Ozone resistant, cationic dyeable nylon containing lithium, magnesium or calcium salts of sulfonated polystyrene

This invention discloses the improved method of making nylon cationic dyeable whereby the soluble lithium, magnesium or calcium salt of a sulfonated polystyrene is added, to provide improved lightfastness and ozone resistance over conventional cationic dyeable nylon.

BACKGROUND OF THE INVENTION 
This invention relates to synthetic fiberforming polyamides, and shaped 
articles therefrom, which have excellent affinity for basic or cationic 
dyestuffs. 
It is an object of this invention to provide a new and useful polyamide. 
These polyamides are useful as shaped articles, particularly fibers which 
can be made into a textile fabric such as carpet. Another object is to 
provide a shaped article which has increased affinity to cationic dyes. 
Ozone fading of cationic dyed polyamide yarn in carpet has become a serious 
problem to the industry. Another object is to provide a cationic dyed 
polyamide which has increased resistance to ozone fading, improved wash 
fastness and increased dyed lightfastness. 
The salts of this invention are soluble in water, in contrast to the 
water-insoluble salts which are described as preferred in U.S. Pat. No. 
3,665,054. The polysulfonic acids described in that patent have a lower 
degree of sulfonation, less than 50 percent, compared to the polysulfonic 
acid described here which is at least 90 percent sulfonated. 
The salts of polystyrene sulfonic acid in which the styrene is sulfonated 
to a high degree have been reported to be insoluble in nylon. This 
insolubility is described in U.S. Pat. No. 3,553,286, which states that a 
vinyl polymer having pendant sulfonic acid groups in which the whole of 
the sulfonic acid group is present in the form of an alkali metal (Li, Na, 
or K) or calcium salt has bad compatibility with polyamide. We have 
confirmed that the sodium salt and the potassium salt do indeed have poor 
compatibility with nylon 6. This is shown below by Examples 1, 2, 3 and 4. 
Also, in certain competitive dyeing situations, the cationic dyeable 
polymer yarn containing highly sulfonated polystyrene will pick up an 
undesired anionic dye. This undesirable pick-up is called cross staining. 
SUMMARY OF THE INVENTION 
We have found, to our surprise, that the lithium, magnesium, and calcium 
salts, or their mixtures, of polystyrenesulfonic acid in which the benzene 
rings are predominantly sulfonated, are water soluble, compatible with 
nylon 6, and yet largely retained by the nylon despite aqueous treatments 
such as leaching the polymer pellets, and dyeing the yarn. 
Also, to our surprise, the nylon 6 yarn made of the polymer containing the 
additives of the method of this invention has greatly improved resistance 
to fading due to ozone in the atmosphere. 
The invention is a method to provide a polyamide article which contains a 
small amount of the lithium, magnesium, or calcium salt of a 
polystyrenesulfonic acid. The preferred salt is that of lithium because of 
increased yarn brilliance compared to the magnesium or calcium salts. 
The preferred molecular weight for the salt of polystyrenesulfonic acid is 
from about 15,000 or, preferably, about 30,000 to about 300,000. The lower 
limit is fixed by the requirement for it to be retained by the nylon 
through the wet processing. The upper limit is proposed because the salt 
is most conveniently handled as an aqueous solution, and a very high 
molecular weight polymer gives a solution which is quite viscous at 
economical concentrations. 
The pH of the polystyrenesulfonic acid salt in a 30 percent aqueous 
solution must be adjusted to between 3 and 8. At lower pH's the acid 
decomposes at temperatures above 100.degree. C. At higher pH's the color 
of the salt solution becomes green, and any polymer made with this 
solution is off color. Use of the acid, such as claimed in U.S. Pat. No. 
3,665,054, is not workable due to this discoloration and slow 
polymerization. 
The polystyrenesulfonic acid salt is preferably added to the polyamide 
precursor as an aqueous solution, although a dry salt can be used, and 
then this mixture together with light stabilizers such as manganese salts, 
polymer molecular weight regulators such as acetic acid, sebacic acid, 
azelaic acid, or 5-sulfoisophthalic acid, and delustrants, if desired, is 
subjected to polymerization conditions. The order of addition is not 
important, that is, the polystyrenesulfonic acid could be first added to 
the polyamide precursor, then the lithium, magnesium and/or calcium ion 
can be added in the form of, for example, their oxides, hydroxides and/or 
carbonates, to form the salt of the polystyrenesulfonic acid. The 
preferred concentration of sulfonates present is between 50 and 150 
equivalents per 10.sup.6 grams, but up to about 600 equivalents can be 
used in a master batch. 
The molecular weight regulator can also be any carboxylic acid or ester 
bearing an aromatic sulfonic or polysulfonic acid or alkaline metal salt 
thereof such as 
sulfonated 2-benzoylbenzoic acid, 
sulfonated 2-bibenzylcarboxyl acid, 
sulfonated phenylacetic acid, 
sulfonated o-phenoxybenzoic acid, 
sulfonated phenoxyacetic acid, 
sulfonated benzoic acid, or 
sulfonated 4-benzylbenzoic acid 
and the alkaline metal salts of them. More specifically, the molecular 
weight regulator can be a compound of the structure 
##STR1## 
wherein X is Li, Na, K or NH.sub.4, Y is H or 
##STR2## 
The carboxyl groups are not ortho to one another, and R is OH, Cl, 
OCH.sub.3 or OC.sub.2 H.sub.5. 
When the sulfonated styrene salt is combined with a molecular weight 
regulator, the most preferred range of concentration in the polymer is 
from about 40 to about 80 equivalents per 10.sup.6 grams of polymer as 
shown in the final examples, Tables I and II. However, still preferred is 
a range of from about 20 to about 100 equivalents per 10.sup.6 grams of 
polymer to achieve a polymer with highly improved cross staining yet 
superior ozone resistance. The total sulfonates would still remain between 
40 and 180 equivalents per 10.sup.6 grams polymer in these combinations of 
salt and regulator. 
The polymerization is done under conditions normally employed for producing 
polyamides. Polymerization can be initiated by steam under pressure as in 
the case of nylon 6. The met is then held under atmospheric pressure until 
it reaches the desired degree of polymerization. The polymer is either 
subjected to high vacuum to remove unreacted monomer, or extruded as 
strands which are pelletized and water-extracted to remove unreacted 
monomer. 
As an alternative to addition of the salt to the polymer precursor, an 
aqueous solution of the salt can be coated on polymer chips and the water 
taken off by evaporation. The polymer with the polystyrene-sulfonic acid 
salt can be shaped into an article or spun into fibers by spinnerettes 
containing the normal filtering sand packs or sintered metal. The pressure 
drop through the spinnerette was no greater than the control yarn without 
any additive. 
The undrawn yarn when wound gives bobbins or other carriers having 
excellent package formation. That is, the bobbins or spools are wound 
uniformly with no tendency to slough off yarn. 
The drawn yarn has an excellent affinity for cationic dyes. The uptake for 
some cationic dyes, for example, "Sevron Yellow 8-GMF", 
##STR3## 
where A is an anion, is proportional to the equivalents of sulfonate in 
the yarn. Other cationic dyes, for example, Astrazon Blue 3-RL, identified 
in U.S. Pat. No. 3,794,464, are essentially exhausted from the dye bath, 
and are not affected by the number of sulfonate equivalents within a range 
of 30 to 180-gram equivalents of sulfonate per 10.sup.6 grams of polymer. 
The uptake of disperse dyes is not materially affected by the amount of 
sulfonate in the yarn. Uptake of acid dyes can be inhibited by the use of 
a monocarboxylic acid or dicarboxylic acid as a molecular weight regulator 
which also decreases the concentration of amine ends, preferably to 
15-25-gram equivalents per 10.sup.6 grams. 
The dyed yarn made using these salts of polystyrenesulfonic acid also has 
excellent resistance to ozone fading compared to the cationic dyeable 
polymer made with 5-sulfoisophthalic acid. 
The sulfonated polystyrene can be prepared according to U.S. Pat. No. 
3,072,618. 
This invention is an improvement on the prior art method to make a 
fiber-forming synthetic linear polyamide having a repeating structure of 
##STR4## 
where R and R' are radicals of 3 to 13 carbon atoms receptive to cationic 
dyes by the addition of a sulfonated polystyrene or salt thereof. These 
prior art polyamides have from about 10 to about 60 amine gram-equivalents 
per 10.sup.6 grams of polymer and a ratio of less than 10 sulfonate 
gram-equivalents per amine gram-equivalent. The improvement is adding to 
the polyamide a water-soluble salt of a highly sulfonated polystyrene 
selected from the group consisting of lithium, magnesium and calcium 
salts. A 30 percent aqueous solution of the salt should have a pH of 
between about 3 and about 8. Then the shaped article is made such as by 
spinning to fiber. The salt should preferably be sulfonated to over 90 
percent of the theoretical maximum of complete monosulfonation of of each 
styrene residue moiety. The salts of this invention can also be added to 
the polyamide precursors prior to polymerization, then the precursors are 
polymerized and the polymer is shaped by such methods as spinning to a 
fiber. The cationic-dyed polyamide fibers of this invention have highly 
improved resistance to fading of the cationic dye due to exposure to 
ozone. The method of testing for ozone fading is similar to the AATCC Test 
129-1968 set forth on page 334/15 of The Journal of American Association 
of Textile Chemists and Colorists, July 30, 1969, Volume 1, No. 16, in an 
article entitled, "A New Test Method for Ozone Fading at High Humidity", 
by Victor S. Salvin. 
The method and the means of measuring the loss of dye consists in dyeing 
the yarn with a selected dye or dyes, exposing it to ozone at a 
concentration of 20 parts per hundred million in a test chamber together 
with a control nylon sample which was dyed an avocado shade. The control 
sample is examined periodically until the resulting color corresponds to 
that of the Standard of Fading (one cycle). It has been found that one 
cycle is completed when the internal standard has faded sufficiently to 
give a .DELTA.E of 2.8, compared to the unexposed standard. 
.DELTA.E is a measure of the change of color between two samples, a smaller 
.DELTA.E being a closer match, or less fading of one sample compared to 
the second sample. 
This color difference, .DELTA.E, was measured with a Hunterlab Color 
Difference Meter. This instrument measures color as seen in average 
daylight in a manner similar to the way in which the human eye responds to 
the stimulus of color. Experimentation has shown that the eye can match 
any color with a combination of three "primary" colored lights, and, 
therefore, that any color can be specified by a three-dimensional 
identification. The Color Difference Meter measures the light reflected by 
a specimen through filters that correspond to the three "primary" lights. 
These measurements made correspond to the way the average human eye 
responds to light. 
EQU .DELTA.E = .sqroot. (.DELTA.L).sup.2 + (.DELTA.a).sup.2 + (.DELTA.b).sup.2 
where 
EQU .DELTA.L is L.sub.1 - L.sub.2 
EQU .DELTA.a is a.sub.1 - a.sub.2 
EQU .DELTA.b is b.sub.1 - b.sub.2 
and L, a, and b are readings on the Hunterlab Color Difference Meter. "L" 
is a 100 to 0 reading of white to black; "a" indicates redness when 
positive, gray when zero, and green when negative; "b" indicates yellow 
when positive, gray when zero, and blue when negative. 
The yarns containing the salts of polystyrene sulfonic acid of this 
invention also have improved dye wash fastness, and dye light fastness, 
compared to cationically dyeable nylon made with salts of 
5-sulfoisophthalic acid.

These advantages of the subject invention and the methods of practicing the 
invention are shown in the following examples. The pH of the salts used in 
the examples was about 6 on a 30 percent aqueous solution, if not given. 
DESCRIPTION OF PREFERRED EMBODIMENTS AND COMATIVE EXAMPLES 
EXAMPLE 1 (Comparative) 
29.5 Grams of the sodium salt of sulfonated polystyrene was dissolved in 
100 grams of water. The molecular weight of the polymeric salt is about 
70,000. (This material is available commercially from National Starch and 
Chemical as Versa TL-70.) The pH of a 30 percent aqueous solution varies 
from 5.5 to 7.5. This aqueous solution was added to 1520 grams of 
caprolactam. 6.8 Grams of sebacic acid was added as a molecular weight 
regulator. The solution was homogeneous. Then 80 grams of 
epsilon-aminocaproic acid was added as a polymerization initiator, and the 
mixture was poured into a 3-liter agitated glass reactor equipped with a 
heating mantle. The mixture was heated over a period of about 1.5 hours 
under a nitrogen blanket (50 cc. of nitrogen gas per minute) to 
255.degree. C. As the water flashed off the polymerization mixture, the 
sodium salt of polystyrenesulfonic acid separated from the lactam. At the 
end of 12 hours, a polymer ribbon was extruded from the bottom of the 
reactor which was pale yellow and full of white lumps. Unreacted 
caprolactam was removed by water extraction and dried. The washed and 
dried polymer was submitted for analysis. The formic acid relative 
viscosity was 69, with 65 equivalents of carboxyl and 20 equivalents of 
amine per 10.sup.6 grams. Sulfur analysis by X-ray fluorescence showed 
1740 parts per million sulfur, or about 54 equivalents of sulfur per 
10.sup.6 grams. Spinning of this polymer into fiber was precluded by the 
large amounts of insoluble "unspinnable chunks" in the polymer even after 
washing. 
EXAMPLE 2 (COMATIVE) 
20 Grams of the same sodium salt of polystyrene sulfonic acid was dissolved 
in 100 grams of water and this solution was poured over 1000 grams of a 
nylon 6 polymer of about 70 formic acid relative viscosity. The mixture 
was tumble-dried under vacuum to coat the nylon 6 pellets with the salt. 
The dried polymer was submitted for spinning. It was fed into a 1-inch 
diameter extruder, which delivered molten polymer to a metering pump, and 
then to a filtering sand pack. The extruder, pump, and sand pack were 
heated to about 270.degree. C. and the polymer fed into the extruder. 
After about 5 minutes, the pressure drop across the sand pack was so great 
that the support for the sand pack broke, sending fine sand and dark brown 
polymer through the spinnerette holes. A repeat with a reduced sand pack 
had the same result. The polymer without any coating had spun well, 
without discoloration immediately prior to the first mentioned spinning 
attempt, with the full sand pack. 
EXAMPLE 3 (COMATIVE) 
15 Grams of the sodium salt of polystyrenesulfonic acid of about 500,000 
molecular weight was dry blended with 1000 grams of a nylon 6 polymer of 
about 70 relative viscosity in formic acid, 70 carboxyl equivalents, and 
16 amino equivalents per 10.sup.6 grams of polymer. This polymer was fed 
into the same spinning system as described in Example 2. As in Example 2, 
the pressure drop through the sand rose rapidly and the sand pack broke. 
After the sand pack broke, sand and black polymer came through the 
spinnerette holes. 
A similar polymer, but without the polystyrene sulfonate, had been spun 
immediately preceding the above blend without excessive pressure drop or 
polymer discoloration. 
EXAMPLE 4 (COMATIVE) 
68.5 Grams of a 30 percent solution of sulfonated polystyrene of about 
70,000 molecular weight was neutralized by the addition of 8.22 grams of 
potassium hydroxide. (This polystyrene sulfonic acid is available from 
National Starch and Chemical as Versa TL-71). 
This aqueous solution was added to 1520 grams of caprolactam. 6.0 Grams of 
sebacic acid was added as a molecular weight regulator. The solution was 
homogeneous. The solution, together with 80 grams of epsilon-aminocaproic 
acid was poured into an agitated reactor and subjected to polymerization 
conditions as described in Example 1. As in Example 1, when the water was 
boiled off the potassium salt of polystyrenesulfonic acid separated as 
white lumps in the molten polymer, confirming the contention in U.S. Pat. 
No. 3,553,286 that the potassium salt has bad compatibility with 
polyamide. 
When the polystyrenesulfonic acid was neutralized with zinc carbonate or 
gelatinous aluminum hydroxide, the same incompatibility was observed. 
EXAMPLE 5 
A solution of the lithium salt of polystyrenesulfonic acid was prepared by 
dissolving 3.46 grams of lithium carbonate in 57.5 grams of a 30 percent 
aqueous solution of a 70,000 molecular weight polystyrenesulfonic acid 
which also contained 0.1 gram of Dow Corning Antifoam 35 to reduce 
foaming. This entire solution was added to 1520 grams of caprolactam at 
90.degree. C. Manganese chloride (0.0576 gram) and 0.1640 gram of a 50 
percent aqueous solution of hypophosphorus acid were added to serve as 
light stabilizers. The solution was homogeneous. 
This solution was poured into a 3-liter agitated glass reactor equipped 
with a heating mantle, and a gas inlet and outlet to provide a nitrogen 
blanket over the molten mixture. 80 Grams of epsilon-aminocaproic acid was 
added as a polymerization initiator. The mixture was then heated over a 
period of about 1.5 hours to about 255.degree. C. When the water flashed 
off, there was no phase separation. 
At the end of 4.75 hours a polymer ribbon was extruded from the bottom of 
the reactor which was a pale yellow, without lumps, and of constant cross 
section. Unreacted caprolactam, about 10 percent by weight, was removed by 
water extraction. The washed and dried polymer was submitted for analysis. 
The formic acid relative viscosity was 65, with 72 equivalents of carboxyl 
and 31 equivalents of amine per 10.sup.6 grams of polymer. Sulfur analysis 
by X-ray fluorescence of the washed and dried polymer showed 2150 parts 
per million sulfur, or about 67 equivalents of sulfur per 10.sup.6 grams 
of polymer. A sample of the unwashed polymer contained about 2400 parts 
per million sulfur. The theoretical concentration of sulfur, based on the 
amount of polystyrenesulfonic acid salt added, was 2240 parts per million. 
The polymer was submitted for spinning. It was spun using the same spinning 
equipment as described in Example 2. The spinnerette had 14 holes each in 
the shape of a "Y" to get a yarn with a "Y" cross section. The spinning 
temperature was about 275.degree. C. Pressure drop across the sand pack in 
the spin pot was about 5900 psi. 
The undrawn yarn had a total denier of 705 or an average of 50 denier per 
filament. The free fall yarn had a formic acid relative viscosity of 54, 
with 71 carboxyl equivalents and 24 amine equivalents per 10.sup.6 grams 
of polymer. Five ends of this yarn were gathered and drawn to 3.2 times 
the spun length, and then 2-plied to give a yarn of 2260 total denier. 
This yarn had a tensile strength of 3.1 grams per denier and an ultimate 
elongation of 45 percent. A control yarn (pure nylon 6) spun at the same 
time had a tensile strength of 3.3 grams per denier and an ultimate 
elongation of 53 percent. 
A control yarn was made from a nylon 6 polymer having a formic acid 
relative viscosity of 46, about 90 carboxyl equivalents per 10.sup.6 
grams, about 25 amine equivalents with about 81 sulfonate group 
equivalents, from the sodium salt of sodium 5-sulfoisophthalate. It was 
spun on the same spinning equipment as described above, drawn, knitted 
into sleeves, and autoclaved at 270.degree. F., that is, heat set. 
Autoclaving consisted of putting the knitted sleeves into an autoclave, 
evacuating the chamber to 27 inches of vacuum and introducing steam to 
heat the chamber to 230.degree. F. The chamber is held at 230.degree. F. 
for 5 minutes, and the pressure released. The chamber is then 
repressurized with steam to heat to 230.degree. F. The pressure is held 
for 5 minutes and released. Then steam is introduced and the temperature 
is allowed to rise to 270.degree. F. The pressure is released and then 
steam is put in again until the temperature is 270.degree. F. It is held 
for 5 minutes and again the pressure released. Then it is repressurized to 
give a temperature of 270.degree. F. for 8 minutes. The pressure is then 
released and the yarns removed from the autoclave. 
The yarns were dyed in separate dye baths to a moss green shade in a dye 
bath composed as follows: 
0.3% (OWF) Sevron Yellow 8-GMF (duPont) 
0.25% (OWF) Sevron Blue GCN (duPont), C. I. Basic Blue 97 
2.0% (OWF) Hipochem PND-11 (amine salt of an alcohol ester) 
1.0% (OWF) Hipochem CDL-60 (nonionic surfactant) 
and monosodium and/or disodium phosphate to adjust the pH of the dye bath 
to 7.0 .+-. 0.2. OWF means on the weight of the fiber. 
The dyed sleeves were then exposed for 6, 12, and 18 hours in an atmosphere 
of about 20 parts per hundred million of ozone, at a temperature of 
104.degree. F., at a relative humidity of 95-100 percent. 
The results of ozone exposure are listed below: 
______________________________________ 
.DELTA.E 
6 12 18 
Hours Hours Hours 
______________________________________ 
(a) Control - polymer with 
6.2 10.2 14.2 
5-sulfoisophthalate 
(b) Polymer with lithium 
0.8 2.2 2.5 
salt of polystyrene 
sulfonic acid 
______________________________________ 
The undyed sleeves described above were also dyed in a second set of dye 
baths where 0.25 percent of Astrazon Blue 5-GL, C. I. Basic Blue 45 was 
substituted for 0.25 percent of Sevron Blue GCN, C. I. Basic Blue 97 which 
has the formula 
##STR5## 
These dyed sleeves were also exposed to 6, 12, and 18 hours in the above 
ozone chamber. The results of ozone exposure were: 
______________________________________ 
.DELTA.E 
6 12 18 
Hours Hours Hours 
______________________________________ 
(a) Control - Polymer with 
6.3 12.1 16.6 
5-sulfoisophthalate 
(b) Polymer with the 1.6 3.5 4.8 
lithium salt of poly- 
styrenesulfonic acid 
______________________________________ 
Exposure of a third set of dyed yarns where Astrazon Blue 3RL (C. I. Basic 
Blue 47) was substituted for Astrazon Blue 5GL gave .DELTA.E's generally 
around 3 to 4 after 18 hours. 
The yarn with the lithium salt of polystyrenesulfonic acid, and the yarn 
with 5-sulfoisophthalic acid sodium salt were also dyed with 0.5 percent 
(OWF) Astrazon Blue 5GL and exposed to xenon light in an Atlas 
Weatherometer for 60 hours. The former yarn took 40 hours to get a color 
"break", while the latter broke in only 20 hours. By "break" or "broke" is 
meant a noticeable change in color or shade of the sample exposed compared 
to an adjacent unexposed portion. 
EXAMPLE 6 
38 Grams of a neutral dry mixture of lithium carbonate and a 
polystyrenesulfonic acid of about 70,000 molecular weight, which also 
contained about 10 percent sulfuric acid, was dissolved in 100 grams of 
water. This was added to 1520 grams of caprolactam at 90.degree. C. 0.0576 
Gram of manganous chloride and 0.1640 grams of a 50 percent aqueous 
solution of hypophosphorous acid and 8.0 grams of sebacic acid were added, 
and the clear, homogeneous solution was poured into a 3-liter agitated 
reactor. 80 Grams of epsilon-aminocaproic acid was added and the material 
was subjected to polymerization conditions as in Example 5. 
After 9.5 hours of polymerization, the polymer was leached and dried. 
Analysis of the polymer gave a formic acid relative viscosity of 38.6, 
with 93 carboxyl equivalents and 25 amine equivalents per 10.sup.6 grams 
of polymer. The sulfur analysis showed 2960 parts of sulfur per million 
parts polymer, i.e., 92.5 equivalents of sulfonate groups per 10.sup.6 
grams of polymer. 
The polymer was spun in the same manner as was the polymer of Example 5. 
The spin pot temperature was 255.degree. C., pressure drop across the 
filter in the spin pot was 2300 psi. The undrawn yarn, total denier 712, 
was taken up at a speed of 990 feet per minute. The free fall yarn had a 
formic acid relative viscosity of 36, with 3000 parts of sulfur per 
million parts of polymer. Five ends of the undrawn yarn were gathered and 
drawn to about 3.2 times the spun length, and then 2-plied to give a yarn 
of 2270 total denier. This yarn had an ultimate elongation of 46 percent, 
and a breaking strength of 2.5 grams per denier. 
A control yarn made from the same type of polymer as the control yarn of 
Example 5 was spun immediately preceding the above yarn. The yarn takeup 
speed was 965 feet per minute to give an undrawn yarn of 720 denier. 
Pressure drop across the spin pot was 1700 psi. The undrawn yarn was 
gathered, drawn and 2-plied as above to give a yarn of 2300 total denier. 
This control yarn had an ultimate elongation of 48 percent, and a breaking 
strength of 30 grams per denier. 
These yarns were knitted into sleeves, autoclaved at 270.degree. F. as 
detailed in Example 5, and dyed in separate dye baths, each containing 0.2 
percent Sevron Blue GCN (OWF). The dye pickup was similar, but the yarn 
containing the lithium salt of polystyrenesulfonic acid exhausted the dye 
bath, while the control yarn left some blue dye in solution. 
Sections of both sleeves were also dyed to a moss green shade in a dye bath 
made up as the first mentioned bath of Example 5, i.e., containing 0.25 
percent Sevron Blue GCN, etc. They were then submitted for exposure to 20 
parts per hundred million of ozone for three cycles. 
The results of ozone exposure were: 
______________________________________ 
.DELTA.E 
______________________________________ 
(a) Control yarn -containing 81 equi- 
16.4 
valents of sulfonate from 5-sulfoiso- 
phthalic sodium salt 
(b) Polymer with the lithium salt of 
3.0 
polystyrenesulfonic acid 
______________________________________ 
EXAMPLE 7 
1800 Grams of a 30 percent solution of polystyrenesulfonic acid was 
neutralized with a 5 normal solution of lithium hydroxide. The 
polystyrenesulfonic acid had a molecular weight of about 70,000. 
300 Grams of the above solution was added to 1520 grams of caprolactam at 
90.degree. C., containing 0.0576 gram of manganous chloride and 0.1640 
gram of a 50 percent solution of hypophosphorous acid to give a clear, 
colorless solution. This solution was poured into a 3-liter agitated 
reactor. 80 Grams of epsilonaminocaproic acid and 6.0 grams of sebacic 
acid were added, and the mixture was subjected to polymerization 
conditions similar to those of Example 5. 
At the end of 8.75 hours a polymer strand was taken from the bottom of the 
reactor. The strand was pelletized, washed to remove lactam, and dried. 
The resulting polymer had a relative formic acid viscosity of 38, with 84 
carboxyl equivalents and 28 amine equivalents per 10.sup.6 grams of 
polymer. Sulfur analysis by X-ray fluorescence showed 5700 parts per 
million sulfur. 
The polymer was spun in a manner similar to that described in Example 5. 
Spinning temperature was 280.degree. C. Pressure drop across the spin pot 
filter was 1700 psi. The undrawn denier was 727. After gathering five ends 
together, drawing, and 2-plying, the resulting yarn had a total denier of 
2350. The relative formic acid viscosity was 43, and the sulfur content 
was analyzed to be 5510 parts per million. The yarn had an ultimate 
elongation of 37 percent, and tensile strength of 2.7 grams per denier. 
The yarn was knitted into sleeves, autoclaved at 280.degree. F., as in 
Example 5, and dyed to a moss green shade in a dye bath which formulation 
was identical to the first mentioned dye bath in Example 5. 
The dyed sleeve together with a control sleeve similar to that of Example 
5, which had been dyed in a dye bath containing the same formulations were 
then exposed to ozone. Ozone concentration was 20 parts per hundred 
million. 
The results of exposure for 6, 12, and 18 hours are as follows: 
______________________________________ 
.DELTA.E 
6 Hours 12 Hours 18 Hours 
______________________________________ 
(a) Control 7.5 12.0 15.2 
(b) Yarn with lithium 
0.2 0.5 1.5 
polystyrenesulfonate 
______________________________________ 
The same yarns were dyed with 0.5 percent Astrazon Blue 5-GL and exposed to 
xenon light for 10-60 hours. The control yarn took 20 hours to develop a 
color break; the yarn of this invention took 40 hours to break. 
EXAMPLE 8 
A nylon polymerization similar to that described in Example 6 was carried 
out where 24.8 grams of the lithium salt of a polystyrenesulfonic acid of 
120,000 molecular weight was used instead of the polystyrene sulfonate 
used in Example 6. 
After 9 hours at 255.degree. C., the polymer produced had a sulfur content 
before washing of 2636 parts per million. The polymer was washed to remove 
monomer and dried. Analysis of the washed and dried polymer showed a 
relative formic acid viscosity of 52, with 76 carboxyl equivalents and 20 
amine equivalents per 10.sup.6 grams of polymer. The sulfur analysis 
showed 2342 parts per million of sulfur. 
The polymer was spun into fibers using the same equipment and in the same 
manner as that of Example 5. Spinning temperature was 255.degree. C., 
pressure drop across the spinning filter was 2500 psi. Undrawn yarn of 724 
denier, 14 filaments was taken up at 965 feet per minute. Five ends of 
undrawn yarn were gathered, drawn to about 3.2 times the spun length, and 
2-plied to give a yarn of 2330 denier with 140 filaments. The yarn had an 
ultimate elongation of 50 percent, and a tensile strength of 310 grams per 
denier. 
EXAMPLE 9 (COMATIVE) 
A nylon polymerization was carried out similar to that described in Example 
6, but with 29.5 grams of a neutral dry mixture of sodium carbonate and a 
polystyrenesulfonic acid of about 70,000 molecular weight, instead of a 
mixture containing lithium carbonate. 
After about 9 hours of exposure to polymerization conditions, the polymer 
was leached and dried. The analysis of the polymer showed a relative 
formic acid of about 56, with 74 carboxyl equivalents and 24 amine 
equivalents per million grams of polymer. Sulfur analysis showed 2620 
parts sulfur per million parts polymer. 
The polymer was spun in the same manner as was the polymer of Example 5. 
The spin pot temperature was about 260.degree. C., and pressure drop 
across the spin pot filter was greater than 6000 psi. A small package of 
yarn was collected having an undrawn denier of 716. Five ends of yarn were 
gathered together, drawn to about 3.2 times the spun length, and then 
2-plied to give a yarn of 2270 total denier. This yarn had an ultimate 
elongation of 43 percent and a tenacity of 3.0 grams per denier. 
The high pressure drop across the spinning filter showed that this additive 
could not be used commercially, i.e., for long spinning runs. 
EXAMPLE 10 
A solution of the magnesium salt of polystyrenesulfonic acid was prepared 
by dissolving 4.81 grams of magnesium carbonate in 70.2 grams of a 30 
percent solution of a 70,000 molecular weight polystyrenesulfonic acid, 
which contained 0.1 gram of Dow Corning antifoam 36. This solution was 
added to 1520 grams of caprolactam, and the same additives and initiator 
as were used in Example 5. This mixture was then exposed to polymerization 
conditions, leached and dried as described in Example 5. 
Polymerization time was 10 hours, and the polymer had a relative formic 
acid viscosity of 38, with about 100 carboxyl equivalents and about 20 
amine equivalents per million grams of polymer, and about 2600 parts 
sulfur per million parts polymer. 
The polymer was spun using the same spinning equipment described in Example 
2. Spinning temperature was 240.degree. C., and pressure drop across the 
sand pack was 2300 psi. The undrawn yarn was taken up at 980 feet per 
minute. Undrawn denier was 715. Five ends of the yarn were gathered, drawn 
about 3.2 times the undrawn length and 2-plied to give a yarn of 2295 
total denier. The yarn had an ultimate elongation of 52 percent, and a 
tenacity of 2.6 grams per denier. 
A control yarn, made with the sodium salt of 5-sulfoisophthalic acid was 
spun. It had an ultimate tensile strength of 3.1 grams per denier and 46 
percent ultimate elongation. This control yarn was similar to the control 
yarn of Example 5. 
The yarn of this example and the above control yarn were autoclaved at 
270.degree. F. as in Example 5, dyed comparatively in dye baths similar to 
the first mentioned dye bath of Example 5, but with 0.25 percent OWF 
Astrazon Blue 3-RL instead of 0.25 percent (OWF) Sevron Blue GCN. The dyed 
sleeves, a deep green color, were then exposed to ozone as described in 
Example 5. The results of this exposure were as follows: 
______________________________________ 
.DELTA.E 
______________________________________ 
(a) Control yarn - containing 5-sulfo- 
7.5 
isophthalate 
(b) Yarn containing the magnesium salt 
1.5 
of polystyrenesulfonic acid 
______________________________________ 
EXAMPLE 11 
A solution of the calcium salt of polystyrenesulfonic acid was prepared by 
dissolving 7.3 grams of calcium carbonate in 68.5 grams of a 30 percent 
solution of a polystyrenesulfonic acid of 70,000 molecular weight. 
This solution was added to 1520 grams of caprolactam, and the same 
additives and initiator were used as described in Example 5. This mixture 
was then exposed to polymerization conditions, and the resulting polymer 
leached and dried as described in Example 5. 
Polymerization time was about 5.5 hours. The molten polymer which was 
cloudy during the first part of polymerization gradually became clear. The 
polymer was colorless. 
The polymer had a relative formic acid viscosity of 59, with 67 carboxyl 
equivalents and 21 amine equivalents per million grams of polymer, and 
about 2300 parts of sulfur per million parts of polymer. 
The polymer was spun as described in Example 5. Spinning temperature was 
280.degree. C., and pressure drop across the sand pack was 4000 psi, 
rising from 3600 psi over a half hour of spinning. The undrawn yarn, 683 
denier, was taken up at 990 feet per minute. The yarn was drawn at a draw 
ratio of 3.2 as described in Example 5, and plied to a total denier of 
2220. The drawn yarn had an ultimate elongation of 47 percent, and a 
tenacity of 2.8 grams per denier. 
This yarn and a control yarn similar to that described in Example 10 were 
autoclaved at 270.degree. C., as in Example 5, and then dyed in dye baths 
similar to the bath described in Example 10. The dyed yarns were then 
exposed to ozone as described in Example 5. The results of ozone exposure 
were as follows: 
______________________________________ 
.DELTA.E 
______________________________________ 
(a) Control 16.4 
(b) Yarn containing the calcium salt 
3.3 
______________________________________ 
EXAMPLE 12 
A solution of the lithium salt of polystyrenesulfonic acid was prepared by 
dissolving 3.7 pounds of lithium carbonate in 47.5 pounds of a 30 percent 
solution of a 70,000 molecular weight polystyrenesulfonic acid. 
This solution was added to a solution of 18 grams of manganous chloride 
tetrahydrate, 23 grams of a 50 percent solution of hypophosphorus acid, 
and 5.9 pounds of sebacic acid in 1045 pounds of caprolactam. 
The solution was put into an agitated polymerization reactor, and the 
reactor was pressurized with 50 pounds of steam. The pressure dropped to 
atmospheric after an hour, and nitrogen gas was passed over the melt for 
about 10 hours. Then the polymer was extruded from the reactor, 
pelletized, leached to remove residual monomer and then dried. The 
resulting polymer had a relative formic acid viscosity of 47.1, with 85 
carboxyl equivalents, and 22 amine equivalents per million grams of 
polymer. The sulfur content was 2450 parts per million. 
The polymer was spun using a commercial type extruder feeding a metering 
pump which forced polymer through a filtering sand pack and to a 
spinnerette. Spinning temperature was about 250.degree. C. Polymer was 
spun for ten hours at about 40 pounds per hour. Pressure drop across the 
sand pack was steady at about 2000 psi. There was no increase in pressure 
over the ten-hour period. 
EXAMPLE 13 (COMATIVE) 
68.5 Grams of a 30 percent solution of a polystyrenesulfonic acid of 70,000 
molecular weight was added to 1520 grams of caprolactam. The same 
additives and initiator were used as described in Example 6. This mixture 
was poured into a 3-liter agitated reactor and held under polymerization 
conditions as described in Example 5 for 5.5 hours. At the end of this 
time, almost no polymerization had taken place, and the molten mixture had 
become brown. 
EXAMPLE 14 (MASTER BATCH) 
A solution of the lithium salt of polystyrene sulfonic acid was made by 
adding 42.9 grams of lithium carbonate to 554 grams of polystyrene 
sulfonic acid of about 70,000 molecular weight. This solution was added to 
1440 grams of caprolactam and 60 grams of epsilon-aminocaproic acid and 
subjected to polymerization conditions similar to those described in 
Example 5. 
After 9 hours at 255.degree. C. the resulting polymer was extruded from the 
bottom of the reactor. Analysis showed it to be about 2.1 percent sulfur. 
The polymer was pelletized, leached and dried. Analysis of this polymer 
gave a relative formic acid viscosity of 27, with 107 carboxyl equivalents 
and 36 amine equivalents per million grams of polymer. Sulfur analysis 
showed about 1.4 percent sulfur. 
The polymer was then mixed with 5.67 times its weight of a nylon polymer of 
about 70 formic acid relative viscosity, 70 equivalents of carboxyl, and 
15 equivalents of amine per million grams of polymer, and with no 
additives containing sulfur. The resulting blend had about 65 gram 
equivalents of sulfonate groups per 10.sup.6 grams of polymer. This 
polymer mixture was spun on the equipment described in Example 2. The 
polymer was spun at a temperature of 270.degree. C., drawn to about 3.2 
times its spun length and texturized. 
The texturized yarn was tufted into a carpet, which had alternating bands 
of this yarn from the blend, and yarn spun from the 70 formic acid 
relative viscosity polymer mentioned above. This carpet was dyed in a dye 
bath containing 0.5 percent (OWF) Sevron Blue GCN, and the dye assists 
described in Example 5. There was excellent contrast between the different 
bands of yarn in the carpet. 
EXAMPLE 15 
22.4 Grams of the neutral dry mixture of lithium carbonate and 
polystyrenesulfocnic acid described in Example 6, and 9.6 grams of 
5-sulfoisophthalic acid sodium salt were added to 1520 grams of 
caprolactam. The same light stabilizers and initiator were used as 
described in Example 6. This mixture was poured into a 3-liter agitated 
reactor and held under polymerization conditions as described in Example 5 
for 9.25 hours. 
The polymer was leached and dried as in Example 5. The washed and dried 
polymer had a formic acid relative viscosity of 58.6, and a sulfur content 
of 2610 parts per million. 
The polymer was spun into yarn plied and drawn as described in Example 5 
and then knitted into a sleeve. 
This yarn, the yarn from Example 8, and a control yarn similar to the 
control yarn of Example 5, were autoclaved at 280.degree. F. and then dyed 
in separate dye baths to a moss green shade as described in Example 5 but 
using Astrazon Blue 3RL instead of Sevron Blue GCN. 
These dyed sleeves were then exposed to 3 cycles of ozone fading as in 
Example 6. The result of this exposure is as follows: 
______________________________________ 
.DELTA.E 
______________________________________ 
(a) Yarn of this example 
5.9 
(b) Yarn of Example 8 
4.5 
(c) Control yarn 13.2 
______________________________________ 
DISCUSSION 
Thus, as can be seen in the comparative Examples 1-4, 9 and 13, the sodium 
and potassium salts and the acids could not be melt-processed on a 
commercial basis to provide a cationic dyeable nylon. Such products cause 
plugging of filters, and spinnerettes. On the other hand, examples of the 
embodiment of this invention, Nos. 5-8, 10-12, and 14, show the lithium, 
magnesium and calcium salts are operable to make cationic dyeable nylon. 
This is a surprising result in light of the sodium and potassium analogous 
salts failure. They also, surprisingly, (a) provide highly improved 
resistance to fading of the cationic dye due to exposure of ozone as shown 
in the examples and (b) show an improved lightfastness and washfastness. 
Comparative Examples 1-4 show that the analogous sodium salt whether as a 
solution in the lactam, the solution in the chips or dry on the polymer 
chips still will not work. The comparative examples also show that the 
potassium, zinc and aluminum salts do not work as in Example 4. 
Comparative Example 9 confirms that the sodium salt solution does not work 
and comparative Example 13 shows that the acid will not work. Surprising 
results are shown in Examples 5-8 with the lithium salt added to the 
solution in lactam, (a) starting with the sulfonic acid in solution, (b) 
as a dry mix with the lithium hydroxide, (c) with the lithium carbonate 
and (d) with 120,000 molecular weight polystyrenesulfonic acid. Example 10 
shows magnesium works. Example 11 shows calcium works. Example 12 shows a 
long term spinning can be accomplished with the lithium salt in a large 
operation. The master batch is shown in Example 14. Example 15 shows the 
preferred molecular weight modifier. The preferred range of amounts of all 
the molecular weight modifiers is from about 25 to about 90 gram 
equivalents per 10.sup.6 grams of polymer. 
The following example shows that at the prior art degree of sulfonation, 
i.e., below 90 percent, the lithium and the sodium salts are equivalent. 
It is only above 90 percent that the criticality of the nature of the 
cation, i.e., it must be Li, Ca, or Mg as shown in Examples 1 - 4 and 13 
contrasted with Examples 5 - 12 and 14 - 15. 
EXAMPLE 16 (COMATIVE) 
Example 5 was repeated using the following polymers to be spun: 
A. The control yarn from Example 5 having the sodium 5-sulfoisophthalate. 
B. The lithium salt of polystyrenesulfonic acid, as in Example 5, but the 
polystyrene being only 70 percent monosulfonated. 
C. The sodium salt of the same 70 percent sulfonated polystyrenesulfonic 
acid. 
The three polymers were each spun 30 minutes consecutively under the 
conditions of Example 5 with the following results: 
______________________________________ 
Pressure 
Pressure at Increase 
ppm of FAV Spinnerette, 
During 
Polymer 
S* ** psi*** Spinning 
______________________________________ 
A 2611 40 2600 -- 
B 2770 30.7 3000 400 
C 3155 50.3 3400 400 
______________________________________ 
*Parts per million of sulfur 
**Formic acid viscosity 
***Measured at end of run 
In startling contrast to Examples 1-3, the prior art sodium salt of 
polystyrenesulfonic acid when only 70 percent sulfonated will spin without 
the tremendous pressure build-up caused by particles in the filter as 
indicated by the pressure across the spin pot. 
EXAMPLE 17 
The following example sets forth experiments to show how cross staining of 
cationic dyeable fibers or yarn of nylon 6 polymer in a competitive dyeing 
situation was overcome. This problem is present commercially when a bi-dye 
or tri-dye plied yarn containing two or three different polymer yarns 
having different dye affinities are dyed in the same dye bath to produce a 
multicolor yarn, such as in a dyed carpet. Ideally, yarn of each polymer 
in the plied yarn attracts only the type of and amount of dye in the dye 
bath that its polymer chemistry intends. However, occasionally a polymer 
attracts a dye not intended to be absorbed. For instance, nylon containing 
the salt of polystyrene sulfonic acid can, in certain dyebaths, attract 
both the cationic and an unwanted anionic dye. This undesirable pickup of 
anionic dye is called cross staining. Another solution to the problem is 
described in U.S. Pat. No. 3,846,507. 
Cross Staining Experiment 
The experimental cationic dyeable fibers were competitively dyed on an 
equal weight basis with an acid dyeable fiber in a dyebath containing the 
following formulation (on weight of fabric). 
0.35% Telon Blue ANL (C.I. 62055) C.I. Acid Blue 25 
2.0% Ammonium sulphate 
0.5% Acetic Acid 
1.0% Leveling agent (Sandogen CCM) 
40:1 liquor ratio, 2.degree. F. per minute bath temperature rose to 
205.degree. F., held at 205.degree. F. for 1 hour. 
The amount of this acid dye on each fiber was estimated by dissolving the 
fiber in trifluorethanol and comparing the intensity of the maximum 
absorptions of the dye in the visible region of the spectrum measured on 
an ultraviolet spectrometer by measuring the height of absorption peaks on 
the chart from the machine. Table I lists the relative percentages of acid 
dye staining the cationic fiber. 
Ozone Fading Experiments 
The experimental fibers were heat set at 270.degree. F. and comparatively 
dyed with 0.5% (OWF) Astrazon Blue 5GL (C.I. Basic Blue 45). Individual 
skeins were exposed to an atmosphere containing 20 ppm ozone at 90% RH and 
104.degree. F. for 6, 12, 18, and 24 hours. The amount of dye on each 
fiber after each period of exposure was estimated by dissolving the fiber 
in trifluorethanol and comparing the intensity of the maximum absorption 
of the dye in the visible region of the spectrum, measured as above, with 
the maximum absorptions of an unexposed, dyed fiber. Table II lists the 
percentage of dye remaining on the fiber, averaged over the 24 hour 
exposure time. 
Additive A below was the additive from the polymer described in Example 16, 
polymer A with the equivalents of sulfonate per 10.sup.6 gram of polymer 
shown. Additive D below was the additive from the polymer of Example 5 
with the equivalents of sulfonate per 10.sup.6 grams of polymer shown. 
TABLE I 
______________________________________ 
STAINING 
No Sulfonate 
40 Sulfonate 
80 Sulfonate 
Equivalent Equivalent Equivalent 
from from from 
Additive D Additive D Additive D 
Sulfonate Eq. 
% Dye % Dye % Dye 
from Additive A 
Pick Up* Pick Up* Pick Up* 
______________________________________ 
0 50 32 26 
5 -- 31 22 
10 -- 26 20 
20 -- 16 20 
40 28 15 14 
80 12 12 12 
160 7 -- -- 
______________________________________ 
*In a competitive dye bath given above, competing against a yarn of 
polymer of first entry of first column. 
TABLE II 
______________________________________ 
OZONE FADING 
No Sulfonate 
40 Sulfonate 
80 Sulfonate 
Equivalent Equivalent Equivalent 
from from from 
Additive D Additive D Additive D 
Sulfonate Eq. 
% Dye % Dye % Dye 
from Additive A 
Remaining Remaining Remaining 
______________________________________ 
0 70 87 95 
5 -- 85 89 
10 -- 81 92 
20 -- 88 93 
40 66 84 89 
80 65 79 82 
160 51 -- -- 
______________________________________ 
The polymer spun into the fiber for the yarn tested for each piece of data 
in the above tables contained sulfonate from the sodium salt of 
5-sulfoisophthalic acid in all cases except the first row across each 
Table. The polymer spun into the fiber for the yarn tested for each piece 
of data contained sulfonate from the lithium salt of polystyrene sulfonate 
in all cases except the first column (down) of each Table. Thus, the 
polymer for the data in the last two columns of both Tables, with the 
exception of the first entry in each column, contains a mixture of 
sulfonate additives. Additive A, sodium salt of 5-sulfoisophthalic acid is 
the molecular weight regulator when the additives are combined. 
For points of reference, note the polymer of the first entry of the first 
column contains no sulfonate, and the polymer of the penultimate entry in 
the first column is a commercial nylon 6 cationic dyeable yarn. Note that 
the amount of dye remaining in the yarn after exposure to ozone decreases 
significantly with increasing amounts of Additive A sulfonates in the 
first column of Table II. To overcome this ozone fading, the sulfonate of 
Additive D can be used effectively, first row Table II. However, this 
gives unacceptable cross staining in certain dye baths as shown in the 
first row of Table I, in comparison to commercial nylon 6 cationic dyeable 
yarn. 
Surprisingly, combining Additive A with Additive D in a polymer does not 
significantly diminish the improved ozone fading resistance attributed to 
Additive D yet does provide most of the greatly improved cross staining 
resistance attributed to Additive A. 
TABLE III 
______________________________________ 
Comparison to Commercial Cationic 
Nylon 6 (80 Equivalent Additive A 
Equivalent of 0 Equivalent Additive D) 
Additive Improved Improved 
A Staining Ozone 
______________________________________ 
80 0 (commercial) 0 0 
20 40 
22 
14 40 
16 
20 40 
4 23 
40 40 
3 19 
80 40 0 14 
14 80 
30 
10 80 
8 27 
20 80 
8 28 
40 80 
2 24 
80 80 0 17 
______________________________________ 
Particularly note the yarn of polymers containing 40--40 (A-D), 80-40, 
40-80, and 80--80 equivalents of sulfonate have improved ozone fading by 
14 to 24% with only a few percent loss of staining or no loss. The figures 
of Table III are the absolute percent difference, not a ratio, taken from 
Table I and Table II. 
EXAMPLE 18 
A solution of the lithium salt of polystyrenesulfonic acid was prepared by 
dissolving 5.334 grams of lithium hydroxide monohydrate in 200.4 grams of 
a 9 percent aqueous solution of a 500,000 molecular weight 
polystyrenesulfonic acid. The pH of this solution was 6.3. This entire 
solution was added to 1520 grams of caprolactam at 90.degree. C. Manganese 
chloride (0.0576 gram) and 0.1640 gram of a 50 percent aqueous solution of 
hypophosphorous acid were added to serve as light stabilizers. The 
solution was homogeneous. 
This solution was poured into a 3-liter agitated glass reactor equipped 
with a heating mantle, and a gas inlet and outlet to provide a nitrogen 
blanket over the molten mixture. 80 Grams of epsilon-aminocaproic acid was 
added as a polymerization initiator, and 6.8 grams of sebacic acid was 
added as a molecular weight regulator. The mixture was then heated over a 
period of about 1 hour to about 255.degree. C. When the water flashed off 
there was no phase separation. 
At the end of 71/4 hours a polymer ribbon was extruded from the bottom of 
the reactor, which was almost colorless, without lumps and of constant 
cross section. Unreacted caprolactam, about 10 percent by weight, was 
removed by water extraction. The washed and dried polymer was submitted 
for analysis. 
The formic acid relative viscosity was 61, with 75 gram equivalents of 
carboxyl and 22 gram equivalents of amine per 10.sup.6 grams of polymer. 
Sulfur analysis by X-ray fluorescence of the washed and dried polymer 
showed 2095 parts per million sulfur, or about 65 equivalents of sulfur 
per 10.sup.6 grams of polymer. A sample of the unwashed polymer contained 
about 2090 parts per million sulfur. The theoretical concentration of 
sulfur, based on the amount of polystyrenesulfonic acid salt added was 
about 2100 parts per million. 
The polymer was submitted for spinning. It was spun using the same spinning 
equipment as described in previous examples. The spinning temperature was 
about 265.degree. C. Pressure drop across the sand pack in the spin pot 
was about 1600 psi. 
The undrawn yarn had a total denier of 711 or an average of 50 denier per 
filament. The free fall yarn had a formic acid relative viscosity of 60, 
with 78 gram equivalents of carboxyls and 25 gram equivalents of amines 
per 10.sup.6 grams of polymer. Five ends were gathered and drawn to 3.2 
times the spun length, and then 2-plied to give a yarn of 2250 total 
denier. This yarn had a tensile strength of 2.9 grams per denier and an 
ultimate elongation of 44 percent. A control yarn of nylon 6, not 
containing any sulfonate, but which contained a dicarboxylic acid as a 
molecular weight regulator had a tensile strength of 3.3 grams per denier 
and an ultimate elongation of 50 percent. 
This yarn and a control yarn which had 81 gram equivalents of sulfonate 
groups per 10.sup.6 grams of polymer, similar to that described in Example 
5, were knitted into to that described in Example 5, were knitted into 
sleeves, autoclaved as described in Example 5 and dyed in separate dye 
baths composed as was the dye bath of Example 5. 
The dyed sleeves were then exposed for 6, 12 and 18 hours in an atmosphere 
of 20 parts per hundred million (v/v) of ozone at a temperature of 
104.degree. F. at a relative humidity of 95-100 percent. 
The degree of ozone fading was determined by Gray scale readings. They were 
as follows: 
______________________________________ 
Gray Scale Readings 
6 Hours 12 Hours 18 Hours 
______________________________________ 
(a) Control polymer 4 3 1.2 
(b) Polymer with 4.5 4 3 
lithium salt of 
polystyrenesulfonic acid 
______________________________________ 
Higher Gray scale numbers indicate lesser degree of fading. 
EXAMPLE 19 
A solution of the lithium salt of polystyrenesulfonic acid was prepared by 
dissolving 6.28 grams of lithium hydroxide monohydrate in 67 grams of 34.8 
percent aqueous solution of a 40,000 molecular weight polystyrenesulfonic 
acid. The pH of this solution was 4.5. This entire solution was added to 
1520 grams of caprolactam at 90.degree. C. Manganese chloride (0.0576 
gram) and 0.1640 gram of a 50 percent aqueous solution of hypophosphorous 
acid were added to serve as light stabilizers. The solution was 
homogeneous. 
This solution was poured into a 3-liter agitated glass reactor equipped 
with a heating mantle, and a gas inlet and outlet to provide a nitrogen 
blanket over the molten mixture. 80 Grams of epsilon-aminocaproic acid was 
added as a polymerization initiator, and 6.8 grams of sebacic acid were 
added as a molecular weight regulator. The mixture was then heated over a 
period of about 1 hour to about 255.degree. C. When the water flashed off 
there was no phase separation. 
At the end of 11 hours a polymer ribbon was extruded from the bottom of the 
reactor, which was almost colorless, without lumps and of constant cross 
section. Unreacted caprolactam, about 10 percent by weight, was removed by 
water extraction. The washed and dried polymer was submitted for analysis. 
The formic acid relative viscosity was 53.5 with 68 gram equivalents of 
carboxyl and 22 gram equivalents of amine per 10.sup.6 grams of polymer. 
Sulfur analysis by X-ray fluorescence of the washed and dried polymer 
showed 2120 parts per million sulfur, or about 67 equivalents of sulfur 
per 10.sup.6 grams of polymer. A sample of the unwashed polymer contained 
about 2230 parts per million sulfur. The theoretical concentration of 
sulfur, based on the amount of polystyrenesulfonic acid salt added, was 
2240 parts per million. 
The polymer was submitted for spinning. It was spun using the same spinning 
equipment as described in Example 5. The spinnerette had 14 holes each in 
the shape of a "Y" to get a yarn with a "Y" cross section. The spinning 
temperature was about 260. Pressure drop across the sand pack in the spin 
pot was about 2000 psi. 
The yarn was treated as in the above example, including drawing, plying to 
2250 denier, knitting into sleeves, autoclaving, and dyeing. The dyed 
sleeve and a dyed control sleeve identical to that used in the above 
example were exposed to 20 parts ozone per hundred million (by volume) of 
air for 6, 12, and 18 hours. The Gray Scale results are as follows: 
______________________________________ 
6 Hours 12 Hours 18 Hours 
______________________________________ 
(a) Control polymer 
4 3 1.2 
(b) Polymer containing 
4-5 4 3 
the lithium salt of 
polystyrene 
______________________________________ 
The above two examples show that acceptable cationically dyeable yarns can 
be made from polystyrene-sulfonic acids of molecular weights from 500,000 
to 40,000 or less. The 9 percent solution of the 500,000 molecular weight 
polysulfonate is as viscous as can be easily handled commercially. The 
40,000 molecular weight polystyrene sulfonate is not the lower limit in 
molecular weight because the loss of sulfonic groups upon washing of the 
polymer chips to remove impurities was not significant. 
EXAMPLE 20 
10 Drops of Dow Corning Antifoam 35 were added to 100 cc. of distilled 
water. 18.2 Grams of the magnesium salt of 120,000 molecular weight 
polystyrenesulfonic acid, and 18.2 grams of a neutral mixture of lithium 
carbonate and 120,000 molecular weight polystyrenesulfonic acid were added 
slowly with agitation. This entire solution was added to 1520 grams of 
caprolactam at 90.degree. C. Manganese chloride (0.0576 gram) and 0.1640 
gram of a 50 percent aqueous solution of hypophosphorous acid were added 
to serve as light stabilizers. The solution was homogeneous. 
This solution was poured into a 3-liter agitated glass reactor equipped 
with a heating mantle, and a gas inlet and outlet to provide a nitrogen 
blanket over the molten mixture. 80 Grams of epsilonaminocaproic acid was 
added as a polymerization initiator and 6.8 grams of sebacic acid was 
added as a molecular weight regulator. The mixture was then heated over a 
period of about 1 hour to about 255.degree. C. When the water flashed off, 
there was no phase separation. 
At the end of 63/4 hours a polymer ribbon was extruded from the bottom of 
the reactor which had a yellow tint, without lumps and of constant cross 
section. Unreacted caprolactam, about 10 percent by weight, was removed by 
water extraction. The washed and dried polymer was submitted for analysis. 
The formic acid relative viscosity was 65, with 91 gram equivalents of 
carboxyl and 43 equivalents of amine per 10.sup.6 grams of polymer. Sulfur 
analysis by X-ray fluorescence of the washed and dried polymer showed 2540 
parts per million sulfur, or about 80 equivalents of sulfur per 10.sup.6 
grams of polymer. The theoretical concentration of sulfur, based on the 
amount of polystyrenesulfonic acid salt added, was 2540 parts per million. 
The polymer was submitted for spinning. It was spun using the same spinning 
equipment as described in Example 2. The spinnerette had 14 holes each in 
the shape of a "Y" to get a yarn with a "Y" cross section. The spinning 
temperature was about 280.degree. C. Pressure drop across the sand pack in 
the spin pot was about 2400 psi. 
The undrawn yarn had a total denier of 720 or an average of 51 denier per 
filament. The free fall yarn had a formic acid relative viscosity of 58. 
Five ends of this yarn were gathered and drawn to 3.2 times the spun 
length, and then 2-plied to give a yarn of 2320 total denier. This yarn 
had a tensile strength of 2.9 grams per denier, and an ultimate elongation 
of 45 percent. A control yarn (pure nylon 6) spun at the same time had a 
tensile strength of 3.2 grams per denier and an ultimate elongation of 50 
percent. 
A control yarn was made from a nylon 6 polymer having a formic acid 
relative viscosity of 50, about 85 carboxyl equivalents per 10.sup.6 
grams, about 23 amine equivalents with about 81 sulfonate group 
equivalents, from the sodium salt of sodium 5-sulfoisophthalate. It was 
spun on the same spinning equipment as described above, drawn, knitted 
into sleeves, and autoclaved at 270.degree. as in Example 5. 
The yarns were dyed in separate dye baths to to a moss green shade in a dye 
bath composed as in Example 5. 
The dyed sleeves were then exposed for 6, 12, and 18 hours in an atmosphere 
of about 20 parts per hundred million of ozone, at a temperature of 
104.degree. F., at a relative humidity of 95-100 percent. 
The results of ozone exposure are listed below: 
______________________________________ 
.DELTA.E 
6 Hours 12 Hours 18 Hours 
______________________________________ 
(a) Control, polymer with 
6.0 10.5 15.1 
5-sulfoisophthalate 
(b) Polymer with lithium 
1.1 2.3 3.8 
salt of polystyrene 
sulfonic acid 
______________________________________ 
EXAMPLE 21 
10 Drops of Dow Corning Antifoam 35 were added to 100 cc. of distilled 
water. 12.95 Grams of the magnesium salt of 120,000 molecular weight 
polystyrenesulfonic acid, and 12.65 grams of a mixture of lithium 
carbonate and 120,000 molecular weight polystyrenesulfonic acid were mixed 
in slowly to minimize foaming. The solution has a pH of about 7.0. This 
entire solution was added to 1520 grams of caprolactam at 90.degree. C. 
Manganese chloride (0.0576 gram) and 0.1640 gram of a 50 percent aqueous 
solution of hypophosphorous acid were added to serve as light stabilizers. 
The solution was homogeneous. 
This solution was poured into a 3-liter agitated glass reactor equipped 
with a heating mantle and a gas inlet and outlet to provide a nitrogen 
blanket over the molten mixture. 80 Grams of epsilon-aminocaproic acid was 
added as a polymerization initiator, and 9.02 grams of 5-sulfoisophthalic 
acid sodium salt was added as a molecular weight regulator and dye site 
source. The mixture was then heated over a period of about 1 hour to about 
255.degree. C. When the water flashed off, there was no phase separation. 
At the end of 12 hours a polymer ribbon was extruded from the bottom of the 
reactor, which was slightly yellow, without lumps and of constant cross 
section. Unreacted caprolactam, about 10 percent by weight, was removed by 
water extraction. The washed and dried polymer was submitted for analysis. 
The formic acid relative viscosity was 58, with 84 gram equivalents of 
carboxyl and 22 gram equivalents of amine per 10.sup.6 grams of polymer. 
Sulfur analysis by X-ray fluorescence of the washed and dried polymer 
showed 2309 parts per million sulfur, or about 72 equivalents of sulfur 
per 10.sup.6 grams of polymer. A sample of the unwashed polymer contained 
about 2636 parts per million sulfur. The theoretical concentration of 
sulfur, based on the amount of polystyrenesulfonic acid salt added was 
2540 parts per million. 
The polymer was submitted for spinning. It was spun using the same spinning 
equipment as described in Example 2. The spinnerette had 14 holes each in 
the shape of a "Y" to get a yarn with a "Y" cross section. The spinning 
temperature was about 275.degree. C. Pressure drop across the sand pack in 
the spin pot rose by about 600 psig during the half-hour spinning. 
The undrawn yarn had a total denier of 717 or an average of 51 denier per 
filament. The free fall yarn had a formic acid relative viscosity of 46. 
Five ends of this yarn were gathered and drawn to 3.2 times the spun 
length, and then 2-plied to give a yarn of 2352 total denier. This yarn 
had a tensile strength of 2.5 grams per denier, and an ultimate elongation 
of 44 percent. A control yarn (pure nylon 6) spun at the same time had a 
tensile strength of 3.2 grams per denier and an ultimate elongation of 50 
percent. 
A control yarn was made from a nylon 6 polymer having a formic acid 
relative viscosity of 50, about 85 carboxyl equivalents per 10.sup.6 
grams, about 23 amine equivalents with about 81 sulfonate group 
equivalents, from the sodium salt of sodium 5-sulfoisophthalate. It was 
spun on the same spinning equipment as described above, drawn, knitted 
into sleeves, and autoclaved at 270.degree. F. as in Example 5. 
The yarns were dyed in separate dye baths to a moss green shade in a dye 
bath composed as in Example 5. 
The dyed sleeves were then exposed for 6, 12 and 18 hours in an atmosphere 
of about 20 parts per hundred million of ozone, at a temperature of 
104.degree. F., at a relative humidity of 95-100 percent. 
The results of ozone exposure are listed below: 
______________________________________ 
.DELTA.E 
6 Hours 12 Hours 18 Hours 
______________________________________ 
(a) Control, polymer 
6.0 10.5 15.1 
with 5-sulfoiso- 
phthalate 
(b) Polymer with lithium 
1.0 2.8 3.1 
salt of polystyrene 
sulfonic acid 
______________________________________ 
This example shows that a mixture of soluble salts of polystyrenesulfonic 
acid can be used with a molecular weight regulator which bears a 
sulfonate. 
EXAMPLE 22 
53.05 Grams of a 34.8 percent aqueous solution of a 70,000 molecular weight 
polystyrene sulfonic acid is added to 1520 grams of caprolactam at 
90.degree. C. Manganese chloride (0.0576 gram) and 0.1640 gram of a 50 
percent aqueous solution of hypophosphorous acid are added to serve as 
light stabilizers. The solution is homogeneous. 
This solution is poured into a 3-liter agitated glass reactor equipped with 
a heating mantle, and a gas inlet and outlet to provide a nitrogen blanket 
over the molten mixture. 80 Grams of epsilonaminocaproic acid is added as 
a polymerization initiator. 4.095 Grams of lithium hydroxide monohydrate 
are added to neutralize the polystyrene sulfonic acid, and 6.8 grams of 
sebacic acid is added as a nylon molecular weight regulator. The mixture 
is then heated over a period of about 1 hour to about 255.degree. C. When 
the water flashes off there is no phase separation. 
At the end of about 8 hours, a polymer ribbon is extruded from the bottom 
of the reactor. Unreacted caprolactam, about 10 percent by weight, is 
removed by water extraction. 
The formic acid relative viscosity is about 55 with about 75 gram 
equivalents of carboxyl and 25 gram equivalents of amine per 10.sup.6 
grams of polymer. The theoretical concentration of sulfur, based on the 
amount of polystyrenesulfonic acid salt added, was 2240 parts per million. 
EXAMPLE 23 
The following solutions were prepared by adding various amounts of lithium 
hydroxide monohydrate to 53.05 grams of an aqueous solution of 
polystyrenesulfonic acid. After the lithium hydroxide dissolved, the pH of 
the solution was measured with a Fisher Accumet.RTM. Model 230 pH/ion 
meter. 
______________________________________ 
% of 
Neutralization* 
______________________________________ 
Solution A 
4.0758 g. LiOH . H.sub.2 O 
pH = 4.0 99.8 
Solution B 
4.0840 g. LiOH . H.sub.2 O 
pH = 7.0 100 
Solution C 
4.0960 g. LiOH . H.sub.2 O 
pH = 9.5 100.3 
Solution D 
4.0347 g. LiOH . H.sub.2 O 
pH = 2.2 98.8 
______________________________________ 
##STR6## 
These solutions were poured into four different lots of 1520 grams of 
caprolactam at 90.degree. C. Manganese chloride (0.0576 gram) and a 50 
percent aqueous solution of hypophosphorous acid (0.1640 gram) were 
added. These solutions were each poured into 3-liter agitated glass 
reactor equipped with heating mantles, and provided with an inert gas 
sweep. 80 Grams of epsilon-aminocaproic acid and 6.8 grams of sebacic 
acid was added to each reactor and the mixtures stirred for about 12 
hours at 250.degree. C. At the end of this time a tough strand product 
was extruded from the bottom of the reactor, cooled in a water trough, 
and pelletized. The polymer color in all cases was a light yellow, 
irrespective of pH. The degree of polymerization was not lowered by the 
presence of either high or low pH sulfonates, based on the amps required 
This shows that, in glass reactors at least, a wide range of pH's of the 
lithium salt of polystyrenesulfonic acid can be used to make an acceptable 
nylon polymer. 
DISCUSSION 
Example 18 shows that a salt having a molecular weight as high as 500,000 
is still feasible, and Example 19 shows that a 40,000 molecular weight 
salt is still not the lower limit of molecular weight for the workable 
salts of this invention. 
It can be seen from Examples 20 and 21 that mixtures of the lithium, 
magnesium and calcium salts of sulfonate polystyrene can also be used for 
this invention. 
Example 22 proposes that the cations of this invention can be added to 
polystyrene sulfonic acid to form the salt in the reactor rather than in 
the aqueous solution prior to addition to the reactor. 
Example 23 shows that, since the polystyrene sulfonic acid is a strong acid 
and the Li (and Mg and Ca) salt is a strong base, the pH of the aqueous 
solution swings widely with only small amounts of excess acid or base. 
This small amount of acid or base is so thoroughly diluted by the 
overwhelming amount of polymer precursor (lactam, etc.) that the pH of the 
aqueous solution of the sulfonated polystyrene salt of this invention has 
very little effect on the pH during polymerization. Thus, the wide 
operable range of pH of the salt to be added is possible, and explained. 
Since both Li, Mg, and Ca salt and the sulfonic acid, as commercially 
available, probably have minor amounts of other cations present as 
impurities, the remainder of the aqueous salt solution, i.e., that not 
neutralized as Li, Mg or Ca salt, will be either the sulfonic acid or a 
salt having a cation from Group I or II of the Periodic Table (as reported 
by the Committee of the International Union of Chemistry, hereinafter, 
C.I.U. of C.). 
It can be seen that if over 98 percent of the sulfonated polystyrene salt 
is the Li, Mg or Ca salt thereof, with the remainder being the sulfonic 
acid or a cationic from Group I or II, the invention should be operable. 
Preferably, the sulfonated polystyrene salt is neutralized to between 
about 98.8 and 100.3 percent at neutralization, corresponding to a pH of 
between about 2.2 and about 9.5.