EP0191756B1 - Multi peroxide stage mechanical pulp bleaching - Google Patents
Multi peroxide stage mechanical pulp bleaching Download PDFInfo
- Publication number
- EP0191756B1 EP0191756B1 EP86890030A EP86890030A EP0191756B1 EP 0191756 B1 EP0191756 B1 EP 0191756B1 EP 86890030 A EP86890030 A EP 86890030A EP 86890030 A EP86890030 A EP 86890030A EP 0191756 B1 EP0191756 B1 EP 0191756B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- pulp
- bleaching
- peroxide
- mechanical
- stage
- 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.)
- Expired
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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
- D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
Definitions
- the invention relates to a method of obtaining high brightness lignocellulose pulp comprising the steps of subjecting a mechanical lignocellulose . pulp to peroxide bleaching and a hydrosulfite bleaching sequence, and to a high brightness mechanical lignocellulose pulp.
- Typical conventional bleaching sequences for the bleaching of mechanical pulps such as mechanical pulp, chemimechanical pulp (CMP), thermomechanical pulp (TMP) and chemither- momechanical pulp (CTMP) comprise peroxide (P), hydrosulfite (T), or P-T sequences.
- Reductive bleaching with hydrosulfites is also commonly practiced in a single stage.
- a P-T bleaching sequence which gives brightness in the range of about 74-78% ISO.
- the contribution to brightness of the final T stage is gradually reduced as the charge of peroxide is increased in order to boost final brightness.
- the invention as claimed is intended to further improve the result of treatment without adding further steps to the process.
- the T stage does produce a substantial brightening effect, on the order of 2-4 ISO units.
- the contribution from the hydrosulfite stage is very small (less than 2 ISO units) at the 80 + ISO level.
- the method is characterized by subjecting the mechanical pulp to a first peroxide bleaching, and then to a second peroxide bleaching, and then to the hydrosulfite bleaching sequence, to produce a bleached mechanical pulp. More than two peroxide stages may be provided, and the sequence of steps preferably practiced sequentially. Preferably the pulp is pressed between the stages to partially remove interstitial pulp liquor. This removed liquor (filtrate) is normally reused for dilution in preceding stages, orforchemical recovery. During the practice of all of steps the pulp maintains a consistency of between 8-50%, although after pressing it is typically diluted (e.g. to between 8-15%). During each actual bleaching stage the consistency is between 8-30%.
- the invention also relates to a mechanical pulp having high brightness, and produced by the practice of the aforementioned sequence of steps. According to the invention, a mechanical pulp is produced having a brightness of 83% ISO (or greater).
- a mechanical lignocellulose pulp as used in the specification and claims is intended to encompass conventional mechanical pulps, such as ground wood and refiner pulps, e.g. CMP, CTMP, and TMP.
- Figure 1 illustrates the production of a mechanical pulp in a typical mechanical pulping process station 10, which includes the use of refiners, and other pulping process stages as desired.
- a mechanical lignocellulose pulp is produced in station 10, it is subjected to a first sodium or hydrogen peroxide bleaching P 1 , as indicated by reference numeral 12 in Figure 1.
- Peroxide bleaching is accomplished utilizing conventional equipment, and conventional bleaching conditions for peroxide bleaching of mechanical pulps (e.g.. 45-90°C, 15-240 minutes).
- a typical form such equipment can take is illustrated schematically in Figure 3 wherein the pulp is fed to a mixer 14, the peroxide, sodium hydroxide, and buffering and stabilizing agents or the like (such as sodium silicate and MgS0 4 ) are added.
- the consistency of the pulp may be increased in screw press 15, and ultimately the pulp is fed to bleaching tower 16.
- Bleaching would typically be accomplished at a consistency of about 8-30%, preferably about 12-25%.
- the pulp is passed to the second peroxide stage P 2 , indicated by reference numeral 18 in Figure 1. There it is subjected to another typical peroxide bleaching sequence.
- Other peroxide bleaching sequences after stage 12 e.g. P 3 , P 4 , etc. may be provided.
- press station 19 is disposed between the peroxide bleaching sequence stages 12, 18.
- the pulp is pressed to a high consistency (e.g. on the order of 30-50%) before the bleach liquid for the subsequent peroxide stage 18 is added.
- pressing in press station 19' preferably is practiced after stage 18.
- the pulp is subjected to a hydrosulfite bleaching, as illustrated schematically by reference numeral 20 in Figure 1.
- the conditions in the hydrosulfite bleaching stage 20 are conventional (e.g. 45-90°C, 10-60 min.) except that it is preferred that the bleaching be practiced with a pulp consistency of between about 8-30%, preferably between about 8-15%.
- Hydrosulfite bleaching of medium consistency mechanical pulps is illustrated in EP-A- * 0,155,928, and the equipment and processes illustrated therein may be utilized in the practice of bleaching 20.
- FIG. 4 schematically illustrates one form of the typical equipment that could be utilized in the practice of stage 20, wherein the pulp, after having been pressed and diluted to about 8-15% consistency, is mixed with hydrosulfite and other chemicals, such as buffering, chelating, and sequestering agents.
- the pulp is fluidized by the mixer 22, and then passes to conventional upflow tower 24.
- the bleached mechanical pulp produced according to the sequence illustrated in Figure 1 has high brightness; brightness on the order of about 83% ISO units, or more, can be achieved. Almost as high a brightness can be achieved if a peroxide stage is utilized both before and after a hydrosulfite stage. This is shown schematically in Figure 5 wherein T stage 20' is between P 1 stage 12' and P 2 stage 18'.
- T stage 20' is between P 1 stage 12' and P 2 stage 18'.
- a P-T sequence was practiced on unbleached CTMP pulp having 53.5% ISO, 160/110 (cold/hot) ml C.S.F. (millimeters, Canadian Standard Free- ness) containing 0.4% DCM-extract (a measure of the amount of resin), 92 ppm manganese, and 9 ppm iron.
- the pulp was pretreated with 0.2% DTPA (pentasodium salt of diethylenetriamine pentaacetic acid on bone dry (BD) pulp at 3% consistency and 60°C. The temperature in both the P and T stages was 80°C, and the pulp consistency was 15% in both stages.
- DTPA dipentasodium salt of diethylenetriamine pentaacetic acid on bone dry (BD) pulp
- the treatment time in the peroxide stage was 180 minutes using 3% sodium silicate and 0.2% MgS0 4 for buffering and stabilizing the peroxide liquid.
- the reaction time was 30 minutes, using 1% hydrosulfite which was all consumed. The following results were obtained:
- the pulp was pressed and the pH was reduced by the addition of S0 2 water, the reduction practiced so that the pH was about 5.5-6.0 just prior to the hydrosulfite stage, and the pulp was diluted as necessary in order to maintain the consistency throughout the actual bleaching stages at about 15%.
- the hydrosulfite stage was between two peroxide stages (see Fig. 5).
- the pulp, and general conditions, were the same as for Example 2, with the following results:
- the final pulp brightness of almost 83 ISO (82.6) was suprisingly high, although not quite as high as.the one for the sequence in Example 2.
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Abstract
Description
- The invention relates to a method of obtaining high brightness lignocellulose pulp comprising the steps of subjecting a mechanical lignocellulose . pulp to peroxide bleaching and a hydrosulfite bleaching sequence, and to a high brightness mechanical lignocellulose pulp.
- Typical conventional bleaching sequences for the bleaching of mechanical pulps, such as mechanical pulp, chemimechanical pulp (CMP), thermomechanical pulp (TMP) and chemither- momechanical pulp (CTMP) comprise peroxide (P), hydrosulfite (T), or P-T sequences.
- Conventional peroxide bleaching, with sodium or hydrogen peroxide, is typically accomplished at a consistency of about 12-30%. Single stage peroxide treatment is most common. However, it has been known to use two stage peroxide bleaching (P-P) for medium brightness mechanical pulps, that is having a brightness of about 75-80% ISO.
- Reductive bleaching with hydrosulfites (dithionites) is also commonly practiced in a single stage. However it has been known to use a P-T bleaching sequence, which gives brightness in the range of about 74-78% ISO. In a P-T sequence, the contribution to brightness of the final T stage is gradually reduced as the charge of peroxide is increased in order to boost final brightness.
- From EP-A-0 187477 a multistage process for bleaching lignocellulose pulp is known whereby the pulp is treated sequentially with a peroxygen compound, a reducing compound, e.g. sodium hydrosulfite, and a final peroxygen compound to achieve higher brightness levels, i.e. a P-T-P sequence.
- The invention as claimed is intended to further improve the result of treatment without adding further steps to the process.
- According to the present invention it has been surprisingly found that where the peroxide treatment is split into two, or more, stages, the T stage does produce a substantial brightening effect, on the order of 2-4 ISO units. In a typical P-T sequence, the contribution from the hydrosulfite stage is very small (less than 2 ISO units) at the 80 + ISO level.
- According to the present invention the method is characterized by subjecting the mechanical pulp to a first peroxide bleaching, and then to a second peroxide bleaching, and then to the hydrosulfite bleaching sequence, to produce a bleached mechanical pulp. More than two peroxide stages may be provided, and the sequence of steps preferably practiced sequentially. Preferably the pulp is pressed between the stages to partially remove interstitial pulp liquor. This removed liquor (filtrate) is normally reused for dilution in preceding stages, orforchemical recovery. During the practice of all of steps the pulp maintains a consistency of between 8-50%, although after pressing it is typically diluted (e.g. to between 8-15%). During each actual bleaching stage the consistency is between 8-30%.
- The invention also relates to a mechanical pulp having high brightness, and produced by the practice of the aforementioned sequence of steps. According to the invention, a mechanical pulp is produced having a brightness of 83% ISO (or greater). I
- It is the primary object of the present invention is produce a high brightness mechanical pulp. This and other objects of the invention will become clearfrom a description of the detailed description of the invention, and from the appended claims.
-
- Figure 1 is a schematic view illustrating the steps in the practice of an exemplary method according to the present invention;
- Figure 2 is a schematic indicating a preferred modification of the method of Figure 1;
- Figure 3 is a schematic representation of exemplary apparatus utilized in the practice of one of the peroxide stages in the method of Figure 1;
- Figure 4 is a schematic representation of exemplary equipment utilizable in the practice of the hydrosulfite bleaching stage of Figure 1; and
- Figure 5 is a schematic representation of a modification of the method of Figure 1 wherein the T stage is between two P stages.
- The invention is useful is increasing the brightness of all types of mechanical pulps. The term "a mechanical lignocellulose pulp" as used in the specification and claims is intended to encompass conventional mechanical pulps, such as ground wood and refiner pulps, e.g. CMP, CTMP, and TMP. Figure 1 illustrates the production of a mechanical pulp in a typical mechanical pulping process station 10, which includes the use of refiners, and other pulping process stages as desired.
- After a mechanical lignocellulose pulp is produced in station 10, it is subjected to a first sodium or hydrogen peroxide bleaching P1, as indicated by
reference numeral 12 in Figure 1. Peroxide bleaching is accomplished utilizing conventional equipment, and conventional bleaching conditions for peroxide bleaching of mechanical pulps (e.g.. 45-90°C, 15-240 minutes). A typical form such equipment can take is illustrated schematically in Figure 3 wherein the pulp is fed to amixer 14, the peroxide, sodium hydroxide, and buffering and stabilizing agents or the like (such as sodium silicate and MgS04) are added. If desired after mixing inmixer 14, the consistency of the pulp may be increased inscrew press 15, and ultimately the pulp is fed to bleachingtower 16. Bleaching would typically be accomplished at a consistency of about 8-30%, preferably about 12-25%. - In the present embodiment after treatment in stage P1, the pulp is passed to the second peroxide stage P2, indicated by
reference numeral 18 in Figure 1. There it is subjected to another typical peroxide bleaching sequence. Other peroxide bleaching sequences after stage 12 (e.g. P3, P4, etc.) may be provided. - In the preferred embodiment of the invention, between the P, and P2 stages the mechanical pulp is pressed. This is illustrated schematically in Figure 2 wherein a
press station 19 is disposed between the peroxidebleaching sequence stages press station 19, the pulp is pressed to a high consistency (e.g. on the order of 30-50%) before the bleach liquid for thesubsequent peroxide stage 18 is added. Also as indicated in Figure 2, pressing in press station 19' preferably is practiced afterstage 18. - After the second (or subsequent, i.e. last) peroxide bleaching sequence, the pulp is subjected to a hydrosulfite bleaching, as illustrated schematically by
reference numeral 20 in Figure 1. The conditions in thehydrosulfite bleaching stage 20 are conventional (e.g. 45-90°C, 10-60 min.) except that it is preferred that the bleaching be practiced with a pulp consistency of between about 8-30%, preferably between about 8-15%. Hydrosulfite bleaching of medium consistency mechanical pulps is illustrated in EP-A-*0,155,928, and the equipment and processes illustrated therein may be utilized in the practice of bleaching 20. Figure 4 schematically illustrates one form of the typical equipment that could be utilized in the practice ofstage 20, wherein the pulp, after having been pressed and diluted to about 8-15% consistency, is mixed with hydrosulfite and other chemicals, such as buffering, chelating, and sequestering agents. The pulp is fluidized by themixer 22, and then passes toconventional upflow tower 24. - Between
stations station 20, pressing of the pulp can be practiced between thestations - The bleached mechanical pulp produced according to the sequence illustrated in Figure 1 has high brightness; brightness on the order of about 83% ISO units, or more, can be achieved. Almost as high a brightness can be achieved if a peroxide stage is utilized both before and after a hydrosulfite stage. This is shown schematically in Figure 5 wherein T stage 20' is between P1 stage 12' and P2 stage 18'. The following examples illustrate the enhanced brightness that can be achieved by the practice of the method of the invention.
- A P-T sequence was practiced on unbleached CTMP pulp having 53.5% ISO, 160/110 (cold/hot) ml C.S.F. (millimeters, Canadian Standard Free- ness) containing 0.4% DCM-extract (a measure of the amount of resin), 92 ppm manganese, and 9 ppm iron. For the peroxide stage, the pulp was pretreated with 0.2% DTPA (pentasodium salt of diethylenetriamine pentaacetic acid on bone dry (BD) pulp at 3% consistency and 60°C. The temperature in both the P and T stages was 80°C, and the pulp consistency was 15% in both stages. The treatment time in the peroxide stage was 180 minutes using 3% sodium silicate and 0.2% MgS04 for buffering and stabilizing the peroxide liquid. In the T stage the reaction time was 30 minutes, using 1% hydrosulfite which was all consumed. The following results were obtained:
-
- Practicing the present invention utilizing the same pulp as described in Example 1, pretreated in the same way, with the same buffering and stabilizing agents, with the same temperatures (i.e. 80°C) and consistency (i.e. 15% in all stages), and with a reaction time of 180 minutes in each peroxide stage and 30 min. in the hydrosulfite stage (1 %, which was all consumed), the following results were obtained:
- Between the second peroxide stage and the hydrosulfite stage the pulp was pressed and the pH was reduced by the addition of S02 water, the reduction practiced so that the pH was about 5.5-6.0 just prior to the hydrosulfite stage, and the pulp was diluted as necessary in order to maintain the consistency throughout the actual bleaching stages at about 15%.
- In this example the hydrosulfite stage was between two peroxide stages (see Fig. 5). The pulp, and general conditions, were the same as for Example 2, with the following results:
- It will thus be seen that according to the present invention a mechanical pulp having high brightness is produced, with a synergistic effect being achieved in pulp brightness by utilizing multi- peroxide stages prior to a hydrosulfite stage.
Claims (9)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT86890030T ATE39714T1 (en) | 1985-02-15 | 1986-02-12 | MULTI-STAGE PEROXIDE BLEACHING OF A MECHANICAL PULP. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US70200085A | 1985-02-15 | 1985-02-15 | |
US702000 | 1985-02-15 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0191756A1 EP0191756A1 (en) | 1986-08-20 |
EP0191756B1 true EP0191756B1 (en) | 1989-01-04 |
Family
ID=24819495
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP86890030A Expired EP0191756B1 (en) | 1985-02-15 | 1986-02-12 | Multi peroxide stage mechanical pulp bleaching |
Country Status (8)
Country | Link |
---|---|
EP (1) | EP0191756B1 (en) |
JP (1) | JPS61245392A (en) |
AT (1) | ATE39714T1 (en) |
BR (1) | BR8600637A (en) |
DE (1) | DE3661641D1 (en) |
FI (1) | FI85729C (en) |
NO (1) | NO166244C (en) |
SE (1) | SE8600615L (en) |
Families Citing this family (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
SE455203B (en) * | 1986-10-20 | 1988-06-27 | Eka Nobel Ab | PROCEDURE FOR THE CONTROL OF PEROXID WHEATING OF MASS |
FR2622221A1 (en) * | 1987-10-22 | 1989-04-28 | Atochem | PROCESS FOR BLEACHING PASTA |
FR2639371B1 (en) * | 1988-11-24 | 1995-04-14 | Atochem | PROCESS FOR THE BLEACHING OF DEINKED PASTA |
CA1340348C (en) * | 1989-03-23 | 1999-01-26 | Michel Barbe | Bleaching process for the production of high bright pulps |
JPH076148B2 (en) * | 1989-06-27 | 1995-01-30 | 新王子製紙株式会社 | Bleaching method for lignocellulosic material |
BE1004630A3 (en) * | 1990-10-17 | 1992-12-22 | Interox Internat Sa | Method for preservation of strength characteristics of paper pulp chemicals. |
GB9212926D0 (en) * | 1992-06-18 | 1992-07-29 | Morton Int Inc | Method of bleaching paper pulp |
US5464501A (en) * | 1993-04-06 | 1995-11-07 | Societe Anonyme Pour L'etude Et L'exploitation L'air Liquide, Des Procedes Georges Claude | Bleaching recycled pulp with a reductive-oxidative sequence |
IT1296947B1 (en) * | 1997-12-10 | 1999-08-03 | Donato Fausto De | COMPOSITION FOR WHITENING THE WOOD PASTE AND RELATED PROCEDURE |
EP1418269B1 (en) | 2002-11-05 | 2009-02-11 | Rohm And Haas Company | Method for brightening virgin mechanical pulp |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0187477A1 (en) * | 1984-12-21 | 1986-07-16 | Pulp and Paper Research Institute of Canada | Multistage brightening of high yield and ultra high-yield wood pulps |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1820502A (en) * | 1928-06-30 | 1931-08-25 | Champion Fibre Company | Bleaching cellulose pulp |
US2290601A (en) * | 1940-02-16 | 1942-07-21 | Du Pont | Bleaching of ground wood pulp with preliminary bisulphite treatment |
US2862784A (en) * | 1955-03-04 | 1958-12-02 | Virginia Smelting Company | Oxidative-reductive multi-stage bleaching of ground wood pulp |
JPS5679798A (en) * | 1979-12-03 | 1981-06-30 | Mitsubishi Gas Chemical Co | Production of bleaching machine pulp |
JPS575992A (en) * | 1980-06-04 | 1982-01-12 | Mitsubishi Gas Chemical Co | Bleaching of high yield pulp by peroxide |
-
1986
- 1986-02-12 DE DE8686890030T patent/DE3661641D1/en not_active Expired
- 1986-02-12 EP EP86890030A patent/EP0191756B1/en not_active Expired
- 1986-02-12 SE SE8600615A patent/SE8600615L/en unknown
- 1986-02-12 AT AT86890030T patent/ATE39714T1/en not_active IP Right Cessation
- 1986-02-14 JP JP61030582A patent/JPS61245392A/en active Pending
- 1986-02-14 NO NO860546A patent/NO166244C/en unknown
- 1986-02-14 FI FI860688A patent/FI85729C/en not_active IP Right Cessation
- 1986-02-14 BR BR8600637A patent/BR8600637A/en not_active IP Right Cessation
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0187477A1 (en) * | 1984-12-21 | 1986-07-16 | Pulp and Paper Research Institute of Canada | Multistage brightening of high yield and ultra high-yield wood pulps |
Also Published As
Publication number | Publication date |
---|---|
FI860688A (en) | 1986-08-16 |
DE3661641D1 (en) | 1989-02-09 |
NO860546L (en) | 1986-08-18 |
JPS61245392A (en) | 1986-10-31 |
EP0191756A1 (en) | 1986-08-20 |
ATE39714T1 (en) | 1989-01-15 |
SE8600615L (en) | 1986-08-16 |
FI85729C (en) | 1992-05-25 |
NO166244B (en) | 1991-03-11 |
FI85729B (en) | 1992-02-14 |
FI860688A0 (en) | 1986-02-14 |
NO166244C (en) | 1991-06-19 |
BR8600637A (en) | 1986-11-04 |
SE8600615D0 (en) | 1986-02-12 |
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