CA1187253A - Paper making process utilizing an amphoteric mucous structure as binder - Google Patents
Paper making process utilizing an amphoteric mucous structure as binderInfo
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- CA1187253A CA1187253A CA000398502A CA398502A CA1187253A CA 1187253 A CA1187253 A CA 1187253A CA 000398502 A CA000398502 A CA 000398502A CA 398502 A CA398502 A CA 398502A CA 1187253 A CA1187253 A CA 1187253A
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Abstract
ABSTRACT OF THE DISCLOSURE:
The present invention refers to a paper making process with improved retention and binding of fillers and second grade fibers. It is characterized by the use of an amphoteric mucus like compound as binder. This compound is the reaction product between cationic starch of low charge density and an anionic polymer of high charge density as carboxymethyl cellulose. The compound has amphoteric and mucous characters and should be used for paper making, while in a unique transient structure. This structure is characterized by filler particles being enclosed and finely distributed in droplets of the highly hydrated but substantially water-insoluble mucous compound.
According to the invention this transient structure may further be reorganized to a less hydrated and more resist-ant gel structure, still enclosing the filler. This gel structure can stand the draining forces on a paper machine wire. This structural reorganization is achieved by reac-tion with colloidal inorganic polymers of very high surface charge as polysilicic acid and polyaluminium compounds.
The process yields papers of high strengths and filler retentions of more than 90% at a single wire passage even at extreme filler contents of 30-60% of the paper weight.
The present invention refers to a paper making process with improved retention and binding of fillers and second grade fibers. It is characterized by the use of an amphoteric mucus like compound as binder. This compound is the reaction product between cationic starch of low charge density and an anionic polymer of high charge density as carboxymethyl cellulose. The compound has amphoteric and mucous characters and should be used for paper making, while in a unique transient structure. This structure is characterized by filler particles being enclosed and finely distributed in droplets of the highly hydrated but substantially water-insoluble mucous compound.
According to the invention this transient structure may further be reorganized to a less hydrated and more resist-ant gel structure, still enclosing the filler. This gel structure can stand the draining forces on a paper machine wire. This structural reorganization is achieved by reac-tion with colloidal inorganic polymers of very high surface charge as polysilicic acid and polyaluminium compounds.
The process yields papers of high strengths and filler retentions of more than 90% at a single wire passage even at extreme filler contents of 30-60% of the paper weight.
Description
7'~
.
The inven~ion refers to a paper making process, and is based on the use of a new amphoteric compound as binder for fillers and second grade fibers. This compound is obtained by reaction of cationic starch of Iow charge density with linear polyanionic polymers of high charge density as carboxyme~hyl cellulose and polyacrylic acid. By this reaction a complex organized structure is formed, which chemically is related to certain biologi-cal mucus polysaccharide structures-lt is able to reorganize itself to efficientand mechanically strong envelope structures around filler particles and fibers, whereby it enables improved binding thereof in the final paper struc~ure. The invention is further based on the use of inorganic polymer colloids of strongly ionic character for final reorganization of the "rnucus envelope" to a mechanically stron~ structure that can withstand the heavy draining forces on the paper machine wire. The process can be utilized in regular paper makin~ and yields very high retention and very hi~h paper strengths at extreme high filler contents of 30-60% of the paper weight.
Cationic s~arches have been used since long in the paper industry7 but in small percentages of û,2-1,0% on paper weight. According ~o ~he present invention, the amount of cationic starch used for paper making can be increased ~o between 3 and 10% without any process troubles. Star-ches containing both cationic and anionic groups have earJier been proposed as binders in paper, and so have mixtures of ca~ionic and anionic starches.
The proposed systems refer, however, to anionic starches of low charge density or DS (degree of substitution) of 0,01-0~10 which is of the same , ' ~.
order as DS of commercial cationic starches 0,015-0,050.
According to our investigations, such starches and starch con~inations will give a much inferior result compared with the present in~ention, and they can not give the organized structure of a mucous filler-envelope, which is character-istic for this invention.
Accordlngly, the present invention relates to a paper manufacturing process, characterized by the step of:
a) preparing an amphoteric mucus like composition by reacting lO0 parts by weight of a cationic starch with a low degree of substitution of 0,02-0,10 in a waterswollen state with 1-8 parts by weight of an anionic linear (non-starch) polymer with a high degree of substitution of 0,5-l,0 to a hydrated but substantially insoluble mucus composi-tion, suspended in water - the primary structure;
b) preparing a mucus coated structure of fillers and/or cellulosic fibers by mixing a slurry of fillers and/
or fibers with the water suspended composition according to a) - the secondary structure;
c) reorganizing the mucus coating according to b) to a less hydrated and mechanically resistant gel coating by adding a colloidal solution of polymer micro-particles consisting of polysilicic acid with 5-50 SiO2-units per polymer or of a polyaluminium-oxi-compound (basic Al-compound), in which the Al-valencies are partly neutralized and replaces by oxi bridges (-O- groups) - the tertial structure; and d) processing the obtained gel coated filler/
fiber structure according to c) as a paper making furnish or part thereof.
~ The DS (degree of substitution) of trade mark cationic starches (CS) are very low, mostly 0,015 to 0,050, which means that l,5 resp. 5% of the glucose units are substituted with amino groups, mostly ~uaternary amino - 2a -groups.
We have obtained the best results with cationic starches (CS) of highest possible molecular weight (100.000-500.000) and a DS of 0,025-0,050 preferably 0,030-0,035, corresponding to EW (equivalent weight) of about 6.000.
Trade mark carboxymethyl celluloses (CMC) are also available in various MW and DS. Their DS is mostly very high and way vary between 0,40 and 0,90, and we have found the higher DS of 0,60-0,90, preferably 0,70-0,80 best suited for the invention, which corresponds to an EW of around 300. A DS below 0,10 is here called low (low charge density) and above 0,50 ahigh. Further a medium MW of 50,000-300,000, corresponding to a Brookfield viscosity of 20-300 cps in 2% solutions are to be prefered, even i CMC grades outside these limits also can be used.
If one prepares a mixture of CS (EW 6.000) and CMC (EW 300) in a 2-3% water solution and in equivalent amounts, that is 5 parts of CMC per 100 parts of CS, one gets a somewhat turbid low viscosity solution. On standing a precipitate of CS-CMC slowly separates. Such a product can be used for the invention, but it is not the most efficient product that can be obtained. For the most efficient product only about half the amount of CMC or 2-3 parts per 100 CS has to be used, and this CMC should prefer-ably be predissolved cold in the water in which the CS has to be swollen and adissolved. The technically recommended process for dissolving CS by direct steam injection during prolonged time in order to get a ~molecular solution free of structural agglomerates should in fact be avoided. As ~'7~3 said, the most efficient structure of the CS-CMC reaction product is obtai-ned when the reaction product is formed already during swelling and solubi-lization of the starch ~rains. l echnically it is of advantage to utilize a dry mixture of CS with 2-3 parts of CMC as Na-salt. When mixed with cold water the CMC component then dissolves without formation of CMC-lumps, which otherwise causes difficulties. The CS starts to swell at 50-60C
under formation of a specific structure with ChlC. Cooking of the formed structure at 90-100 shoul~i be prolonged for 10 minutes9 but contrary to pure CS it does not change character during prolonged cooking. The resulting solution is somewhat turbid and of much lower viscosity than only CS at the same concentration. The solution can be made in a concentration of ~-5% CS.
The optimal ratio of CS to CMC or any other anionic polymer is not related ~o any equivalency point or to any fixed relation between anionic and cationic ratio. Of importance is the organi~ation of anionic and cationic areas inside the mucous structure obtained. This optimal ratio must be settled by tests for evry CS - anionic polymer combination. For the natural alginic acid with DS=l,0 the optimal ratio is the same as for CMC with DS=0,7 or 2-3 parts per 100 parts of CS. For polyacrylic acid also with DS= 1,0 (but with smaller units than glucose) the optimal weight ratio is around 195 parts per 100 parts of CS. With too low polyacid content (below CMC/CS-0,5/100) the final mucous structure including filler is too weak mechanically and inadequate to final binding the pigment in the paper. With too high polyacid content the structure will resist combination with fillers.
Plyacid/CS ratios above 10/100 are hardly useful, while practical limits are 1-8/100 CS.
As already indicated, alginic acid from sea-weed and polyacrylic acid can b~ used as reactants with CS, but CMC seems at present to be the most economic reactant. Also a low molecuiar polyacid like citric acid has a minor but inadequate effect9 when used accordin~ to the invention.
It can be used in polyacid combinations. Of special interest are oligomer silicic acids, which àlso react with CS to mucus-like compounds of amphote-ric character. If commercial waterglass of ratio SiO2/Na20=3,3/1 is added to the water in which CS is ~oing to be dissolved in an optimai amount of
.
The inven~ion refers to a paper making process, and is based on the use of a new amphoteric compound as binder for fillers and second grade fibers. This compound is obtained by reaction of cationic starch of Iow charge density with linear polyanionic polymers of high charge density as carboxyme~hyl cellulose and polyacrylic acid. By this reaction a complex organized structure is formed, which chemically is related to certain biologi-cal mucus polysaccharide structures-lt is able to reorganize itself to efficientand mechanically strong envelope structures around filler particles and fibers, whereby it enables improved binding thereof in the final paper struc~ure. The invention is further based on the use of inorganic polymer colloids of strongly ionic character for final reorganization of the "rnucus envelope" to a mechanically stron~ structure that can withstand the heavy draining forces on the paper machine wire. The process can be utilized in regular paper makin~ and yields very high retention and very hi~h paper strengths at extreme high filler contents of 30-60% of the paper weight.
Cationic s~arches have been used since long in the paper industry7 but in small percentages of û,2-1,0% on paper weight. According ~o ~he present invention, the amount of cationic starch used for paper making can be increased ~o between 3 and 10% without any process troubles. Star-ches containing both cationic and anionic groups have earJier been proposed as binders in paper, and so have mixtures of ca~ionic and anionic starches.
The proposed systems refer, however, to anionic starches of low charge density or DS (degree of substitution) of 0,01-0~10 which is of the same , ' ~.
order as DS of commercial cationic starches 0,015-0,050.
According to our investigations, such starches and starch con~inations will give a much inferior result compared with the present in~ention, and they can not give the organized structure of a mucous filler-envelope, which is character-istic for this invention.
Accordlngly, the present invention relates to a paper manufacturing process, characterized by the step of:
a) preparing an amphoteric mucus like composition by reacting lO0 parts by weight of a cationic starch with a low degree of substitution of 0,02-0,10 in a waterswollen state with 1-8 parts by weight of an anionic linear (non-starch) polymer with a high degree of substitution of 0,5-l,0 to a hydrated but substantially insoluble mucus composi-tion, suspended in water - the primary structure;
b) preparing a mucus coated structure of fillers and/or cellulosic fibers by mixing a slurry of fillers and/
or fibers with the water suspended composition according to a) - the secondary structure;
c) reorganizing the mucus coating according to b) to a less hydrated and mechanically resistant gel coating by adding a colloidal solution of polymer micro-particles consisting of polysilicic acid with 5-50 SiO2-units per polymer or of a polyaluminium-oxi-compound (basic Al-compound), in which the Al-valencies are partly neutralized and replaces by oxi bridges (-O- groups) - the tertial structure; and d) processing the obtained gel coated filler/
fiber structure according to c) as a paper making furnish or part thereof.
~ The DS (degree of substitution) of trade mark cationic starches (CS) are very low, mostly 0,015 to 0,050, which means that l,5 resp. 5% of the glucose units are substituted with amino groups, mostly ~uaternary amino - 2a -groups.
We have obtained the best results with cationic starches (CS) of highest possible molecular weight (100.000-500.000) and a DS of 0,025-0,050 preferably 0,030-0,035, corresponding to EW (equivalent weight) of about 6.000.
Trade mark carboxymethyl celluloses (CMC) are also available in various MW and DS. Their DS is mostly very high and way vary between 0,40 and 0,90, and we have found the higher DS of 0,60-0,90, preferably 0,70-0,80 best suited for the invention, which corresponds to an EW of around 300. A DS below 0,10 is here called low (low charge density) and above 0,50 ahigh. Further a medium MW of 50,000-300,000, corresponding to a Brookfield viscosity of 20-300 cps in 2% solutions are to be prefered, even i CMC grades outside these limits also can be used.
If one prepares a mixture of CS (EW 6.000) and CMC (EW 300) in a 2-3% water solution and in equivalent amounts, that is 5 parts of CMC per 100 parts of CS, one gets a somewhat turbid low viscosity solution. On standing a precipitate of CS-CMC slowly separates. Such a product can be used for the invention, but it is not the most efficient product that can be obtained. For the most efficient product only about half the amount of CMC or 2-3 parts per 100 CS has to be used, and this CMC should prefer-ably be predissolved cold in the water in which the CS has to be swollen and adissolved. The technically recommended process for dissolving CS by direct steam injection during prolonged time in order to get a ~molecular solution free of structural agglomerates should in fact be avoided. As ~'7~3 said, the most efficient structure of the CS-CMC reaction product is obtai-ned when the reaction product is formed already during swelling and solubi-lization of the starch ~rains. l echnically it is of advantage to utilize a dry mixture of CS with 2-3 parts of CMC as Na-salt. When mixed with cold water the CMC component then dissolves without formation of CMC-lumps, which otherwise causes difficulties. The CS starts to swell at 50-60C
under formation of a specific structure with ChlC. Cooking of the formed structure at 90-100 shoul~i be prolonged for 10 minutes9 but contrary to pure CS it does not change character during prolonged cooking. The resulting solution is somewhat turbid and of much lower viscosity than only CS at the same concentration. The solution can be made in a concentration of ~-5% CS.
The optimal ratio of CS to CMC or any other anionic polymer is not related ~o any equivalency point or to any fixed relation between anionic and cationic ratio. Of importance is the organi~ation of anionic and cationic areas inside the mucous structure obtained. This optimal ratio must be settled by tests for evry CS - anionic polymer combination. For the natural alginic acid with DS=l,0 the optimal ratio is the same as for CMC with DS=0,7 or 2-3 parts per 100 parts of CS. For polyacrylic acid also with DS= 1,0 (but with smaller units than glucose) the optimal weight ratio is around 195 parts per 100 parts of CS. With too low polyacid content (below CMC/CS-0,5/100) the final mucous structure including filler is too weak mechanically and inadequate to final binding the pigment in the paper. With too high polyacid content the structure will resist combination with fillers.
Plyacid/CS ratios above 10/100 are hardly useful, while practical limits are 1-8/100 CS.
As already indicated, alginic acid from sea-weed and polyacrylic acid can b~ used as reactants with CS, but CMC seems at present to be the most economic reactant. Also a low molecuiar polyacid like citric acid has a minor but inadequate effect9 when used accordin~ to the invention.
It can be used in polyacid combinations. Of special interest are oligomer silicic acids, which àlso react with CS to mucus-like compounds of amphote-ric character. If commercial waterglass of ratio SiO2/Na20=3,3/1 is added to the water in which CS is ~oing to be dissolved in an optimai amount of
2-6% SiO2 on weight of CS, first white voluminous starch-silicic-acid-precipitates are formed when CS starts to swell. After cooking a mucous dispersion is obtained, similar to that with CMC, but of higher viscosity.
Commercial ~vaterglass corresponds to di-sodium-sa)ts of linear tri- and tetra-silicic acid, bue it is supposed that these acids polymerize further and Jinearly during reaction with CS. If di-sodium salt of penta-silicic acid is used as reactant with CS a much more rigid gel structure of high and complex viscosity is obtained. For preparation of the mucous structure at this stage of the process, hence, silicic acid oligomers with maximum ~ SiO2 should be used. Three dimensional polymers of above 4 SiO2 should be used for the final reorganization or curing of the mucus structure to a resistant gel structure. A suitable way of utilizing the cheap waterglass for the invention is to divide the addition in two steps or to combine it with small amounts of CMC. CS is then swollen and dissolved together with 1-2 parts of CMC or SiO2 and at a lower temperature a diluted waterglass is added in an amount corresponding to 1-4% SiO2 on CS. This latter addition can be made together with the addition of filler-suspension or even after it.
The chemical structure obtained by reacting 2 parts CMC (DS 0,7 and MW 150.000) with 100 parts CS (DS 0,03 and MW 300.000) should likely be "a ionic bond coacervate" of one central CI~AC-unit surrounded by 20-3G
cationic starch units. Such a structure should give a high viscosity. But the viscosity of the strucnlre Iormed is rather low, which indicates that the coacervates are collected in larger, denser and more rigid structures, proba-bly the original but swollen g rains of the CS with some enrichment of CMC on their surface. A swollen starch grain (potato starch) has a size of around 100 micron. The primary structure obtained by dissolving CS in a CMC-solution have some fur~her interesting properties.
1. Contrary to pure CS, the structure shows a stable viscosity during pro-longed cooking and this viscosi~y is surprisingly low already after completed swellin~. The external water phase contains no dissolved starch when separated and analyzed. The resulting produc~ is, conse~uen-tly, not a real solution but a suspension of a substantially insoluble mucus compound, a coacervate of anionic-cationic polyelectrolytes.
Commercial ~vaterglass corresponds to di-sodium-sa)ts of linear tri- and tetra-silicic acid, bue it is supposed that these acids polymerize further and Jinearly during reaction with CS. If di-sodium salt of penta-silicic acid is used as reactant with CS a much more rigid gel structure of high and complex viscosity is obtained. For preparation of the mucous structure at this stage of the process, hence, silicic acid oligomers with maximum ~ SiO2 should be used. Three dimensional polymers of above 4 SiO2 should be used for the final reorganization or curing of the mucus structure to a resistant gel structure. A suitable way of utilizing the cheap waterglass for the invention is to divide the addition in two steps or to combine it with small amounts of CMC. CS is then swollen and dissolved together with 1-2 parts of CMC or SiO2 and at a lower temperature a diluted waterglass is added in an amount corresponding to 1-4% SiO2 on CS. This latter addition can be made together with the addition of filler-suspension or even after it.
The chemical structure obtained by reacting 2 parts CMC (DS 0,7 and MW 150.000) with 100 parts CS (DS 0,03 and MW 300.000) should likely be "a ionic bond coacervate" of one central CI~AC-unit surrounded by 20-3G
cationic starch units. Such a structure should give a high viscosity. But the viscosity of the strucnlre Iormed is rather low, which indicates that the coacervates are collected in larger, denser and more rigid structures, proba-bly the original but swollen g rains of the CS with some enrichment of CMC on their surface. A swollen starch grain (potato starch) has a size of around 100 micron. The primary structure obtained by dissolving CS in a CMC-solution have some fur~her interesting properties.
1. Contrary to pure CS, the structure shows a stable viscosity during pro-longed cooking and this viscosi~y is surprisingly low already after completed swellin~. The external water phase contains no dissolved starch when separated and analyzed. The resulting produc~ is, conse~uen-tly, not a real solution but a suspension of a substantially insoluble mucus compound, a coacervate of anionic-cationic polyelectrolytes.
3~
2. The external water and the internal mucus structure mostly show a dif ference ~f pH that can be maintained during several days until the structure looses viscosity and collapses. This difference has its origin in the fact that CMC, or any other polyacid used, is aclded as a slightly alkaline salt (pH 7-9) while CS mostly is neutral ~pH 6-7), but it is surprising that the primary structure formed- has a "membra-ne-effect" that can be kept for so long time. When a pH-paper strip is dipped in the CS-CMC-solution it shows the external pH of 8-9. When the strip with adhered mucus structure is squeezed- or rubbed between fingers, the pH decreases to 7 in connection with collapse of she structu-re. Thus, the structure is transient-instable.
3. When the reaction product of CS and CMC (or any other polyacid) is brought in contact with a slurry of filler (as kaolin or chalk) the mucous structure is reorganized while it combines with the filler particles. The reorganization yields a new secondary structure of filler particles finely enclosed by an envelope of mucus in small spherical droplets.
This reorganization is accompanied by a strong increase of viscosity and an equalization of the pH gradient described above. The droplets of mucus enclosing the filler (the secondary structure) easily agglo-merate and separate from the external water, which still contains no substantial amounts of dissolved CS or CMC.
The mixing of the primary mucus composition with filler slurry can be performed cold or with a still hot CS-CMC product. pH is not important and may vary between 5 and 9, depending on filler (kaolin-acidic and chalk--alkaline). A suitable ratio of C~-CMC to fillèr is 10% but the amount of CS-CMC-binder can vary between ~ and 20% of the weight of filler.
An economical optimum is between 5 and 15%. If no filler or only small amounts of filler is to be used, an additlon of 1-~% of CS-CMC on weight of dry furnish is useful for compensating the lack of strength, accompanying second grade fibers. The concentration of the filler suspension may vary between 10 and 30%, and the concentration of the CS-CMC compound may vary between 7 and 4%. Higher concentrations may ~ive lumps of filler with inadequate contact with the CS-CMC-binder. Such lumps will give a "dotty" and dusty paper with low surface strength. Lower concentra-'7~
tions may be used, but result in lower stren~ths o~ the final paper. Thus, ifthe secondary mucus structure is formed in high dilution, also the secondary mucus structure will be "diluted'i and weakened. The secondary structure is likely composed of filler particles finely enclosed in droplets of CS-CMC-mucus. The building blocks of this mucus should be coacervates of one anionic CMC-unit (or the polyacid used) in a central position, surrounded by 20-30 cationic CS-molecules, kept ~ogether by ionic forces between CS and CMC, and extensively hydrated. The peripheral CS branches of this agglome-rate will bind by ionic bonds to the slightly anionic filler particles and cover them by an envelope. The filler particles have a size of 1-10 microns, while the mucous unit block should be less than one micron but linked ~ogether with other blocks by other CMC-units to a giant mucus molecule extending over whole the droplet. A surprising property of this secondary structure is ~hat the droplets can agglomerate to large dough lumps in a reversible way, allowing separation by filtering and even an extensive drying before redespersion to a useful paper furnish with good formation properties.
Simple ionic bonds in polyeloctrolytes are not strong nor stable. In biological mucopolysaccharides, stability is obtained by a l)S-I of glucose-amines and-acids, o~ten reinforced by protein-crosslinking. The secondary structure is accordingly not stable. It slowly reorganizes to less viscouse structures and finally fades away while the filler particles are redispersed to the external water phase. The secondary structure is also transient and must be used before 24 to 48 hours after preparation. Especially chalk loaded structures are sensitive to aging, probably depending on a slow forma-tion of Ca-ionst which react with CMC and thereby weakens the CS-CMC-bonds. Also thc primary CS-CMC mucus without filler is transient. It has the highest absorption power for fillers when newly prepared~ but it is still useful after 24-48 hours.
The role of CMC ~or any other polyacid3 can be expressed as follows.
A cationic-anionic starch mixture will not give these features unless the anionic part has a high DS and is decomposed to shor~ linear molecules.
1. It binds CS to giant, hydrated but substantially insoluble mucus coa-cervates.
'7~3 . It contributes to a high ionic and surface activity of these coacervates, whereby they are able to enclose the filler efficiently and in a highJy dispersed form.
. It contributes to improved mechanical resistancy of the mucus structure, also when this has been reorgani~ed to a gel in the following step of the process.
. 1t finally contributes to a much more efficient binding of the filler in the final paper than any starch combination can do.
The secondary structure o~ encapsulated fillers in droplets of CS-CMC-mucus may seem stable at a laboratory test~ but in most cases it is not enou~h strong mechanically to withstand the intensive forces of draining at ~he wire of a fast running paper machine. Anyhow it will not be strong enough to give the desired filler retention of 90-95% at one single passage oYer the wire. It is therefore of advantage to reorganize or "cure" the secondary mu c u s structure to a tertiary more resistant gel structure.
This can be done by a synerese reaction (dehydration) achieved by addition of small amounts of colloidal mainly inorganic polymers with very high surface charge. Such inorganic polymers of anionic character are poly-silicic acids with S-50 SiO2-units per molecule, while certain polyaluminium componds are examples of suitable cationic polymers. Finally complex polyaluminium-citrate-sulfate compounds, corresponding to a formula A 1 4(OH)8Ci22 5042 (Ci= a citric acid equivalent), seem to be amphoteric polymers with ~oth anionic and cationic surface charges, which are very eff icient.
The first reorganization of the mucus structure is attained by coarse filler particles (I-lO micron~ with a rather weak surface charge, while the second reorganization is at~ained by colloidal particles (I-lO millimicrons)with a very high surface charge. The principle reactions are in both cases the same, a ionic binding of glucose chains (starch chains) to the surface of particles. The second reaction is much more intensive, however, resulting in the formation of more dense and dehydrated mucus or gel droplets with increased tendency to irreversible agglomera~ion, that can stand the draining f orces.
~'7~3 The second reaction with colloidal inorganic polymers may be per~ormed before any cellulosic fibers have been mixed into the furnish.
It may also be performed after mixing with cellulose fibers, but then allowed to have a reaction time of 10-60 seconds before diluted with backwater at the paper machine. The synerese reaction of the secondary mucous structure to the tertiary gel structure is fast but not spontanous. It is also possible to divide this second reaction in two steps, one part before mi~ing with cellulosic furnish and another part after. The latter may be advisable, if ground wood fibers are going to be used, because wood fibers are contaminated with anionic and lipid compounds that interfere with the reaction. If the reaction is divided in two steps, it is further advisable to use a polyaluminium compound at the first step and a polysilicic acid compound in the second, or the reverse.
The amount of inorganic, col!oidal polymers, required, are rather low, below 10%, mostly between I and 5% of the starch content, which means 0,1-0,59~ of the filler weight, calculated as SiO2 or A1203. In most cases 0,1-0,3% is sufficient if the secondary structure is well developed and not aged more than some hours. If the secondary structure is weakend by age or by too high content of polyacid or "poisoned" by ionic and lipid contaminants, a primary curing should be made with an poly-AI-complex and a secondary curing with a silicic acid polymer.
The fiber component of the furnish may consist of kraft sulfate or sulphite fibers, preferably refined to a somewhat higher degree than normaly used for the type of paper concerned. It can also consist of ground wocd fibers. According to the invention a very high filler content of 30-60% of the paper weight can be used without substantial loss of strength and other important properties, which is shown in the following e~amples.
It is obvious that the invention can be practised also in other ways than described as optimal above. For instance, the cationic starch may be swollen in pure water to a certain degree and without prolonged cooking, whereupon the anionic polyacid is added. Such a proceeding is suitable for laboratory purposes but difficult to keep within reproducible limiCs in an industrial scale with large volumes. Other fillers can be usèd for 31 31 ~r7;~5~3 g instance talc, titaniumdioxide etc. but kaolin and chalk (limestone-powder) are ~he most common and most economical. A combinaison of kaolin and chalk has the advantage of keeping the furnish pH constant at around 7, where curing action is most efficient.
Rosin sizing and other sizing e.g. with AquapelR for rendering the paper water-resistent do not influence disadvantageous on the process, if these chemicals are added to the ~iber furnish before mixing with the furnish of mucus enveloped filler. Again, it is of advantage to arrange for the formation of the tertiary structure of starch-polyacid-~iller in absence of other anionic, cationic and lipid contaminations.
Cationized starches of various ori~ins can be used as corn, tapioca, wheat etc. but at least in Europe potato starch are prefered due to low price and suitable types of starch grains. Also other polyacids than carboxy-lic and siJicic acids can be used as synthetic sulfonic acids and phosphorous acids but of linear type, plus various acid combinations.
Example 1.
20 ~ of chalk with average particle size of 4 micron was slurried in water to a 25% slurry. Further an amphoteric mucous dispersion of 2% concentra-tion was prepared in the following way. 2g of a high viscosity cationic starch ~CS) was dispersed in cold water ~lOOml) in which had been dissolved 0,05g CMC or 2,5 parts CMC per 100 parts CS. The cationic starch (Perfec-tamyl PW ) had a DS of 0,033~ while the CMC-product (7LF from Hercules Corp.) had a DS o 0,70 and a low-medium moiecular weight. Thjs i5 a very pure product (food grade) which we used in laboratory tests in order to avoid contaminations. The mixture was swollen during mild agitation and cooked for 10 min. at 9~ when it yielded a lightly turbide and low viscoslty suspension.
The amphoteric mucus dispersion was added hot to the chalk slurry, thus, in an amount corresponding to lû96 CS and 0,2~% CMC on chalk weight.
The mixture got a finely agglomerated structure~ while ~he mucus-like composition enclosed the filler particles. After 10 min. a solution of hexasili-cic acid was added in an amount corresponding to 396 SiO2 on weight of CS
* ( trade mark ) '7~3 (and 0,3% on wei~ht of chalk). The a~lomeration turned to a coarser charac-ter of 1-3 mm lumps while the water phase turned totaly clear. The hexa-silicic acid had been prepared by diluting commercial water~lass (ratio 3,3) to a solution containing 2% SiO2 and then neutralizing half the alkali content by sulfuric acid, whereupon the siloxane polyrnerization was allowed to proceed during ~0 minutes before use.
?Og cellulose, bleached kraft, 6096 hardwood and 40% so~twood, and refined to 30SR was suspended in a turmix and mixed with 0,5~6 ~qua-pelR on weight of cellulose. Then the cured starch-mucus suspension was added to the cellulose under intensive agitation. The final furnish then had a composition corresponding to:
Cellulose 47,296 ~halk 47,2%
CS-C .~A C ~, 1 2%
SiO2 0, 1 3%
Aquapel 0,25% (emulsion) The furnish was divided in 10 parts and handsheets made with a grammage of lOOg/m2. The backwater was controlled and was found to be totally clear. The weight of the 10 handsheets were 42,20g compared with the dry solid weight of the furnish of 42,12g. The retention, consequen-tly, was 100~6 and the paper forma~ion very good.
The paper properties were: Tensil index 33 Nm/g O p a c i t y 9 6 %
Elongation 2,996 Bri~htness 77 %
Wax value 15 Example ~.
The same test was made as in example 1), only with the difference that the 2,5% ~::MC was replaced by 1,5% polyacrylic acid (Na-sal~. The retention value was also in this case close to 100%. Percentage figures for CMC
and acrylic acid refers to weight of cationic starch. The paper properties were : Tensil index 29 Nm/~ and Wax value 1~, according to Dennison.
~ ~'7~i3 1 ~
Exampie 3.
The same test was made as in example 1), only with the difference that the 2,59~ CMC was replaced by 2,5% alginic acid (DP=300). Then cellulose furnish with Aquapel was mixed into the filler-mucus-slurry. The resulting agglomeration was then very fine (no coarse lumps), and just before formation of the handsheets a polymer aluminium sulfate solution prepared by neutra-lization of I/3 of the acid content by NaOH was added in an amount corres-ponding to 0,2% A1203 on chalk bases (2% on starch bases). The resulting agglomeration was very fine with quite clear backwater. ~he paper formation was excellen~ and the calculated retention of filler 96%.
Tensil index: 32 Nm/g Wax value: lS.
Example 4.
20g kaolin (dry) English grade E with an average particle size of 2-5 ~J
were slurried in water to a 25% slurry. To this slurry was added the same amphoteric CS-CMC composition an in example I (CMC/CS=2,5/100) in an amount corresponding to 10,25% on bases of kaolin. After encapsulation of ~he filler by mucus, 1,0% SiO2 as waterglass was added on base of the starch (0,1% on base of kaolin).
The same cellulose was used as in example 1, but without AquapelR
Filler/cellulose=l/l. After having mixed the kaolin suspension with the f iber furnish under moderate agitation, ~the fine a~glomerates does not need any Yiolent agitation for uniform distribution), a polymer Al-sulfate solution, neutralized to 33%, was added in an amount corresponding to 0,2% A1203 on the kaolin~ Again 10 handsheets with grammage lOOg/m2 was made and the calculated retention was 98%. The backwater showed only a very slight turbidity. In order ~o reach this retention ~he agglomerationhad to be improved by adjusting the pH of the furnish after Al-addition to 5,5. The hand sheets showed the following properties: Tensil inde~
~8 Nm/g, Elongation 2,2%, Wax value I I, ~pacity 98% and Brightness 75%.
Example 5.
20 8 kaolin (dry weight) grade E (2-5 micron) was slurried in bOg wa~er to which was added 0,2g common waterglass, corresponding to 0,25% SiO2 on kaolin weight. 2g CS (DS=0,035) was slurried in 50g water to which had been added another 0,2g waterglass (SiO2/Na20=393) and then heated and ~:~8'7~3 cooked durin~ 10 minutes. The hot and swollen starch suspension was added to the kaolin slurry under formation of a high visgous slurry of mucous dro-plets with enclosed kaolin. The ratio Siû2/CS was 5/100 of the formed mucus-filler structure. After 30 min it was added a further 2 parts of SiO2/100 CS, but now as "hexasilicic acid" (waterglass in which 50% of the alkali had been neutralized with sulfuric acid in diluted solution durinK
60 min.). This resulted in separation of mucus-filler-agglomerates which changed to more rigid gel agglomerates separated from a clear water-phase.
To this ag~lomerated gel structure was added a furnish of 20g cellulose (as in ex. 1, but with sulfate rosin as hydrophobic agent in stead of AquapelR). Upon efficient agitation, the agglomerates were dispersed and paper sheets were formed after neutralizing the alkalin furni~h with polyaluminiumsulfate (1/3 neutralized~ to a furnish pH of 5,8. The retention was estimated to 98% yielding a paper of 50% filler. Tensil index was 29Nm/g and Dennison wax pick up 13.
~xample 6 This example is presented in order to show the effect of the amphoteric CS-CMC~binder on a cellulose paper without filler. First a standard paper was produced from the cellulose of example I without any additions neither of filler nor of starch binder. The retention was anyhow above 97% and the pure cellulose paper showed a tensil index of 57 Nm/g and a wax value of only 13.
Secondly a paper was produced of cellulose without any filler but with 5% amphoteric CS-CMC-composition on cellulose bases. The ampho-teric composition was the same as in e~ample 1 CMC/CS = 2,5/100. ~efore the handsheet forming the cellulose-starch furnish was supplied with 0,15%
A1203 as a polymeric Al-sulfate (neutralized to 339~), calculated on the dry weight of cellulose. The retention was in this case slightly above 100%
including the starch and curing components. The paper showed a tensil index of 62 Nm/g and a rearkable wax value of 23. This example shows that the ampho~eric CS-CMC-binder has the most profound effect on the "Z-strength" when applied to a furnish of only cellulose.
~'7~3 Example 7.
The following test was performed on an experimental paper machine. 50 k~
chalk (4 micron) was dispersed in water to a 25% slurry. Further a slurry of 5 kg CS (DS 0,035) was prepared in 100 liters of water containing 0,12 kg l~MC (DS 0,7) of a Swedish SCA-grade called FF20, with BrookfieJd visco-sity 20cps at 2~o conc. After 10 min. cooking the hot CS-CMC-product was diluted to 2,5% and added to the chalk-filler-slurry, yielding a filler-n ucus-slurry with 10% CS on chalk and 2,4 parts C,~lC per 100 parts CS.
lhe filler-mucus-slurry was then mixed with 50kg cellulose (50%
hardwood and 50% softwood, refined to 30SR) in a 4% consistency, and con~aining 0,4% Aquapel~ hydrophobing emulsion. The mixed furnish showed a very Iine ag~lomeration of mucus-filler-droplets together with the fibers.
To the mixed furnish was then added 1% A1203 on CS w. as a complex polyaluminium-citrate-sulfate-solution. This complex had been prepared by dissolving I mol Al-sulfate in 2 lit. water, adding 1/3 mol o~ citric acid, and finally adding 5-n NaOH during 3 hours corresponding to a neutralization of 5/6 of the sulfuric acid of the Al-sulfate. AEter this addition the furnish agglomerated furt ~er and a totally clear water phase was obtained. The furnish was allowed to stay over the night. The next day it was charged to the experimental paper machine during addition o~ 3~ Si02 on CS-weight as hexasilicic acid (disodiumsalt). The svlution of hexasilicic acid salt was prepared by dissolving precipitated and washed silicic acid in waterglass to a ratio Si02/Na?0=6,0. The hexasilicic acid was allowed to react with the furnish during 40 seconds before dilution with backwater.
The furnish was fast draining on the wire, and the machine worked without any problems or interruptions. The paper dried very fast and the filler retention was estimated to 91%.
~;rammage 75 g/m2 Gurley 13 s.
Density 780 kg/m3 ~obb 15 g/m2 Tens;l index ~ 33 kNm/kg Unger b. s./2 27 g/m2 Burst index 2,0 MN/kg Brightn. b s/s 77 %
Tear index ~ 5,5 Nm2/kg Opacity 92 %
~long. at break V~ 2,5 % Filler cont. 45 %
Dennison Wax both-sides/2 16
2. The external water and the internal mucus structure mostly show a dif ference ~f pH that can be maintained during several days until the structure looses viscosity and collapses. This difference has its origin in the fact that CMC, or any other polyacid used, is aclded as a slightly alkaline salt (pH 7-9) while CS mostly is neutral ~pH 6-7), but it is surprising that the primary structure formed- has a "membra-ne-effect" that can be kept for so long time. When a pH-paper strip is dipped in the CS-CMC-solution it shows the external pH of 8-9. When the strip with adhered mucus structure is squeezed- or rubbed between fingers, the pH decreases to 7 in connection with collapse of she structu-re. Thus, the structure is transient-instable.
3. When the reaction product of CS and CMC (or any other polyacid) is brought in contact with a slurry of filler (as kaolin or chalk) the mucous structure is reorganized while it combines with the filler particles. The reorganization yields a new secondary structure of filler particles finely enclosed by an envelope of mucus in small spherical droplets.
This reorganization is accompanied by a strong increase of viscosity and an equalization of the pH gradient described above. The droplets of mucus enclosing the filler (the secondary structure) easily agglo-merate and separate from the external water, which still contains no substantial amounts of dissolved CS or CMC.
The mixing of the primary mucus composition with filler slurry can be performed cold or with a still hot CS-CMC product. pH is not important and may vary between 5 and 9, depending on filler (kaolin-acidic and chalk--alkaline). A suitable ratio of C~-CMC to fillèr is 10% but the amount of CS-CMC-binder can vary between ~ and 20% of the weight of filler.
An economical optimum is between 5 and 15%. If no filler or only small amounts of filler is to be used, an additlon of 1-~% of CS-CMC on weight of dry furnish is useful for compensating the lack of strength, accompanying second grade fibers. The concentration of the filler suspension may vary between 10 and 30%, and the concentration of the CS-CMC compound may vary between 7 and 4%. Higher concentrations may ~ive lumps of filler with inadequate contact with the CS-CMC-binder. Such lumps will give a "dotty" and dusty paper with low surface strength. Lower concentra-'7~
tions may be used, but result in lower stren~ths o~ the final paper. Thus, ifthe secondary mucus structure is formed in high dilution, also the secondary mucus structure will be "diluted'i and weakened. The secondary structure is likely composed of filler particles finely enclosed in droplets of CS-CMC-mucus. The building blocks of this mucus should be coacervates of one anionic CMC-unit (or the polyacid used) in a central position, surrounded by 20-30 cationic CS-molecules, kept ~ogether by ionic forces between CS and CMC, and extensively hydrated. The peripheral CS branches of this agglome-rate will bind by ionic bonds to the slightly anionic filler particles and cover them by an envelope. The filler particles have a size of 1-10 microns, while the mucous unit block should be less than one micron but linked ~ogether with other blocks by other CMC-units to a giant mucus molecule extending over whole the droplet. A surprising property of this secondary structure is ~hat the droplets can agglomerate to large dough lumps in a reversible way, allowing separation by filtering and even an extensive drying before redespersion to a useful paper furnish with good formation properties.
Simple ionic bonds in polyeloctrolytes are not strong nor stable. In biological mucopolysaccharides, stability is obtained by a l)S-I of glucose-amines and-acids, o~ten reinforced by protein-crosslinking. The secondary structure is accordingly not stable. It slowly reorganizes to less viscouse structures and finally fades away while the filler particles are redispersed to the external water phase. The secondary structure is also transient and must be used before 24 to 48 hours after preparation. Especially chalk loaded structures are sensitive to aging, probably depending on a slow forma-tion of Ca-ionst which react with CMC and thereby weakens the CS-CMC-bonds. Also thc primary CS-CMC mucus without filler is transient. It has the highest absorption power for fillers when newly prepared~ but it is still useful after 24-48 hours.
The role of CMC ~or any other polyacid3 can be expressed as follows.
A cationic-anionic starch mixture will not give these features unless the anionic part has a high DS and is decomposed to shor~ linear molecules.
1. It binds CS to giant, hydrated but substantially insoluble mucus coa-cervates.
'7~3 . It contributes to a high ionic and surface activity of these coacervates, whereby they are able to enclose the filler efficiently and in a highJy dispersed form.
. It contributes to improved mechanical resistancy of the mucus structure, also when this has been reorgani~ed to a gel in the following step of the process.
. 1t finally contributes to a much more efficient binding of the filler in the final paper than any starch combination can do.
The secondary structure o~ encapsulated fillers in droplets of CS-CMC-mucus may seem stable at a laboratory test~ but in most cases it is not enou~h strong mechanically to withstand the intensive forces of draining at ~he wire of a fast running paper machine. Anyhow it will not be strong enough to give the desired filler retention of 90-95% at one single passage oYer the wire. It is therefore of advantage to reorganize or "cure" the secondary mu c u s structure to a tertiary more resistant gel structure.
This can be done by a synerese reaction (dehydration) achieved by addition of small amounts of colloidal mainly inorganic polymers with very high surface charge. Such inorganic polymers of anionic character are poly-silicic acids with S-50 SiO2-units per molecule, while certain polyaluminium componds are examples of suitable cationic polymers. Finally complex polyaluminium-citrate-sulfate compounds, corresponding to a formula A 1 4(OH)8Ci22 5042 (Ci= a citric acid equivalent), seem to be amphoteric polymers with ~oth anionic and cationic surface charges, which are very eff icient.
The first reorganization of the mucus structure is attained by coarse filler particles (I-lO micron~ with a rather weak surface charge, while the second reorganization is at~ained by colloidal particles (I-lO millimicrons)with a very high surface charge. The principle reactions are in both cases the same, a ionic binding of glucose chains (starch chains) to the surface of particles. The second reaction is much more intensive, however, resulting in the formation of more dense and dehydrated mucus or gel droplets with increased tendency to irreversible agglomera~ion, that can stand the draining f orces.
~'7~3 The second reaction with colloidal inorganic polymers may be per~ormed before any cellulosic fibers have been mixed into the furnish.
It may also be performed after mixing with cellulose fibers, but then allowed to have a reaction time of 10-60 seconds before diluted with backwater at the paper machine. The synerese reaction of the secondary mucous structure to the tertiary gel structure is fast but not spontanous. It is also possible to divide this second reaction in two steps, one part before mi~ing with cellulosic furnish and another part after. The latter may be advisable, if ground wood fibers are going to be used, because wood fibers are contaminated with anionic and lipid compounds that interfere with the reaction. If the reaction is divided in two steps, it is further advisable to use a polyaluminium compound at the first step and a polysilicic acid compound in the second, or the reverse.
The amount of inorganic, col!oidal polymers, required, are rather low, below 10%, mostly between I and 5% of the starch content, which means 0,1-0,59~ of the filler weight, calculated as SiO2 or A1203. In most cases 0,1-0,3% is sufficient if the secondary structure is well developed and not aged more than some hours. If the secondary structure is weakend by age or by too high content of polyacid or "poisoned" by ionic and lipid contaminants, a primary curing should be made with an poly-AI-complex and a secondary curing with a silicic acid polymer.
The fiber component of the furnish may consist of kraft sulfate or sulphite fibers, preferably refined to a somewhat higher degree than normaly used for the type of paper concerned. It can also consist of ground wocd fibers. According to the invention a very high filler content of 30-60% of the paper weight can be used without substantial loss of strength and other important properties, which is shown in the following e~amples.
It is obvious that the invention can be practised also in other ways than described as optimal above. For instance, the cationic starch may be swollen in pure water to a certain degree and without prolonged cooking, whereupon the anionic polyacid is added. Such a proceeding is suitable for laboratory purposes but difficult to keep within reproducible limiCs in an industrial scale with large volumes. Other fillers can be usèd for 31 31 ~r7;~5~3 g instance talc, titaniumdioxide etc. but kaolin and chalk (limestone-powder) are ~he most common and most economical. A combinaison of kaolin and chalk has the advantage of keeping the furnish pH constant at around 7, where curing action is most efficient.
Rosin sizing and other sizing e.g. with AquapelR for rendering the paper water-resistent do not influence disadvantageous on the process, if these chemicals are added to the ~iber furnish before mixing with the furnish of mucus enveloped filler. Again, it is of advantage to arrange for the formation of the tertiary structure of starch-polyacid-~iller in absence of other anionic, cationic and lipid contaminations.
Cationized starches of various ori~ins can be used as corn, tapioca, wheat etc. but at least in Europe potato starch are prefered due to low price and suitable types of starch grains. Also other polyacids than carboxy-lic and siJicic acids can be used as synthetic sulfonic acids and phosphorous acids but of linear type, plus various acid combinations.
Example 1.
20 ~ of chalk with average particle size of 4 micron was slurried in water to a 25% slurry. Further an amphoteric mucous dispersion of 2% concentra-tion was prepared in the following way. 2g of a high viscosity cationic starch ~CS) was dispersed in cold water ~lOOml) in which had been dissolved 0,05g CMC or 2,5 parts CMC per 100 parts CS. The cationic starch (Perfec-tamyl PW ) had a DS of 0,033~ while the CMC-product (7LF from Hercules Corp.) had a DS o 0,70 and a low-medium moiecular weight. Thjs i5 a very pure product (food grade) which we used in laboratory tests in order to avoid contaminations. The mixture was swollen during mild agitation and cooked for 10 min. at 9~ when it yielded a lightly turbide and low viscoslty suspension.
The amphoteric mucus dispersion was added hot to the chalk slurry, thus, in an amount corresponding to lû96 CS and 0,2~% CMC on chalk weight.
The mixture got a finely agglomerated structure~ while ~he mucus-like composition enclosed the filler particles. After 10 min. a solution of hexasili-cic acid was added in an amount corresponding to 396 SiO2 on weight of CS
* ( trade mark ) '7~3 (and 0,3% on wei~ht of chalk). The a~lomeration turned to a coarser charac-ter of 1-3 mm lumps while the water phase turned totaly clear. The hexa-silicic acid had been prepared by diluting commercial water~lass (ratio 3,3) to a solution containing 2% SiO2 and then neutralizing half the alkali content by sulfuric acid, whereupon the siloxane polyrnerization was allowed to proceed during ~0 minutes before use.
?Og cellulose, bleached kraft, 6096 hardwood and 40% so~twood, and refined to 30SR was suspended in a turmix and mixed with 0,5~6 ~qua-pelR on weight of cellulose. Then the cured starch-mucus suspension was added to the cellulose under intensive agitation. The final furnish then had a composition corresponding to:
Cellulose 47,296 ~halk 47,2%
CS-C .~A C ~, 1 2%
SiO2 0, 1 3%
Aquapel 0,25% (emulsion) The furnish was divided in 10 parts and handsheets made with a grammage of lOOg/m2. The backwater was controlled and was found to be totally clear. The weight of the 10 handsheets were 42,20g compared with the dry solid weight of the furnish of 42,12g. The retention, consequen-tly, was 100~6 and the paper forma~ion very good.
The paper properties were: Tensil index 33 Nm/g O p a c i t y 9 6 %
Elongation 2,996 Bri~htness 77 %
Wax value 15 Example ~.
The same test was made as in example 1), only with the difference that the 2,5% ~::MC was replaced by 1,5% polyacrylic acid (Na-sal~. The retention value was also in this case close to 100%. Percentage figures for CMC
and acrylic acid refers to weight of cationic starch. The paper properties were : Tensil index 29 Nm/~ and Wax value 1~, according to Dennison.
~ ~'7~i3 1 ~
Exampie 3.
The same test was made as in example 1), only with the difference that the 2,59~ CMC was replaced by 2,5% alginic acid (DP=300). Then cellulose furnish with Aquapel was mixed into the filler-mucus-slurry. The resulting agglomeration was then very fine (no coarse lumps), and just before formation of the handsheets a polymer aluminium sulfate solution prepared by neutra-lization of I/3 of the acid content by NaOH was added in an amount corres-ponding to 0,2% A1203 on chalk bases (2% on starch bases). The resulting agglomeration was very fine with quite clear backwater. ~he paper formation was excellen~ and the calculated retention of filler 96%.
Tensil index: 32 Nm/g Wax value: lS.
Example 4.
20g kaolin (dry) English grade E with an average particle size of 2-5 ~J
were slurried in water to a 25% slurry. To this slurry was added the same amphoteric CS-CMC composition an in example I (CMC/CS=2,5/100) in an amount corresponding to 10,25% on bases of kaolin. After encapsulation of ~he filler by mucus, 1,0% SiO2 as waterglass was added on base of the starch (0,1% on base of kaolin).
The same cellulose was used as in example 1, but without AquapelR
Filler/cellulose=l/l. After having mixed the kaolin suspension with the f iber furnish under moderate agitation, ~the fine a~glomerates does not need any Yiolent agitation for uniform distribution), a polymer Al-sulfate solution, neutralized to 33%, was added in an amount corresponding to 0,2% A1203 on the kaolin~ Again 10 handsheets with grammage lOOg/m2 was made and the calculated retention was 98%. The backwater showed only a very slight turbidity. In order ~o reach this retention ~he agglomerationhad to be improved by adjusting the pH of the furnish after Al-addition to 5,5. The hand sheets showed the following properties: Tensil inde~
~8 Nm/g, Elongation 2,2%, Wax value I I, ~pacity 98% and Brightness 75%.
Example 5.
20 8 kaolin (dry weight) grade E (2-5 micron) was slurried in bOg wa~er to which was added 0,2g common waterglass, corresponding to 0,25% SiO2 on kaolin weight. 2g CS (DS=0,035) was slurried in 50g water to which had been added another 0,2g waterglass (SiO2/Na20=393) and then heated and ~:~8'7~3 cooked durin~ 10 minutes. The hot and swollen starch suspension was added to the kaolin slurry under formation of a high visgous slurry of mucous dro-plets with enclosed kaolin. The ratio Siû2/CS was 5/100 of the formed mucus-filler structure. After 30 min it was added a further 2 parts of SiO2/100 CS, but now as "hexasilicic acid" (waterglass in which 50% of the alkali had been neutralized with sulfuric acid in diluted solution durinK
60 min.). This resulted in separation of mucus-filler-agglomerates which changed to more rigid gel agglomerates separated from a clear water-phase.
To this ag~lomerated gel structure was added a furnish of 20g cellulose (as in ex. 1, but with sulfate rosin as hydrophobic agent in stead of AquapelR). Upon efficient agitation, the agglomerates were dispersed and paper sheets were formed after neutralizing the alkalin furni~h with polyaluminiumsulfate (1/3 neutralized~ to a furnish pH of 5,8. The retention was estimated to 98% yielding a paper of 50% filler. Tensil index was 29Nm/g and Dennison wax pick up 13.
~xample 6 This example is presented in order to show the effect of the amphoteric CS-CMC~binder on a cellulose paper without filler. First a standard paper was produced from the cellulose of example I without any additions neither of filler nor of starch binder. The retention was anyhow above 97% and the pure cellulose paper showed a tensil index of 57 Nm/g and a wax value of only 13.
Secondly a paper was produced of cellulose without any filler but with 5% amphoteric CS-CMC-composition on cellulose bases. The ampho-teric composition was the same as in e~ample 1 CMC/CS = 2,5/100. ~efore the handsheet forming the cellulose-starch furnish was supplied with 0,15%
A1203 as a polymeric Al-sulfate (neutralized to 339~), calculated on the dry weight of cellulose. The retention was in this case slightly above 100%
including the starch and curing components. The paper showed a tensil index of 62 Nm/g and a rearkable wax value of 23. This example shows that the ampho~eric CS-CMC-binder has the most profound effect on the "Z-strength" when applied to a furnish of only cellulose.
~'7~3 Example 7.
The following test was performed on an experimental paper machine. 50 k~
chalk (4 micron) was dispersed in water to a 25% slurry. Further a slurry of 5 kg CS (DS 0,035) was prepared in 100 liters of water containing 0,12 kg l~MC (DS 0,7) of a Swedish SCA-grade called FF20, with BrookfieJd visco-sity 20cps at 2~o conc. After 10 min. cooking the hot CS-CMC-product was diluted to 2,5% and added to the chalk-filler-slurry, yielding a filler-n ucus-slurry with 10% CS on chalk and 2,4 parts C,~lC per 100 parts CS.
lhe filler-mucus-slurry was then mixed with 50kg cellulose (50%
hardwood and 50% softwood, refined to 30SR) in a 4% consistency, and con~aining 0,4% Aquapel~ hydrophobing emulsion. The mixed furnish showed a very Iine ag~lomeration of mucus-filler-droplets together with the fibers.
To the mixed furnish was then added 1% A1203 on CS w. as a complex polyaluminium-citrate-sulfate-solution. This complex had been prepared by dissolving I mol Al-sulfate in 2 lit. water, adding 1/3 mol o~ citric acid, and finally adding 5-n NaOH during 3 hours corresponding to a neutralization of 5/6 of the sulfuric acid of the Al-sulfate. AEter this addition the furnish agglomerated furt ~er and a totally clear water phase was obtained. The furnish was allowed to stay over the night. The next day it was charged to the experimental paper machine during addition o~ 3~ Si02 on CS-weight as hexasilicic acid (disodiumsalt). The svlution of hexasilicic acid salt was prepared by dissolving precipitated and washed silicic acid in waterglass to a ratio Si02/Na?0=6,0. The hexasilicic acid was allowed to react with the furnish during 40 seconds before dilution with backwater.
The furnish was fast draining on the wire, and the machine worked without any problems or interruptions. The paper dried very fast and the filler retention was estimated to 91%.
~;rammage 75 g/m2 Gurley 13 s.
Density 780 kg/m3 ~obb 15 g/m2 Tens;l index ~ 33 kNm/kg Unger b. s./2 27 g/m2 Burst index 2,0 MN/kg Brightn. b s/s 77 %
Tear index ~ 5,5 Nm2/kg Opacity 92 %
~long. at break V~ 2,5 % Filler cont. 45 %
Dennison Wax both-sides/2 16
Claims (13)
1. Paper manufacturing process, characterized by the step of:
a) preparing an amphoteric mucus like composition by reacting 100 parts by weight of a cationic starch with a low degree of substitution of 0,02-0,10 in a waterswollen state with 1-8 parts by weight of an anionic linear (non-starch) polymer with a high degree of substitution of 0,5-1,0 to a hydrated but substantially insoluble mucus composi-tion, suspended in water - the primary structure;
b) preparing a mucus coated structure of fillers and/or cellulosic fibers by mixing a slurry of fillers and/
or fibers with the water suspended composition according to a) - the secondary structure;
c) reorganizing the mucus coating according to b) to a less hydrated and mechanically resistant gel coating by adding a colloidal solution of polymer microparticles consisting of polysilicic acid with 5-50 SiO2-units per polymer or of a polyaluminium-oxi-compound (basic Al-compound), in which the Al-valencies are partly neutralized and replaces by oxi bridges (-0- groups) - the tertial structure; and d) processing the obtained gel coated filler/fiber structure according to c) as a paper making furnish or part thereof.
a) preparing an amphoteric mucus like composition by reacting 100 parts by weight of a cationic starch with a low degree of substitution of 0,02-0,10 in a waterswollen state with 1-8 parts by weight of an anionic linear (non-starch) polymer with a high degree of substitution of 0,5-1,0 to a hydrated but substantially insoluble mucus composi-tion, suspended in water - the primary structure;
b) preparing a mucus coated structure of fillers and/or cellulosic fibers by mixing a slurry of fillers and/
or fibers with the water suspended composition according to a) - the secondary structure;
c) reorganizing the mucus coating according to b) to a less hydrated and mechanically resistant gel coating by adding a colloidal solution of polymer microparticles consisting of polysilicic acid with 5-50 SiO2-units per polymer or of a polyaluminium-oxi-compound (basic Al-compound), in which the Al-valencies are partly neutralized and replaces by oxi bridges (-0- groups) - the tertial structure; and d) processing the obtained gel coated filler/fiber structure according to c) as a paper making furnish or part thereof.
2. Process according to claim 1, characterized in that the primary mucus structure according to step a) consists of the reaction product between a cationic starch (CS) with a degree of substitution of 0,02-0,05 quaternized amino groups per glucose unit and carboxymethyl cellulose (CMC) with a degree of substitution of 0,50-0,90 in an amount of 1-5 parts by weight of CMC pet 100 parts by weight of CS.
3. Process according to claim 1 or 2, charac-terized in that the primary mucus structure according to step a) consists of the reaction product between cationic starch (CS) with a degree of substitution of 0,02-0,05 quaternized amino groups per glucose unit and an anionic polymer of the following group of mixtures thereof including CMC, the group consisting of the following members and present in the following amounts:
polyuronic acids (alginic acid)DS=l 1-8 p by weight/100 p by weight of CS
polyacrylic acid DS=l 1-2 p by weight/100 p by weight of CS
tri-tetra-silicic acid DS=0,5-0,7 1,6 p by weight/100 p by weight of CS
said primary mucus structure first being brought in contact with fillers and/or fibers to form a coating on them according to step b) and secondly being reorganized to a resistant structure by adding a colloidal solution of poly-mer microparticles of polysilicic acid and/or polyaluminium-oxi-compounds according to step c).
polyuronic acids (alginic acid)DS=l 1-8 p by weight/100 p by weight of CS
polyacrylic acid DS=l 1-2 p by weight/100 p by weight of CS
tri-tetra-silicic acid DS=0,5-0,7 1,6 p by weight/100 p by weight of CS
said primary mucus structure first being brought in contact with fillers and/or fibers to form a coating on them according to step b) and secondly being reorganized to a resistant structure by adding a colloidal solution of poly-mer microparticles of polysilicic acid and/or polyaluminium-oxi-compounds according to step c).
4. Process according to claim 1, characterized in that the secondary structure consists of kaolin filler, chalk filler, cellulosic fibers including groundwood and second grade fibers, coated with the primary mucus structure in an amount of 2-20% dry weight on weight of filler or 1-8% on weight of fibers, said secondary structure being reorganized by adding a colloidal solution of polymer microparticles of polysilicic acid or polyaluminium-oxi-compounds.
5. Process according to claim l,characterized in that the reorganization of the secondary coated structure is achieved by adding a colloidal solution of polysilicic acid (microparticles) with a degree of polymerization of 5-50 (SiO2-units per polymer) in an amount less than 10% calculated as SiO2 on the weight of CS used.
6. Process according to claim 1, characterized in that the reorganization of the secondary coated structure is achieved by adding a colloidal solution of polysilicic acid (microparticles) with a degree of polymerization of 5-50 (SiO2-units per polymer) in an amount between 1-5% calculated as SiO2 on the weight of CS used.
7. Process according to claim 1, characterized in that the reorganization of the secondary coated struc-ture is achieved by adding a colloidal solution of poly-aluminium-oxi-compounds (microparticles) in which the Al-valencies are partly neutralized to about 1/3 leaving a polymer unit of X2Al-O-, where X means a valency of a strong acid, said polyaluminium-oxi-compound being added in an amount less than 10% calculated as A12O3 on the weight of CS used.
8. Process according to claim 1, characterized in that the reorganization of the secondary coated struc-ture is achieved by adding a colloidal solution of poly-aluminium-oxi-compounds (microparticles) in which the Al-valencies are partly neutralized to about 1/3 leaving a polymer unit of X2Al-O-, where X means a valency of a strong acid, said polyaluminium-oxi-compound being added in an amount between 1-5% calculated as A12O3 on the weight of CS used.
9. Process according to claim 1, in which the polyaluminium-oxi-compound consists of a complex with citric acid, having the approximative unite formula in fully hydrated form Al4 (OH) 8Ci?+.SO?+ or in the corresponding dehydrated form Al4O4Ci?+.SO?-, where Ci is an equivalent of citric acid.
10. Process according to claim 1, characterized in that the reorganization of the secondary structure is performed in two steps with different colloids, the first step performed at a high concentration of the secondary structure with a colloidal solution of polysilicic acid and the second step performed in a diluted furnish (before the head box) with a colloidal solution of polyaluminium-oxi-comounds or in the reverse order, with the aluminium-oxi-compound added to step 1 and the silicic acid polymer to step 2, said colloidal solutions being added in amount correspond-ing to 1-5% calculated as SiO2+A12O3 on the weight of CS
used.
used.
11. Product combination for performing the process of claim 1, characterized in that it consists of a dry mixture of a cationic starch with DS=0,02-0,05 and CMC with DS=0,50=0,90 or/and the sodium salt of alginic acid with DS=1,0 in an amount corresponding to 1-5 parts by weight of the anionic component/components per 100 parts by weight of cationic starch.
12. Paper manufacturing process, characterized by preparing an amphoteric mucus composition by reacting a cationic starch (CS) with a degree of substitution of 0,02-0,05 quarternized amino groups per glucose unit and carboxymethyl cellulose (CMC) with a degree of substitution of 0,50-0,90 in an amount of 1-5 parts by weight of CMC per 100 parts by weight of CS to a hydrated but substantially insoluble composition, suspended in water, adding said mucus composition as a binder to a paper furnish, consist-ing of cellulosic fibers with or without fillers before paper formation.
13. Paper manufacturing process, characterized by preparing an amphoteric mucus composition by reacting a cationic starch (CS) with a degree of substitution of 0,02-0,05 (quaternized amino groups per glucose unit) and carboxymethyl cellulose (CMC) with a degree of substitution of 0,50-0,90 in an amount of 1-5 parts by weight of CMC per 100 parts by weight of CS to a hydrated but substantially insoluble composition, suspended in water and adding said mucus composition to a paper furnish, consisting of cellulosic fibers and/or fillers before paper formation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000398502A CA1187253A (en) | 1982-03-16 | 1982-03-16 | Paper making process utilizing an amphoteric mucous structure as binder |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000398502A CA1187253A (en) | 1982-03-16 | 1982-03-16 | Paper making process utilizing an amphoteric mucous structure as binder |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1187253A true CA1187253A (en) | 1985-05-21 |
Family
ID=4122316
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000398502A Expired CA1187253A (en) | 1982-03-16 | 1982-03-16 | Paper making process utilizing an amphoteric mucous structure as binder |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1187253A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2362016B1 (en) | 2007-07-16 | 2019-01-30 | Akzo Nobel Chemicals International B.V. | Filler composition |
-
1982
- 1982-03-16 CA CA000398502A patent/CA1187253A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2362016B1 (en) | 2007-07-16 | 2019-01-30 | Akzo Nobel Chemicals International B.V. | Filler composition |
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