US3262839A - Neutral to weakly alkaline sulfite process for the extraction of cellulose from cellulosic material - Google Patents

Neutral to weakly alkaline sulfite process for the extraction of cellulose from cellulosic material Download PDF

Info

Publication number
US3262839A
US3262839A US231558A US23155862A US3262839A US 3262839 A US3262839 A US 3262839A US 231558 A US231558 A US 231558A US 23155862 A US23155862 A US 23155862A US 3262839 A US3262839 A US 3262839A
Authority
US
United States
Prior art keywords
sulfite
neutral
cellulose
wood chips
wood
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
Application number
US231558A
Inventor
Luthgens Manfred
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
GEA Group AG
Original Assignee
Metallgesellschaft AG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Metallgesellschaft AG filed Critical Metallgesellschaft AG
Application granted granted Critical
Publication of US3262839A publication Critical patent/US3262839A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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
    • D21C3/04—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

Definitions

  • the present invention generally relates to the release of cellulose fibers from solid cellulosic materials, and more particularly, to an improvement in the neutral to weakly alkaline sulfite process used for extracting cellulose from solid cellulosic material.
  • alkaline digestion the most common example of which is the sulfate process.
  • This process essentially comprises the use of a strongly alkaline solution consisting essentially of NaOH or other alkalis such as sulfides or polysulfides having a pH value greater than 12.
  • sulfate process essentially comprises the use of a strongly alkaline solution consisting essentially of NaOH or other alkalis such as sulfides or polysulfides having a pH value greater than 12.
  • sulfides or polysulfides having a pH value greater than 12.
  • the cellulose fibers have good strength properties but poor whiteness qualities. Accordingly, expensive and time consuming bleaching processes must be employed in order to obtain a proper whiteness of the cellulose fibers for use in the manufacture of high grade papers.
  • cellulose fibers having a greater whiteness use is made of a second group of processes which comprise sulfite processes wherein the main digestive agent is S0 in free and/or combined form. While the cellulose fibers produced by these processes are much whiter than the cellulose fibers produced by the alkalis, the fibers are generally not as strong as the fibers produced I by the alkaline processes.
  • the main disadvantage of this process is the relatively poor quality of the pulp product which must invariably be mechanically fiberized in order to separate the fibers.
  • the process of the present invention comprises the reduction of logs of wood as supplied to the mill to a consistency of fairly small chips, cooking the chips with a hot aqueous solution, commonly referred to as liquor, cooking the chips and liquor under pressure so that the pulping agent component of the liquor attacks the lignins and other organic material in the wood releasing the cellulose for washing, filtering and refining and making into paper or other uses.
  • the required time for the digestion is appreciably lower than for the conventional methods and ranges between 5 and 30 minutes with a usual period of between 8 to 10 minutes.
  • the time required for the process of the present invention is less than that required for the production of semichemical pulp or for carrying out the alkaline digestion process at higher temperatures and with a thorough preliminary impregnation.
  • the resulting cellulose fibers are of a considerably better quality and no mechanical fiberizing is required.
  • the digestion liquors may comprise solutions of alkaline sulfites or bisulfites with additions such as Na CO NaHCO and/or preferably NaOI-I, NaHS, Na S O N328, NAS or other polysulfides.
  • the pH value of the digestion liquors at the beginning of the cooking process ranges between 7.0 and 11.5, preferably between 7 to 10.
  • the digestion or cooking temperature is between 200 and 280 C., and preferably between 225 and 280 C. This temperature is generally higher than permissible in previously known and conventional processes.
  • the thorough preliminary impregnation of the present process can be accomplished by known methods by the use of steam or vacuum, by mechanical or hydraulic pressure, or by agitation, or by any combination of those steps.
  • the wood chips Prior to the impregnation of the crude cellulose material with the digestion liquir the wood chips may be treated with steam or subjected to a vacuum.
  • the cellulosic raw material may be subjected to an initial comminution to form wood chips having a maximum length of 25 mm., and a maximum thickness of 5 mm. A minimum length of 3 mm. and a minimum thickness of about 0.5 mm. is advisable. This will result in obtaining cellulose fibers having a greater strength.
  • While the present invention is essentially directed to the use of wood, other cellulosic materials are not excluded. Such other cellulosic materials having various chip sizes and comprising, for example, waste material from plants, grasses, bamboo, can be used for producing cellulose fibers of a good quality according to the present invention.
  • the present invention also has the advantage of making possible the production of cellulose pulp having optimum qualities and good whiteness even by the use of digestion liquors containing substantial quantities of Na S O These quantities may range up to 60% of the total chemical content of the liquor. In the known sulfite processes darker grades of cellulose pulps are produced by such small quantities of Na S O' as 2%. In the process of the present invention the presence of a relatively small quantity of Na S and/ or polysulfides does not have any detrimental effects on the produced cellulose fibers.
  • this process has the further advantage of a high production rate.
  • Example Comminuted pine wood chips having an average length of 15 mm. and an average thickness of 2 mm. were deposited in an autoclave and steamed for about 2 minutes under a pressure of 6 atmospheres. The wood was accordingly quickly heated and the entrapped air was driven out of thewood. The digestion liquor which was heated to about 250? C. was then introduced into the autoclave. This liquor had the following composition:

Landscapes

  • Paper (AREA)

Description

United States Patent 3,262,839 NEUTRAL TO WEAKLY ALKALINE SULFITE PROCESS FOR THE EXTRACTION OF CELLU- LOSE FROM CELLULOSIC MATERIAL Manfred Liithgens, Frankfurt am Main, Germany, assignor to Metallgesellschaft Aktiengesellschaft, Frankfurt am Main, Germany No Drawing. FiledOct. 18, 1962, Ser. No. 231,558 Claims priority, application Germany, Oct. 20, 1961, M 50,639 2 Claims. (Cl. 162-83) The present invention generally relates to the release of cellulose fibers from solid cellulosic materials, and more particularly, to an improvement in the neutral to weakly alkaline sulfite process used for extracting cellulose from solid cellulosic material.
In the pulping of cellulosic materials in order to obtain cellulose fibers for different uses, various processes have been devised which may be generally classified into three groups. One such group may be termed alkaline digestion the most common example of which is the sulfate process. This process essentially comprises the use of a strongly alkaline solution consisting essentially of NaOH or other alkalis such as sulfides or polysulfides having a pH value greater than 12. As a result of this process the cellulose fibers have good strength properties but poor whiteness qualities. Accordingly, expensive and time consuming bleaching processes must be employed in order to obtain a proper whiteness of the cellulose fibers for use in the manufacture of high grade papers.
In order to obtain cellulose fibers having a greater whiteness, use is made of a second group of processes which comprise sulfite processes wherein the main digestive agent is S0 in free and/or combined form. While the cellulose fibers produced by these processes are much whiter than the cellulose fibers produced by the alkalis, the fibers are generally not as strong as the fibers produced I by the alkaline processes.
Within recent years a third group of processes has gained technical importance, which processes may be generally described as the neutral sulfite digestion process. In this process the solution has an alkalinity which is so selected that at the end of the cooking process the liquor will have been rendered neutral by the acids liberated during the cooking process. Generally, this process has been previously used only for the production of so-called semichemical pulps. These are pulps containing appreciable amounts of lignin. The main advantages of this group of processes are the relatively high yields and the short reaction times of to 20 minutes as compared to the 8 to 11 hours for the sulfiteprocess, or 2 /2 to 8 hours of the alkaline process.
The main disadvantage of this process is the relatively poor quality of the pulp product which must invariably be mechanically fiberized in order to separate the fibers.
In the alkaline digestion process it has been proposed to reduce the cooking time by a preliminary impregnation of the cellulosic materials with the cooking liquor, sometimes supported by a steam treatment preceding the preliminary impregnation of the cellulosic materials so as to eifect digestion at temperatures up to 220 to 225 C. which are above those generally used for this purpose. In comparison, in the usual sulfite process the temperature ranges from 135 to 175 C. and in the alkaline and neutural sulfite processes the temperature is increased to only about 185 C.
It is therefore a principal object of the present invention to provide an improved neutral to weakly alkaline sulfite process for the extraction of cellulose fibers from cellulosic materials.
lCC
It is another object of the present invention to provide a neutral sulfite process wherein the resulting cellulose fibers have improved strength properties or greater whiteness than was previously obtainable.
It is a further object to attain a fast digestion in order to be able to operate with small apparatus thereby obtaining a high production rate.
Generally speaking, the process of the present invention comprises the reduction of logs of wood as supplied to the mill to a consistency of fairly small chips, cooking the chips with a hot aqueous solution, commonly referred to as liquor, cooking the chips and liquor under pressure so that the pulping agent component of the liquor attacks the lignins and other organic material in the wood releasing the cellulose for washing, filtering and refining and making into paper or other uses.
It has been unexpectedly found that by a thorough preliminary impregnation of the cellulosic material with the cooking liquor and subsequently cooking the impregnated cellulosic material at greater temperatures it is possible to obtain by the neutral to weakly alkaline sulfite process cellulose fibers having improved strength properties or greater whiteness than was previously the case. Reasons for these unexpected results are not as yet fully known, but the results have been verified through numerous experiments an example of which will be described subsequently.
As a further result of the process of this invention the required time for the digestion is appreciably lower than for the conventional methods and ranges between 5 and 30 minutes with a usual period of between 8 to 10 minutes. Thus, the time required for the process of the present invention is less than that required for the production of semichemical pulp or for carrying out the alkaline digestion process at higher temperatures and with a thorough preliminary impregnation. Further, the resulting cellulose fibers are of a considerably better quality and no mechanical fiberizing is required.
The digestion liquors may comprise solutions of alkaline sulfites or bisulfites with additions such as Na CO NaHCO and/or preferably NaOI-I, NaHS, Na S O N328, NAS or other polysulfides. The pH value of the digestion liquors at the beginning of the cooking process ranges between 7.0 and 11.5, preferably between 7 to 10. The digestion or cooking temperature is between 200 and 280 C., and preferably between 225 and 280 C. This temperature is generally higher than permissible in previously known and conventional processes.
The thorough preliminary impregnation of the present process can be accomplished by known methods by the use of steam or vacuum, by mechanical or hydraulic pressure, or by agitation, or by any combination of those steps.
Prior to the impregnation of the crude cellulose material with the digestion liquir the wood chips may be treated with steam or subjected to a vacuum.
In order to further reduce the digestion time, the cellulosic raw material may be subjected to an initial comminution to form wood chips having a maximum length of 25 mm., and a maximum thickness of 5 mm. A minimum length of 3 mm. and a minimum thickness of about 0.5 mm. is advisable. This will result in obtaining cellulose fibers having a greater strength.
While the present invention is essentially directed to the use of wood, other cellulosic materials are not excluded. Such other cellulosic materials having various chip sizes and comprising, for example, waste material from plants, grasses, bamboo, can be used for producing cellulose fibers of a good quality according to the present invention.
The present invention also has the advantage of making possible the production of cellulose pulp having optimum qualities and good whiteness even by the use of digestion liquors containing substantial quantities of Na S O These quantities may range up to 60% of the total chemical content of the liquor. In the known sulfite processes darker grades of cellulose pulps are produced by such small quantities of Na S O' as 2%. In the process of the present invention the presence of a relatively small quantity of Na S and/ or polysulfides does not have any detrimental effects on the produced cellulose fibers.
Because of the short cooking time required for the present invention, this process has the further advantage of a high production rate.
In order to set forth a specific embodiment of the present invention, the following example is disclosed in detail but it is not considered to be limiting of the invention but is disclosed merely for illustrative purposes.
Example Comminuted pine wood chips having an average length of 15 mm. and an average thickness of 2 mm. were deposited in an autoclave and steamed for about 2 minutes under a pressure of 6 atmospheres. The wood was accordingly quickly heated and the entrapped air was driven out of thewood. The digestion liquor which was heated to about 250? C. was then introduced into the autoclave. This liquor had the following composition:
G./1. Sodium sulfite -L. 50 Sodium sulfide 10 and Paper Industry (Tappi) Standards T 220 m. 60,
Critical Testing of Pulp Hand Sheets. The following values were obtained with a freeness of 35" SR:
Tensile breaking length, m. 12,200
Burst factor 105 Tear strength 97 Folds, no. 5,050
It will be understood that this invention is susceptible to modifications in order to adapt it to different usages and conditions, and accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.
What is claimed is:
1. In the process of the neutral to weakly alkaline sulfite type for extracting cellulose fibers from wood, the steps of comminuting the wood to wood chips having an' average length of about 15 mm. and an average thickness of about 2 mm.; removing air from said wood chips; thoroughly impregnating the resultant air-freed wood chips with a sulfite solution having a pH value between 7 and 11.5, said sulfite solution having a concentration of about g./l. sodium sulfite and about 10 g./1. sodium sulfide, the weight ratio of the sulfite solution to the wood chips being about 5:1, respectively; and digesting the resultant impregnated wood chips at 200-280 C. for 5-30 minutes.
2. The process of claim 1, wherein the digestion step is conducted at 225-280 C. and for a time of about 8-10 minutes.
References Cited by the Examiner UNITED STATES PATENTS 1,880,046 9/1932 Richter 162-83 2,736,635 2/1956 Haywood 16283 2,924,547 2/1960 Knapp 162-83 3,046,182 7/1962 Tomlinson "162-83 FOREIGN PATENTS 710,257 6/1954 Great Britain.
OTHER REFERENCES Hatfner, Douglas Fir as a Pulpwood, Paper Trade Journal, pp. 93-98, Aug. 29, 1940.
DONALL H. SYLVESTER, Primary Examiner.
MORRIS O. WOLK, Examiner.
H. R. CAINE, Assistant Examiner.

Claims (1)

1. IN THE PROCESS OF THE NEUTRAL TO WEAKLY ALKALINE SULFITE TYPE FOR EXTRACTING CELLULOSE FIBERS FROM WOOD, THE STEPS OF COMMINUTING THE WOOD TO WOOD CHIPS HAVING AN AVERAGE LENGTH OF ABOUT 15 MM. AND AN AVERAGE THICKNESS OF ABOUT 2 MM.; REMOVING AIR FROM SAID WOOD CHIPS; THROUGHLY IMPREGNATING THE RESULTANT AIR-FREED WOOD CHIPS WITH A SULFITE SOLUTION HAVING A PH VALUE BETWEEN 7 AND 11.5, SAID SULFITE SOLUTION HAVING A CONCENTRATION OF ABOUT 50 G./1. SODIUM SULFITE AND ABOUT 10 G./1. SODIUM SULFIDE, THE WEIGHT RATIO OF THE SULFITE SOLUTION TO THE WOOD CHIPS BEING ABOUT 5:1, RESPECTIVELY; AND DIGESTING THE RESULTANT IMPREGNATED WOOD CHIPS AT 200-280*C. FOR 5-30 MINUTES.
US231558A 1961-10-20 1962-10-18 Neutral to weakly alkaline sulfite process for the extraction of cellulose from cellulosic material Expired - Lifetime US3262839A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEM50639A DE1198666B (en) 1961-10-20 1961-10-20 Process for the production of pulp

Publications (1)

Publication Number Publication Date
US3262839A true US3262839A (en) 1966-07-26

Family

ID=7306905

Family Applications (1)

Application Number Title Priority Date Filing Date
US231558A Expired - Lifetime US3262839A (en) 1961-10-20 1962-10-18 Neutral to weakly alkaline sulfite process for the extraction of cellulose from cellulosic material

Country Status (2)

Country Link
US (1) US3262839A (en)
DE (1) DE1198666B (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3530112A (en) * 1967-07-24 1970-09-22 Itt Rayonier Inc Process for preparing dispersants useful in hydraulic cement slurries
US3923591A (en) * 1972-03-21 1975-12-02 Process Evaluation Devel Prehydrolysis and digestion of fibrous lignocellulosic material
US4141787A (en) * 1974-09-24 1979-02-27 Pwa Papierwerke Waldhof-Aschaffenburg Aktiengesellschaft Process for preparing chemical cellulose according to the sulfite process by increasing the total SO2 content of cooking acid with liquid SO2 and digesting wood chips
US4456750A (en) * 1982-02-11 1984-06-26 A.Ahlstrom Osakeyhtio Method for controlling the alkalinity of feed circulation when prehydrolyzing wood chips
US4786365A (en) * 1984-10-10 1988-11-22 Svenska Traforskningsinstitutet Process of making cellulose pulp with a sulphite cooking liquor containing sulphide and a quinone or hydroquinone compound
US5882476A (en) * 1995-05-05 1999-03-16 Solvay Minerals, Inc. Deinking printed wastepaper using alkaline solution containing sodium sulfite and sodium carbonate

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1880046A (en) * 1930-09-06 1932-09-27 Brown Co Processing of cellulose fiber
GB710257A (en) * 1949-11-08 1954-06-09 Celanese Corp Wood pulp
US2736635A (en) * 1951-07-07 1956-02-28 Ionics Method of producing sulfite cooking liquors and recovering valuable constituents therefrom
US2924547A (en) * 1954-11-08 1960-02-09 Hawaiian Dev Company Ltd Rapid neutral sulfite process for pulping bagasse and other non-woody plant lignocellulose
US3046182A (en) * 1956-01-13 1962-07-24 Smith Paper Mills Ltd Howard Sulphite pulping process

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA399572A (en) * 1937-11-19 1941-09-30 D. Merrill Albert Cellulosic material treating apparatus

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1880046A (en) * 1930-09-06 1932-09-27 Brown Co Processing of cellulose fiber
GB710257A (en) * 1949-11-08 1954-06-09 Celanese Corp Wood pulp
US2736635A (en) * 1951-07-07 1956-02-28 Ionics Method of producing sulfite cooking liquors and recovering valuable constituents therefrom
US2924547A (en) * 1954-11-08 1960-02-09 Hawaiian Dev Company Ltd Rapid neutral sulfite process for pulping bagasse and other non-woody plant lignocellulose
US3046182A (en) * 1956-01-13 1962-07-24 Smith Paper Mills Ltd Howard Sulphite pulping process

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3530112A (en) * 1967-07-24 1970-09-22 Itt Rayonier Inc Process for preparing dispersants useful in hydraulic cement slurries
US3923591A (en) * 1972-03-21 1975-12-02 Process Evaluation Devel Prehydrolysis and digestion of fibrous lignocellulosic material
US4141787A (en) * 1974-09-24 1979-02-27 Pwa Papierwerke Waldhof-Aschaffenburg Aktiengesellschaft Process for preparing chemical cellulose according to the sulfite process by increasing the total SO2 content of cooking acid with liquid SO2 and digesting wood chips
US4456750A (en) * 1982-02-11 1984-06-26 A.Ahlstrom Osakeyhtio Method for controlling the alkalinity of feed circulation when prehydrolyzing wood chips
US4786365A (en) * 1984-10-10 1988-11-22 Svenska Traforskningsinstitutet Process of making cellulose pulp with a sulphite cooking liquor containing sulphide and a quinone or hydroquinone compound
US5882476A (en) * 1995-05-05 1999-03-16 Solvay Minerals, Inc. Deinking printed wastepaper using alkaline solution containing sodium sulfite and sodium carbonate

Also Published As

Publication number Publication date
DE1198666B (en) 1965-08-12

Similar Documents

Publication Publication Date Title
US4294653A (en) Process for manufacturing chemimechanical cellulose pulp in a high yield within the range from 65 to 95%
US4486267A (en) Chemithermomechanical pulping process employing separate alkali and sulfite treatments
US3707436A (en) Exploding of ammonia impregnated wood chips
US4087317A (en) High yield, low cost cellulosic pulp and hydrated gels therefrom
KR100694840B1 (en) Manufacturing method of mechanical pulp from cornstalk
US4116758A (en) Method of producing high yield chemimechanical pulps
US2169473A (en) Method of producing cellulose pulp
JPS61275489A (en) Production of bleached chemimechanical and semichemical fiber pulp by two-stage impregnation method
US3919041A (en) Multi-stage chlorine dioxide delignification of wood pulp
US3262839A (en) Neutral to weakly alkaline sulfite process for the extraction of cellulose from cellulosic material
US3829357A (en) Oxidative manufacture of pulp with chlorine dioxide
AU2002244309B8 (en) Method for producing pulp
US3532597A (en) Preparation of dissolving pulps from wood by hydrolysis and alkaline sulfite digestion
AU2002244309A1 (en) Method for producing pulp
US3558428A (en) Method in the manufacture of chemomechanical pulps
US3737369A (en) Alkaline digestion of a mixture of cotton linters and fibrous vegetable material and product thereof
US3013932A (en) Printing paper and process of making the same
US3013931A (en) Printing paper and process of making the same
EP0030778B1 (en) Process for the formation of refiner pulp
US3591451A (en) Pretreatment of vegetable matter and delignification of the refined matter with chloring dioxide
US3520773A (en) Alkaline pulping processes with chemical pretreatment
US2065395A (en) Fractured wood fiber product
US1890179A (en) Preparing refined bleached pulp
US1859845A (en) Treatment of wood for the production of pulp
US3773611A (en) Two-stage sodium sulfite-oxygen pulping