CN118308895A - Pulp bleaching or pulp delignification process - Google Patents
Pulp bleaching or pulp delignification processInfo
- Publication number
- CN118308895A CN118308895A CN202410441658.XA CN202410441658A CN118308895A CN 118308895 A CN118308895 A CN 118308895A CN 202410441658 A CN202410441658 A CN 202410441658A CN 118308895 A CN118308895 A CN 118308895A
- Authority
- CN
- China
- Prior art keywords
- alkaline earth
- earth metal
- pulp
- composition
- bleaching
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims abstract description 81
- 230000008569 process Effects 0.000 title claims abstract description 40
- 238000004076 pulp bleaching Methods 0.000 title claims description 25
- 239000000203 mixture Substances 0.000 claims abstract description 151
- 239000011347 resin Substances 0.000 claims abstract description 43
- 229920005989 resin Polymers 0.000 claims abstract description 43
- 229910001860 alkaline earth metal hydroxide Inorganic materials 0.000 claims abstract description 42
- 229910000287 alkaline earth metal oxide Inorganic materials 0.000 claims abstract description 42
- -1 alkaline earth metal salt Chemical class 0.000 claims abstract description 42
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims abstract description 41
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 28
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 24
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000007844 bleaching agent Substances 0.000 claims abstract description 18
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 15
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 12
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 12
- 150000007522 mineralic acids Chemical class 0.000 claims abstract description 9
- 238000002156 mixing Methods 0.000 claims abstract description 8
- 238000011065 in-situ storage Methods 0.000 claims abstract description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 43
- 239000000654 additive Substances 0.000 claims description 30
- 239000007787 solid Substances 0.000 claims description 28
- 239000002002 slurry Substances 0.000 claims description 27
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 26
- 230000000996 additive effect Effects 0.000 claims description 19
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 claims description 18
- 239000000454 talc Substances 0.000 claims description 17
- 229910052623 talc Inorganic materials 0.000 claims description 17
- 239000000123 paper Substances 0.000 claims description 16
- 239000000440 bentonite Substances 0.000 claims description 15
- 229910000278 bentonite Inorganic materials 0.000 claims description 15
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical group [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 13
- 239000011777 magnesium Substances 0.000 claims description 11
- 239000002270 dispersing agent Substances 0.000 claims description 7
- 239000000835 fiber Substances 0.000 claims description 7
- 235000019353 potassium silicate Nutrition 0.000 claims description 7
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 6
- 239000004115 Sodium Silicate Substances 0.000 claims description 6
- 125000002091 cationic group Chemical group 0.000 claims description 6
- 229910052749 magnesium Inorganic materials 0.000 claims description 6
- 229910052911 sodium silicate Inorganic materials 0.000 claims description 6
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 5
- 150000001342 alkaline earth metals Chemical class 0.000 claims description 5
- 239000011575 calcium Substances 0.000 claims description 5
- 229910052791 calcium Inorganic materials 0.000 claims description 5
- 230000002209 hydrophobic effect Effects 0.000 claims description 4
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 3
- 102000004190 Enzymes Human genes 0.000 claims description 3
- 108090000790 Enzymes Proteins 0.000 claims description 3
- 239000005909 Kieselgur Substances 0.000 claims description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 3
- 229910021536 Zeolite Inorganic materials 0.000 claims description 3
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 claims description 3
- 230000002902 bimodal effect Effects 0.000 claims description 3
- 229920006317 cationic polymer Polymers 0.000 claims description 3
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims description 3
- 239000010445 mica Substances 0.000 claims description 3
- 229910052618 mica group Inorganic materials 0.000 claims description 3
- 239000010457 zeolite Substances 0.000 claims description 3
- 238000004061 bleaching Methods 0.000 abstract description 70
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 36
- 239000000347 magnesium hydroxide Substances 0.000 description 36
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 36
- 239000002253 acid Substances 0.000 description 20
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 18
- 239000004615 ingredient Substances 0.000 description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 17
- 150000002978 peroxides Chemical class 0.000 description 12
- 229920001131 Pulp (paper) Polymers 0.000 description 10
- 230000002378 acidificating effect Effects 0.000 description 9
- 230000015556 catabolic process Effects 0.000 description 9
- 238000006731 degradation reaction Methods 0.000 description 9
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 8
- 239000002655 kraft paper Substances 0.000 description 8
- 235000019341 magnesium sulphate Nutrition 0.000 description 8
- 239000000126 substance Substances 0.000 description 8
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 7
- 239000002738 chelating agent Substances 0.000 description 7
- 230000008901 benefit Effects 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 229910052500 inorganic mineral Inorganic materials 0.000 description 6
- 235000010755 mineral Nutrition 0.000 description 6
- 239000011707 mineral Substances 0.000 description 6
- 150000007513 acids Chemical class 0.000 description 5
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 5
- 239000000920 calcium hydroxide Substances 0.000 description 5
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 5
- 238000009472 formulation Methods 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 241001397809 Hakea leucoptera Species 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 4
- 239000000945 filler Substances 0.000 description 4
- 238000009776 industrial production Methods 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 239000006174 pH buffer Substances 0.000 description 4
- 239000008188 pellet Substances 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 230000035484 reaction time Effects 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 239000011122 softwood Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 239000004094 surface-active agent Substances 0.000 description 4
- 238000005406 washing Methods 0.000 description 4
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 3
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 3
- 229910001420 alkaline earth metal ion Inorganic materials 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000000227 grinding Methods 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 229910001425 magnesium ion Inorganic materials 0.000 description 3
- 239000004033 plastic Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000004927 clay Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 description 2
- 229910001385 heavy metal Inorganic materials 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- YIXJRHPUWRPCBB-UHFFFAOYSA-N magnesium nitrate Chemical compound [Mg+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O YIXJRHPUWRPCBB-UHFFFAOYSA-N 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- 159000000003 magnesium salts Chemical class 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000002023 wood Substances 0.000 description 2
- 239000004155 Chlorine dioxide Substances 0.000 description 1
- 235000019738 Limestone Nutrition 0.000 description 1
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- 230000002292 Radical scavenging effect Effects 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000012736 aqueous medium Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052599 brucite Inorganic materials 0.000 description 1
- QXDMQSPYEZFLGF-UHFFFAOYSA-L calcium oxalate Chemical compound [Ca+2].[O-]C(=O)C([O-])=O QXDMQSPYEZFLGF-UHFFFAOYSA-L 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 1
- YLUIKWVQCKSMCF-UHFFFAOYSA-N calcium;magnesium;oxygen(2-) Chemical compound [O-2].[O-2].[Mg+2].[Ca+2] YLUIKWVQCKSMCF-UHFFFAOYSA-N 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- 239000001913 cellulose Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 235000019398 chlorine dioxide Nutrition 0.000 description 1
- 239000008139 complexing agent Substances 0.000 description 1
- AQEDFGUKQJUMBV-UHFFFAOYSA-N copper;ethane-1,2-diamine Chemical compound [Cu].NCCN AQEDFGUKQJUMBV-UHFFFAOYSA-N 0.000 description 1
- 239000007857 degradation product Substances 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- GUJOJGAPFQRJSV-UHFFFAOYSA-N dialuminum;dioxosilane;oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Al+3].[Al+3].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O GUJOJGAPFQRJSV-UHFFFAOYSA-N 0.000 description 1
- 235000014113 dietary fatty acids Nutrition 0.000 description 1
- 235000021463 dry cake Nutrition 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000000194 fatty acid Substances 0.000 description 1
- 229930195729 fatty acid Natural products 0.000 description 1
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000009897 hydrogen peroxide bleaching Methods 0.000 description 1
- 230000005661 hydrophobic surface Effects 0.000 description 1
- 229920005610 lignin Polymers 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 229910001629 magnesium chloride Inorganic materials 0.000 description 1
- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 description 1
- 239000000391 magnesium silicate Substances 0.000 description 1
- 229910052919 magnesium silicate Inorganic materials 0.000 description 1
- 235000019792 magnesium silicate Nutrition 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 229910052901 montmorillonite Inorganic materials 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 229910052615 phyllosilicate Inorganic materials 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000013055 pulp slurry Substances 0.000 description 1
- 238000004537 pulping Methods 0.000 description 1
- 239000002516 radical scavenger Substances 0.000 description 1
- 229920002545 silicone oil Polymers 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000004448 titration Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 230000004584 weight gain Effects 0.000 description 1
- 235000019786 weight gain Nutrition 0.000 description 1
Abstract
The present invention relates to a method for bleaching or delignifying pulp, said method comprising: a composition is formed by a process comprising the steps of: mixing an alkaline earth metal oxide and/or an alkaline earth metal hydroxide with an inorganic acid or sulfur dioxide or carbon dioxide, thereby forming in situ a mixture of the alkaline earth metal oxide and/or alkaline earth metal hydroxide with an alkaline earth metal salt, optionally in the presence of one or more resin control agents, wherein the pH of the resulting composition is from 7 to 10.5; adding the composition to the pulp to be bleached; and then adding hydrogen peroxide and optionally any other alkaline bleach.
Description
The application is a divisional application, the application number of which is 201680037901.5, the application date is 2016, 9 and 29, the application is named as a method for bleaching water-containing paper pulp and a composition for the method "
Technical Field
The present invention relates to a composition for bleaching pulp. In particular, the composition is suitable for use as an additive for adjusting the pH and/or controlling unwanted substances in pulp slurry during the pulp bleaching step. The use of the composition, for example the use of the composition in pulp preparation or paper making processes, and the pulp bleaching process using the composition are also part of the invention. Finally, kits for forming the compositions of the invention or ingredients for use in the methods of the invention are also part of the invention.
Background
Conventional bleaching processes for pulp typically employ alkaline hydrogen peroxide as a bleaching agent. To this end, hydrogen peroxide and water-soluble alkaline compounds (e.g., sodium hydroxide and/or water glass) are introduced to the pulp to improve the whiteness and/or brightness of wood pulp, recycled pulp, or any other chemical or mechanical pulp (e.g., pulp used in the papermaking process). The use of chelating agents such as EDTA to remove some metal ions from the pulp followed by the addition of peroxide allows for a more efficient use of the peroxide. Magnesium salts and sodium silicate may also be added to improve bleaching with alkaline peroxide. Magnesium salts are also commonly used to protect cellulosic fibers from excessive degradation and consequent loss of strength during delignification and bleaching process steps.
Recently, alkaline earth metal hydroxides and/or alkaline earth metal oxides have been employed in place of sodium hydroxide and water glass to reduce the need for chelating agents and sodium silicate (see, e.g., that disclosed in Li et al ,Pulp&Paper Canada 106:6(2005),T125～T129"Using magnesium hydroxide(Mg(OH)2)as the alkali source in peroxide bleaching at Irving paper"). WO 2014/195478 A1 discloses the use of resin control additives in combination with Mg (OH) 2 and/or MgO in paper bleached pulp to avoid the formation of magnesium-based salts of acids and resins in the pulp.
Alkaline earth metal hydroxides and alkaline earth metal oxides are only slightly soluble in aqueous solutions, which may lead to reduced bleaching efficiency and reduced efficiency in terms of fiber protection. In addition, it is known to use MgSO 4 as a radical scavenger and pulp stabilizer in paper bleached pulp. MgSO 4 is expensive and difficult to store due to its hygroscopicity.
Finally, maintaining high pulp viscosity is a concern in pulp processing, including pulp bleaching. Pulp viscosity is a measure indicative of the strength of the fiber. The arrangement of the pulp processing device, such as a pulp bleaching device, is specifically designed to maintain the pulp viscosity while achieving the desired bleaching result. Thus, variations in pulp viscosity can be problematic.
There are several problems with the prior art.
Disclosure of Invention
The invention is defined in the appended claims.
In particular, embodiments of the present invention are compositions for use in an aqueous pulp bleaching process, the compositions comprising: (i) One or more alkaline earth metal oxides and/or one or more alkaline earth metal hydroxides; (ii) one or more alkaline earth metal salts; and (iii) optionally one or more resin control additives (pitch control additive). It has been found that the alkalinity of the chemical formulation decreases in the presence of alkaline earth metal salts (e.g. alkaline earth metal sulphates), resulting in improved solubility of the alkaline earth metal oxides and/or alkaline earth metal hydroxides in the formulation to be dosed into the pulp afterwards, while at the same time obtaining a beneficial radical scavenging effect and slurry stabilizing effect of the alkaline earth metal salts (e.g. alkaline earth metal sulphates). For example, the alkaline earth metal may be selected from magnesium, calcium or a mixture of magnesium and calcium.
According to one embodiment, the alkaline earth metal salt is an alkaline earth metal sulfate, such as calcium sulfate or magnesium sulfate.
According to one embodiment, the resin control additive is selected from talc, bentonite, zeolite, diatomaceous earth, cationic mica, hydrophobic carbonate, resin decomposing enzymes, cationic polymers designed to trap and immobilize resins or resinous components on the fiber surface, aluminum sulfate, polyaluminum chloride and dispersants specifically designed to disperse resins and resinous components, and mixtures thereof. It has been found that these resin control agents result in a reduction of fatty acid salts and resins in the pulp. According to one embodiment, the resin reducing agent is talc, such as micronized talc, bimodal talc, cationic talc or mixtures thereof. According to one embodiment, the resin control additive is bentonite, such as activated bentonite. In certain embodiments, the bentonite is activated with an alkaline earth oxide and/or an alkaline earth hydroxide and/or an alkaline earth salt. Bentonite clay can bind heavy metals in paper bleaching compositions and reduce its disruption to the bleaching process (e.g., by degrading the peroxide responsible for the bleaching process).
According to the invention, the composition may be a dry particulate composition, or the composition may be an aqueous slurry, or the composition may be present as an ingredient of an aqueous slurry comprising other components, for example the composition may be present as an ingredient of an aqueous paper bleached pulp. According to the present invention, the particulate composition of the present invention may be mixed with water to prepare an aqueous slurry, which is also part of the present invention.
According to the invention, the composition may be an aqueous slurry having a solids content of up to 75% by weight, for example from 10 to 75% by weight, based on the total weight of the slurry.
According to the invention, the weight ratio of (i) alkaline earth metal oxide and/or alkaline earth metal hydroxide to (ii) alkaline earth metal salt is from 1:10 to 100:1. It has been found that the advantageous effects of the invention are best obtained if these components are present in this ratio. For example, the weight ratio may be 1:5 to 50:1, such as 1:2 to 25:1, or 1:1 to 10:1, such as about 2:1 or about 70:30 or about 80:20 or about 90:10.
According to one embodiment, the composition may further comprise one or more of the following additives: a dispersing agent; a filler; a surfactant; a bleaching agent; a chelating agent; a pH buffer.
According to another aspect of the present invention there is provided a kit of parts comprising: a first container containing an alkaline earth metal oxide and/or an alkaline earth metal hydroxide, the second container containing an aqueous mineral acid solution, and/or a third container containing sulfur dioxide or carbon dioxide. It has been found that the compositions of the invention can be readily obtained using the kit. In one embodiment, the aqueous mineral acid is aqueous sulfuric acid.
Methods of making the compositions of the present invention are also part of the present invention, the methods comprising: a step of mixing an alkaline earth metal oxide and/or an alkaline earth metal hydroxide with an acid (e.g., a mineral acid such as sulfuric acid) or sulfur dioxide or carbon dioxide or an alkaline earth metal salt (e.g., an alkaline earth metal sulfate or an alkaline earth metal carbonate), optionally in the presence of one or more resin control agents. The alkaline earth metal may be selected from, for example, magnesium, calcium, and mixtures thereof.
According to one aspect of the invention, the method may be performed in situ in an aqueous pulp bleaching composition. It has been found that the reaction of the alkaline earth metal oxide and/or alkaline earth metal hydroxide with an acid (e.g., a mineral acid such as sulfuric acid) and/or sulfur dioxide or carbon dioxide occurs efficiently in situ, thereby forming a mixture of the alkaline earth metal oxide and/or alkaline earth metal hydroxide with an alkaline earth metal salt (e.g., an alkaline earth metal sulfate) in situ. For example, the process of the present invention may be carried out by adding a mineral acid (e.g. sulfuric acid) or carbon dioxide or sulfur dioxide to a paper bleached pulp comprising alkaline earth metal oxides and/or alkaline earth metal hydroxides. For example, the methods of the present invention can be performed by adding alkaline earth metal oxides and/or alkaline earth metal hydroxides to an acidic pulp composition (e.g., wherein the only acid present in the acidic pulp composition is an acid naturally present in the pulp composition (i.e., derived from wood), or no extraneous acid is added).
According to one aspect of the invention, the method may include the step of mixing the alkaline earth metal hydroxide with the inorganic acid, wherein the alkali acid equivalent concentration (i.e., molar ratio of hydroxide ions in the alkaline earth metal hydroxide to hydrogen cations in the inorganic acid) is from 10:1 to 1:5, such as about 10:1 or about 5:1 or about 4:1 or about 3:1 or about 2:1 or about 1.5:1 or about 1:1 or about 1:1.5 or about 1:2 or about 1:5. In the case of alkaline earth metal oxides and carbon dioxide or sulfur dioxide, for example, the corresponding acid/base ratio should be employed.
According to one aspect of the invention, the method may be carried out by mixing the components of the kit of one aspect of the invention into paper bleached pulp. The kit has been found to be easy to transport, store and use for the method of the invention.
The use of the compositions, methods or kits of the invention in pulp bleaching processes is also part of the invention. It has been found that by application of the present invention, the pulp bleaching process can be made simpler, more efficient and cheaper, while reducing the need for expensive raw materials or complex procedures.
According to some embodiments, the compositions, methods or kits of the present invention may be used in processes for reducing resin in pulp and/or in processes for protecting pulp from depolymerization (depolymerisation) and/or degradation of pulp (e.g., resulting in the formation of stickies). In this case, methods of reducing depolymerization and/or degradation of the pulp and/or methods of protecting the pulp from formation of degradation products (e.g., stickies) are also part of the invention. Depolymerization or degradation occurs because of the attack of the cellulose molecules by the bleaching chemicals, which results in a decrease of the polymer chain length and thus in a decrease of the pulp strength properties. Very often, this degradation is measured in terms of fiber viscosity. The shorter chain length resulting from depolymerization or degradation results in lower viscosity values and thus lower strength properties, which reduces the value of the pulp produced.
According to some other embodiments of the invention, one or more ingredients of the product or kit of the composition or method of embodiments of the invention are added to the pulp to be bleached before any other alkaline bleaching agent (e.g. water glass, naOH, sodium silicate and/or hydrogen peroxide) is added.
It should be understood that the following detailed description relates to exemplary embodiments of the invention and should not limit the scope of the claims.
Detailed Description
The invention as set forth in the appended claims provides improvements to paper pulping processes (e.g., including bleaching, such as oxygen bleaching, peroxide-oxygen bleaching, oxygen-peroxide bleaching, or oxygen delignification). The improvements may be obtained by the products and kits defined in the appended claims and their use in accordance with the methods and uses defined in the appended claims.
It has been found that the combination of alkaline earth metal hydroxides and/or alkaline earth metal oxides, as well as certain alkaline earth metal salts and optional resin control agents provides a number of advantages over the prior art.
One advantage is that the formation of harmful deposits in the pulp is reduced. This is achieved on the one hand by using alkaline earth metal oxides and/or alkaline earth metal hydroxides in combination with alkaline earth metal salts and on the other hand by the presence of certain resin control agents.
Furthermore, it has been found that the presence of certain alkaline earth metal salts results in a reduction of free radicals formed during bleaching. The presence of free radicals, while desirable for bleaching on the one hand, may also lead to the formation of unwanted byproducts, for example, byproducts from depolymerization and/or degradation of the pulp, such as resins or "stickies", which may lead to caking of the pulp and damage to downstream paper handling equipment.
Moreover, the presence of certain alkaline earth metal salts (e.g., alkaline earth metal sulfates) stabilizes pulp viscosity and improves pulp strength properties. This is important for the usability of pulp in paper and board manufacture and other pulp end uses. According to some aspects of the invention, viscosity stability is achieved by using the compositions or kits of the invention, resulting in viscosity maintenance or reduced viscosity reduction. For example, according to the invention, use of the components of the composition or the kit results in a viscosity change of no more than 10%, such as no more than 5%, or no more than 4%, or no more than 3%, or no more than 2%, or no more than 1%, or no more than 0.5%, or it results in substantially no measurable viscosity change.
It is believed that this "protection" of the viscosity is due to the presence of free alkaline earth metal ions (e.g., magnesium ions) in the slurry. Alkaline earth metal salts are formed in paper pulp from alkaline earth metal hydroxides or alkaline earth metal oxides and acids, resulting in the formation of free alkaline earth metal ions (e.g. magnesium ions) and stabilization of pulp viscosity.
Furthermore, the use of alkaline earth metal salts in the present invention allows adaptation to the pH value in the pulp bleaching formulation. Alkaline slurries are generally obtained with an elevated pH of 10 or more or 11 or more due to the presence of alkaline earth metal oxides and/or alkaline earth metal hydroxides. According to the invention, the use of alkaline earth metal salts results in control of the alkalinity in the pulp bleaching formulation, which may reduce the pH to a value of 7 to 10.5, for example about 8.5. In order to protect the equipment from alkaline ageing and obviously for safety reasons, it is advantageous to operate in the pH region below 10 or near neutral pH region. In addition, lower pH results in better bleaching performance and/or reduced pulp depolymerization and/or degradation. Thus, the loading of alkaline earth metal hydroxide and/or alkaline earth metal oxide in the papermaking pulp can be reduced according to the present invention.
Finally, according to some embodiments of the invention (e.g., kits or methods of the invention), the alkaline earth metal salt is obtained in situ prior to or during the bleaching process by combining an alkaline earth metal oxide and/or an alkaline earth metal hydroxide with a mineral acid or with sulfur dioxide or carbon dioxide. Thus, for example, a composition comprising magnesium hydroxide and magnesium sulfate may be obtained in a pulp bleaching formulation by introducing magnesium hydroxide and an acid (e.g., sulfuric acid) according to the following reaction:
Mg(OH)2+H2SO4(aq)→MgSO4+2H2O
Acids such as aqueous sulfuric acid are readily available and readily stored in large quantities for long periods at the papermaking site. On the other hand, alkaline earth salts (e.g., magnesium sulfate) tend to be expensive to acquire and store and difficult to handle due to their low durability or hygroscopic behavior. Thus, the methods and kits of the present invention result in the formation of the compositions of the present invention and also form part of the present invention and provide additional advantages over the prior art.
The alkaline earth metal hydroxide or alkaline earth metal oxide may be selected from magnesium hydroxide, calcium hydroxide, magnesium oxide and calcium oxide or mixtures thereof. If alkaline earth metal oxides are used, they act in the same manner as alkaline agents by forming the corresponding alkaline earth metal hydroxides in an aqueous medium. These compounds have a low solubility in water and are therefore released into the pulp only at the rate at which they are consumed during bleaching. According to the present invention, control of pH is improved, as alkaline earth metal salts or acids may be added to adjust pH according to embodiments of the present invention.
In certain embodiments, the alkaline earth metal hydroxide may be magnesium hydroxide. In some embodiments, the magnesium hydroxide can be crystalline (e.g., brucite). In other embodiments, the magnesium hydroxide may be in an amorphous form.
In certain embodiments, magnesium hydroxide, calcium hydroxide, and mixtures thereof may be provided by: dolomitic limestone is converted to dolomitic lime, which is then converted to magnesium hydroxide, calcium hydroxide, and mixtures thereof. Such embodiments comprising magnesium hydroxide and calcium hydroxide may provide pulp bleaching benefits described herein as well as reduction of deposits (e.g., calcium oxalate deposits) and/or higher availability of soluble hydroxide ions. The ratio of magnesium hydroxide to calcium hydroxide in such embodiments may be 10:1 to 1:10, such as 5:1 to 1:5, such as 1:2 to 2:1.
The alkaline earth metal salt used in the present invention may be, for example, an alkaline earth metal sulfate such as magnesium sulfate. Magnesium sulfate is a hygroscopic particulate salt. Alkaline earth metal salts are used to help adjust the pH of the slurry and also to stabilize the slurry. Alternatively, magnesium chloride or magnesium nitrate may be used.
The resin control agent used in the composition of certain embodiments of the present invention may be talc (a natural magnesium silicate having a lamellar structure). Alternatively, the resin control agent used in the composition of certain embodiments of the present invention may be bentonite (an absorptive aluminum phyllosilicate comprising montmorillonite). In particular embodiments, bentonite may be activated by an alkaline earth metal hydroxide or an alkaline earth metal oxide (e.g., mg (OH) 2 or Mg (OH)). In certain embodiments, bentonite may act as an ion exchanger for heavy metals (e.g., mn, cr, fe, and/or Ni), which provides the benefit of making these ions less likely to interfere with the bleaching process. In other embodiments, bentonite may stabilize peroxides used in bleaching and/or reduce silicate content.
In certain embodiments, the resin control agent may be a blend of talc and bentonite clay. For example, the ratio of talc to bentonite in such embodiments may be from 10:1 to 1:10, such as from 5:1 to 1:5, such as from 2:1 to 1:2. Such a blend of two different resin control agents shows the benefit of handling more harmful substances in the process, as the two substances have different adsorption properties. The hydrophobic surface of talc preferentially adsorbs the hydrophobic material, whereas bentonite is more attractive to hydrophilic substances.
According to certain embodiments of the present invention, the composition for bleaching pulp may be present as an aqueous slurry. Aqueous slurries are often used in, for example, paper making to introduce solids into the pulp. Thus, the compositions of certain embodiments of the present invention may be introduced to pulp in the form of an aqueous slurry to support hydrogen peroxide bleaching. By having certain embodiments of the composition of the present invention in slurry form, the total weight of the composition is increased. In order to limit weight gain, for example to maintain the transport efficiency of the composition, it is preferred that the aqueous slurry comprising the composition of certain embodiments of the present invention has a solids content of 10 wt.% or more (based on the total weight of the slurry), for example 30 wt.% or more, or 40 wt.% or 45 wt.% or more, or 50 wt.% or more, or even 60 wt.% or more, for example up to 70 wt.%, or 72 wt.%, or 75 wt.%. In order to achieve a high solids content slurry, it may be necessary to include a dispersant in the slurry. The slurry may also contain other ingredients such as fillers, surfactants, bleaching agents, pH buffers or other additives.
In certain embodiments, the composition is in the form of a dry particulate powder. In order to reduce the weight of the composition and improve the transportability, the composition may be transported as a dry powder, and a slurry may be formed only at the place where the composition is used during bleaching. The dry particulate powder may be obtained, for example, by using a spray drying method. The moisture content of the spray-dried particulate compositions of certain aspects of the invention may be low or very low, for example, 5 wt% moisture or less, or 4 wt% moisture or less, or 3 wt% moisture or less, or even 2 wt% moisture or less, for example, about 1 wt% moisture or 0.5 wt% moisture, based on the total amount of solids in the spray-dried particulate powder. The dry composition may also contain other ingredients such as dispersants, fillers, surfactants, bleaching agents, chelating agents, pH buffers or other additives.
In certain embodiments, the composition is in the form of a pellet. According to one aspect, the moisture content of the pellets may be 0.1 wt% to 25 wt%, such as 2wt% to 20 wt% or 5 wt% to 15 wt%, such as about 15 wt% of the total weight of the composition. According to one other aspect, the pellets may comprise 2 to 50 wt% resin control additive and 98 to 50 wt% particulate alkaline earth metal oxide or alkaline earth metal hydroxide or mixture thereof, based on the total solids content of the pellets.
According to certain embodiments of the present invention, the weight ratio of (i) alkaline earth oxide and/or alkaline earth hydroxide to (ii) alkaline earth salt of the composition for bleaching pulp may be from 1:1 to 100:1, such as from 2:1 to 50:1, such as from 3:1 to 25:1, or from 5:1 to 10:1, such as about 70:30 or about 80:20, or about 90:10.
According to certain embodiments of the invention, the kit of parts may comprise amounts of parts in which the above weight ratios may be obtained. It will be appreciated by those skilled in the art that this weight ratio as a result of the above reaction (e.g., magnesium hydroxide reacted with sulfuric acid to give magnesium sulfate) may depend on a number of factors, such as concentration, temperature, relative amounts of ingredients, acidity/basicity prior to the reaction, and the like. According to certain embodiments of the present invention, the process of obtaining the composition of the present invention may be carried out in such a way that the weight ratio described above may be obtained.
If a resin control agent is used in the present invention, the weight ratio of (i) alkaline earth metal oxide, alkaline earth metal hydroxide, and alkaline earth metal salt to (ii) resin control agent may be from 1:9 to 9:1, such as from 3:7 to 7:3, such as from 2:3 to 3:2, such as 1:2 or 1:1 or 2:1.
According to certain embodiments of the present invention, the composition for bleaching pulp may comprise one or more particulate alkaline earth metal oxides or alkaline earth metal hydroxides in an amount of 10% to 90% by weight of the total solids content of the composition, such as 30% to 70% by weight of the total solids content of the composition, such as 40% to 60% by weight of the total solids content of the composition, such as 50% by weight of the total solids content of the composition.
According to certain embodiments of the present invention, the composition for bleaching pulp may comprise an alkali metal salt in an amount of 0.1% to 50% by weight of the total solids content of the composition, such as 1% to 30% by weight of the total solids content of the composition, such as 5% to 15% by weight of the total solids content of the composition, such as 10% by weight of the total solids content of the composition.
According to certain embodiments of the present invention, the composition for bleaching pulp may comprise one or more resin control additives in an amount of 1% to 90% by weight of the total solids content of the composition, such as 10% to 70% by weight of the total solids content of the composition, such as 20% to 60% by weight of the total solids content of the composition, such as 50% by weight of the total solids content of the composition.
Another aspect of the invention is the use of a composition or kit of parts according to certain embodiments of the invention in a pulp bleaching process, such as a bleaching process of paper pulp. For example, the compositions of certain embodiments of the present invention may be used in combination with other additives (e.g., hydrogen peroxide, complexing agents, water glass, or others) during pulp bleaching in a papermaking process.
The composition of the invention may replace completely or partly the known alkaline compositions, such as NaOH. For example, naOH may be omitted entirely as an alkaline agent in the H 2O2 bleaching process, or the amount of NaOH may be reduced by the simultaneous addition of the composition of the invention.
According to certain embodiments of the present invention, it is not required that (i) one or more alkaline earth metal oxides or alkaline earth metal hydroxides or mixtures thereof are mixed together with (ii) one or more alkaline earth metal salts prior to introduction into the pulp to be bleached. Another aspect of the invention is the use of a composition obtained by: one or more (e.g., all) of the components of the composition are separately introduced into the papermaking pulp, or one or more (e.g., all) of the components of the kit of parts are separately introduced into the papermaking pulp, thereby forming the composition in the pulp during bleaching of the pulp.
During bleaching, the compositions or ingredient kits of certain embodiments of the invention may be introduced into the pulp in amounts such that: the amount of the one or more particulate alkaline earth metal oxides or alkaline earth metal hydroxides or mixtures thereof in the pulp is from 0.1 wt.% to 8 wt.% of the total solids content of the pulp during bleaching, such as from 0.2 wt.% to 4 wt.% of the total solids content of the pulp during bleaching, such as from 0.5 wt.% to 2.5 wt.% of the total solids content of the pulp, such as from 1 wt.% or 2 wt.% of the total solids content of the pulp, and the amount of the one or more alkaline earth metal salts in the pulp is from 0.01 wt.% to 5 wt.% of the total solids content of the pulp during bleaching, such as from 0.02 wt.% to 1 wt.% of the total solids content of the pulp during bleaching, such as from 0.05 wt.% to 0.5 wt.% of the total solids content of the pulp, such as from about 0.1 wt.% or about 0.25 wt.% of the total solids content of the pulp.
According to certain embodiments of the present invention, the components of the composition or component kit for bleaching of papermaking pulp may be included in the pulp, for example in the bleaching stage or at the beginning of the bleaching stage or before the bleaching stage. It may also be added during or before the delignification stage. For example, the composition for bleaching of papermaking pulp may be contained in the pulp as early as the grinding stage (during which the pulp ingredients are ground) or at any time between the grinding stage and the bleaching stage. The various components of the compositions of certain embodiments of the present invention may also be added to the papermaking pulp in stages, for example during the grinding stage and/or immediately before the bleaching or delignification step.
For example, according to one embodiment of the present invention, the components of the compositions or component kits for use in bleaching papermaking pulps of some embodiments of the present invention may be introduced into the pulp to be bleached, followed by the introduction of any alkaline bleaching agent (e.g., naOH, water glass, sodium silicate and/or hydrogen peroxide). In this case, the alkaline earth metal oxide or alkaline earth metal hydroxide is activated by the alkaline earth metal salt (e.g. alkaline earth metal sulfate) present and/or the wood-derived organic and/or inorganic acid present in the pulp mixture before the bleaching process starts. For example, according to one embodiment of the invention, alkaline earth metal hydroxide and/or alkaline earth metal oxide is added to an acidic pulp mixture (e.g., where the only acids present are those naturally present in the pulp, and/or no extraneous acid is added) before the bleaching process begins and/or before any alkaline bleaching agent is added.
As mentioned above, this viscosity "protecting" effect is believed to be caused by the presence of free alkaline earth metal ions (e.g. magnesium ions) in the pulp mixture or slurry. This effect is enhanced when alkaline earth ions are formed before any alkaline bleach is introduced to begin bleaching.
According to another embodiment of the invention, the ingredients of the ingredient composition or ingredient kit may be added at an earlier step (e.g. during the addition of a chelating agent such as EDTA or chlorine dioxide in an acidic bleaching step). Such embodiments include all applications in bleaching steps where the ingredients of the ingredient composition or ingredient kit are at a pH below 7.
To avoid confusion, the embodiments described in the numbered sentences below all form part of the invention:
1. A composition for use in a pulp bleaching process, the composition comprising: one or more alkaline earth metal oxides and/or one or more alkaline earth metal hydroxides; one or more alkaline earth metal salts; and optionally one or more resin control additives.
2. The composition of numbered sentence 1 wherein the resin control additive is selected from the group consisting of talc, bentonite, zeolite, diatomaceous earth, cationic mica, hydrophobic carbonate, resin decomposing enzyme, cationic polymer designed to capture and immobilize a resin or resinous component on a fiber surface, aluminum sulfate, polyaluminum chloride, and dispersants specifically designed to disperse the resin and resinous component, and mixtures thereof.
3. A composition according to any one of the preceding numbered sentences, wherein the alkaline earth metal is selected from magnesium, calcium and mixtures thereof.
4. A composition according to any one of the preceding numbered sentences, wherein the resin control additive is selected from micronised talc, bimodal talc and cationic talc.
5. A composition according to any one of numbered sentences 1 to 3, wherein the resin control additive is bentonite, such as activated bentonite.
6. The composition of any of the preceding numbered sentences, which is an aqueous slurry.
7. The composition of numbered sentence 6 wherein the total solids content of the aqueous slurry is from 10 wt% to 75 wt% of the total weight of the slurry.
8. A composition according to any one of the preceding numbered sentences, wherein the weight ratio of (i) alkaline earth metal oxide and/or alkaline earth metal hydroxide to (ii) alkaline earth metal salt is from 1:2 to 100:1.
9. The composition of any of the preceding numbered sentences, further comprising at least one of the following additives: (a) a dispersant; (b) a filler; (c) a surfactant; (d) a bleaching agent; (e) a chelating agent; and (f) a pH buffer.
10. A kit of ingredients comprising: an alkaline earth metal oxide and/or an alkaline earth metal hydroxide stored in the first container, and a second container and/or a third container, in which an aqueous solution of an inorganic acid is stored, and sulfur dioxide and/or carbon dioxide is stored in the third container.
11. A method of forming the composition of any one of numbered sentences 1-9, comprising the steps of: the alkaline earth metal oxide and/or alkaline earth metal hydroxide is mixed with an inorganic acid or sulfur dioxide or carbon dioxide, optionally in the presence of one or more resin control agents.
12. The method of clause 11, which is carried out in an aqueous pulp bleaching composition.
13. The method of numbered sentence 12 wherein the mixing step is performed by adding sulfuric acid or sulfur dioxide or carbon dioxide to a paper bleached pulp comprising alkaline earth metal oxides and/or alkaline earth metal hydroxides.
14. A method according to any one of numbered sentences 11 to 13 comprising the step of mixing the components of the kit of numbered sentence 10 into paper bleached pulp or delignified pulp.
15. Use of a composition or a method or a kit according to any of the preceding numbered sentences in a pulp bleaching process or a pulp delignification process.
16. The use of numbered sentence 15 in a process for reducing resin in pulp.
17. The use of numbered sentence 15 for protecting pulp from depolymerization and/or degradation.
18. The use of numbered sentence 15 in or after an acidic bleaching step.
19. Use according to any of the numbered sentences 15 to 18, wherein the composition or the product of the method or the components of the kit are added to the pulp to be bleached, followed by any other alkaline bleaching agent, such as water glass, sodium silicate, naOH and/or hydrogen peroxide.
20. A method of reducing resin in pulp comprising the use of any one of numbered sentences 15-19.
Examples
As used herein, pulp viscosity is measured in accordance with TAPPI T230 om-08. Furthermore, as used herein, kappa values indicative of lignin residual amounts in pulp are measured according to ISO-302:2012.
In the pulp bleaching process using sodium hydroxide as a bleaching agent, the use of magnesium hydroxide as an additive was compared with the use of a combination of magnesium hydroxide and an inorganic acid and with the combination of an inorganic acid and chelating agent EDTA.
Unbleached kraft needle wood pulp is used as a raw material. The pulp is obtained from the industrial production of softwood kraft pulp mills. It is washed in the factory and then subjected to a bleaching process without further washing in the laboratory. Commercial magnesium hydroxide was diluted to a 1mol/L concentration prior to use and used in these experiments.
In comparative examples 1 and 2, magnesium sulfate and magnesium hydroxide solutions were added to papermaking pulp, respectively. In examples 1 and 2, magnesium hydroxide solution and laboratory grade sulfuric acid were added. In example 3, laboratory grade EDTA (10 g/L) was also loaded. Sulfuric acid and EDTA were first mixed with commercially available magnesium hydroxide. The additive mixtures are shown in Table I. This mixture is then mixed into the pulp. In all examples, the pulp charge was 120g (oven dried). Bleaching was performed in a 2L Teflon lined autoclave placed in a preheated silicone oil bath. The total reaction time was about 2.5 hours in each case.
TABLE I
| Comparative example 1 | Comparative example 2 | Example 1 | Example 2 | Example 3 | |
| MgSO 4 (wt.%) | 0.20 | 0 | - | - | - |
| Mg (OH) 2 (wt.%) | 0 | 0.15 | - | - | - |
| 1:1Mg (OH) 2+H2SO4 (wt%) | 0 | - | 0.15 | - | - |
| 2:1Mg (OH) 2+H2SO4 (wt%) | 0 | - | 0 | 0.15 | 0.15 |
| EDTA (wt.%) | 0 | 0 | 0 | 0 | 0.02 |
Weight% index relative to total dry weight of pulp
Pulp testing was performed according to the usual standard of the German Th unen Institute (Hamburg, germany). Viscosity was measured according to ISO 5351 using copper ethylenediamine (cuen) solution. The results are shown in Table II.
Table II
| Comparative example 1 | Comparative example 2 | Example 1 | Example 2 | Example 3 | |
| Brightness (ISO) | 38.8 | 41.8 | 38.9 | 36.9 | 37.8 |
| Pulp viscosity (mL/g) | 940 | 860 | 920 | 930 | 920 |
| Kappa number | 11.4 | 9.9 | 11.8 | 12.0 | 11.8 |
| Yield rate | 87.43 | 87.44 | 87.36 | 87.34 | 87.26 |
From the data obtained, it can be seen that: (i) The viscosity number of the examples of the present invention was comparable to that of comparative example 1, avoiding the use of magnesium sulfate. At the same time, the viscosity number and the kappa number are improved relative to comparative example 2. Finally, the brightness value, kappa number and overall yield were not adversely affected with respect to comparative example 1.
Example 3 used EDTA in combination with Mg (OH) 2/H2SO4, which did not substantially modify the intended technical properties of the pulp.
In a separate pulp bleaching process using sodium hydroxide and hydrogen peroxide as bleaching agents, gradually increasing amounts of magnesium hydroxide were used instead of sodium hydroxide, and the effect of this on residual peroxide and brightness was determined.
Unbleached kraft needle wood pulp is used as a raw material. The pulp is obtained from the industrial production of softwood kraft pulp mills. It is washed in the factory and then subjected to a bleaching process without further washing in the laboratory. The pH of the water pressed out of the pulp sample used in the laboratory bleaching test was 2.8, so the pulp was significantly acidic. The commercial magnesium hydroxide was diluted to a 1mol/L concentration prior to use and used in these experiments.
The additive ingredients were first mixed together and then this mixture was added to the aqueous pulp to produce the pulp mixtures shown in table III. Bleaching was performed in plastic bags (bags were placed in a preheated water bath at 70 ℃ and the bag was open outside the water to avoid additional water entering the bag during bleaching). The total reaction time in each case was about 2 hours.
Table III
After bleaching for about 2 hours, 1ml of water was pressed out of the pulp and residual peroxide was determined using iodometric titration, well known to the person skilled in the art and described in the literature. In addition, the ISO brightness of the pulp mixture was determined from the dry cake of bleached pulp using a Konica Minolta CM3700d spectrocolorimeter according to ISO 2469 (R457). The results are shown in Table IV. Chemical Oxygen Demand (COD) was determined from water pressed from bleached pulp using HACH LANGE cuvette test LCK 614.
Table IV
It was found that when using an acidic pulp mixture, magnesium hydroxide could be used instead of sodium hydroxide during bleaching. Even at lower substitution rates of Mg (OH) 2 for NaOH, a significant COD value drop was observed. This is advantageous for pulp yield, since the COD produced per kg is the lost pulp yield. It also has a positive effect on the COD of the wastewater, so it provides an improved environmental impact.
In another pulp bleaching process using sodium hydroxide and hydrogen peroxide as bleaching agents, the effect of adding magnesium hydroxide to the pulp prior to sodium hydroxide and any other alkaline additives was measured.
Unbleached kraft needle wood pulp is used as a raw material. The pulp is obtained from the industrial production of softwood kraft pulp mills. It is washed in the factory and then subjected to a bleaching process without further washing in the laboratory. The pH of the water pressed out of the pulp sample used in the laboratory bleaching test was 2.8, so the pulp was significantly acidic. Commercial magnesium hydroxide was diluted to a 1mol/L concentration prior to use and used in these experiments.
The pulp mixtures shown in table V were prepared by: the individual additive components are mixed and then this mixture is added to the aqueous pulp, or in the case of magnesium hydroxide being added to the pulp before, magnesium hydroxide is added to the aqueous pulp, the pulp mixture is manually mixed for about 1 minute, and then the remaining additive components are mixed and this mixture is added to the magnesium hydroxide and pulp mixture. Bleaching was performed in plastic bags (bags were placed in a preheated water bath at 70 ℃ and the bag was open outside the water to avoid additional water entering the bag during bleaching). The total reaction time was in each case about 80 minutes.
Table V
After bleaching for about 80 minutes, the residual peroxide and ISO brightness of the pulp mixture were measured as described above. The results are shown in Table VI below.
Table VI
The residual peroxide and ISO brightness of the pulp mixture with magnesium hydroxide added first was found to be superior to the pulp mixture with magnesium hydroxide and other additive components added simultaneously.
In another pulp bleaching process using sodium hydroxide and hydrogen peroxide as bleaching agents, a reduced amount of hydrogen peroxide was used together with magnesium hydroxide and its effect was measured.
Unbleached kraft needle wood pulp is used as a raw material. The pulp is obtained from the industrial production of softwood kraft pulp mills. It is washed in the factory and then subjected to a bleaching process without further washing in the laboratory. The pH of the water pressed out of the pulp sample used in the laboratory bleaching test was 2.8, so the pulp was significantly acidic. Commercial magnesium hydroxide was diluted to a 1mol/L concentration prior to use and used in these experiments.
The pulp mixtures shown in table VII were prepared by: the individual additive components are mixed and then this mixture is added to the aqueous pulp, or in the case of magnesium hydroxide being added to the pulp before, magnesium hydroxide is added to the aqueous pulp, the pulp mixture is manually mixed for about 1 minute, and then the remaining additive components are mixed and this mixture is added to the magnesium hydroxide and pulp mixture. Bleaching was performed in plastic bags (bags were placed in a preheated water bath at 70 ℃ and the bag was open outside the water to avoid additional water entering the bag during bleaching). The total reaction time was in each case about 80 minutes.
Table VII
After bleaching for about 80 minutes, the residual peroxide and ISO brightness of the pulp mixture were measured as described above. The results are shown in Table VIII below.
Table VIII
It was found that when magnesium hydroxide was added first, similar residual peroxide and ISO brightness results were obtained even with a reduced amount of hydrogen peroxide.
It should be noted that the invention may comprise any combination of features and/or limitations mentioned herein, except combinations of features that are mutually exclusive. The foregoing description, for purposes of explanation, was directed to specific embodiments of the present invention. However, those skilled in the art will appreciate that many modifications and variations may be made to the embodiments described herein. All such modifications and variations are intended to be within the scope of the present invention as defined in the appended claims.
Claims (10)
1. A method of pulp bleaching or pulp delignification using hydrogen peroxide as an alkaline bleaching agent, the method comprising:
A composition is formed by a process comprising the steps of: mixing an alkaline earth metal oxide and/or an alkaline earth metal hydroxide with an inorganic acid or sulfur dioxide or carbon dioxide, thereby forming in situ a mixture of the alkaline earth metal oxide and/or alkaline earth metal hydroxide with an alkaline earth metal salt, optionally in the presence of one or more resin control agents, wherein the pH of the resulting composition is from 7 to 10.5;
adding the composition to the pulp to be bleached; and
Hydrogen peroxide and optionally any other alkaline bleach is then added.
2. The method of claim 1, wherein the process of forming the composition is performed in an aqueous pulp bleaching composition.
3. The method of claim 2, wherein the mixing step is performed by adding sulfuric acid or sulfur dioxide or carbon dioxide to a paper bleached pulp comprising the alkaline earth metal oxide and/or the alkaline earth metal hydroxide.
4. A method according to any one of claims 1 to 3, wherein the composition comprises:
(i) One or more alkaline earth metal oxides and/or one or more alkaline earth metal hydroxides;
(ii) One or more alkaline earth metal salts; and
(Iii) Optionally one or more resin control additives.
5. A method according to any one of claims 1 to 3, wherein the resin control additive is selected from talc, bentonite, zeolite, diatomaceous earth, cationic mica, hydrophobic carbonate, resin decomposing enzymes, cationic polymers designed to capture and immobilize resins or resinous components on the surface of the fiber, aluminum sulfate, polyaluminum chloride and dispersants specifically designed to disperse resins and resinous components and mixtures thereof, for example, wherein the resin control additive is selected from micronized talc, bimodal talc and cationic talc, or the resin control additive is bentonite, such as activated bentonite.
6. A method according to any one of claims 1 to 3, wherein the alkaline earth metal is selected from magnesium, calcium and mixtures thereof.
7. The method of claim 1, wherein the composition is an aqueous slurry.
8. The method of claim 7, wherein the total solids content of the aqueous slurry is from 10 wt% to 75 wt%, based on the total weight of the slurry.
9. The method of claim 1, wherein the weight ratio of (i) alkaline earth metal oxide and/or alkaline earth metal hydroxide to (ii) alkaline earth metal salt in the composition is from 1:10 to 100:1.
10. The method of claim 1, wherein the other alkaline bleaching agent is water glass, sodium silicate, and/or NaOH.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP15306543.8 | 2015-09-30 | ||
| EP16305924.9 | 2016-07-18 |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201680037901.5A Division CN107709657A (en) | 2015-09-30 | 2016-09-29 | The method of belaching aqueous paper pulp and the composition for these methods |
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| Publication Number | Publication Date |
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| CN118308895A true CN118308895A (en) | 2024-07-09 |
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