 28.5 27.8 7 Polymin ^® HM + Polymer F 0.2 0.3 27.8 27.6

Claims (12)

1. A process for producing paper of high basis weight by draining a paper pulp on a wire in the presence of a combination of at least two polymers as a retention and drainage aid system, forming sheets, and drying the sheets, which comprises forming the sheets in the absence of finely divided inorganic flocculants and using as retention and drainage aids

   a. at least one amino-containing polymer
   and

   b. at least one branched cationic polyacrylamide, and the basis weight of the paper being at least 300 g/m².
2. The process according to claim 1, wherein the amino-containing polymer is a polyethylenimine or a modified polyethylenimine.
3. The process according to claim 2, wherein the modified polyethylenimine is obtained by reacting a polyamidoamine compound with a polyalkylene oxide derivative whose terminal hydroxyl groups have been reacted with epichlorohydrin.
4. The process according to any one of claims 1 to 3, wherein the amino-containing polymer has been subjected to ultrafiltration.
5. The process according to any one of claims 1 to 4, wherein the branched cationic polyacrylamide is a cationic copolymer of acrylamide and an unsaturated cationic ethylene monomer.
6. The process according to claim 5, wherein the unsaturated cationic ethylene monomer is selected from dimethylaminoethyl acrylate methochloride and dimethylaminoethylacrylamide methochloride.
7. The process according to either of claims 5 and 6, wherein methylenebisacrylamide is used as branching agent.
8. The process according to any one of claims 1 to 7, wherein the branched cationic polyacrylamide has an ionic regain RI of > 20%.
9. The process according to any one of claims 1 to 8, wherein the branched cationic polyacrylamide has an ionic regain RI of > 40%.
10. The process according to any one of claims 1 to 9, wherein the branched cationic polyacrylamide is a mixture of a branched cationic polyacrylamide and a linear polyacrylamide in a ratio of 99:1 to 1:2.
11. The process according to any one of claims 1 to 10, wherein components (a) and (b) of the retention and drainage aid system are used, based on one metric tonne of dry paper, in an amount of

    a. 100 g to 3 kg solids, preferably 150 g to 2.0 kg
    and

    b. 50 g to 800 g, preferably 65 g to 600 g.
12. The use of a combination of

    c. at least one amino-containing polymer
    and

    d. at least one branched cationic polyacrylamide

    as sole retention and drainage aid in the production of paper of high basis weight, the basis weight of the paper being at least 300 g/m².