CA1105660A - Solvent vapor extraction of wood - Google Patents
Solvent vapor extraction of woodInfo
- Publication number
- CA1105660A CA1105660A CA273,111A CA273111A CA1105660A CA 1105660 A CA1105660 A CA 1105660A CA 273111 A CA273111 A CA 273111A CA 1105660 A CA1105660 A CA 1105660A
- Authority
- CA
- Canada
- Prior art keywords
- wood
- solvent
- vapor
- solvent vapor
- hydrocarbon
- 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
- D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
- D21B1/00—Fibrous raw materials or their mechanical treatment
- D21B1/02—Pretreatment of the raw materials by chemical or physical means
- D21B1/021—Pretreatment of the raw materials by chemical or physical means by chemical means
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C1/00—Pretreatment of the finely-divided materials before digesting
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Paper (AREA)
Abstract
Abstract of the Disclosure Wood containing a relatively high concentra-tion of solvent-extractable organic substances is extracted with the hot vapor of a chlorinated solvent such as perchloroethylene to reduce the proportion of these materials. Pulpwood of high resin content is advantageously treated by the process to minimize the accumulation of pitch during sulfite pulping.
18,255-F
18,255-F
Description
56~i~
This invention rela-tes to a process for reducing the eoncentration of resins and related organic substances in wood. More particularl~, it concerns a solvent vapor extraction of pitch-forming constituents from pulpwood used in making paper.
Resinous and resin-forming substances in pulpwood may eonsti-tute a con~iderable problem in ; the papermaking process because of the formation and ~ -;
accumulation of pitch. This problem is partieularly acute in the case of softwoods, such a~ certain species of pine and fir which eontain relatively high propor-tions of these materials, which in this ease consi.st essentiall~ of fatty and resin aeids, flavanoids, sterols and steryl esters, and di- and -trig1ycerides ; 15 of the acid3 named. Specialized pulping processes have been developed to handle these resinous woods, but it would be desirable to have availakle a praetical means to reduee the amount of resins and resin-orming substances before pulping and thus simplify the proeess~
It is possible to remove these resinous materials from wood by subjeeting the wood ehips to eonventional extraetion with a hot li~uid organic solvent. However, the extractea chips are then satur~-ated with extracting liquid and the removal and .
recovery of the very considerable amount of s~lvent involved becomes a formidable problem.
It has now been found that the defects of the prior art described ahove have been~substantially over-eome by the present invention, whieh is a process for reducing ~he concentration of solvent-extractable organic .
.
18,255-F -l-~566~
substances in softwood pulpwood of high resin content which comprises contacting said wood with the vapor of a halogentated hydrocarbon having a boiling point of lO0-150C., at about said boiling point.
The process is particularly eEfective for treating softwood pulpwood of high resin content before the pulping process, using perchloroethylene as the extracting vapor.
The present invention is essentially an adaptation of the well~known technique for cleaning metal parts in a solvent vapor degreasing apparatus to the reductio~ of the resinous and resin-forming components of wood below the point where these substances caus~ significant problems in wood-modifying processes such as sulfite pulping. Vapor degreasing apparatus consists basically of a refluxing chamber or sump contain-ing liquid solvent, means for boiling the solvent so as to form a solvent vapor zone in the upper portion of the apparatus above the sump, condensing means near the top of the chamber, and means for holding articles to be cleaned in the vapor zone. During the cleaning process, solvent vapor condenses on the articles in ~he vapor zone, dissolving grease or oily residues, and this liquid drips back into the boiling solvent below, thereby effectively cleaning and rinsing the dirty article.
In the present adaptation of that process to the removal of resin and resin-forming substances from wood, the hot solvent vapor similarly forms a solution of these substances and as they are thus gradually removed from the wood along with most of 18 r 255-F ~ 2 .:' - ~ "
~ , ` : ` :
. . .
5~6~
the water present, the wood becomes increasingl~ per-meable to the vapor 50 that the solvent action affects all of the wood and is not merely a surface effect.
The extracted resinous materials accumulate in the solvent sump and so are readily recoverable. The action of the hot solvent vapor on the wood is particu-larly effective in removing water which is very rapidly reduced to a minimal residue during the extraction process.
The solvents preferred for use in the present process are those having boiling points within the preferred temperature range o the processl that is, about 100C-150C. For practical reasons, halogenated hydrocarbons are the solvents of choice, particularly chlorinated hydrocarbons such as 1,1,2-trichlo~oethane, perchloroeth~lene, chlorobenzene, 1,3-dichloropropane, and 1,1,2,2-tetrachloroethane. of these, a chlorinated aliphatic hydrocarbon such as perchloroethylene is particularly preferred. Halogenated hydrocarbons with lower hoiling points such as rnethylene chloride, ethylene dichloride, and l,1,1-trichloroethane are also operable in the process and may give about as good results as the preferred higher boiling compounds when the wood being treated has a lo~ to moderate resin and pitch content.
This process is primarily of utility as a precursor to a pulping operation wherein wood chips in bundles or baskets of me~al mesh are first extracted to reduce their resinous content. The process can also be used to advantage in o-ther wood-modifying or treating procedures where a high resin content is undesirable, for example/ in making particle hoard.
18,255-F ~3~
~S6~
The fastest and most effective method for r~noving resin and resin-forming compounds from wood is, of course, by conventional extraction with hot li~uid solvent. This method is ordinaril~ impractical to use for the puxposa, however, because of the large amount of solvent re~uired and, particularly, the difficulty of avoiding ver~ high losses of solvent because the wood comes from the extraction soaked through with li~uid solvent. In the present process, the treated wood from the process contains essentially only solvent vapor. This much smaller proportion of solvent can be recovered by any OL se~7eral known methods, for example, by flushing with a stream of warm air and adsorption of the solvent vapor ~rom the effluent air by charcoal or by adsorbent polymer beads.
Example Ex erimental Procedure P - - --.
Woods:
Jack pine and black spruce were chosen as two pulpwoods representing high and low levels, respec-tively, of solvent-extractable substances and conse-quently more and less pitch-forming prohlem~ in sulfi'ce pulping. Logs of both were cut and stored for two weeks at about ~C, then reduced to chips at a pulp mill so as to be representative of fxesh mill chips. Some of the chips were seasoned by storage at that temperature for six months.
Moisture Determination:
The wood chips were cuc to an avera~e size of about 6 x 25 ~n and weighed samples were freéze-dried 18,255-F ~4~
5~
or ~8 hours. The weight loss was taken as the moisture content of the wood.
Solvent-Extractable Content:
: Samples of dried wood chips were ground to a fine powder in the presence of solid carbon dio~ide by a blender and 5-g. portions were extxacted for 18 - hours with 200 ml. o~ acetone. The organic material :~:
thereby extracted was considered to be the total extract-able organic content.
Solvent Vapor Extraction:
Six shallow stainless steel ~esh baskets each containing about 25 g. of wood ships were secured within the vapor zone of a conventional solvent vapor metal degreasing apparatus of the type pxeviou~ly described. Single baskets were removed at Ei~teen-minute intervals and the extracted chips were cut into smaller pieces ~or moisture content determination and measurement of residual solvent-extractables as described ; above. Solvent retained in the vapor ext~acted chips was measured as the solvent la~er in the condensed ef1uent from the freeze drying procedure.
The weight percentages of solvent-extractable organics remaining in the wood chips at each stage of , the vapor extraction process are listed in Tables I
and II. The results in Table I are those obtained using perchloroeth~lene as the solvent, Table II which is included for comparison shows the results obtained using l,l,l-trichloroethane.
18,255-F ~5~
Table I
~Perchloroethylene) Wt. % Extractables ~dry basis~
Fresh Seasoned Time, jack jack Fresh Seasoned Minutes pine pine spruce spruce 0 3.9 4.7 1.5 102 3.5 4.0 1.2 1.3 - - 1.2 1.3 3-3 4~0 - 1.1
This invention rela-tes to a process for reducing the eoncentration of resins and related organic substances in wood. More particularl~, it concerns a solvent vapor extraction of pitch-forming constituents from pulpwood used in making paper.
Resinous and resin-forming substances in pulpwood may eonsti-tute a con~iderable problem in ; the papermaking process because of the formation and ~ -;
accumulation of pitch. This problem is partieularly acute in the case of softwoods, such a~ certain species of pine and fir which eontain relatively high propor-tions of these materials, which in this ease consi.st essentiall~ of fatty and resin aeids, flavanoids, sterols and steryl esters, and di- and -trig1ycerides ; 15 of the acid3 named. Specialized pulping processes have been developed to handle these resinous woods, but it would be desirable to have availakle a praetical means to reduee the amount of resins and resin-orming substances before pulping and thus simplify the proeess~
It is possible to remove these resinous materials from wood by subjeeting the wood ehips to eonventional extraetion with a hot li~uid organic solvent. However, the extractea chips are then satur~-ated with extracting liquid and the removal and .
recovery of the very considerable amount of s~lvent involved becomes a formidable problem.
It has now been found that the defects of the prior art described ahove have been~substantially over-eome by the present invention, whieh is a process for reducing ~he concentration of solvent-extractable organic .
.
18,255-F -l-~566~
substances in softwood pulpwood of high resin content which comprises contacting said wood with the vapor of a halogentated hydrocarbon having a boiling point of lO0-150C., at about said boiling point.
The process is particularly eEfective for treating softwood pulpwood of high resin content before the pulping process, using perchloroethylene as the extracting vapor.
The present invention is essentially an adaptation of the well~known technique for cleaning metal parts in a solvent vapor degreasing apparatus to the reductio~ of the resinous and resin-forming components of wood below the point where these substances caus~ significant problems in wood-modifying processes such as sulfite pulping. Vapor degreasing apparatus consists basically of a refluxing chamber or sump contain-ing liquid solvent, means for boiling the solvent so as to form a solvent vapor zone in the upper portion of the apparatus above the sump, condensing means near the top of the chamber, and means for holding articles to be cleaned in the vapor zone. During the cleaning process, solvent vapor condenses on the articles in ~he vapor zone, dissolving grease or oily residues, and this liquid drips back into the boiling solvent below, thereby effectively cleaning and rinsing the dirty article.
In the present adaptation of that process to the removal of resin and resin-forming substances from wood, the hot solvent vapor similarly forms a solution of these substances and as they are thus gradually removed from the wood along with most of 18 r 255-F ~ 2 .:' - ~ "
~ , ` : ` :
. . .
5~6~
the water present, the wood becomes increasingl~ per-meable to the vapor 50 that the solvent action affects all of the wood and is not merely a surface effect.
The extracted resinous materials accumulate in the solvent sump and so are readily recoverable. The action of the hot solvent vapor on the wood is particu-larly effective in removing water which is very rapidly reduced to a minimal residue during the extraction process.
The solvents preferred for use in the present process are those having boiling points within the preferred temperature range o the processl that is, about 100C-150C. For practical reasons, halogenated hydrocarbons are the solvents of choice, particularly chlorinated hydrocarbons such as 1,1,2-trichlo~oethane, perchloroeth~lene, chlorobenzene, 1,3-dichloropropane, and 1,1,2,2-tetrachloroethane. of these, a chlorinated aliphatic hydrocarbon such as perchloroethylene is particularly preferred. Halogenated hydrocarbons with lower hoiling points such as rnethylene chloride, ethylene dichloride, and l,1,1-trichloroethane are also operable in the process and may give about as good results as the preferred higher boiling compounds when the wood being treated has a lo~ to moderate resin and pitch content.
This process is primarily of utility as a precursor to a pulping operation wherein wood chips in bundles or baskets of me~al mesh are first extracted to reduce their resinous content. The process can also be used to advantage in o-ther wood-modifying or treating procedures where a high resin content is undesirable, for example/ in making particle hoard.
18,255-F ~3~
~S6~
The fastest and most effective method for r~noving resin and resin-forming compounds from wood is, of course, by conventional extraction with hot li~uid solvent. This method is ordinaril~ impractical to use for the puxposa, however, because of the large amount of solvent re~uired and, particularly, the difficulty of avoiding ver~ high losses of solvent because the wood comes from the extraction soaked through with li~uid solvent. In the present process, the treated wood from the process contains essentially only solvent vapor. This much smaller proportion of solvent can be recovered by any OL se~7eral known methods, for example, by flushing with a stream of warm air and adsorption of the solvent vapor ~rom the effluent air by charcoal or by adsorbent polymer beads.
Example Ex erimental Procedure P - - --.
Woods:
Jack pine and black spruce were chosen as two pulpwoods representing high and low levels, respec-tively, of solvent-extractable substances and conse-quently more and less pitch-forming prohlem~ in sulfi'ce pulping. Logs of both were cut and stored for two weeks at about ~C, then reduced to chips at a pulp mill so as to be representative of fxesh mill chips. Some of the chips were seasoned by storage at that temperature for six months.
Moisture Determination:
The wood chips were cuc to an avera~e size of about 6 x 25 ~n and weighed samples were freéze-dried 18,255-F ~4~
5~
or ~8 hours. The weight loss was taken as the moisture content of the wood.
Solvent-Extractable Content:
: Samples of dried wood chips were ground to a fine powder in the presence of solid carbon dio~ide by a blender and 5-g. portions were extxacted for 18 - hours with 200 ml. o~ acetone. The organic material :~:
thereby extracted was considered to be the total extract-able organic content.
Solvent Vapor Extraction:
Six shallow stainless steel ~esh baskets each containing about 25 g. of wood ships were secured within the vapor zone of a conventional solvent vapor metal degreasing apparatus of the type pxeviou~ly described. Single baskets were removed at Ei~teen-minute intervals and the extracted chips were cut into smaller pieces ~or moisture content determination and measurement of residual solvent-extractables as described ; above. Solvent retained in the vapor ext~acted chips was measured as the solvent la~er in the condensed ef1uent from the freeze drying procedure.
The weight percentages of solvent-extractable organics remaining in the wood chips at each stage of , the vapor extraction process are listed in Tables I
and II. The results in Table I are those obtained using perchloroeth~lene as the solvent, Table II which is included for comparison shows the results obtained using l,l,l-trichloroethane.
18,255-F ~5~
Table I
~Perchloroethylene) Wt. % Extractables ~dry basis~
Fresh Seasoned Time, jack jack Fresh Seasoned Minutes pine pine spruce spruce 0 3.9 4.7 1.5 102 3.5 4.0 1.2 1.3 - - 1.2 1.3 3-3 4~0 - 1.1
2.8 2.3 1.7 1.8 1 Table II
richloroethane) ~t. ~ Extractables (dry basis) Fresh Seasoned Time, jack jack Fresh Seasoned Minutes pine pine spruce _spruce 0 3.9 4.7 1.5 1.2
richloroethane) ~t. ~ Extractables (dry basis) Fresh Seasoned Time, jack jack Fresh Seasoned Minutes pine pine spruce _spruce 0 3.9 4.7 1.5 1.2
3.8 3.9 1.3 0.9 3.8 3.5 1.2 0.8 3.4 2.7 1.1 0.8 _ _ _ _ 3.1 2~5 1.3 0.8 It is evident that the higher boiling perchloro-ethylene provided suhstantially more effective vapor extrac-tion in the wood of high solvent-extractable content. In the case of the wood with relatively low extractable organic content, comparable results were ohtained with the -two solvents. Similar extraction tests made with meth~lene 18,255 F -6-~561~0 chloride showed somewhat less effective extraction of jack pine wood whereas the results with spruce were comparable to those found with the other two solvents.
18,255-F ~7~
,:, :. .:
18,255-F ~7~
,:, :. .:
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for reducing the concentration of solvent-extractable organic substances in softwood pulp-wood of high resin content which comprises contacting said wood with the vapor of a halogenated hydrocarbon having a boiling point of 100-150°C., at about said boil-point.
2. The process of Claim 1 wherein the halo-genated hydrocarbon is a chlorinated aliphatic hydrocarbon.
3. The process of Claim 2 wherein the chlorinated hydrocarbon is perchlorethylene.
18,255-F -8-
18,255-F -8-
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA273,111A CA1105660A (en) | 1977-03-03 | 1977-03-03 | Solvent vapor extraction of wood |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA273,111A CA1105660A (en) | 1977-03-03 | 1977-03-03 | Solvent vapor extraction of wood |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1105660A true CA1105660A (en) | 1981-07-28 |
Family
ID=4108067
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA273,111A Expired CA1105660A (en) | 1977-03-03 | 1977-03-03 | Solvent vapor extraction of wood |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1105660A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2619837A1 (en) * | 1987-08-25 | 1989-03-03 | Isoroy Sa | Process for preparing an activable cellulose substrate and substrate obtained by this process |
| WO1999004087A1 (en) * | 1997-07-17 | 1999-01-28 | North Pacific Paper Corporation | Pulp, paper and absorbent products of reduced pitch content and process |
| WO1999004086A1 (en) * | 1997-07-17 | 1999-01-28 | North Pacific Paper Corporation | Pretreatment of wood particulates for removal of wood extractives |
| US6075076A (en) * | 1995-12-27 | 2000-06-13 | North American Paper Corporation | Composite wood products prepared from solvent extracted wood particulates |
| US6364999B1 (en) | 1995-12-27 | 2002-04-02 | Weyerhaeuser Company | Process for producing a wood pulp having reduced pitch content and process and reduced VOC-emissions |
-
1977
- 1977-03-03 CA CA273,111A patent/CA1105660A/en not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2619837A1 (en) * | 1987-08-25 | 1989-03-03 | Isoroy Sa | Process for preparing an activable cellulose substrate and substrate obtained by this process |
| US6075076A (en) * | 1995-12-27 | 2000-06-13 | North American Paper Corporation | Composite wood products prepared from solvent extracted wood particulates |
| US6364999B1 (en) | 1995-12-27 | 2002-04-02 | Weyerhaeuser Company | Process for producing a wood pulp having reduced pitch content and process and reduced VOC-emissions |
| US6719880B2 (en) | 1995-12-27 | 2004-04-13 | Weyerhaeuser Company | Process for producing paper and absorbent products of increased strength |
| WO1999004087A1 (en) * | 1997-07-17 | 1999-01-28 | North Pacific Paper Corporation | Pulp, paper and absorbent products of reduced pitch content and process |
| WO1999004086A1 (en) * | 1997-07-17 | 1999-01-28 | North Pacific Paper Corporation | Pretreatment of wood particulates for removal of wood extractives |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |