Fibers and pulps for papermaking based on chemical combination of poly(acrylate-co-itaconate), polyol and cellulosic fiber

Disclosed is a fiber comprising, chemically bonded together, (a) a conventional cellulosic fiber, such as a Kraft fiber or a chemithermomechanical pulp fiber; (b) poly(acrylate-co-itaconate), such as the acid form of a poly(acrylate-co-itaconate) comprising 90-95 mole % acrylate and 5-10 mole % itaconate having weight average molecular weight of about 600,000-900,000; and (c) a polyol, such as polyethylene glycol; also disclosed are methods for making such fibers, especially evaporatively depositing an intimate mixture of the copolymer and polyol on the fiber followed by thermally crosslinking at specific temperatures for limited periods; absorbent paper which can be made by wet-laying the fiber, especially in admixture with conventional fiber; and derivative paper structures, such as multi-ply disposable absorbent towels.

FIELD OF THE INVENTION 
This invention relates to fibers, such as Kraft fibers, which are 
chemically modified with certain poly(arcylate-co-itaconate) copolymers 
and polyols; to chemical methods for making such fibers; to improved paper 
which can be made by wet-laying the fibers, especially as a pulp in 
admixture with conventional papermaking pulps; and to derivative paper 
structures, such as multi-ply disposable absorbent towels. 
BACKGROUND OF THE INVENTION 
The is an ongoing interest in the development of absorbent articles such as 
paper towels. Disposable paper towels are widely used in the home for 
wiping spills, especially of water or watery liquids; for cleaning 
work-surfaces such as those of the kitchen and bathroom; for food 
preparation and handling; or for cleaning glass. More generally, absorbent 
papers are sometimes incorporated into other absorbent articles, such as 
dressings, catamenials and disposable diapers. 
Manufacturing, more specifically sheet-forming, processes for paper are 
well-established in commerce. Papermaking machinery is very 
capital-intensive, and as a result, improvements in absorbent paper which 
do not require any major change in, or complication of, the paper-forming 
process tend to be highly appreciated. The processes of major importance 
include air-laying and wet-laying. 
In outline, the latter process involves filtering a dilute dispersion of 
fibers onto a mesh (usually termed a Fourdrinier wire) and drying the 
resulting web. There is a large installed base of manufacturing equipment 
using continuous, high-speed machinery based on the wet-laying technique, 
representing considerable investment. 
Conventional papermaking fibers suitable for wet-laying papermaking are 
cellulosic fibers which disperse well and can readily be filtered and 
dried. They typically absorb relatively small amounts of water, of the 
order of a few grams per gram of bone dry fiber. 
The simplest notion for improving the absorbency of paper involves adding 
thereto a highly water-absorbent material, such as one of the gel-forming 
polycarboxylate polymers, which are well-known in the art. Very high 
absorbencies are possible, of the order of hundreds of grams of water per 
gram of polymer. Such materials have found particular utility as 
disposable diaper "superabsorbents". 
Superabsorbents are however inherently very difficult to handle in a 
wet-laying process. Thus they tend to disintegrate under the relatively 
high shear forces involved in wet-laying papermaking. Moreover, they are 
difficult to filter, tending to block the Fourdrinier wire; and once 
deposited, they are very difficult to dry. The final product tends to be 
stiff and may not rewet to an acceptable degree when in use. 
Applying the above-identified simple absorbency-improving notion to 
processes other than wet-laying has led to the development of a laminated 
structure or "sandwich" having outer plies of conventional paper and an 
inner layer consisting essentially of superabsorbent. However, the 
superabsorbent tends to leak out from the product paper structure, 
especially through pinholes or when the paper structure is torn. Slippery, 
gel-like material is released, which is a serious aesthetic disadvantage. 
The deficiencies of the above approaches suggest a need to consider more 
than just the absolute magnitude of the absorbency which can be had from a 
particular paper additive. Thus, although absorbency is of primary 
importance, other requirements, such as ease of manufacture and product 
aesthetics, must be met. In addition, as distinct from water-absorbing 
capacity, another problem which has been identified in the context of 
absorbent structures has to do with rate of water uptake, in technical 
terms, "wicking rate". Wicking rate is particularly important in a 
disposable paper towel which must quickly absorb a spill. 
In principle, it is possible to suggest making absorbent paper by 
wet-laying an improved absorbent fiber (as distinct from particulate 
superabsorbents on one hand or conventional papermaking fibers on the 
other). However it would seem that these reports of "absorbent fibers". 
However it would seem that these often involve mere physical coating of a 
fiber, such as processes involving precipitating absorbent polymers onto 
fibers or polymerizing monomers such as acrylic acid and 
methylenebisacrylamide in the presence of a fiber. In such situations, the 
chemical means are not present to covalently attach the polymer to the 
fiber. In consequence, the coating may not survive the shear forces 
involved in typical wet-laying operations, and may come off, the result 
being wire-blocking and/or drying problems similar to those mentioned 
above. 
Grafted fibers are also well-known. Typical of grafted fibers are those 
made by graft copolymerizing methyl acrylate and cellulosic fibers in the 
presence of an appropriate catalyst such as cerium (IV) ammonium nitrate 
followed by hydrolyzing to the absorbent form. Absorbent grafted fibers 
are often not as strong as might be desired for wet-laying papermaking, 
since the low molecular weight monomer used in the preparation is capable 
of penetrating the fiber, polymerizing in the interior, so that when 
hydrolyzed and exposed to water, the fiber "balloons" internally and can 
easily shatter. 
Various highly absorbent polymers have been extruded, and the extrudates 
have sometimes been termed "fibers". However, these materials are in fact 
not fibers in the usual sense of cellulosic papermaking fibers, rather 
they tend to be chemically homogeneous, and as with the common particulate 
superabsorbents, form slippery gels and encounter processing problems when 
wet-laid. 
Oddly, to add to the above, there are reports in the literature of various 
chemicals apparently similar to those used herein apparently imparting 
wet-strength and/or hydrophobicity, i.e., water-resistance, to paper. 
In view of the foregoing considerations, improvements in absorbent 
cellulosic fibers which do not make the fiber incompatible with wet-laying 
are highly desirable. 
Accordingly, it is an object of the instant invention to provide a 
wet-layable papermaking fiber and pulp having an improved absorbent form. 
More specifically, it is an object herein to provide a chemically modified 
fiber (hereinafter "the fiber of the invention") having three chemically 
bonded components, namely a cellulose of natural origin (such as an 
ordinary pulp fiber), a poly(acrylate-co-itaconate) and a polyol; which 
fiber has a water-absorbent chemical form (such as the sodium salt form), 
which is useful especially in that it is readily capable of being 
distributed into a web by wet-laying (e.g., as a pulp) in admixture with 
untreated fibers. 
It is another object of the invention to provide absorbent wet-laid paper 
comprising the fiber of the invention. 
A further object of the invention is the provision of a suitable process, 
unreliant on metal catalysts as used in common grafting processes of the 
art, for reproducibly making the fiber of the invention. 
These and other objects are secured, as will be seen from the following 
disclosure. 
BACKGROUND ART 
For general discussion of coatings and chemical modifications of 
papermaking fibers and of paper see "Pulp and Paper, Chemistry and 
Chemical Technology", Ed. James P. Casey, Wiley-interscience, 1981, Vols. 
I-IV. See also "Chemical Modification of Papermaking Fibers", K. Ward, 
Marcel Dekker, N.Y., 1973. 
Japanese Laid-Open 50-5610, Jan. 21, 1975, discloses treating a preformed 
paper web with an aqueous solution containing polyvinylalcohol and various 
copolymers, especially maleic anhydride-methyl vinyl ether, followed by 
drying and thermally treating, to form high-wet-strength papers. 
Papermaking wet-strength resins based on half-amides derived from maleic 
anhydride copolymers with various monomers are disclosed in U.S. Pat. No. 
4,391,878, Drach, issued Jul. 5, 1983. 
Papermaking sizing agents and adhesives based on carboxylated vinyl 
polymers are disclosed in U.S. Pat. No. 3,759,861, Shimokawa, issued Sep. 
18, 1973. 
Gantrez AN Technical Data Sheet, GAF Corp., suggests a number of useful 
applications for Gantrez polymers in connection with papermaking. Notably, 
Gantrez is suggested for use "as a beater additive to improve sizing, 
strength and dimensional stability." Further, "as a paper coating 
component, it can improve moisture . . . resistance." 
U.S. Pat. No. 4,018,951, Gross, issued Apr. 19, 1977, discloses absorbent 
films prepared by heating methyl vinyl ether-maleate copolymers with 
crosslinking agents such as diglycidyl ethers or dihaloalkanes. The films 
can assertedly be used in absorbent articles. 
U.S. Pat. No. 4,128,692, Reid, issued Dec. 5, 1977, discloses precipitating 
absorbent polymers onto fibers from an aqueous slurry. 
U.S. Pat. No. 4,721,647, Nakanishi et al, issued Jan. 26, 1988, discloses 
an absorbent article comprising hydrophobic fibers and a water-absorbent 
polymer as spherical particles. 
U.S. Pat. No. 4,295,987, Parks, issued Oct. 20, 1981, discloses a two-ply 
paper towel containing powdered absorbent copolymers. A layer can be 
sandwiched between two paper plies. 
Brandt et al, U.S. Pat. No. 4,654,039, issued Mar. 31, 1987, reissued as RE 
32,649 on Apr. 19, 1988, disclose superabsorbent polymers which can be 
used in absorbent structures. 
Weisman, U.S. Pat. No. 4,610,678, issued Sep. 9, 1986, discloses air-laid 
absorbent structures comprising a mixture of hydrophilic fibers and 
discrete particles of a water-insoluble hydrogel. 
Saotome, EP-A 192,216, published Aug. 27, 1986, discloses a water-absorbent 
fibrous structure, characterized as comprising a fibrous cellulosic 
material impregnated with a water-absorbent acrylic polymer and a fibrous 
material, which is produced by a method in which an aqueous solution of a 
monomeric component comprising acrylic acid and a radical initiator is 
diffused in a fibrous cellulosic material and heated, followed by blending 
with a fibrous material. 
See also U.S. Pat. No. 4,354,901, Kopolow, issued Oct. 19, 1982 and U.S. 
Pat. No. 4,552,618, Kopolow, issued Nov. 12, 1985. The Kopolow disclosures 
relate to compression or heat treatment of boards in the dry state after a 
wet-laying papermaking process. The boards comprise "hydrocolloidal 
fibers" such as those of U.S. Pat. No. 3,889,678, Chatterjee et al, issued 
Jun. 17, 1975. 
Heat treatment of absorbent carboxyalkyl cellulose fibers in an absorbent 
structure to derive improved fluid absorptive properties is disclosed in 
U.S. Pat. No. 3,858,585, Chatterjee, issued Jan. 7, 1975. 
Grafted, hydrolyzed absorbents are disclosed in "The Chemistry and 
Technology of Cellulosic Copolymers", Hebeish, Springer-Verlag, 1981; see 
also U.S. Pat. No. 3,366,582, Adams et al, issued Jan. 30, 1968 and U.S. 
Pat. No. 4,151,130, Adams issued Apr. 24, 1979. 
U.S. Pat. No. 4,151,761, Schoggen et al, issued Feb. 24, 1981, discloses 
sheets prepared from certain modified fibrous carboxymethylcellulose 
derivatives, sometimes known as bibulous cellulosic fibers. Such sheets 
are disclosed in patents including U.S. Pat. No. 3,678,031, Schoggen, 
issued Jul. 18, 1972 and U.S. Pat. No. 3,589,364, Dean and Ferguson, 
issued Jun. 29, 1971. 
U.S. Pat. No. 4,780,500, Sinka et al, issued Oct. 25, 1988, discloses a 
coating composition for paper and paperboard containing pigment, binder, 
lubricant and water. The composition comprises a copolymer of 80%-98% 
(wt.) acrylic acid and 2%-20% (wt.) itaconic acid. The copolymer is water 
dispersible, has a molecular weight of 100,000-800,000 and is in acid, 
sodium, potassium and/or ammonium salt form. Included are compositions 
comprising by way of copolymer 95% (wt.) sodium acrylate and 5% (wt.) 
diammonium itaconate and having M.sub.W 250,000-400,000. Such copolymers 
can be used at a low level (0.05%-0.8% wt.) based on solids in the coating 
composition as a retention aid to retard release of water from the coating 
composition without increasing its viscosity. 
Patents relating to papermaking processes generally useful in the context 
of the present invention and incorporated herein by reference include U.S. 
Pat. No. 3,301,746, Sanford et al, issued Jan. 31, 1967; U.S. Pat. No. 
3,905,863, Ayers, issued Sep. 16, 1975; Morgan, Jr. et al, issued Nov. 30, 
1976; U.S. Pat. No. 4,191,609, Trokhan, issued Mar. 4, 1980; U.S. Pat. No. 
4,300,981, Carstens, issued Nov. 17, 1981; U.S. Pat. No. 4,440,597, Wells 
et al, issued Apr. 3, 1984; U.S. Pat. No. 4,469,735, Trokhan, issued Sep. 
4, 1984; and U.S. Pat. No. 4,637,859, Trokhan, issued Jan. 20, 1987. 
SUMMARY 
The present invention relates to a chemically modified fiber which has good 
absorbent properties. The fiber comprises, chemically bonded together, (a) 
a cellulosic fiber, very preferably a Kraft or chemithermomechanical 
fiber; (b) a poly(acrylate-co-itaconate) preferably having a relatively 
high acrylate content and a relatively low itaconate content; and (c) a 
polyol, very preferably a polyethylene glycol. 
In more detail, the invention encompasses a chemically modified fiber 
having a water absorbency and retention value in the range from about 15 
g/g to about 130 g/g comprising, chemically bonded together: (a) a 
cellulosic fiber selected from the group consisting of 
chemithermomechanical pulp fiber, bleached hardwood Draft pulp fiber, 
bleached softwood Kraft pulp fiber, unbleached hardwood Kraft pulp fiber, 
unbleached softwood Kraft pulp fiber, bleached softwood sulfite pulp 
fiber, unbleached softwood sulfite pulp fiber, cotton linters, mercerized 
dissolving pulp fiber, unmercerized dissolving pulp fiber, and mixtures 
thereof; (b) a poly(acrylate-co-itaconate) having a weight average 
molecular weight in the range from about 60,000 to about 1,000,000, an 
acrylate content of from about 50 mole % to about 99 mole % and an 
itaconate content of from about 1 mole % to about 50 mole %, and (c) a 
polyol; wherein the proportion by weight of said 
poly(acrylate-co-itaconate) to polyol is from about 250:1 to about 3:1 and 
the weight of said poly(acrylate-co-itaconate) plus said polyol per unit 
weight of said cellulosic fiber, (a), is in the range from about 0.3 to 
about 2, the poly(acrylate-co-itaconate) weight being expressed on an acid 
equivalent basis. 
In the above, a preferred polyol has formula HO(CH.sub.2 CH.sub.2 O).sub.n 
H wherein n is from about 4 to about 154 and a preferred proportion by 
weight of poly(acrylate-co-itaconate) to polyol is from about 30:1 to 
about 4:1. 
In a highly preferred embodiment, the invention provides a chemically 
modified fiber wherein said poly(acrylate-co-itaconate) has acrylate 
content of from about 90 mole % to about 95 mole % and itaconate content 
of from about 5 mole % to about 10 mole %; said weight average molecular 
weight is in the range from about 600,000 to about 900,000; n is said 
formula is from about 34 to about 100; and said weight of 
poly(acrylate-co-itaconate) plus polyol per unit weight of said cellulosic 
fiber, (a), is in the range from about 0.6 to about 1.5. 
In other absorbent, quick-wicking chemically modified fiber embodiments, n 
in said formula is from about 70 to about 80; said proportion by weight of 
poly(acrylate-co-itaconate) to polyol is from about 10:1 to about 5:1; and 
said weight of poly(acrylate-co-itaconate) plus polyol per unit weight of 
cellulosic fiber, (a), is in the range from about 0.8 to about 1.2. Such 
fiber of the invention is especially useful when said water absorbency and 
retention value is in the range from about 50 g/g to about 90 g/g. 
In the above-identified fiber of the invention, cations, which are 
inherently present in a charge-balancing amount, are generally selected 
from the group consisting of sodium, potassium, lithium, hydrogen and 
mixtures thereof, more preferably sodium, hydrogen and mixtures thereof. 
A highly preferred form of the fiber for absorbency purposes is the sodium 
salt form, however the acid form is also useful, inter-alia because it can 
readily be taken to the absorbent form by sodium hydroxide. 
The invention encompasses papermaking pulps especially useful for 
wet-laying (although the same pulps are also useful in air-laying 
applications). Cellulosic papermaking pulps in accordance with the 
invention consist essentially of the above-identified fiber, or can be a 
mixture of the fiber of the invention with an unmodified fiber, such as 
the unmodified component (a) fiber identified supra. One such pulp 
consists essentially of: from about 5% to about 60% of the chemically 
modified fiber of the invention and from about 40% to about 95% of 
conventional cellulosic fiber. 
Preferred chemically modified pulps in accordance with the invention are 
useful in the acid form, for example the pulp is largely acid-form when 
the content of cations which are hydrogen is such as to produce a pH of 
less than 5 when the pulp is dispersed in water. In this instance, the 
consistency can vary widely and the pulp can be shipped at high 
consistency since, as noted above, the chemically modified fiber is not 
absorbent. 
The invention also encompasses the absorbent form of the cellulosic 
papermaking pulp, for example one comprising a major proportion of 
sodium-form fiber of the invention: typically, in such a pulp, the content 
of cations which are hydrogen is such as to produce a pH of about 6 to 
about 9 when dispersed in water. 
The fiber of the invention is a lightly crosslinked material. Particular 
attention is paid herein to adjusting the relative proportions of the 
starting-material components and to process conditions so that a lightly 
crosslinked fiber can best be achieved. 
Thus a preferred fiber of the invention can be secured by heating for 
specific curing times at particular curing temperatures a conventional 
cellulosic fiber onto which has been deposited an intimate mixture of the 
poly(acrylate-co-itaconate) and polyol. For proper control of the 
crosslinking, it is critical that the copolymer starting-material be 
capable of forming anhydride functionality during the thermal cure. In the 
case of the poly(arcylate-co-itaconate), the 1,4-diacid functional 
(present in the copolymer by virtue of itaconate) will dehydrate during 
heating, to afford the requisite anhydride. Best results can be achieved 
by operating in specific, acidic pH ranges, and by control of the cation 
composition, especially by avoiding strongly co-ordinating polyvalent 
metal ions. 
The term "fiber" is used to distinguish the immediate product of the 
invention from strong interbonded masses of paper fibers. The latter might 
seem similar based on a mere recital of ingredients, but do not have the 
dispersability and absorbency properties of the invention. 
Thus, as noted, the fiber of the invention can be used on large scale as a 
papermaking pulp, especially in admixture with conventional papermaking 
fiber. Paper webs made by wet-laying such pulps are especially useful for 
making disposable absorbent paper towels having a unique distribution of 
absorbent material, which are capable of quickly absorbing appreciable 
amounts of water or watery fluids. 
Useful embodiments of the invention include a wet-laid paper web, 
comprising at least 1% (preferably 5% to 10%) up to about 60% of 
chemically modified fiber of the invention. Excellent webs are secured 
when the content of fiber of the invention is from about 20% to about 50%. 
The invention also encompasses a disposable absorbent article, such as a 
disposable absorbent towel or a pad for a catamenial, comprising one or 
more plies of a wet-laid paper web as described herein. 
The invention has several significant advantages. Thus the fiber of the 
invention leads to wet-laid absorbent paper free from aesthetic negatives 
in use, such as a tendency to shed particles of absorbent material or such 
as a tendency to feel slippery and gel-like when wetted. Other advantages 
include, but are not limited to: simplicity; nonreliance on expensive or 
toxic metal catalysts during the preparation; the ability to improve the 
absorbency of "difficult" fibers such as chemithermomechanical pulp fibers 
(which is very desirable in view of the environmental advantages of such 
fibers as compared with chemical pulp fibers); and importantly, the 
ability to provide improved absorbent fibers which better accommodate the 
stresses of wet-laying papermaking with less tendency to disintegrate or 
cause wire-blocking or drying difficulties than conventional absorbent 
polymer-treated fibers. 
All percentages herein are by weight and temperatures are ambient 
(25.degree. C.), unless otherwise specifically noted.

DETAILED DESCRIPTION OF THE INVENTION 
Chemical Structure Features--Description of the Drawing 
A fiber in accordance with the instant invention is effectively a 
cellulosic fiber of natural origin to which is chemically attached a 
lightly crosslinked mixture of particular synthetic components, namely a 
poly(acrylate-co-itaconate) and a polyol. Without being limited by theory, 
the essential features of the chemical bonding occurring in a preferred 
embodiment of the invention are illustrated in FIG. 1. 
FIG. 1 shows, covalently bonded together, (i) a cellulose moiety, (ii) 
itaconate moieties (these form junctions between the other moieties), 
(iii) polyacrylate moieties and (iv) a polyol moiety, which in FIG. 1 is 
one derived from a polyethylene glycol. Not shown are the fiber as a 
whole, of which the depicted cellulose moiety is but a part, as well as 
cations (sodium being preferred), which are inherently present in a 
charge-balancing amount and are primarily associated with the negative 
charges of the copolymer; water molecules; and any imperfections, such as 
incompletely reacted moieties. 
Important features of the invention illustrated in FIG. 1 include that the 
relative proportion of itaconate to acrylate is low, ensuring a relatively 
light crosslinking. Moreover, the lightly crosslinked 
acrylate/itaconate/polyol structure is chemically attached to the 
cellulosic fiber. 
The fibers of the invention are quite different from grafted cellulosic 
fibers of well-known kinds which can be made, for example by 
cerium-catalyzed polymerization of methyl acrylate in presence of a 
cellulosic fiber followed by sodium hydroxide hydrolysis. A known 
technique for finding the location of a highly charged synthetic 
polycarboxylate polymer in relation to a material such as cellulose which 
is less highly charged involves mapping the distribution of 
charge-balancing cations, such as sodium, by X-ray Energy Dispersive 
Spectroscopy. Sodium ion maps of preferred fibers of the invention show 
substantially intact cellulose regions without high concentrations of 
sodium being present between the fiber wall and the fiber lumen, whereas 
there is a significant proportion of sodium distributed between the fiber 
wall and the lumen in typical hydrolyzed methyl-acrylate grafted fibers. 
Without being bound by theory, it is believed that having a fiber with 
substantially intact cellulosic regions of natural origin and a chemically 
attached, lightly crosslinked, water-swellable poly(acrylate-co-itaconate 
are important for securing the benefits of the instant invention. 
Composition of fiber of the invention 
In general, the fiber of the invention comprises, chemically bonded 
together: (a) a cellulosic fiber; (b) a poly(acrylate-co-itaconate and (c) 
a polyol. 
(a). Cellulosic Fiber. 
The cellulosic fiber, to which the remaining components are bonded in the 
fiber of the invention, is a conventional material. In general, it is 
selected from the group consisting of chemithermomechanical pulp fiber, 
bleached hardwood Kraft pulp fiber, bleached softwood Kraft pulp fiber, 
unbleached hardwood Kraft pulp fiber, unbleached softwood Kraft pulp 
fiber, bleached softwood sulfite pulp fiber, unbleached softwood sulfite 
pulp fiber, cotton linters, mercerized dissolving pulp fiber, unmercerized 
dissolving pulp fiber, and mixtures thereof. 
Preferred cellulosic fiber is selected from the group consisting of 
chemithermomechanical pulp fiber, bleached hardwood Kraft pulp fiber, 
bleached softwood Kraft pulp fiber, unbleached hardwood Kraft pulp fiber, 
unbleached softwood Kraft pulp fiber, and mixtures thereof. 
Highly preferred embodiments of the invention include those made from 
chemithermomechanical pulp fiber and bleached Kraft fiber such as southern 
softwood Kraft fiber. As will be seen hereinafter, there are somewhat 
different preferred synthesis conditions, especially relating to pH, 
curing temperature and curing time, depending on which of these highly 
preferred fibers is chosen. 
Preferably, such fiber will be of a quality deemed good or superior for the 
purposes of conventionally making wet-laid paper webs. More specifically, 
fiber having relatively low levels of "fines " and a good staple length 
are preferred. 
(b). Poly(acrylate-co-itaconate). 
The fiber of the invention also contains a poly(acrylate-co-itaconate). In 
general, this copolymer has an acrylate content of from about 50 mole % to 
about 99 mole %, more preferably about 70 mole % to about 98 mole %, most 
preferably about 90 mole % to about 95 mole % and an itaconate content of 
about 1 mole % to about 50 mole %, more preferably about 2 mole % to about 
30 mole %, most preferably about 5 mole % to about 10 mole %. 
The poly(acrylate-co-itaconate) useful herein are selected members of a 
known class of copolymers. They may be prepared by conventional, art-known 
techniques for copolymerizing acrylic acid and itaconic acid. Typically, 
mild aqueous conditions using a conventional water-soluble free-radical 
initiator are used. Suitable initiators are illustrated by the common azo 
initiators such as 2,2'-azobis(2-amidinopropane) dihydrochloride; as well 
as potassium persulfate, hydrogen peroxide or the like. Selection of a 
copolymer useful herein is based on a recognition that any given itaconate 
moiety in the copolymer will be unreactive for the purposes of forming the 
fiber of the invention if at the time thermal crosslinking is attempted, 
an itaconic anhydride moiety cannot be formed. Such resistance to forming 
the anhydride is exhibited especially when the itaconate component of the 
copolymer is completely neutralized, such as in the form of the diammonium 
salt, and to an even greater extent, when the itaconate component of the 
copolymer is co-ordinated with multivalent metal ions such as those of 
calcium, magnesium or iron. For practical purposes, it is therefore highly 
preferred both to use the acid form of the copolymer and to limit the 
content of multivalent metal cations in the copolymer. The latter can best 
be achieved by synthesizing the copolymer in clean water. 
Although isolable, the copolymer can conveniently be made, and further 
directly used to form the fiber herein, as an aqueous solution. 
Copolymers most useful herein have weight average molecular weight, 
M.sub.W, as determined by low angle laser light scattering, in the general 
range from about 60,000 to about 1,000,000. Preferred copolymer has weight 
average molecular weight of from about 400,000 to about 1,000,000. Within 
practical limits, the absorbent properties of the fiber of the invention 
increase significantly as the weight average molecular weight of the 
copolymer increases. Since copolymers tend to become viscous and difficult 
to handle at very high weight average molecular weight, a highly preferred 
copolymer weight average molecular weight is in the range from about 
600,000 to about 900,000. 
As found in the fiber of the invention, the copolymer is chemically bonded 
to the cellulosic fiber and to the polyol. 
(c). Polyol 
The polyol component of the fiber of the invention is an alcohol having two 
or more --OH groups. In the fiber of the invention, as illustrated in FIG. 
1, the polyol is at least partially chemically incorporated by reaction 
with itaconic anhydride moieties of the copolymer (see the chemistry of 
the synthesis further discussed hereinafter) so that it is no longer in 
the free state and acts as a crosslinking group in the fiber of the 
invention. Although a wide variety of polyols are useful herein, preferred 
polyols are water-soluble. Although any polyol consisting essentially of 
C, H and O can be used, the polyol is typically selected form the group 
consisting of polyethylene glycol, polyvinyl alcohol, ethylene glycol, 
propylene glycol, glycerin, pentaerythritol and the like. 
Another polyol capable of being substituted for propylene glycol within the 
spirit and scope of the invention is a relatively longer chain alpha-omega 
alkylene diol, such as a 1,6 hexylene glycol. 
In preferred embodiments, the polyol is a diol, such as polyethylene 
glycol, and can have varying molecular weight. Suitable diol materials 
have the formula HO(CH.sub.2 CH.sub.2 O).sub.n H wherein n is from about 4 
to about 154, more preferably from about 34 to about 100, most preferably 
from about 70 to about 80. Preferred embodiments of these materials are to 
be found in the commercial PEG 200-7000 series. Thus, commercial PEG 200 
corresponds with n in the above formula of about 4, PEG 1000 corresponds 
with n of about 22, PEG 1500 corresponds with n of about 34, PEG 3350 
corresponds with n of about 76 and PEG 6800 corresponds with n of about 
154. In practice, it is found that although quick-wicking fiber of the 
invention can be prepared with PEG 200, absorbency results are optimal 
with PEG 3350. PEG 6800, though usable, gives somewhat less preferred 
embodiments of the invention. 
Proportions of components 
In general, the proportion by weight of poly(acrylate-co-itaconate) to 
polyol in the fiber of the invention is in the range from about 250:1 to 
about 3:1, more preferably from about 30:1 to about 4:1, most preferably 
from about 10:1 to about 5:1. When the polyol has a low molecular weight, 
such as ethylene glycol, the weight amount of polyol is relatively low. As 
the molecular weight increases in a homologous series, such as in PEG of 
progressively increasing molecular weight, the relative weight of polyol 
increases. When the polyol has many --OH groups, as in polyvinylalcohols, 
the relative proportion by weight of polyol may be low, even though the 
molecular weight of the polyol is high. 
Without being limited by theory, it is believed that the proportion of 
copolymer to polyol is very important for controlling the crosslink 
density in the fiber of the invention. The above-recited ranges take into 
account that maintaining a relatively constant, consistently low crosslink 
density is preferred. 
In the fiber of the invention, the add-on, that is to say the weight of 
poly(acrylate-co-itaconate) plus polyol ((b) plus (c)) per unit weight 
cellulosic fiber (a) is in the general range from about 0.3 grams per gram 
to about 2 grams per gram, more preferably from about 0.6 grams per gram 
to about 1.5 grams per gram, most preferably from about 0.8 to about 1.2 
grams per gram. It should be appreciated that as the add-on is 
progressively decreased, the absorbency of the fiber decreases but the 
fiber may become somewhat easier to process. On the other hand, excessive 
add-on, outside the scope of this invention, can lead to an appreciable 
content of pieces of absorbent polymer which are not chemically attached 
to the fiber. Moreover, there appears to be a plateau effect of absorbency 
performance and usefulness when much more than the stated upper limit of 
add-on is used. 
It should be appreciated that add-on levels herein are, in percentage 
terms, rather high, i.e., 30% to 200%. These levels are very much higher 
than in conventional paper coatings, wet-strength additive applications or 
the like. 
The poly(acrylate-co-itaconate) weight referred to hereinabove and 
throughout the specification is by convention expressed on an acid 
equivalent basis. That is to say, regardless of the form of the 
poly(acrylate-co-itaconate) used in the synthesis of the fiber of the 
invention, and equally regardless of the form product fiber, the 
convention is adopted of everywhere specifying the 
poly(acrylate-co-itaconate) weight as though it were in the acid form, 
i.e., all the charge-balancing cations are H. In this manner, the relative 
proportion of poly(acrylate-co-itaconate) to the cellulose and polyol 
components is unambiguously determined. 
Cations 
Since the fiber of the invention contains negatively charged carboxylate 
groups, especially those associated with the poly(acrylate-co-itaconate) 
cations will inherently be present in a charge-balancing amount. 
In the fiber of the invention, the cations are generally selected from 
sodium, potassium, lithium, hydrogen and mixtures thereof, more preferably 
sodium, potassium, hydrogen and mixtures thereof, most preferably sodium, 
hydrogen and mixtures thereof. 
A similar range of cation composition applies to the copolymer 
starting-material, however the most highly preferred cation for the 
starting-material copolymer is hydrogen. Thus the starting form of the 
copolymer is most preferably the acid form. 
The fiber of the invention can be in the acid form, in which it is not 
directly useful as in absorbent material but is very useful for long-term 
storage or shipping from the fiber manufacturing plant to the papermaking 
plant at high consistency; or it can be int he highly absorbent sodium 
form. Other such water-soluble monovalent cation salts of the fiber of the 
invention, such as the potassium salt, as noted, are likewise useful 
absorbents. 
Importantly, polyvalent cations such as those of iron, calcium, magnesium 
and aluminum are avoided, both in the starting copolymer and in the fiber 
of the invention, as much as practical considerations will allow. Such 
cations can not only interfere with the synthesis of the fiber but also 
with the absorbent properties of the product fiber. 
Absorbency property 
The fiber of the invention is most useful as an absorbent material. Thus, 
it has a water absorbency and retention value (WAARV)--this quantity being 
measured according to the procedure given in "Test Methods" 
hereinafter--in the range from about 15 g/g to about 130 g/g, more 
preferably from about 30 g/g to about 100 g/g, most preferably from about 
50 g/g to about 90 g/g. 
The term "retention" in WAARV takes into consideration that the test method 
involves centrifugation, so that water quite tenaciously retained by 
fiber, pulp or paper is included in the absorbency measurement. Moreover, 
WAARV values are measured at a constant alkaline pH so that values are 
reproducible and can be compared. WAARV can be used to characterize both 
acid-form and salt-form fibers according to the invention because during 
the test, in-situ conversion of acid-form to salt-form fiber takes place. 
Moreover, WAARV can be used to measure the absorbency of wet-laid webs 
comprising the fiber of the invention. 
Without being bound by theory, it is believed to be important that the 
fiber herein is substantially discrete rather than a mass of strongly 
interbonded fibers with significant amounts of polymer located at the 
fiber crossovers. That latter behavior, believed inferior for absorbency 
purposes, is the kind to be expected when the fiber results from (i) 
forming paper, e.g., on a Fourdrinier wire then (ii) applying a polymer, 
for example by spray-on or impregnation, then (iii) crosslinking the 
polymer: such a sequence is not in accordance with this invention. 
Thus the fiber of the instant invention results from (i) concentrating the 
polymer components as much as possible on individual cellulosic fibers 
prior to making paper, then (ii) thermally crosslinking to form the 
chemical bonds between the polyol-copolymer mixture and the fiber. The 
resulting fiber can then (iii) be used in bulk as a papermaking pulp or 
furnish for wet-laying to achieve an absorbent, quick-wicking paper web 
free from aesthetic disadvantages. 
Chemistry of Synthesis 
It should be understood that water (H.sub.2 O) is eliminated in the 
chemical reactions of curing or thermally crosslinking which are normally 
used to form the fiber of the invention. Without being limited by theory, 
the following chemical reactions are believed to occur: 
(I) all or at least part of the itaconate moieties of the copolymer 
dehydrate in the presence of heat to give itaconic anhydride moieties; 
(II) a portion of the itaconic anhydride moieties further react by 
acylating the --OH groups of the cellulosic fiber, (a): this results in at 
least partial chemical attachment of copolymer to fiber via covalent ester 
bonds of cellulose to itaconate; and 
(III) a portion of the itaconic anhydride moieties further react by 
acylating the --OH groups of the polyol: since the polyol is at least 
difunctional, this results in crosslinking of the copolymer and polyol. 
Although it is believed that substantially all itaconate moieties are 
accounted for by participating in reaction (II) or (III), it is normal 
practice herein to provide a slight excess of itaconate moieties beyond 
that required for complete reaction. Thus the fiber of the invention may 
contain traces of non-crosslinked itaconate and, although unlikely, it is 
believed that traces of anhydride-form itaconate may be present in dry 
fiber of the invention. 
To be noted is that the terms "curing", "thermally crosslinking", 
"crosslinking" and "chemically reacting" are equivalent herein, at least 
inasmuch as they refer more or less specifically to producing the fiber of 
the invention. Curing temperatures and times are very important and are 
discussed at length hereinafter. 
Preparation of fiber of the invention 
In general, fiber of the invention can be made by lightly crosslinking, 
typically by a thermal method, a cellulosic fiber of a quality suitable 
for wet-laying papermaking, typically a conventional wet-laying 
papermaking fiber such as bleached southern softwood Kraft or 
chemithermomechanical fiber, with an intimate mixture of 
poly(acrylate-co-itaconate) and polyol. 
It is essential that immediately prior to thermal crosslinking, the 
poly(acrylate-co-itaconate) should be capable of producing an acidic 
solution in water, for the simple reason that the fully neutralized salts, 
such as the diammonium salt, the disodium salt etc., are incapable of 
thermally eliminating water and of forming an anhydride, which as 
discussed supra, is an essential part of the chemical reaction leading to 
the fiber of the invention. 
It is consistent with the sense of the invention to deposit 
copolymer-polyol mixtures on cellulosic fibers using a process such as 
extrusion, evaporative deposition or any similar deposition method, 
regardless of whether it involves a fluid medium or carrier or not. 
When there is no medium to be removed, the mixed fiber/copolymer/polyol can 
be directly crosslinked by heating at suitable curing temperatures for 
limited curing times, always provided that a suitably intimate mixture has 
been formed. 
When it is desired to make fibers without resorting to expensive process 
equipment, a medium can be used to deposit the poly(acrylate-co-itaconate) 
on the starting-material cellulosic fiber. In this event, the medium 
should preferably be capable of substantially completely dissolving the 
poly(acrylate-co-itaconate) and the polyol, so that an intimate mixture of 
the two can be evaporatively deposited on the cellulosic fiber. The medium 
should be capable of substantially complete evaporation at normal or 
reduced pressures below the temperatures at which thermal crosslinking 
occurs. Acetone/water mixtures, acetone/water/methanol, mixtures, and 
methanol/water mixtures are all quite suitable, as are water mixtures with 
other common low-boiling water-miscible organic solvents, but water alone 
is highly preferred, especially on account of low cost and low toxicity. 
When water dissolves the poly(acrylate-co-itaconate) and polyol, the result 
is an "aqueous medium" for the purposes of this invention. Typically, the 
aqueous medium has a percentage by weight of poly(acrylate-co-itaconate) 
plus polyol which is about 10% by weight or higher, more preferably the 
concentration is about 20%. Much more importantly, the aqueous medium is 
found to behave quite differently, in terms of its suitability, depending 
on the pH. In general, the pH of the aqueous medium must lie in the range 
from about 1.8 to about 4.0, more preferably from about 2.5 to about 3.5. 
When the cellulosic fiber to be treated is chemithermomechanical fiber, a 
pH range of from about 1.8 to about 4.0 is acceptable. When other 
cellulosic fiber types are being treated, it is essential that the pH of 
the aqueous medium should be in the range from about 2.5 to about 4.0. 
Below the above-specified pH minima, depending on the precise type of 
cellulosic fiber, the cellulosic fiber will tend to degrade. Moreover, at 
pH values much above pH the stated upper limit, the degree of crosslinking 
in the crosslinking step is sharply reduced, to an unacceptable extent. 
Water used to make the aqueous medium is preferably substantially free from 
polyvalent cations such as those of calcium, magnesium, iron and aluminum. 
In any event, the content of such cations should not be so high as to 
inhibit the thermal crosslinking reaction. 
Once the poly(acrylate-co-itaconate) and polyol are dissolved and an 
aqueous medium is formed, the medium can be applied to cellulosic fibers 
in whatever manner desired, provided that these fibers are discrete or 
dispersed rather than knit together in the form of a bonded web. 
The mixture of cellulosic fibers and aqueous medium is evaporated at 
non-crosslinking temperatures. For practical purposes, such temperatures 
are generally below about 75.degree. C., typically in the range 50.degree. 
C. to 70.degree. C. At higher temperatures, there is an increased risk of 
uncontrolled crosslinking. Lower temperatures can be used: for example 
water can be evaporated by freeze-drying. 
Evaporation of water results in a substantially dry, intimate mixture of 
the poly(acrylate-co-itaconate) and polyol on the cellulosic fibers. 
Preferably, the evaporation is carried out under conditions which avoid 
sticking together of the fibers. One suitable approach believed to be good 
for removing water from the aqueous medium and uniformly deposition the 
poly(acrylate-co-itaconate) and polyol as an intimate mixture on the 
cellulosic fiber surface involves the use of a supercritical fluid such as 
supercritical carbon dioxide for extracting the water. 
A preferred approach to the depositing operation which has been found quite 
satisfactory, especially on grounds of economy and simplicity, is to 
evaporate a thin layer of the 
poly(acrylate-co-itaconate)/polyol/fiber/water mixture. Although there may 
be some sticking together of fibers, the evaporated layer is readily 
repulped (after the crosslinking step described in detail below) to give 
substantially discrete fibers of the invention. 
In general, crosslinking or "curing" herein involves applying a controlled 
amount of heat, which can be achieved under a range of temperatures and 
times. 
Thus, in a preferred embodiment, the invention encompasses a process for 
preparing a chemically modified fiber having a water absorbency and 
retention value in the above-recited ranges, comprising a step of: 
thermally crosslinking, at a curing temperature of from about 100.degree. 
C. to about 150.degree. C., more preferably from about 110.degree. C. to 
about 140.degree. C. for a curing time of from about 60 minutes to about 2 
minutes, more preferably from about 33 minutes to about 3 minutes, a 
starting-material pulp consisting essentially of the above-identified 
cellulosic fiber (component (a)); with an intimate mixture of 
poly(acrylate-co-itaconate) (above-identified as (b), and a polyol 
(component (c) identified hereinabove); wherein the proportion by weight 
of poly(acrylate-co-itaconate) copolymer to polyol is in the above-recited 
general ranges and the weight of poly(acrylate-co-itaconate) plus polyol 
per unit weight of cellulosic fiber, (a), is likewise as recited 
hereinabove. 
In practice, the copolymer-polyol treated dry cellulosic fibers are 
preferably exposed to heat as a thin layer. Preferably, a pre-heated oven 
is used for best control of the crosslinking or curing reaction. In order 
to minimize curing time at any given curing temperature, the practitioner 
will preferably use a flow of hot air and will permit access of the hot 
air to both sides of the fiber layer by first removing any substrate which 
may have been used in the above-described fiber-polymer contacting 
procedures: in practice, this is most easily accomplished when the 
substrate is "non-stick", for example, polytetrafluoroethylene (PTFE). 
Based on this appreciation of the curing operation, the practitioner will 
readily appreciate that it is possible to conduct evaporative deposition 
and thermal crosslinking, indeed the entire synthesis of the fiber of the 
invention, in a continuous or semi-continuous mode. For example, a PTFE 
carrier belt can carry the cellulosic fiber, copolymer and polyol through 
the evaporative deposition stage and into the curing stage in the 
synthesis process. 
It is however been found that it is preferred to cure in the absence of a 
substrate, or in the presence of a substrate which does not overly affect 
heat flow into the above-described thin layer during curing. 
Thus, when curing a fiber/copolymer/polyol layer about 1 mm thick on glass 
about 3 mm thick, the layer being one resulting from evaporation of an 
aqueous medium having a pH of 3.00, the following curing temperatures and 
the corresponding curing times are illustrative of preferred curing 
conditions: 
______________________________________ 
Curing Temperature (.degree.C.) 
Curing Time (minutes) 
______________________________________ 
110 33 
120 18 
130 11.5 
140 8 
______________________________________ 
In the above and throughout the specification, curing times are defined as 
the total period of exposure to hot air at the curing temperature, the 
fiber layer being introduced to the hot air oven at ambient temperature. 
Substituting PTFE for glass as a substrate for evaporating the aqueous 
medium in the above, and removing the PTFE from a layer now about 2 mm 
thick prior to curing, a preferred curing time at a temperature of 
130.degree. C. is reduced from 11.5 minutes (glass-see the above) to about 
6.5 minutes (no substrate). The reduction in the curing time is believed 
to be due to the improved access of hot air to both sides of the fibrous 
layer. 
In light of the above, the practitioner should be aware that for best 
results, especially when manufacturing on a large scale, it is advisable 
to optimize the curing temperature and time at the scale chosen, by the 
simple expedient of measuring Fiber Yield and water absorbency and 
retention values of the fiber of the invention, each as defined in "Test 
Methods" hereinafter, over a series of curing temperatures and times in 
accordance with the invention. 
Once curing is complete, the raw fiber of the invention is repulped, 
preferably with an amount of shear which will not significantly reduce the 
staple. Repulping is generally carried out in water under acid conditions, 
typically at a pH of about 2 to about 4, more preferably at pH of about 2 
to about 3 (hence the term "acid repulping" can be used to characterize 
this step). In the acid repulping step, the fiber of the invention is 
substantially in the acid form. In this form, the fiber is non-swollen and 
is readily manipulated, thus in this form it has the advantage that it can 
conveniently be shipped as a concentrated slurry from the fiber 
manufacturing plant to the papermaking plant if desired. 
After repulping, the fiber of the invention can be secured substantially in 
the dry, sodium-salt form by a fiber-swelling step. The fiber-swelling 
step simply involves neutralizing with sodium hydroxide, preferably to a 
pH of from about 7.5 to about 9, whereon the fiber swells greatly. The 
fiber swelling step can be quite slow, and may take up to 2-3 days. It is 
a curious feature of the fiber of the invention that the first conversion 
from the acid form to the sodium salt form is of such duration, since 
subsequent interconversions between the acid and salt forms can be carried 
out quite rapidly by adding acid or base, as needed. 
If desired, after the fiber-swelling step, the fiber of the invention can 
be filtered and dried, typically at temperatures of about 80.degree. 
C.-90.degree. C., although this is not necessary and is not usually 
practiced if the fibers are to be used as a pulp for wet-laying 
papermaking. 
To be noted is that fibers of the invention in the sodium salt form are 
superior in their heat resistance as compared with the corresponding 
fibers in the acid form. If in the above, the sodium hydroxide is 
substituted by potassium hydroxide or lithium hydroxide, the corresponding 
potassium and lithium salt forms of the fiber of the invention can be 
secured. 
For the practical reason that the fiber of the invention is typically used 
in a wet-laying process, the practitioner generally does need to dry the 
salt form of the fiber prior to use in wet-laying, but can directly use it 
as a slurry. 
Webs and Wet-Laying Processes for their Production 
In other embodiments, the invention provides a wet-laid paper web 
comprising from about 5% to about 60%, more preferably from about 10% to 
about 60%, most preferably from about 20% to about 50% of the fiber of the 
invention (or equivalently, the product of the above-identified synthesis 
process). The balance of the composition can be conventional papermaking 
fibers, such as fibers having an identical composition to the 
starting-material fibers. When mixtures of fiber of the invention and 
conventional papermaking fibers are co-distributed in a wet-laid web, 
highly absorbent, quick-wicking structures result. 
Preferred papermaking processes useful herein, as incorporated by reference 
in the background art discussion hereinabove, include continuous 
wet-laying processes designed for making conventional highly absorbent 
paper. 
A feature of interest which distinguishes several such processes and is 
believed to be useful in the context of the present invention is to avoid 
compressing or squeezing (e.g., calendering) the wet-laid web as much as 
possible during drying: also, it can be helpful to dry the webs containing 
the fiber of the invention using blow-through air dryers of conventional 
construction. This produces a rather open, absorbent web. 
A modification of a conventional wet-laying process which is especially 
helpful for making wet-laid webs according to the present invention in a 
continuous operation simply involves wet-laying at acidic pH, typically in 
the range from about 3 to about 5, followed by partially drying the 
wet-laid web, neutralizing on-line with a sprayed-on sodium carbonate or 
potassium carbonate solution (sodium hydroxide may be used but can yellow 
the web is not carefully applied), and drying, especially with the aid of 
a conventional Yankee dryer. 
Disposable absorbent towels 
The wet-laid webs can be used as plies in a two-ply or multi-ply disposable 
absorbent structure such as a disposable absorbent towel. All that needs 
to be done to secure such disposable absorbent structures is to combine 
plies comprising at least one wet-laid paper web according to the 
invention, in a conventional converting operation, e.g., simple glueing or 
bonding of the plies together. 
ALTERNATE EMBODIMENTS OF THE INVENTION 
The fiber of the invention is not limited to use as an absorbent for 
disposable absorbent towels, but may be used for making catamenial pads, 
absorbent dressings, pantiliners and the like. 
Fibers in accordance with the invention are further illustrated by the 
following Examples. 
EXPERIMENTAL 
Starting-materials 
Acrylic acid (Polysciences Inc., Warrington, Pa.) is vacuum distilled 
through a Vigreux column and is preferably used fresh in subsequent 
operations, e.g., within one day of distillation. Itaconic acid (Aldrich 
Chemical Co., Milwaukee, Wis.) is obtained in 99%+purity and is used as 
received. The free-radical initiator 2,2'-azobis(2-amidinopropane) 
dihydrochloride (WAKO V-50, Wako Pure Chemical Industries, Osaka, Japan) 
is also used as received. Unless otherwise noted, water is triply 
distilled. Where polymers are dialyzed, the dialysis membrane is obtained 
from Spectrum Medical Industries, Inc., Los Angeles, Calif. 
Polyethylene glycols (these preferred polyols are commonly known as "PEG", 
various suppliers being suitable) as used in the Examples have nominal 
molecular weights of 200, 1000, 1500, 3350, and 6800. PEG 200 is obtained 
from Polysciences Inc., Warrington, Pa. PEG 1000, PEG 1500 and PEG 6800 
are obtained from Scientific Polymer Products, Inc., Ontario, N.Y. PEG 
3350 is obtained from Sigma Chemical Co., St. Louis, Mo. 
Southern softwood Kraft pulp and northern softwood Kraft pulp are obtained 
from P & G Cellulose, Memphis, Tenn. Chemithermomechanical pulp is 
obtained from Quesnel Paper Co., Quesnel, B.C., Canada. 
EXAMPLE I 
Preparation of an poly(acrylate-co-itaconate) suitable for use in making 
fiber of the invention (90 mole % acrylate, 10 mole % itaconate) 
Acrylic acid (20.000 g, 0.27755 mole), itaconic acid (4.0121 g, 0.038386 
mole), Wako V-50 (0.0837 g, 0.308 millimole), and 150 ml of water which 
has been acidified to pH 2.0 with hydrochloric acid are added to a 250 ml 
three-necked round-bottomed flask. The necks are fitted with a 
thermometer, a stopper, and a gas inlet/outlet adapter capable of bubbling 
gas through a liquid in the flask and venting it. The solution is 
deaerated by passage of nitrogen gas and is then placed under an 
atmosphere of argon. The solution is heated to 55.degree. C. and is 
maintained at this temperature for 15 hours. The viscous solution of 
copolymer is cooled to ambient temperature and is dialyzed overnight 
against water (Spectrapor 3 tubing with molecular weight cut-off at 3500) 
to remove any unreacted monomers. The dialyzed solution is freeze dried to 
afford 23.00 g of poly(acrylate-co-itaconate), acid form, as a colorless 
solid. The weight average molecular weight, M.sub.W, as determined by low 
angle laser light scattering in 0.2 Molar sodium chloride in water 
(refractive index=1.3344, d.sub.n /d.sub.c =0.1683) is 896,100. 
EXAMPLE II 
Preparation of another poly(acrylate-co-itaconate) suitable for making 
fiber of the invention (90 mole % acrylate, 10 mole % itaconate) 
Acrylic acid (25.000 g, 0.34693 mole), itaconic acid (5.0151 g, 0.038548 
mole), Wako V-50 (0.1046 g, 0.3856 millimole), and 193 ml of water which 
has been acidified to pH 2.0 with hydrochloric acid are added to a 500 ml 
three-necked round-bottomed flask. The necks are fitted with a 
thermometer, a stopper, and a gas inlet/outlet adapter capable of bubbling 
gas through a liquid in the flask and venting it. The solution is 
deaerated by passage of nitrogen gas and is then placed under an 
atmosphere of argon. The solution is heated to 60.degree. C. and is 
maintained at this temperature for 15 hours. The viscous solution of 
copolymer is cooled to ambient temperature and is dialyzed against 
distilled water overnight (Spectrapor 3 tubing as in the foregoing 
Example) to remove any unreacted monomers. The dialyzed solution is freeze 
dried to afford 28.31 g of poly(acrylate-co-itaconate), acid form, as a 
colorless solid. The weight average molecular weight, M.sub.W, as 
determined by low angle laser light scattering in 0.2 Molar sodium 
chloride in water (refractive index=1.3344, d.sub.n /d.sub.c =0.1683) is 
658,200. 
EXAMPLE III 
Preparation of another poly(acrylate-co-itaconate) suitable for making 
fiber of the invention (90 mole % acrylate, 10 mole % itaconate) 
Acrylic acid (105.27 g, 1.4609 moles), itaconic acid (21.12 g, 0.1623 
mole), Wako V-50 (0.4403 g, 1.623 millimole), and 812 ml of water which 
has been acidified to pH 2.0 with hydrochloric acid are added to a 2 liter 
three-necked round-bottomed flask. The necks are fitted with a 
thermometer, a stopper, and a gas inlet/outlet adapter capable of bubbling 
gas through a liquid in the flask and venting it. The solution is 
deaerated by passage of nitrogen gas and is then placed under an 
atmosphere of argon. The solution is heated to 55.degree. C. and 
maintained at this temperature for 15 hours. The viscous solution of 
copolymer is cooled to ambient temperature, and is freeze dried to give 
121.57 g of poly(acrylate-co-itaconate), acid form, as a colorless solid. 
The weight average molecular weight, M.sub.W, as determined by low angle 
laser light scattering on a dialyzed portion in 0.2 Molar sodium chloride 
in water (refractive index=1.3344, d.sub.n /d.sub.c =0.1683) is 821,600. 
EXAMPLE IV 
Preparation of another poly(acrylate-co-itaconate) suitable for making 
fiber of the invention (90 mole % acrylate, 10 mole % itaconate) 
Acrylic acid (1050.0 g, 14.571 moles), itaconic acid (210.64 g, 1.6190 
moles), Wako V-50 (4.3919 g, 16.19 millimole), and 7.9 liters of water 
which has been acidified to pH 2.0 with hydrochloric acid are added to a 
22 liter three-necked round-bottomed flask fitted with a thermometer, a 
mechanical stirrer, and gas inlet/outlet adapter capable of bubbling gas 
through a liquid in the flask and venting it. The solution is deaerated by 
passage of nitrogen gas and is then placed under an atmosphere of 
nitrogen. The solution is heated to 55.degree. C. and maintained at this 
temperature for 15 hours. The viscous solution of copolymer is cooled to 
ambient temperature and is freeze dried to give 1,222.1 g of 
poly(acrylate-co-itaconate), acid form, as a colorless solid. The weight 
average molecular weight, M.sub.W, as determined by low angle laser light 
scattering on a dialyzed portion in 0.2 Molar sodium chloride in water 
(refractive index=1.3344, d.sub.n /d.sub.c =0.1683) is 711,700. 
EXAMPLE V 
Preparation of another poly(acrylate-co-itaconate) suitable for making 
fiber of the invention (95 mole % acrylate, 5 mole % itaconate) 
Acrylic acid (25.00 g, 0.3469 mole), itaconic acid (2.376 g, 18.27 
millimole), Wako V-50 (0.0991 g, 0.365 millimole), and 183 ml of water 
which as been acidified to pH 2.0 with hydrochloric acid are added to a 
500 ml three-necked round-bottomed flask. The necks are fitted with a 
thermometer, a stopper, and a gas inlet/outlet adapter capable of bubbling 
gas through a liquid in the flask and venting it. The solution is 
deaerated by passage of nitrogen gas and is then placed under an 
atmosphere of argon. The solution is heated to 55.degree. C. and 
maintained at this temperature for 15 hours. The viscous solution of 
copolymer is cooled to ambient temperature and is dialyzed against 
distilled water overnight (Spectrapor 3 tubing as in the foregoing 
Examples) to remove any unreacted monomers. The dialyzed solution is 
freeze dried to afford 25.99 g of poly(acrylate-co-itaconate), acid form, 
as colorless solid. The weight average molecular weight, M.sub.W, as 
determined by low angle laser light scattering in 0.2 Molar sodium 
chloride in water (refractive index=1.3344, d.sub.n /d.sub.c =0.1683) is 
683,900. 
EXAMPLE VI 
Preparation of another poly(acrylate-co-itaconate) copolymer suitable for 
making fiber of the invention (95 mole % acrylate, 5 mole % itaconate) 
Acrylic acid (21.11 g, 0.2930 mole), itaconic acid (2.0061 g, 15.420 
millimole), Wako V-50 (0.0837 g, 0.309 millimole), and 150 ml of water 
which has been acidified to pH 2.0 with hydrochloric acid are added to a 
250 ml three-necked round-bottomed flask. The necks are fitted with a 
thermometer, a stopper, and a gas inlet/outlet adapter capable of bubbling 
gas through a liquid in the flask and venting it. The solution is 
deaerated by passage of nitrogen gas and is then placed under an 
atmosphere of argon. The solution is heated to 55.degree. C. and 
maintained at this temperature for 15 hours. The viscous solution of 
copolymer is cooled to ambient temperature and a portion is dialyzed 
against distilled water overnight (Spectrapor 3 tubing as in the foregoing 
Examples) to remove any unreacted monomers and then freeze dried to afford 
1.5 g of poly(acrylate-co-itaconate), acid form, as a colorless solid. The 
remainder of the solution is diluted with water to give a 12% solids 
content and is used directly, without drying, in the synthesis of fibers 
in accordance with the invention. The weight average molecular weight, 
M.sub.W, as determined by low angle laser light scattering on the dialyzed 
portion in 0.2 Molar sodium chloride in water (refractive index=1.3344, 
d.sub.n /d.sub.c =0.1670) is 925,000. 
EXAMPLE VII 
Preparation of fiber of the invention 
Poly(arcylate-co-itaconate) of EXAMPLE III (2.00 g) is dissolved by adding 
it portionwise to 20 ml of water while stirring and heating to 
65.degree.-70.degree. C. To the solution is added polyethylene glycol 
(0.334 g, nominal molecular weight 3350) predissolved in 5 ml of water. 
Stirring is continued until dissolution is complete. The resulting aqueous 
medium is cooled to ambient temperature and the pH is adjusted to 3.00 
(the "pH of the aqueous medium" referred to elsewhere herein) with 1 Molar 
sodium hydroxide. Loose fibers of southern softwood Kraft pulp (2.00 g 
bone-dry weight basis) are added. The resulting slurry is thoroughly mixed 
and is spread out into a thin layer on a 6-inch diameter watch glass of 
thickness about 3 mm. The slurry layer is dried in an oven at 
65.degree.-70.degree. C., a temperature selected to minimize or avoid 
crosslinking reactions, and is then cured by placing the watch glass in an 
oven preheated to a curing temperature of 130.degree. C. The curing time 
is 11.5 minutes. The layer, now about 1 mm thick, is cooled to ambient 
temperature. This yields fiber in the acid form, which is not particularly 
absorbent. The fiber is then repulped. In practice it is convenient to 
soak it with distilled water, tear it into small pieces and add it to 400 
ml of distilled water. After further stirring (e.g., overnight) the pH of 
the mixture is adjusted to 2.0 with hydrochloric acid and it is mixed in a 
Waring Blendor in two steps wherein (1) the blendor is run on low speed 
for 5.0 minutes at 50% power and (2) the blendor is run for 1.0 minute on 
low speed at full power. The fibers, still in the acid form, are collected 
by suction filtration in a Buchner funnel fitted with a handsheet forming 
wire, washed the 400 ml of water, and are re-suspended into 500 ml of 
water. The slurry pH is adjusted to 8.5 using 1 Molar sodium hydroxide in 
water. (Using potassium hydroxide or lithium hydroxide instead of sodium 
hydroxide at this stage would result in the potassium or lithium form of 
the fibers.) Over two days, the pH is periodically checked and readjusted 
to 8.5 with sodium hydroxide. During this period, the fibers exchange to 
the sodium salt form, which is highly absorbent. Thus, the fibers swell 
up. The fully swollen fibers of the invention are collected by suction 
filtration and are washed with distilled water. Their wet weight is 232.62 
g and their consistency (Test Method given hereinafter) is determined to 
be 1.656%, from which the Fiber Yield (Test Method given hereinafter) is 
calculated to be 3.85 g of fiber of the invention. The Conversion (Test 
Method given hereinafter) is calculated as about 89%. The WAARV of the 
fiber of this Example (Test Method given hereinafter) is determined as 
96.3 g/g. 
EXAMPLE VIII 
Preparation of fiber of the invention 
Poly(acrylate-co-itaconate) of EXAMPLE IV (25.00 g) is dissolved by adding 
it portionwise to 250 ml of water while stirring and heating to 
65.degree.-70.degree. C. To the solution is added polyethylene glycol 
(4.1667 g, nominal molecular weight 3350) predissolved in 15 ml of water. 
Stirring is continued until dissolution is complete. The resulting aqueous 
medium is now cooled to ambient temperature and the pH is adjusted to 3.00 
with 1 Molar sodium hydroxide. Loose fibers of southern softwood Kraft 
pulp (25.00 g bone-dry weight basis) are added and the resulting slurry is 
mixed thoroughly after each portion of pulp is added. The slurry is spread 
out as a thin, 15-inch by 11-inch layer on a suitably sized 
polytetrafluoroethylene (TEFLON) sheet. The layer is dried in an oven at 
65.degree.-70.degree. C., a temperature selected to minimize or avoid 
crosslinking reactions, and is then cured by removing it from the TEFLON 
(for better air-flow) and placing it into an oven, preheated to a curing 
temperature of 130.degree. C. The curing time is 6.5 minutes. This yields 
a layer about 2 mm thick of acid-form fiber. This is broken into small 
pieces and is added to 3 liters of distilled water. After further stirring 
(e.g., overnight) the pH of the mixture is adjusted to 2.0 with 6 Molar 
hydrochloric acid and it is mixed in a Waring Blendor in two steps wherein 
(1) the blendor is run on low speed for 20 minutes at 50% power and (2) 
the blendor is run for 2.5 minutes on low speed at full power. The 
acid-form fibers are collected by suction filtration in a Buchner funnel 
fitted with a handsheet forming wire and washed with 3 liters of distilled 
water and are re-suspended in another 4 liter aliquot of distilled water. 
The slurry pH is adjusted to 6.5 using 1 Molar sodium hydroxide in water. 
The fibers exchange sodium for hydrogen, at least sufficiently to be 
absorbent. The fibers swell up relatively quickly as compared with Example 
VII. The pH is periodically re-adjusted to 6.5 with sodium hydroxide over 
1 day as the fibers swell. The fibers are collected by suction filtration 
and are washed with distilled water. Their wet weight is 3564.5 g and 
their consistency is determined to be 1.43%, from which the Fiber Yield is 
calculated to be 51.0 g of dry fiber of the invention. The form is 
absorbent, though not necessarily 100% of the cations inherently present 
are sodium: there may be hydrogen cations present. The Conversion is about 
94%. The WAARV of the fiber is determined as 94.8 g/g. 
EXAMPLE IX 
Preparation of fiber of the invention 
The procedure of Example VII is repeated except that the curing time is 
11.0 minutes. The procedure yields fibers having a wet weight of 234.0 g 
and consistency of 1.755%, from which the Fiber Yield is calculated to be 
4.11 g. The conversion is about 95%. The WAARV of the fiber is determined 
to be 86.8 g/g. 
EXAMPLE X 
Preparation of fiber of the invention 
The procedure of Example VII is repeated except that the 
poly(arcylate-co-itaconate) is the product of Example I, the cellulosic 
fiber is chemithermomechanical pulp and the curing time at 130.degree. is 
10.0 minutes. The procedure yields fibers having a wet weight of 170.92 g 
and consistency of 2.58%, from which the Fiber Yield is calculated to be 
4.40 g. The Conversion is about 102% conversion. (percentage in excess of 
100% is a consequence of expressing starting-material 
poly(acrylate-co-itaconate) on an acid basis whereas the product contains 
additional sodium ions). The WAARV is determined to be 79.6 g/g. 
EXAMPLE XI 
Preparation of fiber of the invention 
The procedure of Example VII is repeated except that 
poly(acrylate-co-itaconate) from example I (1.00 g) dissolved in 10 ml of 
water, polyethylene glycol with a nominal molecular weight of 3350 (0.150 
g), and chemithermomechanical pulp (1.00 g on a bone-dry basis) are used. 
The pH of the aqueous medium is 2.00 and the curing time is 14.0 minutes 
at a curing temperature of 130.degree. C. The acid-form fibers are 
repulped in a Waring Blendor for 1 minute on low speed. The procedure 
yields fibers having a wet weight of 130.24 g and consistency of 1.59%, 
from which the Fiber Yield is calculated to be 2.07 g. The Conversion is 
about 96%. The WAARV is determined to be 51.7 g/g. 
EXAMPLE XII 
Preparation of fiber of the invention 
The procedure of Example VII is repeated with the following exceptions: 
poly(acrylate-co-itaconate) is from Example V; the starting-material 
cellulosic fiber is chemithermomechanical pulp; the pH of the aqueous 
medium is 2.00; and the curing time is 15.0 minutes at a curing 
temperature of 130.degree. C. After curing, the acid-form fibers are 
repulped in a Waring Blendor for 1 minute on low speed. The procedure 
yields fibers having a wet weight of 181.56 g and consistency of 2.09%, 
from which the Fiber Yield is calculated to be 3.79 g. The Conversion is 
about 88%. The WAARV is determined to be 46.1 g/g. 
EXAMPLE XIII 
Preparation of fiber of the invention 
The procedure in Example VII is repeated with the following exceptions: 
poly(acrylate-co-itaconate) is from Example V; the cellulosic fiber used 
as starting-material is chemithermomechanical pulp, and the curing time at 
130.degree. C. is 10.0 minutes. After curing, the acid-form fibers are 
repulped in a Waring Blendor for 1 minute on low speed. The procedure 
yields fibers having a wet weight of 205.93 g and consistency of 1.83%, 
from which the Fiber Yield is calculated to be 3.77 g. The Conversion is 
about 87%. The WAARV is determined to be 77.2 g/g. 
EXAMPLE XIV 
Preparation of fiber of the invention 
The procedure in Example VII is repeated with the following exceptions: 
poly(acrylate-co-itaconate) is from Example V and the curing time at 
130.degree. C. is 10.0 minutes. After curing, the acid-form fibers are 
repulped in a Waring Blendor for 1 minute on low speed. The procedure 
yields fibers having a wet weight of 238.86 g and consistency of 1.72%, 
from which the Fiber Yield is calculated to be 4.11 g. The Conversion is 
about 96%. The WAARV is determined to be 97.8 g/g. 
EXAMPLE XV 
Preparation of fiber of the invention 
The procedure in Example VII is repeated with the following exceptions: 
poly(acrylate-co-itaconate) is from Example VI (16.67 g of the 12% solids 
solution are used); the cellulosic fiber used as starting-material is 
chemithermomechanical pulp; the pH of the aqueous medium is 2.00; and the 
curing time at 130.degree. C. is 14.0 minutes. After curing, the acid-form 
fibers are repulped in a Waring Blendor for 1 minute on low speed. The 
procedure yields fibers having a wet weight of 230.0 and consistency of 
1.61%, from which the Fiber Yield is calculated to be 3.71 g. The 
Conversion is about 86%. The WAARV is determined to be 97.8 g/g. 
EXAMPLE XVI 
Preparation of fiber of the invention 
The procedure in Example VII is repeated with the following exceptions: 
poly(acrylate-co-itaconate) is from Example VI (16.67 g of the 12% solids 
solution are used); the cellulosic fiber used as starting-material is 
chemithermomechanical pulp; and the curing time at 130.degree. C. is 10.0 
minutes. The procedure yields fibers having a wet weight of 230.52 g and 
consistency of 1.76%, from which the Fiber Yield is calculated to be 4.06 
g. The Conversion is about 94%. The WAARV is determined to be 82.6 g/g. 
EXAMPLE XVII 
Preparation of fiber of the invention 
The procedure of Example VII is repeated with the following exceptions: 
poly(acrylate-co-itaconate) is from Example II and the curing time at 
130.degree. C. is 11.0 min. The procedure yields fibers having a wet 
weight of 266.02 g and consistency of 1.455%, from which the Fiber Yield 
is calculated to be 3.87 g. The Conversion is about 89%. The WAARV is 
determined to be 99.4 g/g. 
EXAMPLE XVIII 
Preparation of fiber of the invention 
The procedure of Example VII is repeated with the following exceptions: 
poly(acrylate-co-itaconate) is from Example II and the curing time at 
130.degree. C. is 12.0 min. The procedure yields fibers having a wet 
weight of 120.73 g and consistency of 3.81%, from which the Fiber Yield is 
calculated to be 4.60 g. The Conversion is about 106%. The WAARV is 
determined to be 62.8 g/g. 
EXAMPLE XIX 
Preparation of fiber of the invention 
The procedure of Example VII is repeated with the following exceptions: 
poly(acrylate-co-itaconate) is from Example II and the curing time at 
130.degree. C. is 13.0 min. The procedure yields fibers having a wet 
weight of 101.06 g and consistency of 4.53%, from which the Fiber Yield is 
calculated to be 4.57 g. The Conversion is about 106%. The WAARV is 
determined to be 49.2 g/g. 
EXAMPLE XX 
Preparation of fiber of the invention 
The procedure of Example VII is repeated with the following exceptions: 
poly(acrylate-co-itaconate) is from Example II and the curing time at 
130.degree. C. is 14.0 min. The procedure yields fibers having a wet 
weight of 110.12 g and consistency of 4.19%, from which the Fiber Yield is 
calculated to be 4.61 g. The Conversion is about 106%. The WAARV is 
determined to be 43.2 g/g. 
EXAMPLE XXI 
Preparation of fiber of the invention 
The procedure of Example VII is repeated with the exception that the pH of 
the aqueous medium is 2.5. The procedure yields fibers having a wet weight 
of 314.51 g and consistency of 1.164%, from which the Fiber Yield is 
calculated to be 3.66 g. The Conversion is about 85%. The WAARV is 
determined to be 125.8 g/g. 
EXAMPLE XXII 
Preparation of fiber of the invention 
The procedure of Example VII is repeated with the exception that the pH of 
the aqueous medium is 3.5. The procedure yields fibers having a wet weight 
of 110.99 g and consistency of 3.955%, from which the Fiber Yield is 
calculated to be 4.39 g. The Conversion is about 100%. The WAARV is 
determined to be 17.8 g/g. 
EXAMPLE XXIII 
Preparation of fiber of the invention 
The procedure of Example VII is repeated except that the pH of the aqueous 
medium is 4.0. The procedure yields fibers having a wet weight of 185.36 g 
and consistency of 2.25%, from which the Fiber Yield is calculated to be 
4.17 g. The Conversion is about 96%. The WAARV is determined to be 43.1 
g/g. 
EXAMPLE XXIV 
Preparation of fiber of the invention 
The procedure of Example VII is repeated with the exception that 
polyethylene glycol with a nominal molecular weight of 200 (0.060 g) is 
used as the polyol. The procedure yields fibers having a wet weight of 
128.57 g and consistency of 2.88%, from which the Fiber Yield is 
calculated to be 3.71 g. The Conversion is about 91%. The WAARV is 
determined to be 21.9 g/g. 
EXAMPLE XXV 
Preparation of fiber of the invention 
The procedure of Example VII is repeated except that polyethylene glycol 
with a nominal molecular weight of 1000 (0.100 g) is used as the polyol. 
The procedure yields fibers having a wet weight of 228.00 g and 
consistency of 1.56%, from which the Fiber Yield is calculated to be 3.56 
g. The Conversion is about 87%. The WAARV is determined to be 50.8 g/g. 
EXAMPLE XXVI 
Preparation of fiber of the invention 
The procedure of Example VII is repeated except that polyethylene glycol 
with a nominal molecular weight of 1500 (0.150 g) is used as the polyol. 
The procedure yields fibers having a wet weight of 211.74 g and 
consistency of 1.85%, from which the Fiber Yield is calculated to be 3.91 
g. The Conversion is about 94%. The WAARV is determined to be 83.7 g/g. 
EXAMPLE XXVII 
Preparation of fiber of the invention 
The procedure of Example VII is repeated except that polyethylene glycol 
with a nominal molecular weight of 6800 (0.500 g) is used as the polyol. 
The procedure yields fibers having a wet weight of 138.48 g and 
consistency of 2.87%, from which the Fiber Yield is calculated to be 3.98 
g. The Conversion is about 88%. The WAARV is determined to be 76.8 g/g. 
EXAMPLE XXVIII 
Preparation of fiber of the invention 
The procedure of Example VII is repeated with the following exceptions: 
poly(acrylate-co-itaconate) copolymer is from Example II (1.00 g dissolved 
in 20 ml of water); the polyol is polyethylene glycol with a nominal 
molecular weight of 3350 (0.100 g); the starting-material cellulosic fiber 
is chemithermomechanical pulp (2.00 g on a bone-dry basis); the pH of the 
aqueous medium is 2.00 and the curing time at 130.degree. C. is 14.0 
minutes. After curing, the fibers are repulped in a Waring Blendor for 1 
minute on low speed. The procedure yields fibers having a wet weight of 
115.30 g and consistency of 2.54%, from which the Fiber Yield is 
calculated to be 2.93 g. The Conversion is about 95%. The WAARV is 
determined to be 24.1 g/g. 
EXAMPLE XXIX 
Preparation of fiber of the invention 
The procedure of Example VII is repeated with the following exceptions: 
poly(acrylate-co-itaconate) is from Example II (1.80 g dissolved in 30 ml 
of water); the polyol is polyethylene glycol with a nominal molecular 
weight of 3350 (0.300 g); the starting-material cellulosic fiber is 
chemithermomechanical pulp (3.00 g on a bone-dry basis); the pH of the 
aqueous medium is 2.00 and the curing time at 130.degree. C. is 14.0 
minutes. After curing, the chemically modified fibers are repulped in a 
Waring Blendor for 1 minute on low speed. The procedure yields fibers 
having a wet weight of 186.77 g and consistency of 2.57%, from which the 
Fiber Yield is calculated to be 4.80 g. The Conversion is about 95%. The 
WAARV is determined to be 35.9 g/g. 
EXAMPLE XXX 
Preparation of wet-laid paper comprising fiber of the invention (Example 
VII) in admixture with conventional fiber 
A slurry of northern softwood Kraft pulp (NSK) is prepared by repulping NSK 
dry-lap (1.75 g bone-dry basis) in 400 ml of distilled water in a Waring 
Blendor on low speed for 1.0 minute. The slurry is placed in a 1 liter 
beaker and to it is added fiber of the invention (sodium form, made 
according to Example VII but never dried, 0.75 g bone-dry basis, in 100 ml 
of distilled water). The pH of the slurry is adjusted to 8.5 with 0.1 
Molar sodium hydroxide and the slurry is stirred for 1 hour. A deckle box 
is fitted with a forming wire (Albany International-Appelton Wire 
Division, Appelton, Wis.; Handsheet style/mesh 78-S) and is filled with 
distilled water which is also adjusted to pH 8.5 with 1 Molar sodium 
hydroxide. The slurry is added and the water is drained by suction. The 
wet paper sheet (handsheet) thus formed is transferred to a drying fabric 
(albany International-Appelton Wire Division, Appelton, Wis.; Handsheet 
style/mesh 36-C) by passage over a vacuum slit on low setting. The drying 
fabric is passed over the vacuum slit two additional times on high setting 
and then another fabric is placed on top of the wet handsheet. The 
sandwhich is passed through a drum dryer at 230.degree. F. until the sheet 
is dry. This gives a 2.50 g handsheet (basis weight=16.5 lbs/3,000 square 
feet) containing 30% by weight of fiber of the invention. This handsheet 
is quick-wicking and has a WAARV of 22.6 g/g. The handsheet can be wetted 
and re-dried: on rewet, it is found to have preserved good absorbency and 
wicking characteristics. 
EXAMPLE XXXI 
Preparation of wet-laid paper comprising fiber of the invention (Example 
VIII) in admixture with conventional fiber. 
The procedure of Example XXX is repeated except that the fiber of the 
invention of Example VIII is used. The WAARV of the handsheet is 
determined to be 10.7 g/g. 
EXAMPLE XXXII 
Preparation of wet-laid paper comprising fiber of the invention (Example 
IX) in admixture with conventional fiber 
The procedure of Example XXX is repeated except that the fiber of the 
invention of Example IX is used. The WAARV of the handsheet is determined 
to be 24.7 g/g. 
EXAMPLE XXXIII 
Preparation of wet-laid paper comprising fiber of the invention (Example X) 
in admixture with conventional fiber 
The procedure of Example XXX is repeated except that the fiber of the 
invention of Example X is used. The WAARV of the handsheet is determined 
to be 23.7 g/g. 
EXAMPLE XXXIV 
Preparation of wet-laid paper comprising fiber of the invention (Example 
XI) in admixture with conventional fiber 
The procedure of Example XXX is repeated except that the fiber of the 
invention of Example XI is used. The WAARV of the handsheet is determined 
to be 20.7 g/g. 
EXAMPLE XXXV 
Preparation of wet-laid paper comprising fiber of the invention (Example 
XII) in admixture with conventional fiber 
The procedure of Example XXX is repeated except that the fiber of the 
invention of Example XII is used. The WAARV of the handsheet is determined 
to be 19.8 g/g. 
EXAMPLE XXXVI 
Preparation of wet-laid paper comprising fiber of the invention (Example 
XIII) in admixture with conventional fiber 
The procedure of Example XXX is repeated except that the fiber of the 
invention of Example XIII is used. The WAARV of the handsheet is 
determined to be 18.7 g/g. 
EXAMPLE XXXVII 
Preparation of wet-laid paper comprising fiber of the invention (Example 
XIV) in admixture with conventional fiber 
The procedure of Example XXX is repeated except that the fiber of the 
invention of Example XIV is used. The WAARV of the handsheet is determined 
to be 15.5 g/g. 
EXAMPLE XXXVIII 
Preparation of wet-laid paper comprising fiber of the invention (Example 
XV) in admixture with conventional fiber 
The procedure of Example XXX is repeated except that the fiber of the 
invention of Example XV is used. The WAARV of the handsheet is determined 
to be 29.2 g/g. 
EXAMPLE XXXIX 
Preparation of wet-laid paper comprising fiber of the invention (Example 
XVI) in admixture with conventional fiber 
The procedure of Example XXX is repeated except that the fiber of the 
invention of Example XVI is used. The WAARV of the handsheet is determined 
to be 19.8 g/g. 
EXAMPLE XL 
Preparation of wet-laid paper comprising fiber of the invention (Example 
XVII) in admixture with conventional fiber 
The procedure of Example XXX is repeated except that the fiber of the 
invention of Example XVIII is used. The WAARV of the handsheet is 
determined to be 18.6 g/g. 
EXAMPLE XLI 
Preparation of wet-laid paper comprising fiber of the invention (Example 
XVIII) in admixture with conventional fiber 
The procedure of Example XXX is repeated except that the fiber of the 
invention of Example XVIII is used. The WAARV of the handsheet is 
determined to be 9.6 g/g. 
EXAMPLE XLII 
Preparation of wet-laid paper comprising fiber of the invention (Example 
XIX) in admixture with conventional fiber 
The procedure of Example XXX is repeated except that the fiber of the 
invention of Example XIX is used. The WAARV of the handsheet is determined 
to be 7.0 g/g. 
EXAMPLE XLIII 
Preparation of wet-laid paper comprising fiber of the invention (Example 
XX) in admixture with conventional fiber 
The procedure of Example XXX is repeated except that the fiber of the 
invention of Example XX is used. The WAARV of the handsheet is determined 
to be 5.7 g/g. 
EXAMPLE XLIV-LII 
Preparation of wet-laid paper comprising fiber of the invention 
The procedures of Examples XXX-XLIII are repeated except that 2.00 g of 
northern softwood Kraft dry-lap (bone-dry basis) and 0.50 g of the fiber 
of the invention (bone-dry basis) are used. This give 2.50 g handsheets 
(basis weight=16.5 lbs./3,000 square feet) containing 20% by weight of the 
fiber of the invention. The results are as follows. 
______________________________________ 
Example No. Handsheet WAARV (g/g) 
______________________________________ 
XLIV 15.6 
XLV 8.5 
XLVI 13.2 
XLVII 14.0 
XLVIII 10.0 
XLIX 12.8 
L 11.6 
LI 11.8 
LII 19.0 
LIII 13.1 
LIV 13.4 
LV 6.4 
LVI 6.8 
LVII 5.6 
______________________________________ 
TEST METHODS 
Weight average molecular weight of poly(acrylate-co-itaconate) 
Weight average molecular weights, M.sub.W, of copolymer samples are 
determined by low angle laser light scattering using a KMX-6 Chromatix 
Polymer Analyzer (flow injection method). The change in refractive index 
with concentration, d.sub.n /d.sub.c, is measured on a KMX-16 Laser 
Differential Refractometer at 25.degree. C. after the copolymer solutions 
are dialyzed against 0.2 Molar sodium chloride in water. The intercept of 
a linear regression analysis of a plot of K.sub.C /R.sub.theta versus c is 
given by 1/M.sub.W, where K=a(n).sup.2 (d.sub.n /d.sub.c).sup.2 (the 
constant a being characteristic of the particular instrument), 
c=concentration of copolymer, and R.sub.theta is the Rayleigh scattering 
for a given copolymer solution. Typically, the concentrations of copolymer 
used for molecular weight determinations are 1.0, 1.5, 2.0, 2.5, and 3.0 
mg/ml. 
pH of aqueous medium; pH in general 
In general, pH herein is determined using a conventional digital pH meter 
which has an accuracy of .+-.0.01 pH units (Markson model 88). The meter 
is equipped with a flat surface electrode, which has a peripheral porous 
polyethylene junction (Markson 12008B). The electrode is particularly 
suited for measuring the pH of slurries, viscous solutions and wet 
surfaces. As an alternative, a conventional polymer-gel-filled pH 
electrode may be used. pH measurements are made at ambient temperature, in 
the range 20.degree. C.-25.degree. C. The electrodes are calibrated in the 
conventional manner, using pH 7.00 and pH 4.00 buffers. 
It is specifically noted that the above-identified equipment and procedure 
is used for measuring pH of the aqueous medium discussed hereinabove in 
the specification. 
Consistency 
Consistency, such as of wet fiber of the invention, is defined as 
percentage by weight of a specified fiber, in a slurry, fiber dispersion 
or wet fiber mass. Measurement is carried out by placing a sample of wet 
material sufficient to give at least about 0.1 gram of bone dry fiber on a 
Mettler PM460 balance which is equipped for moisture determination 
(infra-red dryer model LP16), weighing wet followed by continuous 
monitoring of weight during drying (90.degree. C. temperature setting) to 
constant weight. 
Fiber Yield 
Fiber Yield is defined as the weight in grams, dry basis, of fiber of the 
invention, sodium form. It is conveniently measured by multiplying the 
weight of wet, swollen fibers of the invention by the consistency. 
Conversion 
Conversion is defined as the yield of fiber of the invention expressed in 
percentage terms. It is calculated by dividing the Fiber Yield by the sum 
of weights of starting-materials, more specifically the sum of weights, 
bone dry basis, of poly(acrylate-co-itaconate) plus polyol plus cellulosic 
fiber starting-material. 
In determining Conversion, the weight of poly(acrylate-co-itaconate) in the 
above is expressed on an acid equivalent basis. That is to say, regardless 
of the form of the poly(acrylate-co-itaconate) used in the synthesis of 
the fiber of the invention, and equally regardless of the form of the 
product fiber, the convention is adopted of everywhere specifying the 
poly(acrylate-co-itaconate) weight as though it were in the acid form, 
i.e., all the charge-balancing cations are H. In this manner, the relative 
proportion of poly(acrylate-co-itaconate) to the cellulose and polyol 
components is unambiguously determined. 
As noted hereinabove, Conversion can be slightly in excess of 100% 
(typically up to about 106%) as a consequence of cation weight gain. Thus 
when the poly(acrylate-co-itaconate) starting-material is in the acid form 
and the fiber of the invention is secured in the sodium form, the heavier 
sodium cation as compared with hydrogen cations accounts for the 
additional weight gain. 
Water absorbency and retention value (WAARV) of fiber of the invention and 
WAARV of wet-laid paper containing same 
The following is a gravimetric water-absorbency and retention-measuring 
method applicable to characterizing the fibers, pulps or paper webs 
according to the invention. For purposes of comparison, typical 
papermaking pulp such as Kraft pulp measures of the order of about 3-4 
grams of water per gram of fiber at pH 8.5 ("g/g") by this method and 
paper webs made from such pulp have similar or slightly lower values. 
Equipment is as follows: 
Sample holders: glass cylinders open at both ends, 1.8 cm. inside diameter, 
4.2 cm height. 
Tea-bag material: Tea-bag paper, grade 1234T, obtainable from C. H. Dexter 
Division of the Dexter Corp., Windsor Locks, Conn. This paper is cut into 
4.7.times.9.5 cm rectangles. The purpose of the tea-bag material is to 
provide a substantially non-absorbent pulp-retaining material through 
which water will pass during centrifugation, and which acts to prevent the 
possibility of obtaining artificially high pulp absorbencies, which might 
otherwise occur, e.g., if the pulp were allowed to block the constriction 
in the centrifuge tube. 
Balance: 0.0001 g sensitivity. 
Centrifuge: clinical model, variable speed, with a swinging bucket rotor, 
four 29.4 mm. inside diameter.times.95 mm depth shields, and tachometer 
adapted to measure centrifuge speed. 
Centrifuge tubes: designed with a constriction so that on centrifuging, the 
water will separate into the lower half of the tube, leaving the sample 
and "tea-bag" in the upper half. 
Drying beakers: 10 ml capacity. 
Vacuum oven: capable of approximately 250 mTorr vacuum, heating to at least 
110.degree. C.; temperature thermostatted at 60.degree. C. 
Convection oven: thermostatted at 105.degree. C. 
Soaking beakers: 150 ml capacity. 
For each absorbency determination, a number of replicated measurements 
(typically two will suffice provided that the results are in good 
agreement) are made, each based on the following procedure: 
Weigh a tea-bag paper. The weight is the Initial Teabag Weight (Initial 
Teabag Weight=ITB) and is typically of the order of 70 mg. 
Place the fiber or paper (shredded in small pieces) which is to be tested 
for absorbency into a 150 ml beaker. Add 100 ml distilled water. Adjust pH 
to 8.5 with aqueous sodium hydroxide. Equilibrate by allowing to stand for 
about 2 hours. 
Fold a weighed tea-bag paper to make a cylindrically shaped holder having 
one end closed and the other end open. Place it inside a glass cylinder. 
Into the shaped tea-bag, place wet equilibrated material to be tested, 
allowing excess water to drain through the tea-bag, until the tea-bag is 
substantially full with wet fiber. (Typically when the sample to be tested 
in fiber of the invention, the sample size is sufficient to contain about 
100 mg bone dry fiber; when the sample to be tested is a wet-laid paper 
containing the fiber of the invention, the sample size is sufficient to 
contain about 300 mg in total of all fiber present; and when the sample to 
be tested is conventional fiber, e.g., northern softwood Kraft, the sample 
size is sufficient to contain about 500 mg of fiber. Slip the tea-bag out 
of the glass cylinder or holder and, preserving the cylindrical shape of 
the tea-bag, place it and its sample contents in a centrifuge tube. 
Centrifuge at approximately 125 "g" (gravities) force for 10 minutes, 
centifuge speed-up time not included. Place the centrifuged sample and 
tea-bag in an accurately preweighed dry beaker (dry beaker weight=DBW). 
Weigh the centrifuged sample, tea-bag and beaker (weight=W.sub.1). Dry in 
the 105.degree. C. convection oven for 3 hours. Further dry in the vacuum 
oven for 6 hours or more. Allow to cool in a desiccator. Weigh 
(weight=W.sub.2). The water absorbency and retention value (WAARV) of the 
sample (g/g) is given by the following formula: 
EQU WAARV=(WPW-DPW)/DPW 
wherein WPW=wet pulp weight=W.sub.1 -(ITB+DBW) and DPW=dry pulp 
weight=W.sub.2 -(ITB+DBW). In principle, it is possible to measure WAARV 
absorbency at pH values other than 8.5 of the above-specified method. 
However, unless there is a specific mention of another pH, any WAARV 
absorbency value quoted throughout the instant specification and claims, 
expressed simply in g/g, is strictly to be construed as a measurement at a 
pH of 8.5.