CA1057008A - Method in sulphite pulping - Google Patents
Method in sulphite pulpingInfo
- Publication number
- CA1057008A CA1057008A CA234,872A CA234872A CA1057008A CA 1057008 A CA1057008 A CA 1057008A CA 234872 A CA234872 A CA 234872A CA 1057008 A CA1057008 A CA 1057008A
- Authority
- CA
- Canada
- Prior art keywords
- formate
- wood
- cooking
- ester
- added
- 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)
- Emulsifying, Dispersing, Foam-Producing Or Wetting Agents (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
In the sulphite pulping, the yield of pulp is increased by the addition of at least one of a selected group of formates to the cooking liquid before the impreg-nation of the wood. The formates have the formula:
In the sulphite pulping, the yield of pulp is increased by the addition of at least one of a selected group of formates to the cooking liquid before the impreg-nation of the wood. The formates have the formula:
Description
057~08 The present invention relates to a method of sulphite pulping of wood.
In particular, the present invention relates to a method of sulphite pulping in which the wood is impregnated with the cooking liquid to which has been added a small quantity of certain esters of formic acid and also desirably formic acid per se.
In the conventional sulphite pulping of wood the lignin and the greater part the the hemicellulose are dissolved, and sometimes also a minor part of the alpha cellulose is dissolved in the cooking liquid. A substantially pure alpha cellulose product may be desired, when the pulp is to be used in the manufacture of viscose cellulose. However, for paper pulp the removal of the hemicellulose only involves, as a rule, a loss of yield.
It has now been found that the yield as well as the strength of the pulp is increased when the cooking liquid includes a small quantity of at least one formic acid ester (formate) of hexyl alcohol or of an unsubstituted or methyl-substituted norbornyl alochol. The formates have the generalstructural formula:
R - O --~ H
where R is a hexyl group or an unsubstituted or methyl-substituted norbornyl group.
In the process of the present invention at least one of the aforesaid formates is added before the impregnation of the wood with cooking liquid, to said liquid in an amount of at least 0.02 mol, preferably at least 0.1 mol, as calculated per ton (1000 kg) absolutely dry wood. Generally, the addition of one of said formates is sufficient, but two or more of them - 1 - ~
.
105~008 may be added. Preferably, the addition tak~s place immediately before the introduction of the cooking liquid into the digester.
Before the addition the formate or formates may be dispersed in water by a non-ionic dispersing agent, and, if desired, the formates may previously be dissolved in a suitable solvent such as turpentine, cymene or diethyl benzene.
As mentioned above, the formate or formates must be added in an amount of at least 0.02 mol. This value may be regarded as a lower limit, below which no appreciable effect t can be observed. Among the agents useful as additives according to the invention endo-fenchyl formate and exo-norbornyl formate have proved to be especially active.
The method of sulphite cooking according to the present invention is particularly applicable when using spruce wood as raw material, but also other kinds of coniferous wood, such as pine wood, for instance, may be used. Also hardwood may be used in mixture with coniferous wood.
As suitable formates defined by the aforesaid structural formula the following may be mentioned:
H O
CH3-(CH2)4-C-O-C-H
hexyl formate ~ I ~ 33 H O
exo-norbornyl formate ~ endo-fenchyl formate --~ ~CH3 exo-isofenchyl formate ~57~08 The way these formates have their favourable influence on the sulphite cooking has not yet been entirely explained, but observations hitherto made seem to indicate that the formates counteract a condensation or polymerization of the lignin. In the pulping, the cooking liquid primarily brings the lignin of the wood into solution by sulphonation. In the process the carbon-oxygen bonds are broken, and reactive and rapidly sulphonatable intermediate substances of benzylium ion type or with a chinon methid structure are formed. It is known that the sulphonation of these substances occurs in competition with lignin condensa-tion reactions, in which benzylium ions or chinon methids (according to the conditions) will, with an aromatic substitution, react with another phenyl-propane unit. In this way a new and stable bond carbon-to-carbon is formed, and thus the process results in an increase of the size of the lignin molecules.
Consequently, this lignin condensation counteracts the desirable dissolving action of the sulphonating cooking liquid.
By thorough investigations it has been found that, during the conditions prevailing at the sulphite cooking, the formates are more or less rapidly hydrolyzed into correspond-ing alcohol and formic acid. It is assumed that the formic acid obstructs the iignincondensation reaction mentioned above, and such an influence probably occurs in two different ways.
Firstly, the formic acid may act directly as a reducing agent thus reducing some of the benzylium ions or chinon methids -analagousreactions are known. The reaction products then formed cannot be condensed in the manner as mentioned above with respect to benzylium ions or chinon methids. The second way, also dependent on the reducing action of the formic acid, involves the formation of thiosulphate by reaction between the formic acid and sulphur compounds in the cooking liquid. Owing to l~S7(~08 their high nucleophilic capacity the thiosulphate ions then very rapidly react with the benzylium ions or the chinon methids which are thus prevented from undergoing the lignin condensation.
Formic acid is normally present in the cooking liquid, t in varying quantities. Together with the formates added in accordance with theinvention this formic acid may have a favourable influence, as long as its concentration is not high enough to cause a predominance of detrimental secondary effects.
Thus, it may be very suitable to add formic acid to a cooking 10liquid which has a very low initial content thereof. Generally, however, the supplemental addition of formic acid should be less than 25% of the weight of the added amount of formate.
It has been found that the best effect of an addition of the formates is achieved, when the content of total SO2 in the cooking liquid is at least 1.5 times greater than the con-tent of combined SO2. This means that the method of the inven-tion may be applied not only in the old pulping with acid sul-phite but also in the modern pulping with bisulphite, such as magnesium bisulphite, for instance.
The invention will be further illustrated by way of the following Examples, in which all cookings with acid sulphite have been carried out in a laboratory scale, but the processes are directly applicable in large-scale production. The examples of pulping with bisulphite are taken directly from the operation of a large continuous digester.
Examples 1, 2 and 3 In the laboratory experiments, a laboratory digester having a volume of 8 litres was charged with dry chips of spruce wood (about 1 kg absolute dry weight) and 4 litres preheated cooking acid containing 6.0% total SO2 and 1.7% SO2 bound to CaO. The initial temperature was 60C. Each cooking began with - 4 - ~ -- ~ . - . - . :
10570~8
In particular, the present invention relates to a method of sulphite pulping in which the wood is impregnated with the cooking liquid to which has been added a small quantity of certain esters of formic acid and also desirably formic acid per se.
In the conventional sulphite pulping of wood the lignin and the greater part the the hemicellulose are dissolved, and sometimes also a minor part of the alpha cellulose is dissolved in the cooking liquid. A substantially pure alpha cellulose product may be desired, when the pulp is to be used in the manufacture of viscose cellulose. However, for paper pulp the removal of the hemicellulose only involves, as a rule, a loss of yield.
It has now been found that the yield as well as the strength of the pulp is increased when the cooking liquid includes a small quantity of at least one formic acid ester (formate) of hexyl alcohol or of an unsubstituted or methyl-substituted norbornyl alochol. The formates have the generalstructural formula:
R - O --~ H
where R is a hexyl group or an unsubstituted or methyl-substituted norbornyl group.
In the process of the present invention at least one of the aforesaid formates is added before the impregnation of the wood with cooking liquid, to said liquid in an amount of at least 0.02 mol, preferably at least 0.1 mol, as calculated per ton (1000 kg) absolutely dry wood. Generally, the addition of one of said formates is sufficient, but two or more of them - 1 - ~
.
105~008 may be added. Preferably, the addition tak~s place immediately before the introduction of the cooking liquid into the digester.
Before the addition the formate or formates may be dispersed in water by a non-ionic dispersing agent, and, if desired, the formates may previously be dissolved in a suitable solvent such as turpentine, cymene or diethyl benzene.
As mentioned above, the formate or formates must be added in an amount of at least 0.02 mol. This value may be regarded as a lower limit, below which no appreciable effect t can be observed. Among the agents useful as additives according to the invention endo-fenchyl formate and exo-norbornyl formate have proved to be especially active.
The method of sulphite cooking according to the present invention is particularly applicable when using spruce wood as raw material, but also other kinds of coniferous wood, such as pine wood, for instance, may be used. Also hardwood may be used in mixture with coniferous wood.
As suitable formates defined by the aforesaid structural formula the following may be mentioned:
H O
CH3-(CH2)4-C-O-C-H
hexyl formate ~ I ~ 33 H O
exo-norbornyl formate ~ endo-fenchyl formate --~ ~CH3 exo-isofenchyl formate ~57~08 The way these formates have their favourable influence on the sulphite cooking has not yet been entirely explained, but observations hitherto made seem to indicate that the formates counteract a condensation or polymerization of the lignin. In the pulping, the cooking liquid primarily brings the lignin of the wood into solution by sulphonation. In the process the carbon-oxygen bonds are broken, and reactive and rapidly sulphonatable intermediate substances of benzylium ion type or with a chinon methid structure are formed. It is known that the sulphonation of these substances occurs in competition with lignin condensa-tion reactions, in which benzylium ions or chinon methids (according to the conditions) will, with an aromatic substitution, react with another phenyl-propane unit. In this way a new and stable bond carbon-to-carbon is formed, and thus the process results in an increase of the size of the lignin molecules.
Consequently, this lignin condensation counteracts the desirable dissolving action of the sulphonating cooking liquid.
By thorough investigations it has been found that, during the conditions prevailing at the sulphite cooking, the formates are more or less rapidly hydrolyzed into correspond-ing alcohol and formic acid. It is assumed that the formic acid obstructs the iignincondensation reaction mentioned above, and such an influence probably occurs in two different ways.
Firstly, the formic acid may act directly as a reducing agent thus reducing some of the benzylium ions or chinon methids -analagousreactions are known. The reaction products then formed cannot be condensed in the manner as mentioned above with respect to benzylium ions or chinon methids. The second way, also dependent on the reducing action of the formic acid, involves the formation of thiosulphate by reaction between the formic acid and sulphur compounds in the cooking liquid. Owing to l~S7(~08 their high nucleophilic capacity the thiosulphate ions then very rapidly react with the benzylium ions or the chinon methids which are thus prevented from undergoing the lignin condensation.
Formic acid is normally present in the cooking liquid, t in varying quantities. Together with the formates added in accordance with theinvention this formic acid may have a favourable influence, as long as its concentration is not high enough to cause a predominance of detrimental secondary effects.
Thus, it may be very suitable to add formic acid to a cooking 10liquid which has a very low initial content thereof. Generally, however, the supplemental addition of formic acid should be less than 25% of the weight of the added amount of formate.
It has been found that the best effect of an addition of the formates is achieved, when the content of total SO2 in the cooking liquid is at least 1.5 times greater than the con-tent of combined SO2. This means that the method of the inven-tion may be applied not only in the old pulping with acid sul-phite but also in the modern pulping with bisulphite, such as magnesium bisulphite, for instance.
The invention will be further illustrated by way of the following Examples, in which all cookings with acid sulphite have been carried out in a laboratory scale, but the processes are directly applicable in large-scale production. The examples of pulping with bisulphite are taken directly from the operation of a large continuous digester.
Examples 1, 2 and 3 In the laboratory experiments, a laboratory digester having a volume of 8 litres was charged with dry chips of spruce wood (about 1 kg absolute dry weight) and 4 litres preheated cooking acid containing 6.0% total SO2 and 1.7% SO2 bound to CaO. The initial temperature was 60C. Each cooking began with - 4 - ~ -- ~ . - . - . :
10570~8
2 hour impregnation period, during which the temperature was successively raised to 80C. After the impregnation the supply of heat was increased such that a final temperature of about 130C was reached 5 hours from the start. The total time of cooking fluctuated in the various experiments. At the end of the cooking a common degassing took place, whereupon the cooking was stopped in the usual way. The yield of pulp from each experiment was estimated by a thorough weighing of chips having a known percentage of humidity in combination with a thorough washing, disintegration, drying and weighing of the quantity of the pulp obtained.
During the whole series of experiments a single quality of chips was used, but to control that the results were not influenced by different times of storing, comparative cookings without the addition of yield increasing a~ents were carried out at equal intervals. All these comparative tests showed a very good correspondence, and the yield of unscreened pulp was, on an average, 51.4% at a kappa-number of 40. The brightness was measured to 64% SCAN, and the time of cooking was, on an average, 9.0 hours.
In all experiments shown in the following Table I
there were mixed 100 parts by weight formate, 3 parts by weight formic acid and 30 parts by weight non-ionic dispersing agent, and the mixture was dispersed in water in the ratio 1:20. The aqueous dispersion was admixed in the cooking acid immediately before the latter was pumped into the digester.
Table I
Example No. 1 2 3 _ _ Additive Exo-iso- Endo- Exo-nor-fenchyl fenchyl bornyl formate formate formate Added g/ton abs. dry wood 24 96 abt 10,000 Cooking time in hours 8.5 8.5 9.1 Kappa-number 38 40 35 Brightness SCAN 69.5 70.0 69.5 Yield of unscreened pulp, % 55.5 57.2 56.2 Examples 4, 5, 6, 7 and 8 The experiments with continuous bisulphite pulping in large-scale production were carried out in a plant shown in the accompanying drawing which is a flow sheet of the process, and the process was as follows:
Chips of spruce wood were fed from a chip bin A via a chip meter B (formed as a winged wheel meter) and a low-pressure feeder C (i.e. a rotary vane feeder) into a steaming vessel D
which was formed as a horizontal cylinder containing a feed screw. Fresh steam was supplied from below through the body of chips to maintain a pressure of 1.5 atm. gauge in the vessel D.
~he residence time in the steaming vessel D was 2-4 minutes.
Steam mixed with air expelled from the chips was vented through the chip bin due to leakage through the vane feeder and the chip meter, but it could also be discharged from the steaming vessel in a controlled amount through a specific venting conduit.
From the steaming vessel D the chips dropped down the chip chute E down into a high pressure feeder F, where, by means . . . .
.
l~D57~QB
of circulating cooking acid, they were stuffed in the valve chamber initially in vertical position. When this valve chamber, on the rotation of the cock, had been turned to a horizontal position, more cooking acid was supplied to convey the chips to the top separator G which is an inclined cylinder containing a concentric screw adapted to convey chips and acid. In its lower part said cylinder has a strainer to withdraw the acid circulating through the high pressure feeder. On their way from the high pressure feeder to the outlet end of the top separator the steamed chips were impregnated during about 3 minutes at 110C
and 12 atm. gauge. Cooking acid heated to about 90C by means of vapours from lye evaporation was supplied in the top separator in such an amount that the ratio wood:cooking acid was adjusted to 1:2. The acid contained about 8.5~ by weight total SO2 and 4.0% by weight MgO-combined SO2.
From the top separator the chips and the acid were tilted down into the steam space of the digester H which con-sisted of a vertical cylinder having a diameter of 4 metres, a height of 48 metres and a volume of 600 m3. The outputer per day would be 350 ton pulp. The upper half of the digester was used for the proper cooking, while the lower half was used for a counter-current high heat washing.
Live steam was supplied to the steam space in such a way that the contents of the digester was instantaneously heated to full cooking temperature, in this case 158-160C. At the end of the cooking zone J the waste liquor was discharged through a pipe K and led to a recovery unit. In the lower zone, i.e. the washing zone L, the pulp was washed with water supplied through a conduit M, and the washed pulp was withdrawn through an outlet N
at the bottom of the digester.
10,57V08 ,, , The following Table II includes three examples. One of them was carried out without additives to serve as a compara-tive test, while in the other examples 50 g endofenchyl formate (EFF) were added per ton absolutely dry wood. In the same way as in the laboratory experiments described above, the formate was dispersed in water (in one example together with 3% by weight formic acid) by means of a non-ionic dispersing agent, and the dispersion was supplied to the cooking acid immediately before the high pressure feeder.
Table II
_ i Example No. 4 5 6 Additive g/ton dry wood No 50 g pure 50 g pure ~;
addition EFF EFF + 3~
formic acid % total SO2 in the acid 8.5 8.5 8.5 % bound SO2 in the acid 4.0 4.0 4.0 Kappa-number 45 45 45 Breaking length at 40 SR, m 8500 8700 9600 Breaking length in m.
after beating 20 min. 6600 6800 8500 Tearing strength in g. at 8000 m breaking length 85 90 101 Brightness SCAN 69 72 75 Yield o unscreened pulp, % 53.0 56.0 57.5 Experiments in large-scale production have also been carried out while adding hexyl formate together with 3% formic acid, calculated on the weight of the formate. The results 30 appear from the following Table III,where the comparative test is the same as in Table II.
Table III
Example No. 4 7 8 : ' Additive g/ton dry wood No 50 g HF + 100 g HF +
addition 3% formic 3% formic acid acid total SO2 in the acid 8.5 8.5 8.5 ~ bound SO2 in the acid 4.0 4.0 4.0 Kappa-number 45 45 45 Breaking length at 40 SR, m 8500 8600 9300 Breaking length in m.
after beating 20 min. 6600 6800 8300 Tearing strength in g. at 8000 m. breaking length 85 87 99 Brightness SCAN 69 71 74 Yield of unscreened pulp, ~ 53.0 55.8 57.3
During the whole series of experiments a single quality of chips was used, but to control that the results were not influenced by different times of storing, comparative cookings without the addition of yield increasing a~ents were carried out at equal intervals. All these comparative tests showed a very good correspondence, and the yield of unscreened pulp was, on an average, 51.4% at a kappa-number of 40. The brightness was measured to 64% SCAN, and the time of cooking was, on an average, 9.0 hours.
In all experiments shown in the following Table I
there were mixed 100 parts by weight formate, 3 parts by weight formic acid and 30 parts by weight non-ionic dispersing agent, and the mixture was dispersed in water in the ratio 1:20. The aqueous dispersion was admixed in the cooking acid immediately before the latter was pumped into the digester.
Table I
Example No. 1 2 3 _ _ Additive Exo-iso- Endo- Exo-nor-fenchyl fenchyl bornyl formate formate formate Added g/ton abs. dry wood 24 96 abt 10,000 Cooking time in hours 8.5 8.5 9.1 Kappa-number 38 40 35 Brightness SCAN 69.5 70.0 69.5 Yield of unscreened pulp, % 55.5 57.2 56.2 Examples 4, 5, 6, 7 and 8 The experiments with continuous bisulphite pulping in large-scale production were carried out in a plant shown in the accompanying drawing which is a flow sheet of the process, and the process was as follows:
Chips of spruce wood were fed from a chip bin A via a chip meter B (formed as a winged wheel meter) and a low-pressure feeder C (i.e. a rotary vane feeder) into a steaming vessel D
which was formed as a horizontal cylinder containing a feed screw. Fresh steam was supplied from below through the body of chips to maintain a pressure of 1.5 atm. gauge in the vessel D.
~he residence time in the steaming vessel D was 2-4 minutes.
Steam mixed with air expelled from the chips was vented through the chip bin due to leakage through the vane feeder and the chip meter, but it could also be discharged from the steaming vessel in a controlled amount through a specific venting conduit.
From the steaming vessel D the chips dropped down the chip chute E down into a high pressure feeder F, where, by means . . . .
.
l~D57~QB
of circulating cooking acid, they were stuffed in the valve chamber initially in vertical position. When this valve chamber, on the rotation of the cock, had been turned to a horizontal position, more cooking acid was supplied to convey the chips to the top separator G which is an inclined cylinder containing a concentric screw adapted to convey chips and acid. In its lower part said cylinder has a strainer to withdraw the acid circulating through the high pressure feeder. On their way from the high pressure feeder to the outlet end of the top separator the steamed chips were impregnated during about 3 minutes at 110C
and 12 atm. gauge. Cooking acid heated to about 90C by means of vapours from lye evaporation was supplied in the top separator in such an amount that the ratio wood:cooking acid was adjusted to 1:2. The acid contained about 8.5~ by weight total SO2 and 4.0% by weight MgO-combined SO2.
From the top separator the chips and the acid were tilted down into the steam space of the digester H which con-sisted of a vertical cylinder having a diameter of 4 metres, a height of 48 metres and a volume of 600 m3. The outputer per day would be 350 ton pulp. The upper half of the digester was used for the proper cooking, while the lower half was used for a counter-current high heat washing.
Live steam was supplied to the steam space in such a way that the contents of the digester was instantaneously heated to full cooking temperature, in this case 158-160C. At the end of the cooking zone J the waste liquor was discharged through a pipe K and led to a recovery unit. In the lower zone, i.e. the washing zone L, the pulp was washed with water supplied through a conduit M, and the washed pulp was withdrawn through an outlet N
at the bottom of the digester.
10,57V08 ,, , The following Table II includes three examples. One of them was carried out without additives to serve as a compara-tive test, while in the other examples 50 g endofenchyl formate (EFF) were added per ton absolutely dry wood. In the same way as in the laboratory experiments described above, the formate was dispersed in water (in one example together with 3% by weight formic acid) by means of a non-ionic dispersing agent, and the dispersion was supplied to the cooking acid immediately before the high pressure feeder.
Table II
_ i Example No. 4 5 6 Additive g/ton dry wood No 50 g pure 50 g pure ~;
addition EFF EFF + 3~
formic acid % total SO2 in the acid 8.5 8.5 8.5 % bound SO2 in the acid 4.0 4.0 4.0 Kappa-number 45 45 45 Breaking length at 40 SR, m 8500 8700 9600 Breaking length in m.
after beating 20 min. 6600 6800 8500 Tearing strength in g. at 8000 m breaking length 85 90 101 Brightness SCAN 69 72 75 Yield o unscreened pulp, % 53.0 56.0 57.5 Experiments in large-scale production have also been carried out while adding hexyl formate together with 3% formic acid, calculated on the weight of the formate. The results 30 appear from the following Table III,where the comparative test is the same as in Table II.
Table III
Example No. 4 7 8 : ' Additive g/ton dry wood No 50 g HF + 100 g HF +
addition 3% formic 3% formic acid acid total SO2 in the acid 8.5 8.5 8.5 ~ bound SO2 in the acid 4.0 4.0 4.0 Kappa-number 45 45 45 Breaking length at 40 SR, m 8500 8600 9300 Breaking length in m.
after beating 20 min. 6600 6800 8300 Tearing strength in g. at 8000 m. breaking length 85 87 99 Brightness SCAN 69 71 74 Yield of unscreened pulp, ~ 53.0 55.8 57.3
Claims (6)
1. In the method of sulphite cooking of wood which includes impregnating the wood with a cooking liquid, the improve-ment in which the cooking liquid impregnated in the wood has added thereto before said impregnation at least one formic acid ester having the general formula where R is a hexyl group or an unsubstituted or methyl substituted norbornyl group in an amount of at least 0.02 mol, calculated per ton absolutely dry wood.
2. A method as claimed in claim 1 in which the cooking liquid has added thereto at least 0.1 mol of said ester calculated per ton absolutely dry wood.
3. A method as claimed in claim 1 or 2, in which in addition to the ester, formic acid is added to the cooking liquid in an amount of at most 25%, based on the weight of the added ester.
4. A method as claimed in claim 1 or 2 in which the ester is added as a dispersion in water with a non-ionic dis-persing agent.
5. A method as claimed in claim 1 or 2 in which the ester is selected from hexyl formate, exo-norbornyl formate, endo-fenchyl formate, and exo-isofenchyl formate.
6. A method as claimed in claim 1 in which the ester is endo-fenchyl formate or exo-norbornyl formate.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7411268A SE384883B (en) | 1974-09-06 | 1974-09-06 | WAY TO INCREASE THE CELLULOSE YIELD WHEN SULPHITE BOILING OF WOOD |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1057008A true CA1057008A (en) | 1979-06-26 |
Family
ID=20322071
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA234,872A Expired CA1057008A (en) | 1974-09-06 | 1975-09-05 | Method in sulphite pulping |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5153002A (en) |
| AT (1) | AT344498B (en) |
| CA (1) | CA1057008A (en) |
| CH (1) | CH600036A5 (en) |
| DE (1) | DE2537785A1 (en) |
| FI (1) | FI58521C (en) |
| FR (1) | FR2283988A1 (en) |
| NO (1) | NO144577C (en) |
| SE (1) | SE384883B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2816473A1 (en) * | 1978-04-15 | 1979-10-25 | Bayer Ag | DISPERSION FOR USE IN CELL PROCESSING |
| DE2827111A1 (en) * | 1978-06-21 | 1980-01-10 | Bayer Ag | AGENTS FOR USE IN CELL PROCESSING |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE336535C (en) * | 1919-12-02 | 1921-05-03 | Zellstoff Und Papierfabrikatio | Process for the production of the purest cellulose with a cotton or wool-like texture from vegetables using acidic sulphite liquors |
-
1974
- 1974-09-06 SE SE7411268A patent/SE384883B/en unknown
-
1975
- 1975-08-25 DE DE19752537785 patent/DE2537785A1/en not_active Withdrawn
- 1975-08-27 CH CH1108775A patent/CH600036A5/xx not_active IP Right Cessation
- 1975-09-01 AT AT670575A patent/AT344498B/en not_active IP Right Cessation
- 1975-09-03 NO NO753029A patent/NO144577C/en unknown
- 1975-09-04 FR FR7527116A patent/FR2283988A1/en active Granted
- 1975-09-05 FI FI752508A patent/FI58521C/en not_active IP Right Cessation
- 1975-09-05 CA CA234,872A patent/CA1057008A/en not_active Expired
- 1975-09-05 JP JP50108467A patent/JPS5153002A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| FR2283988B1 (en) | 1978-12-08 |
| FI752508A (en) | 1976-03-07 |
| CH600036A5 (en) | 1978-06-15 |
| SE7411268L (en) | 1976-03-08 |
| FI58521B (en) | 1980-10-31 |
| SE384883B (en) | 1976-05-24 |
| NO753029L (en) | 1976-03-09 |
| AT344498B (en) | 1978-07-25 |
| NO144577B (en) | 1981-06-15 |
| ATA670575A (en) | 1977-11-15 |
| NO144577C (en) | 1981-09-23 |
| FR2283988A1 (en) | 1976-04-02 |
| JPS5153002A (en) | 1976-05-11 |
| FI58521C (en) | 1981-02-10 |
| DE2537785A1 (en) | 1976-03-18 |
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