CA1250704A - Pulping process - Google Patents
Pulping processInfo
- Publication number
- CA1250704A CA1250704A CA000476860A CA476860A CA1250704A CA 1250704 A CA1250704 A CA 1250704A CA 000476860 A CA000476860 A CA 000476860A CA 476860 A CA476860 A CA 476860A CA 1250704 A CA1250704 A CA 1250704A
- Authority
- CA
- Canada
- Prior art keywords
- liquor
- cooking
- group
- alkyl
- cooking liquor
- 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
- D21C3/00—Pulping cellulose-containing materials
- D21C3/22—Other features of pulping processes
- D21C3/222—Use of compounds accelerating the pulping processes
Landscapes
- Paper (AREA)
- Chemical And Physical Treatments For Wood And The Like (AREA)
Abstract
A B S T R A C T
PULPING PROCESS
A process for the manufacture of wood-pulp is described in which one or more amphoteric surfactants are included in the cooking liquor to reduce the cooking time.
PULPING PROCESS
A process for the manufacture of wood-pulp is described in which one or more amphoteric surfactants are included in the cooking liquor to reduce the cooking time.
Description
l~S~
PULPINC P~OCESS
This invention relates to an improved process for the manufacture of wood pulp, useful in the manufacture of paper and for other purposes.
In the manufacture of wood chips the chips are first digested under alkaline, acid or neutral conditions.
In the Kraft or sulphate process, wood chips are treated (cooked) at high temperatures with an alkaline solution containing a mixture of sodium hydroxide, sodium sulphide and sodium carbonate in order to obtain sulphi-dation of the lignins and thus their dissolution. In the sulphite process an acidic or neutral solution containing sulphites and bisulphites is used for dissolving the lignin. The processes are usually carried out so that the chips are subjected to the chemical treatment starting at a temperature below lOO-C and gradually bringing the temperature up in the region of 150 - 180C.
A well known problem is that the penetration of the chemicals into chips is slow and incomplete. This can allow some lignin to polymerize before it has time to dissolve, and results in a high lignin content (Kappa value) of the pulp and a considerable amount of un-digested fibres (screen reject). In the Kraft process for example the penetration is optimized by allowing 1.5 -3 hours for the gradual raising of the temperature. Even so,the problem still exists, and in order to obtain an accept-ably low Kappa value and low screen reject it has to be compensated by prolonging the cookîng at maximum tempera-ture for a few hours, with a resulting degradation of carbohydrates and loss of pulp yield.
It has been previously suggested that the pene-tration of chemicals into the wood structure would be aided by a surface active agent. However, attempts to improve the pulping processes by the addition of surface active agents have so far been unsuccessful and such agents are not used in current processes.
It is an object of this invention to provide ad-ditives which show demonstrable advantages in assuring penetration of the chemicals and dissolution of the lignin with not more than normal carbohydrate degra-dation in a considerably shorter cooking cycle. I
have surprisingly found that the desired advantages are obtained to a substantial and economically very important degree by adding to the pulping liquor small amounts of an amphoteric surface active agent.
The invention in general terms is thus concerned with a process for the manufacture of wood-pulp in which the cooking liquor is an alkaline liquor or an acid or neutral sulphite or bisulphite liquor and includes one or more amphoteric surface acti~e agents.
The liquor may for example be an alkaline liq~or such as a Kraft or soda liquor, or an acid or neutral sulphite or bisulphi~e liquor. The chemical constitution of these liquors is very well known to pulp manuEacturers and is described for example in "Pulping Processes", S.A, Rydholm (Interscience Publishers, 1965).
~zs~
The process of the invention is of greatest advantage in connection with alkaline liquors, particularly liquors such as normally used in the Kraft process.
The surface active agent used should of course be one which is stable in and soluble in the cooking liquor.
The surfactant is preferably of the type having the general formula (I) or (II), particularly the former:
R-(CO)z-(OCH2CH2CH2)n- (N - (CHRl)X)y - N - Q (I) B B
B
R-(CO)z-(OCH2CH2CH2)n- ~N - (CHR )x)y ~ N - Q ~II) B B
where R is a C8 20 hydrocarbyl group, optionally substituted by -OH or -COOH;
Rl is H or Cl 6 alkyl;
B is H, alkyl, alkyl substituted by -OH or amino, or a group Q as de~ined below;
Q is an anionic moiety;
x is 2 to 6;
y is 0 to 5;
z is 0 to 1, and n is 0 or 1 (z being 0 when n is 1).
In these compounds, R may for example be a straight or branched alkyl or alkenyl group or cycloalkyl-alkyl (e.g.
cyclohexyl-alkyl) group, an aralkyl or ZSV7~
aralkenyl group (e.g. phenalkyl or phenalkenyl) in which the alkyl or alkenyl portion contains at least 6 carbon atoms; or the hydrocarbyl portion of a resinic acid containing at least two fused rings, e.g. as in the tricyclic pine resin acids such as abietic acid. R is preferably a C10_16 alkyl group, e.g. a C12 group. R
may for example be the hydrocarbyl portion of lauric or coconut fatty acid, both of which contain a high proportion of C12 constituents. An example of an unsaturated R group is oleyl and an example of a branched chain group is C16H33CH(CH3)-. The aliphatic portion of R may for example be substituted by hydroxy, as in hydroxystearyl~ or by -COOH (e.g. at the 2-position).
R is usually a hydrogen atom, but may be an lS alkyl group such as methyl.
When B is an alkyl group, it may have 1 - 6, preferably 2 - 4, carbon atoms, and is preferably a straight chain group. Examples of such groups are methyl and ethyl~ The alkyl group may be substituted, for example by hydroxy, as in 2-hydroxyethyl, or by amino.
The group Q may for example be of the formula -R COOM where R is a Cl 6 alkylene group (such as methylene or ethylene) and M is hydrogen or an alkali metal, alkaline earth metal, ammonium or substituted ammonium ion (e.g. mono-, di- or tri-hydroxyethyl-ammonium). M is preferably sodium, and R2 is preferably methylene.
x is preferably 2 and y is preferably 0 or 1.
In surfactants of formula (II) the associated anion may for example be halide ~e.g. chloro or bromo).
The surfactant thus preferably has one of the following structures:
Rco.NH.cH2cH2NcH2cooM
RN(CH2CH2C~1)2 .~
~z5~7~
NH.C~CH2COOM (e-g- R CH ( CH3 ) NH . CH2CH2COOM
where R CH ( CH3 ) is the R group) RN (C1~3)2 I ( 2 2 )2 RCO.NH.~CH2~31 (CH3)2 One or more amphoteric surfactants may be used as cooking liquor additives in my process. Also, the amphoteric surfactants may be used in combinatior. with one or more surfactants of other types, or example non-5 ionic or fluorinated surfactants. In this latter respect,the amphoteric surfactant can have the effect of solubili-sing surfactants of other general types which are stable in the cooking liquor but not normally soluble in it.
The surfactant or surfactants may generally be 10 used in an amount for example of up to 2% (e.g. 0.01% - 2.0-o-) of the cooking liquor, and preferably in amounts of 0.1 to 0.6% by weight.
~25q:~7Q4 It will be appreciated that except as regards the addition of the surfactant, the cooking process is carried out in generally the same manner as in con-ventional practice, again for example as described in "Pulping Processesl', referred to abo~e. The cooking time can however be reduced as demonstrated below, particularly under alkaline conditions.
Tests have shown that the addition of, for example, 0.5% based on the cooking liquor, of a surfactant of this type will reduce the required cooking time and the percen-tage of screen reject substantially in the Kraft process and also in the sulphite process. The reasons why the surface active agents of the invention are superior to those previously tried are not clear. Attempts to cor-relate the effect to the lowering of surface tension have not been successful, and the mechanisms involved are probably complex.
The following examples illustrate the invention.
Example 1 A series of Kraft cooking trials in autoclaves were carried out with and without the additives of the invention. The additives employed were amphoteric sur-factants of the general structure shown in formula 1 and were obtained from Rexolin Chemicals of Helsingborg, Sweden, under the trade mark of Rexoteric XCE* and XJO*.
The amounts used were 0.5~ of the cooking liquor (white liquor). In order to demonstrate the beneficial effect of the additives on the penetration of the chips, the time allowed for the gradual heating to maximum temp-erature, normally 2.5 hours, was only 45 minutes in all the trials. After the cooking was continued * Trade Mark ~, ~2S~Q~
for the time required to obtain the Kappa values desired, it was shown that when using said additive at Kappa No.60 the residue of undigested fibres (screen reject) was 0.9%9 the same residue amounting to 4% when not using the additive at the same Kappa number. At Kappa No.70 the undigested fibres were 1.1% when using the additives in the cooking liquor and was 6% when using the cooking liquid without the additives. At Kappa No.35 the resid~e on the screen was 0.5% with the additives and 1.5%
without the additives.
Ex~
A series of sulphite cooking trials were carried out using as an additive 0.5%, based on the lS acidic cooking liquor, of Rexoteric XJ0 mentioned in Example 1. Trials without the additive were made for comparison. The temperature was raised from 20 to lOS~ in 1.5 hours, and in order to demonstrate the effect of the additive the standstill at 105-C
normally employed in order to obtain a good penetra-tion was omitted. Instead, the heating was continued and the final cooking temperature of 132-C was reached in 1 hour.
After the cooking was continued for the time required to obtain the Kappa values desired, it was shown that when applying said additive at a Kappa No.
of 50, the residue of undigested fibres was 2.8%.
The same residue amounted to 5.5% without the additive.
PULPINC P~OCESS
This invention relates to an improved process for the manufacture of wood pulp, useful in the manufacture of paper and for other purposes.
In the manufacture of wood chips the chips are first digested under alkaline, acid or neutral conditions.
In the Kraft or sulphate process, wood chips are treated (cooked) at high temperatures with an alkaline solution containing a mixture of sodium hydroxide, sodium sulphide and sodium carbonate in order to obtain sulphi-dation of the lignins and thus their dissolution. In the sulphite process an acidic or neutral solution containing sulphites and bisulphites is used for dissolving the lignin. The processes are usually carried out so that the chips are subjected to the chemical treatment starting at a temperature below lOO-C and gradually bringing the temperature up in the region of 150 - 180C.
A well known problem is that the penetration of the chemicals into chips is slow and incomplete. This can allow some lignin to polymerize before it has time to dissolve, and results in a high lignin content (Kappa value) of the pulp and a considerable amount of un-digested fibres (screen reject). In the Kraft process for example the penetration is optimized by allowing 1.5 -3 hours for the gradual raising of the temperature. Even so,the problem still exists, and in order to obtain an accept-ably low Kappa value and low screen reject it has to be compensated by prolonging the cookîng at maximum tempera-ture for a few hours, with a resulting degradation of carbohydrates and loss of pulp yield.
It has been previously suggested that the pene-tration of chemicals into the wood structure would be aided by a surface active agent. However, attempts to improve the pulping processes by the addition of surface active agents have so far been unsuccessful and such agents are not used in current processes.
It is an object of this invention to provide ad-ditives which show demonstrable advantages in assuring penetration of the chemicals and dissolution of the lignin with not more than normal carbohydrate degra-dation in a considerably shorter cooking cycle. I
have surprisingly found that the desired advantages are obtained to a substantial and economically very important degree by adding to the pulping liquor small amounts of an amphoteric surface active agent.
The invention in general terms is thus concerned with a process for the manufacture of wood-pulp in which the cooking liquor is an alkaline liquor or an acid or neutral sulphite or bisulphite liquor and includes one or more amphoteric surface acti~e agents.
The liquor may for example be an alkaline liq~or such as a Kraft or soda liquor, or an acid or neutral sulphite or bisulphi~e liquor. The chemical constitution of these liquors is very well known to pulp manuEacturers and is described for example in "Pulping Processes", S.A, Rydholm (Interscience Publishers, 1965).
~zs~
The process of the invention is of greatest advantage in connection with alkaline liquors, particularly liquors such as normally used in the Kraft process.
The surface active agent used should of course be one which is stable in and soluble in the cooking liquor.
The surfactant is preferably of the type having the general formula (I) or (II), particularly the former:
R-(CO)z-(OCH2CH2CH2)n- (N - (CHRl)X)y - N - Q (I) B B
B
R-(CO)z-(OCH2CH2CH2)n- ~N - (CHR )x)y ~ N - Q ~II) B B
where R is a C8 20 hydrocarbyl group, optionally substituted by -OH or -COOH;
Rl is H or Cl 6 alkyl;
B is H, alkyl, alkyl substituted by -OH or amino, or a group Q as de~ined below;
Q is an anionic moiety;
x is 2 to 6;
y is 0 to 5;
z is 0 to 1, and n is 0 or 1 (z being 0 when n is 1).
In these compounds, R may for example be a straight or branched alkyl or alkenyl group or cycloalkyl-alkyl (e.g.
cyclohexyl-alkyl) group, an aralkyl or ZSV7~
aralkenyl group (e.g. phenalkyl or phenalkenyl) in which the alkyl or alkenyl portion contains at least 6 carbon atoms; or the hydrocarbyl portion of a resinic acid containing at least two fused rings, e.g. as in the tricyclic pine resin acids such as abietic acid. R is preferably a C10_16 alkyl group, e.g. a C12 group. R
may for example be the hydrocarbyl portion of lauric or coconut fatty acid, both of which contain a high proportion of C12 constituents. An example of an unsaturated R group is oleyl and an example of a branched chain group is C16H33CH(CH3)-. The aliphatic portion of R may for example be substituted by hydroxy, as in hydroxystearyl~ or by -COOH (e.g. at the 2-position).
R is usually a hydrogen atom, but may be an lS alkyl group such as methyl.
When B is an alkyl group, it may have 1 - 6, preferably 2 - 4, carbon atoms, and is preferably a straight chain group. Examples of such groups are methyl and ethyl~ The alkyl group may be substituted, for example by hydroxy, as in 2-hydroxyethyl, or by amino.
The group Q may for example be of the formula -R COOM where R is a Cl 6 alkylene group (such as methylene or ethylene) and M is hydrogen or an alkali metal, alkaline earth metal, ammonium or substituted ammonium ion (e.g. mono-, di- or tri-hydroxyethyl-ammonium). M is preferably sodium, and R2 is preferably methylene.
x is preferably 2 and y is preferably 0 or 1.
In surfactants of formula (II) the associated anion may for example be halide ~e.g. chloro or bromo).
The surfactant thus preferably has one of the following structures:
Rco.NH.cH2cH2NcH2cooM
RN(CH2CH2C~1)2 .~
~z5~7~
NH.C~CH2COOM (e-g- R CH ( CH3 ) NH . CH2CH2COOM
where R CH ( CH3 ) is the R group) RN (C1~3)2 I ( 2 2 )2 RCO.NH.~CH2~31 (CH3)2 One or more amphoteric surfactants may be used as cooking liquor additives in my process. Also, the amphoteric surfactants may be used in combinatior. with one or more surfactants of other types, or example non-5 ionic or fluorinated surfactants. In this latter respect,the amphoteric surfactant can have the effect of solubili-sing surfactants of other general types which are stable in the cooking liquor but not normally soluble in it.
The surfactant or surfactants may generally be 10 used in an amount for example of up to 2% (e.g. 0.01% - 2.0-o-) of the cooking liquor, and preferably in amounts of 0.1 to 0.6% by weight.
~25q:~7Q4 It will be appreciated that except as regards the addition of the surfactant, the cooking process is carried out in generally the same manner as in con-ventional practice, again for example as described in "Pulping Processesl', referred to abo~e. The cooking time can however be reduced as demonstrated below, particularly under alkaline conditions.
Tests have shown that the addition of, for example, 0.5% based on the cooking liquor, of a surfactant of this type will reduce the required cooking time and the percen-tage of screen reject substantially in the Kraft process and also in the sulphite process. The reasons why the surface active agents of the invention are superior to those previously tried are not clear. Attempts to cor-relate the effect to the lowering of surface tension have not been successful, and the mechanisms involved are probably complex.
The following examples illustrate the invention.
Example 1 A series of Kraft cooking trials in autoclaves were carried out with and without the additives of the invention. The additives employed were amphoteric sur-factants of the general structure shown in formula 1 and were obtained from Rexolin Chemicals of Helsingborg, Sweden, under the trade mark of Rexoteric XCE* and XJO*.
The amounts used were 0.5~ of the cooking liquor (white liquor). In order to demonstrate the beneficial effect of the additives on the penetration of the chips, the time allowed for the gradual heating to maximum temp-erature, normally 2.5 hours, was only 45 minutes in all the trials. After the cooking was continued * Trade Mark ~, ~2S~Q~
for the time required to obtain the Kappa values desired, it was shown that when using said additive at Kappa No.60 the residue of undigested fibres (screen reject) was 0.9%9 the same residue amounting to 4% when not using the additive at the same Kappa number. At Kappa No.70 the undigested fibres were 1.1% when using the additives in the cooking liquor and was 6% when using the cooking liquid without the additives. At Kappa No.35 the resid~e on the screen was 0.5% with the additives and 1.5%
without the additives.
Ex~
A series of sulphite cooking trials were carried out using as an additive 0.5%, based on the lS acidic cooking liquor, of Rexoteric XJ0 mentioned in Example 1. Trials without the additive were made for comparison. The temperature was raised from 20 to lOS~ in 1.5 hours, and in order to demonstrate the effect of the additive the standstill at 105-C
normally employed in order to obtain a good penetra-tion was omitted. Instead, the heating was continued and the final cooking temperature of 132-C was reached in 1 hour.
After the cooking was continued for the time required to obtain the Kappa values desired, it was shown that when applying said additive at a Kappa No.
of 50, the residue of undigested fibres was 2.8%.
The same residue amounted to 5.5% without the additive.
Claims (5)
1. A process for the manufacture of wood-pulp in which the cooking liquor is an alkaline liquor or an acid or neutral sulphite or bisulphite liquor and includes one or more ampho-teric surface active agents of the general formula (I) or (II) (I) (II) where R is a C8-20 hydrocarbyl group, optionally substituted by -OH or -COOH;
R1 is H or C1-6 alkyl;
B is H, alkyl, alkyl substituted by -OH or amino, or a group Q as defined below;
Q is an anionic moiety;
x is 2 to 6;
y is 0 to 5;
z is 0 to 1, and n is 0 or 1 (z being 0 when n is 1) in an amount of up to about 2% by weight.
R1 is H or C1-6 alkyl;
B is H, alkyl, alkyl substituted by -OH or amino, or a group Q as defined below;
Q is an anionic moiety;
x is 2 to 6;
y is 0 to 5;
z is 0 to 1, and n is 0 or 1 (z being 0 when n is 1) in an amount of up to about 2% by weight.
2. A process as claimed in claim 1 wherein the surface active agent is present in the cooking liquor in an amount of 0.1 to 0.6 % by weight.
3. A process as claimed in claim 1 wherein one or more non-amphoteric surface active agents are also included in the cooking liquor.
4. A process according to claim 1 wherein an alkaline liquor is used as the cooking liquor.
5. A process according to claim 1 wherein Q is a compound of the formula -R2COOM wherein R2 is a C1-6alkylene group and M is hydrogen or an alkali metal ion, an alkaline earth metal ion, an ammonium ion or an ammonium ion substituted by one or more hydroxyethyl groups.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8407438 | 1984-03-22 | ||
| GB848407438A GB8407438D0 (en) | 1984-03-22 | 1984-03-22 | Pulping process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1250704A true CA1250704A (en) | 1989-03-07 |
Family
ID=10558503
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000476860A Expired CA1250704A (en) | 1984-03-22 | 1985-03-19 | Pulping process |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA1250704A (en) |
| FI (1) | FI79358C (en) |
| GB (2) | GB8407438D0 (en) |
| NO (1) | NO164788C (en) |
| SE (1) | SE463463B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5728265A (en) * | 1995-06-12 | 1998-03-17 | Henkel Corporation | Process for enhancing white liquor penetration into wood chips by contacting the chips with a mixture of the white liquor and a polymethylalkyl siloxane |
| CA2217415A1 (en) * | 1997-10-20 | 1999-04-20 | Tien-Feng Ling | Method for sulfite pulping using surfactants |
| CA2417791C (en) * | 2000-07-27 | 2008-01-08 | Ashland Inc | Process for digesting woodchips and digester additives |
| FI122815B (en) * | 2005-04-18 | 2012-07-13 | Cerefi Oy | Method for fractionating lignocellulosic materials and parts obtained from them |
-
1984
- 1984-03-22 GB GB848407438A patent/GB8407438D0/en active Pending
-
1985
- 1985-03-19 SE SE8501338A patent/SE463463B/en not_active IP Right Cessation
- 1985-03-19 CA CA000476860A patent/CA1250704A/en not_active Expired
- 1985-03-21 GB GB08507304A patent/GB2155966B/en not_active Expired
- 1985-03-21 NO NO851130A patent/NO164788C/en unknown
- 1985-03-22 FI FI851171A patent/FI79358C/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| FI79358B (en) | 1989-08-31 |
| GB2155966B (en) | 1987-12-09 |
| NO164788C (en) | 1990-11-14 |
| NO164788B (en) | 1990-08-06 |
| SE8501338D0 (en) | 1985-03-19 |
| SE463463B (en) | 1990-11-26 |
| GB8507304D0 (en) | 1985-05-01 |
| FI851171A0 (en) | 1985-03-22 |
| GB2155966A (en) | 1985-10-02 |
| FI79358C (en) | 1989-12-11 |
| NO851130L (en) | 1985-09-23 |
| SE8501338L (en) | 1985-09-23 |
| FI851171L (en) | 1985-09-23 |
| GB8407438D0 (en) | 1984-05-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |