EP4165243B1 - Procédé de contrôle de poix pendant le blanchiment - Google Patents

Procédé de contrôle de poix pendant le blanchiment

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Publication number
EP4165243B1
EP4165243B1 EP21734378.9A EP21734378A EP4165243B1 EP 4165243 B1 EP4165243 B1 EP 4165243B1 EP 21734378 A EP21734378 A EP 21734378A EP 4165243 B1 EP4165243 B1 EP 4165243B1
Authority
EP
European Patent Office
Prior art keywords
cationic
pitch
mol
pitch control
control agent
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Application number
EP21734378.9A
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German (de)
English (en)
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EP4165243C0 (fr
EP4165243A1 (fr
Inventor
Leif Robertsen
Jonas Konn
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Kemira Oyj
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Kemira Oyj
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Publication of EP4165243A1 publication Critical patent/EP4165243A1/fr
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Publication of EP4165243C0 publication Critical patent/EP4165243C0/fr
Publication of EP4165243B1 publication Critical patent/EP4165243B1/fr
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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/02—Agents for preventing deposition on the paper mill equipment, e.g. pitch or slime control
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/08—Removal of fats, resins, pitch or waxes; Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching
    • D21C9/086—Removal of fats, resins, pitch or waxes; Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching with organic compounds or compositions comprising organic compounds
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
    • D21C9/14—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
    • D21C9/142—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites with ClO2/Cl2 in a multistage process involving ClO2/Cl2 exclusively
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/02—Chemical or chemomechanical or chemothermomechanical pulp
    • D21H11/04—Kraft or sulfate pulp
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/20—Macromolecular organic compounds
    • D21H17/33—Synthetic macromolecular compounds
    • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H17/37—Polymers of unsaturated acids or derivatives thereof, e.g. polyacrylates
    • D21H17/375—Poly(meth)acrylamide
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/20—Macromolecular organic compounds
    • D21H17/33—Synthetic macromolecular compounds
    • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H17/41—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups
    • D21H17/44—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups cationic
    • D21H17/45—Nitrogen-containing groups
    • D21H17/455—Nitrogen-containing groups comprising tertiary amine or being at least partially quaternised

Definitions

  • the present invention relates to a method for pitch control and/or pitch removal during bleaching of cellulosic fibres in a pulp manufacturing process.
  • Cellulosic fibres obtained from a chemical pulping process are bleached in a bleaching process, where residual lignin is removed from the fibres in order to increase their brightness.
  • Bleaching is a stage-wise process, where various bleaching chemicals are usually used at different successive stages to break lignin into smaller structures. Breakdown structures of lignin are water soluble, especially at pH >7, and they are removed from the fibres, as well as from the bleaching process, in alkaline extraction stages located after or between the bleaching stages.
  • pitch and other pitch-like substances, resins and extractives present in pulp are also liberated from the fibres. It has been observed that if the pitch and pitch-like substances are not bound to a pitch control agent in the acidic bleaching stages, they easily form agglomerates, which can deposit on process equipment, block process filters and/or create spots in the final fibrous web.
  • the pitch and pitch-like substances are nowadays preferably effectively removed from the bleaching process at the alkaline extraction stage together with lignin.
  • Talc is commonly used as a pitch control agent to reduce tackiness of pitch and pitch-like substances. Talc is added to the bleaching process, where it interacts with the liberated pitch and pitch-like substances and reduces their tendency to form agglomerates.
  • pitch and pitch-like substances which are soluble at alkaline pH, such as fatty acids, are freed from talc and removed with process water together with lignin.
  • Talc itself remains in the pulp manufacturing process with the fibres.
  • Pitch and pitch-like substances which are not soluble in alkaline pH, such as sterols and betulinol, may also remain in the pulp manufacturing process, staying at least partly bound with talc particles during the alkaline extraction stage. These non-alkaline soluble neutral pitch and pitch-like substances may still cause deposit problems later in the pulp manufacturing process or degrade the quality of the obtained cellulose.
  • WO 2018/096211 discloses a use of a water-soluble polymer product comprising amphoteric polyacrylamide for controlling deposit formation caused by hydrophobic substances in manufacture of paper or board.
  • US 2018/363247 discloses an acrylamide-based polymer which contains one or more multiquaternized monomer units.
  • the acrylamide-based polymer can be used in papermaking process to reduce pitch and stickies deposition, improve retention and drainage and enhance dry strength properties of paper.
  • Us 2006/000570 discloses a metho and a composition for controlling pitch and stickies deposit in a pulp and papermaking process using amphoteric copolymers of diallyldimethylammonium chloride with acrylic acid and/or acrylamide.
  • the object of the present invention is to minimize or even eliminate the disadvantages existing in the prior art.
  • One object of the present invention is to provide a method for effectively controlling pitch and pitch-like substances during a bleaching of cellulosic fibres.
  • One object of the present invention is to provide an effective alternative for talc in the bleaching process of cellulosic fibres.
  • Yet another object of the present invention is to provide a method with which pitch and pitch-like substances are effectively removed from cellulosic fibre suspension during the bleaching process.
  • Typical use of cationic polymer comprising cationic functional groups which are hydrolysed at pH 9 or higher according to the present invention is as pitch control agent in bleaching process of cellulosic fibres for controlled removal of pitch and pitch-like substances.
  • talc can be replaced as a pitch control agent by a cationic polymer, which comprises cationic functional groups which are hydrolysed at pH 9 or higher.
  • Cationic groups of the polymer are able to interact with pitch and pitch-like substances at least as effectively as talc at acidic pH and then release pitch and pitch-like substances during the subsequent alkaline extraction stage, thus preventing the agglomeration of pitch and pitch like substances in the pulp manufacturing process.
  • the polymer comprises cationic groups that are hydrolysed during the alkaline extraction stage
  • the hydrolysed groups release the pitch and pitch-like substances to the aqueous phase in the alkaline extraction stage, whereby the pitch and pitch-like substance can be effectively removed with the aqueous phase from the pulp manufacturing process.
  • the polymer amounts needed for effective pitch removal are also much lower than the talc amounts needed for the same effect.
  • use of a cationic polymer as pitch control agent reduces the content of inorganic material in the obtained bleached pulp, which make the pulp more suitable for a variety of different purposes, such as manufacture of carboxymethyl cellulose.
  • the possibility to reduce or eliminate inorganic material, such as talc, in the obtained bleached pulp may reduce dusting problems in paper or board products for which the obtained bleached pulp is used.
  • Polymers which are suitable for use in the present invention, comprises cationic functional groups which are hydrolysed at pH 9 or higher, i.e. the polymer comprises cationic groups which are hydrolysed in a pH range from pH 9 to pH 14, preferably from pH 9 to pH 11.
  • the pitch control denotes actions which inhibit or at least minimize the formation of agglomerates, deposits and the like, as well as formation of defects, such as visual dark spots, in the final bleached pulp, which are caused by pitch and/or pith-like substances by removing them effectively during the alkaline extraction stage(s) of the bleaching.
  • the present invention provides thus a method for control and/or removal pitch and pitch-like substances during bleaching of cellulosic fibre suspension.
  • Pitch and pitch-like substances in the context of the present invention, comprise a mixture of various resins and extractives, such as fatty acids, resin acids, steryl esters, sterols, triglycerides, etc., which are liberated from hardwood and/or softwood fibres during bleaching process.
  • the present invention is effective for removal of fatty acids, resin acids, steryl esters, sterols and/or betulinol.
  • the present invention is especially effective for removal of neutral pitch and pitch-like substances, which are not soluble at alkaline extraction stage, such as steryl esters, sterols and/or betulinol.
  • the method according to the present invention is suitable for all cellulosic pulps which are bleached.
  • the cellulosic fibres to be bleached may originate from hardwood, softwood, or their mixtures.
  • the cellulosic fibres are hardwood fibres.
  • the cellulosic fibres may originate from birch, eucalyptus, acacia, other tropical hardwood species, or any mixtures thereof.
  • Cellulosic fibres are obtained from a pulping process and formed into an aqueous cellulosic fibre suspension.
  • cellulosic fibres originate from a chemical pulping process, such as Kraft or sulphite pulping, preferably Kraft pulping.
  • the unbleached fibres are separated from the used cooking chemicals, so-called black liquor, by washing of the fibres (brownstock) with water.
  • the obtained suspension of unbleached fibres is then transferred to a bleaching process.
  • the bleaching of the cellulosic fibre suspension is performed in a bleaching process comprising at least one acidic stage, where pH of the cellulosic fibre suspension is ⁇ 6, preferably ⁇ 5.
  • the acidic stage may be, for example, an acid hydrolysis stage, commonly denoted as A-stage, and/or a chlorine dioxide stage, commonly denoted as D-stage.
  • the bleaching process may comprise one or more acidic stages.
  • the bleaching process further comprises one or more alkaline extraction stages, located after an acidic stage or between two acidic stages. In an alkaline extraction stage the pH of the cellulosic fibre suspension is raised at least pH 9, preferably at least pH 10.
  • the pitch control agent according to the present invention comprises at least one cationic polymer with cationic functional groups which are hydrolysed at pH 9 or higher.
  • the pitch control agent is added to the cellulosic fibre suspension before an acidic stage of the bleaching process.
  • the pitch control agent comprising at least one cationic polymer can be added to the cellulosic fibre suspension in any bleaching process stage and/or bleaching process location where talc is conventionally added to the cellulosic fibre suspension during the bleaching process.
  • the pitch control agent may be added as one dose to the cellulosic fibre suspension, or it may be added to cellulosic fibre suspension as several dosages at several dosing locations along the bleaching process.
  • the pitch control agent is added to the cellulosic fibre suspension after the washing of the cellulosic fibres (brownstock) and before an acidic stage in the bleaching process.
  • the pitch control agent may be added, for example, after the separation of used cooking chemicals and washing of the cellulosic fibres.
  • the pitch control agent comprises at least one polymer, preferably cationic polymer, which comprises cationic functional groups which are hydrolysed at pH 9 or higher.
  • the pitch and pitch-like substances are effectively freed or released from the pitch control agent. This ensures good washing and/or deresination at the alkaline extractions stage and effective removal of pitch and pitch-like substances from the bleaching process.
  • cationic polymer denotes a polymer, which may possess both cationic and anionic functional groups in an aqueous solution at pH 7, as long as the net charge of the polymer is cationic at pH 4.
  • Cationic net charge means that the net charge of the polymer is positive, even if it contains anionic groups.
  • the net charge of a polymer is calculated as the sum of the charges of the cationic and anionic groups present.
  • the pitch control agent may be a mixture of two or more cationic polymers, of which some comprise hydrolysable cationic functional groups.
  • the pitch control agent may comprise at least 25 weight-%, preferably at least 50 weight-%, more preferably at least 75 weight-%, even more preferably at least 90 weight-%, of a cationic polymer, which comprises cationic functional groups which are hydrolysed at pH 9 or higher, calculated from the dry weight of total polymers of the pitch control agent.
  • the pitch control agent consists of cationic polymer(s), which comprise(s) cationic functional groups which are hydrolysed at pH 9 or higher.
  • the pitch control agent comprises a cationic polymer, preferably a copolymer of (meth)acrylamide, which has a weight average molecular weight MW of 1 500 000 - 6 000 000 g/mol, preferably 2 000 000 - 5 000 000 g/mol, more preferably 2 500 000 - 4 500 000 g/mol, even more preferably 2 700 000 - 4 300 000 g/mol.
  • the weight average molecular weight of the cationic polymer may be in a range of 3 000 000 - 5 000 000 g/mol or 3 500 000 - 5 500 000 g/mol. It has been observed that the defined molecular weight ensures proper interaction between the cationic polymer, pitch, and pitch-like substances in the acidic stage.
  • weight average molecular weight is used to describe the magnitude of the polymer chain length.
  • the average molecular weight range given for the parameters in used conditions is 490 000 - 3 200 000 g/mol, but the same parameters are used to describe the magnitude of molecular weight also outside this range.
  • pH of the polymer solutions for intrinsic viscosity determination is adjusted to 2.7 by formic acid.
  • the pitch control agent may comprise polyacrylamide obtained by copolymerisation of (meth)acrylamide and cationic monomers.
  • the cationic polyacrylamide which is suitable for use as a pitch control agent may be obtained by copolymerisation of (meth)acrylamide and at least one cationic monomer selected from a group consisting of 2-(dimethylamino)ethyl acrylate (ADAM), [2-(acryloyloxy)ethyl]trimethylammonium chloride (ADAM-Cl), 2-(dimethylamino)ethyl acrylate benzylchloride, 2-(dimethylamino)ethyl acrylate dimethylsulphate, 2-dimethylaminoethyl methacrylate (MADAM), [2-(methacryloyloxy)ethyl] trimethylammonium chloride (MADAM-Cl), 2-dimethylaminoethyl methacrylate dimethylsulphate, [3-(acryl
  • the pitch control agent comprises cationic polyacrylamide which may be obtained by copolymerisation of (meth)acrylamide and at least one cationic monomer comprising functional groups that are hydrolysed at pH 9 or higher.
  • Preferable monomers may be selected from the group consisting of 2-(dimethylamino)ethyl acrylate (ADAM), [2-(acryloyloxy)ethyl]trimethylammonium chloride (ADAM-Cl), 2-dimethylaminoethyl methacrylate (MADAM) and [2-(methacryloyloxy)ethyl] trimethylammonium chloride (MADAM-Cl).
  • These monomers may be copolymerised together with acrylamide and/or methacrylamide monomers in order to obtain copolymers with cationic functional groups that are hydrolysed at pH 9 or higher and thus especially suitable for pitch control during bleaching of cellulosic fibres.
  • the pitch control agent may comprise a cationic polyacrylamide which is obtained by copolymerisation of (meth)acrylamide and 4 - 60 mol-%, preferably 5 - 50 mol-%, more preferably 5 - 40 mol-%, or sometimes even more preferably 5 - 25 mol-%, of cationic monomers, preferably cationic monomers that are hydrolysed at pH 9 or higher.
  • cationic polyacrylamide which is obtained by copolymerisation of (meth)acrylamide and 4 - 15 mol-%, preferably 5 - 13 mol-%, more preferably 6 - 12 mol-%, of cationic monomers.
  • the cationic polyacrylamide may have a total ionicity in a range of 4 - 15 mol-%, preferably 5 - 13 mol-%, more preferably 6 - 12 mol-%, even more preferably 6 - 10 mol-%.
  • the pitch control agent may comprise a polymer, which is a net cationic amphoteric polyacrylamide.
  • Net cationic amphoteric polyacrylamide may be obtained by copolymerisation of acrylamide or methacrylamide together with both anionic monomers and cationic monomers, which are hydrolysed at pH 9 or higher.
  • amphoteric polyacrylamide is obtained by copolymerisation of acrylamide together with both anionic monomers and cationic monomers.
  • the net cationic amphoteric polyacrylamide may obtained by gel polymerisation of (meth)acrylamide together with anionic monomers and cationic monomers.
  • the anionic groups of the amphoteric polymer may improve the removal of pitch and pitch-like substances.
  • the cationic groups of the polymer are hydrolysed at pH 9 or higher, the pitch and pitch-like substances are released.
  • the anionic functional groups of the polymer exert a repelling force to the pitch and pitch-like substances. This may improve and make the removal of the pitch and pitch-like substances even more effective.
  • the pitch control agent may comprise a net cationic amphoteric polyacrylamide where 53 - 90 %, preferably 50 - 85 %, more preferably 60 - 80 %, of the charged groups of the amphoteric polyacrylamide are cationic groups, which are hydrolysed at pH 9 or higher.
  • the anionic groups in the polymer structure may originate from monomers selected from unsaturated mono- or dicarboxylic acids, such as acrylic acid, maleic acid, fumaric acid, itaconic acid, aconitic acid, mesaconic acid, citraconic acid, crotonic acid, isocrotonic acid, angelic acid or tiglic acid.
  • unsaturated mono- or dicarboxylic acids such as acrylic acid, maleic acid, fumaric acid, itaconic acid, aconitic acid, mesaconic acid, citraconic acid, crotonic acid, isocrotonic acid, angelic acid or tiglic acid.
  • the anionic groups originate from acrylic acid or itaconic acid.
  • the cationic groups may originate from cationic monomers listed earlier in this application.
  • the amphoteric polyacrylamide may comprise ⁇ 80 mol-%, preferably ⁇ 70 mol-%, more preferably ⁇ 50 mol-% or ⁇ 40 mol-% of structural units originating from anionic and cationic monomers.
  • the amphoteric polymer may comprise 5 - 80 mol-%, preferably 7 - 70 mol-%, preferably 7 - 50 mol-% or 7 - 40 mol-% of structural units originating from anionic and cationic monomers.
  • the amphoteric polymer may comprise 5 - 30 mol-%, preferably 5 - 20 mol-% or 5 - 15 mol-% of structural units originating from cationic monomers, which are hydrolysed at pH 9 or higher, and/or 1 - 40 mol-%, preferably 3 - 30 mol-% or 5 - 20 mol-% of structural units originating from anionic monomers.
  • the amphoteric polyacrylamide may comprise at least 85 mol-% structural units derived from acrylamide and/or methacrylamide monomers and ⁇ 15 mol-% of structural units originating anionic and cationic monomers.
  • the percentage values are calculated from the total dry weight of the polymer.
  • the total ionicity of the amphoteric polyacrylamide is in the range of 4 - 15 mol-%, preferably 5 - 13 mol-%, more preferably 6 - 12 mol-%, even more preferably 6 - 10 mol-%.
  • Total ionicity includes all groups having ionic charge in the amphoteric polyacrylamide, most of the charged groups originating from the ionic monomers, but including also other charged groups originating from chain termination agents or the like. It has been observed that in some embodiments it is beneficial when the total ionicity of the amphoteric polymer is ⁇ 15 mol-%, especially when the average molecular weight of the polymer is 2 000 000 - 6 000 000 g/mol.
  • the pitch control agent which comprises the cationic polymer with hydrolysable functional groups is added in amount of ⁇ 500 g cationic polymer/ton dry pulp, preferably ⁇ 300 g cationic polymer/ton dry pulp, more preferably ⁇ 200 g cationic polymer/ton dry pulp or ⁇ 100 g/ton dry pulp. It is possible to use lower dosage of pitch control agent when it comprises cationic polymer.
  • Example 1 unbleached, oxygen delignified birch pulp was bleached in the laboratory with a conventional D-E-D (chlorine dioxide - alkali extraction - chlorine dioxide) bleaching sequence.
  • D-E-D chlorine dioxide - alkali extraction - chlorine dioxide
  • talc (reference) or pitch control agents A or B were added to the pulp before each acidic bleaching stage (D).
  • Talc was commercial talc used for pulp applications.
  • Pitch control agent A was amphoteric polyacrylamide originating from about 7 mol-% of cationic monomers and 2 mol-% of anionic monomers; weight average weight about 4 000 000 g/mol; a net charge of about +0.6 meg/g at pH 7.
  • Pitch control agent B was a polymer mixture comprising poly-DADMAC and cationic polyacrylamide in ratio 1:1, total polymer content of the mixture was 35 weight-%.
  • Poly-DADMAC had weight average molecular weight about 250 000 g/mol and charge density of about +6 meq/g.
  • Cationic polyacrylamide originated from 10 mol-% of cationic monomers, had weight average molecular weight about 5 000 000 g/mol and a charge density of about +1.3 meq/g at pH 7.
  • the pitch control agent B had a net charge of about 3.6 - 3.7 meg/g at pH 7
  • the amount of talc added to the pulp before each bleaching stage was 1 kg/t and the amount of the pitch control agent A and B were 300 g/t before each bleaching stage. After each bleaching stage the filtrates and washed pulps were sampled for extractives. The pulp was washed afterthe bleaching stages with two times 20 amount of water in ratio to pulp.
  • Example 2 Extractives Bleaching stage D0 D0 E E D1 D1 pulp [mg/g] filtrate [mg/l] pulp [mg/g] filtrate [mg/l] filtrate [mg/l] pulp [mg/g] 0-REF 4.6. 76.5 0.40 170.9 0.3 4.1 Talc (ref.) 5.2 94.1 0.40 332.5 0.4 4.3 Agent A 6.7 68.0 0.50 596.4 0.5 4.5 Agent B 6.0 79.0 0.50 425.6 0.4 3.2
  • Example 2 oxygen delignified birch pulp was bleached in the laboratory with a conventional bleaching sequence, comprising an acidic chlorine dioxide stage (D 0 ) followed by alkali extraction stage (E).
  • the bleaching conditions are given in Table 3.
  • the amount of talc added to the pulp suspension before the DO-bleaching stage was 3 kg/t.
  • the cationic polymers were added in amount of 200 g/t, except Poly A, for which addition amounts of 100 and 200 g/t were tested.
  • the pulp was washed after D0 and E stages with water two times. For each washing, water: pulp ratio was 20:1.
  • the washed pulps were analysed for extractives by using gas chromatography. The results are shown in Table 4.
  • the percentage value in Table 4 indicates amount of removed extractives. It can be seen that the pitch control agents according to present invention and comprising cationic polymers with functional groups which are hydrolysed at pH, provide as effective, or even improved, extractives removal than talc. It can be further seen that compared to the reference polymers from Poly E to Poly H, the polymers Poly A - Poly D which comprised hydrolysing cationic groups were significantly more effective in removal of neutral pitch and pitch-like substances such as sterols, steryl esters and betulinol.

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  • Chemical Kinetics & Catalysis (AREA)
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  • Wood Science & Technology (AREA)
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Claims (12)

  1. Procédé de contrôle de dépôts résineux et/ou d'élimination de dépôts résineux pendant le blanchiment de fibres cellulosiques, dans lequel
    - des fibres cellulosiques sont obtenues à partir d'un procédé de cuisson chimique et formées en une suspension aqueuse de fibres cellulosiques,
    - le blanchiment de la suspension de fibres cellulosiques est réalisé dans un procédé de blanchiment comprenant au moins une étape acide, dans laquelle le pH de la suspension de fibres cellulosiques est <6, et une ou plusieurs étapes d'extraction alcaline dans lesquelles le pH de la suspension de fibres cellulosiques est porté à au moins pH 9, situées après l'étape acide ou entre deux étapes acides, dans lequel
    - un agent de contrôle de dépôts résineux est ajouté à la suspension de fibres cellulosiques après une séparation de produits chimiques de cuisson usés et un lavage des fibres cellulosiques et avant l'étape acide, dans laquelle l'agent de contrôle de dépôts résineux comprend au moins un polymère cationique comprenant un polyacrylamide obtenu par copolymérisation de (méth)acrylamide et de monomères cationiques comprenant des groupes fonctionnels cationiques qui sont hydrolysés à pH 9 ou plus, par lesquels les groupes fonctionnels cationiques interagissent avec des dépôts résineux et des substances analogues aux dépôts résineux à l'étape acide, dans laquelle le pH est <6, et, à l'étape d'extraction alcaline suivante, au moins une partie ou la totalité des groupes fonctionnels cationiques du polymère cationique sont hydrolysés, et les dépôts résineux et les substances analogues aux dépôts résineux sont libérés et éliminés du procédé de blanchiment.
  2. Procédé selon la revendication 1, caractérisé en ce que l'agent de contrôle de dépôts résineux comprend au moins 25 % en poids, de préférence au moins 50 % en poids, plus préférentiellement au moins 75 % en poids, du polymère cationique comprenant des groupes fonctionnels cationiques qui sont hydrolysés à pH 9 ou plus, calculés à partir du poids sec de l'ensemble de polymères de l'agent de contrôle de dépôts résineux.
  3. Procédé selon la revendication 1 ou 2, caractérisé en ce que le polymère cationique présente un poids moléculaire moyen en poids MW de 1 500 000 - 6 000 000 g/mol, de préférence 2 000 000 - 5 000 000 g/mol, plus préférentiellement 2 500 000 - 4 500 000 g/mol, encore plus préférentiellement 2 700 000 - 4 300 000 g/mol.
  4. Procédé selon la revendication 1, caractérisé en ce que l'agent de contrôle de dépôts résineux comprend un polyacrylamide cationique obtenu par copolymérisation de (méth)acrylamide et de 4 - 60 mol-%, de préférence 5 - 50 mol-%, plus préférentiellement 5 - 40 mol-% de monomères cationiques.
  5. Procédé selon la revendication 1 ou 4, caractérisé en ce que le polyacrylamide cationique présente une ionicité totale dans une plage de 4 - 15 mol-%, de préférence 5 - 13 mol-%, plus préférentiellement 6 - 12 mol-%, encore plus préférentiellement 6 - 10 mol-%.
  6. Procédé selon les revendications 1, 4 ou 5, caractérisé en ce que le polyacrylamide cationique est un polyacrylamide amphotère globalement cationique, de préférence obtenu par polymérisation en gel de (méth)acrylamide conjointement avec des monomères anioniques et cationiques.
  7. Procédé selon la revendication 6, caractérisé en ce que 53 - 90 %, de préférence 50 - 85 %, plus préférentiellement 60 - 80 %, des groupes chargés du polyacrylamide amphotère sont cationiques.
  8. Procédé selon l'une quelconque des revendications précédentes 1, 5 - 7, caractérisé en ce que le polyacrylamide cationique est obtenu par copolymérisation de (méth)acrylamide et d'au moins un monomère cationique choisi à partir d'un groupe constitué d'acrylate de 2-(diméthylamino)éthyle (ADAM), de chlorure de [2-(acryloyloxy)éthyle]triméthylammonium (ADAM-Cl), chlorure de benzyle acrylate de 2-(diméthylamino)éthyle, sulfate de diméthyle acrylate de 2-(diméthylamino)éthyle, méthacrylate de 2-diméthylaminoéthyle (MADAM), chlorure de [2-(méthacryloyloxy)éthyle]triméthylammonium (MADAM-Cl), sulfate de diméthyle méthacrylate de 2-diméthylaminoéthyle, chlorure de [3-(acryloylamino)propyl]triméthylammonium (APTAC), et chlorure de [3-(méthacryloylamino)propyl]triméthylammonium (MAPTAC).
  9. Procédé selon l'une quelconque des revendications précédentes 1 - 8, caractérisé en ce que les fibres cellulosiques proviennent du procédé de cuisson chimique qui est un procédé de cuisson Kraft.
  10. Procédé selon l'une quelconque des revendications précédentes 1 - 9, caractérisé en ce que l'agent de contrôle de dépôts résineux est ajouté en une quantité <500 g/tonne de pâte sèche, de préférence <300 g/tonne de pâte sèche, plus préférentiellement <200 g/tonne de pâte sèche ou <100 g/tonne de pâte sèche.
  11. Utilisation d'un polymère cationique comprenant des groupes fonctionnels cationiques qui sont hydrolysés à pH 9 ou plus en tant qu'agent de contrôle de dépôts résineux dans un procédé de blanchiment de fibres cellulosiques, comprenant au moins une étape acide, dans lequel le pH de la suspension de fibres cellulosiques est <6, et une ou plusieurs étapes d'extraction alcaline dans lesquelles le pH de la suspension de fibres cellulosiques est porté à au moins pH 9, situées après une étape acide ou entre deux étapes acides, dans lequel le polymère cationique est un polyacrylamide cationique obtenu par copolymérisation de (méth)acrylamide et d'au moins un monomère cationique.
  12. Utilisation selon la revendication 11, caractérisée en ce que le polymère cationique est utilisé comme agent de contrôle de dépôts résineux pour l'élimination de dépôts résineux neutres et de substances analogues aux dépôts résineux choisies à partir d'esters stéryliques, de stérols et/ou du bétulinol.
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EP4023813A1 (fr) * 2020-12-29 2022-07-06 Technische Universität Wien Procédé de fabrication de produits à base de bois comme matière première

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FR2655668B1 (fr) * 1989-12-11 1995-06-09 Du Pin Cellulose Procede de blanchiment de pates cellulosiques chimiques.
US5256252A (en) * 1992-07-15 1993-10-26 Nalco Chemical Company Method for controlling pitch deposits using lipase and cationic polymer
KR960037956A (ko) * 1995-04-17 1996-11-19 레이몬드 더블유. 캠벨 혼합 열대 경목 펄프로부터 핏치를 제거하는 방법
US5725779A (en) * 1996-10-03 1998-03-10 Cytec Technology Corp. Anionic water-soluble polymer precipitation in salt solution
PT1070783E (pt) * 1999-07-16 2003-07-31 Nordland Papier Gmbh Processo para optimizacao do doseamento de substancias de transferencia de residuos de papel
GB0018314D0 (en) * 2000-07-27 2000-09-13 Ciba Spec Chem Water Treat Ltd Processes of reducing contamination from cellulosic suspensions
PT1607519E (pt) * 2004-06-14 2008-04-16 Warwick Internat Group Ltd Activador para branqueamento de pasta
US20060000570A1 (en) * 2004-07-02 2006-01-05 Zhiqiang Song Amphoteric cationic polymers for controlling deposition of pitch and stickies in papermaking
JP5168826B2 (ja) * 2006-06-27 2013-03-27 栗田工業株式会社 ピッチコントロール剤及びピッチコントロール方法
US8980056B2 (en) * 2010-11-15 2015-03-17 Kemira Oyj Composition and process for increasing the dry strength of a paper product
FI125712B (en) * 2012-11-13 2016-01-15 Kemira Oyj Paper-making material and its use
FI126610B (en) * 2015-01-27 2017-03-15 Kemira Oyj Particulate polymer product and its use
EP3246466B1 (fr) * 2016-05-20 2018-02-28 Kemira Oyj Procédé et système de traitement destinés à fabriquer du papier
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FI127289B (en) * 2016-11-22 2018-03-15 Kemira Oyj Use of a polymer product to control the formation of precipitates in the manufacture of paper or board
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JP7259188B2 (ja) * 2017-12-15 2023-04-18 ケミラ・オーワイジェイ 溶解ガス浮上分離によって水性フィードを処理するための方法

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EP4165243C0 (fr) 2026-02-18
EP4165243A1 (fr) 2023-04-19
ES3063911T3 (en) 2026-04-21
CA3178055A1 (fr) 2021-12-23
CN115702272A (zh) 2023-02-14
BR112022022809A2 (pt) 2022-12-27
WO2021255335A1 (fr) 2021-12-23
US20230212821A1 (en) 2023-07-06

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