FI100117B - A method for attaching contaminants in papermaking - Google Patents

Abstract

The invention relates to a process for fixing foreign substances in papermaking, wherein the agents used for fixing the foreign substances are polymers, consisting of cationic groups, of 50 to 100% by weight of quaternised dimethylaminopropylacrylamide or dimethylaminopropylmethacrylamide and 0 to 50% by weight of acrylamide, acrylic acid, methacrylic acid or acrylamidomethylpropanesulphonic acid, which have an intrinsic viscosity of less than 150 ml/g. The fixing agent is added to the pulp run and/or to the circulating water in quantities of up to 1% by weight relative to the dry weight of the paper produced.

Description

100117

A method for attaching contaminants in papermaking

The invention relates to a method for attaching contaminants in papermaking.

In recent decades, the paper industry has succeeded in drastically reducing its inherent use of fresh water and its inherent amount of wastewater by restricting and closing the water cycle in papermaking. The reasons for restricting the circulation of water are, on the one hand, the avoidance of losses of substances with the effluent and, on the other hand, the regulations of the authorities on the composition and quantity of the effluent according to the Waste Water Discharge Tax Act.

15 A number of new problems have arisen as a result of this limitation of water volumes. Due to the increased proportion of circulating water, the temperature of the pulp system rises considerably in part. This may result in increased mucus formation. Higher electrolyte concentrations in the process water lead to faster corrosion.

Odor problems can arise due to anaerobic zones in the water cycle.

However, the most significant problem in restricting the circulation of water is the enrichment of organic substances, the so-called pollutants, in the circulation. According to Auhorn, "Wochenblatt fur Papierfabrikation 112, 37-48 (1984)" interfering substances are dissolved or colloidally dissolved anionic oligomers or polymers and non- (ionic) hydrocolloids. They are produced during the manufacture of «*. 30 and in the treatment of cellulose, wood chips and waste paper *; ·· 'as lignans or poly (· * ... * or oligosaccharides derived from hemicellulose). Other interfering substances have their origin in the anionic auxiliaries used in papermaking.

100117 2 The concentration of these water-soluble substances increases sharply as the water circulation restriction is increased. The load of these interfering substances in the circulating water of the paper machine is particularly high in the production of wood chips containing pa-5.

Interfering substances interfere with papermaking in many ways. They affect the grinding of the pulp due to less swelling and slower grinding of the fibers, causing increased deposits in the circulating system and in the part of the paper machine where the pulp is fed to the wire.

In addition, deterioration in retention, dewatering, sheeting, as well as paper strength must be considered. Interfering agents affect the effectiveness of virtually all chemical excipients. These include retention and dewatering aids, wet and dry strength agents, adhesives, defoamers, bleaching chemicals and dyes. The concentration of interfering substances can become a limiting factor in reducing the circulation of water.

With the usual addition of aluminum sulphate used in the past, these problems could be largely overcome. The strong absorption capacity of the intermediate Al complexes results in a reduction of the circulating water load caused by the inorganic and organic substances in the ballast. The neutral way of working commonly used today therefore means that the problem is that aluminum sulphate cannot be used for precipitation and fixing. material. This is also apparent from the fact that, due to economic and qualitative choices, an increasing amount of calcium carbonate is used as a coating and filler pigment.

However, due to the increased use of calcium carbonate, manufacturing problems have also been significantly increased when treating calcium carbonate-containing coatings and waste paper in the acidic pH range. There was also the problem of removing interfering substances from the circulating water of the paper mill by minimizing the aluminum sulphate otherwise normally used.

5 The first attempts to solve this problem are already known. Thus, according to Arheilger and von Medvey, "Wochenblatt fiir Papierfabrikation 114, 958-961 (1986)" is a coated paper rich in wood chips using calcium carbonate without the addition of alum. This was accomplished by adding polydiallyldimethylammonium chloride (PolyDadmac) to the circulating water. However, Poly-Dadmac does not appear to have all the positive properties of alum. At that time, e.g. unusual difficulties in air control, which were avoided only by the addition of 15 other substances.

In addition, in contrast to alum, PolyDadmac also attached chromophoric substances so well that the addition of the fixing agent caused a deterioration in whiteness of about 1.5 whiteness points in use, which resulted in a significant increase in bleach cost.

Thus, there remains a problem in finding aluminum sulphate substitutes for the elimination of interfering substances, the use of which has no negative side effects.

DE-OS 3 620 065 deals with another; In this way: it uses special dewatering, retention and flocculants, namely high molecular weight, water-soluble polymers of N-vinylimides which act only in the presence of contaminants which contain ·. 30 derived from substances contained in wood

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* ··· 'oligomers containing phenolic groups and / or * ...' polymers. These particular N-vinylamide polymers are then insensitive in the production of paper to contaminants always present in limited or closed water cycles.

100117 4

The disadvantage of this method is that no adhesion of the contaminants takes place, and in particular it is also not possible to use other known cationic polymer-based flocculation, dewatering and retention agents used in the paper industry.

It is therefore an object of the invention to fix the contaminants in a simple and effective manner without having to resort to aluminum sulphate, and reliable excipients based on cationic polymers can still be used as dewatering aids, retention aids and flocculants without interfering with their effect.

According to the invention, this object is achieved by the use of polymers (homo- and / or copolymers) based on quaternized dimethylaminopropyl (meth) acrylic-15-amide, which are added to the headbox and / or circulating water of a paper machine, the intrinsic viscosity of these polymers being less than 150 ml / g. in a% by weight sodium chloride solution.

The polymers used according to the invention preferably comprise from 50 to 100% by weight of quaternized dimethylaminopropyl (meth) acrylamide and from 0 to 50% by weight of acrylamide, acrylic acid, methacrylic acid, acrylamidomethylpropanesulfonic acid or monomers of said cationic and anionic acids.

A: Dimethylaminopropyl (meth) acrylamide is quaternized using common known quaternizing agents, e.g. dimethyl sulfate, dimethyl carbonate, benzyl chloride, methyl chloride or ethyl bromide.

*. The polymers are used in an amount ranging from • 0.05 to 1% by weight, based on the dry weight of the paper produced, in addition to the usual excipients with which they are added to the headbox and / or circulating water.

The polymer 35 used as a fixing agent according to the invention is preferably added in an amount of 0.2 to 0.8% by weight, based on the dry weight of the paper produced.

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The total amount of polymer added to attach the contaminants can be advantageously divided into different addition sites.

The polymers used according to the invention surprisingly achieve that 5 a) the contaminants contained in the process water adhere to the paper fibers, and b) the degree of whiteness of the paper thus prepared still does not deteriorate due to the adhering contaminants.

The adhesive polymers used according to the invention are preferably used in a neutral manner without the addition of aluminum sulphate. However, it is also entirely possible to add these products together with aluminum sulphate according to a pseudoneutral method.

The polymers used according to the invention are particularly advantageous in papermaking processes in which the water circulation is more than 90% closed.

The invention is further illustrated by the following examples.

Parts always mean parts by weight unless otherwise defined below.

A. Manufacture of polymers

Polymer 1,250 parts of acrylamidopropyltrimethylammonium chloride are dissolved in 750 parts of water. The pH of the solution is adjusted to 5.0. The solution is heated to 75 ° C by passing sa- V; Rack nitrogen gas into the reaction vessel. The polymerization begins after the addition of 0.6 parts of potassium peroxide sulfate.

: A final temperature of 90 ° C is reached within 5 minutes. The viscosity of the product is i ;;; after 1,050 mPa * s, the intrinsic viscosity is 120 ml / g.

* Polymer 2 180 parts of acrylamidopropyltrimethylammonium chloride and 180 parts of acrylamidomethylpropanesulfonic acid 35 are successively dissolved in 568 parts of water. The pH is adjusted to 5.0 by adding 75 parts of 45% sodium hydroxide solution.

100117 6

The solution is heated to 75 ° C while nitrogen gas is introduced into the reaction vessel. Polymerization begins after the addition of 0.6 parts of potassium peroxydisulfate to the solution. After 10 minutes, a final temperature of 92 ° C has been reached. The viscosity of the product after cooling is 860 mPa.s, the intrinsic viscosity is 75 ml / g.

Polymer 3,200 parts of acrylamidopropyltrimethylammonium chloride are dissolved in 709 parts of water. After adding 50 parts of acrylic acid to the solution, the pH is adjusted to 5.0 by adding 41 parts of 45% sodium hydroxide solution. While nitrogen gas is introduced into the reaction vessel, the mixture is heated to 75 ° C. Polymerization begins after the addition of 0.4 parts of potassium peroxide sulfate. After seven minutes, a final temperature of 94 ° C has been reached. The viscosity of the product after cooling is 750 mPa * s, the intrinsic viscosity is 98 ml / g.

Polymer 4,210 parts of methacrylamidopropyltrimethylammonium-20 chloride are dissolved in 638 parts of water. After 90 parts of methacrylic acid have been added to the solution, the pH is adjusted to 5.0 by adding 62 parts of 45% sodium hydroxide solution. While nitrogen gas is introduced into the reaction vessel, the mixture is heated to 75 ° C. Polymerization begins after the addition of 0.8 parts of potassium peroxide sulphate. After 15 minutes, a final temperature of 91 ° C has been reached. The viscosity of the product after cooling is • · J 890 mPa -s, the intrinsic viscosity is 105 ml / g.

: * ·: Polymer 5 «30 210 parts of methacrylamidopropyltrimethylammonium chloride and 30 parts of acrylamidomethylpropanesulfonic acid are dissolved successively in 646 parts of water. After adding 60 parts of acrylic acid to the solution, the pH is adjusted to 5.0 by adding 54 parts of 45% sodium hydroxide solution. Polymerization of Po-35 begins after the addition of 0.8 parts of potassium peroxide sulfate. After 12 minutes, a final temperature of 94 ° C has been reached. The viscosity of the product after cooling is 740 mPa.s, the intrinsic viscosity is 88 ml / g.

Polydimethyldiallylammonium chloride with an intrinsic viscosity of 95 ml / g was used as a reference polymer in the in-use studies.

B. Operational studies

To demonstrate the attachment of contaminants, the following methods are conventional: 1. Anionic contaminants attenuate the effect of cationic dewatering and retention agents. After the addition of the fixing agents, the dewatering and retention effect is improved and the potency is quantified.

15 2. The degree of whiteness obtained on paper is measured in DIN

According to 53145. Due to the attachment of certain contaminants and chromophores to the paper fibers, the whiteness of the paper deteriorates.

The degree of whiteness is naturally at its highest without the fastener and deteriorates substantially less with the fasteners according to the invention than with the reference substances.

1. Drainage of water from the pulp, Schopper-Riegler method 25 The switchgear used is described in the book "Zellstoff

Papier, 5th edition, VEB Fachbuchverlag Leipzig, pp. 387 -388 "and was modified so that both outflow pipes are emptied together into a common collection vessel.

As a result, it is achieved that it is no longer possible to find out the degree of grinding, but only the removal of water from the mass.

• V · i · ·· ** Waste paper pulp with a solids concentration of 4% was used. Dilute 3 g of absolute dry mass with tap water of hardness 20 ° dH to a volume of 35 300 ml. The fixative is diluted to a volume of 300 ml of 100 ml and added to the pulp suspension. The suspension is poured three times from one container to another. The dewatering aid is then diluted to a volume of 400 ml and added to the suspension. This system is then poured from one vessel to another once and the water is removed from it in a Schopper-Riegler apparatus.

Determine the time during which 700 ml of filtrate has soaked. When determining the blind value, dewatering without fixative and dewatering aid is performed, when determining the O-value without fixing agent, but with dewatering aid included. 25% cationic polyacrylamide is used as a dewatering aid.

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Drainage tests Schopper-Riegler switchgear (time in seconds to remove a 700 ml batch of filtrate) 5

Dewatering aid (%) 0.00 0.01 0.02 0.03

Blind value: 255

Zero value: 121 83 67 10 __

Strain relief 1: 0.3% 89 71 59 "1: 0.6% 78 65 54

Fastener 2: 0.3% 96 76 63 15 "2: 0.6% 86 69 57

Fastener 3: 0.3% 93 74 62 "3: 0.6% 82 64 57 20 Fastener 4: 0.3% 92 71 61" 4: 0.6% 82 65 55

Fixative 5: 0.3% 94 74 63 "5: 0.6% 83 66 56 25

Benchmark: 0.3% 115 81 65 • V; ": 0.6% 105 76 61 •« • · «1 · ·» · «• ♦ · *, 30 2. Determination of retention (Britt-Jar test)

The instrumentation used to determine retention is pre - ***: "in the article" New methods for monitoring retention ", 'Pin, February 1976, vol. 59, No. 2, KW. Britt and J.E.

. Unbehend. 2.5 g of absolute dry mass (90% wood pulp and SR value 48 °, 10% chalk, 71% slurry, 100117 10 where 60% of the chalk particles are smaller than 2 μm) is diluted with tap water of hardness is 20 ° dH, to a volume of 400 ml. After the addition of the fixative, the suspension is poured 10 times from one vessel to another. The retention aid is then added as a 0.01% solution and the suspension is poured three times from one vessel to another. After diluting the suspension with water to a volume of 500 ml, it is added to the Britt-Jar test apparatus and stirred for 15 seconds at 800 rpm. While further stirring the slurry, the outlet valve is then opened for 30 seconds and the filtrate is collected. After the filtrate has been filtered through a suction filter using a black belt filter, the non-retained fines are determined by drying. Retention is expressed as the percentage of non-retained fines in the total fines.

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El 100117 11

Britt-Jar test (percentage retention)

Dewatering aid (%) 0.00 0.02 0.03 5 ..... 1 —— - -

Blind value: 48.9

Zero value: 57.1 61.6

Fixative 1: 0; 3% 66.5 71.3 10 '' 1: 0.6% 69.8 75.4

Fixative 2: 0.3% 64.6 70.8 "2: 0.6% 68.4 75.1 2 ^ Fixative 3: 0.3% 64.3 70.1" 3: 0.6% 68, 9 74.3

Fastener 4: 0.3% 65.2 69.9 "4: 0.6% 69.2 74.8 2 0 ~ Fastener 5: 0.3% 64.8 69.3" 5: 0.6% 68 , 2 73.9

Benchmark: 0.3% 58.3 62.7: 0.6% 63.9 67.3 2 5 ---- ♦ · · • · · • · 3. Determining the degree of whiteness: ·. a) Sheeting ♦ - ·.-f. The waste paper pulp with a solids content of 4% <30% and an amount of 2.5 g absolutely dry is diluted with tap water to a volume of 500 ml. The fixing agent, • · ·! ...: in an amount of 0.4%, calculated on the absolutely dry mass, is added as a 0.5% solution and the slurry is stirred for 30 seconds with a magnetic stirrer at 35 rpm at 500 rpm. 100117 12 dewatering aids, 25% cationic polyacrylamide, are then added in an amount of 0.03% as a 0.01% solution and the slurry is stirred for a further 30 seconds. Add 4 liters of tap water to the sheet machine and make it bubble 5 by blowing air. The pulp suspension is then added and, after stirring, the water is sucked off.

The cover board is placed on top of the formed sheet and the sheet is removed from the wire. The sheet is then dried for 10 minutes in a vacuum drier, followed by five minutes in an oven at 110 ° C. A value of zero is obtained without the use of a fixing agent.

b) Measurement of whiteness According to DIN 53145, the degree of whiteness of the produced sheets is determined. Measurements were performed under the trade name

On a Zeiss Elrepho using a filter No. 7, calibrated for MgO.

Measurement of whiteness

Whiteness (%) 20 Zero value 65.9

Fastener 1 62.8

Fastener 2 63.2

Fastener 3 62.7

Fastener 5 61.3 25 Fastener 5 61.9

Benchmark 57.3 • · i · · «

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Claims (8)

100117 A process for the fixing of contaminants in papermaking by the addition of fixing agents, characterized in that polymers comprising a) 50 to 100% by weight of quaternized dimethylaminopropylacrylamide or dimethylaminopropylmethacrylamide and 10 b) 0 to 50% by weight are used as fixing agent. acrylamide, acrylic acid, methacrylic acid, acrylamidomethylpropanesulfonic acid or mixtures of these monomers, wherein the intrinsic viscosity of these polymers is less than 150 ml / g. Process according to Claim 1, characterized in that the polymers are used in an amount of 0.05 to 1, preferably 0.2 to 0.8% by weight, based on the dry weight of the paper produced. Process according to Claim 1 or 2, characterized in that the quaternized dimethylaminopropyl (meth) acrylamide is quaternized with dimethyl sulphate, methyl chloride, ethyl bromide, dimethyl carbonate or benzyl chloride. A method according to claim 1, characterized in that the total amount of polymer added is divided into different addition points. Process according to Claim 1, characterized in that the polymers are used in combination with customary cationic papermaking aids. • »· Process according to Claim 1, characterized in that the polymers are used without the addition of aluminum sulphate. Process according to Claim 1, characterized in that the polymers are used in combination with aluminum sulphate. 100117 Process according to Claim 1, characterized in that the polymers are used in papermaking processes in which the water circulation is more than 90% closed. • ·· • · · • · · • »♦ • · <• <« • «· Γ”: • · · li is 100117