Note: Descriptions are shown in the official language in which they were submitted.
2~38
This invention relates generally to polycaproamides
(nylon 6) and, more particularly, to a method of improving
the dyeing characteristics of shaped articles of polycapro-
amides.
It has been proposed in U.S. Patent No. 3,506,707 to
improve the affinity of acrylonitrile copolymers for cationic
dyes by the addition of an alkylamido-alkane sulfonic acid
monomer or a salt thereof to the copolymer, It has also been
proposed in sritish Patent Specification No. 995,802 to im-
prove the dyeing characteristics of polypropylene by theaddition of the sodium salt of a copolymer of alkylamido-
aklane sulfonic acid and ethylene thereto. MoreOVer, in
accordance with the disclosure in U.S. Patent No. 3,865,900
the affinity of nylon 6 for cationic dyes is improved by the
addition of an alkali metal salt of a polymer or copolymer
of 2-acrylamido-2-methylpropanesulfonic acid. However, as
described in the patent, it is necessary to minimize the
polymerization time of the nylon 6 when the alkali metal salt
of a polymer or copolymer of 2-acrylamido-2-methylpropanesul-
fonic acid is used because as polymerization time increases,the concentration of sulfonates retained through subsequent
washing and dyeing steps decreases.
It is therefore an object of this invention to provide
a method for improving the affinity of a polycaproamide for
cationic dyes which does not require minimizing the polymer-
ization time of the caprolactam. Another object of the in-
vention is to provide shaped articles of polycaproamide having
improved affinity for cationic dyes. A more specific object
of the invention is to provide polycaproamide fibers having
improved dyeing characteristics and a method for making them.
f ,si
~1~3~
According to the invention there is provided a poly-
caproamide receptive to cationic dyes containing from about 1
to about 5 percent, by weight, based on the weight of the
polycaproamide, of a salt of a vinyl ether copolymer of a 2-
acrylamido-2-methylpropanesulfonic acid with a metal of Group
Ia of the Periodic Table.
In another aspect of the invention there is provided
a method for improving the receptivlty of a polycaproamide to
cationic dyes which comprises incorporating in the polycapro-
amide from about 1 to about 5 percent, by weight, based on the
weight of the polycaproamide, of a salt of a copolymer of a
vinyl ether and 2-acrylamido-2-methylpropanesulfonic acid
with a metal of Group Ia of the Periodic Table.
In yet another aspect of the invention there is pro-
vided a process for making a polycaproamide fiber having
improved affinity for cationic dyes which comprises incorporat-
ing in the polycaproamide from about 1 to about 5 percent, by
weight, based on the weight of the polycaproamide, of a salt
of a copolymer of a vinyl ether and 2-acrylamido-2-methyl-
propanesulfonic acid and a metal of Group Ia of the Periodic
Table, and melt spinning the polycaproamide to form a fiber.
In accordance with the invention, generally speaking,
a polycaproamide (nylon 6) is provided with a sufficient amount
of a salt of a copolymer of a vinyl ether and 2-acrylamido-2-
methylpropanesulfonic acid.
In practicing the invention the copolymer salt is
suitably mixed with caprolactam and the mixture is subjected
to polymerization until a nylon 6 of the desired molecular
weight is obtained.
The nylon 6 may be prepared by any suitable poly-
merization process such as, for example, as disclosed in U.S.
Patent Nos. 2,071,250 and 2,071,253. Any suitable molecular
- la -
~2~38
weight nylon 6 may be used such as one having a molecular
weight of about 20,000 to 100,000.
It has been found that, co:ntrary to the disclosure
in U.S. Patent No. 3,865,900, caprolactam can be polymerized
while containing the copolymer provided by this invention for
the normal length of time and the copolymer will be retained
by the resulting nylon 6 almost completely through the sub-
sequent washing and drying processes. In some cases the
weight percent of the copolymer increases after the washing
and drying steps because of the loss of weight by the polymer
system when the caprolactam monomer is washed out.
The alkali metal salt of the copolymer of a vinyl
ether and 2-acrylamido-2-methylpropanesulfonic acid may be
represented by the following general formula, it being
realized that the exact properties and arrangements may
vary:
CH3 - OH- ( CH2-CH-CH2 -CH ) X-CH2 -CO-NH-C ( CH3 ) 2-CH2 - S03M
OR C=O OR
NH
CH3-C-CH3
CH2
S03M
, - i, .
i~2~38
wherein x is 150 to 1000, R is an alkyl radical and M is an
alkali metal taken from Group Ia of the Periodic Table, for
example, sodium, potassium and lithium,
The polycaproamide should contain sufficient vinyl
ether copolymer of the above formula to improve the affinity of
the polymer to cationic dyes and preferably from about 1% to
about 5% by weight based on the weight of the polycaproamide.
Any suitable alkyl vinyl ether may be used in making
the copolymer but it is preferred that the alkyl radical of the
vinyl ether contain from 4 to 20 carbon atoms. Suitably the co-
polymer will comprise from 17-47 mole percent of the vinyl ether
monomer. A conventional polymerization process can be used in
preparing the copolymer and also in preparing the nylon 6 con-
taining the copolymer provided by this invention for improving
the affinity of the nylon 6 to cationic dyes. For example, the
alkali metal salt of the copolymer may be prepared either by an
aqueous emulsion polymerization process or by solution poly-
merization. Generally speaking, in preparing the vinyl ether co-
polymer, an alkali metal hydroxide or carbonate is dissolved in
water, 2-acrylamido-2-methylpropanesulfonic acid is mixed with
the solution and the alkyl vinyl ether and a suitable initiator
are mixed therewith. The mixture is then heated, water is removed
and the polymer is recovered by trituration in an alcohol.
Alternately, the copolymer may be prepared by mixing potassium
carbonate with water and dimethylformamide and then with 2-acryl-
amido-2-methyl-propanesulfonic acid. The resulting mixture is
then heated with an alkyl vinyl ether and an initiator and
stirred while heating to a temperature of about 60C. until a
polymer is obtained. Any suitable free radical initiator such
as an organic peroxide can be used. The polymer is recovered by
filtration and washing with hexane and drying in vacuo.
- 3 -
In the following exampleS all parts are by weight unless
otherwise specified. In these examples and the following tables,
"AMPS" is used to identify 2-acrylamido-2-methylpropanesulfonic
acid and "KAMPS" is used to identify the potassium salt thereof.
Example 1 - Preparation of Isobutyl Vinyl Ether Copolymer via
Aqueous Emulsion
About 17 grams potassium carbonate were dissolved in about
122.5 ml distilled water. This solution was chilled and 51.75 g
AMPS was slowly added to the stirred solution. This solution was
stirred for approximately 15 min. at room temperature. The pH was
adjusted to 7.5 with additional K2CO3. The pH corrected solution
was decolorized with charcoal and the charcoal was removed by
filtration through Celite. The filter bed was washed with an ad-
ditional 40 ml of distilled water.
The combined filtrate and washings were transferred to a 1
liter 3 neck round bottom flask equipped with a reflux condenser,
N2 bubbler, and external stirrer. About 25 g. i_butyl vinyl ether,
(g) (g)
0.3 ml Tween 20 and 0.3 g of Span 60 were added with stirring.
Nitrogen purging was begun and after 45 min., the temperature
was raised to 55-60C.
After 60 min. purging, about 20 ml of 2-propanol and 405
mg of azo-bis-isobutyronitrile (AIBN) initiator were introduced
into the polymerization vessel. The temperature was increased
to 70C. After 2 hours of stirring, about 405 mg of potassium
persulfate were added. The polymerization was continued for an
additional 4 hrs. at 70C. The mixture was allowed to stand
at room temperature overnight. The 2-propanol and most of
the water were removed under reduced pressure. The polymer was
recovered by trituration of the viscous residue into methanol.
The viscosity (Brookfield) of a 10% aqueous solution of the
dried polymer was 55 centipoise at 25C.
Example 2 - Preparation of Isobutyl Vinyl Ether Copolymer via
a Solution Polymerization
About 18.5 g of potassium carbonate were suspended in a
chilled mixture of about 25 ml of distilled water and about 50
ml of dimethylformamide (DMF). About 51.75 g AMPS was slowly
added, with vigorous stirring, to this chilled suspension. Ad-
ditional DMF, about 275 ml, was added to this mixture, followed
by the addition of approximately 1 g of decolorizing charcoal.
The mixture was heated to 50-55C. for 20 mins. The charcoal
was removed by filtration through Celite. The DMF solution of
KAMPS was transferred to a vented addition funnel which led
into the polymerization apparatus described in Example 1. The
KAMPS solution in the addition funnel was purged with N2 for
about 30 mins. Approximately one-half of this solution was
dropped into the polymerization vessel containing about 25 g
of isobutyl vinyl ether. This stirred mixture was purged for
approximately 15 mins. while heating to 55-60C. The polymeri-
zation was then initiated by addition of 200 mg of AIBN. After 1
hour, one-half of the remaining KAMPS solution was added from the
addition funnel, the last portion of the KAMPS solution was added
after an additional 75 mins. A last charge of AIBN (100 mg) was
added 5.5 hrs. after the initial AIBN addition. The polymerization
was continued overnight at 55-60C.
The product from this polymerization was recovered by fil-
tration and washing with hexane and drying in vacuo. If the pro-
duct of the solution polymerization is not solid, treatment with
methanol converts it to a product that is handled with no dif-
ficulty. Alternatively, the whole of the DMF polymer suspension
can be triturated into methanol in a Waring blender. The viscosity
(Brookfield) of a 10% aqueous solution of this polymer is 17.5
centipoise at 25C.
2~38
Example 3 - Preparation of a Nylon 6 Polymer Containing a
Copolymer of n-Butyl Vinyl Ether: KAMPS Copolymer
A solution of 7.5 g of a copolymex of potassium AMPS (potas-
sium 2-acrylamido-2-methylpropane sulfonate): n-butyl vinyl ether
was prepared using 15 ml of distilled water to dissolve the
copolymer. The copolymer contained 10.2% potassium and was pre-
pared as in Example 2. The copolymer solution was added to a
mixture of 300 g of caprolactamr 0.240 g of benzoic acid (molecular
weight regulator), and 0.015 g of manganese acetate (light stabi-
lizer) in a l-liter glass reactor equipped with an agitator and
distilling head. The mixture was maintained under a flow of
~ .
dry nitrogen and heated to 265C. by means of a Dowthern A boiler.
The mixture was stirred at 100 rpm for 4 hours to assist in re-
moval of water and to disperse the copolymer in the mixture; the
stirring was then continued at 30 rpm for an additional 18 hours.
The resulting light yellow homogeneous polymer was extruded
as a monofilament into a water bath. The polymer mass was ground
and boiled with 5 changes of dis'illed water to remove low molecu-
lar weight material. The purified polymer was dried in vacuo at
75C. for 24 hours; the polymer had a relative viscosity of 2.10,
an amine end group concentration of 4.8 meg/113 g, and a carboxylic
acid end group concentration of 5.3 meg/113 g.
The nylon polymer prepared above was melt spun in normal
fashion to yield a 6 filament-30 denier yarn. A yarn potassium
concentration of 0.345% indicated quantitative retention of the
n-butyl vinyl ether: KAMPS copolymer through the rather severe
polymerization and washing process.
A 2-ply yarn was made and knit into tubes which were dyed
with red (Sevron Red GL), yellow (Basacryl Yellow RL), or blue
(Genacryl Blue RGL) cationic dyes or a blue (Duranol Blue G) dis-
perse dye. The dye fastness properties of the sample yarn on
11~2~38
washing or exposure to ozone were equal to those exhibited by
the control yarn; lightfastness of the cationic dyes was
slightly better with the sample yarn than with the control yarn.
Example 4 - Preparation of a Nylon 6 Polymer Containing A
Copolymer of Isobutyl Vinyl Ether: KAMPS Copolymer
An aqueous solution of 12 ml of distilled water and 7.5 g
of an isobutyl vinyl ether copolymer (prepared as in Example 1)
was incorporated in a nylon 6 polymer as described in Example 3.
The resulting polymer had a relative viscosity of 2.07, an amine
10 end group concentration of 6.8 meg/113 g, and a carboxylic end
group concentration of 5.5 meg/113 g. The potassium concentration
in the polymer increased from 0.30~ before washing to 0.33% after
washing of the ground nylon 6 preparation. The polymer was melt
spun in a conventional manner and demonstrated the same dye pro-
perties as in Example 3.
Example 5
Example 4 was repeated and the sulfur content of the nylon
6 containing the isobutyl vinyl ether: KAMPS copolymer, as determined
by either microcoulometric or x-ray fluorescence methods, increased
20 from 0.29% to 0.32% upon washing.
Example 6
Example 3 was repeated and the nylon 6 containing a n-butyl
vinyl ether: KAMPS copolymer showed an increase in sulfur content
from 0.325% to 0.375~ upon washing.
The properties of the prior art polymers are tabulated
in Table I while those of the copolymers of the invention are
shown in Table II.
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The polymers of Table I had the following compositions:
I. Nylon 6 containing the lithium salt of AMPS prepared
in accordance with Example 1 of U.S. Patent No. 3,865,900.
II. Nylon 6 containing the sodium salt of AMPS prepared
in accordance with Example 2 of U.S. Patent No. 3,865,900.
III. Nylon 6 containing the lithium salt of AMPS prepared
in accordance with Example 3 of U.S. Patent No. 3,865,900.
IV. Nylon 6 containing a potassium salt of AMPS.
V. Nylon 6 containing a lithium salt of AMPS.
VI. Nylon 6 containing a potassium salt of a copolymer
of AMPS and N-vinylpyrrolidone.
VII. Nylon 6 containing a potassium salt of a copolymer
of AMPS and a-methyl styrene.
VIII. Nylon 6 containing a potassium salt of a copolymer
of AMPS and a-methyl styrene.
IX. Nylon 6 containing a potassium salt of a copolymer of
AMPS and a-methyl styrene.
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The polymers of Table II had the compositions:
X. Nylon 6 containing a copolymer of AMPS and isobutyl
vinyl ether of Example 4.
XI. Nylon 6 containing a copolymer of AMPS and isobutyl
vinyl ether of Example 4.
XII. Nylon 6 containing a copolymer of AMPS and the iso-
butyl vinyl ether of Example 4.
XIII. Nylon 6 containing a copolymer of AMPS and n-butyl
vinyl ether.
XIV. Nylon 6 containing a copolymer of AMPS and isobutyl
vinyl ether.
The mole percents of vinyl ether in each of the co-
polymers of Table II has been calculated from the % Metal data
in Table II and are tabulated in Table IIa.
TABLE IIa
Polymer No. M% %K Mole %
Vinyl Ether
. . :
X .35 14.35 17 -
XI .30 12.3 40
XII .28 11.48 47
XIII Not deter-
mined
XIV .30 12.3 40
The physical properties of 30/6 yarns spun from nylon
6 containing metal salts of AMPS and from the metal salts of co-
polymers provided by this invention àre recorded in TABLE III
together with those of control yarn spun at the same time. The
control yarn contained lithium 5-sulfoisophthalate, a com-
mercially used cationic additive.
-- 1 1
2~38
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-15-
2~
It is apparent from a comparison of the percentages
of metal in nylon 6 containing the metal salt of a vinyl ether-
AMPS copolymer with that of nylon 6 containing KAMPS or a metal
salt of an A~PS copolymer disclosed in U.S. Patent No. 3,865,900
before and after washing of the nylon 6 compositions that the
copolymer of this invention is retained in a larger percentage
after washing than those of the prior art. Also, the invention
provides the further advantage that polymerization of the capro-
lactam can be conducted in accordance with conventional polymeri-
zation processes without reduction in sulfur retention.
Although the invention is described in detail for the
purpose of illustration, it is to be understood that such detail
is solely for that purpose and that variations can be made therein
by those skilled in the art without departing from the spirit and
scope of the invention except as it may be limited by the claims.
-16-
