CA1266730A - Papermaking aid - Google Patents
Papermaking aidInfo
- Publication number
- CA1266730A CA1266730A CA000527099A CA527099A CA1266730A CA 1266730 A CA1266730 A CA 1266730A CA 000527099 A CA000527099 A CA 000527099A CA 527099 A CA527099 A CA 527099A CA 1266730 A CA1266730 A CA 1266730A
- Authority
- CA
- Canada
- Prior art keywords
- paper
- anionic
- silica
- binder
- cationic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/63—Inorganic compounds
- D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
- D21H17/68—Water-insoluble compounds, e.g. fillers, pigments siliceous, e.g. clays
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/20—Macromolecular organic compounds
- D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
- D21H17/24—Polysaccharides
- D21H17/28—Starch
- D21H17/29—Starch cationic
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/20—Macromolecular organic compounds
- D21H17/33—Synthetic macromolecular compounds
- D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D21H17/41—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups
- D21H17/42—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups anionic
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/20—Macromolecular organic compounds
- D21H17/33—Synthetic macromolecular compounds
- D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D21H17/41—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups
- D21H17/42—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups anionic
- D21H17/43—Carboxyl groups or derivatives thereof
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
Abstract
An improved binder for use in paper-making containing three ingredients, a cationic starch having a degree of substitution of at least 0.01, a high molecular weight anionic polymer having a molecular weight of at least 500,000 and a degree of anionic substitution of at least 0.01, and a dispersed silica having a particle size ranging from about 1 - 50 nano-meters.
Description
~ ~15730 INTRODUCT I ON
The present invention relates to paper-making proces-ses and products made thereby and, more particularly, to the use of a specific coacervate binder to achieve better binding between cellulosic fibers used in paper-making processes using cellulosic fiber slurries, particularly when those slurri~s also contain various inorganic fillers and/or pigment materials characterized by having an electrically charged surface charac-ter.
The use of the binders of this inven-tion allows the papermaker to operate at a higher speed because the paper sheet formed i9 more easily dewatered. In adclit:ion, improved reten-~ion oE added m:lncral materials used in paper-malcing processes, such materials bein~ varlo~l~ clays, Tio2 ancl other p:Lgments, and the like, is achieved by using the coacervate binders of my invention. Because improved retention and improved dewatering are observed using the improved binders of this invention, it is also an object of this invention to improve clariication of the white water resulting from the paper-making processes Using the improved binders of this invention.
Therefore, this invention seeks to present to the papermaker an improved coacervate binder which can achieve both improved dewatering and improved retention of mineral fillers and pigments used in the paper-making process.
The invention further seeks to achieve a paper having improved strength characteristics.
The invention further seeks to present to the paper-maker an improved coacervate binder comprising a tertiary com-~ination of a cationic starch, an anionic high molecular weight 7~
polymer, and a dispersed silica, which binder can achieve improved dewatering, improved mineral pigment retention, and improved operating speeds of the paper-making machine - la -~i673~
without loss in paper strength or other familiar characteristics required in a paper sheet.
PRIOR PRACTICES
U.S. 3,253,978, Bodendorf et al, teac:hes a method of forming an inorganic water-laid sheet containing colloidal silica and a cationic starch. This invention combines colloidal silica and a cationic agent, preferably a cationic starch in the head box of a paper-making machine which is manufacturing a strictly inorganic fibrous sheet. The type of paper being manufactured is, therefore, referred to as an inorganic sheet and utilizes inorqanic fibers, such as glass fibers, quartz fibers, ceramic fibers, mineral wool, glass flakes, quartz flakes, mica flakes and combinatlons thereof. In colurnn 4, lines 53 et seq., of ~odendorf et al., teach that organic fi~ers may also be incorporated in the sheet but that the presence of substantial percentages of these organic materials in these kinds of sheet products are considered deleterious for intended applications of these inorganic sheets.
U.S. 4,385,961, Svendling, et al, teaches a paper-making process in which a cellulosic pulp is formed, and in which a binder is used, which binder comprises a colloidal silicic acid and a cationic starch. The manner of addition is taught to involve the initial addition of a portion of a colloidal silicic acid to the paper-making stock followed suDsequently Dy tne addition of cationic starch, which then is followed, finallyJ by the addition of the remainder of the colloidal silicic acid prior to the formation of the paper sheet.
t730 U.S. 4,388,15G, Sunden, et al, continues to teach the use of a binder comprising colloidal silicic acid and cationic starch for improving paper and the retention of various paper stock components.
TE~E INVENTION
The present invention is directed to a process for making paper which process comprises admixing with paper-making stock, containing a sufficient amount of cellulosic pulp to give a finished paper containing at least 50 weight percent cellulosic fiber, from about 0.1 to 15~ based on the weight of the pulp in the s-tock, oE a coacervate binder wherein the coa-cervate binder comprises a cationicstarch having a degree of suhsti-tution ran~.Ln~ bctween a~out 0.01 to about 0.20 in combi-nation with an anionic combination o.E an anionic high molecular weight polymer having a molecular weight of at least 500,000 and a degree of anionic substitution of at least 0.01 and a dispersed silica having a particle size ranging from 1 to 50 nm; and wherein the weight ratio of anionic polymer to silica ranges from about 20:1 to about 1:10, and wherein the cationic starch to silica ratio is be-tween about 100:1 to 1:1, and wherein said coacervate binder is admixed with the paper-making stock prior to formation of the paper.
The invention is further directed to a process for making paper which process comprises adding a binder to an aqueous paper-making stock, containing a sufficient amount of cellulosic pulp to give a finished paper having at least 50 weight percent cellulosic fiber, the cellulosic pulp having dispersed therein a mineral filler wherein the mineral filler . ~
material has at least partial anionie surface eharaeteristics and the binder is a coacervate binder consisting of a cationi-cally modified potato stareh having a degree of eationie subs-titution ranging from about 0.01 to 0.15 in eombination with an anionie polymer having a moleeular weight of at least l,OOO,OOo and a degree of anionie substitut:ion ranging from about 0.05 to about 0.95, and fur-ther in eombination with a dispersed sili.ea having a partiele size ranging from about lnm to about 50nm, wherein the cationic starch to silica ratio is from about 100:1 to about 30:1; the anionic eombination has a weiyht ratio of polymer:silica ranging from about 20:1 to about l:.L, and ~ urther whe:rein the total eoacervate binder to mLneral .Eiller we:LcJht ratLo, on a solicls basis, is ;erom about 0.005:1 to about 1:1, and further wherein said binder is formed by admixing with the paper-making stoek, prior to formation of the paper, i.n sequenee, the eationie stareh, the anionie polymer, and then the dispersed siliea.
The invention is also directed to a coacervate binder ~or use in a paper-making process using a eellulosie pulp containing at least 50 weight percent cellulose which comprises in combination:
A. from 50-90 weight percent of a cationie potato stareh having a degree of eationie substitution ranging from 0.010 to about 0.150;
B. from 10-40 weight percent of an anionlc polymer having a moleeular weight of at least 500,000, 73~
and a degree to anionic substitution ranging between about 0.01 to l.0; and C. from about 0.1 to 5 weight percent of a disper-sed silica having a particle size ranging bet-ween about 1 to 50 nm.
The use of the binder described above is preferably accomplished by adding to the beater or mixar a cationic starch having a cationic substitution ranging between .01 and 0.15, which cationic starch is preferably derived from a modified potato starch, which potato starch normally contains some small amount of covalently bound phosphorous conta.inl:ng func-tional groups ancl :L~ a h.icJhly branched amylopectin type o:E
~tarah. Ilowcve.r, :Lt mu~k bc pointed out that other cat:Lonical-ly modiEled sta~ches, .eor ~xample, cationic starch derived from corn starch, cationic starches derived from waxy maize, and the like, may be used in the practice of my invention and in the formulation of our improved binder, as long as the degree of cationic substitution on the starch ranges from about 0.01 to about 0.20, preferably between about 0.02 to about 0.15, and most preferabl~ between about 0.025 to about O .10 ~
To the cationic starch admixed with cellulosic fibers, the p~ of the paper stock ranges from about 4 to about 9, preferably in the headbox of a paper-making machine, is added a quantity of an admixture of a high molecular weight anionic polymer and a dispersed silica, which admixture contains a ratio of anionic polymer to dispersed silica ranging between about 20:1 to about l:lO on a weight-to-weight basisO
73~
This coacervate binder may ~e formed by initially admixing the cationic starch with the cellulosic fiber slurry used in th~
paper-making process. After the cationic starch has been fully admixed, an electroneutralizing amount of the admixture of anionic polymer and dispersed silica may be then added to the paper-making stock containing the cationic starch.
By an electroneutralizing amount of the anionic combination, we mean that sufficient amounts of the combination of both the anionic polymer and the dispersed silica should be added to the paper-making gtock containing the cationic starch in such a way as to approachwithin 75 to 125 percent of elec-troneukrality. Depending on the character oE the cellulosic Eib~r, th~ t~pe, amount and character oE inor~anic E:illcr/
p:igmont, as well a8 the character oE -the cation:ic s~arch, thls electroneutralizing amount o~ anionic combined ingredients can be achieved by adding anywhere from about 75 to 125 percent of an electroneutralizing amount of the combination of anionic polymer and silica sol to the cationically modified starch/
paper stock admixture. On a weight basis, this will vary considerably depending upon the ratio of anionic polymer to silica sols, as well as depending upon the type of anionic polymer chosen and the type of silica dispersion chosen. It will also vary according to the character, type, amount and the like of cationic starch used, as well as the types of fiber, fillers, and the like, used to form the paper stock.
Sunden, et al, U.S. 4,388,150, teaches the use of a weight ratio of cationic starch to silica ranging between 1:1 and 25:1.
3~
Svendling, et al, U.S. 4,385,961, again teaches a weight ratio of cationic starch to silica ranging between 1:1 to 25:1 in a binder use which is irnproved by first adding colloidal silicic acid and then a cationic starch, forming an agglomerate, and then adding the remainder of colloidal silicic acid to the paper-making stock prior to the formation of the paper sheet. This complicated procedure normally requires that the first portion of colloidal silicic acid comprises between 20-90 percent of the total colloidal silicic acid added to the paper-making stoc~.
The improved coacervate binder of this invention uses a combination of cationic starch, preferably a cationically modified potato starch having a degree of cationic substitution ranging between about 0.02 to about 0.15, wherein said potato starch also contains naturally, not synthetically, bound phos-phorous containing functionality, with an electroneutralizing amount of the combination of a high molecular weight anionic polymer and a dispersed silica wherein the dispersed silica has a particle size ranging between about l.0 nanometers to about 50 n~no~eters.
The combination of anionic polymers to dispersed silica, preferably a colloidal silicic acid or a colloidal silica sol normally ranges within a weight ratio of be-tween 20:1 to about l:lO, and, most preferably, ranges between a weight ratio of anionic polymer to silica of from about 15:1 to about l:l.
The Anionic Polymers The anionic polymers used are preferably high mole-t73~1 cular weight water soluble polymers having a molecular weight of at least 500,000, preferably a molecular weight of at least 1,000,000 and most preferably having a molecular weight ran~ing between about 5,000,000 - 25,000,000.
These anionic polymers are preferably water-soluble vinylic polymers containing monomers from the group acrylamide, acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid (AMPS*) and/or admixtures thereof, and may also be either hydrolyzed acrylamide polymers or copolymers of acrylamide or its homologues, such as methacrylamide, with acrylic acid or its homologues, such as methacrylic acid, or perhaps even with monomers, such as maleic acid, itacon.ic ac;id or even monomers ~uch a~ viny.l ~ul.eonic acid, AMPS, ancl other sul.~ona-te con-tain-in~ monomer~. Irhe anion;lc polymers may be homopolymers, copo-lymers, terpolymers or contain multiple monomeric repeating units. The anionic polymers may also be sulfonate or phospho-nate containing polymers which have been synthesized by modi-fying acrylamide polymers in such a way as to obtain sulfonate or phosphonate substitution, or admixtures thereof. The anio-nic polymers may be used in solid, powder -Eorm, aEter dissolu-tion in water, or may be used as water-in-oil emulslons, wherein the polymer is dissolved in the dispersed water pha.se of these emulsions.
*Trademark - 6b -~L~6~i73C~
It is preferred that the anionic polymers have a molecular weight of at least l,OOû,000. The most preferred molecular weight is at least 5,000,000, with best results observed when the molecular weight is between 7.5-25 million.
The anionic polymers have a degree of substitution of at least û.01, preferably a degree of substitution of at least 0.05, and most preferably a degree of substitution of at least 0.10 -û.50. By degree of substitution, we mean that the polymers contain randomly repeating monomer units containing chemical functionality which when dissolved in water become anionically charged, such as carboxylate groups, sulfonate groups, phosphonate groups, and the like. As an example, a copolymer of acrylamide (AcAm) and acrylic acid (AA) wherein the AcAm:AA
monom@r molc ra~lo 1~ 10, would have a deyree of su~sl:ltution o~ ~.lq. ~lmllarly, co~olymers of ~eAm:~A wlth m~nomer mole ratios of 50:5û would have a de~ree of anlonic substitution of 0.5.
The Disoersed Silica Preferably, the anionic polymers are used in combination with a dispersed silica having a particle size ranging between about 1-50 nanometers (nm), preferably having a particle size ranging between 2-25 nm, and most preferably having a particle size ranging between about 2-15 nm. This disoersed silica may oe in the form of colloidal silicic acid, silica sols, fumea sillca, agglomerated silicic acid, silica gels, and preciPitated silicas, as long as the particle size or ultimate particle size is within the ranges mentioned above. The dispersed silica is normally present at a ratio of cationic starch to silica of from about 100:1 to about 1:1, and is Preferably present at a ratio of from 75:1 to about 30:1.
73~
This combined anionic admixture is used within a dry weight ratio of from about ~0:1 to about 1:10 of arlionic polymer to silica, preferably from abou-t 10:1 to about 1:~, and most preferably from about 8:1 to about 1:1.
The Anionic Combination When the anionic combination (or anionic admixture) is used in my invention, it is preferable to add the polymer and dispersed silica to the paper-making stock after the addition of the cationic starch has occurred, and sufficient time and mixing energy used to accompllsh a thorough homogeneous admixture of cationic starch and the cellulosic slurries, mineral fillers, clays, plgments, and other inorganic components of the paper-making stock.
The anionic ~mlxt~lrQ ls therl a~de~d so as to essentl,311y accomplish an electroneutralization of the cationic charges contained in the paper stock. Since the cellulosic fibers, and most inorganic pigments and clays, such as TiO2 pigment, normally carry a negatively charged surface, it is a relatively simple matter to calculate electroneutrality on the basis of the amount of cationic starch added, the ~egree of substitution of cationic functionality on the starch added, and the amount of any other additional species carrying a cationic charge which may be present in the DaDer stock, i.e., alumina sols, alum, and the like.
Depending on the molecular weight, degree of anionic substitution, and tyDe of polymer used, as well as on the amount and type of cationic starch used, the starch to polymer weight ratio can range from about 50:1 to about 5:1. Simultaneously, ~6~310 the polymer to silica ratio normally runs from about 20:1 to about 1:10, and, as before, preferably ranges from about 10:1 to about 1:5, and most preferably ranges from about 8:1 to 1:1.
The most preferred results are obtained when the starch to sili-ca ratios range from about 75:1 to about 3():1.
The anionic combination or admixture of anionic poly-mer to silica, as described above; can be rnade prior to admix-ture with the paper stock containing the cationic starch, and then added to the paper stock, or preferably is made in situ during the paper-making process by adding to the paper stock, in sequence, the cationic starch, then the anionic polymer, and Einally the dispersed silica.
~ b~ ve~l ~hAt ~ ~o~carvat~ comp:lcx o:E undoter-minad ~ c~ur~ rm~d, :ln ~h~ nce O e kh~ paper skock and which may in~lu~;lc compon~nts o.E the papcr stock, between the cationic starch and the anionic polymer, and that this pre-coacervate complex contains, therein, at least some positive charges, which positive charges can then attract and bind both the added dispersed silica which carries a negative surface charge, as well as the cellulosic fibers, inorganic pigments, and the like. It is presumed tha-t the formation of the coacer-vate complex between starch; polymer; and sil:ica leads to the improved performance observed with my system relative to the use of any other combination of ingredients known in the art, such as only starch plus silica. ~lthough it would be difficult to demonstrate that this mechanism exactly accounts for the improved performance observed, and my invention should not be limited in any way to my attempted mechanistic explanation, it ~673(:~
is a simple matter to demonstrate the improved perEormance of my three component coacervate binder system.
The following examples should suffice to demonstrate my new binding system, methods and compositions.
In the drawings, referred in the Examples, which illustrate embodiments of the invention, Figure 1 is a graph comparing (per cent) retention of cationic starch-colloidal silica versus cationic starch-colloidal silica and anionic polyacrylamide Figure 2 is a graph comparing drainage rates of cationic starch-colloidal silica versus cationic starch-colloidal silica and anionic polyac.r~lamide FicJur~ 3 i~ n ~raph compar:in~ ~ra:lnage ra~e~ o~
va~.iou~ b.ind~ ~y~t~m~ w.lth alld w.lthout the aclclition o:~ an alumina sourcc Figure 4 is a graph comparing turbidity of various binder systems with and without the addition oE an alumina source Example I
Paper stock was prepared at 0.7~ consistency from a thick paper stock (3.~ cellulosic fibers) and clari:Eied white water obtained from a paper mill. ~he stock had a pH of 7.0-7.5.
Cationic potato starch having a degree of substitu-tion of 0.025 was prepared at a 2.0 weight percent solution in water, and diluted further, immediately prior to application to a concentration of 0.875~.
~;67~
A high molecular weight (about 10-20 million) anionic polyacrylamide containing about 30 mole percent acrylic acid and 70 mole perc~nt acrylamide monomer, in the form of a water~
in-oil latex containing about 30 weight percent polymer was inverted and diluted into water following the teachings of Anderson, et al, U.S. Re 28,474 and U.S. Re 28,576. The polymer solution was made up at 2.0 weight percent active polymer and further diluted to 0.0875 weight percent immediately prior to use.
A 15 wei~h-t percent silica sol (or colloidal sil;ica) havln~ a paxticle ~ix~ oE about 4 mn was ~liJutcd wLth waL~r to ~.0~75 wei~hk p~xa~n~. rrw~ sqparat~ b~l~ch~s of7~ pap~x ~)~oak wcre obta:ln~l rom th~ s~me rnLll approxLmat~ly kwo weelc~ apart.
The paper stock was admixed with cationic starch and then the various amounts of anionic polymers and/or silica sol were added thereto. Laboratory tests were completed using an "Alchem Tester", which is designed to measure both water drain-age rates under controlled conditions and also turbidity (NTU) which is related to retention by the forrnula:
~ Retention Turbidi-ty (Blank) - Turbidity (Sample) x 100 Turbidity (Blank) The data from these tests are presented in Tables I
and II.
Table I presents data from the first paper stock.
Table II presents data from the second paper stock.
- lOa -~661'73~
TABLE I
Starch Silica PAM* DrainageTurbidity~*
#/T #/T #/T (ml/5 sec) (NTU) o o o 112 1640 0 0.5 126 390 0 0 2 ln~ 420 1 (~ t~ ~ q ~;
The present invention relates to paper-making proces-ses and products made thereby and, more particularly, to the use of a specific coacervate binder to achieve better binding between cellulosic fibers used in paper-making processes using cellulosic fiber slurries, particularly when those slurri~s also contain various inorganic fillers and/or pigment materials characterized by having an electrically charged surface charac-ter.
The use of the binders of this inven-tion allows the papermaker to operate at a higher speed because the paper sheet formed i9 more easily dewatered. In adclit:ion, improved reten-~ion oE added m:lncral materials used in paper-malcing processes, such materials bein~ varlo~l~ clays, Tio2 ancl other p:Lgments, and the like, is achieved by using the coacervate binders of my invention. Because improved retention and improved dewatering are observed using the improved binders of this invention, it is also an object of this invention to improve clariication of the white water resulting from the paper-making processes Using the improved binders of this invention.
Therefore, this invention seeks to present to the papermaker an improved coacervate binder which can achieve both improved dewatering and improved retention of mineral fillers and pigments used in the paper-making process.
The invention further seeks to achieve a paper having improved strength characteristics.
The invention further seeks to present to the paper-maker an improved coacervate binder comprising a tertiary com-~ination of a cationic starch, an anionic high molecular weight 7~
polymer, and a dispersed silica, which binder can achieve improved dewatering, improved mineral pigment retention, and improved operating speeds of the paper-making machine - la -~i673~
without loss in paper strength or other familiar characteristics required in a paper sheet.
PRIOR PRACTICES
U.S. 3,253,978, Bodendorf et al, teac:hes a method of forming an inorganic water-laid sheet containing colloidal silica and a cationic starch. This invention combines colloidal silica and a cationic agent, preferably a cationic starch in the head box of a paper-making machine which is manufacturing a strictly inorganic fibrous sheet. The type of paper being manufactured is, therefore, referred to as an inorganic sheet and utilizes inorqanic fibers, such as glass fibers, quartz fibers, ceramic fibers, mineral wool, glass flakes, quartz flakes, mica flakes and combinatlons thereof. In colurnn 4, lines 53 et seq., of ~odendorf et al., teach that organic fi~ers may also be incorporated in the sheet but that the presence of substantial percentages of these organic materials in these kinds of sheet products are considered deleterious for intended applications of these inorganic sheets.
U.S. 4,385,961, Svendling, et al, teaches a paper-making process in which a cellulosic pulp is formed, and in which a binder is used, which binder comprises a colloidal silicic acid and a cationic starch. The manner of addition is taught to involve the initial addition of a portion of a colloidal silicic acid to the paper-making stock followed suDsequently Dy tne addition of cationic starch, which then is followed, finallyJ by the addition of the remainder of the colloidal silicic acid prior to the formation of the paper sheet.
t730 U.S. 4,388,15G, Sunden, et al, continues to teach the use of a binder comprising colloidal silicic acid and cationic starch for improving paper and the retention of various paper stock components.
TE~E INVENTION
The present invention is directed to a process for making paper which process comprises admixing with paper-making stock, containing a sufficient amount of cellulosic pulp to give a finished paper containing at least 50 weight percent cellulosic fiber, from about 0.1 to 15~ based on the weight of the pulp in the s-tock, oE a coacervate binder wherein the coa-cervate binder comprises a cationicstarch having a degree of suhsti-tution ran~.Ln~ bctween a~out 0.01 to about 0.20 in combi-nation with an anionic combination o.E an anionic high molecular weight polymer having a molecular weight of at least 500,000 and a degree of anionic substitution of at least 0.01 and a dispersed silica having a particle size ranging from 1 to 50 nm; and wherein the weight ratio of anionic polymer to silica ranges from about 20:1 to about 1:10, and wherein the cationic starch to silica ratio is be-tween about 100:1 to 1:1, and wherein said coacervate binder is admixed with the paper-making stock prior to formation of the paper.
The invention is further directed to a process for making paper which process comprises adding a binder to an aqueous paper-making stock, containing a sufficient amount of cellulosic pulp to give a finished paper having at least 50 weight percent cellulosic fiber, the cellulosic pulp having dispersed therein a mineral filler wherein the mineral filler . ~
material has at least partial anionie surface eharaeteristics and the binder is a coacervate binder consisting of a cationi-cally modified potato stareh having a degree of eationie subs-titution ranging from about 0.01 to 0.15 in eombination with an anionie polymer having a moleeular weight of at least l,OOO,OOo and a degree of anionie substitut:ion ranging from about 0.05 to about 0.95, and fur-ther in eombination with a dispersed sili.ea having a partiele size ranging from about lnm to about 50nm, wherein the cationic starch to silica ratio is from about 100:1 to about 30:1; the anionic eombination has a weiyht ratio of polymer:silica ranging from about 20:1 to about l:.L, and ~ urther whe:rein the total eoacervate binder to mLneral .Eiller we:LcJht ratLo, on a solicls basis, is ;erom about 0.005:1 to about 1:1, and further wherein said binder is formed by admixing with the paper-making stoek, prior to formation of the paper, i.n sequenee, the eationie stareh, the anionie polymer, and then the dispersed siliea.
The invention is also directed to a coacervate binder ~or use in a paper-making process using a eellulosie pulp containing at least 50 weight percent cellulose which comprises in combination:
A. from 50-90 weight percent of a cationie potato stareh having a degree of eationie substitution ranging from 0.010 to about 0.150;
B. from 10-40 weight percent of an anionlc polymer having a moleeular weight of at least 500,000, 73~
and a degree to anionic substitution ranging between about 0.01 to l.0; and C. from about 0.1 to 5 weight percent of a disper-sed silica having a particle size ranging bet-ween about 1 to 50 nm.
The use of the binder described above is preferably accomplished by adding to the beater or mixar a cationic starch having a cationic substitution ranging between .01 and 0.15, which cationic starch is preferably derived from a modified potato starch, which potato starch normally contains some small amount of covalently bound phosphorous conta.inl:ng func-tional groups ancl :L~ a h.icJhly branched amylopectin type o:E
~tarah. Ilowcve.r, :Lt mu~k bc pointed out that other cat:Lonical-ly modiEled sta~ches, .eor ~xample, cationic starch derived from corn starch, cationic starches derived from waxy maize, and the like, may be used in the practice of my invention and in the formulation of our improved binder, as long as the degree of cationic substitution on the starch ranges from about 0.01 to about 0.20, preferably between about 0.02 to about 0.15, and most preferabl~ between about 0.025 to about O .10 ~
To the cationic starch admixed with cellulosic fibers, the p~ of the paper stock ranges from about 4 to about 9, preferably in the headbox of a paper-making machine, is added a quantity of an admixture of a high molecular weight anionic polymer and a dispersed silica, which admixture contains a ratio of anionic polymer to dispersed silica ranging between about 20:1 to about l:lO on a weight-to-weight basisO
73~
This coacervate binder may ~e formed by initially admixing the cationic starch with the cellulosic fiber slurry used in th~
paper-making process. After the cationic starch has been fully admixed, an electroneutralizing amount of the admixture of anionic polymer and dispersed silica may be then added to the paper-making stock containing the cationic starch.
By an electroneutralizing amount of the anionic combination, we mean that sufficient amounts of the combination of both the anionic polymer and the dispersed silica should be added to the paper-making gtock containing the cationic starch in such a way as to approachwithin 75 to 125 percent of elec-troneukrality. Depending on the character oE the cellulosic Eib~r, th~ t~pe, amount and character oE inor~anic E:illcr/
p:igmont, as well a8 the character oE -the cation:ic s~arch, thls electroneutralizing amount o~ anionic combined ingredients can be achieved by adding anywhere from about 75 to 125 percent of an electroneutralizing amount of the combination of anionic polymer and silica sol to the cationically modified starch/
paper stock admixture. On a weight basis, this will vary considerably depending upon the ratio of anionic polymer to silica sols, as well as depending upon the type of anionic polymer chosen and the type of silica dispersion chosen. It will also vary according to the character, type, amount and the like of cationic starch used, as well as the types of fiber, fillers, and the like, used to form the paper stock.
Sunden, et al, U.S. 4,388,150, teaches the use of a weight ratio of cationic starch to silica ranging between 1:1 and 25:1.
3~
Svendling, et al, U.S. 4,385,961, again teaches a weight ratio of cationic starch to silica ranging between 1:1 to 25:1 in a binder use which is irnproved by first adding colloidal silicic acid and then a cationic starch, forming an agglomerate, and then adding the remainder of colloidal silicic acid to the paper-making stock prior to the formation of the paper sheet. This complicated procedure normally requires that the first portion of colloidal silicic acid comprises between 20-90 percent of the total colloidal silicic acid added to the paper-making stoc~.
The improved coacervate binder of this invention uses a combination of cationic starch, preferably a cationically modified potato starch having a degree of cationic substitution ranging between about 0.02 to about 0.15, wherein said potato starch also contains naturally, not synthetically, bound phos-phorous containing functionality, with an electroneutralizing amount of the combination of a high molecular weight anionic polymer and a dispersed silica wherein the dispersed silica has a particle size ranging between about l.0 nanometers to about 50 n~no~eters.
The combination of anionic polymers to dispersed silica, preferably a colloidal silicic acid or a colloidal silica sol normally ranges within a weight ratio of be-tween 20:1 to about l:lO, and, most preferably, ranges between a weight ratio of anionic polymer to silica of from about 15:1 to about l:l.
The Anionic Polymers The anionic polymers used are preferably high mole-t73~1 cular weight water soluble polymers having a molecular weight of at least 500,000, preferably a molecular weight of at least 1,000,000 and most preferably having a molecular weight ran~ing between about 5,000,000 - 25,000,000.
These anionic polymers are preferably water-soluble vinylic polymers containing monomers from the group acrylamide, acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid (AMPS*) and/or admixtures thereof, and may also be either hydrolyzed acrylamide polymers or copolymers of acrylamide or its homologues, such as methacrylamide, with acrylic acid or its homologues, such as methacrylic acid, or perhaps even with monomers, such as maleic acid, itacon.ic ac;id or even monomers ~uch a~ viny.l ~ul.eonic acid, AMPS, ancl other sul.~ona-te con-tain-in~ monomer~. Irhe anion;lc polymers may be homopolymers, copo-lymers, terpolymers or contain multiple monomeric repeating units. The anionic polymers may also be sulfonate or phospho-nate containing polymers which have been synthesized by modi-fying acrylamide polymers in such a way as to obtain sulfonate or phosphonate substitution, or admixtures thereof. The anio-nic polymers may be used in solid, powder -Eorm, aEter dissolu-tion in water, or may be used as water-in-oil emulslons, wherein the polymer is dissolved in the dispersed water pha.se of these emulsions.
*Trademark - 6b -~L~6~i73C~
It is preferred that the anionic polymers have a molecular weight of at least l,OOû,000. The most preferred molecular weight is at least 5,000,000, with best results observed when the molecular weight is between 7.5-25 million.
The anionic polymers have a degree of substitution of at least û.01, preferably a degree of substitution of at least 0.05, and most preferably a degree of substitution of at least 0.10 -û.50. By degree of substitution, we mean that the polymers contain randomly repeating monomer units containing chemical functionality which when dissolved in water become anionically charged, such as carboxylate groups, sulfonate groups, phosphonate groups, and the like. As an example, a copolymer of acrylamide (AcAm) and acrylic acid (AA) wherein the AcAm:AA
monom@r molc ra~lo 1~ 10, would have a deyree of su~sl:ltution o~ ~.lq. ~lmllarly, co~olymers of ~eAm:~A wlth m~nomer mole ratios of 50:5û would have a de~ree of anlonic substitution of 0.5.
The Disoersed Silica Preferably, the anionic polymers are used in combination with a dispersed silica having a particle size ranging between about 1-50 nanometers (nm), preferably having a particle size ranging between 2-25 nm, and most preferably having a particle size ranging between about 2-15 nm. This disoersed silica may oe in the form of colloidal silicic acid, silica sols, fumea sillca, agglomerated silicic acid, silica gels, and preciPitated silicas, as long as the particle size or ultimate particle size is within the ranges mentioned above. The dispersed silica is normally present at a ratio of cationic starch to silica of from about 100:1 to about 1:1, and is Preferably present at a ratio of from 75:1 to about 30:1.
73~
This combined anionic admixture is used within a dry weight ratio of from about ~0:1 to about 1:10 of arlionic polymer to silica, preferably from abou-t 10:1 to about 1:~, and most preferably from about 8:1 to about 1:1.
The Anionic Combination When the anionic combination (or anionic admixture) is used in my invention, it is preferable to add the polymer and dispersed silica to the paper-making stock after the addition of the cationic starch has occurred, and sufficient time and mixing energy used to accompllsh a thorough homogeneous admixture of cationic starch and the cellulosic slurries, mineral fillers, clays, plgments, and other inorganic components of the paper-making stock.
The anionic ~mlxt~lrQ ls therl a~de~d so as to essentl,311y accomplish an electroneutralization of the cationic charges contained in the paper stock. Since the cellulosic fibers, and most inorganic pigments and clays, such as TiO2 pigment, normally carry a negatively charged surface, it is a relatively simple matter to calculate electroneutrality on the basis of the amount of cationic starch added, the ~egree of substitution of cationic functionality on the starch added, and the amount of any other additional species carrying a cationic charge which may be present in the DaDer stock, i.e., alumina sols, alum, and the like.
Depending on the molecular weight, degree of anionic substitution, and tyDe of polymer used, as well as on the amount and type of cationic starch used, the starch to polymer weight ratio can range from about 50:1 to about 5:1. Simultaneously, ~6~310 the polymer to silica ratio normally runs from about 20:1 to about 1:10, and, as before, preferably ranges from about 10:1 to about 1:5, and most preferably ranges from about 8:1 to 1:1.
The most preferred results are obtained when the starch to sili-ca ratios range from about 75:1 to about 3():1.
The anionic combination or admixture of anionic poly-mer to silica, as described above; can be rnade prior to admix-ture with the paper stock containing the cationic starch, and then added to the paper stock, or preferably is made in situ during the paper-making process by adding to the paper stock, in sequence, the cationic starch, then the anionic polymer, and Einally the dispersed silica.
~ b~ ve~l ~hAt ~ ~o~carvat~ comp:lcx o:E undoter-minad ~ c~ur~ rm~d, :ln ~h~ nce O e kh~ paper skock and which may in~lu~;lc compon~nts o.E the papcr stock, between the cationic starch and the anionic polymer, and that this pre-coacervate complex contains, therein, at least some positive charges, which positive charges can then attract and bind both the added dispersed silica which carries a negative surface charge, as well as the cellulosic fibers, inorganic pigments, and the like. It is presumed tha-t the formation of the coacer-vate complex between starch; polymer; and sil:ica leads to the improved performance observed with my system relative to the use of any other combination of ingredients known in the art, such as only starch plus silica. ~lthough it would be difficult to demonstrate that this mechanism exactly accounts for the improved performance observed, and my invention should not be limited in any way to my attempted mechanistic explanation, it ~673(:~
is a simple matter to demonstrate the improved perEormance of my three component coacervate binder system.
The following examples should suffice to demonstrate my new binding system, methods and compositions.
In the drawings, referred in the Examples, which illustrate embodiments of the invention, Figure 1 is a graph comparing (per cent) retention of cationic starch-colloidal silica versus cationic starch-colloidal silica and anionic polyacrylamide Figure 2 is a graph comparing drainage rates of cationic starch-colloidal silica versus cationic starch-colloidal silica and anionic polyac.r~lamide FicJur~ 3 i~ n ~raph compar:in~ ~ra:lnage ra~e~ o~
va~.iou~ b.ind~ ~y~t~m~ w.lth alld w.lthout the aclclition o:~ an alumina sourcc Figure 4 is a graph comparing turbidity of various binder systems with and without the addition oE an alumina source Example I
Paper stock was prepared at 0.7~ consistency from a thick paper stock (3.~ cellulosic fibers) and clari:Eied white water obtained from a paper mill. ~he stock had a pH of 7.0-7.5.
Cationic potato starch having a degree of substitu-tion of 0.025 was prepared at a 2.0 weight percent solution in water, and diluted further, immediately prior to application to a concentration of 0.875~.
~;67~
A high molecular weight (about 10-20 million) anionic polyacrylamide containing about 30 mole percent acrylic acid and 70 mole perc~nt acrylamide monomer, in the form of a water~
in-oil latex containing about 30 weight percent polymer was inverted and diluted into water following the teachings of Anderson, et al, U.S. Re 28,474 and U.S. Re 28,576. The polymer solution was made up at 2.0 weight percent active polymer and further diluted to 0.0875 weight percent immediately prior to use.
A 15 wei~h-t percent silica sol (or colloidal sil;ica) havln~ a paxticle ~ix~ oE about 4 mn was ~liJutcd wLth waL~r to ~.0~75 wei~hk p~xa~n~. rrw~ sqparat~ b~l~ch~s of7~ pap~x ~)~oak wcre obta:ln~l rom th~ s~me rnLll approxLmat~ly kwo weelc~ apart.
The paper stock was admixed with cationic starch and then the various amounts of anionic polymers and/or silica sol were added thereto. Laboratory tests were completed using an "Alchem Tester", which is designed to measure both water drain-age rates under controlled conditions and also turbidity (NTU) which is related to retention by the forrnula:
~ Retention Turbidi-ty (Blank) - Turbidity (Sample) x 100 Turbidity (Blank) The data from these tests are presented in Tables I
and II.
Table I presents data from the first paper stock.
Table II presents data from the second paper stock.
- lOa -~661'73~
TABLE I
Starch Silica PAM* DrainageTurbidity~*
#/T #/T #/T (ml/5 sec) (NTU) o o o 112 1640 0 0.5 126 390 0 0 2 ln~ 420 1 (~ t~ ~ q ~;
2 0 1~ 360 The two component PAM and starch combLnation is superior to both starch/silica and the PAM a}one, for retention* and drainage.
PAM - An anionic polyacrylamide containing about 30% acrylic acid and having a molecular ~eight in excess of 10,000,000.
** An increase in retention is indicated by a decrease in turbidity.
~673[1 Starch Silica PAM*Drainage Turbidity #/T #/T #/T(ml/5 sec) (NTU) 0 0.00 0.0 90 1312.5 0 0O 0 o go 1280 0.00 0.0 90 1325 0.00 0.0 94 1375 0.00 0.0 86 1500 0.~0 1~0 11~ 3~0 2S ~ IlC 3~
~5 ~ 80 0.75 1.0 116 270 0.00 1.0 114 300 0.00 2.0 134 180 0.00 3.0 154 140 0.50 O.S 94 460 0.50 1.0 114 280 0.50 1.5 130 200 0.50 2.5 162 140 * PAM - The same high molecular weight anionic copolymer of acrylamide/
acrylic acid as used in Table I.
~667~
The three (3) component coacervated syste~o starch;
anionic polymer; and dispersed silica provides superior retention and drainage as compared with the two component starch/silica binder systems taught in the prior art. The starch/polymer system alone gives comparable results when compared to the starch/silica system of the prior art for some of the drainage tests. Overall, the three component coacervate binder is superior in both retention and draina~e.
These tests are further illustrated in Figures 1 and 2.
Example II
~ he a~di~lon ~o t~ pap~r skock oP a small amount o~
an ~ m~ 411r~ m~ ap~mak~ lm, I~cl.1~1m alumLnate or polyh~clroxy~lumLnum chlor:Lde, eurth~ ~ntl~nces th~
activities observed for the three component coacervate binder system. These further improvements are observed in Figures 3 and 4. When an alumina source is used, it is preferred to be used at levels ranging from about 0.01 to about 10.0 pounds active A12O3 per ton of paper (dried) manufactured.
0 ~xample III
trial was run at a paper mill in -the upper Mideast while this mill was making 67.5 pounds per ream alkaline Elne paper. The stock consisted of hardwood Kraft and softwood Xraft fiber with 20% filler loading comprised of an admixture of calcium carbonate, Kaolin, and titanium dioxide. Fillers were added to the pulper. Paper stock pH was 7.5. Polyhydroxy-aluminium chloride was added to the save-all with the reclaimed fiber and clarified water returning to the stock system.
~X
PAM - An anionic polyacrylamide containing about 30% acrylic acid and having a molecular ~eight in excess of 10,000,000.
** An increase in retention is indicated by a decrease in turbidity.
~673[1 Starch Silica PAM*Drainage Turbidity #/T #/T #/T(ml/5 sec) (NTU) 0 0.00 0.0 90 1312.5 0 0O 0 o go 1280 0.00 0.0 90 1325 0.00 0.0 94 1375 0.00 0.0 86 1500 0.~0 1~0 11~ 3~0 2S ~ IlC 3~
~5 ~ 80 0.75 1.0 116 270 0.00 1.0 114 300 0.00 2.0 134 180 0.00 3.0 154 140 0.50 O.S 94 460 0.50 1.0 114 280 0.50 1.5 130 200 0.50 2.5 162 140 * PAM - The same high molecular weight anionic copolymer of acrylamide/
acrylic acid as used in Table I.
~667~
The three (3) component coacervated syste~o starch;
anionic polymer; and dispersed silica provides superior retention and drainage as compared with the two component starch/silica binder systems taught in the prior art. The starch/polymer system alone gives comparable results when compared to the starch/silica system of the prior art for some of the drainage tests. Overall, the three component coacervate binder is superior in both retention and draina~e.
These tests are further illustrated in Figures 1 and 2.
Example II
~ he a~di~lon ~o t~ pap~r skock oP a small amount o~
an ~ m~ 411r~ m~ ap~mak~ lm, I~cl.1~1m alumLnate or polyh~clroxy~lumLnum chlor:Lde, eurth~ ~ntl~nces th~
activities observed for the three component coacervate binder system. These further improvements are observed in Figures 3 and 4. When an alumina source is used, it is preferred to be used at levels ranging from about 0.01 to about 10.0 pounds active A12O3 per ton of paper (dried) manufactured.
0 ~xample III
trial was run at a paper mill in -the upper Mideast while this mill was making 67.5 pounds per ream alkaline Elne paper. The stock consisted of hardwood Kraft and softwood Xraft fiber with 20% filler loading comprised of an admixture of calcium carbonate, Kaolin, and titanium dioxide. Fillers were added to the pulper. Paper stock pH was 7.5. Polyhydroxy-aluminium chloride was added to the save-all with the reclaimed fiber and clarified water returning to the stock system.
~X
3~
Cationic potato starch having a degree of substitution of û.025 was added to the recycled white water prior to final stock dilution. The same high molecular weight anionic polyacrylamide (PAM) as used before was added to the intake of the centri-screen. Colloidal silica in the form of a 15% sol having a particle size of from 4-5 nanometers was added immediately before the headbox.
At -the start of the trial period, stock treatment (I) was 18 #/T cationic potato starch and 2.0 #/T PAM. After 1.25 hours 0.8 #/T of colloidal silica was added to the system.
Drainage on the fourdrinier wire increased. The "wet line"
receded 2 to 3 feet and couch vacuum dropped from 22 to 19 psi.
This facilitated an increase in dilution water stream flow from 1560 to 1627 gallons/minute. Jordan refining was increased from 20 to 31 Amps. First pass retention increased from 86 to 91.5~.
Headbox consistency decreased from l.û5% to 0.69%. These changes resulted in a considerable improvement in sheet formation. Sheet moisture before the size press dropped from 6 to 1%.
Approximately 28 psi of steam was removed from the main drying section to hold sheet moisture at the size press to 5%.
Two hours after the start of the trial, cationic starch dosage was increased to 25 #/T, PAM dosage was increased to three (3) pounds per ton and colloidal silica dosage was reduced to 0.45 #/T (Stock Treatment II). First pass retention held at 89.5%, drainage on the wire, sheet drying and sheet formation remained essentially unchanged.
An increase in drainage and reduction in dryer steam usage can be utilized by increasing machine speed, hence, increased production rate, or by improved sheet formation with savings in steam costs. The latter option was adopted during the trial.
3~
No significant change in sheet strength with regards to tensile, Mullen or Scott Bond was evident, as shown below for these t~o treatments.
TREATMENT
[ II
Basis Weight 67.5 # 67.5 #
Tensile 25.0 24.û
Mullen 38.0 36.0 Scott 80nd 170.0 ].97.0 Example IV - Comparlson of Results When Silica Sol Was Added Prior to Anionic Polymer: ~
Durin~ the same trial period at the paper mill operation reviewed above, the dispersed silica injection point was moved to the inlet of the centri-screen. Previously, this silica sol injection point was at the discharge end exiting the centri-screen. ûriginally, the injection of dispersed silica followed both the injection of the cationic starch and the injection of the anionic polymer into the paper stock.
With the silica sol injected at the inlet o~ the centri-screen, the sol ~as being injected into the paper stock prior to the injection of the anionic polymer. Wit~in ~0 minutes of tnis change being made, the following negative observations ~ere made:
~266730 1. Drainage on the fourdrinier was drastically reduced as evidenced by the thruput in the headbox. Typical flows prior to the above change ranged between about 1700-1800 gallons per minute. With the silica being added prior to the anionic copolymer, the thruput fell drastically to about 90û gallons per minute.
2. Paper formation was poor. This was evidenced by the inability of the furnish to drain accompanied by the inability to put more refining on the furnish.
3. Poor drainage and increased energy consumption indicated a poor result. The paper sheet became wetter and the steam usage in the main dryer section increased by at least 15-20 psi.
Cationic potato starch having a degree of substitution of û.025 was added to the recycled white water prior to final stock dilution. The same high molecular weight anionic polyacrylamide (PAM) as used before was added to the intake of the centri-screen. Colloidal silica in the form of a 15% sol having a particle size of from 4-5 nanometers was added immediately before the headbox.
At -the start of the trial period, stock treatment (I) was 18 #/T cationic potato starch and 2.0 #/T PAM. After 1.25 hours 0.8 #/T of colloidal silica was added to the system.
Drainage on the fourdrinier wire increased. The "wet line"
receded 2 to 3 feet and couch vacuum dropped from 22 to 19 psi.
This facilitated an increase in dilution water stream flow from 1560 to 1627 gallons/minute. Jordan refining was increased from 20 to 31 Amps. First pass retention increased from 86 to 91.5~.
Headbox consistency decreased from l.û5% to 0.69%. These changes resulted in a considerable improvement in sheet formation. Sheet moisture before the size press dropped from 6 to 1%.
Approximately 28 psi of steam was removed from the main drying section to hold sheet moisture at the size press to 5%.
Two hours after the start of the trial, cationic starch dosage was increased to 25 #/T, PAM dosage was increased to three (3) pounds per ton and colloidal silica dosage was reduced to 0.45 #/T (Stock Treatment II). First pass retention held at 89.5%, drainage on the wire, sheet drying and sheet formation remained essentially unchanged.
An increase in drainage and reduction in dryer steam usage can be utilized by increasing machine speed, hence, increased production rate, or by improved sheet formation with savings in steam costs. The latter option was adopted during the trial.
3~
No significant change in sheet strength with regards to tensile, Mullen or Scott Bond was evident, as shown below for these t~o treatments.
TREATMENT
[ II
Basis Weight 67.5 # 67.5 #
Tensile 25.0 24.û
Mullen 38.0 36.0 Scott 80nd 170.0 ].97.0 Example IV - Comparlson of Results When Silica Sol Was Added Prior to Anionic Polymer: ~
Durin~ the same trial period at the paper mill operation reviewed above, the dispersed silica injection point was moved to the inlet of the centri-screen. Previously, this silica sol injection point was at the discharge end exiting the centri-screen. ûriginally, the injection of dispersed silica followed both the injection of the cationic starch and the injection of the anionic polymer into the paper stock.
With the silica sol injected at the inlet o~ the centri-screen, the sol ~as being injected into the paper stock prior to the injection of the anionic polymer. Wit~in ~0 minutes of tnis change being made, the following negative observations ~ere made:
~266730 1. Drainage on the fourdrinier was drastically reduced as evidenced by the thruput in the headbox. Typical flows prior to the above change ranged between about 1700-1800 gallons per minute. With the silica being added prior to the anionic copolymer, the thruput fell drastically to about 90û gallons per minute.
2. Paper formation was poor. This was evidenced by the inability of the furnish to drain accompanied by the inability to put more refining on the furnish.
3. Poor drainage and increased energy consumption indicated a poor result. The paper sheet became wetter and the steam usage in the main dryer section increased by at least 15-20 psi.
4. first pass retention worsened as evidenced by increased solids in both the tray waters and the flotation save-all.
5. Machine speed was necessarily reduced by about 8-lû%.
It would then appear that the anionic com~ination of the anionic Polymer and dispersed silica most preferably occurs by sequentially adding to the paper stock from 10 to 50 pounds per ton of dried paper of the cationically modified starch, then adding the anionic polymer; followed thereafter by the dispersed silicas. Prior addition of dispersed silica to paper stock containing polymer does not apparently allow formation of the coacervate complex, and the results of binder use is destroyed.
All of the calculations indicating the aadition of any ingredient in terms of i~/T above refers to the pounds of active ingredients used per ton of dried paper.
It would then appear that the anionic com~ination of the anionic Polymer and dispersed silica most preferably occurs by sequentially adding to the paper stock from 10 to 50 pounds per ton of dried paper of the cationically modified starch, then adding the anionic polymer; followed thereafter by the dispersed silicas. Prior addition of dispersed silica to paper stock containing polymer does not apparently allow formation of the coacervate complex, and the results of binder use is destroyed.
All of the calculations indicating the aadition of any ingredient in terms of i~/T above refers to the pounds of active ingredients used per ton of dried paper.
Claims (17)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for making paper which process comprises admixing with paper-making stock, containing a sufficient amount of cellulosic pulp to give a finished paper containing at least 50 weight percent cellulosic fiber, from about 0.1 to 15% based on the weight of the pulp in the stock, of a coacer-vate binder wherein the coacervate binder comprises a cationic starch having a degree of substitution ranging between about 0.01 to about 0.20 in combination with an anionic combination of an anionic high molecular weight polymer having a molecular weight of at least 500,000 and a degree of anionic substitution of at least 0.01 and a dispersed silica having a particle size ranging from 1 to 50 nm; and wherein the weight ratio of anionic polymer to silica ranges from about 20:1 to about 1:10, and wherein the cationic starch to silica ratio is between about 100:1 to 1:1, and wherein said coacervate binder is admixed with the paper-making stock prior to formation of the paper.
2. The process of Claim 1 in which the ratio of cationic starch to anionic combination ranges from about 50:1 to about 5:1 and the weight ratio of anionic polymer to silica sol ranges from about 10:1 to about 1:1, and also wherein the degree of anionic substitution of the anionic polymer is at least 0.10, and the molecular weight of the anionic polymer is at least 1,000,000; the degree of cationic substitution on the cationic starch is from about 0.02 - 0.10; and the parti-cle size of the dispersed silica ranges from 2-25 nm.
3. The process of Claim 2 wherein the pH of the paper stock ranges from about 4 to about 9.
4. The process of Claim 3 wherein the degree of cationic substitution of starch ranges from about 0.015 to about 0.075 and the cationic starch is a cationically modified potato starch, and wherein the anionic polymer is from the group con-sisting of copolymers of acrylamide with monomers from the group consisting of acrylic acid, methacrylic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinyl sulfonate, sulfonate styrene and mixtures thereof, and modified acrylamide polymers contain-ing at least the sulfonate functional group.
5. The process of Claim 1 or 2, wherein the hinder is formed in situ by sequential addition to the paper-making stock of the cationic starch, then the anionic polymer, then the dis-persed silica; each addition occurring after each prior addi-tion has been thoroughly admixed with the paper-making stock.
6. The process of Claim 1 or 2, wherein the binder is formed in situ by a sequential addition to the paper-making stock of the cationic starch, followed then by an admixture of the silica sol and the anionic polymer; each addition occurring after each prior addition has been thoroughly admixed.
7. The process of Claim 1, which comprises additionally adding to the paper stock from 0.01 to 10.0 pounds of active alumina, Al2o3 per ton of dried paper.
8. The process of Claim 7 wherein the active alumina is chosen from the group consisting of papermaker's alum, sodium aluminate, or polyhydroxyaluminum chloride.
9. A process for making paper which process comprises adding a binder to an aqueous paper-making stock, containing a sufficient amount of cellulosic pulp to give a finished paper having at least 50 weight percent cellulosic fiber, the cellu-losic pulp having dispersed therein a mineral filler wherein the mineral filler material has at least partial anionic sur-face characteristics and the binder is a coacervate binder consisting of a cationically modified potato starch having a degree of cationic substitution ranging from about 0.01 to 0.15 in combination with an anionic polymer having a molecular weight of at least 1,000,000 and a degree of anionic substitution ranging from about 0.05 to about 0.95, and further in combination with a dispersed silica having a particle size ranging from about 1 nm to about 50 nm, wherein the cationic starch to silica ratio is from about 100:1 to about 30:1; the anionic combination has a weight ratio of polymer:si-lica ranging from about 20:1 to about 1:1, and further wherein the total coacervate binder to mine-ral filler weight ratio, on a solids basis, is from about 0.005:1 to about 1:1, and further wherein said binder is formed by admixing with the paper-making stock, prior to formation of the paper, in sequence, the cationic starch, the anionic polymer, and then the dispersed silica.
10. The process of Claim 9 wherein the pH of the paper-making stock ranges from about 4 to about 9.
11. The process of Claim 9 wherein the weight ratio of cationically modified potato starch to the anionic combination of anionic polymer and dispersed silica is from about 50:1 to about 1:1 and the weight ratio of cationic starch to silica is from about 75:1 to about 30:1, and further wherein the binder, on a solids level, is added to said paper-making stock at levels ranging from about 0.05 to about 10 weight percent of said paper-making stock.
12. The process of Claim 11 wherein the ratio of cellulo-sic fibers to mineral filler ranges from about 100:1 to about 1:1 and wherein the ratio of cellulosic fibers to binder is about 200:1 to about 20:1, and wherein the silica particles have a particle size ranging from 1.0 to about 10 nm, the anionic polymer has a molecular weight of at least 5,000,000 and a degree of anionic substitution ranging from about 0.05 to about 0.50 and wherein the potato starch contains a degree of cationic substitution ranging from about 0.01 to about 0.10.
13. The process of Claim 11 which comprises additionally adding to the paper stock from 0.01 to 10.0 pounds of active alumina per ton of dried paper wherein the active alumina is chosen from the group consisting of papermaker's alum, sodium aluminate, polyhydroxyaluminum chloride and mixtures thereof.
14. A coacervate binder for use in a paper-making process using a cellulosic pulp containing at least 50 weight percent cellulose which comprises in combination:
A. from 50-90 weight percent of a cationic potato starch having a degree of cationic substitution ranging from 0.010 to about 0.150;
B. from 10-40 weight percent of an anionic polymer having a molecular weight of at least 500,000, and a degree to anionic substitution ranging between about 0.01 to 1.0; and C. from about 0.1 to 5 weight percent of a dispel-sed silica having a particle size ranging bet-ween about 1 to 50 nm.
A. from 50-90 weight percent of a cationic potato starch having a degree of cationic substitution ranging from 0.010 to about 0.150;
B. from 10-40 weight percent of an anionic polymer having a molecular weight of at least 500,000, and a degree to anionic substitution ranging between about 0.01 to 1.0; and C. from about 0.1 to 5 weight percent of a dispel-sed silica having a particle size ranging bet-ween about 1 to 50 nm.
15. The coacervate binder of Claim 11, wherein the weight ratio of cationic starch to silica ranges from 50:1 to 30:1.
16. The coacervate binder of Claim 14 which additionally contains from 0.01 to 2.0 weight percent of active alumina.
17. A paper product when prepared by the process of claim 1 or 9.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/832,557 US4643801A (en) | 1986-02-24 | 1986-02-24 | Papermaking aid |
| US832,557 | 1986-02-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1266730A true CA1266730A (en) | 1990-03-13 |
Family
ID=25262007
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000527099A Expired - Lifetime CA1266730A (en) | 1986-02-24 | 1987-01-12 | Papermaking aid |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4643801A (en) |
| CA (1) | CA1266730A (en) |
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- 1986-02-24 US US06/832,557 patent/US4643801A/en not_active Expired - Lifetime
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Also Published As
| Publication number | Publication date |
|---|---|
| US4643801A (en) | 1987-02-17 |
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