ES2845552T3 - Inhibition of sedimentation in the manufacture of cellulose according to the sulfate process (Kraft digestion) - Google Patents

Abstract

Use of comb polymers, obtainable by radical polymerization of monomers with a monoethylenic unsaturation of a group A1) of acids with a monoethylenic unsaturation and their salts and of group A2) of polyethers with a monoethylenic unsaturation as sedimentation inhibitors in manufacture of cellulose according to the sulfate procedure (Kraft digestion).

Description

DESCRIPTION

Inhibition of sedimentation in the manufacture of cellulose according to the sulfate process (Kraft digestion)

The present invention relates to the use of comb polymers as deposition inhibitors in the manufacture of cellulose, according to the sulfate process (Kraft digestion).

The most important and most frequently applied process for the manufacture of cellulose is the sulfate or Kraft process. In 1884, C. F. Dahl registered a procedure using sodium sulfide or sodium sulfate to obtain the patent. The cellulose sulfate developed in this regard is preferred due to its high strength, in particular for papers that receive strong mechanical loads, "Kraft papers", and is therefore also referred to as Kraft cellulose.

The basis of the procedure is the partial solubility of lignin in hot solutions. The alkaline procedure uses cooking liquors, which contain sodium hydroxide, sodium sulfide, sodium sulfate, and sodium carbonate. The wood chips are treated in pressure vessels for three to six hours at elevated pressure (0.7 to 1.0 MPa) and a temperature of 140 to 170 ° C.

Sodium sulfide increases delignification, on the one hand, the lignin is cleaved by a nucleophilic attack of the sulfide anion and passes to the so-called black liquor (lignin soluble in alkali), and on the other hand the lengths of the fiber are increased. In addition to lignin, carbohydrates are also degraded in the strongly alkaline region. Polysulfide-containing bleaches stabilize the polioses. Kraft pulp paper is tear resistant, tear resistant and tensile resistant. Advantages of the sulfate process are a good impregnation of the wood chips in the alkaline solution, and thus shorter cooking times. Virtually all woods can be used. Sulfate celluloses still contain large amounts of polioses and are darker than sulfite celluloses. They do not exhibit a sufficiently high content of α-celluloses for the manufacture of cellulose derivatives. The lignin-bearing waste liquors arising from the sulfate process are concentrated and incinerated, so that the energy requirement of the entire process can be covered. As valuable by-products are turpentine essence and approximately 30 to 35 kg of tallow oil per 1,000 kg of cellulose.

During the firing process calcium ions dissolve from the wood. These react with the sodium carbonate present in the cooking liquor, until giving the hardly soluble calcium carbonate. The calcium carbonate that forms is deposited inside the bleach, in pipes, heat exchangers, etc. As a result, the flow through the bleach, the effective amount of bleach as well as the heat transfer are reduced. Finally, the installation has to be switched off and cleaned, already after a short time. To extend these cleaning intervals, calcium carbonate deposition inhibitors are added to the cooking process.

These deposition inhibitors are described in a multiplicity of patents and publications. Documents WO 02/098802 A1 and WO 02/98803 A1 from the company Solutia Inc give a good overview on phosphonic acid-based calcium carbonate deposition inhibitors.

Apart from that, a multiplicity of acrylate-based polymer patents were also published. Thus, JPH 1025684 (A) describes a terpolymer based on maleic acid, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) with a molecular weight of 500 to 20,000 g / mol.

Document US 5,409,571 A discloses a copolymer based on maleic acid and acrylic acid, which was polymerized with the addition of hypophosphite. The molecular weight is 500 to 10,000 g / mol.

The use of polyitaconic acid in mixture with phosphonic acids is known from JP 2011-052358 (A). For "scale inhibitor 1" polyitaconic acid and 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) are mixed.

From JP 2014-147911 (A) a mixture of two polyitaconic acid polymers with different molecular weights is known. Polymer A has a molecular weight of 500 to 15,000 g / mol and Polymer B has a molecular weight of 15,000 to 40,000 g / mol.

Document WO 00/12436 A claims a copolymer of 1,2-dihydroxy-3-butene, and another comonomer from the group of maleic acid, acrylic acid, acrylamide, methacrylic acid, itaconic acid, vinyl sulfonic acid, styrene sulfonic acid, N-tert .-butylacrylamide, butoxymethylacrylamide, N, N-dimethylacrylamide, 2-acrylamido-2-methylpropanesulfonic acid and salts thereof.

The cited disclosures are dedicated exclusively to the inhibition of inorganic calcium carbonate deposition.

If resin-rich hardwoods, such as birch, are used for the manufacture of cellulose according to the sulfate process, other problems arise. The resin present leads to sticky deposits, called "tar" or "sticky", which during the manufacturing process can lead to an elevation of bleaching chemicals or paper machine problems. To remove these adherent substances from the process, resin dispersing agents are added already during the firing process.

Document WO 2010/019425 A1 gives a good overview in the cited state of the art, on which substances can be used as resin dispersing agents.

The registration itself claims a mixture of triglyceride oil or triglyceride alkyl esters with surfactants based on polyalkylene glycol and / or resin, resin soaps, tallow oil, tallow oil soaps and derivatives thereof.

WO 2008/057492 A2 describes a copolymer of vinyl alcohol and vinyl acetate as well as hydrophobically modified hydroxyethyl cellulose, as adhesion suppressant. In addition, enzymes that catalyze the hydrolysis of resin are mentioned.

Document WO 2004/057101 A1 discloses a mixture of fatty acids and resin acids, as an effective dispersing agent against substances that can be extracted.

The cited disclosures are exclusively concerned with the inhibition of organic resin deposition.

It is known from practice that by using, for example, tallow oil, the resin problem in the cooking process is clearly improved in particular, although the tendency to inorganic depositions is thereby significantly increased. The trend increases with the concentration of calcium present in the cooking liquor. The higher the calcium concentration, the greater the tendency for calcium carbonate deposits to occur. Furthermore, a second negative effect occurs due to the addition of tallow oil. The action of even effective deposition inhibitors is reduced by the added sebum oil. An increase in the dosage amounts is no longer sufficient in itself in these cases. Massive deposition occurs in the bleach, pipes, and heat exchanger.

A work is known from the state of the art, which has done its task in relation to the negative effects of resin dispersing agents, on the tendency to deposition of calcium carbonate.

EP 2020422 A1 discloses emulsifying polymers and the use of these polymers for stable emulsification of hydrophobic additives in aqueous concrete liquefaction agents. The polymers are obtainable by copolymerizing at least one ethylenically unsaturated monomer, comprising ionic groups, with at least one ethylenically unsaturated monomer exhibiting hydrophilic oxyalkylene groups, and at least one ethylenically unsaturated monomer exhibiting vinylaromatics and therefore at least one hydrophobic monomer with ethylenic unsaturation.

From DE 10 2013 207778 A1 it is known the use of comb polymers in detergents and detergents, in particular for finishing textiles, and the corresponding agents. The comb polymers used are obtainable by A) a radical polymerization of monomers with an ethylenic unsaturation of a group A1) of acids with an ethylenic unsaturation and their salts and a group A2) of polyethers with an ethylenic unsaturation and / or a group A3) of acids with an ethylenic unsaturation, which were previously esterified with polyalkylene oxides hydrophobically terminal blocked on one side, or by B) a polymer analog reaction by esterification and / or amide formation of a group B1) of polycarboxylic acids and their salts with a group B2) of monohydroxypolyethers and / or a group B3) of monoamine compounds.

Therefore, the objective of the present invention is to effectively prevent the negative influence of CaCO ³ deposition inhibitors, by means of resin dispersing agents during the Kraft cooking process. According to the invention, polymers should be prepared which effectively inhibit CaCO ³ deposits during the cooking process, when working with the addition of resin dispersing agents based on organic carboxylic acids.

Surprisingly it was found that comb polymers with polyether side chains significantly reduce the tendency for calcium carbonate deposition during cellulose cooking according to the sulfate process. If a comb polymer is added to a cooking process, which is carried out with resin dispersing agent and a standard CaCO ³ deposition inhibitor, then a significant reduction in CaCO ³ deposition occurs.

The comb polymers used according to the invention can be obtained by radical polymerization of monomers with an ethylenic unsaturation of the group A1) of acids with an ethylenic unsaturation and their salts and of the group A2) of polyethers with an ethylenic unsaturation.

Therefore, the object of the invention is the use of comb polymers, obtainable by radical polymerization of monomers with ethylenic unsaturation.

of group A1) of acids with an ethylenic unsaturation or their salts

and from group A2) of polyethers with an ethylenic unsaturation

as deposition inhibitors in the manufacture of cellulose according to the sulfate process (Kraft digestion).

The effect or influence of calcium carbonate deposition inhibition is not mentioned in the state of the art. The effect or influence of the deposition inhibiting action, due to the addition of resin dispersing agents based on tallow oil, are also not addressed in the state of the art.

The preparation of the comb polymers used according to the invention by radical polymerization is known to those skilled in the art and can be carried out by following the European document EP 0537870 A. In this regard, reference is made in full in this publication.

Examples of the monomers of group A1, of the acids with an ethylenic unsaturation and their salts, are acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, vinyl sulfonic acid, allylsulfonic acid, methallylsulfonic acid, acid 2 -acrylamido-2-methyl-propanesulfonic, styrene sulfonic acid, vinyl phosphonic acid. The monomers of group A1 can be used individually or as a mixture of different monomers. Acrylic acid, methacrylic acid or maleic acid are preferably used in an amount of 5 to 95% by weight based on the polymer, in particular acrylic acid or maleic acid is used in an amount of 10 to 90% by weight based on the polymer.

Examples of the group A2 monomers are polyethers with ethylenically unsaturated polyethylene glycol monoallyl ether, polypropylene glycol monoallyl ether and polyethylene-polypropylene monoallyl ether; These are commercially available for example from the Clariant company under the Polyglykol® A product series, from the BASF company under the Pluriol® A ... R product series or from the NOF Corporation company under the Uniox® product series, Unisafe ® and Unilube®. Other examples are polyethylene glycol monovinylether (Clariant company product series: Polyglycol® R), isoprenylethoxylates (BASF company product series: Pluriol® A ... I) and vinylxybutylethoxylates (BASF company product series: Pluriol® A ... V).

Group A2 monomers can terminate in OH or have end group closure. The monomers can be used individually or as a mixture of different monomers. Preferably, polyalkylglycolmonoallyl ether is used in an amount of 2 to 25% by weight based on the polymer, in particular polyethyleneglycolmonoalylether and polyethylene-polypropylenemonoalylether are used in an amount of 5 to 20% by weight based on the polymer.

The use according to the invention can occur within the framework of cellulose production according to the sulfate process, in a continuous or batch process, so that the comb polymer is added separately to a cooking liquor, or it is incorporates the comb polymer as a component of the CaCO ³ deposition inhibitor or resin dispersing agent in the cooking liquor. Therefore, another object of the disclosure is a CaCO ³ deposition inhibitor, which contains a comb polymer according to the invention. In a preferred embodiment of the invention, a comb polymer according to the invention is used in a deposition inhibitor, wherein the deposition inhibitor for the manufacture of cellulose according to the sulfate process (Kraft digestion) comprises 0.1 to 30% by weight, in particular 0.5 to 25% by weight of comb polymers, obtainable by radical polymerization of monomers with an ethylenic unsaturation of

a group A1) of acids with an ethylenic unsaturation and their salts and

group A2) of polyethers with an ethylenic unsaturation.

The CaCO ³ deposition inhibitors and resin dispersing agents, which contain the comb polymer according to the invention to be used, may contain all the other usual components of such agents, which do not undesirably interact with them. .

In a preferred embodiment, such a CaCO ³ deposition inhibitor contains polymers such as mono-, co and terpolymers based on acids with an ethylenic unsaturation and their salts, such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, acid fumaric, itaconic acid, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, vinylphosphonic acid, acrylamide, N-tert-butylacrylamide, butoxymethylacrylamide and N, N-dimethylacrylamide and N, N-dimethylacrylamide.

Another object of the invention is the use of comb polymers, obtainable by radical polymerization of monomers with ethylenic unsaturation of a group A1) of acids with ethylenic unsaturation and their salts and of group A2) of polyethers with ethylenic unsaturation. , for washing cellulose according to the sulfate cooking process.

The following examples clarify the advantages of the comb polymers used

Examples of realization:

1. Preparation of comb polymers

Synthesis example (radical polymerization):

328 g of water, 61 g (0.06 mol) of polyalkylene glycol-1000-monoalylether ( Polyglycol A 31/1000, Clariant) as well as 5 g of butyldiglycol, as dissolution promoter. The following mixtures were placed separately: monomer solution: 365 g (5.07 mol) of acrylic acid in 65 g of water. Solution 1: 10 g of sodium persulfate in 80 g of water. Solution 2: 26 g of sodium hypophosphite x 1 H ² O in 60 g of water. The batch was heated to 90 ° C. At this temperature the solutions mentioned above were metered in by separate additions with a constant mass flow for 3 hours (monomer- and solution 2) and for 3.5 h (solution 1). After completion of the addition, it was allowed to react further for 1 hour at 90 ° C. A clear, colorless aqueous polymer solution was obtained with a solids content of 46% by weight.

The comb polymers listed in Table 1 were prepared in an analogous manner.

Table 1:

2. Application of comb polymers

Application example: (cooking of cellulose according to the sulfate process)

The relationships during cellulose cooking according to the sulfate procedure were simulated with the following laboratory procedure. In 200 ml Labomat beakers from the company Mathis AG, which are equipped with an addition unit (septum closure), 100 ml of a synthetic white liquor with the following composition were previously placed in each case:

30.0 g / l 100% sodium hydroxide

11.0 g / l sodium sulfide

7.5 g / l sodium carbonate

2.0 g / l sodium sulfate

The solution was prepared with demineralized water.

Variable amounts of deposition inhibitor and 100 mg of tallow oil (from a pulp mill) are added to the 100 ml of white liquor and the vessels are closed.

In the Labomat of the company Mathis AG, the contents of the beakers were heated to 140 ° C and kept at this temperature for 60 minutes. After 60 minutes, with a suitable syringe, 8 ml of a 0.25 mol / l CaCh solution were metered through the septum. This corresponded to a first approximation to a concentration of 800 mg / l of Ca2 + ions in the solution.

They were kept at 140 ° C for another 30 minutes. The contents of the beaker were then cooled to 80 ° C, the beaker was opened and the hot solution was filtered off through a black filter.

The evaluation occurred on the ease of filtration, the appearance of the filtrate and the appearance of the deposits on the filter.

Evaluation criteria:

a) Filtration rate

■ fast <20 sec

■ Slow 20 - 30 sec

■ Very slow> 30 sec

b) Appearance of the filtrate

■ clear

■ cloudy

■ strongly cloudy

c) appearance of the deposition on the filter

■ 1 = Black filter without stool

■ 2 = Black filter with few stools

■ 3 = Crystalline deposits, comparable to the white value

■ 4 = Crystalline deposits, few compared to white value

■ 5 = Crystalline and amorphous deposits

■ 6 = Amorphous stools

A slow filtration rate (> 30 sec), a cloudy filtrate as well as amorphous depositions on the filtrate were estimated as a good deposition inhibiting effect.

3. Results of the application technical test

Standard polymer = acrylic acid / maleic acid copolymer, which is used in practice as a deposition inhibitor in the cooking of cellulose according to the sulfate process.

Discussion of the results:

The tests of numbers 1 to 4 show results without the addition of tallow oil.

Test No. 1 clearly shows which massive crystalline depositions can arise under the conditions of a cellulose cook, when no deposition inhibitor is used. Due to the coarse crystalline structure, a complete and rapid separation by filtration of the depositions occurs, the filtrate is clear. In tests Nr. 2 to Nr. 4 different concentrations of deposition inhibitors were added. For the use amounts of 20 and 30 mg (tests Nos. 2 and 3) the influence on the test parameters is only non-essential. In addition, mainly coarse crystalline structures arise, which lead to a rapid and complete separation by filtration. From a concentration of 40 mg the results change abruptly. The crystal structure changes from coarse crystalline to fine amorphous. The pores of the filter material are quickly clogged and a significant reduction in filtration speed occurs. From the experiences there, the crystal modification mechanism is necessary, in order to effectively prevent CaCO3 deposition during cellulose cooking in practice.

Test No. 5 shows the impact of tallow oil on the stools that arise. Compared to test No. 1, the deposition on the filter has clearly increased. Test No. 6 now discloses the total problem known from practice, that standard polymers fail due to the use of tallow oil and are no longer sufficiently effective. If the standard polymer in test Nr. 4 could still effectively modify the depositions that arise, it fails completely in test Nr. 6. An increase in the amount of use (test Nr. 7 and 8) improves even the situation slightly, without However, it is far from a sufficient effect.

The tests Nos. 9 to 12 show the outstanding effect of the comb polymers used according to the invention. In all tests, fine amorphous deposits, none crystalline, are shown on the filter paper. The filtration rate has been increased significantly and the depositions could be dispersed even so finely divided that cloudiness occurs in the filtrate. Another positive effect is the amount of polymer used. By using the comb polymers the amount of standard polymer usage could even be reduced.

Claims (8)

1. Use of comb polymers, obtainable by radical polymerization of monomers with monoethylenic unsaturation of a group A1) of acids with a monoethylenic unsaturation and their salts and from group A2) of polyethers with a monoethylenic unsaturation as sedimentation inhibitors in the manufacture of cellulose according to the sulfate process (Kraft digestion). 2. Use of the comb polymers according to claim 1 in a continuous or discontinuous process for cooking cellulose according to the sulfate process. 3. Use of the comb polymers according to claim 1 as a separate addition or as a component of a common CaCO ³ deposition inhibitor or of a resin dispersing agent, in the cooking liquor. Use according to one of Claims 1 to 3, in which the sedimentation inhibitor for the production of cellulose according to the sulfate process (Kraft digestion) comprises 0.1 to 30% by weight, in in particular from 0.5 to 25% by weight of comb polymers, obtainable by radical polymerization of monomers with monoethylenic unsaturation of a group A1) of acids with a monoethylenic unsaturation and their salts and from group A2) of polyethers with a monoethylenic unsaturation. Use according to claim 4, in which the sedimentation inhibitor is characterized in that the components are chosen from among polymers, such as mono-, co- and terpolymers based on acids with a monoethylenic unsaturation and their salts, such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, vinyl sulfonic acid, allylsulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, styrene sulfonic acid, vinyl phosphonic acid, acrylamide, N-tert-butylacrylamide , butoxymethylacrylamide and N, N-dimethylacrylamide. Use according to claims 4 or 5, in which the sedimentation inhibitor is characterized in that it also contains phosphonic acids, in particular HEDP, ATMP and / or DTPMP, phosphonopolycarboxylic acids, in particular PBTC, aminopolycarboxylic acids, in particular MGDA, GLDA, IDS and / or EDDS and / or hydroxycarboxylic acids, in particular gluconic acid and / or citric acid. Use according to one of Claims 4 to 6, in which the sedimentation inhibitor is characterized in that the components of the resin dispersing agent are chosen from non-ionogenic or anionic surfactants, tallow oil, oil soaps of tallow, fatty acids and their soaps, resin acids and their soaps, triglyceride oils and triglyceride alkyl esters. 8. Use of comb polymers, obtainable by radical polymerization of monomers with monoethylenic unsaturation of a group A1) of acids with a monoethylenic unsaturation and their salts and from group A2) of polyethers with a monoethylenic unsaturation for washing cellulose according to the sulfate cooking process.