CA1101616A - Method of producing coniferous wood celluloses by the sulphite process on a magnesium basis - Google Patents
Method of producing coniferous wood celluloses by the sulphite process on a magnesium basisInfo
- Publication number
- CA1101616A CA1101616A CA301,780A CA301780A CA1101616A CA 1101616 A CA1101616 A CA 1101616A CA 301780 A CA301780 A CA 301780A CA 1101616 A CA1101616 A CA 1101616A
- Authority
- CA
- Canada
- Prior art keywords
- magnesium
- chips
- celluloses
- wood
- solution
- 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
Links
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
- D21C1/00—Pretreatment of the finely-divided materials before digesting
- D21C1/06—Pretreatment of the finely-divided materials before digesting with alkaline reacting compounds
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C3/00—Pulping cellulose-containing materials
- D21C3/04—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides
- D21C3/06—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites sulfites
- D21C3/10—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites sulfites magnesium bisulfite
Abstract
ABSTRACT
Method of producing spruce wood celluloses by the sulphite process on a magnesium basis, in which spruce wood hogged chips are pretreated with milk of magnesium hydroxide or with magnesium sulphate solution at room temperature in a pretreatment stage and, after intermediate storage, are decomposed with a magnesium bisulphite solution at pH values of around 4.
Method of producing spruce wood celluloses by the sulphite process on a magnesium basis, in which spruce wood hogged chips are pretreated with milk of magnesium hydroxide or with magnesium sulphate solution at room temperature in a pretreatment stage and, after intermediate storage, are decomposed with a magnesium bisulphite solution at pH values of around 4.
Description
The invention relates to a method of producing spruce wood celluloses by the sulphite process on a magnesium basis.
Certain optimum properties of the cellulose are desirable when producing spruce wood celluloses for the paper industry. It is important to decompose the wood as gently as possible in order that a high proportion of the carbohydrates of the wood is retained in the cellulose and the strength of the fibres is reduced as little as possible during the decomposition of the wood. In order to keep the outlay for bleaching as low as possible, it is further desirable to produce celluloses which already exhibit high whiteness values in the unbleached state.
The production of celluloses is dominated by two processes and their modifications, namely the sulphate process and the sulphite process. The principal advantage of the sulphate process compared to the sulphite process are the higher strength of the celluloses thereby produced. The principal advantages of the sulphite process lie in the higher whiteness values of the unbleached celluloses and their easier ; bleachability. Attempts have been made to discover methods whereby celluloses could be produced with both strong and readily bleachable fibres. It is possible to produce celluloses with such specific properties by modifications of the sulphite process.
This is possible by a known two-stage process, whereby decomposition is performed in the pH range of 4 in the first stage and the boiling is continued at higher pH values in the second stage.
Other sulphite processes aim at increasing the yield of the spruce wood decomposition. According to a known method of this type, boiling is performed in the neutral or weakly acid pH range in a first stage, whereby the glucomannan fraction of the wood becomes stabilised and does not also pass into solution under the conditions of the second stage.
~k This glucomannan stabilisation is also possible at room temperature if the pH value of the solution is raised and the re-action time prolonged. According to one described method, the wood was pretreated with dilute NaOH at low temperatures and then decomposed with a sodium bisulphite solution. According to an-other mode of production wood chips were treated with mil~c of lime and then decomposed with a calcium bisulphite solution. In-creased yiel~s o~ between 2 and 7% were achieved by these methods mentioned, depending upon the intensity of the pretreatment.
However, the technological properties of the celluloses thus pro- ~:
duced were no better, in part actually poorer than those of the celluloses produced by sulphite processes without pretreatment.
Celluloses with high strength values, such as can be produced by two-stage proces$es, have low yields. Furthermore, a two-stage process is so complicated that it has not been adopted industrial-ly. ,~
Object of the invention is a method of producing spruce 1;
wood celluloses by sulphite process on a magnesium basis, whereby the cellulose produced exhibits both high strength va]ues and good bleachability of the fibres. At the same time, a high yield ~rom the spruce wood decomposition is also required.
According to the invention this aim is achieved by a method of producing coniferous wood celluloses by the sulphite process on a magnesium basis comprising the steps o~:
~ a) treating hogged spruce wood chips by immersing them in, or spraying them with, either (1) a suspension of magnesium hydroxide having an MgO content of 2 to 3% until the chips con-tain 2 to 3% MgO in the ~orm of hydroxide, or (2) a solution having 5% magnesium sulphate until the chips contain about 5%
magnesium sulphate/bone dry wood;
(b) storing the thus treated chips at room temperature for approximately 24 hours;
~3 :J
6~
.~,~
(c) inducting the treated and stored chips in a digest-er with magnesium bisulphite solution and heating the resulting batch to a cooking temperature of 160 - 165C; and (d) cooking the chips in the digester for 2.5 - 3 hours at a temperature between 160 and 165C in a magnesium bisul-phite liquor having a pH value of about 4 and a total SO2 concen-tration of 4%, the liquor ratio during cooking being 5:1.
By this method, spruce wood celluloses are produced wlth yields which are up to 5 to 8~ higher than -those of compar-able sulphate cellulose processes. These high yields are alsomainta~ned in the bleaching. The celluloses thus produced are very readily bleachable and already have a high whiteness value in the unbleached state.
,:
.
~ - 4a -,~ ' L6~6 They can be ground more easily than sulphate celluloses.
Bursting and tensile strength are at least as high as for sulphate celluloses. The folding strength of the unground celluloses is higher than for sulphate celluloses, that of the ground celluloses slightly lower. The repeated tearing strength values are also slightly lower than for sulphate celluloses. The method requires no additional thermal energy compared to the magnesium bisulphite ` pracess (pH 4.0) because the pretreatment occurs at room temperature. , Moreover, no additional chemicals are required for the pretreatment with m11k of magnesium hydroxide, because the magnesium hydroxide already adsorbed by the wood is deducted in preparing the boiling ', acid. ~here magnesium sulphate is used for the pretreatment, the , ' magnesium sulphate which is required as make-up in the chemical circuit in any case can be used.
The object of the invention is more fully described and explained hereinbelow with reference to three exemplary embodiments '~' of the method according to the i,nvention:
1st Example Spruce wood hogged chips are treated with a mil k of magnesium hydroxlde having an MgO content of 2-3%, either by being immersed in the milk or by being sprayed with the milk until they contain 2-3%
of magnesi~um oxide in the form of hydroxide. The chips are then stored at room temperature for approximately 24 hours and then decomposed wi,th a magnesium bisulphite solution having a total S02 concentraticn of 4%. The liquor ratio here is 5:1. The pH value of the decomposing solution is initially about 2. By the reaction of the magnesium hydroxide already adsorbed in the pretreatment stage with the bisulphite solution it rises to about pH 4 before the maximum temperature of 160-165C is attained. At this maximum temperature the decomposition is performed in 2 1/2 - 3 hours up to Kappa numbers , ~
6~6 between 30 and 40. The cellulose yield is approximately 54%. The cellulose has the following technological values:
Grinding Grinding Tearing Bursting Fold No. Breaking Time fineness length strength strength min SR m2 p - 16 10 420 61.1 2 620 94.0 21.5 10 935 79.4 1 900 92.6 37.5 11 535 80.1 1 784 79.0 64 11 880 84.4 2 728 73.0 78 11 990 81.4 2 562 66.7 2nd Example Spruce wood hogged chips are treated with a 5% magnesium sulphate solution by immersion in the solution or spraying with the solutian until the wood contains approximately 5% sulphate/bone-dry wood.
The chips are then stored at room temperature for approximately 24 hours and then decomposed w;th a magnesium bisulphite solution having a pH
value of approximately 4 and a total S02 content of 4%. The liquor ratio is 5:1, the maximum temperature is between 160 and 165C. After approx. 2 1/2 - 3 hours decomposition time at maximum temperature, a Kappa number between 30 and 40 is attained. The cellulose yield is between 54 and 55%. The technological values of the cellulose are as follows:
Grinding Grinding Tearing Bursting Fold No. Breaking ;
time fineness length strength strength min SR m m P
- 17 9 240 54.g 2 700 113.7 20.5 10 450 75.6 1 555 87.2 46.5 12~260 75.2 1 687 82.4 73 12 125 78.4 2 304 78.0 6~L~
3rd Example By proceeding as under Example 1, bu-t additionally adding a further 5% o~ magnesium sulphate/bone-dry wood to the decomposing -~
solution, a yield of 57% is attained, and celluloses with the following technological values:
Grinding Grinding Tearing Bursting Fold No. ereaking time fineness length strength strenyth min SR m m P
- 17 8 205 58.8 2 885 106.6 23.510 340 74.0 1 257 86.0 11 375 7q.1 1 010 77.2 11 050 68.6 1 125 7~.4 ~ , , ~ : .. . .
~, ,.
Certain optimum properties of the cellulose are desirable when producing spruce wood celluloses for the paper industry. It is important to decompose the wood as gently as possible in order that a high proportion of the carbohydrates of the wood is retained in the cellulose and the strength of the fibres is reduced as little as possible during the decomposition of the wood. In order to keep the outlay for bleaching as low as possible, it is further desirable to produce celluloses which already exhibit high whiteness values in the unbleached state.
The production of celluloses is dominated by two processes and their modifications, namely the sulphate process and the sulphite process. The principal advantage of the sulphate process compared to the sulphite process are the higher strength of the celluloses thereby produced. The principal advantages of the sulphite process lie in the higher whiteness values of the unbleached celluloses and their easier ; bleachability. Attempts have been made to discover methods whereby celluloses could be produced with both strong and readily bleachable fibres. It is possible to produce celluloses with such specific properties by modifications of the sulphite process.
This is possible by a known two-stage process, whereby decomposition is performed in the pH range of 4 in the first stage and the boiling is continued at higher pH values in the second stage.
Other sulphite processes aim at increasing the yield of the spruce wood decomposition. According to a known method of this type, boiling is performed in the neutral or weakly acid pH range in a first stage, whereby the glucomannan fraction of the wood becomes stabilised and does not also pass into solution under the conditions of the second stage.
~k This glucomannan stabilisation is also possible at room temperature if the pH value of the solution is raised and the re-action time prolonged. According to one described method, the wood was pretreated with dilute NaOH at low temperatures and then decomposed with a sodium bisulphite solution. According to an-other mode of production wood chips were treated with mil~c of lime and then decomposed with a calcium bisulphite solution. In-creased yiel~s o~ between 2 and 7% were achieved by these methods mentioned, depending upon the intensity of the pretreatment.
However, the technological properties of the celluloses thus pro- ~:
duced were no better, in part actually poorer than those of the celluloses produced by sulphite processes without pretreatment.
Celluloses with high strength values, such as can be produced by two-stage proces$es, have low yields. Furthermore, a two-stage process is so complicated that it has not been adopted industrial-ly. ,~
Object of the invention is a method of producing spruce 1;
wood celluloses by sulphite process on a magnesium basis, whereby the cellulose produced exhibits both high strength va]ues and good bleachability of the fibres. At the same time, a high yield ~rom the spruce wood decomposition is also required.
According to the invention this aim is achieved by a method of producing coniferous wood celluloses by the sulphite process on a magnesium basis comprising the steps o~:
~ a) treating hogged spruce wood chips by immersing them in, or spraying them with, either (1) a suspension of magnesium hydroxide having an MgO content of 2 to 3% until the chips con-tain 2 to 3% MgO in the ~orm of hydroxide, or (2) a solution having 5% magnesium sulphate until the chips contain about 5%
magnesium sulphate/bone dry wood;
(b) storing the thus treated chips at room temperature for approximately 24 hours;
~3 :J
6~
.~,~
(c) inducting the treated and stored chips in a digest-er with magnesium bisulphite solution and heating the resulting batch to a cooking temperature of 160 - 165C; and (d) cooking the chips in the digester for 2.5 - 3 hours at a temperature between 160 and 165C in a magnesium bisul-phite liquor having a pH value of about 4 and a total SO2 concen-tration of 4%, the liquor ratio during cooking being 5:1.
By this method, spruce wood celluloses are produced wlth yields which are up to 5 to 8~ higher than -those of compar-able sulphate cellulose processes. These high yields are alsomainta~ned in the bleaching. The celluloses thus produced are very readily bleachable and already have a high whiteness value in the unbleached state.
,:
.
~ - 4a -,~ ' L6~6 They can be ground more easily than sulphate celluloses.
Bursting and tensile strength are at least as high as for sulphate celluloses. The folding strength of the unground celluloses is higher than for sulphate celluloses, that of the ground celluloses slightly lower. The repeated tearing strength values are also slightly lower than for sulphate celluloses. The method requires no additional thermal energy compared to the magnesium bisulphite ` pracess (pH 4.0) because the pretreatment occurs at room temperature. , Moreover, no additional chemicals are required for the pretreatment with m11k of magnesium hydroxide, because the magnesium hydroxide already adsorbed by the wood is deducted in preparing the boiling ', acid. ~here magnesium sulphate is used for the pretreatment, the , ' magnesium sulphate which is required as make-up in the chemical circuit in any case can be used.
The object of the invention is more fully described and explained hereinbelow with reference to three exemplary embodiments '~' of the method according to the i,nvention:
1st Example Spruce wood hogged chips are treated with a mil k of magnesium hydroxlde having an MgO content of 2-3%, either by being immersed in the milk or by being sprayed with the milk until they contain 2-3%
of magnesi~um oxide in the form of hydroxide. The chips are then stored at room temperature for approximately 24 hours and then decomposed wi,th a magnesium bisulphite solution having a total S02 concentraticn of 4%. The liquor ratio here is 5:1. The pH value of the decomposing solution is initially about 2. By the reaction of the magnesium hydroxide already adsorbed in the pretreatment stage with the bisulphite solution it rises to about pH 4 before the maximum temperature of 160-165C is attained. At this maximum temperature the decomposition is performed in 2 1/2 - 3 hours up to Kappa numbers , ~
6~6 between 30 and 40. The cellulose yield is approximately 54%. The cellulose has the following technological values:
Grinding Grinding Tearing Bursting Fold No. Breaking Time fineness length strength strength min SR m2 p - 16 10 420 61.1 2 620 94.0 21.5 10 935 79.4 1 900 92.6 37.5 11 535 80.1 1 784 79.0 64 11 880 84.4 2 728 73.0 78 11 990 81.4 2 562 66.7 2nd Example Spruce wood hogged chips are treated with a 5% magnesium sulphate solution by immersion in the solution or spraying with the solutian until the wood contains approximately 5% sulphate/bone-dry wood.
The chips are then stored at room temperature for approximately 24 hours and then decomposed w;th a magnesium bisulphite solution having a pH
value of approximately 4 and a total S02 content of 4%. The liquor ratio is 5:1, the maximum temperature is between 160 and 165C. After approx. 2 1/2 - 3 hours decomposition time at maximum temperature, a Kappa number between 30 and 40 is attained. The cellulose yield is between 54 and 55%. The technological values of the cellulose are as follows:
Grinding Grinding Tearing Bursting Fold No. Breaking ;
time fineness length strength strength min SR m m P
- 17 9 240 54.g 2 700 113.7 20.5 10 450 75.6 1 555 87.2 46.5 12~260 75.2 1 687 82.4 73 12 125 78.4 2 304 78.0 6~L~
3rd Example By proceeding as under Example 1, bu-t additionally adding a further 5% o~ magnesium sulphate/bone-dry wood to the decomposing -~
solution, a yield of 57% is attained, and celluloses with the following technological values:
Grinding Grinding Tearing Bursting Fold No. ereaking time fineness length strength strenyth min SR m m P
- 17 8 205 58.8 2 885 106.6 23.510 340 74.0 1 257 86.0 11 375 7q.1 1 010 77.2 11 050 68.6 1 125 7~.4 ~ , , ~ : .. . .
~, ,.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of producing coniferous wood celluloses by the sulphite process on a magnesium basis comprising the steps of:
(a) treating hogged spruce wood chips by immersing them in, or spraying them with, either, (1) a suspension of magnesium hydroxide having an MgO content of 2 to 3% until the chips contain 2 to 3% MgO in the form of hydroxide, or (2) a solution having 5% magnesium sulphate until the chips contain about 5% magnesium sulphate/bone dry wood;
(b) storing the thus treated chips at room temper-ature for approximately 24 hours;
(c) inducting the treated and stored chips in a digester with magnesium bisulphite solution and heating the resulting batch to a cooking temperature of 160°-165°C; and (d) cooking the chips in the digester for 2.5-3 hours at a temperature between 160° and l65°C in a magnesium bisulphite liquor having a pH value of about 4 and a total SO2 concentration of 4%, the liquor ratio during cooking being 5:1.
(a) treating hogged spruce wood chips by immersing them in, or spraying them with, either, (1) a suspension of magnesium hydroxide having an MgO content of 2 to 3% until the chips contain 2 to 3% MgO in the form of hydroxide, or (2) a solution having 5% magnesium sulphate until the chips contain about 5% magnesium sulphate/bone dry wood;
(b) storing the thus treated chips at room temper-ature for approximately 24 hours;
(c) inducting the treated and stored chips in a digester with magnesium bisulphite solution and heating the resulting batch to a cooking temperature of 160°-165°C; and (d) cooking the chips in the digester for 2.5-3 hours at a temperature between 160° and l65°C in a magnesium bisulphite liquor having a pH value of about 4 and a total SO2 concentration of 4%, the liquor ratio during cooking being 5:1.
2. A method as defined in claim 1 in which the hogged chips are immersed in, or sprayed with, said suspension of magnesium hydroxide; and in which the magnesium bisulphite solution inducted in the digester has a pH value of about 2 when heating of the batch commences.
3. A method as defined in claim 1 in which the hogged chips are immersed in, or sprayed with, said magnesium sulphate;
and in which the magnesium bisulphite solution inducted in the digester has a pH value of about 4 and a total SO2 content of 4% when heating of the batch commences.
and in which the magnesium bisulphite solution inducted in the digester has a pH value of about 4 and a total SO2 content of 4% when heating of the batch commences.
4. A method as defined in claim 2 including the step of adding 5% of magnesium sulphate/bone dry wood to said magnesium bisulphite liquor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH005489/77 | 1977-05-03 | ||
| CH548977 | 1977-05-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1101616A true CA1101616A (en) | 1981-05-26 |
Family
ID=4294440
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA301,780A Expired CA1101616A (en) | 1977-05-03 | 1978-04-24 | Method of producing coniferous wood celluloses by the sulphite process on a magnesium basis |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS53139802A (en) |
| AT (1) | AT364908B (en) |
| BR (1) | BR7802645A (en) |
| CA (1) | CA1101616A (en) |
| FI (1) | FI781351A (en) |
| SE (1) | SE7805124L (en) |
-
1978
- 1978-04-24 CA CA301,780A patent/CA1101616A/en not_active Expired
- 1978-04-27 BR BR7802645A patent/BR7802645A/en unknown
- 1978-05-02 AT AT0316478A patent/AT364908B/en not_active IP Right Cessation
- 1978-05-02 FI FI781351A patent/FI781351A/en not_active Application Discontinuation
- 1978-05-02 JP JP5321178A patent/JPS53139802A/en active Pending
- 1978-05-03 SE SE7805124A patent/SE7805124L/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| ATA316478A (en) | 1981-04-15 |
| BR7802645A (en) | 1978-12-12 |
| SE7805124L (en) | 1978-11-04 |
| JPS53139802A (en) | 1978-12-06 |
| FI781351A (en) | 1978-11-04 |
| AT364908B (en) | 1981-11-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |