Process for imparting lubricity to fiberfill fiber

A process for imparting lubricity to fibers which comprises applying a graft copolymer of an N-(oxymethyl)-acrylamide and a poly(oxyalkylene) to the surface of the fiber and crosslinking the graft copolymer on the surface of the fiber.

TECHNICAL FIELD 
This invention pertains to the art of applying polymeric finishes to 
textile fibers. 
BACKGROUND OF THE INVENTION 
Unfinished polyester fiberfill fibers exhibit fiber scroop and a rough hand 
due to high interfiber friction. It is known in the art that an silicone 
finish will lower interfiber friction and thereby make polyester fiberfill 
fibers acceptable for commercial uses where fiber scroop can be a problem. 
For example, Dacron Hollofil II available from E. I. duPont de Nemours is 
finished with a silicone which lowers the interfiber friction associated 
with fiberfill fibers and thereby imparts a soft, down-like, hand. 
However, silicone finishes adversely affect the flammability and latex 
bondability of polyester fiberfill fibers. 
It is also known in the art of fabric finishing that a crosslinkable 
organic polymer, when applied to a synthetic fabric, will reduce the 
static electricity associated with such fabrics. For example, U.S. Pat. 
No. 3,213,053 to Kendrick discloses that an antistatic composition of a 
crosslinkable terpolymer of: (1) 5% to 10% of glycidyl methacrylate; (2) 
35% to 55% of an alkali metal salt of a styrene sulfonate; and (3) 35% to 
60% of methoxypoly(ethylene glycol) methacrylate wherein the poly(ethylene 
glycol) chain has a molecular weight from 250 to 500, will reduce the 
static electricity of a synthetic fabric when applied as a finish. 
Likewise, French Pat. No. 1,427,787 discloses that a copolymer of: (1) 
from 2% to 20% of an ethylenically unsaturated epoxide or a corresponding 
methylol compound; with (2) from 98% to 80% of an ester of an 
ethylenically unsaturated carboxylic acid and an alkylphenoxy polyethylene 
glycol, will reduce the static electricity or synthetic fabrics when 
applied to said fabrics as a fabric finish. Similarly, Swiss Pat. No. 
513,282 discloses that a copolymer composed of: (1) from 80% to 90% of an 
ester of an alkyl polyethylene glycol having an alkyl residue with 1 to 3 
carbon atoms and an average molecular weight of from 300 to 1000 and an 
ethylenically unsaturated polmerizable carboxylic acid; (2) 5% to 10% of a 
etherified N-methylolamide of an ethylenically unsaturated polymerizable 
carboxylic acid; and (3) 5% to 10% of an ethylenically unsaturated 
polymerizable compound containing at least one acid group capable of 
imparting solubility in water, e.g. acrylic acid; will reduce the static 
electricity associated with a synthetic fabric and enhance the soil 
release properties of such a fabric. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, it has been found that the 
process which comprises 
(a) treating fibers with a neat composition, solution or dispersion 
containing: 
(i) from about 0.1% to about 5% by solution weight or neat composition 
weight of an acid catalyst, and 
(ii) at least about 0.001% by solution weight or neat composition weight of 
a graft copolymer prepared by grafting to a poly(oxyalkylene) from about 
0.5% to about 50% by graft copolymer weight of an N-(oxymethyl)-acrylamide 
having the formula: 
##STR1## 
wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are hydrogen or monovalent 
hydrocarbon radicals containing from 1 to about 6 carbon atoms each and 
may be the same or different and a poly(oxyalkylene) of the formula: 
EQU R.sup.5 [(OC.sub.n H.sub.2n).sub.z XR.sup.6]a 
wherein R.sup.5 is a hydrocarbon radical having a valence of a and 
containing up to about 21 carbon atoms, a is an integer having values 
between 1 and 4, X is an oxygen, nitrogen or sulfur atom, R.sup.6 is a 
hydrogen atom or hydrocarbon radical containing up to about 6 carbon atoms 
and may contain hydroxyl, amino or mercaptyl groups, n is an integer from 
2 to 4 and z is an integer having a value from about 2 to about 800, and 
(b) drying and curing said treated fiber at between about 100.degree. C. 
and about 170.degree. C., imparts to the fiber a durable finish 
which increases the lubricity of the fiber manifested by a lowering of 
interfiber friction without adversely affecting the flammability or the 
latex bondability of the fiber. 
The graft copolymers useful in the present invention may be prepared as 
described in copending application Ser. No. 307,211 filed Sept. 30, 1981. 
DETAILS OF THE INVENTION 
Graft copolymers useful in the present invention having an N-(oxymethyl) 
acrylamide grafted onto a poly(oxyalkylene) compound are prepared by a 
method which comprises adding an N-(oxymethyl) derivative of acrylamide 
monomer as hereinafter more fully described and a suitable catalyst to an 
agitated bath of the poly(oxyalkylene), whereby all of said components are 
intimately admixed at a temperature at which reaction occurs, and 
maintaining said temperature until said graft copolymer of acrylamide 
derivative on poly(alkylene oxide) is obtained. 
The poly(oxyalkylene) compounds used to make. the graft copolymers of the 
invention are known in the art and have the formula: 
EQU R.sup.5 [(OC.sub.n H.sub.2n).sub.z XR.sup.6 ]a 
wherein R.sup.5 is a hydrocarbon radical containing up to 10 carbon atoms 
and has a valence of a, a is an interger having a value of 1 to 4, R.sup.6 
is a hydrogen atom or a monovalent hydrocarbon radical containing up to 6 
carbon atoms and may contain hydroxyl (--OH) amino (--MH.sub.2) or 
mercaptyl (--SH.sub.2) groups. X is an oxygen, nitrogen or sulfur atom, n 
is an integer from 2 to 4, and z is an integer having a value of about 2 
to about 800. 
In general, these compounds contain oxyethylene, oxypropylene, oxybutylene 
groups or both oxyethylene groups and higher oxyalkylene groups such as 
oxypropylene and oxybutylene groups, either in random or block 
distribution in their molecules, and have molecular weights (number 
average) in the range of about 100 to about 35,000, and, preferably, in 
the range of about 1,500 to 4,000. These poly(oxyalkylene) compounds may 
be made by processes well known in the art by reacting an alkylene oxide 
or mixtures of alkylene oxides with an aliphatic compound which may be 
saturated or contain some aliphatic unsaturation, having from one up to as 
many as four active hydrogen atoms, such as water, monohydroxylic alcohols 
such as ethanol, propanol, and allyl alcohol; dihydroxylic alcohols such 
as ethylene glycol and monoethylether of glycerine; trihydroxylic alcohols 
such as glycerine and trimethylolpropane; and tetrahydroxylic alcohols 
such as sorbitol. Especially preferred active hydrogen compounds are allyl 
alcohol and glycerine. The poly(oxyalkylene) products of such reactions 
will have linear or branched oxyalkylene or mixed oxyalkylene chains, and 
such chains will terminate with hydroxyl groups. Although the preferred 
poly(oxyalkylenes) are hydroxyl terminated, some or all of these hydroxyl 
groups may be etherified by reaction with a dialkyl sulfate such as 
diethyl sulfate. These terminal hydroxyl groups may also be etherified 
with alkyl-halohydrins such as 2-chloro ethanol. This will yield a 
poly(oxyalkylene) that has a terminal hydroxyl group which is preferred 
because of its ability to condense with the N-(oxymethyl) functionality 
that is introduced into the poly(oxyalkylene) to facilitate crosslinking 
of the poly(oxyalkylene) chains. 
The grafting monomers employed in preparing the copolymers useful in the 
present invention are substituted acrylamide monomers having the formula 
##STR2## 
wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 may be the same or different 
and are hydrogen atoms or a monovalent hydrocarbon radicals containing 
from 1 to about 6 carbon atoms. These acrylamide derivative monomers are 
generally homopolymerizable monomers with a reactive cross linkable 
pendent group or groups. Illustrative suitable monomers are methoxymethyl 
acrylamide, ethyoxymethyl acrylamide, N-butoxymethyl acrylamide, 
allyloxymethyl acrylamide, N-butoxymetharylamide and preferably, 
N-methylolacrylamide and N-(iso-butoxymethyl)-acrylamide. 
A catalyst is employed in the process of the invention which is a free 
radical initiator. The choice of such initiator is important because it 
should be active at a temperature below 160.degree. C. but any one of a 
wide variety of known inorganic or organic free radical initiators may be 
used. The choice of initiator will generally depend on the particular 
combination of reactants from which the graft copolymer will be prepared. 
Exemplary of suitable initiators are azobisisobutyronitrile; 
hydroperoxides such as t-butyl peroxypivalate, di-t-butyl peroxide, and 
t-butyl perbenzoate; peroxycarbonates such as diethyl peroxydicarbonate 
and diisopropyl peroxycarbonate; and persulfates such as potassium and 
sodium persulfates. 
Homogeneous graft copolymers useful in the present invention which are 
substantially free (contain less than 2 percent by weight) of insoluble 
homopolymerized acrylamide derivative may be prepared by methods known in 
the art but preferably are prepared by charging the reactants in two 
separate feed streams, advantageously in gradual and/or incremental 
amounts, one of which consists of the grafting monomer and a second 
consisting of the free radical grafting initiator. Either of the reactants 
may be mixed with a portion of the poly(oxyalkylene) compound prior to 
feeding them to the reaction zone when doing so facilitates the gradual or 
incremental feeding thereof to the reaction mixture. The amount of 
acrylamide derivative added to the polymerization reactor zone is not 
critical and may be varied over a wide range. The preferred range is from 
about 6% to about 12% by weight of poly(oxyalkylene). In general, however, 
up to about 70 percent by weight, and preferably from about 0.5 percent by 
weight to about 50 percent by weight based on the total weight of 
poly(alkylene oxide) compound, is charged. 
The temperatures at which the graft reaction may be carried out may vary 
over a wide range and depend, in general, upon the combination of 
reactants to be used in the reaction. For example, when organic free 
radical grafting initiators are employed, a temperature sufficient to 
activate the initiator to about 160.degree. C. can be used in the grafting 
reacting, and preferably, a temperature in the range from about 70.degree. 
C. to about 100.degree. C. Where employing inorganic free radical 
initiators, a temperature from about above the freezing point of the 
solvent to about 65.degree. C. may be employed. Reaction temperatures 
above 160.degree. C. lead to gelling of the reaction mixture, and should 
be avoided. 
Incremental and/or gradual addition of the two separate reactant feed 
streams coupled with efficient agitation of the poly(oxyalkylene) compound 
in the reaction zone constitutes the most important technique for 
producing the graft copolymers useful in the present invention. This 
method is particularly important in large scale or commercial operations, 
not only for preparing the desired homogenous graft compolymer, but also 
to facilitate handling and storage of the monomer and the free radical 
initiator. 
The grafting reaction is preferably carried out in bulk without the use of 
a solvent. If desired, however, a solvent may be used which is inert to 
the reactants. Suitable solvents include benzene, toluene, 
tertiary-butylbenzene, heptane, hexane, or octane, and mixtures thereof, 
and water. 
The preferred graft copolymers are made from a 
poly(oxyethylene-co-oxypropylene) copolymer of molecular weight in the 
range of 350 g/mol to 4000 g/mol and which are at least 40% ethylene oxide 
monomer by weight of the polymer. The upper limit is not critical as 
longer chain polymers have been found to impart better lubricity, however; 
the high viscosity of a very high molecular weight poly(oxyalkylenes) may 
make the use of such polymers difficult. The preferred poly(oxyalkylenes) 
have been treated with a sufficient amount of N-methylol-acrylamide or 
N-(isobutoxymethyl)-acrylamide in a grafting reaction such that at least 
an average of 11/2 N-(oxymethyl)-acrylamides molecules are grafted onto 
each poly(oxyalkylene) molecule and most preferably an average of from 3 
to 6 N-(oxymethyl)-acrylamide molecules per poly(oxyalkylene) molecule. 
An optional component of the fiber treating solution is an antioxidant that 
will inhibit the degradation of the poly(oxyalkylene) polymer thereby 
improving the durability of the "fiber finish." Such antioxidants are well 
known in the art of stabilizing poly(oxyalkylenes) and may include any 
number of antioxidant compounds. Especially suitable are hindered phenolic 
compounds such as Bisphenol A, BHA and BHT. The amount of such an 
antioxidant is not critical and generally ranges from about 1% to about 3% 
by weight of the treating composition or solution. 
The graft copolymer is then mixed with an acid catalyst and applied to the 
fiber to be treated. 
Although the examples given herein are directed to the practice of the 
instant invention with fiberfill fibers, it is believed that the instant 
invention will impart lubricity to any synthetic fiber, e.g. a textile 
fiber. It is to be understood that the phrase fiberfill fiber is intended 
to mean any non-woven bating or fiber mat. Although all the examples shown 
herein are limited to carded polyester fibers it is believed that 
non-carded, non-polyester fibers will exhibit similar properties when 
treated by the process of the instant invention. In addition to the 
Hollofil-808 fibers available from E. I. duPont de Nemours that are 
exemplified herein, other fiberfill fibers such as the round, solid fiber 
available from Hoechst are useful in the instant invention. 
The choice of acid catalyst suitable for use in the invention is not 
critical and may depend on economic or toxicological factors. Any acid 
that will lower the pH sufficiently to make the solution weakly acidic 
will catalyze the crosslinking of the graft copolymer on the fabric 
surface. Examples of acid catalysts include inorganic acids such as 
hydrochloric, hydrobromic, sulfuric and nitric acids; organic acids such 
as carboxylic acids, phenols, aklyl and aryl sulfonic acids and the like. 
Lewis acids such as zinc fluoroborate and the like will also catalyze the 
graft copolymer cross-linking on the surface of the fabric. An acid 
catalyst that is particularly suitable for use in the instant invention is 
citric acid because of its commercial availability and non-toxicity. In a 
most preferred embodiment, the acid catalyst chosen is water soluble 
because an aqueous solution is a convenient medium with which to apply the 
graft copolymer to the fiber. 
The graft copolymer and acid catalyst may be applied as a neat composition 
or a solution. Any solvent which will dissolve the graft copolymer may be 
used. Suitable solvents include water, alcohols, ketones, esters or 
mixtures thereof that will dissolve the graft copolymer and the acid 
catalyst. When water is used as the solvent, a functional additive such as 
an anionic or nonionic surfactant may be added to facilitate the initial 
wetting of the fiber. In a most preferred embodiment, the graft copolymer 
and acid catalyst are added to water to form a treatment solution that is 
from 1/2% to 15% by solution weight of graft copolymer and 0.001% to 2% by 
solution weight of an acid catalyst. 
The solution may be applied in any manner that is effective to wet the 
fiber with the solution. If the fiber is deposited in a bath containing 
the treatment solution, the residence time in the bath need only be so 
long as to allow the fabric to be substantially wetted by the solution. 
The addition of wetting agents such as surfactants will reduce the 
necessary residence time. The temperature of the treatment solution is not 
critical so long as it is maintained below the temperature that will 
cross-link the graft copolymer in solution with the acid catalyst. The 
treated fiber is then heated at a temperature and for a period of time 
sufficient to dry the fiber and cure the graft copolymer on the fiber 
surface. Generally, a few minutes in an oven at between 100.degree. C. and 
170.degree. C. is sufficient, but the actual time and temperature 
necessary will depend primarily upon the catalyst and solvent chosen. 
The dried, treated fiber is then ready for further processing with the 
graft copolymer cross-linked on the surface of the fiber as a durable, 
lubricating fiber finish. Any residual acid catalyst may be removed by 
further processing which may include a simple rinsing procedure.

This invention is further described in the Examples which follow. These 
examples are intended to be illustrative of specific embodiments of this 
invention and are not intended in any way to limit the scope of the 
invention. All parts and percentages are by weight unless otherwise 
specified. 
EXAMPLES 1 & 2 
Graft Copolymer Preparation 
Example 1 
A four-neck round-bottom glass flask, fitted with a mechanical stirrer, 
thermometer, water condenser with nitrogen source, two 250 inch dropping 
funnels and nitrogen outlet, was charged with 184.3 gm of an allyl-started 
ethylene oxide/propylene oxide copolymer (40/60 by weight) having a 
viscosity of 450 SUS (Seconds, Universal Saybolt). One dropping funnel was 
charged with 64.3 gm of N-(isobutoxymethyl)-acrylamide (IBMA) and the 
other was charged with 20.3 gm of ethyl acetate and 1.3 gm of 
2,2-azobis-(2-methylpropionitrile). The flask contents were heated to 
80.degree. with an electrical heating mantle and the flask was purged with 
dry nitrogen. The IBMA and ethylacetate 2,2-azobis-(2-methylpropionitrile) 
were added simultaneously and dropwise over a period of one hour at a rate 
which kept the reaction mixture between 80.degree. and 83.degree. C. After 
addition of the IBMA and ethyl acetate/2,2-azobis (2-methylpropionitrile) 
was completed, the flask and its contents were heated to 80.degree. C. for 
three additional hours and then allowed to cool to room temperature. Any 
remaining unreacted IBMA was removed by vacuum stripping along with the 
ethyl acetate used to introduce the acid catalyst. The graft copolymer 
obtained thereby is a clear, pourable liquid that is added to water to 
make the fabric treating solution or may be applied to the fabric as a 
neat composition with the acid catalyst. 
Example 2 
A 250 ml three neck round bottom flask equipped with a stirrer was used in 
this example. To this reactor was charged 120 grams of distilled water, 
0.5 grams of sodium bicarbonate, 0.5 grams of sodium sulfite and 0.5 grams 
of sodium persulfate. After dissolution of the salts was completed by 
stirring, 15.3 grams (0.0059 moles) of the poly(oxyalkylene) polymer used 
in Example 2 were added and the resulting solution was cooled to 0.degree. 
to 5.degree. C. A 48 percent aqueous solution of N-methylolacrylamide 
containing 7.4 grams (0.034 moles) (28.6 weight percent of the total 
charge) with 5.0 grams additional water was added dropwise to the reaction 
mixture over a period of 15 minutes. After addition of all reactants was 
completed, the reaction mixture was stirred for an additional 45 minutes 
while maintaining the temperature at 0.degree. to 5.degree. C., and then 
the reaction mixture was allowed to warm to room temperature. 
This crude reaction mixture may then be diluted to form a treating solution 
upon the addition of a solvent and a suitable acid catalyst. 
Finish Application and Lubricity Testing 
The samples tested in the following examples were prepared by padding the 
aqueous finishing composition onto carded Hollofil-808, a round, hollow, 
polyester fiberfill fiber available from E. I. duPont de Nemours. The 
amount of finish taken up was controlled such that the Hollofil-808 takes 
up its own weight in aqueous finish. This 100% pick-up of finish on the 
fiberfill translated into a percent by weight of finish on the fiberfill 
equal to the percent by weight of finish in solution, i.e. a 1% graft 
copolymer finishing solution yielded a finished Hollofil-808 sample that 
is 1% by weight of graft copolymer finish. 
The finished fibers were then dried at the temperature indicated and for 
the time indicated in the following examples. 
The treated samples were then allowed to condition for three days by 
maintaining them in a constant environment of 50% relative humidity and 
70.degree. F. The samples were then tested for lubricity according to a 
"Staple Pad Friction" technique. In this technique, a weighted sled is 
pulled across a fiber sample by an Instron Model 1000 available from 
Instron Corp., Canton, Mass. The "Staple Pad Friction" is displayed in 
grams by the Instron and the Staple Pad Friction (hereinafter referred to 
as SPF) Index is computed by dividing the Staple Pad Friction in grams by 
the sled weight in grams. 
To test the durability of the graft copolymer finish, the samples as 
indicated were washed for 10 min. in a solution of 2.25 g of AATCC 
Detergent #124 held at 70.degree. C. The samples were then rinsed with 
deionized water at room temperature and were allowed to recondition in a 
constant environment as hereinbefore described. 
Example 3 
This is a control for Examples 4-6 in which untreated Hollofil-808 
exhibited an SPF of 0.40. The results of Examples 3-6 are tabulated in 
Table I. 
Example 4 
This is a comparative example in which a 1% solution of a ungrafted 
allyl-started ethylene oxide/propylene oxide (40/60 by weight) with a 
viscosity of 2700 SUS (Seconds, Universal, Saybolt) and an average 
molecular weight of 3700 g/mol was padded onto a carded Hollofil-808 
sample as hereinafter described and tested as herein before described. The 
SPF for such an ungrafted sample was 0.36 before washing. 
Example 5 
This is a comparative example wherein no catalyst was used to cure the 
graft copolymer. The procedure of Example 4 was followed with the 
exception that the graft copolymer was composed of 26.6 g by weight of 
N-(isobutoxymethyl)-acrylamide grafted onto an allyl-started ethylene 
oxide/propylene oxide (40/60 by weight) with a viscosity of 450 SUS and an 
average molecular weight of 1400 g/mol. No catalyst was, however, added to 
the finishing solution. The treated Hollofil-808 fiber exhibited an SPF of 
0.30 before washing and an SPF of 0.39 after washing. 
Example 6 
This is a preferred example wherein 7.5 g of a graft copolymer composed of 
12% by weight of polymer of N-(isobutoxymethyl)-acrylamide grafted onto 
the poly(oxyalkylene) of Example 4, 7.5 g of citric acid and 0.15 g of 
Bisphenol A were dissolved in enough deionized water to form a 750 g of 
finishing solution. Samples of Hollofil-808 were treated and tested as 
hereinbefore described to yield an SPF Index of 0.27 after curing for 10 
min. at 150.degree. C. but before washing, and an SPF of 0.29 after 
washing as hereinbefore described. 
Example 7 
This is a preferred example wherein 7.4 g of a graft copolymer composed of 
12% N-(isobutoxymethyl)-acrylamide grafted onto a glycerol-started 
ethylene oxide/propylene oxide (14/86 by weight) with a viscosity of 360 
SUS and an average molecular weight of 4741 g/mol was dispersed in 750 g 
of finishing to which was also added 0.75 g of ethoxylated nonyl-phenol, 
Tergitol NP-40 available from Union Carbide Corporation (as a surfactant 
to disperse the nearly insoluble graft copolymer), 7.5 g of citric acid 
and 0.15 g of Bisohenol A. The procedure of application and testing of 
Example 5 then yield an SPF before washing of 0.26 and an SPF after 
washing of 0.29. 
TABLE I 
______________________________________ 
SPF 
EO/PO Before After 
Example Copolymer Catalyst Washing 
Washing 
______________________________________ 
3 None None .40 .48 
4 None None .41 .44 
5 EO/PO- None .36 -- 
2700 SUS* 
6 EO/PO- None .30 .39 
450 SUS* 
26.6% IBMA 
7 EO/PO- Citric 
2700 SUS* Acid .27 .29 
12% IBMA 
8 EO/PO- Citric 
360 SUS* Acid .26 .29 
12% IBMA 
______________________________________ 
*As more fully described in the corresponding Example 
Table I illustrates that a durable fiberfill finish is obtained by the 
practice of the present invention which significantly lowers the 
interfiber friction associated with polyester fiberfill fibers.