CA1180510A - Methode de separation de la lignile residuaire de la pate chimique de cellulose - Google Patents

Methode de separation de la lignile residuaire de la pate chimique de cellulose

Info

Publication number: CA1180510A
Authority: CA; Canada
Prior art keywords: pulp; alkali; stage; oxygen gas; gas
Prior art date: 1981-03-23
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.): Expired

Application number

CA000399940A

Other languages

English (en)

Inventor

Hans O. Samuelson

Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Mo och Domsjo AB

Original Assignee

Mo och Domsjo AB

Priority date (The priority date 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 date listed.)

1981-03-23

Filing date

1982-03-31

Publication date

1985-01-08

1982-03-31 Application filed by Mo och Domsjo AB filed Critical Mo och Domsjo AB

1985-01-08 Application granted granted Critical

1985-01-08 Publication of CA1180510A publication Critical patent/CA1180510A/fr

Status Expired legal-status Critical Current

Links

238000000034 method Methods 0.000 title claims abstract description 84
230000008569 process Effects 0.000 title claims abstract description 54
229920002678 cellulose Polymers 0.000 title claims abstract description 53
239000001913 cellulose Substances 0.000 title claims abstract description 53
229920005610 lignin Polymers 0.000 title claims abstract description 17
239000000126 substance Substances 0.000 title abstract description 7
239000003513 alkali Substances 0.000 claims abstract description 76
238000011282 treatment Methods 0.000 claims abstract description 74
239000007789 gas Substances 0.000 claims abstract description 72
MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims abstract description 41
229910001882 dioxygen Inorganic materials 0.000 claims abstract description 40
QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 37
229910052760 oxygen Inorganic materials 0.000 claims abstract description 37
239000001301 oxygen Substances 0.000 claims abstract description 37
XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 30
230000003213 activating effect Effects 0.000 claims abstract description 26
230000004913 activation Effects 0.000 claims description 15
239000002699 waste material Substances 0.000 claims description 11
238000005406 washing Methods 0.000 claims description 8
230000009467 reduction Effects 0.000 claims description 7
229920002488 Hemicellulose Polymers 0.000 claims description 5
230000015556 catabolic process Effects 0.000 claims description 4
238000006731 degradation reaction Methods 0.000 claims description 4
238000004537 pulping Methods 0.000 claims description 3
239000012978 lignocellulosic material Substances 0.000 claims description 2
239000007791 liquid phase Substances 0.000 claims 1
239000012071 phase Substances 0.000 claims 1
MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 abstract description 75
150000001720 carbohydrates Chemical class 0.000 abstract description 6
235000014633 carbohydrates Nutrition 0.000 abstract description 6
239000000203 mixture Substances 0.000 abstract description 6
239000007844 bleaching agent Substances 0.000 abstract description 2
IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 60
MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 description 44
JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 description 44
HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 41
229910052757 nitrogen Inorganic materials 0.000 description 30
238000004061 bleaching Methods 0.000 description 29
238000006243 chemical reaction Methods 0.000 description 19
238000001994 activation Methods 0.000 description 15
ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 11
239000000460 chlorine Substances 0.000 description 11
229910052801 chlorine Inorganic materials 0.000 description 11
QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 9
235000008331 Pinus X rigitaeda Nutrition 0.000 description 8
235000011613 Pinus brutia Nutrition 0.000 description 8
241000018646 Pinus brutia Species 0.000 description 8
150000002500 ions Chemical class 0.000 description 7
239000011777 magnesium Substances 0.000 description 7
CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 6
239000007788 liquid Substances 0.000 description 6
230000007423 decrease Effects 0.000 description 5
239000011261 inert gas Substances 0.000 description 5
101150080656 DIO2 gene Proteins 0.000 description 4
DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 4
238000002474 experimental method Methods 0.000 description 4
239000011121 hardwood Substances 0.000 description 4
239000011734 sodium Substances 0.000 description 4
229910052708 sodium Inorganic materials 0.000 description 4
FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 3
LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 3
WFPZPJSADLPSON-UHFFFAOYSA-N dinitrogen tetraoxide Chemical compound [O-][N+](=O)[N+]([O-])=O WFPZPJSADLPSON-UHFFFAOYSA-N 0.000 description 3
238000001035 drying Methods 0.000 description 3
230000000694 effects Effects 0.000 description 3
229910052749 magnesium Inorganic materials 0.000 description 3
229960003390 magnesium sulfate Drugs 0.000 description 3
229910052943 magnesium sulfate Inorganic materials 0.000 description 3
235000019341 magnesium sulphate Nutrition 0.000 description 3
229940091250 magnesium supplement Drugs 0.000 description 3
238000002156 mixing Methods 0.000 description 3
239000011122 softwood Substances 0.000 description 3
241000218657 Picea Species 0.000 description 2
229920001131 Pulp (paper) Polymers 0.000 description 2
CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 2
239000002253 acid Substances 0.000 description 2
239000000654 additive Substances 0.000 description 2
230000008901 benefit Effects 0.000 description 2
239000003795 chemical substances by application Substances 0.000 description 2
238000010924 continuous production Methods 0.000 description 2
238000010411 cooking Methods 0.000 description 2
230000006378 damage Effects 0.000 description 2
230000029087 digestion Effects 0.000 description 2
230000003292 diminished effect Effects 0.000 description 2
229910001873 dinitrogen Inorganic materials 0.000 description 2
OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 description 2
238000000605 extraction Methods 0.000 description 2
JEIPFZHSYJVQDO-UHFFFAOYSA-N ferric oxide Chemical compound O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
ZZUFCTLCJUWOSV-UHFFFAOYSA-N furosemide Chemical compound C1=C(Cl)C(S(=O)(=O)N)=CC(C(O)=O)=C1NCC1=CC=CO1 ZZUFCTLCJUWOSV-UHFFFAOYSA-N 0.000 description 2
XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
238000011065 in-situ storage Methods 0.000 description 2
239000000543 intermediate Substances 0.000 description 2
238000004519 manufacturing process Methods 0.000 description 2
239000000463 material Substances 0.000 description 2
238000005259 measurement Methods 0.000 description 2
125000000449 nitro group Chemical group [O-][N+](*)=O 0.000 description 2
229920000642 polymer Polymers 0.000 description 2
239000000047 product Substances 0.000 description 2
230000035484 reaction time Effects 0.000 description 2
238000012360 testing method Methods 0.000 description 2
230000008016 vaporization Effects 0.000 description 2
HFGHRUCCKVYFKL-UHFFFAOYSA-N 4-ethoxy-2-piperazin-1-yl-7-pyridin-4-yl-5h-pyrimido[5,4-b]indole Chemical compound C1=C2NC=3C(OCC)=NC(N4CCNCC4)=NC=3C2=CC=C1C1=CC=NC=C1 HFGHRUCCKVYFKL-UHFFFAOYSA-N 0.000 description 1
SUBDBMMJDZJVOS-UHFFFAOYSA-N 5-methoxy-2-{[(4-methoxy-3,5-dimethylpyridin-2-yl)methyl]sulfinyl}-1H-benzimidazole Chemical compound N=1C2=CC(OC)=CC=C2NC=1S(=O)CC1=NC=C(C)C(OC)=C1C SUBDBMMJDZJVOS-UHFFFAOYSA-N 0.000 description 1
241000251468 Actinopterygii Species 0.000 description 1
239000004155 Chlorine dioxide Substances 0.000 description 1
101100353161 Drosophila melanogaster prel gene Proteins 0.000 description 1
241000196324 Embryophyta Species 0.000 description 1
241001547070 Eriodes Species 0.000 description 1
101100106077 Escherichia coli (strain K12) ygeI gene Proteins 0.000 description 1
241001397173 Kali <angiosperm> Species 0.000 description 1
241001072332 Monia Species 0.000 description 1
GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
241001296096 Probles Species 0.000 description 1
RJKFOVLPORLFTN-LEKSSAKUSA-N Progesterone Chemical compound C1CC2=CC(=O)CC[C@]2(C)[C@@H]2[C@@H]1[C@@H]1CC[C@H](C(=O)C)[C@@]1(C)CC2 RJKFOVLPORLFTN-LEKSSAKUSA-N 0.000 description 1
HFCYZXMHUIHAQI-UHFFFAOYSA-N Thidiazuron Chemical compound C=1C=CC=CC=1NC(=O)NC1=CN=NS1 HFCYZXMHUIHAQI-UHFFFAOYSA-N 0.000 description 1
-1 Thus Chemical compound 0.000 description 1
208000027418 Wounds and injury Diseases 0.000 description 1
240000008042 Zea mays Species 0.000 description 1
235000005824 Zea mays ssp. parviglumis Nutrition 0.000 description 1
235000002017 Zea mays subsp mays Nutrition 0.000 description 1
230000009471 action Effects 0.000 description 1
238000004458 analytical method Methods 0.000 description 1
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 1
150000004056 anthraquinones Chemical class 0.000 description 1
239000007900 aqueous suspension Substances 0.000 description 1
125000003118 aryl group Chemical group 0.000 description 1
238000010923 batch production Methods 0.000 description 1
238000009530 blood pressure measurement Methods 0.000 description 1
239000006227 byproduct Substances 0.000 description 1
125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 1
238000007084 catalytic combustion reaction Methods 0.000 description 1
230000008859 change Effects 0.000 description 1
238000005660 chlorination reaction Methods 0.000 description 1
235000019398 chlorine dioxide Nutrition 0.000 description 1
235000005822 corn Nutrition 0.000 description 1
230000006866 deterioration Effects 0.000 description 1
239000000539 dimer Substances 0.000 description 1
238000010438 heat treatment Methods 0.000 description 1
208000014674 injury Diseases 0.000 description 1
239000013067 intermediate product Substances 0.000 description 1
238000002386 leaching Methods 0.000 description 1
VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 1
239000000347 magnesium hydroxide Substances 0.000 description 1
229910001862 magnesium hydroxide Inorganic materials 0.000 description 1
230000014759 maintenance of location Effects 0.000 description 1
230000003340 mental effect Effects 0.000 description 1
239000003471 mutagenic agent Substances 0.000 description 1
231100000707 mutagenic chemical Toxicity 0.000 description 1
APVPOHHVBBYQAV-UHFFFAOYSA-N n-(4-aminophenyl)sulfonyloctadecanamide Chemical compound CCCCCCCCCCCCCCCCCC(=O)NS(=O)(=O)C1=CC=C(N)C=C1 APVPOHHVBBYQAV-UHFFFAOYSA-N 0.000 description 1
238000006386 neutralization reaction Methods 0.000 description 1
230000003472 neutralizing effect Effects 0.000 description 1
229910017604 nitric acid Inorganic materials 0.000 description 1
229940099990 ogen Drugs 0.000 description 1
230000001590 oxidative effect Effects 0.000 description 1
238000001139 pH measurement Methods 0.000 description 1
150000002978 peroxides Chemical class 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
238000003918 potentiometric titration Methods 0.000 description 1
238000001556 precipitation Methods 0.000 description 1
238000003825 pressing Methods 0.000 description 1
238000012545 processing Methods 0.000 description 1
238000000746 purification Methods 0.000 description 1
239000011541 reaction mixture Substances 0.000 description 1
238000007430 reference method Methods 0.000 description 1
230000001105 regulatory effect Effects 0.000 description 1
239000010865 sewage Substances 0.000 description 1
241000894007 species Species 0.000 description 1
238000003860 storage Methods 0.000 description 1
238000004448 titration Methods 0.000 description 1
238000012546 transfer Methods 0.000 description 1
238000009827 uniform distribution Methods 0.000 description 1
239000002023 wood 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
- D21C9/1005—Pretreatment of the pulp, e.g. degassing the pulp
- 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
- D21C9/1068—Bleaching ; Apparatus therefor with O2
- 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

Landscapes

Life Sciences & Earth Sciences (AREA)
Engineering & Computer Science (AREA)
Wood Science & Technology (AREA)
Paper (AREA)

CA000399940A 1981-03-23 1982-03-31 Methode de separation de la lignile residuaire de la pate chimique de cellulose Expired CA1180510A (fr)

Applications Claiming Priority (2)

Application Number	Priority Date	Filing Date	Title
SE8101815A SE425674B (sv)	1981-03-23	1981-03-23	Forfarande for delignifiering av cellulosamassa med kvevedioxid och syrgas
SE81-01815-2		1981-03-31

Publications (1)

Publication Number	Publication Date
CA1180510A true CA1180510A (fr)	1985-01-08

Family

ID=20343394

Family Applications (1)

Application Number	Title	Priority Date	Filing Date
CA000399940A Expired CA1180510A (fr)	1981-03-23	1982-03-31	Methode de separation de la lignile residuaire de la pate chimique de cellulose

Country Status (6)

Country	Link
JP (1)	JPS57161185A (fr)
AU (1)	AU550433B2 (fr)
CA (1)	CA1180510A (fr)
FR (1)	FR2502203A1 (fr)
NZ (1)	NZ199697A (fr)
SE (1)	SE425674B (fr)

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number	Priority date	Publication date	Assignee	Title
GB1505070A (en) *	1974-06-11	1978-03-22	Canadian Ind	Process for bleaching of lignocellulosic material
CA1070909A (fr) *	1976-05-04	1980-02-05	Canadian Industries Limited	Delignification au bioxyde d'azote et a l'oxygene

1981
- 1981-03-23 SE SE8101815A patent/SE425674B/sv not_active IP Right Cessation
1982
- 1982-02-11 NZ NZ199697A patent/NZ199697A/en unknown
- 1982-03-05 AU AU81151/82A patent/AU550433B2/en not_active Ceased
- 1982-03-08 JP JP57037131A patent/JPS57161185A/ja active Granted
- 1982-03-23 FR FR8204875A patent/FR2502203A1/fr active Granted
- 1982-03-31 CA CA000399940A patent/CA1180510A/fr not_active Expired

Also Published As

Publication number	Publication date
FR2502203A1 (fr)	1982-09-24
NZ199697A (en)	1986-01-24
AU550433B2 (en)	1986-03-20
AU8115182A (en)	1982-09-30
JPS57161185A (en)	1982-10-04
JPS6360158B2 (fr)	1988-11-22
SE425674B (sv)	1982-10-25
FR2502203B1 (fr)	1984-11-23
SE8101815L (fr)	1982-09-24

Legal Events

Date	Code	Title	Description
2002-01-09	MKEC	Expiry (correction)
2002-03-31	MKEX	Expiry

Publication	Publication Date	Title
US4222819A (en)	1980-09-16	Process for the acid bleaching of cellulose pulp with peroxides
US5310458A (en)	1994-05-10	Process for bleaching lignocellulose-containing pulps
FI111964B (fi)	2003-10-15	Menetelmä lignoselluloosapitoisen massan valkaisemiseksi
DE69206313T2 (de)	1996-04-18	Verfahren zum Bleichen von Lignocellulose enthaltendem Material.
DE3017712C2 (de)	1986-11-06	Verfahren zur alkalischen Extraktion von Fasermaterial enthaltenden Cellulosesuspensionen nach Behandlung mit Chlor oder Chlordioxid oder Mischungen davon
CA2040871C (fr)	1997-05-20	Procede de blanchiment de materiau contenant de la lignocellulose
CA1180509A (fr)	1985-01-08	Procede d'activation de la pate cellulosique avec du no et/ou du no.sub.2, avec de l'oxygene et en presence d'acide nitrique, et de delignification et de blanchiment de la patecellulosique activee
SI9110206A (sl)	1998-02-28	Postopek za beljenje celuloze za umetna vlakna brez klora
EP0395792A2 (fr)	1990-11-07	Procédé de blanchiment de pâte
CA1175610A (fr)	1984-10-09	Blanchiment de pate pour cellulose a l'aide d'oxygene gazeux en presence d'alcalis
US5645687A (en)	1997-07-08	Process for manufacturing bleached pulp with reduced chloride production
CA1147909A (fr)	1983-06-14	Methode de defibrage et de blanchiment de la pate de cellulose
CA1180510A (fr)	1985-01-08	Methode de separation de la lignile residuaire de la pate chimique de cellulose
US4750973A (en)	1988-06-14	Process for reducing carbohydrate losses in the sulfate pulping of wood by pretreating the wood with oxygen and nitrogen oxides
CZ132895A3 (en)	1996-01-17	Bleaching process of pulp containing ligno-cellulose
CA2088281A1 (fr)	1993-08-01	Procede de delignification de la cellulose brute
DE19729155A1 (de)	1998-01-15	Verfahren zur Herstellung von Pulpe
EP0185858B1 (fr)	1988-05-04	Procédé de délignification de pâtes-sulfates
SU1730299A1 (ru)	1992-04-30	Способ получени целлюлозы дл химической переработки
CA1149111A (fr)	1983-07-05	Methode de defibrage et de blanchiment de la pate de cellulose
RU2009279C1 (ru)	1994-03-15	Способ подготовки льняной ровницы к мокрому прядению
NZ198925A (en)	1984-09-28	Method for bleaching cellulose pulp using nitrogen oxides and oxygen followed by an alkali treatment
NO159542B (no)	1988-10-03	Fremgangsmaate ved delignifisering av cellulosemasse.
JPWO1994017237A1 (ja)	1995-03-02	酵素による化学パルプの漂白前処理方法
CA2130906A1 (fr)	1994-08-04	Methode pour le traitement enzymatique de la pate chimique avant le blanchiment