CN116507772A - Method for producing bleached pulp - Google Patents
Method for producing bleached pulp Download PDFInfo
- Publication number
- CN116507772A CN116507772A CN202180075349.XA CN202180075349A CN116507772A CN 116507772 A CN116507772 A CN 116507772A CN 202180075349 A CN202180075349 A CN 202180075349A CN 116507772 A CN116507772 A CN 116507772A
- Authority
- CN
- China
- Prior art keywords
- pulp
- acid
- bleaching
- chlorine dioxide
- bleaching step
- 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
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 56
- 238000004061 bleaching Methods 0.000 claims abstract description 327
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 claims abstract description 320
- 239000004155 Chlorine dioxide Substances 0.000 claims abstract description 160
- 235000019398 chlorine dioxide Nutrition 0.000 claims abstract description 160
- FHHJDRFHHWUPDG-UHFFFAOYSA-N peroxysulfuric acid Chemical compound OOS(O)(=O)=O FHHJDRFHHWUPDG-UHFFFAOYSA-N 0.000 claims abstract description 136
- DAFQZPUISLXFBF-UHFFFAOYSA-N tetraoxathiolane 5,5-dioxide Chemical compound O=S1(=O)OOOO1 DAFQZPUISLXFBF-UHFFFAOYSA-N 0.000 claims abstract description 60
- 239000003513 alkali Substances 0.000 claims abstract description 42
- 238000000034 method Methods 0.000 claims description 106
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 80
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 43
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 39
- 229910052799 carbon Inorganic materials 0.000 claims description 39
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 30
- 238000009897 hydrogen peroxide bleaching Methods 0.000 claims description 20
- 239000003657 drainage water Substances 0.000 claims description 11
- 239000002351 wastewater Substances 0.000 claims description 10
- 238000007430 reference method Methods 0.000 claims description 7
- 238000010306 acid treatment Methods 0.000 claims 1
- 239000002994 raw material Substances 0.000 description 81
- 230000014759 maintenance of location Effects 0.000 description 45
- 239000002253 acid Substances 0.000 description 42
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 36
- 239000013055 pulp slurry Substances 0.000 description 34
- 229920005610 lignin Polymers 0.000 description 27
- 238000010411 cooking Methods 0.000 description 25
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 24
- 239000012286 potassium permanganate Substances 0.000 description 23
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 22
- 229910052760 oxygen Inorganic materials 0.000 description 22
- 239000001301 oxygen Substances 0.000 description 22
- 239000000126 substance Substances 0.000 description 14
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 12
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 12
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 12
- 235000011121 sodium hydroxide Nutrition 0.000 description 12
- 238000001179 sorption measurement Methods 0.000 description 12
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 10
- 238000012360 testing method Methods 0.000 description 10
- 230000015556 catabolic process Effects 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 9
- 238000006731 degradation reaction Methods 0.000 description 9
- 238000002360 preparation method Methods 0.000 description 9
- 239000000654 additive Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 239000002655 kraft paper Substances 0.000 description 7
- 238000010025 steaming Methods 0.000 description 7
- 238000005406 washing Methods 0.000 description 7
- 229920001131 Pulp (paper) Polymers 0.000 description 6
- 239000012978 lignocellulosic material Substances 0.000 description 6
- 238000002156 mixing Methods 0.000 description 6
- 239000002023 wood Substances 0.000 description 6
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 5
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 5
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 5
- 239000004327 boric acid Substances 0.000 description 5
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical compound OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 description 5
- 238000004140 cleaning Methods 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 230000006866 deterioration Effects 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 229910017604 nitric acid Inorganic materials 0.000 description 5
- 239000000123 paper Substances 0.000 description 5
- SMNDYUVBFMFKNZ-UHFFFAOYSA-N 2-furoic acid Chemical compound OC(=O)C1=CC=CO1 SMNDYUVBFMFKNZ-UHFFFAOYSA-N 0.000 description 4
- 229920002488 Hemicellulose Polymers 0.000 description 4
- 230000007062 hydrolysis Effects 0.000 description 4
- 238000006460 hydrolysis reaction Methods 0.000 description 4
- 150000004966 inorganic peroxy acids Chemical class 0.000 description 4
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 4
- 230000000630 rising effect Effects 0.000 description 4
- BZSXEZOLBIJVQK-UHFFFAOYSA-N 2-methylsulfonylbenzoic acid Chemical compound CS(=O)(=O)C1=CC=CC=C1C(O)=O BZSXEZOLBIJVQK-UHFFFAOYSA-N 0.000 description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 238000005903 acid hydrolysis reaction Methods 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
- PYKYMHQGRFAEBM-UHFFFAOYSA-N anthraquinone Natural products CCC(=O)c1c(O)c2C(=O)C3C(C=CC=C3O)C(=O)c2cc1CC(=O)OC PYKYMHQGRFAEBM-UHFFFAOYSA-N 0.000 description 3
- 150000004056 anthraquinones Chemical class 0.000 description 3
- 239000000460 chlorine Substances 0.000 description 3
- 229910052801 chlorine Inorganic materials 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 150000004968 peroxymonosulfuric acids Chemical class 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- ASHGTJPOSUFTGB-UHFFFAOYSA-N 3-methoxyphenol Chemical compound COC1=CC=CC(O)=C1 ASHGTJPOSUFTGB-UHFFFAOYSA-N 0.000 description 2
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 2
- SHNRXUWGUKDPMA-UHFFFAOYSA-N 5-formyl-2-furoic acid Chemical compound OC(=O)C1=CC=C(C=O)O1 SHNRXUWGUKDPMA-UHFFFAOYSA-N 0.000 description 2
- 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 2
- QPCDCPDFJACHGM-UHFFFAOYSA-N N,N-bis{2-[bis(carboxymethyl)amino]ethyl}glycine Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(=O)O)CCN(CC(O)=O)CC(O)=O QPCDCPDFJACHGM-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 2
- 238000002835 absorbance Methods 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 150000001491 aromatic compounds Chemical class 0.000 description 2
- 229920002678 cellulose Polymers 0.000 description 2
- 239000001913 cellulose Substances 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- DUYCTCQXNHFCSJ-UHFFFAOYSA-N dtpmp Chemical compound OP(=O)(O)CN(CP(O)(O)=O)CCN(CP(O)(=O)O)CCN(CP(O)(O)=O)CP(O)(O)=O DUYCTCQXNHFCSJ-UHFFFAOYSA-N 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 235000019253 formic acid Nutrition 0.000 description 2
- LHGVFZTZFXWLCP-UHFFFAOYSA-N guaiacol Chemical compound COC1=CC=CC=C1O LHGVFZTZFXWLCP-UHFFFAOYSA-N 0.000 description 2
- 238000004128 high performance liquid chromatography Methods 0.000 description 2
- 239000012510 hollow fiber Substances 0.000 description 2
- 239000000413 hydrolysate Substances 0.000 description 2
- QWPPOHNGKGFGJK-UHFFFAOYSA-N hypochlorous acid Chemical compound ClO QWPPOHNGKGFGJK-UHFFFAOYSA-N 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- TXXHDPDFNKHHGW-UHFFFAOYSA-N muconic acid Chemical compound OC(=O)C=CC=CC(O)=O TXXHDPDFNKHHGW-UHFFFAOYSA-N 0.000 description 2
- NWVVVBRKAWDGAB-UHFFFAOYSA-N p-methoxyphenol Chemical compound COC1=CC=C(O)C=C1 NWVVVBRKAWDGAB-UHFFFAOYSA-N 0.000 description 2
- 238000010979 pH adjustment Methods 0.000 description 2
- 229960003330 pentetic acid Drugs 0.000 description 2
- -1 polyethylene Polymers 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- 229920005552 sodium lignosulfonate Polymers 0.000 description 2
- HYHCSLBZRBJJCH-UHFFFAOYSA-N sodium polysulfide Chemical compound [Na+].S HYHCSLBZRBJJCH-UHFFFAOYSA-N 0.000 description 2
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 description 2
- 239000003381 stabilizer Substances 0.000 description 2
- JNIQBPHJIAOMQU-FSIIMWSLSA-N (2s,3s,4s,5r)-2,3,4,5-tetrahydroxy-6-oxoheptanoic acid Chemical compound CC(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)C(O)=O JNIQBPHJIAOMQU-FSIIMWSLSA-N 0.000 description 1
- AZQWKYJCGOJGHM-UHFFFAOYSA-N 1,4-benzoquinone Chemical compound O=C1C=CC(=O)C=C1 AZQWKYJCGOJGHM-UHFFFAOYSA-N 0.000 description 1
- XNGBCVRGPNWAGY-UHFFFAOYSA-N 1,4-dihydroanthracene-9,10-diol Chemical compound C1=CC=C2C(O)=C(CC=CC3)C3=C(O)C2=C1 XNGBCVRGPNWAGY-UHFFFAOYSA-N 0.000 description 1
- YGLNXMOCZLUGEO-UHFFFAOYSA-N 2,5-dimethylhexa-2,4-dienoic acid Chemical compound CC(C)=CC=C(C)C(O)=O YGLNXMOCZLUGEO-UHFFFAOYSA-N 0.000 description 1
- BLQFHJKRTDIZLX-UHFFFAOYSA-N 5-amino-2-methoxyphenol Chemical compound COC1=CC=C(N)C=C1O BLQFHJKRTDIZLX-UHFFFAOYSA-N 0.000 description 1
- YYVYAPXYZVYDHN-UHFFFAOYSA-N 9,10-phenanthroquinone Chemical compound C1=CC=C2C(=O)C(=O)C3=CC=CC=C3C2=C1 YYVYAPXYZVYDHN-UHFFFAOYSA-N 0.000 description 1
- 244000283070 Abies balsamea Species 0.000 description 1
- 235000007173 Abies balsamea Nutrition 0.000 description 1
- 241000208140 Acer Species 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- 235000018185 Betula X alpestris Nutrition 0.000 description 1
- 235000018212 Betula X uliginosa Nutrition 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 description 1
- 241001070941 Castanea Species 0.000 description 1
- 235000014036 Castanea Nutrition 0.000 description 1
- 241000218631 Coniferophyta Species 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 244000166124 Eucalyptus globulus Species 0.000 description 1
- 240000000731 Fagus sylvatica Species 0.000 description 1
- 235000010099 Fagus sylvatica Nutrition 0.000 description 1
- 240000000797 Hibiscus cannabinus Species 0.000 description 1
- 240000000249 Morus alba Species 0.000 description 1
- 235000008708 Morus alba Nutrition 0.000 description 1
- TXXHDPDFNKHHGW-CCAGOZQPSA-N Muconic acid Natural products OC(=O)\C=C/C=C\C(O)=O TXXHDPDFNKHHGW-CCAGOZQPSA-N 0.000 description 1
- 229930192627 Naphthoquinone Natural products 0.000 description 1
- 240000002834 Paulownia tomentosa Species 0.000 description 1
- 235000014676 Phragmites communis Nutrition 0.000 description 1
- 235000008331 Pinus X rigitaeda Nutrition 0.000 description 1
- 235000011613 Pinus brutia Nutrition 0.000 description 1
- 241000018646 Pinus brutia Species 0.000 description 1
- 241000183024 Populus tremula Species 0.000 description 1
- 108010009736 Protein Hydrolysates Proteins 0.000 description 1
- 239000004115 Sodium Silicate Substances 0.000 description 1
- YDONNITUKPKTIG-UHFFFAOYSA-N [Nitrilotris(methylene)]trisphosphonic acid Chemical compound OP(O)(=O)CN(CP(O)(O)=O)CP(O)(O)=O YDONNITUKPKTIG-UHFFFAOYSA-N 0.000 description 1
- 125000002777 acetyl group Chemical group [H]C([H])([H])C(*)=O 0.000 description 1
- 238000005273 aeration Methods 0.000 description 1
- RJGDLRCDCYRQOQ-UHFFFAOYSA-N anthrone Chemical compound C1=CC=C2C(=O)C3=CC=CC=C3CC2=C1 RJGDLRCDCYRQOQ-UHFFFAOYSA-N 0.000 description 1
- 239000007844 bleaching agent Substances 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- YALMXYPQBUJUME-UHFFFAOYSA-L calcium chlorate Chemical compound [Ca+2].[O-]Cl(=O)=O.[O-]Cl(=O)=O YALMXYPQBUJUME-UHFFFAOYSA-L 0.000 description 1
- 229920005551 calcium lignosulfonate Polymers 0.000 description 1
- RYAGRZNBULDMBW-UHFFFAOYSA-L calcium;3-(2-hydroxy-3-methoxyphenyl)-2-[2-methoxy-4-(3-sulfonatopropyl)phenoxy]propane-1-sulfonate Chemical compound [Ca+2].COC1=CC=CC(CC(CS([O-])(=O)=O)OC=2C(=CC(CCCS([O-])(=O)=O)=CC=2)OC)=C1O RYAGRZNBULDMBW-UHFFFAOYSA-L 0.000 description 1
- 239000002738 chelating agent Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 230000001335 demethylating effect Effects 0.000 description 1
- 230000029087 digestion Effects 0.000 description 1
- 238000002845 discoloration Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 229960001867 guaiacol Drugs 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- DKPHLYCEFBDQKM-UHFFFAOYSA-H hexapotassium;1-phosphonato-n,n-bis(phosphonatomethyl)methanamine Chemical compound [K+].[K+].[K+].[K+].[K+].[K+].[O-]P([O-])(=O)CN(CP([O-])([O-])=O)CP([O-])([O-])=O DKPHLYCEFBDQKM-UHFFFAOYSA-H 0.000 description 1
- 230000003301 hydrolyzing effect Effects 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
- ZADYMNAVLSWLEQ-UHFFFAOYSA-N magnesium;oxygen(2-);silicon(4+) Chemical compound [O-2].[O-2].[O-2].[Mg+2].[Si+4] ZADYMNAVLSWLEQ-UHFFFAOYSA-N 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 150000002791 naphthoquinones Chemical class 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- MGFYIUFZLHCRTH-UHFFFAOYSA-N nitrilotriacetic acid Chemical compound OC(=O)CN(CC(O)=O)CC(O)=O MGFYIUFZLHCRTH-UHFFFAOYSA-N 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000005077 polysulfide Substances 0.000 description 1
- 229920001021 polysulfide Polymers 0.000 description 1
- 150000008117 polysulfides Polymers 0.000 description 1
- IWZKICVEHNUQTL-UHFFFAOYSA-M potassium hydrogen phthalate Chemical compound [K+].OC(=O)C1=CC=CC=C1C([O-])=O IWZKICVEHNUQTL-UHFFFAOYSA-M 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 229940047670 sodium acrylate Drugs 0.000 description 1
- 235000017557 sodium bicarbonate Nutrition 0.000 description 1
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- UKLNMMHNWFDKNT-UHFFFAOYSA-M sodium chlorite Chemical compound [Na+].[O-]Cl=O UKLNMMHNWFDKNT-UHFFFAOYSA-M 0.000 description 1
- 229960002218 sodium chlorite Drugs 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
- 229910052911 sodium silicate Inorganic materials 0.000 description 1
- 229910052979 sodium sulfide Inorganic materials 0.000 description 1
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 description 1
- 235000010265 sodium sulphite Nutrition 0.000 description 1
- 239000010902 straw Substances 0.000 description 1
Classifications
-
- 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
-
- 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
- D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
- D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone
-
- 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
- D21C9/16—Bleaching ; Apparatus therefor with per compounds
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
Abstract
Provided is a method for producing bleached pulp having excellent whiteness. A method for producing bleached pulp, comprising the steps of: an oxygen-alkali bleaching step of oxygen-alkali bleaching the unbleached pulp; a peroxymonosulfuric acid bleaching step of treating with peroxymonosulfuric acid; and a 1 st chlorine dioxide bleaching step of treating the unbleached pulp with chlorine dioxide, wherein the ratio of the addition rate (mass%) of chlorine dioxide to the absolute dry mass of the unbleached pulp to the addition rate (mass%) of peroxomonosulfuric acid to the absolute dry mass of the unbleached pulp (addition rate of chlorine dioxide/addition rate of peroxomonosulfuric acid) is 0.25 to 4.0.
Description
Technical Field
The present invention relates to a method for producing bleached pulp.
Background
In recent years, bleaching of pulp has been generally performed by chlorine-free (ECF: elemental Chlorine Free) bleaching without using chlorine itself or hypochlorous acid.
For example, patent document 1 describes an invention of a method for producing bleached pulp, which is characterized in that unbleached pulp obtained by steaming lignocellulose material is subjected to oxygen-alkali bleaching, then treated and washed with inorganic peroxyacid and/or a salt thereof without adding a chelating agent, and further subjected to a multistage bleaching treatment from ozone treatment.
Patent document 1 describes the use of chlorine dioxide (ClO) for ECF bleaching 2 ) Light ECF bleaching, which is the main stream and minimizes the amount of chlorine dioxide used, has been attracting attention.
In addition, according to the invention described in patent document 1, it is described that the ozone bleaching is performed after the pretreatment by acid cleaning with an inorganic peroxyacid, so that the reaction selectivity of the ozone bleaching is improved, the reaction efficiency is improved, and the amount of chlorine dioxide used in the subsequent stage can be further reduced.
Patent document 2 describes an invention of a method for producing bleached pulp, which is characterized in that unbleached pulp obtained by steaming lignocellulose material is subjected to oxygen-alkali bleaching, then treated with an inorganic peroxyacid and/or a salt thereof, and further subjected to a multi-stage bleaching treatment starting from chlorine dioxide treatment.
According to the invention described in patent document 2, it is described that when pulp after oxygen-alkali bleaching is subjected to chlorine dioxide bleaching, the pulp is pretreated with an inorganic peroxyacid, whereby delignification and hexenuronic acid removal in the chlorine dioxide stage are promoted.
Prior art literature
Patent literature
Patent document 1: japanese patent laid-open No. 2007-308815
Patent document 2: japanese patent laid-open No. 2007-308824
Disclosure of Invention
Problems to be solved by the invention
Conventionally, in ECF bleaching, bleaching of pulp has been performed by combining various bleaching methods with bleaching with chlorine dioxide as described above, but a method for producing bleached pulp having a further high whiteness is demanded.
Accordingly, the present invention provides a means for producing bleached pulp having excellent whiteness.
Solution for solving the problem
The present inventors have made intensive studies to solve the above problems. The result shows that: the present invention has been completed by combining a bleaching step using peroxomonosulfuric acid and a bleaching step using chlorine dioxide, and setting the ratio of the rate of addition of peroxomonosulfuric acid to the rate of addition of chlorine dioxide in each step to a predetermined range, thereby solving the above-mentioned problems. That is, the present invention is, for example, as follows.
[1] A method for producing bleached pulp, comprising the steps of:
an oxygen-alkali bleaching step of oxygen-alkali bleaching the unbleached pulp;
a peroxymonosulfuric acid bleaching step of treating with peroxymonosulfuric acid; and, a step of, in the first embodiment,
a 1 st chlorine dioxide bleaching step of treating with chlorine dioxide;
the ratio of the addition rate (mass%) of chlorine dioxide to the absolute dry mass of the unbleached pulp to the addition rate (mass%) of peroxomonosulfuric acid to the absolute dry mass of the unbleached pulp (addition rate of chlorine dioxide/addition rate of peroxomonosulfuric acid) is 0.25 to 4.0.
[2] A method for producing bleached pulp, comprising the steps of:
an oxygen-alkali bleaching step of oxygen-alkali bleaching the unbleached pulp;
a peroxymonosulfuric acid bleaching step of treating with peroxymonosulfuric acid; and, a step of, in the first embodiment,
a 1 st chlorine dioxide bleaching step of treating with chlorine dioxide;
the ratio of the addition rate (mass%) of chlorine dioxide to the absolute dry mass of the unbleached pulp to the addition rate (mass%) of peroxomonosulfuric acid to the absolute dry mass of the unbleached pulp (addition rate of chlorine dioxide/addition rate of peroxomonosulfuric acid) is 0.25 to 2.0,
the treatment temperature of the peroxymonosulfuric acid bleaching step is 70-98 ℃.
[3] The production method according to the above [2], which further comprises an alkaline hydrogen peroxide bleaching step of treating with alkaline hydrogen peroxide.
[4] The production method according to the above [2] or [3], which further comprises an ozone bleaching step of treating with ozone.
[5] A method for producing bleached pulp, comprising the following steps in order:
an oxygen-alkali bleaching step of oxygen-alkali bleaching the unbleached pulp;
a peroxymonosulfuric acid bleaching step of treating with peroxymonosulfuric acid;
a 1 st chlorine dioxide bleaching step of treating with chlorine dioxide;
an alkaline hydrogen peroxide bleaching step of treating with alkaline hydrogen peroxide; and, a step of, in the first embodiment,
A 2 nd chlorine dioxide bleaching process, which is to treat with chlorine dioxide,
the ratio of the addition rate (mass%) of chlorine dioxide to the absolute dry mass of the unbleached pulp in the 1 st chlorine dioxide bleaching step to the addition rate (mass%) of peroxomonosulfuric acid to the absolute dry mass of the unbleached pulp (addition rate of chlorine dioxide/addition rate of peroxomonosulfuric acid) is 0.25 to 2.0,
the treatment temperature of the peroxymonosulfuric acid bleaching step is 70-98 ℃.
[6] A method for producing bleached pulp, comprising the steps of:
an oxygen-alkali bleaching step of oxygen-alkali bleaching the unbleached pulp;
a peroxymonosulfuric acid bleaching step of treating with peroxymonosulfuric acid; and, a step of, in the first embodiment,
a 1 st chlorine dioxide bleaching process, which uses chlorine dioxide to process,
the addition rate (mass%) of the peroxymonosulfuric acid to the absolute dry mass of the unbleached pulp is 0.30 to 1.75 mass%,
the ratio of the addition rate (mass%) of chlorine dioxide to the absolute dry mass of the unbleached pulp to the addition rate (mass%) of peroxomonosulfuric acid to the absolute dry mass of the unbleached pulp (addition rate of chlorine dioxide/addition rate of peroxomonosulfuric acid) is 0.5 to 2.0.
[7] The production method according to the above [6], which further comprises an alkaline hydrogen peroxide bleaching step of treating with alkaline hydrogen peroxide.
[8] The production method according to the above [6] or [7], which further comprises an ozone bleaching step of treating with ozone.
[9] The production method according to any one of the above [6] to [8], wherein the treatment temperature in the peroxymonosulfuric acid bleaching step is 40 to 98 ℃.
[10]According to [1] above]～[9]The process according to any one of the preceding claims, wherein the Total Organic Carbon (TOC) of the effluent obtained in the peroxymonosulfuric acid bleaching step and the 1 st chlorine dioxide bleaching step 1 ) Total Organic Carbon (TOC) of the effluent obtained in the sulfuric acid bleaching step and the 1 st chlorine dioxide bleaching step in the reference method in which the sulfuric acid bleaching step treated with sulfuric acid is performed instead of the peroxymonosulfuric acid bleaching step 2 ) Is a TOC increase rate (TOC) 1 /TOC 2 X 100) exceeds 100%.
[11] The manufacturing method according to the above [10], further comprising the operations of: at least a part of the drainage water obtained in the peroxymonosulfuric acid bleaching step and the drainage water obtained in the 1 st chlorine dioxide bleaching step is reused in the peroxymonosulfuric acid bleaching step.
[12] The production method according to any one of the above [1] to [11], wherein the treatment time in the peroxymonosulfuric acid bleaching step is 2 to 200 minutes.
[13] The production method according to any one of the above [1] to [12], wherein the treatment pH in the peroxymonosulfuric acid bleaching step is 2 to 5.
In addition, the present invention may include, for example, the following modes.
[1' ] A method for producing bleached pulp, comprising the steps of:
an oxygen-alkali bleaching step of oxygen-alkali bleaching the unbleached pulp;
a peroxymonosulfuric acid bleaching step of treating with peroxymonosulfuric acid; and, a step of, in the first embodiment,
a 1 st chlorine dioxide bleaching process, which uses chlorine dioxide to process,
the ratio of the addition rate (mass%) of chlorine dioxide to the absolute dry mass of the unbleached pulp to the addition rate (mass%) of peroxomonosulfuric acid to the absolute dry mass of the unbleached pulp (addition rate of chlorine dioxide/addition rate of peroxomonosulfuric acid) is 0.25 to 4.0.
[2’]According to [1 ]']The method for producing a waste water having a Total Organic Carbon (TOC) obtained in the peroxymonosulfuric acid bleaching step and the 1 st chlorine dioxide bleaching step 1 ) Total Organic Carbon (TOC) of the effluent obtained in the sulfuric acid bleaching step and the 1 st chlorine dioxide bleaching step in the reference method in which the sulfuric acid bleaching step treated with sulfuric acid is performed instead of the peroxymonosulfuric acid bleaching step is used 2 ) Is a TOC increase rate (TOC) 1 /TOC 2 X 100) exceeds 100%.
[3'] the production method according to the above [2' ], further comprising the operations of: at least a part of the drainage water obtained in the peroxymonosulfuric acid bleaching step and the drainage water obtained in the 1 st chlorine dioxide bleaching step is reused in the peroxymonosulfuric acid bleaching step.
[4' ] the production method according to any one of the above [1' ] to [3' ], wherein the treatment time of the peroxymonosulfuric acid bleaching step is 2 to 200 minutes.
[5' ] the production method according to any one of the above [1' ] to [4' ], wherein the treatment temperature in the peroxymonosulfuric acid bleaching step is 40 to 98 ℃.
The process according to any one of [6'] to [5' ] above, wherein the treatment pH in the peroxymonosulfuric acid bleaching step is 2 to 5.
The production method according to any one of [7'] to [6' ] above, further comprising an alkaline hydrogen peroxide bleaching step of treating with alkaline hydrogen peroxide.
The method according to any one of [8'] to [7' ] above, further comprising an ozone bleaching step of treating with ozone.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, a method for producing bleached pulp excellent in whiteness is provided.
Detailed Description
Hereinafter, modes for carrying out the present invention will be described in detail.
Method for producing bleached pulp
The method for producing bleached pulp of the present invention comprises the steps of: an oxygen-alkali bleaching step of oxygen-alkali bleaching the unbleached pulp; a peroxymonosulfuric acid bleaching step of treating with peroxymonosulfuric acid; and, a 1 st chlorine dioxide bleaching step of treating with chlorine dioxide. At this time, the ratio of the addition rate (mass%) of chlorine dioxide to the absolute dry mass of the unbleached pulp to the addition rate (mass%) of peroxomonosulfuric acid to the absolute dry mass of the unbleached pulp (addition rate of chlorine dioxide/addition rate of peroxomonosulfuric acid) is 0.25 to 4.0.
The method for producing bleached pulp may further include the steps of: an unbleached pulp preparation step, an alkaline hydrogen peroxide bleaching step in which an alkaline hydrogen peroxide is used for treatment, and an ozone bleaching step in which an ozone is used for treatment. In this case, each step may be repeated 2 or more times. For example, when the chlorine dioxide bleaching step is performed 2 times, the 1 st chlorine dioxide bleaching step and the 2 nd chlorine dioxide bleaching step may be included.
In one embodiment, the method for producing bleached pulp comprises the following steps in order: an unbleached pulp preparation process, an oxygen-alkali bleaching process (O process), a peroxymonosulfuric acid bleaching process (MPS process), an ozone bleaching process (Z process), a chlorine dioxide bleaching process (D process), and an alkaline hydrogen peroxide bleaching process (Ep process). Hereinafter, each step will be described.
[ Process for producing unbleached pulp ]
The unbleached pulp preparation process is a process for preparing unbleached pulp mainly from lignocellulosic material.
(lignocellulosic matter)
Examples of the lignocellulosic material include wood, non-wood, and old paper.
The wood is not particularly limited, and examples thereof include broad-leaved trees such as eucalyptus, locust, aspen, beech, maple, chestnut, paulownia, birch, elm, etc.; conifers such as fir, pine, fir, hinoki, hemlock, etc.
The non-wood material is not particularly limited, and examples thereof include straw, reed, mulberry, kenaf, orange, and the like.
Of these, the lignocellulose substance is preferably wood, old paper, more preferably wood, and further preferably broad-leaved tree.
The above-mentioned lignocellulose substances may be used alone or in combination of 2 or more.
(preparation of unbleached pulp)
The unbleached pulp is produced by separating (digesting) at least a part of lignin from a lignocellulosic material comprising cellulose forming a skeleton of the lignocellulosic material, hemicellulose as a crosslinking component and lignin as a binding component. That is, in one embodiment, the unbleached pulp preparation process includes a process of cooking lignocellulosic material. The unbleached pulp obtained after the digestion is suitably washed.
The cooking method is not particularly limited, and caustic soda cooking, kraft cooking, and sulfite cooking may be mentioned.
The caustic soda cooking is a cooking method using sodium hydroxide and sodium carbonate.
The kraft cooking is a cooking method using sodium hydroxide and sodium sulfide and/or sodium polysulfide. The unbleached pulp obtained by kraft cooking is generally referred to as Kraft Pulp (KP).
The sulfite cooking is a cooking method using sulfurous acid or a salt thereof. As the sulfite cooking, na is used 2 SO 3 Is cooked with alkaline sulfite; using Na 2 SO 3 And NaHSO 3 Is cooked with neutral sulfite; using NaHSO 3 Or Mg%HSO 3 ) 2 Is a slightly acidic sulfite process; using NaHSO 3 And SO 2 、Mg(HSO 3 ) 2 And SO 2 Or Ca (HSO) 3 ) 2 And SO 2 Is an acidic sulfite process; sodium polysulfide (Na 2 S x ) And the like. The unbleached pulp obtained by sulfite cooking is generally referred to as Sulfite Pulp (SP).
In the above-described cooking, a cooking aid may be used. The cooking aid is not particularly limited, and examples thereof include benzoquinone, naphthoquinone, anthraquinone, anthrone, phenanthrenequinone, and the like. Specific examples of the boiling aid include Anthraquinone (AQ) and 1, 4-dihydro-9, 10-dihydroxyanthracene (DDA). These cooking aids may be used alone or in combination of 2 or more.
Among these, kraft cooking and sulfite cooking are preferable, and kraft cooking and polysulfide cooking are more preferable, from the viewpoints of pulp quality, energy efficiency, and the like. The above-mentioned steaming method may be carried out alone or in combination of 2 or more.
In the preparation of unbleached pulp, hydrolysis may be performed for the purpose of further removing at least a portion of hemicellulose of lignocellulosic material. The hydrolysis is usually carried out before cooking. That is, in one embodiment, the unbleached pulp preparation process includes the steps of: a step of hydrolyzing a lignocellulose substance to obtain a hydrolysate, and a step of cooking the hydrolysate. The hydrolysate and/or the unbleached pulp obtained after the steaming is suitably washed.
The method of hydrolysis is not particularly limited, and examples thereof include a method of adding water to a lignocellulose substance and heating the lignocellulose substance. Thus, acetyl groups are separated from hemicellulose to generate acetic acid, and the liquid becomes acidic to undergo acid hydrolysis. For the purpose of promoting hydrolysis, an acid may be added.
(unbleached pulp)
The whiteness of the unbleached pulp is preferably 30 to 60%, more preferably 40 to 55%. Unbleached pulpIf the whiteness of (2) is 30% or more, the cost of the bleaching treatment can be reduced, so that it is preferable. If the whiteness of the unbleached pulp is 60% or less, the cost of steaming can be reduced, so that it is preferable. In the present specification, the whiteness of unbleached pulp was measured by the following method. That is, according to ISO3688:1977, the mass per unit area was 400g/m 2 Is a sheet of 2 sheets. Using the resulting sheet, according to JISP8148:2001 to determine the whiteness (%) of the pulp.
The potassium permanganate number (K value) of the unbleached pulp is preferably 5 to 10, more preferably 6 to 9. If the K value of the unbleached pulp is 5 or more, the cost of steaming can be reduced, so that it is preferable. If the K value of the unbleached pulp is 10 or less, the amount of chlorine dioxide used and the cost of bleaching can be reduced, which is preferable. In the present specification, the K value of unbleached pulp was measured by the following method. Namely, according to TAPPI UM 253:2010, the K value of the unbleached pulp is determined.
Further, the viscosity of the unbleached pulp is preferably 15cP or more, more preferably 17cP or more, and still more preferably 20cP or more. If the viscosity of the unbleached pulp is 15cP or more, the degree of drainage can be maintained, so that it is preferable. The upper limit of the viscosity of the unbleached pulp is not particularly limited, but is preferably 25cP or less. If the viscosity of the unbleached pulp is 25cP or less, the viscosity of the paper can be maintained, so that it is preferable. In the present specification, the viscosity of unbleached pulp was measured by the following method. That is, the viscosity of unbleached pulp was determined according to J.TAPPI No.44 method.
In addition, the hexenuronic acid content (HexA content) of the unbleached pulp is preferably 25 to 50. Mu. Mol/g, more preferably 30 to 40. Mu. Mol/g. If the HexA content of the unbleached pulp is 25. Mu. Mol/g or more, the cost of steaming can be reduced, so that it is preferable. If the HexA content of the unbleached pulp is 50. Mu. Mol/g or less, the cost of the bleaching treatment can be reduced, so that it is preferable. In the present specification, the HexA content of unbleached pulp was measured according to the following method. Specifically, after the unbleached pulp was oven-dried, 0.8g of bleached pulp in oven-dried mass was precisely weighed and placed in a pressure vessel. Next, 80mL of pure water was added thereto, and then formic acid was added thereto to adjust the pH to 3. The pressure vessel was placed in an oven and treated at 120℃for 4 hours to effect acid hydrolysis of HexA. After the treatment, filtration was performed, and 2-furoic acid and 5-carboxy-2-furaldehyde, which are acid hydrolysates of HexA present in the filtered solution, were quantified by HPLC, and the original HexA content was calculated from the total of their molar amounts.
[ oxygen alkali bleaching Process (O Process) ]
The oxygen-alkali bleaching step is a step of removing lignin and the like contained in pulp by oxygen bleaching under alkaline conditions. The oxygen-alkali bleaching step is usually performed by adding oxygen to a pulp slurry containing alkaline pulp and performing bleaching treatment. The pulp obtained after the bleaching treatment is suitably washed.
(pulp slurry)
The pulp slurry comprises pulp and water.
(pulp)
The pulp is not particularly limited, and may be unbleached pulp or pulp subjected to other bleaching steps, but unbleached pulp is preferable.
The pulp concentration is preferably 8 to 40 mass%, more preferably 10 to 35 mass% with respect to the total mass of the pulp slurry.
In addition, the pH of the pulp slurry is alkaline. Specifically, the pH of the pulp slurry is preferably 8 to 14, more preferably 10 to 14.
In the adjustment of the pH of the pulp slurry, an alkali such as sodium hydroxide (caustic soda) or potassium hydroxide may be used; acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, and carbonic acid; oxidized kraft white liquor, and the like.
(bleaching treatment)
The method of the bleaching treatment is not particularly limited, and examples thereof include a medium consistency method (pulp consistency: 8 to 25 mass%, preferably 10 to 15 mass%) and a high consistency method (pulp consistency: 25 to 40 mass%). Among them, the medium concentration method is preferable.
The addition rate of oxygen is preferably 0.5 to 3 mass% relative to the absolute dry mass of unbleached pulp.
In this case, the oxygen to be used is not particularly limited, and examples thereof include oxygen obtained by a cryogenic separation method, oxygen obtained by pressure swing adsorption (PSA: pressure Swing Adsorption), and oxygen obtained by vacuum pressure swing adsorption (VSA: vacuum Swing Adsorption).
The mixing method is not particularly limited, and a high shear mixer is preferably used. Specifically, kamyr system, sunds-defiberizer system, rauma-Repola system, impcpo system, and the like can be mentioned.
The treatment temperature in the oxygen-alkali bleaching step is preferably 80 to 120 ℃.
The treatment time in the oxygen-alkali bleaching step is preferably 15 to 100 minutes.
[ Persulfuric acid bleaching Process (MPS Process) ]
The peroxymonosulfuric acid bleaching step is a step of removing hexenuronic acid (HexA) and the like contained in pulp by using peroxymonosulfuric acid (MPS). Hexenuronic acid (HexA) is a substance produced by demethylating methylglucuronic acid in the polyxylose side chains of hemicellulose during the cooking process. The content of hexenuronic acid (HexA) in the bleached pulp is correlated with the discoloration of the bleached pulp.
The peroxymonosulfuric acid bleaching step (MPS step) is usually performed by adding peroxymonosulfuric acid (MPS) to a pulp slurry and performing a bleaching treatment. The pulp obtained after the bleaching treatment is suitably washed.
(pulp slurry)
The pulp slurry comprises pulp and water. In addition, additives may be included.
(pulp)
The pulp is not particularly limited, and may be unbleached pulp or pulp subjected to other bleaching steps, but unbleached pulp or pulp subjected to an oxygen-alkali bleaching step is preferable.
The pulp concentration is preferably 5 to 30 mass% with respect to the total mass of the pulp slurry, and more preferably 8 to 15 mass% from the viewpoint of operability.
Additive agent
Examples of the additive include lignin and bleaching-derived substances.
The bleaching source is not particularly limited, and lignin derivatives, 2-methoxyphenol, 3-methoxyphenol, 4-methoxyphenol, 5-amino-methoxyphenol, muconic acid, 2, 5-dimethyl-2, 4-hexadienoic acid, and oxides thereof may be mentioned.
The lignin derivative is not particularly limited, and examples thereof include calcium lignosulfonate, sodium lignosulfonate, lignin sulfonic acid, sodium lignosulfonate acetate, and lignin, which is an organic solvent.
By adding lignin and a bleaching source substance, the removal ability of hexenuronic acid (HexA) based on peroxomonosulfuric acid (MPS) can be improved.
The lignin and the bleaching-derived substance may be prepared separately or prepared as additives, but the drainage obtained in the bleaching step of the method for producing bleached pulp may be used. In each bleaching step of the method for producing bleached pulp, lignin and substances derived from bleaching are removed from the pulp, and therefore lignin and substances derived from bleaching may be contained in the resulting drainage.
The drainage water containing lignin and a bleaching source is not particularly limited, and examples thereof include an unbleached pulp preparation step, an oxygen-alkali bleaching step (O step), a peroxymonosulfuric acid bleaching step (MPS step), an ozone bleaching step (Z step), a chlorine dioxide bleaching step (D step), and an alkaline hydrogen peroxide bleaching step (Ep step). The "drainage" is usually derived from the washing liquid of the pulp after the bleaching treatment. Among these, the drainage of the peroxymonosulfuric acid bleaching step (MPS step) and the chlorine dioxide bleaching step (D step) is preferably reused, and the drainage of the peroxymonosulfuric acid bleaching step (MPS step) and the 1 st chlorine dioxide bleaching step (D step) is more preferably reused. That is, in a preferred embodiment, the peroxymonosulfuric acid bleaching step (MPS step) includes: at least a part of the drainage water obtained in the peroxymonosulfuric acid bleaching step and the drainage water obtained in the 1 st chlorine dioxide bleaching step is reused in the peroxymonosulfuric acid bleaching step.
The Total Organic Carbon (TOC) of the discharged water is preferably 50mg/L or more, more preferably 500mg/L or more, and still more preferably 95 to 300mg/L. The Total Organic Carbon (TOC) contains lignin and a bleaching source substance. The Total Organic Carbon (TOC) concentration in the wastewater was measured by the same method as described in the examples.
In the present invention, bleached pulp having excellent whiteness can be produced. In other words, since the waste water obtained in the bleaching step of the present invention contains a large amount of lignin and a substance originating from bleaching, the concentration of total organic carbon increases. Further, by reusing the above-mentioned drain water in the peroxysulfuric acid bleaching step, hexA can be removed at low cost and with high efficiency.
The pH of the pulp slurry is preferably 1 to 6, more preferably 2 to 5. That is, in one embodiment, the treatment pH in the peroxymonosulfuric acid bleaching step is preferably 1 to 6, more preferably 2 to 5. If the treatment pH is within the above range, hexA can be suitably removed, so that it is preferable.
For the purpose of adjusting the pH of the pulp slurry, an acid may be added. Among them, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, carbonic acid, and the like can be cited as acids. Among these, sulfuric acid is preferable as the acid used for pH adjustment. The acid used for the pH adjustment may be used alone or in combination of 2 or more.
(bleaching treatment)
The bleaching treatment is preferably performed by adding and mixing peroxomonosulfuric acid (MPS) to the pulp slurry.
Per-sulfuric acid (MPS), also known as peroxomonosulfuric acid, is prepared with H 2 SO 5 And (3) representing.
The amount of the peroxomonosulfuric acid (MPS) to be added is preferably 0.01 to 5% by mass, more preferably 0.05 to 3% by mass, still more preferably 0.10 to 2% by mass, particularly preferably 0.15 to 1.75% by mass, most preferably 0.30 to 1.75% by mass, based on the absolute dry mass of the unbleached pulp
In one embodiment, the amount of the peroxymonosulfuric acid (MPS) to be added is preferably 0.15 to 1.75 mass%, more preferably 0.22 to 1.0 mass%, still more preferably 0.22 to 0.75 mass%, and particularly preferably 0.3 to 0.5 mass% relative to the absolute dry mass of the unbleached pulp. If the amount of peroxomonosulfuric acid (MPS) added is within the above range, lignin and/or hexenuronic acid (HexA) can be suitably removed from unbleached pulp, for example. As a result, the whiteness of the obtained bleached pulp is increased, the K value residual ratio is decreased, and the HexA content residual ratio is reduced. In addition, a decrease in viscosity can be prevented or suppressed. When the ratio of the addition rate (mass%) of chlorine dioxide to the absolute dry mass of unbleached pulp to the addition rate (mass%) of peroxymonosulfuric acid to the absolute dry mass of unbleached pulp (addition rate of chlorine dioxide/addition rate of peroxymonosulfuric acid) falls within a predetermined range, the addition amount of peroxymonosulfuric acid (MPS) becomes a predetermined value in the chlorine dioxide bleaching step (step D) described later. That is, if the above-mentioned addition ratio falls within a predetermined range, both the bleaching effect in the peroxymonosulfuric acid bleaching step (MPS step) and the bleaching effect in the chlorine dioxide bleaching step (D step) can be obtained effectively.
The peroxymonosulfuric acid (MPS) may be produced by a known method. Specific examples of the method for producing peroxomonosulfuric acid (MPS) include the following methods: sulfuric acid was added dropwise to the aqueous hydrogen peroxide solution and mixed. In this case, the concentration of the aqueous hydrogen peroxide solution is preferably 20 to 70% by mass, more preferably 35 to 70% by mass. The concentration of the sulfuric acid is preferably 80 to 98% by mass, more preferably 93 to 98% by mass. The mixing molar ratio of sulfuric acid to hydrogen peroxide is preferably 1:1 to 5: 1. more preferably 2:1 to 4:1.
the treatment temperature in the peroxymonosulfuric acid bleaching step is preferably 40 to 110 ℃, more preferably 40 to 105 ℃, still more preferably 40 to 98 ℃, and particularly preferably 70 to 98 ℃.
In one embodiment, the treatment temperature in the peroxymonosulfuric acid bleaching step is preferably 40 to 98 ℃, more preferably 55 to 98 ℃, still more preferably 65 to 98 ℃, and particularly preferably 80 to 98 ℃. When the treatment temperature in the peroxymonosulfuric acid bleaching step is within the above range, for example, the K value residual ratio of the obtained bleached pulp can be reduced, and the HexA content residual ratio can be reduced. In addition, deterioration of the obtained bleached pulp, for example, a decrease in whiteness, a decrease in viscosity may become less likely to occur.
The treatment time in the peroxymonosulfuric acid bleaching step is preferably 2 to 200 minutes, more preferably 5 to 180 minutes, still more preferably 10 to 170 minutes, particularly preferably 70 to 160 minutes, and most preferably 100 to 150 minutes.
In one embodiment, the treatment time of the peroxymonosulfuric acid bleaching step is preferably 30 to 180 minutes, more preferably 40 to 160 minutes, still more preferably 60 to 150 minutes, particularly preferably 80 to 140 minutes, and most preferably 100 to 130 minutes.
In another embodiment, the treatment time of the peroxymonosulfuric acid bleaching step is preferably 30 to 120 minutes, more preferably 60 to 120 minutes, and even more preferably 90 to 120 minutes from the viewpoint of productivity.
[ ozone bleaching Process (Z Process) ]
The ozone bleaching step is a step of removing lignin and the like contained in pulp by ozone. The ozone bleaching process is generally performed by adding ozone to a pulp slurry containing pulp and performing a bleaching treatment. In one embodiment, the method for producing bleached pulp preferably further comprises an ozone bleaching step of treating the bleached pulp with ozone. The pulp obtained after the bleaching treatment is suitably washed.
(pulp slurry)
The pulp slurry comprises pulp and water.
(pulp)
The pulp is usually pulp subjected to other bleaching steps, and preferably pulp subjected to at least an oxygen-alkali bleaching step and a peroxymonosulfuric acid bleaching step.
The pulp concentration is preferably 8 to 40 mass%, more preferably 10 to 35 mass% with respect to the total mass of the pulp slurry.
The pH of the pulp slurry is preferably 1 to 6, more preferably 1 to 5, and still more preferably 1 to 3.
In addition, an alkali such as sodium hydroxide (caustic soda) or potassium hydroxide may be used for adjusting the pH of the pulp slurry; sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, carbonic acid, and the like.
(bleaching treatment)
The method of the bleaching treatment is not particularly limited, and examples thereof include a medium consistency method (pulp consistency: 8 to 25 mass%, preferably 10 to 15 mass%) and a high consistency method (pulp consistency: 25 to 40 mass%). Among them, the medium concentration method is preferable.
Ozone is preferably produced at the time of use because of its short life. The method for producing ozone is not particularly limited, and is preferably a method of producing oxygen by corona discharge.
Examples of the oxygen used in this case include liquid oxygen, oxygen obtained by a cryogenic separation method, oxygen obtained by pressure swing adsorption (PSA: pressure Swing Adsorption), and oxygen obtained by vacuum pressure swing adsorption (VSA: vacuum Swing Adsorption).
The addition rate of ozone is preferably 0.05 to 20% by mass, more preferably 0.1 to 15% by mass, still more preferably 0.1 to 10% by mass, and particularly preferably 0.1 to 1% by mass, based on the absolute dry mass of the unbleached pulp.
The treatment temperature in the ozone bleaching step is preferably 0 to 100 ℃, more preferably 10 to 80 ℃, still more preferably 30 to 80 ℃, and particularly preferably 50 to 80 ℃.
The treatment time in the ozone bleaching step is preferably 5 seconds to 60 minutes, more preferably 10 seconds to 10 minutes.
[ chlorine dioxide bleaching Process (D Process) ]
The chlorine dioxide bleaching step is a step of removing lignin and the like contained in pulp by chlorine dioxide. ECF bleaching can be achieved by using chlorine dioxide instead of chlorine itself, hypochlorous acid. In addition, by appropriately combining other bleaching steps, the amount of chlorine dioxide used in the chlorine dioxide bleaching step can be reduced, and light ECF bleaching can be achieved. Here, in the present specification, the "1 st chlorine dioxide bleaching step" means a chlorine dioxide bleaching step which is performed first in the bleaching step (bleaching sequence).
The chlorine dioxide bleaching process is generally performed by adding chlorine dioxide to a pulp slurry containing pulp and performing a bleaching treatment. The pulp obtained after the bleaching treatment is suitably washed.
(pulp slurry)
The pulp slurry comprises pulp and water.
(pulp)
The pulp is usually pulp subjected to other bleaching steps, and preferably pulp subjected to at least an oxygen-alkali bleaching step and a peroxymonosulfuric acid bleaching step.
The pulp concentration is preferably 5 to 30 mass% with respect to the total mass of the pulp slurry, and more preferably 8 to 15 mass% from the viewpoint of operability.
The pH of the pulp slurry is preferably 1.5 to 6, more preferably 2 to 6 in terms of suppressing decomposition of cellulose, and even more preferably 3 to 5 in terms of improving decomposition of hexenuronic acid.
In addition, an alkali such as sodium hydroxide (caustic soda) or potassium hydroxide may be used for adjusting the pH of the pulp slurry; sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, carbonic acid, and the like.
(bleaching treatment)
The bleaching treatment is preferably performed by adding chlorine dioxide to the pulp slurry and mixing.
The amount of chlorine dioxide to be added is preferably 0.01 to 2.0% by mass, more preferably 0.05 to 1.5% by mass, still more preferably 0.1 to 1.0% by mass, and particularly preferably 0.1 to 0.8% by mass, based on the absolute dry mass of the unbleached pulp.
In one embodiment, the amount of chlorine dioxide to be added is preferably 0.1 to 2.0 mass%, more preferably 0.1 to 1.0 mass%, still more preferably 0.2 to 0.8 mass%, and particularly preferably 0.3 to 0.7 mass% relative to the absolute dry mass of the unbleached pulp.
In addition, in relation to the previously performed peroxymonosulfuric acid bleaching step, a bleached pulp excellent in whiteness can be produced by setting the ratio of the addition rate of peroxymonosulfuric acid to the addition rate of chlorine dioxide to a predetermined range. Specifically, the ratio (addition ratio) of the addition ratio (mass%) of chlorine dioxide represented by the following formula to the absolute dry mass of the unbleached pulp to the addition ratio (mass%) of peroxomonosulfuric acid to the absolute dry mass of the unbleached pulp is 0.25 to 4.0, preferably 0.25 to 3.5, more preferably 0.25 to 4.0, and even more preferably 0.5 to 4.0. In the case where the method for producing bleached pulp includes 2 or more chlorine dioxide bleaching steps (step D), the addition rate of chlorine dioxide is the addition rate of chlorine dioxide in the first chlorine dioxide bleaching step (step D).
[ mathematics 1]
If the ratio of the above-mentioned addition ratio is in the range of 0.25 or less, lignin is polymerized again in the peroxymonosulfuric acid bleaching step, and the addition ratio of chlorine dioxide in the subsequent chlorine dioxide bleaching step increases. If the ratio of the above-mentioned addition is in the range of 4.0 or more, the peroxymonosulfuric acid is insufficient, and therefore, sufficient bleaching cannot be performed in the peroxymonosulfuric acid bleaching step. As a result, bleached pulp having a whiteness degree superior to that of the bleached pulp can be produced at the aforementioned addition ratio. In addition, the HexA content can be reduced, and bleached pulp which is not easy to fade can be manufactured.
In one embodiment, the ratio of the addition rate is preferably 0.3 to 3.0, more preferably 0.5 to 2.3, still more preferably 0.5 to 1.8, particularly preferably 0.9 to 1.8, and most preferably 1.0 to 1.5. If the ratio of the above-mentioned addition ratio is within the above-mentioned range, the bleaching balance of the peroxymonosulfuric acid bleaching step and the chlorine dioxide bleaching step becomes appropriate, and lignin and/or hexenuronic acid (HexA) can be suitably removed from unbleached pulp, for example. As a result, the whiteness of the obtained bleached pulp is increased, the K value residual ratio is decreased, and the HexA content residual ratio is reduced. In addition, a decrease in viscosity can be prevented or suppressed.
In another embodiment, the addition ratio is preferably 0.25 to 2.0, more preferably 0.25 to 1.5, still more preferably 0.25 to 1.0, particularly preferably 0.25 to 0.5, and most preferably 0.25 to 0.3. If the addition ratio is within the above range, the bleaching balance of the peroxymonosulfuric acid bleaching step and the chlorine dioxide bleaching step becomes appropriate, and for example, bleached pulp becomes less likely to deteriorate, which is preferable. Specifically, the whiteness of the bleached pulp is preferably not easily deteriorated, and the viscosity is hardly lowered due to the deterioration.
The chlorine dioxide may be prepared, for example, by the following method: a method of reacting sodium sulfite with sulfur dioxide, a method of reacting sodium chlorite with sulfuric acid, a method of reacting calcium chlorate with hydrochloric acid, a method of reacting sodium chlorate with sodium chloride with sulfuric acid, a method of reacting sodium chlorate with methanol with sulfuric acid, etc., a method of reacting sodium chlorate with hydrogen peroxide with sulfuric acid, etc.
The treatment temperature in the chlorine dioxide bleaching step is preferably 20 to 100 ℃, more preferably 40 to 90 ℃.
In one embodiment, the treatment temperature in the chlorine dioxide bleaching step is preferably 30 to 90 ℃, more preferably 40 to 90 ℃, particularly preferably 50 to 80 ℃, and most preferably 65 to 75 ℃.
The treatment time in the chlorine dioxide bleaching step is preferably 1 minute to 5 hours, more preferably 10 to 180 minutes, still more preferably 20 to 150 minutes, particularly preferably 20 to 120 minutes, and most preferably 50 to 130 minutes.
In one embodiment, the treatment time of the chlorine dioxide bleaching step is preferably 10 to 150 minutes, more preferably 10 to 130 minutes, still more preferably 15 to 100 minutes, particularly preferably 20 to 80 minutes, and most preferably 30 to 60 minutes. If the treatment time in the chlorine dioxide bleaching step is 10 minutes or longer, the resulting bleached pulp may have a higher whiteness, and the resulting bleached pulp may be less susceptible to deterioration. On the other hand, if the treatment time in the chlorine dioxide bleaching step is 150 minutes or less, it is preferable from the viewpoint that bleached pulp excellent in whiteness can be efficiently produced, productivity is excellent, and the like.
[ alkaline Hydrogen peroxide bleaching Process (Ep Process) ]
The alkaline hydrogen peroxide bleaching step is a step of removing lignin and the like contained in pulp by hydrogen peroxide bleaching under alkaline conditions. Alkaline hydrogen peroxide bleaching is generally performed by adding hydrogen peroxide to a pulp slurry containing alkaline pulp and performing a bleaching treatment. In one embodiment, the method for producing bleached pulp preferably further comprises: an alkaline hydrogen peroxide bleaching step of treating with alkaline hydrogen peroxide. The pulp obtained after the bleaching treatment is suitably washed.
(pulp slurry)
The pulp slurry comprises pulp and water.
(pulp)
The pulp is not particularly limited, and may be unbleached pulp or pulp subjected to other bleaching steps, but is preferably unbleached pulp.
The pulp concentration is preferably 8 to 40 mass%, more preferably 10 to 35 mass% with respect to the total mass of the pulp slurry.
The pH of the pulp slurry is alkaline. The pH of the pulp slurry is particularly preferably 8 to 14, more preferably 10 to 14.
In addition, an alkali such as sodium hydroxide (caustic soda) or potassium hydroxide may be used for adjusting the pH of the pulp slurry; sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, carbonic acid, and the like.
(bleaching treatment)
The method of the bleaching treatment is not particularly limited, and examples thereof include a medium consistency method (pulp consistency: 8 to 25 mass%, preferably 10 to 15 mass%) and a high consistency method (pulp consistency: 25 to 40 mass%). Among them, the medium concentration method is preferable.
The hydrogen peroxide is preferably added in the form of an aqueous hydrogen peroxide solution. At this time, the aqueous hydrogen peroxide solution contains hydrogen peroxide and water. The aqueous hydrogen peroxide solution may further comprise additives.
The concentration of hydrogen peroxide in the aqueous hydrogen peroxide solution is preferably 1 to 80% by mass, more preferably 10 to 70% by mass, and still more preferably 30 to 65% by mass, based on the total mass of the aqueous hydrogen peroxide solution.
The additives are not particularly limited, and examples thereof include stabilizers such as sodium silicate, magnesium silicate, nitrilotriacetic acid (NTA), ethylenediamine tetraacetic acid (EDTA), diethylenetriamine pentaacetic acid (DTPA), aminotri (methylenesulfonic Acid) (ATMP), diethylenetriamine penta (methylenephosphonic acid) (DTPMP), and poly- α -hydroxy sodium acrylate (PHAS). These stabilizers may be used alone or in combination of 2 or more.
The concentration of the additive in the aqueous hydrogen peroxide solution is preferably 0.01 to 5% by mass, more preferably 0.05 to 3% by mass, and still more preferably 0.1 to 1% by mass, relative to the total mass of the aqueous hydrogen peroxide solution.
The amount of hydrogen peroxide to be added is preferably 0.01 to 10% by mass, more preferably 0.03 to 5% by mass, and still more preferably 0.05 to 2% by mass, based on the absolute dry mass of the unbleached pulp.
In the alkaline hydrogen peroxide bleaching step, oxygen may be further added together with hydrogen peroxide. Oxygen is added to bleach the fabric at the same time. In the case where oxygen is used in combination in the alkaline hydrogen peroxide bleaching step (Ep step), the step is sometimes referred to as an Eop step in particular.
The addition rate of oxygen is preferably 0.1 to 3 mass% relative to the absolute dry mass of unbleached pulp.
In this case, the oxygen to be used is not particularly limited, and examples thereof include oxygen obtained by a cryogenic separation method, oxygen obtained by pressure swing adsorption (PSA: pressure Swing Adsorption), and oxygen obtained by vacuum pressure swing adsorption (VSA: vacuum Swing Adsorption).
The treatment temperature in the alkaline hydrogen peroxide bleaching step is preferably 40 to 120 ℃, more preferably 50 to 100 ℃, and still more preferably 60 to 90 ℃.
The treatment time in the alkaline hydrogen peroxide bleaching step is preferably 15 to 150 minutes, more preferably 15 to 120 minutes, and still more preferably 15 to 100 minutes.
Modification example
In the above embodiment, the description was made of the mode including the unbleached pulp preparation step, the oxygen-alkali bleaching step (O step), the peroxysulfuric acid bleaching step (MPS step), the ozone bleaching step (Z step), the bleaching step (D step), and the alkaline hydrogen peroxide bleaching step (Ep step) in this order, but the mode of the repeated modification examples may be formed in which the presence or absence of the respective bleaching steps, the order change, and the change of the order of the respective bleaching steps are performed. Thus, physical properties of the obtained bleached pulp, the amount of chlorine dioxide used, and the like can be appropriately controlled.
In one embodiment, the method for producing bleached pulp includes, in order, an O process, an MPS process, a 1D process, an Ep process, and a 2D process. By omitting the Z step, the manufacturing cost can be reduced.
In another embodiment, the method for producing bleached pulp includes, in order, an O process, an MPS process, a Z process, a 1D process, an Eop process, and a 2D process. In this case, the above-mentioned Eop step is a step of using oxygen together in the Ep step as described above. Further, it is preferable that the step 1D is performed after the step Z without cleaning.
In another embodiment, the method for producing bleached pulp includes, in order, an O step, an MPS step, a Z step, a 1D step, an Ep step, and a 2D step. In this case, it is preferable that the step 1D is performed after the step Z without cleaning.
In another embodiment, the method for producing bleached pulp includes, in order, an O step, an MPS step, a Z step, an Ep step, and a 1D step. In this case, it is preferable that the step Z is followed by the step Ep without cleaning.
[ bleached pulp ]
The bleached pulp produced by the above production method is excellent in whiteness. Specifically, the whiteness of the bleached pulp is preferably 50% or more, more preferably 50 to 80%, and still more preferably 55 to 70%. The bleached pulp having a whiteness of 50% or more is preferable because it is excellent in whiteness. In this specification, the whiteness of bleached pulp was measured by the method according to the example.
The whiteness increase rate of the bleached pulp (whiteness of the bleached pulp/whiteness of the unbleached pulp×100) is preferably 115% or more, more preferably 117% or more, still more preferably 119% or more, particularly preferably 120% or more, and most preferably 121% or more.
The potassium permanganate number (K value) of the bleached pulp is preferably 6 or less, more preferably 5 or less, further preferably 1 to 4, particularly preferably 2 to 3. The K value of the bleached pulp is preferably 6 or less, because the bleached pulp is excellent in whiteness. The K value of the bleached pulp is an index indicating the amount of residual lignin in the pulp. In addition, in the present specification, the K value of bleached pulp is a value measured by the method according to examples.
The K-value residual ratio of the bleached pulp (K-value of the bleached pulp/K-value of the unbleached pulp×100) is preferably 65% or less, more preferably 56% or less, further preferably 40% or less, particularly preferably 35% or less, and most preferably 33% or less.
Further, the viscosity of the bleached pulp is preferably 10cP or more, more preferably 12cP or more, and still more preferably 14 to 20cP. If the viscosity of the bleached pulp is 10cP or more, the strength of the paper can be maintained, which is preferable. In this specification, the viscosity of bleached pulp was measured by the method according to examples.
The retention of the viscosity of the bleached pulp (viscosity of the bleached pulp/viscosity of the unbleached pulp×100) is preferably 60% or more, more preferably 70% or more, still more preferably 80% or more, particularly preferably 85% or more.
The hexenuronic acid content (HexA content) of the bleached pulp is preferably 30. Mu. Mol/g or less, more preferably 20. Mu. Mol/g or less, and still more preferably 1 to 10. Mu. Mol/g. If the HexA content of the bleached pulp is 30. Mu. Mol/g or less, the bleached pulp is preferably not liable to fade. In this specification, the HexA content of bleached pulp was measured by the method according to examples.
The residual ratio of the HexA content of the bleached pulp (HexA content of the bleached pulp/HexA content of the unbleached pulp×100) is preferably 75% or less, more preferably 65% or less, further preferably 60% or less, particularly preferably 30% or less, and most preferably 15% or less.
In the present invention, the ratio of the rate of addition of the peroxymonosulfuric acid in the peroxymonosulfuric acid bleaching step (MPS step) to the rate of addition of the chlorine dioxide in the 1 st chlorine dioxide bleaching step (D step) is set to a predetermined range, whereby lignin and the like can be removed, and bleached pulp excellent in whiteness can be produced. This effect is a significantly higher effect than the conventional art in which the sulfuric acid bleaching step (MPS step) is performed instead of the sulfuric acid bleaching step performed with sulfuric acid. Thus, the total organic matters in the methods can be comparedCarbon (TOC) ratio. Specifically, in the method of the present invention, first, TOC is calculated as the sum of TOC of the drainage water obtained in the peroxymonosulfuric acid bleaching step (the washing effluent of pulp after bleaching) and TOC of the drainage water obtained in the 1 st chlorine dioxide bleaching step (the washing effluent of pulp after bleaching) 1 . In the conventional method (specifically, a method for performing a sulfuric acid bleaching step instead of the MPS step of the method of the present invention, hereinafter, also referred to as "reference method"), the TOC is calculated as the sum of the TOC of the effluent obtained in the sulfuric acid bleaching step (the wash effluent of the pulp after the bleaching treatment) and the TOC of the effluent obtained in the 1 st chlorine dioxide bleaching step (the wash effluent of the pulp after the bleaching treatment) 2 . Then, these TOC increase rates (TOC 1 /TOC 2 X 100), preferably more than 100%, more preferably more than 110%, still more preferably more than 115%. Here, TOC in the wastewater contains lignin and substances derived from bleaching (lignin derivatives and the like). Therefore, if the TOC increase rate exceeds 100%, it is indicated that: lignin and the like can be suitably removed as compared with the prior art in which the sulfuric acid bleaching step is performed. That is, in a preferred embodiment, the Total Organic Carbon (TOC) of the effluent obtained in the peroxymonosulfuric acid bleaching step and the 1 st chlorine dioxide bleaching step 1 ) Total Organic Carbon (TOC) of the effluent obtained in the sulfuric acid bleaching step and the 1 st chlorine dioxide bleaching step in the reference method in which the sulfuric acid bleaching step treated with sulfuric acid is performed instead of the peroxymonosulfuric acid bleaching step is used 2 ) Is a TOC increase rate (TOC) 1 /TOC 2 X 100) is preferably more than 100%, more preferably more than 110%, still more preferably more than 115%.
Examples
Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The term "%" is a mass basis unless otherwise specified.
Example 1
Bleached pulp was produced by performing a peroxymonosulfuric acid bleaching step (MPS step) and a 1 st chlorine dioxide bleaching step (D step) on pulp (hereinafter referred to as "raw material pulp") after the oxygen-alkali bleaching step (O step) in which unbleached pulp was subjected to oxygen-alkali bleaching.
(Persulfuric acid bleaching Process (MPS Process))
A polyethylene bag was sampled with an oven-dried mass of 34g of raw pulp (whiteness: 49.2%, K value: 7.0, viscosity 18cP, hexA content: 32.6. Mu. Mol/g). The hollow fiber membrane-filtered water required for bleaching was added to a pulp concentration of 10%, and then a predetermined amount of sulfuric acid aqueous solution was added to adjust the pH at the start of the reaction to about 3, followed by thorough mixing. Thereafter, peroxomonosulfuric acid was added in an amount of 0.13 mass% based on the absolute dry mass of the unbleached pulp, and the mixture was further mixed.
Immersing in a constant temperature water tank at 98 ℃ for 120 minutes, thereby performing bleaching treatment.
And cleaning the pulp after the MPS process. Specifically, pure water was added until the pulp concentration became 2.4%, and then dehydration was performed until the pulp concentration became 20% (washing rate 90%).
(1 st chlorine dioxide bleaching step (D step))
The bleached pulp obtained in the above was sampled in a polyethylene bag with an oven dry mass of 16 g. The hollow fiber membrane-filtered water required for bleaching was added to a pulp concentration of 10%, and then a predetermined amount of sulfuric acid aqueous solution was added to adjust the pH at the start of the reaction to about 3, followed by thorough mixing. After that, chlorine dioxide was added in an amount of 0.50 mass% relative to the absolute dry mass of the unbleached pulp, and further mixed. The ratio of the addition rate of chlorine dioxide to the absolute dry mass of unbleached pulp (0.50 mass%) to the addition rate of peroxomonosulfuric acid to the absolute dry mass of unbleached pulp (0.13 mass%), i.e., the addition rate of chlorine dioxide/the addition rate of peroxomonosulfuric acid, was 3.85.
The pulp was washed in the same manner as in the MPS step by immersing in a water bath at a constant temperature of 70 ℃ for 120 minutes to perform bleaching treatment.
The ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) of the bleached pulp were measured by the following methods. In each measurement, a pulp sheet (acid paper) produced by the following method was used as a measurement sample. Here, the pulp sheet (acid paper making) was diluted with 2L of pure water and then adjusted to ph5.5 with sulfurous acid water. Next, 2 sheets were prepared on a buchner funnel, and air-dried for 12 hours, thereby preparing the tablets.
[ ISO whiteness ]
According to JISP8148:2018, whiteness (%). As a result, the ISO whiteness was 57.4% (the rate of increase in whiteness relative to the raw material pulp: 117%).
[ Potassium permanganate value (K value) ]
According to TAPPI UM 253:2010, the K value is determined. As a result, the K value was 2.6 (residual ratio of K value relative to the raw material pulp: 37%).
[ viscosity ]
Viscosity was determined according to J.TAPPI No.44 method. As a result, the viscosity was 15cP (retention of viscosity relative to the raw material pulp: 83%).
[ hexenuronic acid content (HexA content) ]
After the pulp sheet (acid paper making) was oven-dried, 0.8g of the pulp sheet (acid paper making) in oven-dried mass was precisely weighed and placed in a pressure-resistant vessel. Next, 80mL of pure water was added thereto, and then formic acid was added thereto to adjust the pH to 3. The pressure vessel was placed in an oven and treated at 120℃for 4 hours to effect acid hydrolysis of HexA. After the treatment, filtration was performed, and 2-furoic acid and 5-carboxy-2-furaldehyde, which are acid hydrolysates of HexA present in the filtered solution, were quantified by HPLC, and the original HexA content was calculated from the total of their molar amounts. As a result, the HexA content of the bleached pulp was 6.4. Mu. Mol/g (residual ratio of HexA content relative to the starting pulp: 20%).
[ Total Organic Carbon (TOC) in drainage ]
50mL of washing water discharged from dewatering (water discharged from the MPS step) during washing of the pulp after the MPS step was collected. The TOC in the wastewater of the MPS process was measured using a total organic carbon meter TOV-VCN (SHIMADZU) by volatilizing inorganic carbon by adding acid and aeration treatment, and using a sample in an NPOC mode as a Non-volatile organic carbon (NPOC) measurement. Note that according to JISK0551:1994, potassium hydrogen phthalate and sodium hydrogencarbonate were used as standard samples.
Further, 50mL of the washing water (water discharged from the step D) obtained by dewatering the pulp in the step D was collected, and TOC in the water discharged from the step D was measured in the same manner as the water discharged from the step MPS.
The sum of the TOC in the wastewater from the MPS step and the TOC in the wastewater from the D step (hereinafter, sometimes simply referred to as "total organic carbon in wastewater (TOC)") is 289mg/L.
Here, the TOC increase rate in the drainage in example 1 was calculated based on reference example 1 (reference method) in which the sulfuric acid bleaching step with sulfuric acid was performed, instead of the MPS step in example 1. Reference example 1 was performed as follows.
Reference example 1
A bleached pulp was produced in the same manner as in example 1, except that the peroxymonosulfuric acid was not added in the peroxymonosulfuric acid bleaching step (MPS step).
The ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in the drainage of the bleached pulp were measured in the same manner as described above. As a result, the ISO whiteness was 56.4% (rate of rise relative to the raw material pulp: 115%), the K value was 2.6 (rate of retention relative to the raw material pulp: 37%), the viscosity was 14cP (rate of retention relative to the raw material pulp: 78%), and the HexA content was 4.8. Mu. Mol/g (rate of retention relative to the raw material pulp: 15%). In addition, as described above, TOC in the effluent of the MPS step (sulfuric acid bleaching step) and TOC in the effluent of the D step were measured, and the sum (total organic carbon (TOC) in the effluent) was calculated, resulting in 257mg/L.
The TOC increase rate in the drainage of example 1 was calculated from the following equation, and found to be 112%.
[ math figure 2]
Example 2
A bleached pulp was produced in the same manner as in example 1, except that the amount of the peroxymonosulfuric acid added in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 0.20 mass% based on the absolute dry mass of the unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 2.50.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 1. As a result, the ISO whiteness was 58.3% (rate of rise relative to the raw material pulp: 119%), the K value was 2.4 (rate of retention relative to the raw material pulp: 35%), the viscosity was 15cP (retention relative to the raw material pulp: 83%), the HexA content was 5.6. Mu. Mol/g (rate of retention relative to the raw material pulp: 17%), and the TOC in the drainage was 295mg/L (rate of increase in TOC relative to reference example 1: 115%).
Example 3
A bleached pulp was produced in the same manner as in example 1, except that the amount of the peroxymonosulfuric acid added in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 0.25 mass% based on the absolute dry mass of the unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 2.00.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 1. As a result, the ISO whiteness was 59.0% (120% relative to the rising rate of the raw material pulp), the K value was 2.38 (34% relative to the residual rate of the raw material pulp), the viscosity was 14.6cP (81% relative to the holding rate of the raw material pulp), the HexA content was 4.8. Mu. Mol/g (15% relative to the residual rate of the raw material pulp), and the TOC in the drainage was 295mg/L (115% relative to the TOC increasing rate of reference example 1).
Example 4
Bleached pulp was produced in the same manner as in example 1, except that the pH at the start of the reaction in the peroxymonosulfuric acid bleaching step (MPS step) was changed to about 3.5, and the addition amount of peroxymonosulfuric acid was changed to 0.40 mass% relative to the absolute dry mass of unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 1.25.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 1. As a result, the ISO whiteness was 60.6% (rate of rise relative to the raw material pulp: 123%), the K value was 2.2 (rate of retention relative to the raw material pulp: 32%), the viscosity was 14cP (retention relative to the raw material pulp: 78%), the HexA content was 3.9. Mu. Mol/g (rate of retention relative to the raw material pulp: 12%), and the TOC in the drainage was 297mg/L (rate of increase in TOC relative to reference example 1: 116%).
Example 5
A bleached pulp was produced in the same manner as in example 1, except that the amount of the peroxymonosulfuric acid added in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 0.60 mass% relative to the absolute dry mass of the unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 0.83.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 1. As a result, the ISO whiteness was 60.0% (122% relative to the rising rate of the raw material pulp), the K value was 2.2 (32% relative to the residual rate of the raw material pulp), the viscosity was 13.2cP (73% relative to the holding rate of the raw material pulp), the HexA content was 3.2. Mu. Mol/g (10% relative to the residual rate of the raw material pulp), and the TOC in the drainage was 295mg/L (115% relative to the TOC increasing rate of reference example 1).
Example 6
Bleached pulp was produced in the same manner as in example 1, except that the pH at the start of the reaction in the peroxymonosulfuric acid bleaching step (MPS step) was changed to about 3.2, and the addition amount of peroxymonosulfuric acid was changed to 1.50 mass% relative to the absolute dry mass of unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 0.33.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 1. As a result, the ISO whiteness was 59.2% (rate of rise relative to the raw material pulp: 120%), the K value was 2.3 (rate of retention relative to the raw material pulp: 33%), the viscosity was 12cP (retention relative to the raw material pulp: 67%), the HexA content was 2.0. Mu. Mol/g (rate of retention relative to the raw material pulp: 6%), and the TOC in the drainage was 287mg/L (rate of increase in TOC relative to reference example 1: 112%).
Comparative example 1
Bleached pulp was produced in the same manner as in example 1, except that the pH at the start of the reaction in the peroxymonosulfuric acid bleaching step (MPS step) was changed to about 3.2, the amount of peroxymonosulfuric acid added was changed to 2.00 mass% relative to the absolute dry mass of unbleached pulp, and the amount of chlorine dioxide added in the 1 st chlorine dioxide bleaching step (D step) was changed to 0.25 mass% relative to the absolute dry mass of unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 0.13.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 1. As a result, the ISO whiteness was 56.2% (rate of rise relative to the raw material pulp: 114%), the K value was 2.6 (rate of retention relative to the raw material pulp: 37%), the viscosity was 11cP (retention relative to the raw material pulp: 61%), the HexA content was 2.5. Mu. Mol/g (rate of retention relative to the raw material pulp: 8%), and the TOC in the drainage was 271mg/L (rate of increase in TOC relative to reference example 1: 105%).
Comparative example 2
Bleached pulp was produced in the same manner as in example 1, except that the amount of the added peroxymonosulfuric acid in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 0.10 mass% relative to the absolute dry mass of the unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 5.00.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 1. As a result, the ISO whiteness was 55.8% (rate of rise relative to the raw material pulp: 113%), the K value was 2.7 (rate of retention relative to the raw material pulp: 39%), the viscosity was 15cP (retention relative to the raw material pulp: 83%), the HexA content was 6.7. Mu. Mol/g (rate of retention relative to the raw material pulp: 21%), and the TOC in the drainage was 276mg/L (rate of increase in TOC relative to reference example 1: 107%).
Example 7
A bleached pulp was produced in the same manner as in example 1, except that the bleaching temperature in the peroxysulfuric acid bleaching step (MPS step) was changed to 50℃and the bleaching time was changed to 90 minutes, and the bleaching temperature in the 1 st chlorine dioxide bleaching step (D step)) was changed to 60℃and the bleaching time was changed to 35 minutes, using the raw material pulp (whiteness: 54.7%, K value: 7.0, viscosity 19cP, and HexA content: 36.1. Mu. Mol/g). The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 3.85.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, and hexenuronic acid content (HexA content) in the same manner as in example 1. As a result, the ISO whiteness was 63.2% (116% relative to the rising rate of the raw material pulp), the K value was 4.0 (57% relative to the residual rate of the raw material pulp), the viscosity was 17cP (89% relative to the holding rate of the raw material pulp), and the HexA content was 25.0. Mu. Mol/g (69% relative to the residual rate of the raw material pulp).
The Total Organic Carbon (TOC) in the wastewater was measured in the same manner as in example 1, and the total organic carbon was 106mg/L. The TOC increase rate in example 7 was calculated based on reference example 2 (reference method) in which the MPS step in example 7 was replaced with the sulfuric acid bleaching step in which the treatment with sulfuric acid was performed. Reference example 2 is performed as follows.
Reference example 2
A bleached pulp was produced in the same manner as in example 7, except that the peroxymonosulfuric acid was not added in the peroxymonosulfuric acid bleaching step (MPS step).
The ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in the drainage of the bleached pulp were measured in the same manner as described above. As a result, the ISO whiteness was 62.4% (rate of rise relative to the raw material pulp: 114%), the K value was 4.3 (rate of residue relative to the raw material pulp: 61%), the viscosity was 17cP (rate of retention relative to the raw material pulp: 89%), and the HexA content was 28.9. Mu. Mol/g (rate of residue relative to the raw material pulp: 80%). Further, TOC in the effluent of the MPS step (sulfuric acid bleaching step) and TOC in the effluent of the D step were measured in the same manner as described above, and the sum (total organic carbon (TOC) in the effluent) was calculated, resulting in 91mg/L.
The TOC increase rate in the drainage of example 7 was calculated according to the following equation, and found to be 116%.
[ math 3]
Example 8
Bleached pulp was produced in the same manner as in example 7, except that the amount of the peroxymonosulfuric acid added in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 0.20 mass% based on the absolute dry mass of the unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 2.50.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 7. As a result, the ISO whiteness was 64.2% (rate of rise relative to the raw material pulp: 117%), the K value was 3.8 (rate of retention relative to the raw material pulp: 54%), the viscosity was 17cP (retention relative to the raw material pulp: 89%), the HexA content was 23.5. Mu. Mol/g (rate of retention relative to the raw material pulp: 65%), and the TOC in the drainage was 108mg/L (rate of increase in TOC relative to reference example 2: 119%).
Example 9
A bleached pulp was produced in the same manner as in example 7, except that the amount of the peroxymonosulfuric acid added in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 0.25 mass% based on the absolute dry mass of the unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 2.00.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 7. As a result, the ISO whiteness was 65.1% (rate of rise relative to the raw material pulp: 119%), the K value was 3.7 (rate of retention relative to the raw material pulp: 53%), the viscosity was 16.5cP (retention relative to the raw material pulp: 87%), the HexA content was 22.7. Mu. Mol/g (rate of retention relative to the raw material pulp: 63%), and the TOC in the drainage was 109mg/L (rate of increase in TOC relative to reference example 2: 120%).
Example 10
Bleached pulp was produced in the same manner as in example 7, except that the pH at the start of the reaction in the peroxymonosulfuric acid bleaching step (MPS step) was changed to about 3.5, and the addition amount of peroxymonosulfuric acid was changed to 0.40 mass% relative to the absolute dry mass of unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 1.25.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 7. As a result, the ISO whiteness was 66.9% (122% relative to the rising rate of the raw material pulp), the K value was 3.6 (51% relative to the residual rate of the raw material pulp), the viscosity was 16cP (84% relative to the holding rate of the raw material pulp), the HexA content was 21.0. Mu. Mol/g (58% relative to the residual rate of the raw material pulp), and the TOC in the drainage was 110mg/L (121% relative to the TOC increasing rate of reference example 2).
Example 11
The amount of the added peroxymonosulfuric acid in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 0.60 mass% relative to the absolute dry mass of the unbleached pulp. Except for this, bleached pulp was produced in the same manner as in example 7. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 0.83.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 7. As a result, the ISO whiteness was 66.2% (rate of rise relative to the raw material pulp: 121%), the K value was 3.64 (rate of retention relative to the raw material pulp: 52%), the viscosity was 15.8cP (retention relative to the raw material pulp: 83%), the HexA content was 18.8. Mu. Mol/g (rate of retention relative to the raw material pulp: 52%), and the TOC in the drainage was 108mg/L (rate of increase in TOC relative to reference example 2: 119%).
Example 12
Bleached pulp was produced in the same manner as in example 7, except that the pH at the start of the reaction in the peroxymonosulfuric acid bleaching step (MPS step) was changed to about 3.2, and the addition amount of peroxymonosulfuric acid was changed to 1.50 mass% relative to the absolute dry mass of unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 0.33.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 7. As a result, the ISO whiteness was 64.0% (rate of rise relative to the raw material pulp: 117%), the K value was 3.9 (rate of retention relative to the raw material pulp: 56%), the viscosity was 16cP (retention relative to the raw material pulp: 84%), the HexA content was 8.4. Mu. Mol/g (rate of retention relative to the raw material pulp: 23%), and the TOC in the drainage was 107mg/L (rate of increase in TOC relative to reference example 2: 118%).
Comparative example 3
A bleached pulp was produced in the same manner as in example 7, except that the amount of the peroxymonosulfuric acid added in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 2.00 mass% relative to the absolute dry mass of the unbleached pulp, and the amount of chlorine dioxide added in the chlorine dioxide bleaching step 1 (D step) was changed to 0.25 mass% relative to the absolute dry mass of the unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 0.13.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 7. As a result, the ISO whiteness was 62.1% (rate of rise relative to the raw material pulp: 114%), the K value was 4.0 (rate of retention relative to the raw material pulp: 57%), the viscosity was 15cP (retention relative to the raw material pulp: 79%), the HexA content was 10.5. Mu. Mol/g (rate of retention relative to the raw material pulp: 29%), and the TOC in the drainage was 98mg/L (rate of increase in TOC relative to reference example 2: 108%).
Comparative example 4
A bleached pulp was produced in the same manner as in example 7, except that the amount of the peroxymonosulfuric acid added in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 0.10 mass% relative to the absolute dry mass of the unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 5.00.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 7. As a result, the ISO whiteness was 62.6% (rate of rise relative to raw material pulp: 114%), the K value was 4.0 (rate of retention relative to raw material pulp: 57%), the viscosity was 17cP (retention relative to raw material pulp: 89%), the HexA content was 26.2. Mu. Mol/g (rate of retention relative to raw material pulp: 73%), and the TOC in drainage was 101mg/L (rate of increase in TOC relative to reference example 2: 111%).
Example 13
Bleached pulp was produced in the same manner as in example 4, except that the bleaching treatment time in the peroxysulfuric acid bleaching step (MPS step) was changed to 2 minutes. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 1.25.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 1. As a result, the ISO whiteness was 58.0% (rate of rise relative to the raw material pulp: 118%), the K value was 4.3 (rate of retention relative to the raw material pulp: 62%), the viscosity was 17cP (retention relative to the raw material pulp: 94%), the HexA content was 23.1. Mu. Mol/g (rate of retention relative to the raw material pulp: 71%), and the TOC in the drainage was 277mg/L (rate of increase in TOC relative to reference example 1: 108%).
Example 14
Bleached pulp was produced in the same manner as in example 4, except that the bleaching treatment time in the peroxysulfuric acid bleaching step (MPS step) was changed to 7 minutes. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 1.25.
The bleached pulp was measured for ISO whiteness, potassium permanganate number (K value), viscosity, hexenuronic acid content (HexA content) and Total Organic Carbon (TOC) in drainage in the same manner as in example 1. As a result, the ISO whiteness was 58.3% (rate of rise relative to the raw material pulp: 118%), the K value was 4.3 (rate of retention relative to the raw material pulp: 61%), the viscosity was 16cP (retention relative to the raw material pulp: 89%), the HexA content was 19.1. Mu. Mol/g (rate of retention relative to the raw material pulp: 59%), and the TOC in the drainage was 285mg/L (rate of increase in TOC relative to reference example 1: 111%).
The results obtained are shown in table 1 below.
TABLE 1
From the results in table 1, it is clear that the bleached pulps produced in examples 1 to 14 are excellent in whiteness.
In examples 1, 2, 4 and 6, absorbance at a wavelength of 280nm was measured by a spectrophotometer (UV-2450; shimadzu corporation) for mixed drainage of 50mL of drainage in the MPS step and 50mL of drainage in the D step. The results obtained are shown in table 2 below.
TABLE 2
| ClO 2 /MPS | Absorbance of light | |
| Example 1 | 3.85 | 0.473 |
| Example 2 | 2.50 | 0.495 |
| Example 4 | 1.25 | 0.508 |
| Example 6 | 0.33 | 0.435 |
From the results in Table 2, it is clear that the effluent contains aromatic compounds. In this case, the aromatic compound is presumed to be lignin or a derivative thereof.
[ ISO whiteness and viscosity after deterioration test ]
The ISO whiteness and viscosity of the bleached pulps of examples 1, 2, 4, 6, 7, 10 and 12, comparative examples 2 and 4, reference examples 1 and 2 and examples 15 to 23 described below were measured. Further, a degradation test was performed, and the ISO whiteness and viscosity of the bleached pulp after the degradation test were measured. In each measurement, a pulp sheet (acid paper sheet) produced in the same manner as in example 1 was used as a measurement sample.
Example 15
A bleached pulp was produced in the same manner as in example 1, except that the amount of the peroxymonosulfuric acid added in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 2.00 mass% relative to the absolute dry mass of the unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 0.25.
Example 16
A bleached pulp was produced in the same manner as in example 4, except that the bleaching temperature in the 1 st chlorine dioxide bleaching step (step D)) was changed to 60 ℃ and the bleaching time was changed to 35 minutes. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 1.25.
Example 17
A bleached pulp was produced in the same manner as in example 6, except that the bleaching temperature in the 1 st chlorine dioxide bleaching step (step D)) was changed to 60 ℃ and the bleaching time was changed to 35 minutes. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 0.33.
Example 18
Bleached pulp was produced in the same manner as in example 6, except that the bleaching treatment time in the peroxysulfuric acid bleaching step (MPS step) was changed to 90 minutes. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 0.33.
Example 19
A bleached pulp was produced in the same manner as in example 1, except that the amount of the added peroxymonosulfuric acid in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 0.40 mass% based on the absolute dry mass of the unbleached pulp, the bleaching temperature was changed to 70 ℃, the bleaching time was changed to 90 minutes, and the bleaching temperature in the 1 st chlorine dioxide bleaching step (D step)) was changed to 60 ℃ and the bleaching time was changed to 35 minutes. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 1.25.
Example 20
A bleached pulp was produced in the same manner as in example 19, except that the amount of the peroxymonosulfuric acid added in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 1.50% by mass relative to the absolute dry mass of the unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 0.33.
Example 21
Bleached pulp was produced in the same manner as in example 19, except that the amount of the added peroxymonosulfuric acid in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 1.50 mass% relative to the absolute dry mass of unbleached pulp, the bleaching treatment time was changed to 120 minutes, and the bleaching treatment temperature in the 1 st chlorine dioxide bleaching step (D step)) was changed to 70 ℃. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 0.33.
Example 22
Bleached pulp was produced in the same manner as in example 6, except that the bleaching temperature in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 60 ℃. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 0.33.
Example 23
A bleached pulp was produced in the same manner as in example 7, except that the amount of the peroxymonosulfuric acid added in the peroxymonosulfuric acid bleaching step (MPS step) was changed to 2.00% by mass relative to the absolute dry mass of the unbleached pulp. The addition ratio of chlorine dioxide/the addition ratio of peroxomonosulfuric acid was 0.25.
(deterioration test)
The degradation test was carried out according to the paper and board-accelerated degradation treatment method (JIS 8154-3:2008), and the acid paper was kept at 80℃for 24 hours under a relative humidity of 65%.
(ISO whiteness)
The ISO whiteness before and after the degradation test was measured in the same manner as in example 1, and the whiteness change rate was calculated from the following equation. The results obtained are shown in table 3 below.
[ mathematics 4]
(viscosity)
The viscosity before and after the degradation test was measured in the same manner as in example 1, and the viscosity difference was calculated according to the following formula. The results obtained are shown in table 3 below.
[ math 5]
Viscosity reduction (cP) =viscosity after degradation test (cP) -viscosity before degradation test (cP)
TABLE 3
From the results of table 3, it is understood that the whiteness of the bleached pulps produced in examples 1, 2, 4, 6, 7, 10, 12 and 15 to 23 is not easily lowered even after the degradation test.
Claims (13)
1. A method for producing bleached pulp, comprising the steps of:
an oxygen-alkali bleaching step of oxygen-alkali bleaching the unbleached pulp;
a peroxymonosulfuric acid bleaching step of treating with peroxymonosulfuric acid; and, a step of, in the first embodiment,
a 1 st chlorine dioxide bleaching step of treating with chlorine dioxide;
the ratio of the addition rate (mass%) of chlorine dioxide to the absolute dry mass of the unbleached pulp to the addition rate (mass%) of peroxomonosulfuric acid to the absolute dry mass of the unbleached pulp (addition rate of chlorine dioxide/addition rate of peroxomonosulfuric acid) is 0.25 to 4.0.
2. A method for producing bleached pulp, comprising the steps of:
an oxygen-alkali bleaching step of oxygen-alkali bleaching the unbleached pulp;
a peroxymonosulfuric acid bleaching step of treating with peroxymonosulfuric acid; and, a step of, in the first embodiment,
a 1 st chlorine dioxide bleaching step of treating with chlorine dioxide;
the ratio of the addition rate (mass%) of chlorine dioxide to the absolute dry mass of the unbleached pulp to the addition rate (mass%) of peroxomonosulfuric acid to the absolute dry mass of the unbleached pulp (addition rate of chlorine dioxide/addition rate of peroxomonosulfuric acid) is 0.25 to 2.0,
the treatment temperature of the peroxymonosulfuric acid bleaching process is 70-98 ℃.
3. The production method according to claim 2, further comprising an alkaline hydrogen peroxide bleaching step of treating with alkaline hydrogen peroxide.
4. The production method according to claim 2 or 3, further comprising an ozone bleaching step of treating with ozone.
5. A method for producing bleached pulp, comprising the following steps in order:
an oxygen-alkali bleaching step of oxygen-alkali bleaching the unbleached pulp;
a peroxymonosulfuric acid bleaching step of treating with peroxymonosulfuric acid;
a 1 st chlorine dioxide bleaching step of treating with chlorine dioxide;
an alkaline hydrogen peroxide bleaching step of treating with alkaline hydrogen peroxide; and, a step of, in the first embodiment,
A 2 nd chlorine dioxide bleaching process, which is to treat with chlorine dioxide,
the ratio of the addition rate (mass%) of chlorine dioxide to the absolute dry mass of the unbleached pulp in the 1 st chlorine dioxide bleaching step to the addition rate (mass%) of peroxomonosulfuric acid to the absolute dry mass of the unbleached pulp (addition rate of chlorine dioxide/addition rate of peroxomonosulfuric acid) is 0.25 to 2.0,
the treatment temperature of the peroxymonosulfuric acid bleaching process is 70-98 ℃.
6. A method for producing bleached pulp, comprising the steps of:
an oxygen-alkali bleaching step of oxygen-alkali bleaching the unbleached pulp;
a peroxymonosulfuric acid bleaching step of treating with peroxymonosulfuric acid; and, a step of, in the first embodiment,
a 1 st chlorine dioxide bleaching process, which uses chlorine dioxide to process,
the addition rate (mass%) of the peroxymonosulfuric acid to the absolute dry mass of the unbleached pulp is 0.30 to 1.75 mass%,
the ratio of the addition rate (mass%) of chlorine dioxide to the absolute dry mass of the unbleached pulp to the addition rate (mass%) of peroxomonosulfuric acid to the absolute dry mass of the unbleached pulp (addition rate of chlorine dioxide/addition rate of peroxomonosulfuric acid) is 0.5 to 2.0.
7. The method according to claim 6, further comprising an alkaline hydrogen peroxide bleaching step of treating with alkaline hydrogen peroxide.
8. The production method according to claim 6 or 7, further comprising an ozone bleaching step of treating with ozone.
9. The production method according to any one of claims 6 to 8, wherein the treatment temperature in the peroxymonosulfuric acid bleaching step is 40 to 98 ℃.
10. The production process according to any one of claims 1 to 9, wherein the Total Organic Carbon (TOC) of the wastewater obtained in the peroxymonosulfuric acid bleaching step and the 1 st chlorine dioxide bleaching step 1 ) Total Organic Carbon (TOC) of the effluent obtained in the sulfuric acid bleaching step and the 1 st chlorine dioxide bleaching step in the reference method in which the sulfuric acid bleaching step is replaced with the sulfuric acid bleaching step of sulfuric acid treatment 2 ) Is a TOC increase rate (TOC) 1 /TOC 2 X 100) exceeds 100%.
11. The manufacturing method of claim 10, further comprising the operations of: at least a part of the drainage water obtained in the peroxymonosulfuric acid bleaching step and the drainage water obtained in the 1 st chlorine dioxide bleaching step is reused in the peroxymonosulfuric acid bleaching step.
12. The method according to any one of claims 1 to 11, wherein the treatment time in the peroxymonosulfuric acid bleaching step is 2 to 200 minutes.
13. The production method according to any one of claims 1 to 12, wherein the treatment pH in the peroxymonosulfuric acid bleaching step is 2 to 5.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2020-190390 | 2020-11-16 | ||
| JP2020190390 | 2020-11-16 | ||
| PCT/JP2021/031196 WO2022102206A1 (en) | 2020-11-16 | 2021-08-25 | Method for producing bleached pulp |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116507772A true CN116507772A (en) | 2023-07-28 |
Family
ID=81601039
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202180075349.XA Pending CN116507772A (en) | 2020-11-16 | 2021-08-25 | Method for producing bleached pulp |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPWO2022102206A1 (en) |
| CN (1) | CN116507772A (en) |
| WO (1) | WO2022102206A1 (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005068567A (en) * | 2003-08-21 | 2005-03-17 | Oji Paper Co Ltd | Method for producing bleached pulp |
| JP2008088606A (en) * | 2006-10-03 | 2008-04-17 | Oji Paper Co Ltd | Method for producing bleached pulp |
| CN101443514A (en) * | 2006-05-17 | 2009-05-27 | 三菱瓦斯化学株式会社 | Process for producing bleached pulp |
| US20160257982A1 (en) * | 2015-03-04 | 2016-09-08 | Fpinnovations | Novel post-treatment to enhance the enzymatic hydrolysis of pretreated lignocellulosic biomass |
| CN110177909A (en) * | 2017-01-23 | 2019-08-27 | 纸、纸板和纤维素工业技术中心 | Method for bleached pulp |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105672018B (en) * | 2007-12-20 | 2018-09-11 | 三菱瓦斯化学株式会社 | The manufacturing method of bleached pulp |
| JP2011001637A (en) * | 2009-06-16 | 2011-01-06 | Mitsubishi Gas Chemical Co Inc | Method for producing bleached pulp |
| JP5712754B2 (en) * | 2011-04-13 | 2015-05-07 | 王子ホールディングス株式会社 | Method for producing dissolving pulp |
-
2021
- 2021-08-25 CN CN202180075349.XA patent/CN116507772A/en active Pending
- 2021-08-25 WO PCT/JP2021/031196 patent/WO2022102206A1/en active Application Filing
- 2021-08-25 JP JP2022561290A patent/JPWO2022102206A1/ja active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005068567A (en) * | 2003-08-21 | 2005-03-17 | Oji Paper Co Ltd | Method for producing bleached pulp |
| CN101443514A (en) * | 2006-05-17 | 2009-05-27 | 三菱瓦斯化学株式会社 | Process for producing bleached pulp |
| US20090183845A1 (en) * | 2006-05-17 | 2009-07-23 | Iori Tomoda | Process for producing bleached pulp |
| JP2008088606A (en) * | 2006-10-03 | 2008-04-17 | Oji Paper Co Ltd | Method for producing bleached pulp |
| US20160257982A1 (en) * | 2015-03-04 | 2016-09-08 | Fpinnovations | Novel post-treatment to enhance the enzymatic hydrolysis of pretreated lignocellulosic biomass |
| CN110177909A (en) * | 2017-01-23 | 2019-08-27 | 纸、纸板和纤维素工业技术中心 | Method for bleached pulp |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2022102206A1 (en) | 2022-05-19 |
| JPWO2022102206A1 (en) | 2022-05-19 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP5953909B2 (en) | Method for producing dissolving pulp | |
| CN101443514B (en) | Process for producing bleached pulp | |
| CN110552226B (en) | Method for producing bleached pulp | |
| JP4887900B2 (en) | Method for producing bleached pulp | |
| JP4893210B2 (en) | Method for producing bleached pulp | |
| AU2003216028A1 (en) | Process for bleaching lignocellulose-containing non-wood pulp | |
| CN116507772A (en) | Method for producing bleached pulp | |
| JP6187619B2 (en) | Method for producing dissolving pulp | |
| JP5471050B2 (en) | TCF bleaching method | |
| CN112127193A (en) | Production process for improving quality index of dissolving pulp by using bleaching process | |
| JP2011001637A (en) | Method for producing bleached pulp | |
| JP2011001636A (en) | Method for producing bleached pulp | |
| CA2737709A1 (en) | Pulp bleaching and alkaline extraction method | |
| CN114174589B (en) | Method for producing bleached pulp | |
| US8980051B2 (en) | Sulfonation of pulp produced by alkali pulping process | |
| JP3656905B2 (en) | Process for producing bleached pulp with improved fading | |
| JP5888151B2 (en) | Method for producing bleached pulp | |
| JP2000290887A (en) | Bleaching of lignocellulose | |
| JP2004169243A (en) | Method of producing bleached pulp for paper making | |
| JP2004339628A (en) | Method for producing bleached pulp | |
| JP4039308B2 (en) | Method for producing bleached pulp | |
| JPH05247864A (en) | Bleaching of cellulose pulp | |
| JP2002302888A (en) | Method of production for bleached pulp | |
| WO2000008251A1 (en) | An improved method for bleaching pulp | |
| JP2002173885A (en) | Method for producing bleached hardwood pulp |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |