Flock treatment

Flock is treated with a metal salt of a long chain aliphatic acid to control static charges, increase flow and reduce waste. The salt may be applied from a water solution, or from an aqueous mixture of the metal and the acid under high shear mixing conditions under which at least a part of the acid is converted to the salt.

The present invention relates to treatment of flock to facilitate screening 
the flock, reduce waste, and improve the uniformity and the density of the 
flocked surface of the fabric produced from the flock. Briefly, the 
invention comprises adding a linear organic carboxylic acid containing at 
least 8 and preferably at least 10-14 carbon atoms to water in which the 
flock is dispersed, the water containing a small amount of a divalent 
metal cation such as cation of group II A or B of the periodic table of 
elements, for example calcium, zinc, etc., or adding the acid in the form 
of a salt of a group II metal, and separating and drying the flock. 
Preferred acids are those containing 14-18 carbon atoms. The invention 
also permits the use of other ions, such as trivalent and monovalent 
metals, but, although they give beneficial results, their performance is 
less favorable than divalent metal ions. 
Flock is made by cutting short lengths of fiber 0.05 to 1.5 inches long 
from continuous filaments of 1.5 to 40 denier per filament (dpf) of 
synthetic or man-made polymer. Best results are usually obtained with 
filaments of 3-15 dpf cut to lengths of 1-8 mm, preferably 3 dpf cut to 2 
mm length. Generally longer lengths require higher deniers to provide the 
necessary stiffness. A particularly useful process for cutting flock is 
described in U.S. application of Winston E. Hagborg, Ser. No 437,617, 
filed Jan. 29, 1974, now U.S. Pat. No. 3,916,040. In the process described 
in that application, a tow is scoured to remove previously applied 
finishes, and rinsed. While still in wet condition, the tow is directed to 
a cutter which cuts it into fibers of the desired length. Either prior to 
or after the cutting step, the fibers are subjected to a finishing 
operation in which suitable chemicals are applied. 
The flock then is applied onto a substrate by screening it and passing it 
through an electrostatic field. Under the influence of the field, the 
flock is directed onto a surface in an orientation perpendicular to the 
backing and bonded with adhesive. See U.S. Pat. No. 3,490,938 and 
publications cited there. 
In accordance with the present invention, the tow from which the flock is 
cut, but preferably the flock itself after cutting, is treated with a salt 
of a metal ion with a linear saturated aliphatic monocarboxylic acid 
containing at least 8 carbon atoms, with or without prior scouring, in an 
amount effective to improve the flow of the flock, as hereinafter defined. 
The salt may be applied directly, or alternatively, the flock may be 
treated with a linear saturated aliphatic monocarboxylic acid containing 
at least 8 carbon atoms while dispersed in water, which contains a low 
concentration of the metal ion. The latter procedure requires hot water 
and high shear mixing to facilitate ion/acid reaction. 
The invention is particularly applicable to flock composed of synthetic 
polymers, such as flock composed of linear polyester of the type having 
repeating units connected by ester linkages in the polymer chain (e.g., 
polyethylene terephthalate and its copolymers), flock composed of 
polyamide (nylon) of the type having a repeating units connected by amide 
linkages in the polymer chain (i.e., nylon 66, nylon 6, etc.) and flock 
composed of polyolefin (i.e., polyethylene, polypropylene, etc.). The 
invention also has been found useful with flock cut from man-made 
filaments including rayon, cellulose acetate and cellulose triacetate. 
The linear saturated aliphatic monocarboxylic acid used in the present 
invention has at least 8 carbon atoms and may be, e.g., palmitic acid, 
stearic acid, myristic acid and arachidic acid. Mixtures of such acids may 
be used. Examples of commercially available acids are Emery 132, 150 and 
153. For reasons of cost, acids containing more than 20 carbon atoms are 
unattractive. Experiments have revealed that salts in which the acid 
contains 8 carbon atoms are of marginal usefulness, acids containing 10 
carbon atoms give good results, but acids containing 12-14 carbon atoms or 
more are especially preferred. Mixtures of acids may be used. Appropriate 
esters of these acids which either contain or saponify to give free acid 
may also be used. 
The metal ions preferably are divalent metal ions. These may be ions 
derived from metals of group II A or B (see Periodic Table of the 
Elements, Handbook of Chemistry and Physics, 44th Edition, Chemical Rubber 
Publishing Co., pages 448-449, Groups IIa and IIb). These include divalent 
ions of zinc, calcium, or magnesium. However, divalent metal ions derived 
from other metals may be used such as lead, manganese, barium, nickel, 
iron, and tin. Beneficial results also are obtained with monovalent and 
trivalent metals such as lithium and aluminum, but they are not equal to 
the results with divalent metals. 
The amount of acid used is between about 0.025 to 0.4 g/liter of water in 
the treating solution at a fiber concentration of 20 g/l; preferably in 
the case of stearic acid the amount is 0.05 to 0.2 g/liter. If excess acid 
is used, in relation to the amount of metal ion, poor results are observed 
because free acid starts to deposit on the fibers in preference to the 
salt, apparently with the fatty end of the acid deposited against the 
fibers, and the hydrophilic end of the molecule extending from the fibers. 
The acid is applied in water containing greater than about 3 parts per 
million of the divalent metal ion. The metal ion may be introduced in the 
form of a soluble salt, such as a chloride, or it may represent natural 
hardness in the water. Preferably, however, the acid is applied in the 
form of a preformed salt of a divalent metal and calcium stearate is 
especially preferred because of its low cost, ready availability and 
effectiveness. In the case of using a preformed salt, the concentration of 
the salt used is about the same as for the acid, preferably greater than 
0.1 g/l at a fiber concentration of 20 g/l. Higher concentrations of 
fibers make the mixture thicker and hard to stir; they require more of the 
salt. At lower fiber concentration, less salt may be used. When preformed 
salt is used, excess salt causes no difficulty except for possible dust 
problems arising from dust of the excess salt coming off the fibers. 
The water containing a preformed metal salt of the acid may simply be 
agitated with the flock, using sufficient water to thoroughly wet the 
flock. The water may be at 50.degree. F or higher temperature. On the 
other hand, when the free acid is used with water containing metal ions, 
it has been found necessary to suspend the fibers in the water and subject 
the suspension to mixing in a high shear mixer at a temperature of at 
least about 48.degree. C. This procedure has been carried out using a 
Daymax ultra high speed mixing machine purchased from Day Mixing, 4932 
Beech St. cincinnati, Ohio. On a laboratory scale, suitable conditions can 
be achieved in a Waring blender. 
These conditions are believed to disperse the free acid, which is water 
insoluble, and facilitate chemical reaction between it and the metal ions 
(see Blodgett, Journal of the American Chemical Society, Vol. 57, page 
1007 (1935), and Langmuir, Journal of the American Chemical Society, Vol. 
58, page 284 (1936)). C.sub.14 tracer studies show this procedure appears 
to deposit a mixture of free acid and metal salt, which is believed to 
result in a surface composed of hydrophobic CH.sub.3 -end groups. It is 
less desirable than using the metal salt, because it requires substantial 
capital investment for high shear mixing equipment and also because the 
water must be heated to a temperature of about 48.degree. C or more. Both 
procedures are believed to form a monomolecular film of salt or salt mixed 
with free acid on the flock. It also has been found possible to apply the 
acid itself or the preformed salts from solutions in organic solvents.

The following examples illustrate the process, all parts and percentages 
being by weight. 
EXAMPLE 1 
To 1 liter of water there is added 20 grams of 3 dpf/2 mm prescoured flock 
(scoured and rinsed prior to cutting) and then there is added with mixing 
0.15 to 0.3 grams of calcium stearate. The liquid is agitated for about 30 
seconds and then the flock is spun and dried to a moisture content of 
about 4.5%. At this point the flock has a volume resistivity of about 
10.sup.12 to 10.sup.13 ohm-cm, as measured by placing a 2 gram sample 
between parallel copper electrodes in a dielectric cell, with a potential 
of 500 volts applied. Resistivity is measured on a megohmmeter. 
Flock performance for this size flock is measured by adding 15 grams of 
fibers to a cylindrical container whose bottom consists of a #12 mesh U.S. 
Standard sieve. A rotating brush is lowered to screen level and the sample 
is brushed for 300 rotations of the brush. The percentage of fibers 
passing through the screen is determined by weighing and recorded as 
percent flow. 
Static charge is evaluated empirically by the amount of flock adhering to 
the sieve used in measuring flow. An arbitrary scale is used with zero 
indicating lowest static and 5 the highest level observed. 
Samples also were evaluated with an AC-DC flocking unit made by C-Labs, 
Inc. This consists of a screen having round holes approximately the same 
diameter as a 12 mesh sieve. Below the screen is a series of cylindrical 
electrodes coated with dielectric material which generate an electric 
field 40-50 K.V. A.C. Below these electrodes, there is a fabric coated 
with adhesive which moves below the screen while the screen is brushed 
with a rotating brush. 
This procedure has been used with Nylon 6, Nylon 66, polyethylene 
terephthalate and rayon flock, and, with slightly higher concentrations of 
the salt, with polypropylene, cellulose acetate and cellulose triacetate 
flock. Flows of greater than 95% have been observed. Similar results were 
observed with 1.5 denier nylon and rayon flock cut to 2 mm. 
EXAMPLE 2 
The following results are from the treatment of 80 gram samples of fiber (3 
dpf/2 mm) in 4 liters of deionized H.sub.2 O at room temperature and 
containing the specified concentrations of calcium stearate, 1 minute 
treatment times at very low mixing conditions. The measurement were 
performed as described above. Two numbers are given, the first being the 
present flow and the second being the static charge on the aforesaid 
arbitrary scale. 
Table 1 
______________________________________ 
Calcium Stearate 
Ny- Ny- Polyester Poly- 
Concentration 
lon lon (Polyethylene 
pro- Ray- 
(Grams per Liter) 
66 6 Terephthalate) 
pylene 
on 
______________________________________ 
.02 33-4 45-4 29-4 11-4 96-0 
.09 33-4 75-2 56-4 31-4 
.11 75-2 94-1 70-3 32-3 96-0 
.13 77-2 96-0 94-2 64-2 
.15 94-1 96-0 97-0 70-1 
.22 97-0 97-0 96-0 74-1 97-0 
.30 97-0 98-0 96-0 85-1 
.40 97-0 96-0 96-0 98-0 
______________________________________ 
When similar experiments were carried out with zinc stearate and magnesium 
stearate, very little difference in performance was found. 
EXAMPLE 3 
The following results were observed when various finishes were tested in 
the manner described above on Nylon 66 flock (3 dpf/2 mm). The two numbers 
given are respectively percent flow and static charge. 
Table 2 
______________________________________ 
Conc. (g/l) 
ZnSt.sub.2 
MgSt.sub.2 
LiSt NaSt AlSt.sub.3 
______________________________________ 
.09 46-3 45-3 32-4 9-4 38-4 
.11 81-1 46-3 44-3 14-4 31-4 
.13 91-1 49-3 47-4 12-4 12-4 
.15 97-0 47-4 9-4 
.22 97-0 49-4 12-4 56-4 
.30 98-0 79-1 41-4 
.40 97-0 94-0 54-4 
1.0 96-0 97-0 40-4 13-4 60-4 
______________________________________ 
EXAMPLE 4 
Nylon 66 flock (3 dpf/2 mm) was tested using stearic acid in water under 
high shear mixing conditions, the water containing calcium ion in various 
concentrations to evaluate dependence on calcium content. Fiber 
concentration was 20 g/l H.sub.2 O at 160.degree. F. Stearic acid was at a 
concentration of 0.10 g/l. Reaction time was 5 minutes to allow for 
equilibrium to be reached, pH of the water was 6.3. 
Table 3 
______________________________________ 
Calcium Content (ppm) 
% Flow Static 
______________________________________ 
0 30 4 
.50.+-..05 45 3 
1.0.+-..1 45 4 
2.0.+-..2 89 2 
3.0.+-..3 70 2 
4.0.+-..4 72 2 
5.0.+-..5 75 1 
6.0.+-..6 95 1 
7.0.+-..7 97 1 
8.0.+-..8 95 0 
10.0.+-.1 96 0 
______________________________________ 
Nylon 6 was found to respond in about the same way as Nylon 66. 
EXAMPLE 5 
When Nylon 66 fibers were treated with glycerol stearate, and stearic acid 
in deionized water, even at much higher concentrations, the results were 
very poor by comparison as shown in Table 4. 
Table 4 
______________________________________ 
Stearic Acid Glycerol Stearate 
Conc. g/l 
% Flow-Static % Flow-Static 
______________________________________ 
.00 4.6 - 4 -- 
.025 6.0 - 4 -- 
.05 6.6 - 4 -- 
.1 5.4 - 4 42 - 4 
.2 9.0 - 4 51 - 4 
.4 8.9 - 4 20 - 4 
.8 10.0 - 4 57 - 4 
1.0 12.2 - 4 18 - 4 
1.6 12.0 - 4 24 - 4 
2.0 10.0 - 4 21 - 4 
______________________________________ 
These measurements were made on flock treated in water and the finish at 
160.degree. F, H.sub.2 O and high shear mixing conditions to allow a 
maximum opportunity for reaction. Low temperature H.sub.2 O gives 
approximately the same results. 
EXAMPLE 6 
Similar experiments were performed in the same manner as those reported in 
Table 3 using cupric and stannous ions and stearic acid. A range from 0 - 
0.032 g/l (32 ppm) was covered. At the pH used (6.5) significant reaction 
should occur between the acid and the stannous and cupric ions. However, 
the stannous ion gave results which were not promising although the cupric 
ion gave a moderate increase in flow. 
Table 5 
______________________________________ 
Conc. of Chloride 
Salt (ppm) % Flow CuCl.sub.2 
% Flow SnCl.sub.2 
______________________________________ 
0 17 - 4 10 - 4 
4 06 - 4 9 - 4 
8 04 - 4 6 - 4 
16 24 - 4 6 - 4 
32 39 - 4 6 - 4 
64 41 - 4 -- 
128 42 - 4 -- 
______________________________________ 
In these cases, the reaction between the metal ion and the acid did not 
take place properly. When preformed salts were used as revealed below, the 
corresponding salts exhibited much better performance. 
EXAMPLE 7 
A study was made by a commercial mill which produces a flocked blanket, to 
determine differences in fiber waste between flock treated according to 
the present invention with calcium stearate and flock treated with a 
commercial finish. The fiber used was 3 dpf, 2 mm length Nylon 66. This 
study is based on consumption of 600,000 lbs. of the commercial fiber and 
120,000 lbs. of the calcium stearate treated fiber. 
Table 6 
______________________________________ 
Surplus 
Balled Flocking 
Drier Oven Unattached 
Treatment 
Machine Waste Waste Flock Waste 
______________________________________ 
Commercial 
6% .92% 10.5% 
CaSt.sub.2 
0.5% .31% 0.6% 
______________________________________ 
EXAMPLE 8 
Nylon 66 flock (2 dpf/3 mm) was treated with calcium salts and linear 
saturated aliphatic monocarboxylic acids of chain length as indicated 
below, at the indicated concentrations, in water at room temperature. The 
results were as follows: 
Table 7 
______________________________________ 
Chain Length 
Conc. (gyl) % Flow Comment 
______________________________________ 
C-8 .5 38 Poor 
1.0 43 Poor 
C-10 .5 68 Fair 
1.0 91 Excellent 
C-12 .5 90 Excellent 
1.0 95 Excellent 
C-14 .5 81 Good 
1.0 95 Excellent 
C-16 .5 93 Excellent 
1.0 95 Excellent 
C-18 .5 95 Excellent 
1.0 96 Excellent 
______________________________________ 
EXAMPLE 9 
Additional experiments were carried out with a variety of metal salts on 
Nylon 66 (2 dpf/3 mm) and percent flow was measured. The flock was at a 
concentration of 20 g/l, in deionized water at 140.degree. F. The results 
were as follows. 
Table 8 
__________________________________________________________________________ 
SALT 
Alumi- 
Stan- Plum- 
Lith- Cal- 
Cal- 
Alumi- 
Aluminum 
num Di- 
Barium 
Nickel 
Ferric 
nous 
Cupric 
Mangan- 
bous 
ium Sodium 
cium 
cium 
num Monochlo- 
chloride 
Conc 
Diste- 
Triste- 
Stear- 
Stear- 
Stear- 
ese Di- 
Stear- 
Stear- 
Stear- 
Laur- 
Palmi- 
Triste- 
ride 
Mono- 
g/l 
arate 
arate 
ate ate* 
ate stearate 
ate ate ate ate tate 
arate 
stearate 
stearate 
__________________________________________________________________________ 
.1 68% 48% 47% 55% 94% 56% 76% 37% Foam 
75% 84% 31% 37% 30% 
.2 97% 30% 53% 67% 94% 57% 77% 77% Foam 
89% 94% 44% 40% 41% 
.4 97% 30% 58.7% 
4.4% 
94% 87% 97% 49% Foam 
91% 93% 46% 46% 36% 
.8 97% 49% 43% 24% 88% 90% 97% 38% Foam 
93% 94% 42% 54% 56% 
1.2 
97% 39% 55% 24% 90% 90% 92% 49% Foam 
94% 95% 52% 47% 58% 
1.6 
97% 30% 69% 31% 90% 90% 97% 38% Foam 
94% 94% 49% 52% 65% 
2.0 
95% 45% 73% 44% 90% 89% 92% 31% Foam 
94% 96% 50% 55% 64% 
4.0 
94% 63% 82% 44% 95% 89% 95% 47.3% 
Foam 
90% 91% 51% 43% 75% 
__________________________________________________________________________ 
*Believed to be unstable, to form stannic stearate. 
Quantitative extraction of flock treated in accordance with the present 
invention, taken with observations of the hydrophobic nature of the 
finished flock, is evidence that the hydrophobic CH.sub.3 --ends of the 
acid molecules are exposed and the hydrophilic ends are attached to the 
flock. However, this hydrophobic property of the flock does not interfere 
with adhesion to water based adhesives when the flock is deposited onto a 
web. 
The amount of acid and/or salt deposited on the flock has not been 
determined precisely. However, it is estimated to be about 0.1% by weight 
based on chemical extractions of the flock. 
The present invention was the result of a series of experiments in which a 
wide variety of conventional yarn finishes were evaluated for possible 
usefulness in the treatment of flock. The finishes were applied to the 
flock using a high shear mixer and hot water as described above. Of the 
many tested, one finish (Lauravel SC Conc., Laurel Soap Mfg. Co., Inc., 
Philadelphia, Pa.) showed promise when applied in this way. It was 
analyzed and its various components were evaluated. It was found that 
certain long chain fatty acids in that finish were effective whereas other 
components were not. Further investigation revealed that the effectiveness 
of the acids was dependent on the presence of metal ions in the water used 
to apply the finish and the use of high shear mixing, apparently causing 
the ions to react with the acid. Consequently, metal salts of those acids 
were evaluated and found to be effective and an especially useful material 
for the process.