CA1097466A - Process for the production of paper containing starch fibers and the paper produced thereby - Google Patents

Abstract

#326 HENRY R. HERNANDEZ
DONALD S. GREIF
ALBERT N. BARNA
DOUGLAS S. THORNTON

A PROCESS FOR THE PRODUCTION OF PAPER CONTAINING
STARCH FIBERS AND THE PAPER PRODUCED THEREBY

Abstract of the Disclosure A process for the production of paper and paperboard is disclosed wherein water-insensitive starch fibers, produced by extrusion of a starch dispersion into a coagulating solution, are employed to replace all or part of the cellulosic or other pulp conventionally employed. There is also disclosed a method for the incorporation of functional additives into paper during the production thereof; and a method for binding fibers in non-woven webs.

Description

1139'~66 il BACKGROUND OF THE INVENTION

I¦I. Field of the Invention: This invention is directed to a ~process for producing paper using water-insensitive starch fibers to replace all or part of the cellulosic or other pulp convention-l ally employed, and to the paper produced thereby. The invention I ~ also relates to a novel method for the production of certain specialty papers, as well as to methods for the incorporation of functional additives into paper during the production thereof and for binding fibers in non-woven webs.
II. Brief Description of the Prior Art: Various natural fibers (other than cellulose) as well as a variety of synthetic fibers have been employed in making paper, however, all these replace-¦me~ts have failed to provide a commercially acceptable substitute I
¦for celluLose due to their cost, poor bonding properties, chemical¦
¦incompatibilities, difficulty in handling ln papermaking systems, ¦etc. While it has also been suggested to use starch fibers in ¦various aspects of the papermaking process, commercial attempt6 to¦
¦use such fibers have not resulted in any degree of success and paper is still being manufactured almost completely from wood-base~
cellulosic ingredien~s - the supply of which is bein~ rapidly Idepleted.
¦ It is apparent that the aqueous systems normally ¦employed in the paper making operations require pulp fibers possessing sufici.ent water-insensitivity that they can be used ¦ in all aspects of the manufacturing process throughout a relatively wlde pH range without losing their integrity. In this 1 ¦I regard, the few references which suggest the replacement of starch fibers for cellulose fibers (e.g. U.S. Patent 1,682,293) require 1~ chemical modification of the starch in order to radically change 11 its naturally occurring properties prior to forming the fiber ¦l so as to provide the degree of water-insensitivity required l, l in the paperma~ing process. Alternatively, other refer-ences (e.g., U.S. Patent 2,570,4~9) require that the papermaking process itself be modified as by replacing the conventionally employed aqueous system with an alcohol solvent in which the starch fibers are not soluble. It will be recognized that the use o-f such ~echniques is both impractical and uneconomical when employed on a commercial basis.
As another aspect of the papermaking operation, it is often necessary to incorporate additives into the pulp in order to achieve specific end properties. Thus, additives such as pigments, latices, synthetic microspheres, fire retardants, dyes, perfumes, etc. are often employed in the manufacture of paper. The efficient retention of these additives at the wet end of a paper machine presents difficulty to the manufacturer since that portion which is not retained create~ not only an economic loss, but also a significant pollution problem i~ it becomes part of the plant effluent. Furthermore, such additives are also added via coating or saturation processes commonly known in the art. These processes usually require that ex~ess heating energy be consumed to re-dry the paper after coating~
Moreover, in some instances the coating systems are required to be solvent based which then creates extreme capital expense and requires regulation to recover volatile materials.
It is therefore an object of the present invention to provide a commercially viable process for the use of starch fibers as a partial or complete replacement for cellulose in conventional paperma~ing operations.
It is also an object to provide a process which effi-ciently enables the retention and incorporation of additives into paper during the manufacture thereof.
~ t is a further object to provide a process which i I

enables water-insoluble additivcs to be introduced into the paper as fiber encapsulated additives.
Another object is to provide ordinary and improved specialty papers according to such process.
A further object of the invention is to provide an efficient and economical process for binding synthetic and/or natural fibers in non-woven web form.
These and other related objects will be apparent from the descrip-tion which follows.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided in a process for manufacturing paper and paperboard comprising the steps of in-troducing an aqueous slurry of fibrous pulp material onto a screen in such a manner that the water is removed thereby forming a sheet of consolidated fibers which, upon pressing and drying, yields the final paper product, the improvement comprising the step of employing starch in an amount of from 1 to 100% by weight of the pulp in the orm oE water-insensitive starch fibers of 10 to 500 microns in diameter, said fibers being produced by extruding a thread-like stream of a colloidal dispersion of starch, at 5-40% by weight solids, into a moving coagulating bath comprising an aqueous solution of a coagulating salt selected from the group consisting of ammonium sulfate, ammonium sulfamate, mono-basic ammonium phosphate, di-basic ammonium phos-phate and mixtures thereof, said solution containing said coagulating salt in an amount at least sufficient to coagulate said starch.
In another aspect, there is provided paper and paperboard composi-tions comprising a blend, on a weight basis, of 0-99% papermaking cellulose pulp fibers and 1-100% water-insensitive starch fibers of 10 to 500 microns in diameter produced by extruding a thread-like stream of a colloidal dis-persion of starch, at 5-40% by weight solids, into a moving coagulating bath comprising an aqueous solution of a coagulating salt selected from the group ; ~
, ~ .

, ~ca74~6 consisting of a~nonium sulfate, ammonium sulfamate, mono-basic ammonium phosphate, di-basic ammonium phosphate and mixtures thereof, said solution containing said coagulating salt in an amount at least sufficient to coagu-late said starch.
Furthermore, the invention provides a method for incorporating wa~er-insoluble additives within the pulp of a conventional papermaking system comprising the steps of thoroughly dispersing at least one water-insoluble additive in a colloidal dispersion of starch, said starch being present in an amount of 5-40% by weight solids, and precipitating said dispersion by extruding a thread-like stream of said dispersion into a moving coagulating bath comprising an aqueous solution of a coagulating salt selected from the group consisting of ammonium sulfate, ammonium sulfamate, mono-basic ammonium phosphate, di-basic ammonium phosphate and mixtures thereof, said solution containing said coagulating salt in an amount at least sufficient to coagulate said starch so as to form water-insensitive starch fibers en-capsulating said additive; and subsequently using the resulting starch fibers as components in a papermaking pulp system.
Thus, it has been found that water-insensitive starch fibers, pTO-duced by the precipitation of a colloidal dispersion of starch in a coagula-ting salt solution, may be employed as partial or complete replacements ~or cellulose and similar fibers in conventional paper and paperboard manufac-turing operations. The fibers may be used to extend the pulp, as a means for incorporating additives into the paper product, as binder for the fibers in non-woven webs or for any combination thereof.
As used herein, the term "paper and paperboard" includes sheet-like masses and molded products made ~rom fibrous cellulosic materials as well as such fibrous materials as may be derived from synthetics ~such as polyamide, polyester, rayon and polyacrylic resin), mineral fibers ~such as asbestos and glass), and the like.
As used herein, the expression "conventional papermaking operation"

-4a-, ~97~66 means the process of introducing an aqueous slurry of wood cellulose fibers ~which have been beaten or refined to achieve a level of fiber hydration and to which a variety of functional additives can be added) onto a screen or -4b-.~ .

7~6~i similar device in such a manner that the water is removed, ~1 thereby forming a sheet of the consolidated fibers which, u~on pressing and drying, can be processed into dry roll or sheet form.
Also included within the scope of this expression are the con ventional processes for the production of wet and dry-laid non-wovens.
Thus, in one aspect the present invention provides a feasible, efficient and economical process for extending ¦ existing raw material sources. Further,it allows th~ paper manufacturer a far greater degree of flexibility in his oper-ations: he is able to obtain starch fibers in dry or wet-slab form and store them for subsequent use or he may incorporate the starch fiber manufacturing process into his plant as an integrated step in his pulping ~md/or papermaking operations.
~oreover, the present invention offers the manufac-turer a new means for incorporat:ing additives into paper prod-ucts with increased retention and consequently less economic loss and fewer pollution problems. As previously discussed, it is common practice in the manufacture of paper to introduce additives in conjunction with the fibers used in the pulp.
Such additives are incorporated in order to achieve specific paper properties other than what is contributed by the fiber itself. Such additives include materials which f~mction as 1l pigments (titanium dioxide, for example) as ~ell as other materials introduced into paper to achieve such properties as improved ¦¦brightness, opacity, smoothness, ink receptivity, fire retard-l¦ance, water resistance, increased bulk, etc. As an additional ¦lembodimen~ of the present invention, it has been found that l¦when starch fibers are produced so as to contain various func-ii tional additives, and such fibers are then utilized in the llaqueous paper ~aking process, retention of the additives is _ 5 1C\~74~6 1~ ~
greatly increased when compared with that achieved using current methods. In addition to the increased retention, a further advantage of the addition of additives in this manner is the fact¦
that there is no necessity for relying upon the sensitive charge balance relationship between the cellulose fiber additive and the flocculant (e.g., alum) or other retention aids.
Indeed, it is unnecessary to use a flocculant or retention aid with the starch fibers used in the present invention.
It has also been found that non-woven webs can be produced in wet or dry-laid form in accordance with the present invention wherein starch fibers are incorporated within the web to serve as binders therefor. The starch fibers may be retained in the final web or,if the base fiber employed in the web is non-combustible, may be removed, depending upon the de- ¦
sire.d end use.
Specifically, the present invention is directed to an improvement in a process for manufacturing paper and paperboard co~prising the steps of introducing an aqueous slurry of a ~ fibrous pulp material onto a screen in such a mannar that the water - 20 j is removed thereby forming a sheet of consolidated fibers which, upon pressing and drying,yields the final paper product. The I reD/~ci~ ~
improvement comprises the step of cm~l~i~g~ from 1 to 100~/o by k)i~ ~r-i~?S~S~ e weight of the pulp ~ e~ starch fibers of 10 to 500 microns in diameter produce~ by extruding a thread-like stream of a colloidal dispersion of the starch,at 5 to ~0% by weight solids, into a moving coagulating bath comprising an aqueous solution of a coagulating salt selected from the group consisting I
of ammonium sulfate, ammonium sulfamate, mono-basic ammonium ~ -¦phosphate, di-basic ammonium phosphate and mixtures thereof, ~h~ ¦
¦ solution containing the coagualting salt in an amount at least sufficient to coagulate the starch.

1l ~0~466 I DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
ii The process of the present invention may readily be ; adapted to be used on any conventional paper making equipment i using the procedures commonly used in the specific plant, with i the only difference residing in the substitution of starch fibers for all or part of the cellulose pulp.
The starch fibers employed may be produced using a number of variations, the only requirement being that the water-insensitive fibers have a diameter of 10 ~o 500 microns and that they be precipitated by the extrusion of a thread-like stream of ¦
a colloidal dispersion of starch at 5 - ~0%, by weight solids, into a suitable moving coagulating salt solution.
Fibers may be employed which are produced from any naturally occurring or fractionated starch. Thus, corn starch, waxy tnaize, rice, tapioca, wheat, potato, high amylose corn starch commercial amylose powder, etc. may be employed with naturally occurring corn starch, tapioca and waxy maize being preferred due to their economy and availability.
The concentration of the starch solids in the dispersio~
should be about 5 to 40% by weight. While higher concentrations of starch solids may be used, the resuLting dispersions become very viscous and special equipment is required to handle them.
The particular concentrations employed in the dispersions will however, affect the properties of the final fiber and the desired~
¦~ end use. As an example, starch fibers prepared from 5V/o solids ¦¦ dispersions have been found to be particularly useful in the production of glassine or greaseproof papers while starch fibers prepared from 15V/C solids dispersions have been found better suited for use in rore porous papers ~such as ~ilter peper.

1-~7466 j The particular starch employed must be used in the form Il¦of a colloidal dispersion. For the purposes of this invention, ¦Ithe term "colloidal dispersion" means dispersion of starch which ,lis substantially free of granules and which exhibits, on standing ~lat the temperature at which it is to be used9 little evidence of ¦igelation or precipitation. This state of dispersion may be obtained using a variety of techniques depending upon the particu-l lar starch base employed, the desired end use and the equipment available.
¦ When native starches that are very high in amylopectin i content, such as waxy maize, are employed, a suitable colloidal dispersion may be prepared merely by thoroughly cooking the starch in water with no chemical additives or modifications required.
In most cases where starches whi.ch contain less than about 95%
; amylopectin are employed, it will be desirable to chemically derivatize or modify the starch to ensure its colloidal dispersion before adding it to the aqueous system. The derivatization or I ¦ modification is carried out to an extent which will insure the production of the desired colloidal dispersion without affecting the ability of the starch to subsequently precipitate. Alterna- ¦
¦tively, if there is no objection to the presence of caustic in ¦the system, the latter starches may be dispersed in aqueous sodium hydroxide, potassium hydroxide or other common alkali. As further alternatives, the starch bases may also be dispersed in a minor amount of an organic solvent such as dimethylsulfoxide and then added to water, or the starch base may be dispersed in conjunction with chemical additives such as urea and/or para-¦formaldehyde. In the cases where causticizing is employed, the ~¦amount of alkali used must be sufficient to adequately disperse !¦the starch. Typical amounts of alkali used when sodium hydroxide ¦

!, I

10''7466 ¦lis employed are from 15 to ~0%, by weight, based on the weight of the starch.
In preparing the starch dispersion, the starch is added I
~¦to the dispersing medium and vigorously agitated until a state of i colloidal dispersion is achieved. In the case of dilute dispersions of starch (i.e. about 5-10% starch solids by weight), this will require about 45 minutes, with longer periods and/or moderate heat required for more concentrated starch dispersions lor for certain chemically modified starch bases.
¦ Most of the starch dispersions, including those of waxy ¦maize and most of the chemically modified starches, may be cooled to room temperature prior to introduction into the coagulatT
ing bath. In the case of a few of the less chemically modified starches, it will be preferred ~o employ the dispersions at approximately the elevated temperatures at which they are prepared so as to maintain the necessary colloidal dispersion and to insure efficient fiber production.
The coagulating bath used in preparing the starch fi~ers employed in the present invention comprises an aqueous solution containing specific ammonium salts selected from the group con-` sisting of ammonium sulfate, ammonium sùlfamate, mono- and di-¦¦basic ammonium phosphate and mixtures thereof. It is also ¦¦possible to combine the above-mentioned functional salts with other compatible salts which will form a starch precipitate so as ~to obtain satisfactory coagulation and a fibrous product. Suit-able salts for this purpose include ammonium persulfate, ammonium carbonate, ammonium bromide, ammonium bisulfite, ammonium nitrite ammonium nitrate, ammonium bicarbonate, ammonium oxalate, sodium l and potassium chloride, sodium and potassium sulfate, among l~others. Generally, no ad~antaee is seen in using these additional l ~, ~1 1 ~l;)C~74~

salts since the ammonium sulfate, sulfamate or phosphate salts must still be present in their respective minimum amount in order i to effect coagulation. The only instances where the presence of substantial amounts of other salts may be desirable is in the ¦
use of the recycled coagulation bath wherein salts are present which have been generated in situ, as will be discussed herein-below.
The minimum concentration of the salt required to ~ effect coagulation as well as the preferred salt or salt blend will vary depending upon the particular starch base employed.
For example, in the case of waxy maize starch, it is necessary for ammonium sulfate to be present in amo~mts of at least 35%, ¦ by weight of the total solution, ammonium sulfamate 72% (satura-tion), di-basic ammonium phosphate 37% and mono-basic ammonium phosphate 40%. In the case of corn starch or similar starches ¦ containing about 64-80% amylopectin, lower concentrations of ¦ salt may be used with ammonium sulfate required in amounts of 20~/o~
' ammonium sulfamate 50%, mono-basic ammonium phosphate 25% and di-basic ammonium phosphate 30%. In the case of hybrid corn starches containing less than about 50% amylopectin, ammonium sulfate must be present in amounts of at least 15%, ammonium I sulfamate 40%, di-basic ammonium phosphate 25% and mono-basic ammonium phosphate 20%.
~ It will be recognized that alkali salts are generated ¦¦ in the coagulating bath when causticized starch dispersions are l employed, with satisfactory production of the desired starch I fibers continuing until the level of the generated salt is relatively high. The generated salt tolerance level above which l~ production of the fibers becomes inefficient will vary depending i~ upon such factors as the specific salt employed, the total salt ,1 - 10 -solids employed, the starch solid concentration in the dispersion,~
the amount of amylopectin in the starch base, etc. Once this salt ¦tolerance level is determined a steady-state system may be achieved ¦at this maximum level (or less~ by the periodic addition of ammonium sulfate on a continuous basis. As an example, when sodium hydroxide is used as a dispersing medium and the starch mixture is extruded into an ammonium sulfate coagulating bath, sodium sulfate i.s generated. In this case, it has been found that production of corn starch fibers (13% solids dispersion) will con-tinue at a satisfactory level until a maximum of about 70 parts : sodium sulfate per 30 parts ammonium sulfate (4.~% solids solution)is present in the bath. Above this level of sodium sulfate, production of the starch fibers becomes less e~ficient and the resulting fibers tend to lose thleir individual integrity. However, by adding a small amount of an inorgan-lc acid to the initial coagulating bath or to the bath during formation of the fibers, th level of the generated sal~ in the system may be appreciably raised before production of the :Eibers is seriously affected. Thus ~using the eæample discussed previously, the addition of as little 1 as 3 parts of sulfuric acid per hundred parts of the initially charged coagulating bath salt results in a tolerance level of 90 ¦parts sodium sulfate per 10 parts ammonium sulfate thereby increas-I ¦ ing the longevity of the coagulating bath.
It is apparent that the salt solution used in the fiber~forming process may be recycled and used again once the fibers have been removed. It is, however, important that the salt concentratio e maintained, especially where the salt is being depleted through a chemical reaction lnvolving the starch dispersion as it is ~ntroduced. In this regard, the starch dispersions which do not lontain caustic present little diffic~lty in recycling other than I . , .: . .

lVq7466 ¦that the solids content of the salt be maintained. However~ in I those cases where causticized starch dispersions are employed, chemical reactions with the coagulating solution will occur. For ~exam2le, if ammonium sulfate is used, the reaction results in the ¦formation of ammonium gas and sodium sulfate. The recycling of ¦such a system can be extended by recovering the ammonia in an ¦acid scrubber and returning it to the system as ammonium sulfate.
¦The generated sodium sulfate can be used in the coagulating bath ¦as part o~ the salt blend until the tolerance levels discussed ¦previously are attained or can be used as a raw material in o~her ¦aspects of the pulp or papermaking operation, e.g. as a source of I''salt cake" in the production of Kraft pulp.
¦ Starch fibers can be produced at any temperature at ¦which the starch dispersion can be handled. Generally, the ¦coagulation bath is maintained at about room temperature (20C.) ¦ during production of the fibers,, however, temperatures as high as about 70C. may be used. These higher temperatures may be desired ¦under certain conditions since they increase the solubility of i the salt in the coagulating bath resulting in more concentrated 1 solutions. Th~s, when it is desired to produce waxy maize fibers using mono-basic ammonium phosphate as coagulant, it is desirable ¦
¦ to increase the temperature of the bath so as to obtain a concen-¦ tration of salt of approximately 40% (saturation level for the mono-basic ammonium phosphate at 20C. is 2 8~/o) .
¦ In preparing the starch fibers used in the invention, the starch dispersion is introduced continuously or by drops in ¦ the form of a thread-like stream into the moving coagulating salt , s~lution. This Lntroduction ma~ be accomplished either~a~ove or below the salt solution using any conventional techniques. Thus, 1 the dispersion may be extruded through an apparatus containing at~
l least one aperture, such as a spinnerette, a syringe or a biure~
Il ~
1~ - 12 - I
li l l i6 feed tube. Alternatively, the dispersion may be discharged under pressure from a pipe or tube containing a plurality of ¦ apertures into a surrounding enclosed area, e.g. a concentric ~ pipe, containing the moving coagulating solution. Various ¦ adaptations of the above and related techniques may be used and the fibers may be thus produced using either batch or continuous operations.
In accordance with either embodiment, the aqueous salt coagulating solution should be moving when the starch dispersion ¦ is introduced and the directionality of the two flows can also be utilized in controlling fiber lengths and diameters or widths.
Thus, if the salt solution is moving in a direction generally concurrent with the flow of the starch dispersion, ~ounder fiber lengths are formed; if thle starch dispersion is introduced at an angle of about 90 to the flow of the salt soluti,on, '~
l ~er-~r~ !
B ~ relatively flatter fibers are formed. Generally a~erat~e~ of 10¦
to 500 microns in diameter are preferred, in order to produce ¦ fibers of the size required herein. Thus, the starch fi~ers used ¦ in the present invention have diameters (widths) of 10 to 500 microns and will generally have lengths of from about 0.1 to I ~ 3.0 mm. i~ they are to be used as cellulose pulp replacements in paper. For non-woven application, fibers of longer lengths may be employed.

Il .

~LC3''3~66 It will be recognized that the length, cross-sectional size and configuration of the resultant fibers are dependent upon a number of inter-related parameters in addition to those described hereinabove. Thus, the YiSCosity, the solids content of the starch dispersion, as well as the particular components used in the coagulating solution and/or starch dis-persion and the relative flow viscosities thereof are additional factors which can be used in conjunction with the parameters discussed previously in order to control the dimensions of the resultant fiber.
This and similar coagulating processes producing starch fibers use~ul herein are described in United States Patent No. 4,139,699 issued February 13, 1979, National Starch and Chemical Corporation, as well as in United States Patent 2,902,336 issued September 1, 1959, Pieter Hiemstra and Johannes Muetgee~t~ Various modifications of the processes may also be employed as long as the final fiber possesses sufficient water insensitivity to be employed in the papermaking operation.
l`he resulting aqueous slurry or suspension of starch flbers may be used directly by introducing it into the pulp stream thereby enabling pro-duction of fibers and paper web "in-line" in the paper manufacturing plant.
If this embodiment is to be used, it is generally preferred to first wash the fibers free of coagulating salt prior to introducing the slurry into the paper manufacturing operation. Alternatively, the fibers may be recovered in the dry state by collecting from water on a screen or similar device. It is then preferable to reslurry the fibers into a non-aqueous solvent such as methanol, ethanol, isopropanol, acetone or the like in which the fibers are not soluble. The fibers are then reco~ered, as by filtration, from the solvent and ~.

l~g7466 ,~dried. Other methods such as centrifuging, flash-drying or ¦~spray~drying may also be used to remove the water. Once dried, the fibers may be re-introduced into an aqueous medium and will jexhibit excellent re-dispersibility maintaining their discrete, ~discontinuous structure. Alternatively, the fibers may be recovered from the slurry, as by filtration, washed and placed in water at levels of up to about 50% solids and formed into "wet-slabs" for subsequent use.
l It is also to be noted that the starch employed may be ¦chemically treated to vary the properties of the fiber produced ¦ or to help effect formation of the colloidal dispersion. ~lter-¦natively, the starch fibers may be treated after formation in ¦order to produce certain functional characteristics. Thus, the starch may be chemically treated, as by aminoethylation, in order to provide rapid dispersibility of the starch in the dispersion, I which treatment will also result in the production of a fiber which possesses a cationic charge when employed in an a~ue~us Imedium. Similarly, a starch may be used which is modified to ¦contain anionic groups so as to be stable in a dispersion and ¦ which, after regeneration, will produce a fiber having anionic properties. The fibers may also be modified after their formationl ~in order to achie~e specific functional properties. Thus, improv-¦
ed anionic functionality might be obtained by bleaching the fibers af~er precipitation as long as the conditions are not so severe as to destroy the fibers. The properties of the fibers may also be controlled by using blends of modified and unmodified starches or by the addition of other functional materials, such as polyacrylic acid, to obtain the specifically desired properties.

ç;

~1 As one of the advantages of the method of the present 1, i¦invention there is provided a means to improve paper products in ¦¦ a variety of manners due to the properties which are either ¦~inherent in or which may be im~rted to the starch fiber itsel~.
As an example of such improved properties, we may consider the production of such diverse specialty papers as glassine paper and filter paper which require special treatment when conventionally produced.
Glassine paper is made from pulps in which the quality of the fiber permits a high degree of hydration. It is the mechanical treatment of the pulp while suspended in water that causes the distinctive greaseproof properties. The fibers are fibrillated and swollen to an a].most gelatinous condition. When paper is m~de from hydrated fibers, a dense non-porous sheet is ormed on the wire. The result~mt sheet is resistant to the penetration of greases and oils because it is composed of nearly continuous well hydrated cellulose. To get the cellulose in this well hydrated form requires a considerable amount of energy.
Glassine manufacturers must subject their stock to refining -for extended periods of time or increase the number of refiners through which the stock must pass. Once the s~ock is hydrated and introduced on the wi/re i~ ~rains very slowly. As a result, machine speeds are ~m~ to between 1~0-500 fpm depending some- ¦
what upon the basis weight of the paper. The stock temperature ~may be elevated with steam to accelerate water removal on the wire¦
IAttempts by glassine manufacturers to use cationic polyelectro-¦ lytes for improving drainage has met only limited success. The.
flocculation of the fibers may improve drainage but this 1~ disruption in formati.on can cause pinholes which reduce oil and ill greaseproof properties of the product.

Il - 16 -l l ~

~q7~6~

il We have now found that when starch fibers are combined ¦~ with cellulose fibers which have been beaten to a degree less than would be required in conventional glassine manufacture, the ¦ resultant mixture has a significantly higher freeness and will drain at lower temperatures in about one-third the time usually required at the elevated temperatures presently used,with higher wet mat solids after pressing and improved drying efficiency relative to the conventional glassine stock. Moreover, the resultant sheet properties of this novel paper exhibits greater internal strength (Z-directional strength), improved oil holdout ¦
properties and greater resistance to the passage of air relative to conventional glassine paper. It is apparent that the reduction of the cellulose refi~ing requirements can result in significant energy savings since the fiber mix need not be ¦ elevated in temperature to achilPve acceptable water removal rates~
as is common practice in conventional glassine manufacture.
Starch fibers may also be employed to provide a more porous sheet which is a property that can be desirable i~ such papers as filter or saturating grades. In prior art methods, reduced refining of cellulose has been found to aid the develop- ~
ment of this property, but does so only at the expense of weaker ¦
web strength~ The incorporation of starch fibers according to the present invention, in conjunction with the cellulose,can result in a more porous sheet structure while maintaining, and ¦ often improving, the required strength properties.
¦ As a further feature of the invention it is possible to ¦ incorporate certain hydrocolloids in the dispersing medium and to extrude the hydrocolloids together with the starch in order to produce a starch-hydrocolloid fiber which may be used in the pape~-I making process of the present invention. In order to achieve ... . . ..

~74~6 11 , il this fiber composition, it is only necessary that the hydrocolloid ¦~ (in minor amounts, i.e. less than 50% by total solids weight), ¦together with the starch portion, be placed in a state of ¦ colloldal dispersion prior ~o contact with the coagulating bath.
I¦Thus, in the case of water-dispersible hydrocolloids such as poly-¦ vinyl alcohol, carboxymethylcellulose, hydrox~ethylcellulose, etc.
it is only necessary to add the hydrocolloid to ~he water in which the starch is dispersed. In the case of other hydrocolloids, such as casein, it will be necessary to causticize the dispersion in order to form the colloidal dispersion required.
As an alternative embodiment of the present invention, water-insoluble additives may be uniformly admixed throughout the starch dispersion and subsequently encapsulated within the resultant starch fiber. Thus, water-insoluble additives, includ- ¦
ing pigments, metallic powders, latices, oils, plasticizers, 'I
microspheres (glass beads, foamed silica or other low density materials either in b~own or unblown fonm~, etc., may be encapsul-¦ated within the s~arch fibers of the invention. In a ~imilarmanner, water-insoluble synthetic polymers or latices, such as polyvinyl acetate, polyacrylonitrile, polystyrene, etc., may be ¦ incorporated within the fiber. It wil~ also be noted that the density of the starch fibers may be varied by incorporating air ¦or other gases in the starch dispersion prior to passing it into the coagulating bath.
It is to be further noted that certain water-soluble solid additives may also be co-extruded with the starch fibers.
In such ~ases, the additive will be dissolved in the aqueous starch dispersion and the coagulating bath which is employed in I¦ forming the starch fibers will be ad~usted by the addition of a ,1 - 18 -~74~6 sufficient quantity of a compatible salt capable of precipitating the additive.
As an exan~le, a commercial rosin size can be added to the starch dispersion and extruded into a coagulating bath containing the functional starch-coagulating salt together with sufficient aluminum sulfate to precipitate the rosin, thereby forming a co-precipitated starch-aluminum rosinate fiber.
The water-insolubility of the starch fibers of the present invention can be further enhanced by the incorporation of conventional cross-linking agents, such as urea-formaldehyde, glyoxal, urea-melamine-formaldehyde, Kymene (registered trademark of Hercules, Inc., Wilmington, Delaware), etc.
These cross-linking agents may be incorporated into the starch dispersion prior to extrusion or may be post-added to the starch fiber.
Generally, any additives employed will be used in amounts less than about 50% by weight of the total solids, however, certain additives including clay and pigments may be incorporated at levels up to about 80% by weight. .
It will be realized that the specific additive selected for incorporation, as well as the amount employed in any of the above-described embodiments, will depend upon what properties are desired in the final fiber. Thus, pigmented fibers show improved opacity and may be inco~)orated by convent~onal methods into the fibrous web with overall improved pigment retention relative to that ohtained by merely adding pigment to a paper stock system. Fire retardant prope~ties may be conveyed to a substrate by incorporating polyvinyl chloride powder and antimony trioxide or other fire retardant chemicals within the starch fiber. Starch fibers containing microspheres may be incorporated into paper webs at high levels of retention. The retention of such spheres enables the production of sheets of high bulk and low weight as compared with cellulose sheets of comparable weight. In conventional sheets containing microspheres, the presence of the microspheres between the fibers has a debonding effect on the fibers and this ~IL09~4~;6 results in a sheet of low strength. In contrast, the sheets of ~ the present invention possess e~cellent strength properties as I the spheres are encapsulated within the starch fibers so that the !
debonding effect of the spheres is minimiæed. The density of the starch fibers, and resultant paper, may also be varied by the incorporation of air or other gases in the starch dispersion prior to passage into the coagulating bath.
Furthermore, by using additive encapsulating fibers it I will be possible, not only to provide a novel process of incorpor-~
¦ ating additives in paper, but also to produce novel effects in ¦ the paper itself. As an e~ample, there~are papermaking machines ¦ that produce a final web which i.s constr~cted of individual layersll ¦ compressed together. Such equipment may be described as cylinder ¦
¦ machines or Fourdriniers with a second down-line headbox or with ¦
multiple headboxes. Machines of this type normally use lower quality fibers for the inner pli.es and quality pulp as the top liner. By utilizing a pigmented starch fiber in the top liner, production of paper web having the surface properties of coated board is possible. In essence a coated board would be produced via a wet-end application process due to the high concentration I I of starch and pigment at the substrate surface. Alternatively, special decorative or construction paper could be manufactured ~ having different colored sides. Dyed fiber could be prepared i¦ at various colors and fed to two diff~rent headbo~es. Such two-colored sided paper is prepared today but requlres the use of surface applications during processing.
One of the ad~antages of the use of water-insoluble synthetic polymers encapsulated within the starch fiber is that i~
permits a high retention in paper and paper-like webs of synthetic 10~7466 ~fibers (such as rayon, acrylic, polyester, nylon or polypropylene) Most of these fibers carry very low surface charge and therefore their retention in commonly used latex binder sys~ems, which rely upon precipitation and fiber deposition techniques, are poor.
Such poor retention can result in low binder efficiency and problems with foam, sticking and accumulation of polymer in ~he system. The resin encapsulating starch fiber insures efficient retention and provides the desired end sheet properties.
An additional feature of the present invention is that the starch fibers may also be employed in the production of dry laid nonwovens of synthetic fibers. In such applications, a web is produced using air as the medium for depositing the fibers on a moving wire. Since the synthetic fibers are not hydrated, bond-ing is inhibited and relatively weak and soft structures are produced. Thus, in order to provide integrity to the web, it is necessary to spray a binder on its surface. In accordance with the present invention, it is possible to blend dry starch fibers with the synthetic fibers. Such a method would be particularly advantageous in the area of disposable nonwovens wherein the biodegradable properties of the starch fiber would be superior to those obtained with the presen~ly employed synthe~ic fiber binders .
¦ As binders those fibers particularly high in amylopectin content are preferred. It is to be noted that the starch fiber may be retained in the final non-woven web or removed therefrom if ¦ desired. If the starch fiber is to be removed, as for example, ¦ from a ceramic web, exposure to ashing conditions sufficient to ¦ burn off the starch fibers provides a suitable means for removal thereof.

. ~1 ,1 l 10 741~6 The starch fibers, filled or unfilled, may be success-fully used alone in the formation of an all-starch paper product or may be utilized in conjunction with all types of cellulosic or non-cellulosic fibers. The hardwood or softwood cellulosic fibers whic~ may be used include blff~ached and unbleached sulfate (kraft), bleached and unbleached sulfite, bleached and unbleached soda, neutral sulfite, semi-chemical groundwood, chemi-groundwood I
and any combination of these fibers. These dff~signations refer to ¦
wood pulp fibers which have been prepared by means of a variety of processes which are conventionally used in the pulp and paper industry. In addition, synthetic cellulosic ibers of the viscose rayon or regenerated cel.lulose type can be used, as well as recycled waste papers from va~rious sources. Similarly, ceramic fibers, glass, asbestos or other inorganic ~ibrous materials may be employed in conjunction with the starch fibers of the invention.
~ue to the water-insensitive nature of the starch fibers 11 employed herein, the fibers disperse readily to form stable dis-¦¦ persions which may be used in ordinary papermaking operations 20 1! without adding surfactants. This permits the use of the fibers i~
Il paper making operations and machinery without modification of the ¦¦ usual processing conditions. Thus, fibers may be added to the beater or a blending chest into the head bo~ onto the screen of a Fourdrinier machine and from there the sheet may be carried to the wet press through drier rolls, calenders, and woundup as a sheet without modifying substantially the normal operating f characteristics of the machines as used for making cellulose ~ --1I paper. It will bff~ appreciated that in the case of paper made fll entirely from starch fibers, it may be desirable to place the web 1¦ between nylon mesh screens or to blot the web drier than is common in conventional operations in order to prevent s~icking of~

f~

109, 46(i the fibers in the drier.
~I Furthermore, the papermaking operations may be integrat-¦
11 ed with the starch fiber production operation by employing the slurry containing the fibers as they are precipitated. It is also possible to form shaped articles directly from thick fiber slurries by slush-molding in patterns or molds.
l It will be obvious to those skilled in the art that the ¦ specific starch employed and the amount of starch fiber used I will vary according to the desired quality paper. Thus, we have ¦ found that the choice of the proper type of starch makes it 1 possible to achieve selected sheet properties previously achieved ¦ only by hydrating and fibrillating wood pulp to various degrees of freeness. Specifically, it has been necessary to lightly refine pulp (650 ml. CSF) in unbleached kraft linerboard appli-¦ cations to insure rapid water removal rates while maintai.ning I ¦ high processing speeds. The degree of refining is controlled also by the internal bond strength of the product being produced.
~he introduction of starch fiber enables rapid water removal and maintenance of production speed but still insures ~he development internal bond strength. Glassine papers are frequently processed ¦~ from pulp that has been refined extensively ~less than 50 ml. CSF)~
¦¦ We have now found that glassine type papers can be produced by reducing the cellulose refining in half by adding as little as 1 15~/o starch fiber. Alternatively, for papers which require even I ¦ lower opacity and porosity, it will be preferable to use starch ¦¦ fibers in larger quantities, i.e. about 50% or more.
The starch fiber containing papers of the present ¦ invention may be manufactured together with any commonly employed¦
internal additives such as sizes, wet and dry ~strength additives, ~g7~6 ¦¦ etc. or may be surface treated by coating, spraying or saturating ~i as is conventional in the trade.
The starch fiber-containing paper of the present invention can be repulped and recycled. The ability of the starch!
fiber itself to retain its fiber integrity during a repulping process is influenced by the starch fibPr type (higher amylose ;~
starches repuLp more readily) and the repulping conditions to ; which it is subjected. Generally, the lower the usage of basic chemicals and elevated temperatures during the repulping operation~, the more avorable the recycling of the starch fiber. I
The following examples will serve to more fully explain !
the various aspects and embodiments of the present invention.
In the examples, all parts are by weight unless otherwise indlcated.

A slurry was prepared by mixing a naturally occurring unmodified starch composed of 70% amylose and 30% amylopectin in water at a level of 5%, by weight, solid starch and then addin~
with agitation, a 25~/o solids solution of sodium hydroxide sufficient to provide a level of 40% caustic on the starch on a dry basis. This mixture was agitated until a dispersion of the starch granules was obtained.
¦ The resultant dispersion was introduced at a pressure ¦ o~ 703 gms/sq. cm. into an agitated co~gulation bath consisting of 28% solids ammonium suLfate through a spinnerette containing 100 apertures, each of which had a diameter of 70.2 microns, at an angle of 90 to the moving salt solution. The resultant fibers Il - 24 -10~466 were collected on a wire mesh screen, washed free of salt and r~ ~ recollected . The fibers possessed an average diameter of 65 i ~ ¦ microns, an average length of approximately 4 mm~.and a final solids content of 23.5%, by weight.
A series of handsheets were prepared on a ~oble and Wood sheet mold, from varying levels of bleached softwood pulp ~BSWK) in com~ination with the above prepared fibers. The sheets were dried on the Noble and Wood dryer at a drum tempera~ure of 1,?~1C. and then allowed to condition for a period of 24 hours under constant 22C. temperature and 55% relative humidity.
Table I summarizes the pertinent sheet making conditions and test data.
TABI,E I
Fiber Blend Basis Can~a~ Sheffield Z-direction-~ Starch Weight Standarcl 2 al 3 BSWK Fiber gms7sq.m. Freeness (ml)(l) Porosity( )_Strength( ) 100 0 78.~ 5~4 218 596 82.6 540 1~2 630 ~` 75 25 80.4 475 7~ 846 77.9 367 28 1050~
77.1 250 16 1050+
(1) Measure of the drainage of water from the pulp through a wire screen. Unbeaten pulps have a high freeness relative to low freeness of well beaten pulps. TAPPI test T227-M~58.

(2) This test measures the air resistance of paper. I
Sp~cifically, it measures the volume of air that can be passed through a specific sample area at a given pressure and time. The higher the test value, the 1 30 more porous the sheet (Used 7.62 cm. I.D. ring;
values are unitless).
(3~ The Scott Internal Bond Tester measures the Z-directional strength of paper. This method is designed to determine the average force in joules per square meter required to separate a paper ¦ specimen. TAPPI RC-305.

~
i ~ 746~ 1 The results shown in the Table indicate that the presence ~of increasing amounts of this particular starch fiber prepared at a 5% solids dispersion level extends the water holding capabilities of the fiber blend and produces a sheet that is less porous and of higher Z-directional strength than a lOOV/o cellulose sheet.

Starch fibers were produced using the materials and method employed in Example 1, however, after the final wash, ~he fibers were dispersed in ethanol solution, collected and allowed to dry. The fibers were then combined with cellulose and hand-sheets prepared as in Example 1. Tests performed on these hand-sheets show that the dried fiber provided performance character-istics comparable to those obtained by the moist fibrous products of Example 1.

¦ Starch fibers were produced using the materials and ¦methods employed in Example 1, however, the starch solids concen-¦tration of the starch dispersion was 20% and the final solids ¦level in the fiber was 38%. Handsheets were prepared and tested as in Example 1. The results are shown in Table II.
TABLE II
~Fiber Blend Basis Canadian Starch Weight Standard Sheffield Z-directional I
BSWK Fiber _gms/sq~m. Freeness ~ml2 Porosity Strength _ 100 0 86.2 505 158 538 82.9 545 333 527 82.9 595 1,215 565 l, l~ 50 50 79.7 676 8,645 ~47 1, 11 25 75 79.7 81~50,496 1035+

- 2~ -l~q74~6 ~ As illustra~ed in Table II, the use of starch fibers ¦ prepared from a higher solids level dispersion resulted in an ¦ increase in the water releasing ability of the furnish ~i.e., ¦ the freeness), and provided a more porous sheet of greater porosity and Z-directional strength than a 100~/o cellulose sheet.
¦ It is to be noted that this starch solids level produced freeness ¦ and porosity values which distinctly contrast from the values ¦ obtained in Example 1 wherein a 5% starch solids level was used ¦ to produce fibers. This comparison illustrates the adaptability ¦ of the method of the present invention to the production of a variety of properties in the final paper product (e.g., the level ¦ of porosity required in a glassine stock versus that required in ¦ filter paper). It is also to b~ noted that in both Example 1 and ¦ 3, the strength of the paper wa~ improved by the use of starch I ¦ fibers.
I EXAMPLE ~
¦ Starch fibers were prepared using a 20~/~ solids starch dispersion as in Example 3 except that after washing they were reslurried in ethanol, recovered and dried. Handsheets were ¦ prepared and tested and showed that the dried fiber provided ¦ performance characteristics comparable to those obtained using ¦ the moist fibrous product of Example 3.
¦ E~AMPLE 5 This ex~mple illustrates the use of fibers formed from I ~ a variety of starch bases in the production of paper according ~ to the present invention.
; I Starch fibers were prepared and combined with cellulose i using the methods described in Example 1. The cellulose portion 74~i , ' il was beaten to a Canadian Standard Freeness of 645 ml prior to ¦ being blended wi~h the starch fiber and the basis weight of the ,I handsheets was maintained at 97.5 gms/sq. m.
!~ !
TABLE III
Fiber Blend 1 2 direct- 4 Starch Starch Fiber Tensile Mullen ional3 MIT
BSWK Fiber Base gms/cm2 gms/cm2 Strength Fold l 100 0 - - 10~0.55 4429.40 14~ 552 1 90 10 Aminoethyl- 1462.4 6679.26 903 1,210 ated corn " " 1476.46 5624.641050+ 1,2~0 Waxy maize 1525.68 6679.26 853 1,670 " " 14:l3.19 5062.171050+ 1,125 Unmodified 1553.80 5484.02 567 1,340 corn " " 1293.66 3445.091050+ 1,245 Hybrid corn 165~.26 5273.10 62~ 1,420 I containing 2n 1 70/O amylose 1 70 3~ " 1652.23 4148.171050~ 1,390 I ~ 90 10 Amylose 1545.99 5413.71 68~ 1,433 " 1652.23 4780.9~1050+ 1,395 TAPPI method T404-5s 66 - Determines the tensile breaking strength in pounds per inch (converted to metric units).
TAPPI method T403-ts-63 The hydrostatic pressure in pounds per sq. inch (converted) required to ruptur~ the paper when the pressure is applied at a controlled I increasing rate through a rubber diaphragm to a circular area 3048 cm. in diameter.
3As deined in Example 1.
~ 4TAPPI method T423M-S0. The number of folds that the test ¦ specimen can endure prior to breaking using a fold tester of the type developed at the Massachusetts Institute of l Technology.
¦l As shown in Table III the addition of any of the variou~
! starch fibers may be used to improve particular strength properties of the paper when compared with the 100% cellulose fiber sheet.

l l 10~74$6 This example illustra~es two methods for the production ~¦of a 100% starch fiber sheet. I
¦Method A. Six grams of unmodified corn starch fibers were slurried in 1 liter of water. The fibers were agitated with a paddle stirrer until a uniform mixture was obtained. A handsheet was formed on the Noble and Wood sheet former that had been fitted wi~
a 100 mesh wire screen. The resultant fibrous web was removed fro~
l the screen and blotters and subjected to a series of pressing operations: 3 presses at 7030.~ gms/cm2 and 3 presses at 28123.2 gms/cm with changing of the blotters between pressing operations.
The resulting mat solids was 70%. The web was then placed between blotters and dried on the Noble and ~ood dryer at 120.1C. The resultant rigid self-supporting paper-like product had a basis weight of 145 gms/sq.m.
Method B. Starch fibers were processed as described in Method A
and the resultant web mat was subjected to a pressing sequence of:
2 presses at 7030.8 gms/cm2 and 2 presses at 14061.6 gms/cm2 with ¦ changing of the blotters between pressing operations such that th~
l¦resultant wet mat solids was 50~/O. The web was placed between two nylon wire screens and passed through the ~oble and Wood dryer at 120.1~C. The resultant rigid self-supporting paper-like web had a basis weight of 145 gms/sq.m.

Handsheets were prepared by the method of Examplel excep~
¦ that commercially unmodified refined glassine stock at two free-ness levels was combined with corn starch fibers. The cellulose pulp was obtained from two points in the refinery operation such ¦¦that one portion had a Schopper Reigler freeness of 350 ml. while lOg~466 ¦Ithe fully refined portion had a 160 ml. freeness. Starch fiber ~was substituted at the 20% level and all handsheets were prepared ¦'at a basis weight of 48.8 gms/m2. The sheets were then surface ~sized on a laboratory size press fitted with rubber rolls using a 1% solids polyvinyl acetate solution.(available from Air Product and Chemicals under the tradename Vinol 165) main~ained at 60C.
such that a 1% pick-up of polyvinyl acetate was obtained. The ¦sheets were then conditioned under constant temperature of 20C.
and room humidity 55% for 24 hours ~rior to being tested for ` kesl~stance using TAPPI standard T~54-ts-66. The results of the terpentine testing are shown in Table IV.
TABLE IV
Cellulose ¦S.R. Starch Sheet Mold Stock Terpentine ¦Freeness* Parts Fiber Drain Time Temp. C. _Test _ 350 ml 100 - 21.3 secs. 2~ 855 secs.
; 350 ml 8~ 20 19.9 secs. 24 1800+ secs.
160 ml 100 - - 62.1 secs. 60` 1~00+ secs.
Schopper-Riegler Freeness Tester supplied by Testing Machines, Inc.

The use of starch fiber in combination with partially ¦ refined pulp increased the terpentine resistance of that pulp alone and matched the resistance of a fully r~fined glassine stock~
In addition, the refining reduction enabled drain time reductions by a factor of almost 3 fold at significantly lower temperatures.
Thus while it is necessary to elevate conventional stock to l temperatures of about 60C. in order to obtain drainage in 62 ! seconds, drainage in about 20 seconds can be achieved at temper-atures of 24C. with no loss in desirable properties using the 30 1¦ method of the present invention. The improved drainage can result ~in faster machine speeds and efficiency of production while realiz~
¦¦ing considerable savings in energy due to reduced refining and , - 30 -Il l ~L0~7466 ¦stock temperatures.

EX~MPLES g ¦ This example illustrates the improvement in properties ¦obtainable by the incorporation in cellulose pulp of starch fibers ¦containing polymeric m~crospheres.
¦ Starch fibers were prepared using the method of Example:
¦but also incorporating înto the starch dispersion, prior to fiber ¦formation, 8.5% microspheres (available from Dow Chemical I as XD 6850). The fibers were then incorporated into handsheets ¦in combination with cellulose wood pulp using the method described I ¦in Example 1. In all cases, the Canadian Standard Freeness value l was 730 ml. for the cellulose componPnt. The results o testing ¦ are shown in Table V. As a means of comparison, samples were also prepared in which the microspheres were added directly to the paper pulp as is conventional practice in the industry.
TABLE ~ 2 Fiber Blend % Spheres Basis 1 Taber Z-dir~ct-; I Starch In Weight Caliper Stiff- ional~
I BSWK Fiber Added Sheet ~ms/sq.m. lxlO~ cm. ness Stren~th 1 100 0 0 0 97.6 18.79 3.7 111 100 0 0 0 130.1 24.38 6.3 137 100 0 1.8 .86 97.~ 24.39 6.6 103 100 0 2.0 1.0 97.6 25.40 7.1 90 5 .43 .43 97.6 23.11 5.0 168 10 .86 .86 97.6 26.16 6.3 206 ~5 151.29 1.29 97.6 28.45 7.5 237 Thickness of paper expressed in thousandths of a centimeter TAPPI Method T451-M-60 3As defined in Example 1.

.. , ~ .... : . .

1 V~74~i6 As illustrated in Table V, the introduction of the ¦microspheres by either of the methods substantially improved both ¦
¦the caliper and stiffness of the paper product. In this regard, it was possible by the addition of microspheres to achieve the caliper and stiffness of 130g/sq.m. basis weight at a level of only 97.6 g/sq.m. The weight saving, both in amount of fiber required and in related costs recognized after produc~ion of the paper (e.g. mailing), are readily recognizable.
When the o~her properties obtained from the microsphere ¦
containing sheets were compared, it was found that retention of theexternally added spheres was approximately 50V/o of the amount initially added while the retention was approximately 100% for those added in the encapsulated fibers. Moreover, there was a decrease in strength and evidence of non-uniform distribution of the spheres (with a greater con~entration on the felt side) in the case of the externally added spheres while these factors were not presen~ in the case of the starch encapsu~ated spher~s. Thus, the increase in~caliper and stiffness observed using the conventio~-ally employed external addition of the spheres was obtained only at the expense of decreasing internal bond strength of the paper, ¦while introducing the spheres within the starch fiber insured their retention with the sheet while increasing the internal bond strength in addition to providing the desired stiffness and calipe~ .
increases.
¦ E~AMPLE ~
This example illustrates the results obtained using three methods for incorporating clay in paper production.
Handsheets were prepared using methods similar ~o those l ll -. :

described in Example 1. The handsheets were prepared so as to incorporate a number two coating grade cl~ in the final sheet ¦ during the formation process. The incorporation of the clay into ¦ the handsheets was accomplished in three different manners:
1) by conventionally slurrying the pigment with the pulp fibers, 2) by incorporating starch fibers pr~pared according to Example 1 but containing 80% clay and 20% starch, and 3) using a combination ¦ of methods (1) and (2). In all cases the basis weight of the l sheet was 97.6 g/sq.m.
¦ The physical and optical properties of the resulting ¦ paper sheets are shown in Table VI.
I ¦ TABLE VI
l Conventional I Addition_ Starch Fiber Z-direction-~/0 Cellu- % % ~~~~~~~~~~ Opaç- Ten~- al(3) lose Clay TiO2 Starch Clay ity~l) ile~2) Strength 100 0 0 0 0 85.9991.34 302 87.2 12`.8 0 0 0 92.0625.74 113 1 75.2 0 0 5.0 19.8 88.91371.00 351 201 68.4 6.8 0 5.0 19.8 90.5864.79 256 ; 1 72.1 0 4.5 4.7 18.7 94.1850.73 233 (l)TAPPI method T425-m-60.Expressed in percent and defined as 100 times the ratio of the diffuse reflectance of a specimen backed with a blank of I no more than .005 reflectance of the same specimen ¦ backed with a white body having an absolute reflectance of 0.89. The higher the value the more opaque the paper.
l ( )Defined in Example 5.
(3~Defined in Example 1.

As illustrated in Table VI, incorporating the pigment ¦within the starch fiber enabled higher pigment loadings and ~¦strength properties when compared to conventional pigment loading lOq~4~6 techniques. Thus, when 12.8% clay was added to cellulose pulp ~ using conventional techniques, the tensile and 7-directional I strength decreased. In contrast, when 19.8% olay was added in the form of encapsula~ed starch fibers (a total addition of 24~8~/o) ) the tensile and Z-directional strength improved. It is ~further shown that the reduction in opacity obtained by use of ¦~the clay-encapsulated fiber can be compensated for by the ¦external addition of a small amount of clay or of titanium dioxide ¦ EXAMPLE 10 l This example illustrates the superior retention ability ¦of the starch fibers as used in the method vf the present ¦invention.
¦ Bleached softwood kraEt was beaten to a freeness of 500 ¦ml. Canadian Standard and divided into three portions. To one ¦portion, a No. 2 coating grade clay was added and the resultant ¦blend agitated until the pigment was uniformly distributed throughout the pulp fibers. Another portion was treated in the ¦same manner except that Natron 86 (a trademark of ~ational Starch !
l and Chemical Corporation), a retention aid, was addedO To the ¦remaining portion of the pulp, starch fibers containing clay encapsulated therein (50% starch and 50~/O clay~ were added and ¦the fiber blend was agitated until uniform distribution was obtained. Handsheets were prepared by a method similar to ¦Example 1 and the sheets evaluated for clay content and percent ¦ retention. The results are shown in Teble VII.

Il ~

1.

lOq74~

TABLE VII
Fiber Blend BSWK Starch Fiber (50/O Clay) Clay _ Retention Aid % Clay Retention 90 0 10 0.02% 35 As illustrated in Table VII, the retention of clay was highest when the clay was encapsulated in the starch fiber pursuant to the present invention.

The following example illustrates the use of starch fibers for their binding properties in the production of a multi-ply sheet.
Two-ply handsheets were prepared on a Noble and Wood sheet former from bleachedsoftwood kraft that had been beaten to a 500 ml. Canadian Standard Freeness. To achieve a final basis weight of 146 gms. per square meter, two plies (each approximately!
73 gms. per square meter) were prepared and wet pressed together Iprior ~o drying on the Noble and Wood drier at 121C. The control ¦handsheet contained 100% cellulose in both plies, while the test handsheet had 20~Jo of ~he cellulose in the top ply replaced by starch fiber. The bond between the plies was tested using the Scott Internal Bond tester and the results shown in Table VIII.
TABLE VIII
Fiber Blend Z-direct~onal ¦Bottom Ply - Top Ply _ _ _ Stren~th j100% Cellulose - 100~/o cellulose 119.7 ¦ 100% Cellulose - 80% cellulose and 20% Starch Fiber 197.4 ¦ (l)Defined in Example 1.

_ ~5 _ 9 ~ 79~j~

As shown in Table VIII the presence of the starch fiber l increased the bond strength between the pliPs of the final shee~s.
; ¦ EXAMPLE 12 This example shows the production of paper containing a variety of additives incorporated by the addition of starch fibers containing the encapsulated additives.
l In a manner similar to that described in Example 8, ¦ additives were encapsulated within the starch fibers and used to ¦ form handsheets having a given percentage of the starch fibers as ¦ indicated in Table IX.
TABLE IX
Additive% A,dditive in % Addition of Starch l Star~h Fiber _ Fibers in Pulp I __ TiO2 25 20 ¦ CaC03 25 20 j Al powder 25 20 Carbon black 25 20 Fibran 68 5 10 I (A trademark for a sizing agent available from ¦ National Starch and Chemical Corporation~
Pexol 200 5 10 (A trademark for a sizing agent available from ¦ Hercules Powder Co.) A l:l blend of 50 50 I antimony trioxide ¦ and vinyl chloride ¦ homopolymer (fire retardant) I I r ;s ~ d ~ch l ~r c:~
57 ~0 I propyl phosphate (fire retardant) In all cases, the additives were retained at al high level in the fînal paper product and imparted their characteristic property thereto.
Il I
~l - 3~ -1~97q~6 This example illustrates the use of the sta~h fibers as a means to incorporate latex binders in a nonwoven web of synthetic fibexs.
A dispersion of rayon fibers (0.635 cm, 1.5 denier) and polyester fibers (0.635 cm, 1.5 denier) were prepaxed at 0.1%
solids in sepaxate containexs.
A 100% staxch fiber product as well as a starch fiber that contained 20% on a weight basis of encapsulated latex,vinyl acetate/butyl acrylate copolymer,were added as binders in amounts such that the final fiber blend would contain 25% of the starch fiber products. Handsheets were prepared on a Noble and Wood sheet former at a basis weight of 65 gms. per square meter using methods similar to those described in Example 1. The webs were tested to determine tensile stren~th improvement and the results summarized in Table X.
TABLE X
Synthetic Tensile(l) i ¦ Starch Fiber Description Bindex Level Fiber (gms/cm2) l None (control) - Ra~on *
¦ None (contxol) - Polyester *
¦100% Starch 25% Rayon 710.11 ¦ 100% Starch 25% Polyester 217.95 80% Starch - 20% latex 25% Rayon 984.31 80% Starch - 20% latex 25% Polyester 135.69 ¦ Sheet did not possess sufficient integrity to measure tensile (l)Defined in Example 5.

,:1 ,~ ,... .

10~7466 ! As shown in Table X, webs prepared using both the ¦starch fibers and the starch-latex fibers as binders possessed ¦superior tensile strength. In contrast, control webs prepared ¦from 100% synthetic fiber did not possess sufficient integrity ¦to even be handled for testing. It is noted that the particular latex employed increased the tensile strength of the rayon web while decreasing the strength of the polyester web compared to the 100% starch fiber. This illustrates the necessity of choos-ing the proper latex for the synthetic fiber being treated.

This example illustrates the use of starch fibers as binders with ceramic fibers. The example also shows that the starch fiber binders may be removed after formation of the web resulting in the production of a 100% ceramic ~iber sheet.
A 3% solids ce~ramic iber slurry was prepared in a Waring Blender and agitated for 1 minute after 0. 2~/o NaOH (dry basis based on the weight of the fiber) was added to serve as a dispersing agent. The fiber mix was then transferred to a con-tainer that was equipped with a paddle stirrer and a pre-determine~
amount of starch fiber added from a 1% solids mix. After mixing I the blend for a period of 5 minutes, handsheets were prepared at 407 gms/square meter basis weight, on the Noble and Wood sheet former. As a control, a ceramic sheet was made without the addi-tion of any starch fibers. All sheets were subjected to strength tests with the results shown in Table XI.
.` ~
r~d~ûrk . I
~ - 38 -.' :; .. .. : ., , ~; .

1(3~7466 i! TABLE XI
ll i i Basis Weight Tensil2e(l) I Starch Fiber gms/sq. meter gms/cm I 407.5 __*
,1 5% 407.5 3.52 ~ 10% 407.5 20.39 I
l Sheet did not possess sufficient integrity to I measure tensile l (l)Defined in Example 5.

¦ The sheets containing the starch fibers were then r~ placed in a kiln malntaintained at a ~ sufficient to ash the starch fibers and fuse t:he ceramic fibers. A
well bonded ceramic web was thereby produced.

Two ply handsheets containing 10% TiO2 on the final sheet weight of approximately 145 gms/sq.m. were prepared. In the control ha~dshee~s, TiO2 was added in the conventional manner by dispersing the pigment with those unbleached kraft fibers which comprised the top liner. In the remaining handsheets, 20% TiO2 encapsulated starch fiber on a weight basis was added in sufficient quantity to the top liner to provide 10% TiO2 on the final sheet weight.
The final sheet was constructed from two plies, each prepared separately on the Noble and Wood sheet mold at ¦ approximately 72.5 gms/sq.m., removed from the wire and pressed ¦ together in the wet mat state at 14061.6 gms/cm2. The sheets ¦were then drîed on the Noble and Wood drier at 121C. Brightness readings were taken on the top liner side in accordance with 1097~

I,ITAPPI standard R452-M-58 wi~h the results indicated in Table XII.
I TABLE XII
I Sample Sheet Top Liner Brightness i Control 26.2 Starch Fiber 30.1 The results shown in Table XII indicate that the handsheets prepared using the TiO2 encapsulated starch fibers had ¦superior properties to those prepared using conventional methods.
¦ The preferred embodiments of the present invention ¦having been described above, various modifications and improvement~ , thereon will now become readily apparent to those skilled in the ¦art. Accordingly, the spirit and scope of the present invention ¦is to be limited not by the foregoing disclosure, but only by the appended claims.

- ~0 -!

Claims (20)

--The embodiments of the invention in which an exclusive property or privilege is claimed or defined as follows:--

1. In a process for manufacturing paper and paperboard comprising the steps of introducing an aqueous slurry of a fibrous pulp material onto a screen in such a manner that the water is removed thereby forming a sheet of consolidated fibers which, upon pressing and drying, yields the final paper product, the improvement comprising the step of employing starch in an amount of from 1 to 100% by weight of the pulp in the form of water-insensitive starch fibers of 10 to 500 microns in diameter, said fibers being produced by extruding a thread-like stream of a colloidal dispersion of starch, at 5-40% by weight solids, into a moving coagulating bath comprising an aqueous solution of a coagulating salt selected from the group consisting of ammonium sulfate, ammonium sulfamate, mono-basic ammonium phosphate, di-basic ammonium phosphate and mixtures thereof, said solution containing said coagulating salt in an amount at least sufficient to coagulate said starch.

2. The process of Claim 1 wherein said starch fibers are prepared from corn starch or waxy maize starch.

3. The process of Claim 1 wherein said starch fibers are prepared from high amylose starch.

4. The process of Claim 1 wherein said starch fibers are prepared from cationically derivatized starches.

5. The process of Claim 1 wherein said starch fibers are prepared from ether or ester derivatives of starch.

6. The process of Claim 1 wherein the colloidal starch dispersion additionally includes clay or pigment replacing said starch in an amount up to 80% by weight.

7. The process of Claim 1 wherein the colloidal starch dispersion additionally includes a water-insoluble additive selected from the group consisting of microspheres, metallic powders,lattices, oils, and plasticizers replacing said starch in an amount less than 50% by weight.

8. The process of Claim 1 wherein said colloidal starch dispersion additionally includes a dispersed hydrocolloid in an amount less than 50%
by weight of said starch.

9. The process of Claim 1 wherein said starch fibers have a length of 0.1 to 3.0 mm.

10. The process of Claim 1 wherein the remaining fibrous pulp material is substantially in the form of wood cellulose.

11. The process of Claim 1 wherein the remaining fibrous pulp material is substantially in the form of fibers selected from the group consisting of polyester fibers, rayon fibers, ceramic fibers, glass fibers and asbestos fibers.

12. Paper and paperboard compositions comprising a blend, on a weight basis, of 0-99% papermaking cellulose pulp fibers and 1-100% water-insensitive starch fibers of 10 to 500 microns in diameter produced by extruding a thread-like stream of a colloidal dispersion of starch, at 5-40% by weight solids, into a moving coagulating bath comprising an aqueous solution of a coagulating salt selected from the group consisting of ammonium sulfate, ammonium sulfamate, mono-basic ammonium phosphate, di-basic ammonium phosphate and mixtures thereof, said solution containing said coagulating salt in an amount at least sufficient to coagulate said starch.

13. The paper and paperboard compositions of Claim 12 wherein at least one water-insoluble additive is encapsulated within said starch fiber.

14. A method for incorporating water-insoluble additives within the pulp of a conventional papermaking system comprising the steps of thoroughly dispersing at least one water-insoluble additive in a colloidal dispersion of starch, said starch being present in an amount of 5-40% by weight solids, and precipitating said dispersion by extruding a thread-like stream of said dispersion into a moving coagulating bath comprising an aqueous solution of a coagulating salt selected from the group consisting of ammonium sulfate, ammonium sulfamate, mono-basic ammonium phosphate, di-basic ammonium phosphate and mixtures thereof, said solution containing said coagulating salt in an amount at least sufficient to coagulate said starch so as to form water-insensitive starch fibers encapsulating said additive; and subsequently using the resulting starch fibers as components in a papermaking pulp system.

15. In a process for manufacturing paper and paperboard comprising the steps of introducing an aqueous slurry of a fibrous pulp material onto a screen in such a manner that the water is removed thereby forming a sheet of consolidated fibers which, upon pressing and drying, yields the final paper product, the improvement comprising the step of replacing from 1 to 100% by weight of said pulp material with water-insensitive starch fibers of 10 to 500 microns in diameter, said fibers being produced by extruding a thread-like stream of a colloidal dispersion containing starch at 5-40% by weight solids, wherein said starch is present in an amount more than 50% by weight of the fiber forming ingredient, into a moving coagulating bath comprising an aqueous solution of a coagulating salt selected from the group consisting of ammonium sulfate, ammonium sulfamate, mono-basic ammonium phosphate, di-basic ammonium phosphate and mixtures thereof, the solution containing the coagulating salt in an amount at least sufficient to coagulate the starch, said starch fibers further characterized in retaining fiber integrity when dispersed in an aqueous medium.

16. A process for incorporating water-insoluble additives within an aqueous papermaking slurry of a conventional papermaking system comprising the steps of thoroughly dispersing at least one water-insoluble additive in a colloidal dispersion containing starch at 5-40% by weight solids, wherein said starch is present in an amount more than 50% by weight of the fiber forming ingredient and precipitating said dispersion by extruding a thread-like stream of the dispersion into a moving coagulating bath com-prising an aqueous solution of a coagulating salt selected from the group consisting of ammonium sulfate, ammonium sulfamate, mono-basic ammonium phosphate, di-basic ammonium phosphate and mixtures thereof, the solution containing the coagulating salt in an amount at least sufficient to coagulate the starch so as to form water-insensitive starch fibers encapsulating said additive; and subsequently using the resulting starch fibers as a component in a papermaking pulp system, said starch fibers further characterized in retaining fiber integrity when dispersed in an aqueous medium.

17. The process of Claim 15 wherein 1-50% by weight of the fibrous pulp is replaced by water-insensitive starch fibers.

18. The process of Claim 17, wherein at least a portion of said unreplaced fibrous pulp has been refined to a Schopper Reigler freeness of between about 350 ml. to 160 ml., and said final paper product having glassine greaseproof properties.

19. The paper or paperboard composition produced by the process of Claim 15, wherein 1-50% by weight of the papermaking cellulose pulp fibers is replaced by water-insensitive starch fibers.

20. The paper or paperboard composition produced by the process of Claim 15, wherein 1-50% by weight of the papermaking cellulose pulp fibers is replaced by water-insensitive starch fibers and at least a portion of said unreplaced papermaking cellulose pulp fibers has been refined to a Schopper Reigler freeness of between about 350 ml. to 160 ml.