CA1103413A - Process for the manufacture of mechanical pulp - Google Patents
Process for the manufacture of mechanical pulpInfo
- Publication number
- CA1103413A CA1103413A CA272,600A CA272600A CA1103413A CA 1103413 A CA1103413 A CA 1103413A CA 272600 A CA272600 A CA 272600A CA 1103413 A CA1103413 A CA 1103413A
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- dried
- mechanical
- accordance
- alkaline
- 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
- D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
- D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
- D21B1/14—Disintegrating in mills
- D21B1/16—Disintegrating in mills in the presence of chemical agents
-
- 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
- D21B1/38—Conserving the finely-divided cellulosic material
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
- D21F11/14—Making cellulose wadding, filter or blotting paper
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
- Pressure Sensors (AREA)
- Air Bags (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides a process for the manufacture of mechanical pulp suitable for absorption purposes in which the wood raw material before, during and/or after mechanical defibration is treated with alkaline reacting components and in which the defibrized pulp is dried, optionally after sheet formation, characterized in that the pulp is dried in an alkaline buffered condition,
The present invention provides a process for the manufacture of mechanical pulp suitable for absorption purposes in which the wood raw material before, during and/or after mechanical defibration is treated with alkaline reacting components and in which the defibrized pulp is dried, optionally after sheet formation, characterized in that the pulp is dried in an alkaline buffered condition,
Description
3~g~3 The instant invention-relates to a process for the manufacture of mechanical pulp.
Mechanical pulp is a general term used for pulp types obtained by mechanical defibration of different wood spices.
Itcan be produced by the use of grinding stones or disk re-finers~ optionally subsequent to a mild chemical treatment.
As mechanical pulp is a relatively inexpensive product compared with cellulose pulps obtained by chemical digestion of wood~ such pulp has been widely used as raw material for the manufacture of newsprint, magazine paper etc... However~
mechanical pulp possesses the undesirable property that it undergoes "self sizing" on storage, and as a consequence of said "seIf siæing" mechanical pulp after storage will exhibit hydrophobic properties to a more or lesser degree~
dependent on storage time, rosin content, storage condition etc., which renders the further treatment difficult when the pu1p is to be further p~ocessed.
Due to the "self sizing" mechanical pulp has only to a minor degree been utilized for absorption purposes7 for instance in napkins, sanitory pads, tampons, towels and similar products. For such purposes high quality bleached celluloses have previously been utilized.
It has been shown that if the rosin can be removed from the mechanical pulp such pulp can advantageously be utilized ~or the above mentioned purposes~ such as disclosed in Norwegian Patent No. 124.193. In accordance with said pat~nt the rosin can be removed from the pulp by extraction with acetone~ whereby a~product with good absorption pro-perties is obtained. ~owever, an industrial ext:raction pro-cess is a relatively complicated and expensive process ~3~3 , requiring large capital investment in extraction apparatus, recovering apparatus, etc.. Acetone extraction of mechanical pulp has previously been suggested in order to improve the strength property of mechanical pulp and in order to facilitate the wet defibration in the subsequent process (Brandal & Lindheim, Pulp & Paper Mag. Canada 67 T 431, 1966).
In Belgian Patent 833,343, issued September 30, 1915, there is dlsclosed a process for treatment of a mechanical pulp in order that the hydrophilic properties of the pulp be maintained after ageing. A mechanical pulp treated in accordance with Norwegian patent application No. 74.3286 will during storage remain hydrophilic and can thus easily be defibrized during the subsequent processing. It has further been shown that such pulp is eminently suitable for absorption purposes, in spite of the fact that the new treatment effects the rosln content of the mechanical pulp to a minor degree.
In accordance with Belgian Patent 833,343, the mechanical pulp is treated or impregnated with a buffer buffering in the pH
range 6 - 10, preferably in the range 7 - 9. Suitable buffers are alkali metal salts and ammonium salts of for instance phosphoric acid, carbonic acid, citric acid, tartarie acid ete..
The buffer, preferably in the form of an aqueous solution is added to the mechanical pulp in such amount that the pulp will contain at least, 0,2~ by weight of the buffer, based on the dry weight of the pulpj preferably 0,5% by weight or more.
Such treatment of the mechanical pulp with an aqueous solution of the buffer ean be effected at a low price and ~3~:~3 in a simple manner. The addition can be effected at different stages under the production of the mechanical pulp, depen-ding on the field of use of the product and accessible equipment. The addition can for instance take place during the manufacturing step in the refiner or grinder~ in the white water system in the paper machine, in the size press, by spraying during or after the sheet formation~ injection in the pulp before bale formation. The treatment can thus be effected with accessible equipment and thus utillzed in existing processing plants. By means of thé new pro-cess absorbing materials can for instance be manufactured from mechanical pulps~ which means a substantial saving with respect to hlghly refined cellulose products. From a resource and environment point of view the new process represents obviousl~ advantageous features.
It has surprisingly been found that it is possible to manufacture a mechaniaal pulp maintaining the hydrophi-lic properties without effecting the subsequent buffer treatment of the pulp, such as described in ~
~ In accordance with the new pro-cess the desired bufer system is prepared in situ in the~
pulp. By adjusting an optional after-treatment of the pulp the buffer system can be maintained in such way that the pulp during storage does not undergo "self sizing"
and thus maintains the hydrophilic properties.
As previously mentioned mechanical pulps prepared in diferent manners can further be subjected to a light pre or post chemical treatmentr Such treatment can comprise a pretreatment of the chips with suIphite solutions~ in-jection of sulphite and bleaching chemicals in the refi-ner, or the pulp can subsequent to defibrizing be submit-ted to conventional bleaching in a bleaching tower. Se-veral of the treatments are effected at a pH in the range 7 - 11 and as -the process temperature can reach 50 - 150 C
organic acids derived from the lignin and carbohydrate content of the wood will be formed.
These acids together with sodium hydroxide from the sulphite treatment or peroxide bleaching (dithionite bleaching) can form buffer systems buffering in the range pH 7 - 10). These buffer systems are thus obtained as by-products in the pulp as a consequence of the above ~en-tioned mild chemical treatments.
All mechanical pulp types which today are submitted to such mild chemical treatment are posttreated by means of washing with water and a subse~uent,pH adjustment to pH 5~0 - 5,5 by means of sulphuric acid or sulphur diox,lde.
The subse~uent pH adjustment 'of the mechanical pulp to a pH of 5~0 - 5~5 will shift the pH range of the pulp from the de,sired range of 6 - 10~ hence after the pH adjust_ ment the pulp will no longer maintain the hydrophilic pro-perties after storage.
Conventional peroxide bleaching of mechanical pulp is today carried out by treating the pulp for 2 - 3 hours at 50 - 70C with a mixture of WaOH, H202 and sodium si-licate at a pulp consistency in the range 10 - 20%. Du-ring the initial stage of the bleaching process the pH
is in the range 10 - 11 and after the bleaching the pH
is in the range 8 - 9.
According to the conventional process the bleached pulp i's diluted with water and the pH adjusted to approxi-mately 5 by means of sulphuric acid or sulphur dioxide and then dewatered and washed with water.
The conventional process will still be relevant if the pulp is to be utilized for non-absorbing purposes.
However~ if the pulp shall be used for absorbing purposes, for instance fluffed products~ tissue products and the like~ the optional pH adjustment must be effected in such manner that the p~l is not reduced to 5,0 - 5,5 in accor-dance with the conventional process.
The buffer systems formed in the pulp as a conse-quence of the rnild chemical treatment by optionally omit-ting the subsequent washing treatment or the washing treat-ment can be effected~wlth water optionally made weakly alkaline~ or lf it is deslred to lower the pH to a pre-ferred range the washing can be effected by utilizing suitable weak acids in order that the pH of the washed pulp will be in the range 7,0 - 8,5. By utilizing for instance phosphoric acld~ carbonic acid~ cltric acid or tartaric acid the amount of the buffer system in the pulp can be increased if desired.
~ooS~'~ q - By cho~ng`~he proper after-treatment of a mechani-cal pulp which has been submitted to a mild chemical treat-ment it can, as described above~ be obtained a mechanical pulp containing a suitable amount of buffer buffering in the desired pH range of 6 - 10, preferably in the range 7 - 9 whereby the obtained pulp will remain hydrophilic and not undergo "self sizing'~ during storage.
The desired effect can also be attained in conven-tional grinding in a grindér if the pH of the shower is kept at the alkaline range. This can for lnstance be ~3~3 effected by utilizing the washing water from the peroxide bleaching as shower.
The mechanical pulp containing the buffer system formed in situ can be dried dirçctly in a conventional manner or it can be transformed to the desired product such as a tissue product by utilizing a sheet forming machine having an alkaline reacting white water system.
The invention shaIl be illustrated by means of the following non-limiting examples. Different mechani-cal pulps were prepared and examined with respéct to the water absorbing properties. The prepared pulps were dried in a cyclone and fluffed (in a Wenneberg-mill).
The fluffed pulp was then artificially aged at 150C in 1 hour~ whereafter the pulps were allowed to remain at room temperature for 30 - 60 min. before the water absorp-tion of the aged pulps were deterrnined. The water absorp-tion for non-aged pulp and pulp not prepared in ac~ordance with the invention was also determined.
The determination of the water absorption rate in t~ese tests were carried out by evenly distributing 10 g air dried, fluffed pulp in a small basket of metal gauze (dimensions 7 cm x 20 cm x 1 cm) which was placed in a container containing 200 ml water. The time taken from the moment the basket was placed in the container and un-til the pulp was completely moistened by the water is a measure of the water absorption rate of the pulp.
Eksempel 1 A refiner pulp was prepared by soaking 25 kg spruce chips overnight in 220 1 of an aqueous solution containing 10% by weight Na2S03 (pH 8~6) Eor 12 hours at 20C. The thus impregna~ed chips were refined in a disk refiner with a power consumption of 800 kWh/ton. A part of the thus obtained pulp (in the following designated with la) was dried'and the absorption rate determined before and after ageing.
A part of the pulp was thoroughly washed with water (pulp lb) and subsequently dried and the water absorption rate determined.
A further part of the pulp was washed with'S02 con-t,aining water (pulp lc) in such way that the pH of the pulp was lowered to 5,5, whereafter the pulp was dried and the water absorption rate determined.
The results will be'apparent from the subsequent table.
Example 2: Bleached pulp~
Spruce groundwood was bleached to a bright'ness of 73% by means of 2% H202, 1,2% NaOH and 5% sodium sili'cate 7 pH after bleaching was 8,5, however, after a mild washing with water the pH of the pulp was 7~5. The wate~ absorp-tion rate of the thus'obtained pulp (2a) was determined as described above and the results are shown in the sub-sequent table.
A part of the thus obtained bleached pulp was aci-dified in,a conventional manner by means of S02-water to ' ', a pH of 5~5 and the water absorption rate of the pulp (2b) was determined as previously described and the re-sults are shown in the subsequent table.
~533~L3 Water absorption rate~
seconds/lO q:pulp ~ : After 1 hour Example Pulp type: Before ageing ~at 105 C :
~ : .
Refiner p~lp :rom spruce la Dried directly at pH 8~6 2 ~ 2~5 lb Dried after a mild washing with water 9 52 lc Drled at~pH 515~ 20 ~ 130 -- . :
:: . Peroxide:bleached ground- ~ , : wood~ spruce :~
: : 2a Dried at~pH 7~5 ~ ~ S ~5 2b Dried at pH 5,5 11 40 ~:
.
:
' ~ ' .
, ' 4~3 It can be mentioned that the absorption rate for a - refiner pulp of spruce before and after ayeing is 8 - 14 seconds and 90 - 600 seconds~ respectively.
From the above results it can clearly be seen that 5mechanical pulp prepared in accordance with the instant invention results in a pulp havlny a high absorption rate?
even ater artificial ageing at 105C for l hour.
.
10 , . ..
' .
".
Mechanical pulp is a general term used for pulp types obtained by mechanical defibration of different wood spices.
Itcan be produced by the use of grinding stones or disk re-finers~ optionally subsequent to a mild chemical treatment.
As mechanical pulp is a relatively inexpensive product compared with cellulose pulps obtained by chemical digestion of wood~ such pulp has been widely used as raw material for the manufacture of newsprint, magazine paper etc... However~
mechanical pulp possesses the undesirable property that it undergoes "self sizing" on storage, and as a consequence of said "seIf siæing" mechanical pulp after storage will exhibit hydrophobic properties to a more or lesser degree~
dependent on storage time, rosin content, storage condition etc., which renders the further treatment difficult when the pu1p is to be further p~ocessed.
Due to the "self sizing" mechanical pulp has only to a minor degree been utilized for absorption purposes7 for instance in napkins, sanitory pads, tampons, towels and similar products. For such purposes high quality bleached celluloses have previously been utilized.
It has been shown that if the rosin can be removed from the mechanical pulp such pulp can advantageously be utilized ~or the above mentioned purposes~ such as disclosed in Norwegian Patent No. 124.193. In accordance with said pat~nt the rosin can be removed from the pulp by extraction with acetone~ whereby a~product with good absorption pro-perties is obtained. ~owever, an industrial ext:raction pro-cess is a relatively complicated and expensive process ~3~3 , requiring large capital investment in extraction apparatus, recovering apparatus, etc.. Acetone extraction of mechanical pulp has previously been suggested in order to improve the strength property of mechanical pulp and in order to facilitate the wet defibration in the subsequent process (Brandal & Lindheim, Pulp & Paper Mag. Canada 67 T 431, 1966).
In Belgian Patent 833,343, issued September 30, 1915, there is dlsclosed a process for treatment of a mechanical pulp in order that the hydrophilic properties of the pulp be maintained after ageing. A mechanical pulp treated in accordance with Norwegian patent application No. 74.3286 will during storage remain hydrophilic and can thus easily be defibrized during the subsequent processing. It has further been shown that such pulp is eminently suitable for absorption purposes, in spite of the fact that the new treatment effects the rosln content of the mechanical pulp to a minor degree.
In accordance with Belgian Patent 833,343, the mechanical pulp is treated or impregnated with a buffer buffering in the pH
range 6 - 10, preferably in the range 7 - 9. Suitable buffers are alkali metal salts and ammonium salts of for instance phosphoric acid, carbonic acid, citric acid, tartarie acid ete..
The buffer, preferably in the form of an aqueous solution is added to the mechanical pulp in such amount that the pulp will contain at least, 0,2~ by weight of the buffer, based on the dry weight of the pulpj preferably 0,5% by weight or more.
Such treatment of the mechanical pulp with an aqueous solution of the buffer ean be effected at a low price and ~3~:~3 in a simple manner. The addition can be effected at different stages under the production of the mechanical pulp, depen-ding on the field of use of the product and accessible equipment. The addition can for instance take place during the manufacturing step in the refiner or grinder~ in the white water system in the paper machine, in the size press, by spraying during or after the sheet formation~ injection in the pulp before bale formation. The treatment can thus be effected with accessible equipment and thus utillzed in existing processing plants. By means of thé new pro-cess absorbing materials can for instance be manufactured from mechanical pulps~ which means a substantial saving with respect to hlghly refined cellulose products. From a resource and environment point of view the new process represents obviousl~ advantageous features.
It has surprisingly been found that it is possible to manufacture a mechaniaal pulp maintaining the hydrophi-lic properties without effecting the subsequent buffer treatment of the pulp, such as described in ~
~ In accordance with the new pro-cess the desired bufer system is prepared in situ in the~
pulp. By adjusting an optional after-treatment of the pulp the buffer system can be maintained in such way that the pulp during storage does not undergo "self sizing"
and thus maintains the hydrophilic properties.
As previously mentioned mechanical pulps prepared in diferent manners can further be subjected to a light pre or post chemical treatmentr Such treatment can comprise a pretreatment of the chips with suIphite solutions~ in-jection of sulphite and bleaching chemicals in the refi-ner, or the pulp can subsequent to defibrizing be submit-ted to conventional bleaching in a bleaching tower. Se-veral of the treatments are effected at a pH in the range 7 - 11 and as -the process temperature can reach 50 - 150 C
organic acids derived from the lignin and carbohydrate content of the wood will be formed.
These acids together with sodium hydroxide from the sulphite treatment or peroxide bleaching (dithionite bleaching) can form buffer systems buffering in the range pH 7 - 10). These buffer systems are thus obtained as by-products in the pulp as a consequence of the above ~en-tioned mild chemical treatments.
All mechanical pulp types which today are submitted to such mild chemical treatment are posttreated by means of washing with water and a subse~uent,pH adjustment to pH 5~0 - 5,5 by means of sulphuric acid or sulphur diox,lde.
The subse~uent pH adjustment 'of the mechanical pulp to a pH of 5~0 - 5~5 will shift the pH range of the pulp from the de,sired range of 6 - 10~ hence after the pH adjust_ ment the pulp will no longer maintain the hydrophilic pro-perties after storage.
Conventional peroxide bleaching of mechanical pulp is today carried out by treating the pulp for 2 - 3 hours at 50 - 70C with a mixture of WaOH, H202 and sodium si-licate at a pulp consistency in the range 10 - 20%. Du-ring the initial stage of the bleaching process the pH
is in the range 10 - 11 and after the bleaching the pH
is in the range 8 - 9.
According to the conventional process the bleached pulp i's diluted with water and the pH adjusted to approxi-mately 5 by means of sulphuric acid or sulphur dioxide and then dewatered and washed with water.
The conventional process will still be relevant if the pulp is to be utilized for non-absorbing purposes.
However~ if the pulp shall be used for absorbing purposes, for instance fluffed products~ tissue products and the like~ the optional pH adjustment must be effected in such manner that the p~l is not reduced to 5,0 - 5,5 in accor-dance with the conventional process.
The buffer systems formed in the pulp as a conse-quence of the rnild chemical treatment by optionally omit-ting the subsequent washing treatment or the washing treat-ment can be effected~wlth water optionally made weakly alkaline~ or lf it is deslred to lower the pH to a pre-ferred range the washing can be effected by utilizing suitable weak acids in order that the pH of the washed pulp will be in the range 7,0 - 8,5. By utilizing for instance phosphoric acld~ carbonic acid~ cltric acid or tartaric acid the amount of the buffer system in the pulp can be increased if desired.
~ooS~'~ q - By cho~ng`~he proper after-treatment of a mechani-cal pulp which has been submitted to a mild chemical treat-ment it can, as described above~ be obtained a mechanical pulp containing a suitable amount of buffer buffering in the desired pH range of 6 - 10, preferably in the range 7 - 9 whereby the obtained pulp will remain hydrophilic and not undergo "self sizing'~ during storage.
The desired effect can also be attained in conven-tional grinding in a grindér if the pH of the shower is kept at the alkaline range. This can for lnstance be ~3~3 effected by utilizing the washing water from the peroxide bleaching as shower.
The mechanical pulp containing the buffer system formed in situ can be dried dirçctly in a conventional manner or it can be transformed to the desired product such as a tissue product by utilizing a sheet forming machine having an alkaline reacting white water system.
The invention shaIl be illustrated by means of the following non-limiting examples. Different mechani-cal pulps were prepared and examined with respéct to the water absorbing properties. The prepared pulps were dried in a cyclone and fluffed (in a Wenneberg-mill).
The fluffed pulp was then artificially aged at 150C in 1 hour~ whereafter the pulps were allowed to remain at room temperature for 30 - 60 min. before the water absorp-tion of the aged pulps were deterrnined. The water absorp-tion for non-aged pulp and pulp not prepared in ac~ordance with the invention was also determined.
The determination of the water absorption rate in t~ese tests were carried out by evenly distributing 10 g air dried, fluffed pulp in a small basket of metal gauze (dimensions 7 cm x 20 cm x 1 cm) which was placed in a container containing 200 ml water. The time taken from the moment the basket was placed in the container and un-til the pulp was completely moistened by the water is a measure of the water absorption rate of the pulp.
Eksempel 1 A refiner pulp was prepared by soaking 25 kg spruce chips overnight in 220 1 of an aqueous solution containing 10% by weight Na2S03 (pH 8~6) Eor 12 hours at 20C. The thus impregna~ed chips were refined in a disk refiner with a power consumption of 800 kWh/ton. A part of the thus obtained pulp (in the following designated with la) was dried'and the absorption rate determined before and after ageing.
A part of the pulp was thoroughly washed with water (pulp lb) and subsequently dried and the water absorption rate determined.
A further part of the pulp was washed with'S02 con-t,aining water (pulp lc) in such way that the pH of the pulp was lowered to 5,5, whereafter the pulp was dried and the water absorption rate determined.
The results will be'apparent from the subsequent table.
Example 2: Bleached pulp~
Spruce groundwood was bleached to a bright'ness of 73% by means of 2% H202, 1,2% NaOH and 5% sodium sili'cate 7 pH after bleaching was 8,5, however, after a mild washing with water the pH of the pulp was 7~5. The wate~ absorp-tion rate of the thus'obtained pulp (2a) was determined as described above and the results are shown in the sub-sequent table.
A part of the thus obtained bleached pulp was aci-dified in,a conventional manner by means of S02-water to ' ', a pH of 5~5 and the water absorption rate of the pulp (2b) was determined as previously described and the re-sults are shown in the subsequent table.
~533~L3 Water absorption rate~
seconds/lO q:pulp ~ : After 1 hour Example Pulp type: Before ageing ~at 105 C :
~ : .
Refiner p~lp :rom spruce la Dried directly at pH 8~6 2 ~ 2~5 lb Dried after a mild washing with water 9 52 lc Drled at~pH 515~ 20 ~ 130 -- . :
:: . Peroxide:bleached ground- ~ , : wood~ spruce :~
: : 2a Dried at~pH 7~5 ~ ~ S ~5 2b Dried at pH 5,5 11 40 ~:
.
:
' ~ ' .
, ' 4~3 It can be mentioned that the absorption rate for a - refiner pulp of spruce before and after ayeing is 8 - 14 seconds and 90 - 600 seconds~ respectively.
From the above results it can clearly be seen that 5mechanical pulp prepared in accordance with the instant invention results in a pulp havlny a high absorption rate?
even ater artificial ageing at 105C for l hour.
.
10 , . ..
' .
".
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the manufacture of mechanical pulp suitable for absorption purposes in which the wood raw material before, during and/or after mechanical defibration is treated with alkaline reacting components at a temperature in the range 50-150°C and in which the defribrized pulp is dried, characterized in that the pulp is dried in an alkaline buffered condition at pH 7-10.
2. A process in accordance with claim 1, characterized in that the pH of the alkaline pulp is adjusted to pH 7-9 before drying.
3. A process in accordance with claim 2, characterized in that the pH of the pulp is adjusted by the addition of phosphoric acid, carbonic acid, citric acid or tartaric acid, or mixtures thereof.
4. A process in accordance with claim 1, characterized in that the pulp is bleached under alkaline conditions at a temperature in the range of 50-150°C, whereafter the pulp is dried.
5. A process in accordance with claim 4, in which the pulp is dried after a pH adjustment to 7-9.
6. A process in accordance with claim 1, 2 or 3, in which the pulp is dried after sheet formation.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NO76.0666 | 1976-02-27 | ||
| NO760666A NO760666L (en) | 1976-02-27 | 1976-02-27 | PROCEDURE FOR MAKING MECHANICAL MASSES. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1103413A true CA1103413A (en) | 1981-06-23 |
Family
ID=19882745
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA272,600A Expired CA1103413A (en) | 1976-02-27 | 1977-02-24 | Process for the manufacture of mechanical pulp |
Country Status (14)
| Country | Link |
|---|---|
| JP (1) | JPS52124901A (en) |
| AT (1) | AT358917B (en) |
| AU (1) | AU510167B2 (en) |
| BE (1) | BE851814A (en) |
| CA (1) | CA1103413A (en) |
| DE (1) | DE2707273C2 (en) |
| DK (1) | DK86477A (en) |
| FI (1) | FI70442B (en) |
| FR (1) | FR2342366A1 (en) |
| GB (1) | GB1572519A (en) |
| IT (1) | IT1072075B (en) |
| NL (1) | NL7702142A (en) |
| NO (1) | NO760666L (en) |
| SE (1) | SE439938B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4976819A (en) * | 1988-04-28 | 1990-12-11 | Potlatch Corporation | Pulp treatment methods |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE8002027L (en) * | 1980-03-14 | 1981-09-15 | Sunds Defibrator | IN CONNECTION WITH THE MANUFACTURE OF THERMOMECHANICAL MASS IMPROVING ITS ABSORPTION PROPERTIES |
| AU5088885A (en) * | 1985-11-29 | 1987-06-04 | Gippsland Institute of Advanced Education, The | The production of hard compact carbonaceous material through water/acid/alkali treatment |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2454534A (en) * | 1940-08-03 | 1948-11-23 | Wood Conversion Co | Process for defibering lignocellulose while subjected to steam and alkali-metal hydroxide |
| FR1199065A (en) * | 1958-06-10 | 1959-12-11 | Saint Gobain | Further refining of pulp |
| US3186899A (en) * | 1962-09-11 | 1965-06-01 | Minnesota And Outario Paper Co | Groundwood pulp |
| BE792031A (en) * | 1971-12-14 | 1973-03-16 | Mo Och Domsjoe Ab | PROCESS FOR THE PREPARATION OF MECHANICAL PULPS |
| NO136583C (en) * | 1974-09-12 | 1984-06-07 | Papirind Forskningsinst | MECHANICAL TRIMASSES WITH HIGH SPEED OF ABSORPTION, AND PROCEDURE FOR PREPARING THEREOF |
-
1976
- 1976-02-27 NO NO760666A patent/NO760666L/en unknown
-
1977
- 1977-02-17 AT AT108277A patent/AT358917B/en not_active IP Right Cessation
- 1977-02-19 DE DE2707273A patent/DE2707273C2/en not_active Expired
- 1977-02-24 AU AU22615/77A patent/AU510167B2/en not_active Expired
- 1977-02-24 SE SE7702073A patent/SE439938B/en unknown
- 1977-02-24 CA CA272,600A patent/CA1103413A/en not_active Expired
- 1977-02-25 IT IT12482/77A patent/IT1072075B/en active
- 1977-02-25 BE BE175244A patent/BE851814A/en unknown
- 1977-02-25 GB GB8113/77A patent/GB1572519A/en not_active Expired
- 1977-02-25 FI FI770625A patent/FI70442B/en not_active Application Discontinuation
- 1977-02-25 FR FR7705694A patent/FR2342366A1/en active Granted
- 1977-02-25 DK DK86477A patent/DK86477A/en unknown
- 1977-02-28 NL NL7702142A patent/NL7702142A/en not_active Application Discontinuation
- 1977-02-28 JP JP2040077A patent/JPS52124901A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4976819A (en) * | 1988-04-28 | 1990-12-11 | Potlatch Corporation | Pulp treatment methods |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2707273A1 (en) | 1977-09-01 |
| NO760666L (en) | 1977-08-30 |
| NL7702142A (en) | 1977-08-30 |
| AT358917B (en) | 1980-10-10 |
| ATA108277A (en) | 1980-02-15 |
| FI770625A (en) | 1977-08-28 |
| JPS52124901A (en) | 1977-10-20 |
| FR2342366B1 (en) | 1982-03-05 |
| DK86477A (en) | 1977-08-28 |
| FR2342366A1 (en) | 1977-09-23 |
| GB1572519A (en) | 1980-07-30 |
| IT1072075B (en) | 1985-04-10 |
| AU510167B2 (en) | 1980-06-12 |
| SE7702073L (en) | 1977-08-28 |
| AU2261577A (en) | 1978-08-31 |
| SE439938B (en) | 1985-07-08 |
| FI70442B (en) | 1986-03-27 |
| BE851814A (en) | 1977-06-16 |
| DE2707273C2 (en) | 1984-01-26 |
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