US1935579A - Two-step chemical process of fiber liberation - Google Patents
Two-step chemical process of fiber liberation Download PDFInfo
- Publication number
- US1935579A US1935579A US428838A US42883830A US1935579A US 1935579 A US1935579 A US 1935579A US 428838 A US428838 A US 428838A US 42883830 A US42883830 A US 42883830A US 1935579 A US1935579 A US 1935579A
- Authority
- US
- United States
- Prior art keywords
- liquor
- cooking
- wood
- alkaline
- sulphite
- 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 - Lifetime
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
- D21C3/26—Multistage processes
Definitions
- An object of the present invention is to make possible the utilization of highly resinous species of woods, such as long leaf yellow pine, in the production of high grade pulps which are characterized by physical characteristics, including strength and tear resistance, approximating those of kraft pulp, but which possess the important advantage over kraft pulp in that they are more easily bleachable.
- Another object of the present invention is to produce such pulp in a practical period of time and without the use of temperatures higher than'those ordinarily employed in the soda or kraft process.
- the wood employed as a raw material is initially cooked short of fiber liberation in a suitable alkaline liquor, preferably in a kraft liquor, whereupon fiber liberation is completed in a neutral or only slightly alkaline sulphite liquor.
- a suitable alkaline liquor preferably in a kraft liquor
- fiber liberation is completed in a neutral or only slightly alkaline sulphite liquor.
- a significant advantage of the process of the present invention is that both cooking steps may be accomplished in a single alkaline digester, as neither cooking liquor is acid. After the initial cooking operation, the spent alkaline liquor may be discharged from the digester and, while the wood is still hot, the fresh sulphite liquor may be run into the digester, preferably in heated condition, so as to avoid cooling of the wood.
- a liquor of much'lower alkalinity than that used in the usual soda or kraft process may be employed.
- the chipped wood may be placed in an alkaline ,digester together with an alkaline liquor containing 0.5 to 1.0 pounds of active alkali per cubic foot, which represents an alkali content of about half that present in the usual soda or kraft process.
- the alkali may be present in the form of either caustic soda or sodium sulphide, it is preferable to use a mixture of both these alkalies, about 30% to 40% being present as sodium sulphide, as in the usual kraft process.
- the charge of chips and liquor is confined in the digester and is cooked at a temperature of, say, 300 to 350 F. for about two to four hours, at the end of which time the chips are brown and somewhat softer than the original wood, Whereas the cooking liquor is dark brown.
- the chips are separated from the spent liquor by opening the blow pipe valve at the bottom of the digester and permitting free liquor to drain from the chips.
- the chips are preferably'washed, but this step may be omitted, if desired.
- the blow pipe valve is then closed and a suitable sulphite liquor, preferably in hot condition, is added to the digester, whereupon the digester contents are confined.
- the liquor should contain about 5% to 10% of a soluble sulphite, preferably sodium sulphite, so that fiber liberation may be effected in a reasonable period of time without requiring excessive temperatures.
- a soluble sulphite preferably sodium sulphite
- the digester contents are ,heated to temperatures of from 300 to 350 F., and cooking at these temperatures is continued from two to six hours to accomplish the desired completion of fiber liberation.
- the resulting pulp is then washed free of spent liquor and may be bleached or otherwise chemically treated before being used in the manufacture of paper or other ultimate products.
- the spent liquor resulting from the initial cooking operation contains a large amount of resin soap resulting from the saponification of most of the resin content of the wood.
- the cooked wood being relatively free from resins, is much more readily reacted upon by the sodium sulphite solution to produce a pulp than is the case whenno initial treatment such as described is efiected.
- the product not only has strength and tear resistance practically as good as kraft pulp, but is more readily bleachable than kraft pulp, doubtless as a result of the high reactivity of sodium sulphite upon residual lignin present in the wood after.
- the initial cooking operation If the initial cooking operation is carried out with weaker liquors, or at lower temperatures than those prescribed in the example, the resulting pulp has a tear resistance lower than that of kraft pulp, and its other characteristics approach those of pulps produced by cooking only in sodium sulphite liquors.
- the wood chips may first be cooked in the weak alkaline solution at the desired temperature for the requisite period of time, whereupon the desired amount of sodium sulphite liquor may be pumped into the digester without draining the initial liquor from the chips, and cooking in the sulphite liquor may then be effected to complete fiber liberation.
- the sodium sulphite liquor may be added in the form of a highly concentrated solution, in order that it may be accommodated by the free space in the digester. Such a procedure is advantageous, especially when the resulting pulp is not to be bleached, as the heat content of the liquor is conserved, the process simplified, and all the sodium constituent recovered from a single waste liquor of comparatively high concentration in sodium and organic constituents.
- the sulphite liquor used for the second cooking operation should be non-acid, by which is meant that it may be neutral or slightly alkaline. As already pointed out, such a liquor not only makes possible the production of a high grade product, but may be used satisfactorily in the usual alkaline digester, so that there is no necessity for removing the chips :from the digester after the initial digestion, a procedure which would be difiicult and expensive in actual practice.
- a process which comprises cooking raw cellulosic material short of fiber liberation in an alkaline, sodium base liquor, separating the liquor from the cooked material, and then cooking the material to complete fiber liberation in a substantion, removing only the cooking liquor from the.
- a process of producing pulp from a resinous- Wood which comprises initially cooking chips of such wood in an alkaline, sodium base cooking liquor to effect a saponification of most of the resin content while maintaining the wood in chip form, and then cooking the chips in a substantially neutral solution of essentially only sodium sulphite to complete fiber liberation.
- a process which comprises cooking chipped wood in a sodium base, alkaline liquor short of fiber liberation, and then cooking in a substantially neutral solution of essentially only sodium sulphite to complete fiber liberation.
- a process which comprises cooking chipped wood in-a kraft cooking liquor short of fiber liberation, and then cooking in a substantially neutral solution of essentially only sodium sulphite to complete fiber liberation.
- a process which comprises cooking chipped wood short of fiber liberation in an alkaline sodium base liquor made up essentially of caustic soda and sodium sulphide with the caustic soda somewhat preponderating in amount, and then cooking to complete fiber liberation in a substantially neutral solution of essentially only sodium sulphite.
- a process which comprises cooking chipped wood short of fiber liberation in an alkaline sodium base liquor made up essentially of caustic soda and sodium sulphide with the caustic soda somewhat preponderating in amount, and then cooking in a substantially neutral solution of essentially only sodium sulphite of about 5% to 10% strength at about 300 to 350 F., for about two to six hours, thereby producing a completely liberated wood pulp of easy bleachability.
Description
Patented Nov. 14, 1933 UNITED STATES PATENT- OFFICE TWO-STEP CHEMICAL PROCESS OF l IBER LIBERATION George A. Richter, Berlin, N. H., assignor to Brown Company, Berlin, N. H., a corporation of Maine,
No Drawing. Application February 15, 1930 Serial No. 428,838
7 Claims.
as used as a raw material in the papermaking and cellulose derivative industries.
An object of the present invention is to make possible the utilization of highly resinous species of woods, such as long leaf yellow pine, in the production of high grade pulps which are characterized by physical characteristics, including strength and tear resistance, approximating those of kraft pulp, but which possess the important advantage over kraft pulp in that they are more easily bleachable. Another object of the present invention is to produce such pulp in a practical period of time and without the use of temperatures higher than'those ordinarily employed in the soda or kraft process.
In accordance with the process of the present invention, the wood employed as a raw material is initially cooked short of fiber liberation in a suitable alkaline liquor, preferably in a kraft liquor, whereupon fiber liberation is completed in a neutral or only slightly alkaline sulphite liquor. Such a two-step. chemical process of fiber liberation may be practised to advantage upon various types of woods but is especially advantageous in the case of woods of high resin content, as the alkaline liquor used inthe initial cooking operation saponifies most of the resins present in the wood, whereupon fiber liberation into a high grade bleachable product may be readily efiected in a neutral or slightly alkaline sulphite liquor, because of the reactivity of the sulphite with residual lignin present in the wood. A significant advantage of the process of the present invention is that both cooking steps may be accomplished in a single alkaline digester, as neither cooking liquor is acid. After the initial cooking operation, the spent alkaline liquor may be discharged from the digester and, while the wood is still hot, the fresh sulphite liquor may be run into the digester, preferably in heated condition, so as to avoid cooling of the wood.
In carrying out the initial step of the present process, a liquor of much'lower alkalinity than that used in the usual soda or kraft process may be employed. For instance, the chipped wood may be placed in an alkaline ,digester together with an alkaline liquor containing 0.5 to 1.0 pounds of active alkali per cubic foot, which represents an alkali content of about half that present in the usual soda or kraft process. While the alkali may be present in the form of either caustic soda or sodium sulphide, it is preferable to use a mixture of both these alkalies, about 30% to 40% being present as sodium sulphide, as in the usual kraft process. The charge of chips and liquor is confined in the digester and is cooked at a temperature of, say, 300 to 350 F. for about two to four hours, at the end of which time the chips are brown and somewhat softer than the original wood, Whereas the cooking liquor is dark brown. The chips are separated from the spent liquor by opening the blow pipe valve at the bottom of the digester and permitting free liquor to drain from the chips. The chips are preferably'washed, but this step may be omitted, if desired. The blow pipe valve is then closed and a suitable sulphite liquor, preferably in hot condition, is added to the digester, whereupon the digester contents are confined. The liquor should contain about 5% to 10% of a soluble sulphite, preferably sodium sulphite, so that fiber liberation may be effected in a reasonable period of time without requiring excessive temperatures. The digester contents are ,heated to temperatures of from 300 to 350 F., and cooking at these temperatures is continued from two to six hours to accomplish the desired completion of fiber liberation. The resulting pulp is then washed free of spent liquor and may be bleached or otherwise chemically treated before being used in the manufacture of paper or other ultimate products.
When woods of high resin content, such as long leaf yellow pine or other conifers, are processed as hereinbefore described, the spent liquor resulting from the initial cooking operation contains a large amount of resin soap resulting from the saponification of most of the resin content of the wood. The cooked wood, being relatively free from resins, is much more readily reacted upon by the sodium sulphite solution to produce a pulp than is the case whenno initial treatment such as described is efiected. When the process is carried out under the conditions hereinbefore described, the product not only has strength and tear resistance practically as good as kraft pulp, but is more readily bleachable than kraft pulp, doubtless as a result of the high reactivity of sodium sulphite upon residual lignin present in the wood after. the initial cooking operation. If the initial cooking operation is carried out with weaker liquors, or at lower temperatures than those prescribed in the example, the resulting pulp has a tear resistance lower than that of kraft pulp, and its other characteristics approach those of pulps produced by cooking only in sodium sulphite liquors.
If desired, the wood chips may first be cooked in the weak alkaline solution at the desired temperature for the requisite period of time, whereupon the desired amount of sodium sulphite liquor may be pumped into the digester without draining the initial liquor from the chips, and cooking in the sulphite liquor may then be effected to complete fiber liberation. The sodium sulphite liquor may be added in the form of a highly concentrated solution, in order that it may be accommodated by the free space in the digester. Such a procedure is advantageous, especially when the resulting pulp is not to be bleached, as the heat content of the liquor is conserved, the process simplified, and all the sodium constituent recovered from a single waste liquor of comparatively high concentration in sodium and organic constituents. Even if all the active alkali used in the first cooking step is not consumed before the addition of the sodium sulphite, it does not interfere with the liberation of fiber accomplished by the second cooking step. The withdrawal of the spent alkaline liquor at the end of the first cooking step improves the bleachability of the final pulp, but in those cases where bleachability of the resulting pulp isnot an important factor, it is possible, by adding the sodium sulphite to the spent alkaline cooking liquor associated with the wood chips after the initial cooking step, to effect a saving of time, heat, and labor.
The sulphite liquor used for the second cooking operation should be non-acid, by which is meant that it may be neutral or slightly alkaline. As already pointed out, such a liquor not only makes possible the production of a high grade product, but may be used satisfactorily in the usual alkaline digester, so that there is no necessity for removing the chips :from the digester after the initial digestion, a procedure which would be difiicult and expensive in actual practice.
I claim:
1. A process which comprises cooking raw cellulosic material short of fiber liberation in an alkaline, sodium base liquor, separating the liquor from the cooked material, and then cooking the material to complete fiber liberation in a substantion, removing only the cooking liquor from the.
digester, introducing a substantially neutral solution of essentially only a sulphite thereinto, and cooking the material in said solution to complete fiber liberation.
3. A process of producing pulp from a resinous- Wood, which comprises initially cooking chips of such wood in an alkaline, sodium base cooking liquor to effect a saponification of most of the resin content while maintaining the wood in chip form, and then cooking the chips in a substantially neutral solution of essentially only sodium sulphite to complete fiber liberation.
l. A process which comprises cooking chipped wood in a sodium base, alkaline liquor short of fiber liberation, and then cooking in a substantially neutral solution of essentially only sodium sulphite to complete fiber liberation.
5. A process which comprises cooking chipped wood in-a kraft cooking liquor short of fiber liberation, and then cooking in a substantially neutral solution of essentially only sodium sulphite to complete fiber liberation.
6. A process which comprises cooking chipped wood short of fiber liberation in an alkaline sodium base liquor made up essentially of caustic soda and sodium sulphide with the caustic soda somewhat preponderating in amount, and then cooking to complete fiber liberation in a substantially neutral solution of essentially only sodium sulphite.
'7. A process which comprises cooking chipped wood short of fiber liberation in an alkaline sodium base liquor made up essentially of caustic soda and sodium sulphide with the caustic soda somewhat preponderating in amount, and then cooking in a substantially neutral solution of essentially only sodium sulphite of about 5% to 10% strength at about 300 to 350 F., for about two to six hours, thereby producing a completely liberated wood pulp of easy bleachability.
GEORGE A. RICHTER.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US428838A US1935579A (en) | 1930-02-15 | 1930-02-15 | Two-step chemical process of fiber liberation |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US428838A US1935579A (en) | 1930-02-15 | 1930-02-15 | Two-step chemical process of fiber liberation |
Publications (1)
Publication Number | Publication Date |
---|---|
US1935579A true US1935579A (en) | 1933-11-14 |
Family
ID=23700598
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US428838A Expired - Lifetime US1935579A (en) | 1930-02-15 | 1930-02-15 | Two-step chemical process of fiber liberation |
Country Status (1)
Country | Link |
---|---|
US (1) | US1935579A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4269859A (en) * | 1979-04-19 | 1981-05-26 | Brown Company | Cellulose floc granules and process |
-
1930
- 1930-02-15 US US428838A patent/US1935579A/en not_active Expired - Lifetime
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4269859A (en) * | 1979-04-19 | 1981-05-26 | Brown Company | Cellulose floc granules and process |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US1848661A (en) | of berlin | |
US2528350A (en) | Two-step digestion of hardwoods | |
US1880043A (en) | Production of high grade chemical pulps | |
US1935579A (en) | Two-step chemical process of fiber liberation | |
US1831032A (en) | Production of refined wood pulp | |
US1640853A (en) | Process of producing pulp having a high percentage of resistant cellulose | |
US1880042A (en) | Acid process of fiber liberation | |
US2694631A (en) | Process of preparing wood pulp | |
US1787953A (en) | Processing of raw cellulosic materials | |
US1880044A (en) | Process of alkaline fiber liberation | |
US1735013A (en) | Process of pulping raw cellulosic material | |
US1830421A (en) | Manufacture of pulp and paper from resinous woods | |
US1974751A (en) | Chemical pulping process | |
US2049567A (en) | Manufacture of paper pulp | |
US3773611A (en) | Two-stage sodium sulfite-oxygen pulping | |
US2906659A (en) | High yields bisulphite pulping process | |
US2190193A (en) | Chemical wood-pulping process | |
US1809286A (en) | Pulp of high whiteness and strength and process of producing same | |
US2459570A (en) | Method of refining sulfate turpentine | |
US1864620A (en) | Process of liberating pulp from raw cellulosic materials | |
US1867593A (en) | Process of chemical fiber liberation | |
US2018937A (en) | Paper pulp and method of making the same | |
US1811864A (en) | Process of liberating fiber from bagasse or like stalks | |
US1880048A (en) | Multistage process of pulping raw cellulosic material | |
US2747995A (en) | Method of pulp production |