CA1283258C - High strength, cellulosic-gel-containing kraft paper and process for making the same - Google Patents
High strength, cellulosic-gel-containing kraft paper and process for making the sameInfo
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- CA1283258C CA1283258C CA000541892A CA541892A CA1283258C CA 1283258 C CA1283258 C CA 1283258C CA 000541892 A CA000541892 A CA 000541892A CA 541892 A CA541892 A CA 541892A CA 1283258 C CA1283258 C CA 1283258C
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- kraft
- gel
- cellulosic
- kraft paper
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Abstract
ABSTRACT
High strength, cellulosic-gel-containing kraft paper is made by mechanically refining kraft papermaking pulp to a freeness of CSF 500-800, mixing the resulting refined pulp with from 1 to 10% hydrated cellulosic gel binder, running the resulting fluid mixture into a felted sheet and pressing and drying the sheet to form the kraft paper product.
High strength, cellulosic-gel-containing kraft paper is made by mechanically refining kraft papermaking pulp to a freeness of CSF 500-800, mixing the resulting refined pulp with from 1 to 10% hydrated cellulosic gel binder, running the resulting fluid mixture into a felted sheet and pressing and drying the sheet to form the kraft paper product.
Description
33Z~8 HIGH STRENGTH, CELL~LOSIC-GEL CONTAXNING
~RAFT PAPER AND PROCESS FOR ~KING SAME
BACXGROUND AND GENERAL STATEMENT OF THE INVENTIO~
This invention pertains to high strength, cellulosic-gel-containing kraft paper and to a process for making the same.
In a typical procedure, cellulosic gels are prepared by feeding a chemical papermaking pulp such as a Kraft pulp to a conventional hydrapulper in which it is dis-integrated into a fibrous slurry having a consistency of from l to 10%, preferably from 6 to 8~.
The resulting slurry is fed t~ a battery of several conventional pulp refiners arranged in series. The flow through the sequence of refiners is throttled down by appropriate valving to give a pressurized dwell or residence time su~ficient to exhaustively hydrate the feed material and produce a hyclrated cellulosic gel product.
The use of c:ellulosic gels prepared in this manner as bindexs in the manufacture of wet process composition boards of various categories is illustrated in the following patents:
~ 8 Roberts U.S. 3379608-g Roberts 4173248 Roberts V.S. 4043862 ~eritage Canada 449167 Roberts U.S. 407783~
Roberts U.S. 4087317 However, cellulosic gels heretofore have not been applied successfully as efficien~ binders in the manufacture of ~raft papers since it appeared that the physical properties of the gels would prohibit their successful application to this end use.
Papermaking machines operate at very hi~h speeds, for example, at speeds of as much as 3500 feet per minute. It is necessary that the furnish supplied to them drain quickly through the wire, i.e. in a matter of seco~ds.
Cellulosic gels ar~ thick, viscous, sticky liquids.
It would seem self-evident that to include a significant proportion o~ them in a papermaking furnish, in order to improve the strength of the paper product, would increase the drain time of the furnish to such a level as to make it unsuitable for use on high speed paper machines. Accordingly, heretofore the desired high strength of the paper pxoducts has been developed by refining the pulp to a high degree, and by using long fibered stock which inherently imparts high strength ts the paper. This is undesirable, since prolonged refining requires expensive equipment the use of which is attended by high power costs. Long fibered stocks are comparatively expensive. Substantial economies oould be 83~S8 --3 ~
achieved by reducing the refining time and using short fibered stoc~s, f~r example, short fibered hardwood stocks.
I haYe discovered that, surprisingiy, the inclusi~n of a substantial proportion of cellulosic gel in Rraft papermaking furnishes does s~ot materially increase their drain times on the Fourdrinier wire. Additionally, their inclusion materially increases the strength of the paper and reduces significantly the refining time which must be applied to the freshly cooked pulp.
~ccordingly it is the general object of my invention to provide a process which will result in the production of Kraft papers of improved quality at significantly lower cost.
~ further object of my invention is the provision of a process fox the.production of Xraft papers of improved strength, and having smoother, harder surfaces.
Another object of my invention is the provision of a process for making kraft papers which permits the inclusion of a significant amount of low cost, short fibered pulp such as hardwood pulp without adversely affecting the strength of the paper products.
~enerally stated, my presently described process of making high strength kraft papers-characterized by the above noted advantages comprises first mechanically refining kraft paperma~ing pulp to a freeness value of about CSF 5~0-800.
Next, 2 fluid mixture is made of ~rom about 90 to about 99 of the resultin~ refine~ pulp and from about l to a~out _4~ Z~8 10% of hydrated cellulosic gel binder.
The kra'~t papermaking pulp which is a primary component o~ ~he mixture comprises from about 40 to about 100~ ~y ~
weight of freshly prepared or "virgin~ kraft pulp and from S 0 to 60~ by weight of pulp prepared from reclaimed or "secondary" lignocellulosic fibers, which may include a substantial proportion of short fibers.
The mixture is run into a felted sheet which is pressed and dried to form tbe final kraft papex product.
DESCRIPTION OF PREE'ERRED EIIBODIMENTS
OE' THE INVENTION
As noted above, the new kraft paper of my invention broadly comprises kraft papermaking pulp and cellulosic gel.
These two materials are employed in the following general and preferred proportions, given in percent by weight, dry sollds basis:
General Preferred Kraft papermakinq pulp 90-99 94-98 ~ Cellulosic gel 1-10 2-6 The kraft papermaking pulp may be derived from the usual.sources and is prepared by the.sulfate pulping of the woods of various species of trees Dr other lignocellulosic material.
~ 58 After the pulp has been r2moved from ths digester, it is washed and screened and then subjec~ed to ~ re~tively brief treatment in a con~entional refiner, i.e. a double d~sc refiner such as a Sprout-Waldron or Beloit Jones re-finer. The refining need be carri~d ou~ only to a limiteddegree, i.e. until ~he Canadian Standard Freeness has reachea a value of from about 500 to about 820J preferably from about 600 to about 750, with consequent saYing of energy.
The kraft papermaking pulp component may comprise 1~ 100% virgin pulpt prepared as outlined above, or, it may include a proportion, i.e. from 0 to 60% of its weigbt, dry solids basis, of pulps other than virgin kraft pulp.
These secondary fibers may include fibers derived ~rom cl.eaned papermaking sludge, short fibers derived from the "save all" of the paper mill, from waste paper, from waste cartons and bags, and even from sawdust. The weakening e~fect of these relatively short, lower qiality fibers is overcome by the reinforcing action of the added cellulosic gel.
Where the secondary fibers are derived from waste paper or waste cartons, they are converted to a pulp of papermaking consistency by processing them in a hydrapulper followed by suitable refining i~ a conventional deflaker or refiner to break up ~iber clumps and bundles. This refined stock then is combined with ~he virgin pulp stock.
~ he gel component of the.papermaking mixture comprises the exhaustively hydrated cellulosic gel described, for -6~ 83~
example, in my U.S. patents 4043862, 40~7833, and 4173248.
In its manufacture, che~ical cellulose pulp such as kraft cellulose pulp is refined and hydrated exhaustively to a,high degree at which fiber structure is almost completely destroyed. SpeciXically, this is accomplished by breaking down cellulose pulp sheets to their component individual fibers and fiber clumps, preferably by adding the dry sheets and water to a conventional hydrapulper and hydrapulping at a stocX consistency of from 1 to 10%, preferably from 6 to 8%. This requires about 30 minutes.
The resulting pulp then is fed in controlled flow to a selec~ed disc-type or conical-type primary refiner. There preferably are three such refiners arranged in series with a flow-restricting valve downstream from the last refiner to insure an adequate pressurized refiner dwell time. These abrade the pulp and hydrate it to a high degree, thereby forcing water through the cellulosic structure.
The resulting par~ially refined and hydrated pulp is then fed to a secondary refiner of the same general class as the primary refiners~ but which is effective to complete the hydration~ The pulp is reduced in size to values impart-ing to it TAPPI standard drain times of at least 350 seconds, preferably above 900 seconds. This is accomplished by a shearing action which almost completely destroys the fi~er-structure o~ the pulp and hydrates i~ exhaustively. Thissupple~ental and exhaustive refining greatly improves the gualities of the pulp as a ~ind2r, dispe~sing agen~ and re ~Z~3z~8 _ , tention agent when used in the manufacture of the herein described high strength paper.
In particular, it makes of the gel an ~ixreversible~
binder. As a result, paper made with it is highly water resistant.
A method other than the TAPPI drain time test for characterizing a gel suitable for the present purpose is to determine the shrinkage upon drying of the handsheet produced by the TAPPI drain time test. A suitably hydrated gel will form a hand sheet which shri~ks upon drying to a diameter which is at least 25~ smal~er than its original diameter.
In another method, the hand sheet is dried and a small fl'ame applied to its underside. If the cellulose is suffi-lS ciently hydrated, this instantaneously will produce a blisteri~ the sheet.
In still a further test procedure, 250 milleliters of the gel slurry is dried into a solld ball. If the gel is sufficiently hydrated, the ball will sink when dropped into water and thereafter will remain hard without swelling for an indefinite period of submergence.
In addition to the cellulosic gel prepared as described abov~, varîous additives may also be included in the paper-making ~urnish as desirable or necessary. These may include small proportions of dyes, rot-proofing agents, wet strength agents, wax, and the lik~.
~2~33Z~8 The pulp may be bleached if desired, in which case it usually is preferred to use a bleached gel as well.
To prepare the furnish, all the foregoing materials.
a~e added to a suitable mixer such as a Waring blender and mixed to uniformity. The resulting mixture then is added to the headbox of the paper machine, and run into a felted sheet, which is pressed and dried to ~orm the final paper product.
E~PLES
The process of my inve~tion is illustrated in the following examples wherein the amounts of the constituents are given in percent by weight, dry weight basis.
A conventional kraft bag-making stock refined to a freeness of CSF S50 was mixed with about 24~ by weight of pulp having a freeness of about CS~ 550 and containing secondary fibers derived from hydxapulping principally corrugate~ kraft ~oxes and passing the resulting pulp through a deflaker for preliminary refining in order to break down fiber bundles and clumps. The resulting pulp mixture had a consistency of about 0.3~. It was mixed with exhaustively hydrated cellulosic gel prepared as outlined above and having a TAPPI drain time of 550 seconds and a shrinkage of 27~ when subjected to the handsheet drying test.
~he pulp and gel were formulated into 6 test mixtures.
containing respectively 0, 2, 4, 6, 8 and 10~ gel.
~ ~3~ ~8 The mixtures were run into standard test hand sheets having a weight of 200 grams per square meter. These then were ;tested by the Standard TAæPI Test for measuring stiff-ness, CSF freeness, burst, tear and tensile. The results are given in conventional TAPPI test units in the table below.
% GEL STIF~NESS FREENESS BURST TEl~RTENSII;E
0 55 720 16~ 320 17,1 2 50 700 172 342 17,6 4 80 69D 198 ~76 19,3 6 75 670 190 392 .25,1 8 75 670 187 408 22,7 63~ 161 32~ 19.8 Inspecti~n of the above test data illustrates clearly tha~ inclusion of as much as 8% gel reduces the CS~ freeness but a small amount, i.e. from 720 to 670. This is not a sufficient reduction to materially increase the drain time of the furnish on the wire.
The results inclicate further a significant increase in strength, for example, an increase in tensile strength of from 17.1 to 22.7.
If.the gel binder were to be omitted, refining of the original virgin stock to a freeness of CSF 400 to 45~ w~uld be reguired to attain equivalent sheet strength, with at~endant high ref ining costs.
,. :
3LZ~3~2~3 Other benefits accrue from the use of cellulosic gel in the manufacture of kraft paper.
Its use permits the addition of lower cost fibers t~ the paper sheet without significant reduction o~ strength properties.
The qel can be made from a variety of fiber raw materials as well as from conventional kraft and sulfite pulp.
~ t 6% gel usage, with con~entional pressing, it ma~es a thicker sheet at the same welght as the regular pulp.
~ccordingly a lighter wei~ht sheet having acceptable physical properties can be made at present thicknesses.
The gel usage gives a paper sheet with a harder, smoother surface.
The reinfDroing effect of the gel shows on papers made from hardwoods, so~t woods, recycled paper and thermo mechanical pulp.
Use of gel in corrugating medium gives a substa~tial increase in compres~ion resistance. This pexsists under conditions of very high humidity.
Gel is an excellent fiber retention aid. It holds onto most of the very fine fibers which normally are lost to the formi~g wire of the paperma~ing machineO
If the papçr machine is improved so it will ru~ faster, as by installing an ~extended nip~ or ot~er thermal or mechanical impro~ements, the use of gel will permit the additional pulp ~eeded to come from the lower cost secondary fiber sources listed above.
L;283~8 In sum, the use of cellulosic gel in kraft paper improves all impo~tant sheet physical properti~ and ~nakes possible the production of higher quality paper ~t lower Gost.
S Having thus described my inventiorl in spscific embodi-ments, I claim as new and desire to protect by Letters Pa~ent:
,~
- . - ,, ' - ~ .
~RAFT PAPER AND PROCESS FOR ~KING SAME
BACXGROUND AND GENERAL STATEMENT OF THE INVENTIO~
This invention pertains to high strength, cellulosic-gel-containing kraft paper and to a process for making the same.
In a typical procedure, cellulosic gels are prepared by feeding a chemical papermaking pulp such as a Kraft pulp to a conventional hydrapulper in which it is dis-integrated into a fibrous slurry having a consistency of from l to 10%, preferably from 6 to 8~.
The resulting slurry is fed t~ a battery of several conventional pulp refiners arranged in series. The flow through the sequence of refiners is throttled down by appropriate valving to give a pressurized dwell or residence time su~ficient to exhaustively hydrate the feed material and produce a hyclrated cellulosic gel product.
The use of c:ellulosic gels prepared in this manner as bindexs in the manufacture of wet process composition boards of various categories is illustrated in the following patents:
~ 8 Roberts U.S. 3379608-g Roberts 4173248 Roberts V.S. 4043862 ~eritage Canada 449167 Roberts U.S. 407783~
Roberts U.S. 4087317 However, cellulosic gels heretofore have not been applied successfully as efficien~ binders in the manufacture of ~raft papers since it appeared that the physical properties of the gels would prohibit their successful application to this end use.
Papermaking machines operate at very hi~h speeds, for example, at speeds of as much as 3500 feet per minute. It is necessary that the furnish supplied to them drain quickly through the wire, i.e. in a matter of seco~ds.
Cellulosic gels ar~ thick, viscous, sticky liquids.
It would seem self-evident that to include a significant proportion o~ them in a papermaking furnish, in order to improve the strength of the paper product, would increase the drain time of the furnish to such a level as to make it unsuitable for use on high speed paper machines. Accordingly, heretofore the desired high strength of the paper pxoducts has been developed by refining the pulp to a high degree, and by using long fibered stock which inherently imparts high strength ts the paper. This is undesirable, since prolonged refining requires expensive equipment the use of which is attended by high power costs. Long fibered stocks are comparatively expensive. Substantial economies oould be 83~S8 --3 ~
achieved by reducing the refining time and using short fibered stoc~s, f~r example, short fibered hardwood stocks.
I haYe discovered that, surprisingiy, the inclusi~n of a substantial proportion of cellulosic gel in Rraft papermaking furnishes does s~ot materially increase their drain times on the Fourdrinier wire. Additionally, their inclusion materially increases the strength of the paper and reduces significantly the refining time which must be applied to the freshly cooked pulp.
~ccordingly it is the general object of my invention to provide a process which will result in the production of Kraft papers of improved quality at significantly lower cost.
~ further object of my invention is the provision of a process fox the.production of Xraft papers of improved strength, and having smoother, harder surfaces.
Another object of my invention is the provision of a process for making kraft papers which permits the inclusion of a significant amount of low cost, short fibered pulp such as hardwood pulp without adversely affecting the strength of the paper products.
~enerally stated, my presently described process of making high strength kraft papers-characterized by the above noted advantages comprises first mechanically refining kraft paperma~ing pulp to a freeness value of about CSF 5~0-800.
Next, 2 fluid mixture is made of ~rom about 90 to about 99 of the resultin~ refine~ pulp and from about l to a~out _4~ Z~8 10% of hydrated cellulosic gel binder.
The kra'~t papermaking pulp which is a primary component o~ ~he mixture comprises from about 40 to about 100~ ~y ~
weight of freshly prepared or "virgin~ kraft pulp and from S 0 to 60~ by weight of pulp prepared from reclaimed or "secondary" lignocellulosic fibers, which may include a substantial proportion of short fibers.
The mixture is run into a felted sheet which is pressed and dried to form tbe final kraft papex product.
DESCRIPTION OF PREE'ERRED EIIBODIMENTS
OE' THE INVENTION
As noted above, the new kraft paper of my invention broadly comprises kraft papermaking pulp and cellulosic gel.
These two materials are employed in the following general and preferred proportions, given in percent by weight, dry sollds basis:
General Preferred Kraft papermakinq pulp 90-99 94-98 ~ Cellulosic gel 1-10 2-6 The kraft papermaking pulp may be derived from the usual.sources and is prepared by the.sulfate pulping of the woods of various species of trees Dr other lignocellulosic material.
~ 58 After the pulp has been r2moved from ths digester, it is washed and screened and then subjec~ed to ~ re~tively brief treatment in a con~entional refiner, i.e. a double d~sc refiner such as a Sprout-Waldron or Beloit Jones re-finer. The refining need be carri~d ou~ only to a limiteddegree, i.e. until ~he Canadian Standard Freeness has reachea a value of from about 500 to about 820J preferably from about 600 to about 750, with consequent saYing of energy.
The kraft papermaking pulp component may comprise 1~ 100% virgin pulpt prepared as outlined above, or, it may include a proportion, i.e. from 0 to 60% of its weigbt, dry solids basis, of pulps other than virgin kraft pulp.
These secondary fibers may include fibers derived ~rom cl.eaned papermaking sludge, short fibers derived from the "save all" of the paper mill, from waste paper, from waste cartons and bags, and even from sawdust. The weakening e~fect of these relatively short, lower qiality fibers is overcome by the reinforcing action of the added cellulosic gel.
Where the secondary fibers are derived from waste paper or waste cartons, they are converted to a pulp of papermaking consistency by processing them in a hydrapulper followed by suitable refining i~ a conventional deflaker or refiner to break up ~iber clumps and bundles. This refined stock then is combined with ~he virgin pulp stock.
~ he gel component of the.papermaking mixture comprises the exhaustively hydrated cellulosic gel described, for -6~ 83~
example, in my U.S. patents 4043862, 40~7833, and 4173248.
In its manufacture, che~ical cellulose pulp such as kraft cellulose pulp is refined and hydrated exhaustively to a,high degree at which fiber structure is almost completely destroyed. SpeciXically, this is accomplished by breaking down cellulose pulp sheets to their component individual fibers and fiber clumps, preferably by adding the dry sheets and water to a conventional hydrapulper and hydrapulping at a stocX consistency of from 1 to 10%, preferably from 6 to 8%. This requires about 30 minutes.
The resulting pulp then is fed in controlled flow to a selec~ed disc-type or conical-type primary refiner. There preferably are three such refiners arranged in series with a flow-restricting valve downstream from the last refiner to insure an adequate pressurized refiner dwell time. These abrade the pulp and hydrate it to a high degree, thereby forcing water through the cellulosic structure.
The resulting par~ially refined and hydrated pulp is then fed to a secondary refiner of the same general class as the primary refiners~ but which is effective to complete the hydration~ The pulp is reduced in size to values impart-ing to it TAPPI standard drain times of at least 350 seconds, preferably above 900 seconds. This is accomplished by a shearing action which almost completely destroys the fi~er-structure o~ the pulp and hydrates i~ exhaustively. Thissupple~ental and exhaustive refining greatly improves the gualities of the pulp as a ~ind2r, dispe~sing agen~ and re ~Z~3z~8 _ , tention agent when used in the manufacture of the herein described high strength paper.
In particular, it makes of the gel an ~ixreversible~
binder. As a result, paper made with it is highly water resistant.
A method other than the TAPPI drain time test for characterizing a gel suitable for the present purpose is to determine the shrinkage upon drying of the handsheet produced by the TAPPI drain time test. A suitably hydrated gel will form a hand sheet which shri~ks upon drying to a diameter which is at least 25~ smal~er than its original diameter.
In another method, the hand sheet is dried and a small fl'ame applied to its underside. If the cellulose is suffi-lS ciently hydrated, this instantaneously will produce a blisteri~ the sheet.
In still a further test procedure, 250 milleliters of the gel slurry is dried into a solld ball. If the gel is sufficiently hydrated, the ball will sink when dropped into water and thereafter will remain hard without swelling for an indefinite period of submergence.
In addition to the cellulosic gel prepared as described abov~, varîous additives may also be included in the paper-making ~urnish as desirable or necessary. These may include small proportions of dyes, rot-proofing agents, wet strength agents, wax, and the lik~.
~2~33Z~8 The pulp may be bleached if desired, in which case it usually is preferred to use a bleached gel as well.
To prepare the furnish, all the foregoing materials.
a~e added to a suitable mixer such as a Waring blender and mixed to uniformity. The resulting mixture then is added to the headbox of the paper machine, and run into a felted sheet, which is pressed and dried to ~orm the final paper product.
E~PLES
The process of my inve~tion is illustrated in the following examples wherein the amounts of the constituents are given in percent by weight, dry weight basis.
A conventional kraft bag-making stock refined to a freeness of CSF S50 was mixed with about 24~ by weight of pulp having a freeness of about CS~ 550 and containing secondary fibers derived from hydxapulping principally corrugate~ kraft ~oxes and passing the resulting pulp through a deflaker for preliminary refining in order to break down fiber bundles and clumps. The resulting pulp mixture had a consistency of about 0.3~. It was mixed with exhaustively hydrated cellulosic gel prepared as outlined above and having a TAPPI drain time of 550 seconds and a shrinkage of 27~ when subjected to the handsheet drying test.
~he pulp and gel were formulated into 6 test mixtures.
containing respectively 0, 2, 4, 6, 8 and 10~ gel.
~ ~3~ ~8 The mixtures were run into standard test hand sheets having a weight of 200 grams per square meter. These then were ;tested by the Standard TAæPI Test for measuring stiff-ness, CSF freeness, burst, tear and tensile. The results are given in conventional TAPPI test units in the table below.
% GEL STIF~NESS FREENESS BURST TEl~RTENSII;E
0 55 720 16~ 320 17,1 2 50 700 172 342 17,6 4 80 69D 198 ~76 19,3 6 75 670 190 392 .25,1 8 75 670 187 408 22,7 63~ 161 32~ 19.8 Inspecti~n of the above test data illustrates clearly tha~ inclusion of as much as 8% gel reduces the CS~ freeness but a small amount, i.e. from 720 to 670. This is not a sufficient reduction to materially increase the drain time of the furnish on the wire.
The results inclicate further a significant increase in strength, for example, an increase in tensile strength of from 17.1 to 22.7.
If.the gel binder were to be omitted, refining of the original virgin stock to a freeness of CSF 400 to 45~ w~uld be reguired to attain equivalent sheet strength, with at~endant high ref ining costs.
,. :
3LZ~3~2~3 Other benefits accrue from the use of cellulosic gel in the manufacture of kraft paper.
Its use permits the addition of lower cost fibers t~ the paper sheet without significant reduction o~ strength properties.
The qel can be made from a variety of fiber raw materials as well as from conventional kraft and sulfite pulp.
~ t 6% gel usage, with con~entional pressing, it ma~es a thicker sheet at the same welght as the regular pulp.
~ccordingly a lighter wei~ht sheet having acceptable physical properties can be made at present thicknesses.
The gel usage gives a paper sheet with a harder, smoother surface.
The reinfDroing effect of the gel shows on papers made from hardwoods, so~t woods, recycled paper and thermo mechanical pulp.
Use of gel in corrugating medium gives a substa~tial increase in compres~ion resistance. This pexsists under conditions of very high humidity.
Gel is an excellent fiber retention aid. It holds onto most of the very fine fibers which normally are lost to the formi~g wire of the paperma~ing machineO
If the papçr machine is improved so it will ru~ faster, as by installing an ~extended nip~ or ot~er thermal or mechanical impro~ements, the use of gel will permit the additional pulp ~eeded to come from the lower cost secondary fiber sources listed above.
L;283~8 In sum, the use of cellulosic gel in kraft paper improves all impo~tant sheet physical properti~ and ~nakes possible the production of higher quality paper ~t lower Gost.
S Having thus described my inventiorl in spscific embodi-ments, I claim as new and desire to protect by Letters Pa~ent:
,~
- . - ,, ' - ~ .
Claims (6)
1.
The process of making high strength kraft paper which comprises:
(a) mechanically refining kraft paper-making pulp to a freeness value of about CSF 500-800;
(b) forming a fluid mixture of from about 90 to about 99% of the resulting refined pulp and from about 1 to about 10% of hydrated cellulosic gel binder having a TAPPI drain time of at least 350 seconds, percent being expressed as percent by weight on a dry solids basis, (c) the kraft paper-making pulp comprising from about 40 to about 100% by weight virgin kraft pulp and from about 0 to about 60% by weight, dry weight basis, short fibered hardwood papermaking pulp or short fibered reclaim paper-making pulp, (d) running the fluid mixture into a felted sheet and (e) pressing and drying the sheet to form the kraft paper product.
The process of making high strength kraft paper which comprises:
(a) mechanically refining kraft paper-making pulp to a freeness value of about CSF 500-800;
(b) forming a fluid mixture of from about 90 to about 99% of the resulting refined pulp and from about 1 to about 10% of hydrated cellulosic gel binder having a TAPPI drain time of at least 350 seconds, percent being expressed as percent by weight on a dry solids basis, (c) the kraft paper-making pulp comprising from about 40 to about 100% by weight virgin kraft pulp and from about 0 to about 60% by weight, dry weight basis, short fibered hardwood papermaking pulp or short fibered reclaim paper-making pulp, (d) running the fluid mixture into a felted sheet and (e) pressing and drying the sheet to form the kraft paper product.
2.
The process of claim 1 wherein the kraft papermaking pulp is mechanically refined to a freeness value of about CSF 600-750.
The process of claim 1 wherein the kraft papermaking pulp is mechanically refined to a freeness value of about CSF 600-750.
3.
The process of claim 1 wherein the fluid mixture comprises from about 94% to about 98% refined pulp and from about 2% to about 6% hydrated cellulosic gel binder.
The process of claim 1 wherein the fluid mixture comprises from about 94% to about 98% refined pulp and from about 2% to about 6% hydrated cellulosic gel binder.
4.
The process of claim 1 wherein the kraft papermaking pulp comprises substantially 100% by weight virgin kraft pulp.
The process of claim 1 wherein the kraft papermaking pulp comprises substantially 100% by weight virgin kraft pulp.
5.
The process of claim 1 wherein the papermaking pulp is refined to a freeness of about CSF 600-750 and the fluid mixture comprises from about 94% to about 98% refined pulp and from about 2% to about 6% hydrated cellulosic gel binder, and wherein the cellulosic gel binder has a TAPPI drain time of at least about 350 seconds.
The process of claim 1 wherein the papermaking pulp is refined to a freeness of about CSF 600-750 and the fluid mixture comprises from about 94% to about 98% refined pulp and from about 2% to about 6% hydrated cellulosic gel binder, and wherein the cellulosic gel binder has a TAPPI drain time of at least about 350 seconds.
6.
The high strength, cellulosic-gel-containing kraft paper product of the process of claim 1.
The high strength, cellulosic-gel-containing kraft paper product of the process of claim 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000541892A CA1283258C (en) | 1987-07-13 | 1987-07-13 | High strength, cellulosic-gel-containing kraft paper and process for making the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000541892A CA1283258C (en) | 1987-07-13 | 1987-07-13 | High strength, cellulosic-gel-containing kraft paper and process for making the same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1283258C true CA1283258C (en) | 1991-04-23 |
Family
ID=4136068
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000541892A Expired - Fee Related CA1283258C (en) | 1987-07-13 | 1987-07-13 | High strength, cellulosic-gel-containing kraft paper and process for making the same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1283258C (en) |
-
1987
- 1987-07-13 CA CA000541892A patent/CA1283258C/en not_active Expired - Fee Related
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