DE20220981U1 - Preparation of paper, pasteboard, or cardboard involving cutting of the paper pulp, addition of microparticles of cationic polymer, e.g. cationic polyamide, and a finely divided inorganic component after the last cutting step - Google Patents

Abstract

A process for preparation of paper, pasteboard, or cardboard involving cutting of the paper pulp, addition of microparticles of cationic polymer, and a finely divided inorganic component after the last cutting step and before pulp swelling, dewatering of the pulp, and sheet formation and drying of the sheets is new. A process for preparation of paper, pasteboard, or cardboard involving cutting of the paper pulp, addition of microparticles of cationic polymer, and a finely divided inorganic component after the last cutting step and before pulp swelling, dewatering of the pulp, and sheet formation and drying of the sheets. The cationic polymer of the microparticle system is cationic polyacrylamide, polymer containing vinylamine units, and/or polydiallyl dimethylammonium chloride containing polymer of mean mol.wt. 500,000 Dalton, and maximum charge density 4.0 meq/g, where the microparticle system free from polymers of charging density (sic) more than 4 meq/g is used as the retention agent.

Description

The The invention relates to a microparticle system from a cationic Polymers and a finely divided inorganic component for the production of Paper, cardboard and cardboard, being

• - the Paper pulp is sheared,
• - the Microparticle system for the paper stock after the last shear stage is added before the headbox, and
• - the Paper stock is dewatered with sheet formation and drying of the leaves.

The Use of combinations of non-ionic or anionic Polymers and bentonite as retention aids in the manufacture of paper is known for example from US-A-3,052,595 and EP-A-O 017 353 known.

Out EP-A-0 223 223 is a process for the production of paper and cardboard through drainage a paper stock is known, where a paper stock with a Substance concentration of 2.5 to 5% by weight first of all adding bentonite, then dilute the paper stock, a highly cationic polymer with a charge density of at least 4 meq / g adds up and finally a high molecular polymer based on acrylamide and the pulp thus obtained is dewatered after mixing.

To the process known from EP-A-O 235 893 for the production of Paper is metered into an aqueous fiber suspension first a substantially linear synthetic cationic polymer with a molecular weight of more than 500,000 in an amount of more than 0.03% by weight, based on dry paper stock, the Mix then the action of a shear field, whereby the initially created Flakes can be broken up into microflakes that have a cationic charge wear, then doses bentonite and dewatered the pulp thus obtained without further exposure to shear forces.

EP-A-O 335 575 describes a paper making process in which the pulp successively with 2 different water-soluble, cationic polymers offset, then subjected to at least one shear step and then by adding Bentonite is flaked.

In EP-A-0 885 328 describes a process for the production of paper described, whereby to an aqueous fiber suspension first doses a cationic polymer, the mixture then acts subject to a shear field, then an activated bentonite dispersion admits and dewatered the pulp thus obtained.

Out EP-A 0 711 371 is a further process for the production of Known paper. This process uses a synthetic, cationic, high molecular weight Polymer added to a thick cellulose suspension. After this Dilute the flocculated thick matter becomes a coagulant before dewatering, that of an inorganic coagulant and / or a second, low molecular weight and highly cationic water-soluble polymer is added.

In EP-A-0 910 701 describes a process for the production of paper and cardboard described, one for the paper pulp one after the other low molecular or medium molecular cationic polymer Based on polyethyleneimine or polyvinylamine and then with a high molecular weight cationic polymer such as polyacrylamide, polyvinylamine or cationic strength added. After this pulp is subjected to at least one shear step was flocculated by adding bentonite and the paper stock dewatered.

Out EP-A-0 608 986 is known to be used in papermaking dosed a cationic retention agent to the thick matter. Another one Process for the production of paper and cardboard is known from US-A-5,393,381, WO-A-99/66130 and WO-A-99/63159 known, wherein you also a microparticle system from a cationic Polymer and bentonite used. A is used as the cationic polymer water-soluble, branched polyacrylamide used.

In WO-A-0/34910 describes a process for the production of paper, in which a polysaccharide or a synthetic, high molecular polymer is metered. Then mechanical shear of the paper stock. The reflocculation is done by dosage an inorganic component such as silica, bentonite or clay and of a water soluble Polymer.

Out US-A-6,103,065 is a method for improving retention and the drainage of Paper stocks known, going to a paper stock after the last one Shear a cationic polymer with a molecular weight of 100,000 up to 2 million and a charge density of more than 4.0 meq./g adds, simultaneously or afterwards a polymer with a molecular weight of at least 2 million and a charge density of less than 4.0 meq./g and then metered bentonite. It is with this procedure does not need the pulp after adding the polymers subject to shear. After adding the polymers and the Bentonite can take the pulp under no further shear forces Leaf formation drained become.

With the known paper manufacturing processes, where a microparticle system is used as the retention agent, larger amounts of polymer and bentonite are required. Those processes which require the use of cationic polymers with a charge density of more than 4.0 result in papers which tend to yellowing.

The The present invention has for its object a microparticle system for a Process for making paper using the microparticle system to disposal to provide, compared to the known methods lower Amounts of polymers and bentonite needed, at the same time an improved Retention and drainage achieved and received papers, who are less prone to yellowing.

• – der Papierstoff geschert wird,
• – das Mikropartikelsystem zum Papierstoff nach der letzten Scherstufe vor dem Stoffauflauf zugegeben wird, und
• – der Papierstoff unter Blattbildung und Trocknen der Blätter entwässert wird.

wobei man als kationische Polymere des Mikropartikelsystems kationische Polyacrylamide, Vinylamineinheiten enthaltende Polymere und/oder Polydiallyldimethylammoniumchlorid mit einer mittleren Molmasse Mw von jeweils mindestens 500 000 Dalton und einer Ladungsdichte von jeweils höchstens 4,0 meq./g einsetzt, wobei das als Retentionsmittel eingesetzte Mikropartikelsystem frei von Polymeren mit einer Ladungsdichte von mehr als 4 meq./g ist.The object is achieved according to the invention with a microparticle system composed of a cationic polymer and a finely divided inorganic component for the production of paper, cardboard and cardboard, wherein

• - the paper stock is sheared,
• - The microparticle system is added to the paper stock after the last shear stage before the headbox, and
• - The paper stock is dewatered with sheet formation and drying of the sheets.

wherein cationic polyacrylamides, polymers containing vinylamine units and / or polydiallyldimethylammonium chloride with an average molecular weight Mw of at least 500,000 daltons and a charge density of at most 4.0 meq./g each are used as cationic polymers of the microparticle system, the microparticle system used as a retention agent being free of polymers with a charge density of more than 4 meq./g.

To the procedure can all paper qualities be produced, e.g. Carton, single / multi-layer folding box, single / multi-layer liner, corrugated material, papers for newspaper printing, so-called medium fine writing and printing papers, gravure papers and lightweight coating base papers. To make such papers can be, for example, of ground wood, thermomechanical material (TMP), chemothermomechanical material (CTMP), pressure cut (PGW), Wood pulp and sulfite and sulfate pulp run out. The pulps can both be short-fiber as well as long-fiber. Preferably after the process wood-free qualities manufactured, the bright white Result in paper products.

The Papers can optionally up to 40 wt .-%, mostly 5 to 35 wt .-% fillers contain. Suitable fillers are e.g. Titanium dioxide, natural and anticipated Chalk, talc, kaolin, satin white, calcium sulfate, barium sulfate, Clay or alumina.

The According to the invention, the microparticle system consists of a cationic polymer and a fine-particle anionic component. As cationic polymers come cationic polyacrylamides containing vinylamine units Polymers, polydiallyldimethylammonium chlorides or mixtures thereof with an average molecular weight Mw of at least 500,000 daltons each and a charge density of at most 4.0 meq./g. Cationic polyacrylamides with a average molecular weight Mw of at least 5 million daltons and one Charge density from 0.1 to 3.5 meq./g and polyvinylamines that pass through Hydrolysis of polymers containing vinylformamide units are available, where the degree of hydrolysis of the vinylformamide units is 20 to 100 mol% and the average molecular weight of the polyvinylamines is at least 2 million Dalton is. The polyvinylamines are preferred by hydrolysis of homopolymers made of vinylformamide, the degree of hydrolysis for example Is 70 to 95%.

cationic Polyacrylamides are, for example, copolymers which are obtained by copolymerizing Acrylamide and at least one di-Cl-bisC2-alkylamino-C2-bisC4-alkyl (meth) acrylate or a basic acrylamide in the form of the free bases, the salts with organic or inorganic acids or with alkyl halides quaternized compounds available are. examples for such compounds are dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, Dimethylaminoethyl acrylate, diethylaminoethyloacrylyate, dimethylaminopropyl methacrylate, Dimethylaminopropyl acrylate, diethylaminopropyl methacrylate, diethylaminopropyl acrylate and / or dimethylaminoethyl acrylamide. More examples of cationic Polymers containing polyacrylamides and vinylamine units can references cited to the prior art, such as EP-A-O 910 701 and US-A-6,103,065. One can use both linear as well as use branched polyacrylamides. Such polymers are commercial Products. Branched polymers, e.g. by copolymerization of Acrylamide or methacrylamide with at least one cationic monomer can be prepared in the presence of small amounts of crosslinkers for example in the literature cited for the prior art US-A-5,393,381, WO-A-99/66130 and WO-A-99/63159.

Further suitable cationic polymers are polydiallyldimethylammonium chlorides (PolyDADMAC) with an average molecular weight of at least 500,000 Daltons, preferably at least 1 million Daltons. Polymers of these Kind are commercial products.

The cationic polymers of the microparticle system become the paper stock in an amount of 0.005 to 0.5% by weight, preferably in an amount from 0.01 to 0.2% by weight.

As inorganic components of the microparticle system come for example Bentonite, colloidal silica, Silicates and / or calcium carbonate. Taking colloidal silica products based on silicates should be understood, e.g. Silica microgel, silica sol, polysilicates, aluminum silicates, borosilicates, Polyborate silicates, clay or zeolites. Calcium carbonate can for example in the form of chalk, ground calcium carbonate or precipitated Calcium carbonate as an inorganic component of the microparticle system be used. Layered silicates are generally used under bentonite understood that are swellable in water. It is this especially the clay mineral montmorrillonite and similar Clay minerals such as nontronite, hectorite, saponite, sauconite, beidellite, allevardite, Illite, halloysite, attapulgite and sepiolite. These layered silicates are preferably activated before their application, i.e. in a converted into water swellable form, in which one of the layered silicates with an aqueous base such as aqueous solutions of Sodium hydroxide solution, potassium hydroxide solution, soda or potash treated. Preferably is used as the inorganic component of the microparticle system Bentonite in the form treated with sodium hydroxide solution. The platelet diameter of the bentonite dispersed in water is in the form treated with sodium hydroxide solution for example 1 to 2 µm, the thickness of the platelets is around 1 nm. Depending on the type and activation, the bentonite has a specific surface from 60 to 800 m² / g. Typical bentonites are e.g. in EP-B-0235893. In the papermaking process, bentonite becomes the cellulose suspension typically in the form of an aqueous Bentonite slurry added. This bentonite slurry can contain up to 10% by weight. Contain bentonite. Usually the slurries contain approx. 3 - 5% by weight Bentonite.

As colloidal silica can Products from the group of silicon-based particles, silica microgels, Silica brine, aluminum silicates, borosilicates, polyborosilicates or Zeolite can be used. These have a specific surface of 50-1000 m² / g and an average particle size distribution of 1 - 250 nm, usually in the range 40 - 100 nm. The manufacture of such components is e.g. in EP-A-0041056, EP-A-0185068 and US-A-5176891.

Clay or also kaolin is a water-containing aluminum silicate with a plate-like structure. The crystals have a layer structure and an aspect ratio (ratio diameter to thickness) of up to 30: 1. The particle size is at least 50 less than 2 mm.

As Carbonates, preferably calcium carbonate, can be natural calcium carbonate (ground calcium carbonate, GCC) or precipitated Calcium carbonate (precipitated calcium carbonate, PCC) can be used. GCC is made by grinding and classifying processes using grinding aids manufactured. It has a particle size of 40 - 95% smaller than 2 mm, the specific surface is in the range of 6 - 13 m² / g. PCC is produced by introducing carbon dioxide into calcium hydroxide solution. The average particle size is in the range of 0.03 - 0.6 mm, the specific surface can vary greatly through the choice of precipitation conditions to be influenced. It is in the range of 6 - 13 m² / g.

The The paper pulp becomes the inorganic component of the microparticle system in an amount of 0.01 to 1.0% by weight, preferably in an amount from 0.1 to 0.5% by weight.

The Pulp consistency is for example 1 to 100 g / l, preferably 4 to 30 g / l. The aqueous fiber slurry will subject to at least one shear step. It goes through it at least one cleaning, mixing and / or pumping stage. The shearing the pulp can be, for example, in a pulper, sifter or in one Refiner done. After the last shear step and before the headbox According to the invention, the microparticle system is metered onto the sieve. A method of operation in which one is the first is particularly preferred the cationic polymer and then the inorganic component of the microparticle system dosed to the paper stock that previously sheared has been. However, you can also first the inorganic component of the microparticle system and beyond meter the cationic polymer or the pulp both components simultaneously to admit. Then drainage takes place of the paper stock without further action by shear forces a sieve with leaf formation. The paper sheets are then dried.

Moreover Microparticle system can usually be the paper stock Process chemicals used in papermaking in the usual Add quantities, e.g. Fixatives, dry and wet strength agents, Bulk sizing agents, biocides and / or dyes.

With the procedure is opposed the known methods an increase retention of fine and fillers as well as process chemicals such as Strength, Dyes and wet strength agents, and achieved an improvement in drainage speed, without deteriorating the formation and paper properties. Moreover a significant improvement in fiber recovery and thus relieving the wastewater treatment plant.

The percentages in the examples be indicate weight percent, unless the context indicates otherwise.

The First pass retention (FP retention) was determined by determining the ratio the solids content in the white water to the solids content in the headbox determined. The information is given in percent.

The FPA retention (first pass ash retention) was analogous to FP retention was determined, but only the ash content was taken into account.

example 1

On Pulp made from a wood-free, bleached pulp with a Material density of 7 g / l and a filler content of 30% calcium carbonate became paper on a Fourdrinier machine with hybrid former with writing and printing quality processed. The following arrangement of mixing and shearing devices was used: mixing chest, dilution to 7 g / l, mixing pump, cleaner, headbox pump, screen and headbox. 32 t of paper were produced per hour.

To the screen (last shear stage before the headbox) was dosed first 270 g / t of a commercially available high molecular weight, cationic polyacrylamide (Polymin PR 8140, medium Molar mass Mw 7 million) and then 2500 g / t bentonite. The FP retention was 81.5%, the FPA retention) 60.2%.

Comparative Example 1

The Example would repeated with the exceptions that 410 g / t of the cationic Polyacrylamids before screen and pump and 3000 g / t bentonite after screen dosed before the headbox. These quantities were required to achieve the same good formation as in the example. The FP retention was 79.9%, FPA retention 59.1%.

How a comparison of the results of the example with the results of the Comparative example shows, the saving in polymer was 30% and the bentonite savings of 17%. With equally good formation could in the example according to the invention an improvement in retention can be achieved. The improvement with screen drainage was about 10%.

Example 2

On Wood-containing pulp made from ground wood and cellulose with a Consistency of 7 g / l and a filler content of 30% Mixture of clay and calcium carbonate (1: 1) was made on paper machine processed with a gap former into LWC-quality paper. The following arrangement of mixing and shearing devices was used: Mixing chest, dilution, deculator, Pump, screen, headbox. 30 tons of paper were produced per hour.

To the screen (last shear stage before the headbox) was dosed first 200 g / t of a commercially available high molecular weight cationic polyacrylamide (Polymin KP 2520, medium Molar mass Mw 5 million) and then 1400 g / l bentonite. The FP retention was 69%, FPA retention 40%.

Comparative Example 2

The Example 2 was repeated with the exception that 280 g / t the cationic polyacrylamide before the pump and the screen and Dosed 1400 g / t bentonite after the screen before the headbox. This amount was necessary to achieve an equally good retention. The FP retention was 69%, the FPA retention 40%.

How a comparison of the results of Example 2 with the results of Comparative Example 2 shows the savings in polymer about 30%. Although in Example 2 a smaller amount of retention aid when used in comparative example 2, in example 2 an equally good formation and paper properties can be achieved.

Claims (10)

Microparticle system consisting of a cationic polymer and a finely divided inorganic component for the production of paper, cardboard and cardboard, whereby - the paper stock is sheared, - the microparticle system is added to the paper stock after the last shear stage before the headbox, and - the paper stock with sheet formation and drying of the Leaves are dewatered, characterized in that cationic polyacrylamides, polymers containing vinylamine units and / or polydiallyldimethylammonium chloride with an average molecular weight Mw of at least 500,000 daltons each and a charge density of at most 4.0 meq./g each are used as cationic polymers of the microparticle system, wherein the microparticle system used as a retention agent is free of polymers with a charge density of more than 4 meq./g. Microparticle system according to claim 1, characterized in that that as cationic polymers of the microparticle system polyacrylamides with an average molecular weight Mw of at least 5 million daltons and a charge density of 0.1 to 3.5 meq./g. Microparticle system according to claim 1, there characterized in that the cationic polymers of the microparticle system used are polyvinylamines which can be obtained by hydrolysis of polymers containing vinylformamide units, the degree of hydrolysis of the vinylformamide units being 20 to 100 mol% and the average molar mass of the polyvinylamines being at least 2 million daltons. Microparticle system according to one of claims 1 to 3, characterized in that the cationic polymer of the microparticle system the paper stock in an amount of 0.005 to 0.5% by weight on dry paper stock. Microparticle system according to one of claims 1 to 4, characterized in that the cationic polymer of the microparticle system the paper stock in an amount of 0.01 to 0.2 wt .-%, based on dry paper stock. Microparticle system according to one of claims 1 to 5, characterized in that one as an inorganic component of the microparticle system at least one bentonite, colloidal silica, silicates and / or calcium carbonate. Microparticle system according to one of claims 1 to 6, characterized in that the inorganic component of Microparticle system the paper stock in an amount of 0.01 to 1.0% by weight, based on dry paper stock, is added. Microparticle system according to one of claims 1 to 7, characterized in that the inorganic component of Microparticle system the paper stock in an amount of 0.1 to 0.5% by weight, based on dry paper stock, is added. Microparticle system according to one of claims 1 to 8, characterized in that first the cationic polymer and then the inorganic component of the microparticle system dosed to the paper stock. Microparticle system according to one of claims 1 to 8, characterized in that first the inorganic component and then the cationic polymer of the microparticle system to the pulp dosed.