Process for treating textile fibers

A process for continuously dyeing or chemically treating textile staple length fibers having thermoplastic properties while conveying the fibers in a desired path of travel wherein the fibers are impregnated by passage through a liquid dye or chemical applicator and subsequently compressed and advanced in compressed form into and through a confined heating zone for reaction of the dye or chemical with the fibers, and wherein the fibers are preheated prior to their compaction at a temperature below their second order transition point but above the reaction temperature of the dye or other chemical applied thereto to compact and reduce the bulk of the same before their compression and delivery into the confined heating zone.

The present invention relates to an improved process for treating textile 
fibers and, more particularly, to an improved process for the continuous 
uniform dyeing or other chemical treatment of synthetic fibrous materials 
having thermoplastic characteristics. 
BACKGROUND OF THE INVENTION 
It is known to continuously dye textile fibrous materials, such as loose 
staple fibers, by impregnating the fibers with a liquid dye or other 
chemical, and thereafter continuously passing the fibers through a 
confined high frequency energy heating zone to react and fix the dye or 
other chemical on the fibers. As used herein, the terms "liquid dye or 
other chemical" means any dye or other chemical which is in a liquid 
medium form when applied to the textile fibrous materials. 
U.S. Pat. No. 4,104,019 discloses process and apparatus for the fixation of 
dyes or other chemicals onto textile fibers by continuously passing the 
same through a confined radio frequency energy heating tube. The fibers 
are compressed and compacted in the confined heating tube to form a 
partially self-sealing pressure chamber whereby generation of steam from 
the wetted fibers accelerates the reaction of the dye on the fibers. A 
copending commonly assigned Beucus U.S. patent application Ser. No. 
390,207 discloses method and apparatus for continuously dyeing textile 
fibrous materials using radio frequency energy to react the dye on the 
fibers, as referred to in U.S. Pat. No. 4,104,019. Said copending 
application relates to an improvement wherein the loose fibrous materials 
may be dyed at a greater rate of production by intermittent batch-wise 
delivery to a compression chamber and ram assembly which introduces the 
dye-wetted fibers under compression into the confined heating tube. 
In such continuous treatment of textile fibrous materials by compressed 
passage through a confined radio-frequency energy heating tube, it has 
been found that loose masses of certain synthetic staple fibers having 
thermoplastic properties, in particular acrylic fibers, are quite bulky 
and have such a high loft and volume that they are difficult to 
effectively compact and compress at a high rate of production. In 
particular, even with the intermittent delivery of acrylic fibers into a 
compression chamber as described in the aforesaid copending U.S. patent 
application, the apparatus can effectively handle only up to about 500 
pounds of dry weight acrylic fiber per hour. For greater economy of 
production, it is of course desirable to further increase the capacity of 
the apparatus for handling and dyeing or otherwise chemically treating 
textile fibrous materials. 
It has also been found that in the continuous high speed dyeing of loose 
textile fibers, in particular, synthetic fibers utilizing the high 
frequency heating apparatus described in U.S. Pat. No. 4,104,019, problems 
can also occur in obtaining uniform distribution and fixation of the dye 
color in the compressed fibrous mass. Such is believed due to non-uniform 
packing of the fibrous mass in the confined heating tube which produces 
density variations in the mass. In particular, if the packing density 
varies across or along the length of the mass of fibers in the tube, the 
concentration of the liquid phase which constitutes the lossy material in 
the heating tube will also vary, causing corresponding temperature 
variations in the mass being heated by radio frequency energy. Such 
temperature variations accordingly produce differential dye reactivity and 
color shade variations in the fibers. 
BRIEF OBJECTS OF THE INVENTION 
It is therefore an object of the present invention to provide an improved 
process for the continuous dyeing or other chemical treatment of textile 
fibrous materials having thermoplastic characteristics, wherein the 
materials may be effectively treated more unformly and rapidly with use of 
high frequency energy than heretofore obtained. 
It is another object to provide an improved process for the continuous 
dyeing of textile fibrous materials, in particular acrylic fibers, 
utilizing radio frequency energy to react the dye with the fibrous 
materials while in compressed confined condition. 
It is a further object to provide an improved process for the continuous 
dyeing of textile fibrous materials with fixation of the dyes on the 
materials while the fibers are transported through a confined heating zone 
under pressure, whereby more uniform packing of the fibers contributes to 
uniform and consistent dye shade development of the same during dye 
fixation. 
It is a further object of the present invention to provide an improved 
process for continuous dyeing or other chemical treatment of loose fibrous 
materials, with high-frequency heat energy fixation of the dye on the 
fibers while under compression, and wherein the compressed fibers may be 
more uniformly compressed and packed into a confined heating zone, 
permitting higher pressure build-up in the zone of vaporized liquids and 
higher temperatures with lower energy input during the heat treating stage 
.

BRIEF SUMMARY OF THE INVENTION 
The present invention is directed to an improved process for continuous 
treatment of loose textile fibrous materials having thermoplastic 
properties wherein the fibers are impregnated with a liquid dye or other 
chemical to a desired wet pick-up, and thereafter transported in 
continuous mass or bulk form to be heated in a confined tube by the use of 
radio frequency energy, while maintaining the fibers under a desired 
degree of compression during their passage through the tube. More 
particularly, the rate of treatment of such fibrous materials on such 
equipment can be greatly increased by preheating the bulk fibrous 
materials prior to their physical compression and forced passage through 
the heating tube. The preheating of the fibrous materials, preferably with 
preliminary pressure applied temporarily thereto, causes a pre-compaction 
and reduction in overall bulk of the fibers, whereby they can be delivered 
at a greater rate through the heating tube, and whereby the density of the 
mass of compressed fibers passing through the tube may be more uniformly 
controlled. 
Preheating of the thermoplastic fibers is carried out at a temperature 
below the second order transition point of the fiber, and below the 
reaction temperature at which dye or other chemical applied to the fibers 
would begin to fix or react with the fibers. By pre-compaction of the 
fibrous materials before dye fixation, the fibrous materials may be 
compressed more compactly and uniformly through the confined heating tube 
for reaction to ensure more uniform treatment of the same. 
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The process of the present invention may be effectively carried out on a 
continuous textile fibrous material dyeing range, the major component 
parts of which are schematically illustrated in FIG. 1 and are described 
in detail in aforesaid copending Beucus U.S. patent application Ser. No. 
390,207, filed June 21, 1982. The disclosure of said application is 
included herein by reference. 
Referring more specifically to the drawings, FIG. 1 shows improved 
apparatus of the present invention for the continuous dyeing or otherwise 
chemically treating textile fibrous material. Basically, the continuous 
treatment range includes a fibrous material supply section 10, a dye or 
chemical applicator section 12, a fibrous material compression section 14, 
a high frequency energy heating tube section 16, and a washing section 20. 
Textile fibrous material, typically in the form of loose staple length 
fibers, is pneumatically conveyed by way of a delivery tube 22 from a 
suitable supply source, such as conventional textile opening and weigh pan 
blending equipment (not shown), into a fiber condenser unit 24 containing 
a rotating filter drum 26. The interior of the drum is connected to a 
vacuum source, such as a motorized fan (not shown), such that a condensed 
fibrous web 28 accumulates on the filter drum outer surface. The drum 
continuously rotates in the direction indicated by the arrow to discharge 
a cohesive web of fibers by way of a pressure roller 26a and bladed 
stripping roller 26b, onto a moving belt conveyor 30 which continuously 
delivers the web to an inclined chute conveyor 32. Details of the fiber 
condenser unit 24 and its cooperative use in the continuous treatment 
range form the subject matter of a different invention contained in a 
commonly assigned copending U.S. patent application Ser. No. 390,202, 
filed June 21, 1982. 
The lower outlet end 32a of chute 32 is disposed immediately adjacent the 
nip of a pair of mangle rollers 34, 35 of a padding unit of the liquid dye 
or chemical applicator section 12. The amount of fiber supplied to the 
treating range is controlled by varying the rate of delivery of fiber to 
condenser unit 14 of the range, and suitable motor means, e.g., DC drive 
motors, (not shown) are operatively connected in conventional manner to 
positively drive the various conveyors and rollers for delivery of fibers 
through the treating range. 
The padding unit of section 12, details of which are known in the art, 
includes a driven endless belt 36, the central portion of the upper reach 
of which is downwardly deflected by rollers 38 to form a depression, or 
well, for retaining a treating liquid, such as a liquid dye composition. 
Belt 36 is entrained about the lower mangle roller 35 and moves to convey 
and transfer liquid dye into the fiber web as it is delivered from the end 
of chute 32 into the nip of the mangle rollers. Pressure is applied in 
conventional manner (not shown) to the mangle rollers to express liquid 
dye from the fibers and obtain a desired amount of wet dye pickup in the 
fibers. The dye-impregnated fibers are removed from the surface of the 
mangle rollers by rubber-bladed scraper rollers 40 and are deposited in 
broken apart, smaller masses of fiber onto a continuously moving conveyor 
41. 
The wetted loose fibrous material containing a desired amount of dye liquid 
is continuously gravitationally delivered by conveyor 41 into the upper 
end of a fiber-receiving hopper 42 of fiber compression section 16. The 
upper portion of hopper 42 is provided with a pair of fiber collecting 
plates 44 which are pivotally mounted in overlapping relation for 
collecting and periodically depositing accumulated fibers into a lower 
compression chamber 46 of hopper 42. The compression head 48a of a 
double-acting hydraulic ram assembly 48 moves through the compression 
chamber in a generally horizontal direction to compress the fibrous 
material received in the chamber and push the same into the inlet of an 
elongate confined radio-frequency energy heating tube 50. A plurality of 
hydraulic piston-actuated, fiber-retaining pins 52 are arcuately disposed 
about the inlet of heating tube 50 and are arranged and operated to move 
radially into the fiber passageway to retain compressed fiber in the 
heating tube 50 against backward movement into the compression chamber 46 
each time ram head 48a is retracted for the beginning of another 
compression stroke. 
Details of the operation of the fiber-collecting plates in the upper end of 
the hopper, and their movement to deposit fibers collected thereon into 
the compression chamber in response to the absence of the ram compression 
head therein from the subject matter of a different invention contained in 
a commonly assigned copending Beucus U.S. patent application Ser. No. 
390,207, filed June 21, 1982. The disclosure of said application is 
incorporated herein by reference. 
The fibers passing through the tube are heated by conventional RF energy 
generating equipment, which includes an H.T. transformer, rectifier, tube 
oscillator, and tank circuit adjustable to give a radio frequency of 27.12 
megahertz. The generating equipment, details of which are known in the art 
and are not shown in FIG. 1, are located in an insulated protective 
housing 56. The RF energy imparted to the dye-impregnated, compacted 
fibers in tube 50 raises the temperature in the fibrous material to a 
desired degree to set and/or otherwise fix the dye on the fibers, as by 
ionic bonding of the dye molecules to the fiber molecules. 
As best seen in FIG. 1, the exit end of the heating tube 50 has a 
downwardly disposed fiber outlet 54 for discharging fibers onto a moving 
conveyor 55. Disposed in the exit end portion of heating tube 50 to 
control periodic discharge of compressed fiber mass sections from the tube 
outlet is a pneumatic piston 57 with pressure head 58 and a plurality of 
pneumatic piston-actuated, fiber-retaining pins 60. Pistons of the 
pressure head 58 and retaining pins 60 are of the double-acting type and 
connected through conventional control valves, pressure regulator, and 
supply lines to a source of pressurized air (not shown). The exit piston 
pressure head 58 is arranged to move horizontally through the end portion 
of the heating tube over outlet 54, and located in its path of travel are 
three switches 62, 63, 64 which are connected to actuate the pneumatic 
control valves and supply pressurized air to the exit piston and pin 
pistons in the following sequence. 
Compressed fiber mass sections 66 are periodically discharged from the 
heating tube in the following cycle. When the exit piston pressure head 58 
is fully extended into the exit end of the heating tube to close the tube 
passageway and contact switch 62, pressure regulated air is supplied to 
the exit piston 57 to maintain a constant counter pressure of the pressure 
head against the compressed fibers in the tube. Pressurized air is also 
supplied to the pistons of pins 60 to fully retract the pins from the 
heating tube passageway. As fiber pressure builds in the heating tube due 
to the compressing action of the main compression ram assembly 48, the 
exit piston pressure head 58 is pushed outwardly of the tube by the moving 
fiber mass, to the right as seen in FIG. 1, until it contacts switch 63. 
Switch 63 actuates the air control valves to supply pressurized air to the 
pistons of pins 60 to insert the pins into the heating tube passageway and 
thereby retain the fibers under compression in the tube upstream of the 
pin positions. Pressurized air is also supplied to the exit piston 57, 
after momentary time delay, to move the pressure head 58 quickly further 
outwardly of the exit end of the heating tube, thereby releasing the 
section of compacted fibers between the pins and pressure head which falls 
by gravity through the heating tube outlet 54 and onto the conveyor 55. 
When the pressure head 58 contacts switch 64, pressurized air is supplied 
to the exit piston 57 to return the pressure head back to its innermost 
position to contact switch 62 and close the tube outlet 54. Contact of the 
pressure head with switch 62 directs compressed air to again retract the 
fiber-retaining pins 60 from the heating tube passageway and establish a 
constant counter pressure of the pressure head 58 on the fibers for the 
beginning of another discharge cycle. 
Sections 66 of released fibrous material which gravitationally fall from 
exit outlet 54 of the tube are conveyed by suitable conveyor sections 
through washing section 20, after which they are dried and collected in 
suitable manner (not shown). 
It has been found that synthetic fibers having thermoplastic 
characteristics, such as acrylic and polyester fibers, have such high loft 
and volume in loose bulk form that it is difficult to process the same on 
the aforedescribed treating equipment at a high rate of production. In 
particular, the high loft and bulk of such loose fiber materials passing 
into the compression chamber of the hopper section of the apparatus of 
FIG. 1 tends to clog and jam the ram assembly and compression chamber at 
rates of delivery above a level of about 500-600 pounds of fiber delivery 
per hour. By means of the process of the present invention, i.e., 
controlled preheating of the synthetic fiber materials before their 
mechanical compression and compaction into the heating zone, the mass of 
fibers delivered to the compression chamber are precompacted and 
compressed, permitting a greater weight of fibers to be processed through 
the compression chamber for mechanical compaction in a given time period. 
To accomplish these ends, means are provided for controlled preheating of 
the fibrous materials to relax the fibers and reduce their mass bulk prior 
to their introduction into fiber compression hopper of the dye range. 
Preheating of the fibers preferably is accomplished by heating the dye 
liquid which impregnates the fibers in the dye pad applicator section, 
followed by pressure application of the nip rollers 34, 35 to express dye 
liquid therefrom. The fibers also may be preheated by provision of 
additional heating means located in the path of fiber movement to the 
hopper compression chamber, either before or after dye application. Such 
may take the form of infra-red heaters or steaming chambers through which 
the fibers pass. Preferably, the preheating is accomplished in a wet or 
high humidity environment to facilitate heat transfer into the fibers and 
provide lubricity for individual fiber movement in the mass. 
Preheating of the fibers must be maintained within a controlled temperature 
range, specifically at a temperature below their second order, or glass, 
transition point, and below the temperature at which any dye applied 
thereto will start to react or strike into the fibers. The preheating 
preferably should be accompanied or followed by a pressure applied to the 
preheated fibers to compact their bulk or volume, which correspondingly 
increases the bulk density of the same. Such increase in bulk or mass 
density with consequent reduction in loft is believed due to a general 
heat relaxation of the latent crimp or stresses imposed in the synthetic, 
thermoplastic fibers during their manufacturing operations. In any event, 
the preheating of the fibers greatly compacts the bulk and mass of the 
same without adversely affecting the properties thereof, and as such, the 
fibers may be introduced at a higher rate of mass delivery, i.e., weight, 
than the non-preheated fibers. 
In addition, pre-heat compression and compaction of the fibers before their 
mechanical compression and delivery through the heating tube provides for 
more uniform packing of the fibers during their passage through the 
heating tube. Due to the nature of high frequency heating of the fibers 
which relies on lossy materials, i.e., the aqueous medium of the dye, to 
create and transmit the heat to the fibrous material, the temperature 
gradient across as well as along the compacted longitudinal mass of the 
same in the heating tube can be made more uniform. By more uniformly 
heating the fibers in the heating tube, more uniform dye fixation can be 
obtained. 
The advantages of the process of the present invention may be better 
appreciated by the following examples illustrating the dyeing of synthetic 
fibers in loose form with and without preheating of the same before 
delivery into the compression chamber of the hopper. The examples are by 
way of illustration and not intended to limit the scope of the present 
invention. 
EXAMPLE 1 
Three denier acrylic 11/8 inch staple length fibers (Acrilan B-16 
manufactured by Monsanto Company), were continuously dyed on the dyeing 
range of FIG. 1 utilizing a cationic aqueous dye composition having the 
following components by weight: 
1% Seragum 5076 by Kemloid Corporation 
1/2% acetic acid 
0.72% Astrazon Yellow GRL, Mobay Chemical 
0.45% Sevron Red CDL, Crompton & Knowles 
0.37% Sevron Blue 5GMF, Crompton & Knowles 
The dye formulation, which has an afghan brown color, was continuously 
applied to the fibrous batt at the dye applicator section. Pressure on the 
mangle rollers was controlled to provide a wet pick up of the liquid dye 
composition on the fibers of about 100 to 125 percent. Masses of the 
fibers were directed to and gravitationally deposited into the compression 
chamber of the fiber receiving hopper where they were compressed by the 
compression ram through the confined heating tube which is maintained at 
an energy level to provide a temperature of around 230.degree. F. to fix 
and react the dye on the compressed fibers passing therethrough. Speed of 
delivery of the dye impregnated fibers to the hopper was increased during 
the dyeing operation up to a speed of approximately 560 pounds fiber per 
hour (as measured by dry weight of the fibers entering the dye pad 
applicator), above which point the fibrous material began to clog and jam 
the ram assembly preventing introduction of further fibrous materials into 
the heating tube. It was necessary to stop the operation of the dyeing 
equipment to reestablish continuous dyeing operation at a rate of fiber 
throughput of no more than around 500 pounds dry weight fiber per hour. 
EXAMPLE 2 
Acrylic fibrous materials as identified in Example 1 were continuously 
impregnated with the dye composition of Example 1 and delivered to the 
fiber-receiving hopper of the dye range; except that the temperature of 
the dye liquid was raised to 160.degree. F. 
The dye impregnated fibrous materials were compacted due to the heat and 
pressure before delivery to the hopper compression chamber. Speed of 
delivery of the fibers to the hopper compression chamber was increased up 
to a rate of 1,000 pounds per hour (dry weight) with no problems in 
handling of the fibers at the hopper compression chamber. 
FIG. 2 illustrates in graphic form the effect of preheating of synthetic 
staple fibers containing thermoplastic components to reduce their loft 
and/or bulk in loose mass form. FIG. 2 graphically illustrates by the 
lines 70 and 80, for three denier acrylic 11/8 inch staple fiber and three 
denier polyester 11/2 inch staple fiber, respectively, the effect of 
temperature of the fibers on their compression, expressed as a percent of 
the volume of corresponding fiber type wet with cold tap water at room 
temperature under equivalent pressure, as control. Multiple sample strips 
of sliver of the two fiber types having the same weight and length were 
wet out with water at different temperatures and passed through a nip 
roller apparatus to give 100% residual water content. The wetted slivers 
were each placed in a 500 CC graduated cylinder and compressed, utilizing 
a 100 gram weight for the acrylic fiber and a 500 gram weight for 
polyester fiber. The amount of compression at various temperatures was 
compared with correspondingly compressed wet out, room temperature samples 
of the respective fibers. 
As can be observed from the graph of FIG. 2, as the temperature of samples 
of the acrylic fiber is raised, they increasingly compact to reach a 
maximum of approximately 40 percent of their original wet bulk at room 
temperature when heated to a temperature of approximately 160.degree. F. 
Correspondingly, polyester staple fiber compacts to a point of 
approximately 44 percent of its bulk at a temperature of approximately 
160.degree. F. Thus, it can be seen that fibers containing thermoplastic 
properties, as illustrated by the acrylic and polyester staple fiber tests 
represented in the graph of FIG. 2, will compact or compress under 
conditions of temperature with optimum compression being obtained in a 
temperature pretreatment range of around 160.degree. F. for both types.