DD269755A3 - METHOD FOR SOLIDENTRETENTION AND TEMPERATURE ACCELERATION IN PAPER MANUFACTURE - Google Patents

Abstract

Process for solids retention and dewatering acceleration in papermaking used in the paper industry. For this purpose, a highly branched, high molecular weight, water-soluble copolymer of dimethyl diallyl-ammonium chloride and 0.1 to 3.0 mol% of a crosslinking comonomer in amounts of 0.01 to 0.5% based on the content of the paper-forming suspension of fiber raw materials and Additives, added to this suspension and the papermaking carried out in a known manner.

Description

Field of application of the invention

The invention relates to a method for dewatering acceleration and retention of fiber, fillers and fines in papermaking, while reducing wastewater treatment. The method is suitable for the production of various types of cardboard or paper, which are characterized by different Faserroh- and aggregates.

Characteristic of the known state of the art

In papermaking, the fiber raw materials, z. As groundwood or ground pulp or shredded waste paper, usually with other additives such. As fillers or mineral pigments, as an aqueous suspension to an endless moving screen belt. Large amounts of water are removed and a leaf is formed. This sheet is then further mechanically dehydrated and dried. The prerequisite for high productivity of paper machines with good material economy is the use of process engineering tools. As such, the so-called retention agents or drainage accelerators are used. Above all, they have the task of increasing the fiber, fine and filler retention on the paper machine screen. At the same time they should cause a drainage acceleration on the wire and in the downstream wet presses and dryer sections and contribute to a sewage treatment. The main effects of the procedural aids, namely retention and drainage, are thus a prerequisite for high production rates by fast and trouble-free operation of the paper machines or for energy savings, especially in the dryer sections, and for a good material economy by largely retaining all solids on the screen. Improved retention means reduced wastewater load at the same time.

Polyethyleneimine, polyamines, polyamidoamines and cationic or anionic polyacrylamides are used as Entwässorungsbeschleuniger and retention agents (see Ulimann, Enzyklopädie der technischen Chemie, 4th Edition, Verlag Chemie, Volume 17, page 584. Pulp, paper, 5th edition, specialist book publisher Leipzig , Pp. 231, 235-237). Polyethyleneimine has by far the largest application as a dehydration accelerator (Pulp, paper p. 236).

In addition, other synthetic polymers have been tested as drainage accelerators and retention aids, but have not found any technical application. These include linear poly (dimethylallyl-ammonium chloride) (poly-DMDAAC). This polymer provides less drainage compared to the polyethyleneimine, so that at technically relevant small amounts used no increase in production can be achieved in comparison to the additive-free driving style (Pulp and Paper 31 (1982, 19-23).

Effective retention aids and drainage accelerators have a linear structure, branching in the molecule have a detrimental effect. The active chemical groups in cationic products are consistently amide or weakly basic amino groups, but not strongly basic quaternary ammonium groups (F. Müller, U. Beck, Das Papier 33 [1979] IOA, V 89-95). Polymers composed exclusively of structural units with quaternary ammonium groups therefore find no practical use.

Retention agents and drainage accelerators are said to cause micro-flocculation, because only in this way can the desired production increase be brought about in all process stages. In the formation of macro-curls no positive effects can be achieved, especially in the press and dryer sections. Macroflocs are formed the sooner, the higher the molecular weight of the auxiliary used.

To show z. B. high molecular weight cationic polyacrylamides «ine pronounced tendency to form macro flocs with the mentioned technological disadvantages.

(F. Müüer, U. Beck, The Paper 33 [1979] 10A, V 89-95, W. Günder, H. Melzer, The Paper 33 (1979) 10A, V 95-100, W. Auhorn, Wochenblatt Papierfabrikation [ 1982] 5, pp. 155-162).

When using a single polymer, the optima of solids retention, drainage rate, and sewage treatment are more frequent; not together, but lying down, at different times after the addition or at different Zugjbemengen (The paper 33 [1973] 10A, V 89-95). For this reason, mixtures of various polymers, for example polyethyleneimine and polyethylene oxide, have also been tested (Das Papier 29 [1975] V32).

However, the known process engineering tools hai η have the disadvantage that the drainage rate with good retention and sewage treatment is not sufficient to a sufficient increase in production and services

To achieve material economy. It is often limited to the first part of the wire section and is not effective in the subsequent technological sections. The use of mixtures of polymers has the further disadvantage that these mixtures are not universally applicable and that additional high demands must be placed on the technological regime with regard to the exactly coordinated dosage.

Object of the invention

The aim of the invention is a method in which an increase in production capacity in papermaking is achieved by the use of process engineering aids with high material economy, at the same time a good wastewater treatment is achieved.

Explanation of the essence of the invention

The object of the invention is to develop a method for increasing the space-time yield in papermaking by increased dewatering rate with good overall retention of the solids by adding a suitable water-soluble organic polymer.

According to the invention, this object is achieved, indan in papermaking as dewatering accelerator and retention agent, a water-soluble, highly branched, high molecular weight copolymer of dimethyl diallyl ammonium chloride (DMDAAC) and 0.1 to 3.0 mol% of a crosslinking comonomer having a molecular weight of 80,000 in quantities from 0.01 to 0.5%, based on the solids content of the suspension of fiber raw materials and additives, is added as an aqueous solution. Suitable crosslinking comonomers for the preparation of the highly-branched poly-DMDAAC are, for. As amine or ammonium salts with more than two allyl groups, u. a. Methyl trialiyl ammonium chloride (MTAAC), tetraallyl ammonium chloride (TAAC), N, N, N ', N'-tetraai: ylethylenediamine hydrochloride (TAEDC) and / or triallyl-amine hydrochloride (TAC) and methylenebisacrylamide (MBA). The highly branched poly-DMDAAC is prepared by copolymerization of DMDAAC with the crosslinking comonomer in aqueous solution with metered addition of the crosslinker, the addition being carried out during the progressive homopolymerization or copolymerization of the DMDAAC after conversions of between 25 and 90%.

The improved process for papermaking is carried out so that the desired amount of polymer is metered batchwise or continuously in conventional technical devices in a known manner before or during the Blattbildi .ng. It can be applied to all known processes for the production of paper or paperboard, which lead to different types of paper or paperboard and using different fiber raw materials and aggregates. The solids content of the suspension flowing onto the sieve, e.g. between 0.1 and 1.5%. Surprisingly, it was found that when using the highly branched poly-DMDAAC eino significant increase in the dewatering rate occurs. This accelerated drainage takes place both on the screen and in the press and dryer sections. At the same time very good results are achieved in retention and wastewater treatment. With consistently good retention against the fillers, the highly branched poly-DMDAAC is characterized by a significantly higher activity compared to the fibrous materials.

embodiments

To demonstrate the dewatering acceleration and the retention of the suspension to be treated in each case the following polymers were added in the specified amount, wherein the additional amounts refer to the solids content of the suspension.

Table 1

polymer

abbreviation

Quantity in%

Polyethyleneimine Example Same as Poly-DMDAAC (Homopolymer) Blend Example Copolymer of DMDAAC and 0.1 mole% of ViTAAC copolymer of DMDAAC and 0.5 mole of MDAAC copolymer of DMDAAC and 1.5 mole% of MTAAC copolymer of DMDAAC and 1.5 mol% MTAAC copolymer of DMDAAC and 1.5 mol% MTAAC copolymer of DMDAAC and 1.5 mol% MTAAC copolymer of DMDMC and 1.5 mol% MTAAC copolymer of DMDAAC and 3.0 mol% MTAAC copolymer of DMDAAC and 1.5 mole% TAAC copolymer of DMDAAC and 1.5 mole% TAEDC copolymer of DMDAAC and 1.5 mole% TAC copolymer of DMDAAC and 1.5 mole% MBA

0.02

0.02

0.02

0.02

0.02

0.01

0.04

0.08

0.5

0.02

0.02

0.02

0.02

0.02

example 1

On a wire screen paper machine (working width 65 cm), the influence of the substances according to Table 1 on the dewatering and drying was investigated. For this purpose, the substances according to Table 1 were each added continuously to a 0.8% suspension of shredded waste paper and other paper waste without further additives. The dewatering in the register section of the paper machine was measured by collecting 250 times of the waste water and measuring the necessary time and dewatering in the suction section by measuring the vacuum and the dry content at the end of the dryer section.

Table 2 shows the corresponding values.

Table 2 polymer drainage time Vacuum suction section Endtrockenge attempt Register game see. ' Decrease in% stop% No. - 6.5 0 93.1 1 A 5.4 20 95.1 2 B 5.7 5 95.2 3 C 5.1 23 97.5 4 D 4.6 28 98.0 5 e 4.4 30 98.5 6 F 5.4 21 97.6 7 G 4.1 34 98.8 8th H 4.0 35 98.9 9 J 3.8 32 98.9 10 K 4.4 30 98.5 11 L 4.3 30 98.5 12 M 4.5 28 98.6 13 N 4.4 30 98.4 14 O 4.4 30 98.4 15

Example 2

Permeability measurements were used to measure the specific surface area of a suspension of wood pulp in water and its change by addition of water-soluble organic polymers according to Table 1. Dtose method is a measure of the drainage rate. The smaller the specific surface area O, the higher the dewatering rate. In this case, the nonwoven fabric obtained from 1% suspension was compacted to dry contents of 20%, so that O, describes the rate of dewatering on the wire and in the press and dryer sections. The results are summarized in Table 3.

Table 3

Experiment No. polymer additive O.mVg 1 - 5.93 2 A 3.77 3 B 4.14 4 C 3.60 5 D 3.56 6 e 3.45 7 F 3.90 8th G 3.31 9 H 3.19 10 J 3.10 11 K 3.40 12 L 3.42 13 M 3.51 14 N 3.47 15 O 3.47

Example 3

In a laboratory pressure sheet former filled paper sheets were formed from a suspension of groundwood and kaolin having a solids content of 0.8% and the influence of added water-soluble polymers on the ash content (based on the dry weight of the paper) and the turbidity of the separated water was examined. Increasing ash content means increasing retention of the filler. Decreasing turbidity corresponds to increasing purity of the separated water.

The results are summarized in Table 4.

polymer Amount % Ash content% Turbidity scale parts 1 - - 13.1 86.5 2 A 0.02 15.5 78.0 3 A 0.04 16.1 69.0 4 B 0.02 15.4 75.5 5 B 0.04 15.9 68.0 6 D 0.02 15.5 77.0 7 D 0.04 15.9 70.0 8th G 0.02 15.7 75.0 9 G 0.04 16.1 68.0

Claims (2)

Anspruch [en] A process for solids retention and dewatering acceleration in papermaking, wherein the paper-forming suspension consists of fiber raw materials and aggregates having solids contents of 0.1 to 1.5%, by addition of 0.01 to 0.5% water-soluble organic polymers, based on the Solids content of the suspension, characterized in that the suspension is a highly branched, molecular copolymer having a molecular weight of 80,000 of dimethyldiallylammonium chloride and 0.1 to 3.0 mol% of a water-soluble crosslinking comonomer from the group of amine or ammonium salts with more than two Allylgrupoen was added, wherein the copolymerization was carried out in aqueous solution with dosing of Vernetzars during the progressive polymerization of DMDAAC after conversions between 25 and 90%. 2. The method according to claim 1, characterized in that are used as crosslinking comonomers M et hy I-triallyl-ammonium chloride, tetraallyl-ammonium chloride, triallyl-amine hydrochloride, Ν, Ν, Ν ', Ν'-Tefraallyl-ethylenediamine hydrochloride or methylenebisacrylamide.