US 3184373 A
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United States Patent FILLED PAPER CONTAINING A MIXTURE 0F RESIN AND MUCILAGINOUS MATERIAL AS A RETENTION AID AND PROCESS FOR PRO- DUCING SAID PAPER Hanns F. Arledter, Chillicothe, Ghio, assignor, by mesne assignments, to The Mead Corporation, a corporation of Ohio No Drawing. Continuation of application Ser. No. 600,410, July 27, 1956. This application July 5, 1961, Ser. No. 121,827
The portion of the term of the patent subsequent to June 28, 1977, has been disclaimed 14 Claims. (Cl. 162-152) This application is a continuation of my copending application Serial No. 600,410, filed July 27, 1956, now abandoned.
The present invention relates to paper and a process for producing the same, and more particularly to a high filler content paper and a process for producing the same.
Water-laid papers have been prepared heretofore having a relatively high filler content but having a filler retention in the range from about 50% to about 70% only. This low filler retention has constituted a serious drawback to the production of such papers, since from about 50% to about 30% of the filler particles originally added to the paper stock have passed through the wire of the papermaking machine without being retained in the paper and accordingly have been lost in the white water.
It is, therefore, the principal object of the present invention to provide a water-laid paper having not only high filler content but also a filler retention in excess of about 85% with only insignificant loss of filler particles in the white water, and a process of producing such a paper. Additional objects are to provide a paper having no tWo-sidedness, good dewlatering rate, and very little dusting.
The product of the present invention is a paper consisting of a water-laid inter-felted fibrous web containing fibers, filler particles, and a synergistic mixture of filler retention aids. The synergistic mixture of filler retention aids makes possible the production of a paper having a remarkable filler particle retention in excess of about 85%, and as high as about 99%, even in papers having a high filler content.
The paper contains from about 20% to about 90% of any fibers of papermaker length, i.e., less than 6 millimeters, or longer, e.g., 6-15 millimeters. The fibers which can be employed either alone or in admixtures include, for example, the following: so-called papermaking fibers, such as kra-ft, alpha-cellulose, sulfite cellulose, cotton, hemp, rag, esparto, straw, bagasse, and the like; synthetic organic fibers such as those formed from polyamide resins made by the polymerization of a hexamethylene diamine salt of adipic acid (Nylon), polytetrafluoroethylene fibers (Teflon), synthetic fibers made by the condensation of dimethyl terephthalate and ethylene glycol (Dacron), synthetic fibers made from polyacrylonitrile (Orlon), synthetic fibers made by the copslymerization of 40% acrylonitrile and 60% vinyl chloride (Dynel) polyvinyl chloride fibers, polyvinylidene chloride fibers (Saran), dinitrile fibers, cellulose acetate fibers, cellulose triacetate fibers, and viscose rayon fibers; synthetic inorganic fibers; such as glass, silica, aluminum silicate, steel wool, and the like; and natural inorganic fibers, such as asbestos.
The paper also contains from about 80% to about 10%, respectively, of filler particles, although amounts less than 10% may be employed, if desired. These filler particles preferably have a size in the range from about 60 mesh to about 2,000 mesh. While paper may also 3,184,373 Patented May 18, 1965 be made in accordance with the invention containing larger size filler particles, such paper has poor uniformity.
The filler particles may be of any nature usable in a paper and include solid particles as well as liquid particles. The liquid particles, such as those present in emulsions and latices, may serve as binders for the paper. The filler particles may be, for example, the conventional fillers used in the manufacture of paper, such as zinc sulfide, titanium dioxide, clay, talc, diatornaceous earth, barium sulfate, alumina, and other water-insoluble inorganic compounds. The filler particles may also be metallic powders or fiitters, such as silver, aluminum, gold, lead, tantalum, nickel, iron, and copper. Any water-insoluble thermoplastic or thermosetting resin which can be manufactured in powder form may be used in the paper to supply the filler particle content. The following thermosetting resin powders are typical of those which can be employed either alone or in mixture; phenolic resins, such as phenol-formaldehyde resins or phenol furfural resins; benzoguanamine formaldehyde resins; diallylphthalate polymers; and silicone resins. Suitable thermoplastic resin powders include, for example, polyacrylic resins, such as polymethylmethacrylate; polyvinyl chloride; cellulose acetate; ccllulose butyrate; polystyrene; polyethylene; polyvinyl butyral; polytetrafluoroethylene (Teflon); and polyvinyl acetate. Suitable fillers also include wood dust, pigments, and fluorescent or luminescent materials. Other suitable fillers include flocculated particles of so-called beater addition resins, latices, etc., of the nature of neoprene latex (polychloroprene), rubber latex, acrylic resin emulsions Rhoplex WN), polyvinyl acetate emulsions (117-88), polystyrene latices, and phenol-formaldehyde resin dispersions which may serve as binders for the paper.
In addition to the fibers and filler particles, the paper contains a. synergistic mixture of filler retention aids. The first component of the synergistic mixture is a watersoluble mucilaginous material, such as guar gum, methylated guar gum, mannogalactan, sodium alginate (Keltex), or protein substances. The paper contains from about 0.1% to about 2% of such materials based on the solids content of the paper. The second component of the synergistic mixture, which is added later in the process, is water-soluble polyethyleneimine resin, sold under the trade names PEI or Polymins P, water-soluble melamine formaldehyde resin, or water-soluble urea melamine resin, or mixtures thereof, from about 0.1% to about 2% of the material being employed based upon the solids content of the paper. An appreciably larger amount of these retention aids is undesirable, since such a larger amount may serve to decrease the filler retention properties thereof or may yield other unwanted effects. This synergistic mixture of retention aids makes possible the preparation of a high filler content paper with filler particle retention in excess of about by the obtention of large flocs of the fibers and filler particles in the paper furnish, so that the filler particles are not lost through the wire of a papermaking machine into the white Water.
In the foregoing and in the examples to follow, the retention aids are described as Water-soluble. These materials, as will be recognized by those skilled in the art, are high molecular weight polymers which, even though molecularly dispersed in water, yield solutions having the characteristics of colloidal dispersions in terms of viscosity and presence of the Tyndal effect.
It will be appreciated that water-laid filled papers may be produced having a filler retention in excess of 50% without the use of any filler retention aid. Accordingly, in order to show a synergistic effect by the use of filler retention aids, it is necessary to calculate the synergistic .Guar gum (based on alpha cellulose'and titaniumi dioxide content) j f 1. Melamine formaldehyde (basedon alpha-cellulo se etfect as the excess amount of filler retained above the retention level obtained without the presence of any filler retention aid. The synergistic efiFect of the mixture of fillerretention aids is readily shown by the data presented in the examples below: a
Melamine formaldehyde resin (based on alphap cellulose and titanium dioxide content) V 1 Percent material retained on wire 51 Net change in filler retention compared with Paper 7 7 Paper A-3 V V Alpha-cellulose fibers 33 Titanium dioxide filler particles 6-7 Polyethyleneimine (based on alpha-cellulose and V titanium dioxide content) Q 1 Percent material retained on wire 69 Net change in filler retention compared with Paper :A1 3,. +10.'8 Paper A-4 Alpha-cellulose fibers 33 Titanium dioxide filler particles 67 Guar gum (based on alpha-cellulose and titanium dioxide content) 1 Percent material retained on wire 72 Net change in filler retention compared With Paper Q A-l +133 P aper A-5 Alpha-cellulose fibers I 33 Titanium dioxide filler particles .67 Guar gum (based on alpha-cellulose and titanium dioxide content) 1 Polyethyleneimine (based 'on alpha-cellulose and Percent material retained on wire a a e Paper A6C0ntinu ed 92.5 Net change in filler retention compared with Paper In comparing Papers A-3, A-4, and A-5 it will be noted t-hatthe expected effect of adding 1% water-soluble polyethyleneimine plus 1% water-solubleguar gum, both based on the solids content of the paper, to Paper A..1 would be the sum of +10.8% and +13.8%, or +2A.6% increase in filler retention. However, it will be noted that in Paper A'5 thenet change in 'filler retention was +29.8% as compared with the expected change of +Q4.6% indicating a clear case of synergism. V
" EXAMPLE 2 t In this example a series of papers were prepared using the following stock: 77% alpha-cellulose fibers (400 parts), 11.5 zinc sulfide filler particles (60 parts), and 11.5% titanium dioxide filler particles (60 parts). In the following tabulation the amounts of additives are based on the solidscontent of the paper.
' In comparing Papers B-2, B-3, and B-4 it will be noted that the expected net. change in the addition of water-soluble guar gum 'plus Water-soluble melamine formaldehyde resin to Paper B-l' would be the sum of +8%' and '20%, or -12 while actually in'Paper 3-4 the net change in filler retention was +16%, clearly indicating a remarkable'synergistic elfcct.
EXAMPLE 3 titanium dioxide'contentf 1 'In this example the following paper stock was used: Percent material retained on wire 88 53% alpha-cellulose fibers (225 parts), 23.5 titanium Net change in filler retention compared with Paper 5 dioxide filler particles (100 parts), and. 23.5% diatoma- A-l +293 ceous earth filler particles 100 parts). 7 V
, V Net change V Percent filler Filler in filler Paper 7 Additives und in retention, retention paper percent compared withpaper 0-1, percent;
c-1 None 39.5 82 0-2 0.4% melamine formaldehyde 37.2 79 3 result. 0-3 0.2 V 41.9 89 4-7 0-4.--. 0.2%; $2.; g n; plus 0.4% mela- 45. 4 96. 5 +14. 5 mine'formaldehyde resin.
- 7 Paper A 6 V V a V i'ln'tihe above table the amount' of water-soluble mel- Alpha-cellulose fibers 33 1 amine formaldehyde resin and water-soluble guar gum Titanium dioxidefiller particles e 67', additives is based upon the total solids content of the and titanium dioxide content)"- Polyethyleneimine (based on alpha-cellulose and titanium dioxide content) g n paper. In comparing Papers C-Z C-3, and C-4 it will be noted'that the combination of melamine formaldehyde resin and guar gum would ,be expected to produce a net 7 change in filler retention comparedwith Paper C-1 of i 3%: plus V +7%, or +4%, while-actually'the combina- 0.5 tion of guart-gum andmelamine formaldehyde resin as shown in Paper C-4 produced a net change in filler retena Net change tion of +14.5%, clearly indicating a remarkable syner- Stock in retention gistic eifect once again, Paper Additives retention, compared percent with paper F-l, percent EXAMPLE 4 F-1 None 78 F2. 0.5% rnelarnine formaldehyde 77 1 The fiber and filter losses in the manufacture of a paper resula r I. F3 0.2% guar gum 79.5 +1.5 can be determined lrom the white water losses as shown F 4 0 5%me1mme fonnaldehyde 35 1 resin plus 0.27 guar gum. by this example. in the exampe tne following paper 10 F 5 05% melamine fflormaldehyde 89 +11 furnish was used: 33 sulfite cellulose fibers (450 grams), resin plus 0.2% guar gum plus 67% clay filler particles (900 grains), 200 liters water, and tgg ggg i ggfi gi sufiicient alum to pH 4.6.
White water N t change in l losses in Stock retention Paper Additives grams per retention, compared liter percent with paper D-l, percent D None 1.98 70 D 0.5% 1nelamine formaldehyde 2. 22 67 -3 lGSlll. D-3 0.5% guar gum 0.89 86. 8 +1 8 D-4 0.5% guar gum plus 0.5% mela- 0.37 94. 5 +g4 5 mine formaldehyde resin.
In the above table the amount of water-soluble melamine formaldehyde resin as well as the amount of watersoluble guar gum is based upon the solids content of the paper. In comparing Papers D-2, D-3, and D-4 it will be seen that the addition of both guar gum and melamine formaldehyde resins to the paper stock would be expected to produce a not change in retention of -3% plus +16.8%, or +13.8%, while in actuality as shown by Paper D-4 the net change in retention was considerably greater than this amount, and in particular +24.5%.
Under equal conditions a stock retention of 93.6% was obtained when zinc sulfide filler particles were used in lieu of the clay filler particles. Also, when 75% diatomaceous earth filler particles were substituted for the clay filler particles, at stock retention of approximately 94.5% was obtained by the use of the synergistic mixture of retention aids, i.e., water-soluble guar gum plus watersoluble melamine formaldehyde resin or water-solub polyet'hyleneimine resin.
EXAMPLE 5 Papers were prepared from the following paper furnish and tested for stock retention: 33% of glass fibers (33 parts), 67% of 100 mesh water-insoluble Vinylite powder (copolymer of vinyl chloride and vinyl acetate) (67 Once again synergism has been shown in the comparison on Papers E2, E-3, and E-4. When water-soluble guar gum plus water-soluble polyethyleneimine are used in combination, it would be expected that the net change in retention would amount to the sum of +6% plus +45% or +10.5%, while actually a net change in retention of +11.5% was obtained in Paper E4.
EXAMPLE 6 Papers were formed from the following paper furnish: 50% water-insoluble phenol formaldehyde resin powder, 50% alpha-cellulose fibers, and alum to pH 4.8.
EXAMPLE 7 Flocculation and retention can be improved if the flocculation is conducted at elevated temperatures above room temperature, especially when synthetic organic fibers are incorporated in the paper. A paper was prepared from the following stock and tested for stock retention: 33% viscose rayon fibers, 67% water-insoluble Vinylite resin powder (copolymer of vinyl chloride and vinyl acetate), 0.5% water-soluble guar gum based on the solids content of the paper, 0.7% water-soluble melamine formaldehyde resin based on the solids content of the paper and 10,000 parts Water.
Stock Paper Temperature of flocculation retention on Wire, percent G-l 68 F. (room temperature) 77 G- 130 F 88 Without flocculation by use of the filler retention aids, the retention is between and EXAMPLE 8 Net change in Percent.reretention come i tained on wire pared with Paper Additives paper H-l,
percent 68 F. 130 F. 68 F. 13min;
None 53 56 0.5 melamine iormalde- 49 46. 6 -4 9. 4
hyde resin. a H- 0.5% guar gum 61 67 +8 +11 H4--." 0.5% melamine formalde- 72 82 +19 +14 hyde resin plus 0.5% 7 guar gum. 11-5... 0.5% polyethylenehnine... 72. 2 +16. 2 H-6 0.5% guar gum plus 0.5% 86 +80 polyethyleneimine.
EXAMPLE 9 In this example a series of papers were prepared using making machine and dewatering, drying, and calendering theweb. Whether the flocculated slurry is added to the filler content and filler retention.'
The process of the invention may be further improved The filler content and filler retention of the paper may also be further improved by adding sufiicient sodium abietate of a pH of 11.0 to the fiber-filler slurry containing the synergistic mixture of retention aids and then adding thereto sufiicient papermakers alum to lower the pH to from about 4.5 to about The high filler content paper having high filler retention has been illustrated by the examples set forth above. The paper of the invention as well as the process of the invention will be furtherillustrated by the examples presented below.
the following stock having liquid filler particles: 50
grams of alpha-cellulose fibers, 100 grams of neoprene latex (36% neoprene content), and 10 gallons of water. In the following tabulation, the amounts of additives are based onthe solids content of the paper.
Stock retention; percent Paper Additives Alum to pH 6.4
0.5%,guar gum 53 1% polyethyleneimine 60 3% polyethyleneimina. 76 1% melamine formaldehyde re 53 0.5% guar gum plus 1% melamine formalde- 92. 5
hyde resin plus 1% polyethyleneirnine.
machine chest, or the action of the vibrating screen ahead 5 of the headbox. If the fiocs are subjected .to violent mechanical action, the efiect of the synergistic .mixture of filler retention "aid is inhibited, so that there is no longer obtained high'filler retention and sheet uniformity.
The paper may, therefore, be prepared by pumping an aqueous slurry of the fibers, filler particles and watersoluble mucilaginous material to the mixing chamber of the headbox of a papermaking machine, adding thereto the water-soluble polyethyleneimine, mel-amineformalde-- hyde, or urea melamine resins, or mixtures thereof, to
flocculate the fibers and filler particles with minimum agitation, forming the paper web onthe wire of the papermaking machine, and dewatering, drying, and oalendering the web. The flocculation of the filler particles and fibers is preferably conducted at a pH in the range from about 6 to about 7 and at a temperature above room tempera turc, preferably in the range from about 90 F. to about 140 F., in order to obtain maximum filler retention.
The preferred-embodiment of the process of the invention comprises pumping an aqueous slurry heated to 120 F.-of about one-tenth of the fibrous content of the paper along :with all of the filler particles and water-soluble EXAMPLE 10 U ":The stock was brought over beater chest, refiner, machine parts of ,water,-wa s added to thispaper stock. The stock.
.mucilaginous material to the mixing chamber of the headbox of a papermaking machine, adding thereto watersoluble polyethyleneimine,- melamine 'tformaldehyde, or
urea melamine resins, or' mixturesv thereof tofidcculate the fibers and filler particles at elevated temperature, mixing the flocculated heated slurrywith an aqueous unpaper withminimum agitation to flocculate hthe'added heated slurry of nine-tenths of the fibrous content of the,
late the filler and fiber "diluted in the machinechest to 3% chest, screen and vortrap to the mixing chamber'of the headbox of a paper machine, The stock was here diluted, in the conventional manner with the white water from the tray ofthe paper machine to a stock consistency of 5' grams per liter and formed Stock A containing in all 100,000 parts of water. 7 1
50 partsof kraft pulp in 1,000 parts of water was beaten separately to a beating degree of 28 S.R. and mixed in a mixing chamber before the he-adbox with 500 par-ts of powdered water-insoluble phenol formaldehyde resin 'of a size of 200 mesh plus 1,000 parts o-f'water. To the resin-fiber slurry there was added 4 parts of dissolved gu-ar gum. The fiberfplus resin powder slurry containing the water-soluble gu-ar gum wasthen diluted with water to 10,000 parts of liquid and flocculated with 3 parts of Water-soluble melamine formaldehyde resin dissolved in parts of Water. This formed Stock B.
Stock A and Stock B were then gently mixed together with -minimum" agitation in the mixing chamber "of the headbox of a papermachine' for approximately 5 seconds to fioccula'te the fibers in Stock A and fed to the Wire of the paperrnaking machine, dewatered, dried, and calen'der'ed into a paper.
The paper, product contained 53% of kraft fibers, 47% of phenol formaldehyde resin powder, 0.4% of watersoluble guar gum based on the solids content of the paper,
and 0.3% of water-soluble melamine formaldehyde resin based on the solidscontent of the paper.
EXAMPLE 11 50 parts "of sulfite celluloseiof-a beating degree of 42 diatomaceous earth in a mixing chamber before the headbox. 6 parts of water-solubleguar gum, dissolved in 400 was diluted to the ratio of 1:10 with water and 5 parts of water-soluble polyethylene'imine. added thereto to floccucontent. This stock formed Stock A. l
450 parts of sulfite cellulose was beaten to a beatingdegreexof 27 S.R.; at a stock consistency of 6% and stock consistency.
This formed 'StockfB. StockB was diluted with white water to a stock consistency of 5 grams 'per liter and pumped to the mixing chamber of the headbox of a paper machine 'at a rate of 30 parts of sulfite cellulose per minute.- Stock A was added to Stock B .(30 parts) at a rate of.
60 parts dry material per minute'and gently mixed to-' gethcnwith minimum agitation. The'stock was then fed upon the wire of the papermaking'machine, dewatered, dr1ed,and calendered.
The paper product so formed had excellent printahility :and contained 33% sulfite cellulose, 67% filler particles (zinc sulfide plus diatomaceous earth), 0.4% watersoluble guar gum based on the solids content of the paper, and 0.3% water-soluble polyethyleneimine based on the solids content of the paper.
EXAMPLE 12 50 parts of glass fibers having a diameter of 1.5 microns in 20,000 parts of water was mixed with 600 parts of waterinsoluble diallylphthalate resin powder in a mixing chamber before the headbox. 3 parts of water-soluble guar gum was then added thereto and the slurry flocculated with 5 parts of water-soluble urea melamine resin, thereby forming Stock A.
400 parts of glass fibers having a diameter of 3 microns was beaten, diluted with white water, and pumped to the mixing chamber of the headbox of a paper machine to form Stock B.
Stock A was added to Stock B, gently mixed together with minimum agitation, and a paper product formed by feeding the resultant flocculated slurry to the wire of the papermaking machine, dewatering, drying, and calendering the webso produced.
The paper product contained 44% glass fibers, 56% diallylphthalate resin powder filler, 0.3% water-soluble guar gum based on the solids content of the paper, and 0.5% water-soluble urea melamine resin based on the solids content of the paper. The paper product had a resin retention of 97%.
EXAMPLE 13 500 pounds of kraft pulp was beaten in a heater to a beating degree of 17 S.R. at a stock consistency of 6%. 500 pounds of water-insoluble phenol formaldehyde resin powder with a softening point of 70 C.-85 C. and a screen mesh size ranging from 80 to 200 was dispersed in 5,000 pounds of water containing 0.5 pound of high viscosity methyl cellulose. The beaten kraft pulp and the phenol form-aldehyde resin powder suspension was then mixed in the machine chest. The stock consistency was lowered to 2.45% and 5 pounds of cold water-soluble guar gum added thereto. The stock was pumped to the mixing chamber of the headbox of a paper machine and flocculated at around 2.35% stock consistency, pH 7.0, with a 2.5% solution containing 6 pounds of water-soluble urea melamine resin. The stock consistency was then reduced to 1.0% with white water and aluminum sulfate (alum) added to obtain a pH of 4.5. Shortly before the stock went on the wire of the paper machine a solution of 0.5% sodium abietate of pH 11 was added in such an amount that approximately 1.8% resin was added to the stock. The flocculated fiber-filler slurry was then fed to the wire of the papermaking machine, dewatered, dried, and calendered into a paper product containing 50% kraft fibers, 50% phenol formaldehyde resin powder, 0.5 water-soluble guar gum based on the solids content of the paper, and 0.6% water-soluble urea melamine resin based on the solids content of the paper.
EXAMPLE 14 25 parts of glass fibers of 3 micron diameter, 12.5 parts of viscose rayon fibers, 12.5 parts of cellulose fibers, and 100 parts of polyvinyl acetate emulsion of 50% resin content was mixed in 10,000 parts of water. Alum was added to a pH of 5.0, ammonia added to a pH of 9.0, and the pH finally adjusted to 7.0 with alum to flocculate the slurry. The flocculated stock mixture was pumped to the headbox of a Fourdrinier machine and 0.5% watersoluble guar gum and 1% of a water-soluble polyethyleneimine and water-soluble melamine formaldehyde mixture added. A paper product was then formed in the convention-a1 manner.
The paper product contained 25% glass fibers, 50%
' polyvinyl acetate, 12.5% viscose rayon fibers, and 12.5%
10 cellulose fibers, as well as 0.5% water-soluble guar gum and 1% water-soluble polyethyleneimine plus water-soluble melamine formaldehyde resin based on the solids content of the paper. The product had a resin retention of 94%.
Data showing synergism are presented below.
Additives: percent Alum added to pH 5.0 48 Alum added to pH 5.0, ammonia to pH 8.8 66 Alum added to pH 5.0, ammonia to pH 9.0, and
alum to pH 7.0 78 0.5% guar gum 52 1% polyethyleneimine 56 Alum to pH 5.0, ammonia to pH 9.0, alum to pH 7.0, 0.5% guar gum, and 1% polyethyleneimine 96 EXAMPLE 15 9 part sof viscose rayon fibers (5.5 denier, 6 mm. length), 1 part of viscose rayon fibers (0.75 denier, 4 mm. length), and 20 parts of neoprene emulsion (36%) were dispersed in 6,000 parts water of a pH of 5.2. Ammonia was added to a pH of 9.2. Alum was added to a pH of 6.4 and the slurry then flocculated in the headbox with 1% water-soluble guar gum and 1% water-soluble polyethyleneimine. A well-bonded strong paper, containing approximately 6% binder, was obtained.
The high filler content paper of the invention may be used for decorative laminates, flame retardant laminates, chemical resistant laminates, and also for printing papers and the production of films by exposing the paper to heat and pressure in a calender.
Various modifications and changes may be made in the invention herein set forth without departing from the spirit thereof and accordingly the invention is to be limited only within the scope of the appended claims.
1. A filled paper having a filler retention in excess of about 85% consisting of a water-laid interfelted fibrous web consisting of from about 10% to about 80% of filler particles, from about 90% to about 20% respectively of fibers, and a synergistic filler retentionmixture of from about 0.1% to about 2% of a water-soluble mucilaginous material selected fromthe gnoup consisting of mannogalactan and sodium alginate based on the soilds content of the paper, and from about 0.1% to about 2% of at least one water-soluble resin selected from the group consisting of polyethyleneimine, melamine formaldehyde, and urea melamine resins based on the solids content of the paper.
2. A paper as set forth in claim 1 wherein the filler particles are water-insoluble resin powder.
3. A paper as set forth in claim 1 wherein the filler particles are Water-insoluble inorganic compounds.
4. A paper as set forth in claim 1 wherein the filler particles are flocculated liquid particles.
5. A paper as set forth in claim 1 wherein the fibers are cellulosic fibers.
6. A paper as set forth in claim 1 wherein the fibers are synthetic organic fibers.
7. A paper as set forth in claim 1 wherein the fibers are synthetic inorganic fibers.
8. A paper as set forth in claim 1 wherein the fibers are natural inorganic fibers.
9. The process of preparing a filled paper having a filler retention in excess of about comprising pumping an aqueous slurry consisting of water, from about 2.0% to about of fibers, from about 8 0% to about 10% respectively of filler particles, and from about 0.1% to about 2% of a water-soluble mucilaginous material selected from the group consisting of a mannogalactan and sodium alginate based on the solids content of the paper to the headbox of a paper-making machine; adding from about 0.1% to about 2% based on the solids content of the paper of at least one water-soluble resin selected from the group. consisting of p-olyethyleneim-ine, "melamine diormialdehyde, and urea. melamine resins theretolwith minimum agitationto, form a synergistic filler retention mixture andto, fioecu-l atevt'he fibers and filler particles;
forming a paper web on the Wire of the paper'm'aking machine; and, d'ewatering, drying, and calendering the web.
-10. The pro cess as set forth in claim 9 wherein the" flocculation isconducted at a pH in the range from" about 6 to about 7.' l
-11. The process as set .forthin claim 9 wherein the flocculationis conducted at a temperature in the range dirom about 90 F. to about 140 F.
12. The process as set forth in claim 9 wherein after.
the addition of the resin there is added ,e-lkalinesodium abietate to adjust the pH of the flocculat-ed slurry to about 8.5 and then there is added alum to further adjust the pH of the flocculated slurry to about 4.6-4.8.
13. The process of preparing a'filled paper having a filler retention in excess of about 85% CQ'IIlPll'iS/ll'lg mixing a flocculated aqueous slurry consisting of water, about one-tenth of the 90-20% fibrous content of the paper, from about 10% to about 80% respectively of filler particles, and a synergistic filler retention "mixture oft'ron'i about 0.4% to about 2% based on t-h-eweight of the solids content of the paper of a water-soluble mucilaginone material selected firom the group consisting of a mannogalactan and sodium alginate and from about 0.1% to about 2% based on thefsolids content of the paper of at least one water-soluble resin selected from the group consisting of polyethylenei-mine, melamineformaldehyde and urea melamine res-ins'withan aqueous slurry conr 12 sisting of water and nine-tenths of the 20% fibrous content of, the paper in the headbox of a papermaking machine with minimum agitationf forming e. paper Web on the wire of the papermalking 'machine;and dewate-rin-g, drying, and calendering the web.
14.'The process :as set forth in. claim 13 wherein-the aqueous slurry of labout one-tent-h of the. fibrous content of the paper has a temper-attire in the range of iirom about 90 F. to about F. and the slurry containing nine-tenths of the fibrous con-tent of the paper isunheated,
. References-Cited by the Examiner I UNITED STATESPATENTS DONALL H. SYLVESTER, Prinjqry' Eicdminer. RICHARD .1 NEVIUS, MORRIS o. WOLK, Examiners.