Note: Descriptions are shown in the official language in which they were submitted.
PROCESS ~O~ ~APID DYEING OF COMPOSITE SYNTHETIC SHEET
MATERIAL DESIGNED TO IMITATE NATURAL LEATHER
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The present invention relates to a process for
rapid dyeing of composite synthetic sheet material from
which to produce, via appropriate~chemical processing, a
product similar to natural leather. In particular, the
present invention applies to a~chemical process for pro-
cessing any known type of~synthetic (or "imitation")
leather, consisting of shaet material comprising a
porous (vesicular) polymer matrix embedded with natural
or synthetic fibers, and which provides for transforming
said synthetic leather into a product identical in
appearance and "feel" to natural leather, and as
described in Italian Patents n. 1.178.956 and 1.211.465
filed by the present Applicant.
The above Italian patentsj ~he content of which i5
included herein by way of reference as required, relate
to the chemical processing of sheet materials with a
vesicular matrix (i.e. having evenly distributed
micropores) incorporating or hot natural or synthetic
reinforcing fibers, for producing imitation leather
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closely resembling and even indistinguishable to the
naked eye from natural leather, by processing the raw
material normally used for producing SOFRINA (registered
trade mark) of KURARAY CO. LTD. The chemical process
also includes a dyeing stage, which consists of one or
more operations using azoic dyes (e.g. BASACRIL
registered trade mark) and ammonia, and, successively or
in a mixture, premetallized dyes or specific metal
compounds ~or the matrix fibers (e.g. NYLQN (registered
trade mark) fibers), such as aniline, ISOLAN, TELON,
LANACROM, ACIDOL (registered trade marks). The dyeing
stage is performed using both tanning technology, in
rotary drums, and textile technology, using JET or FLOW
type dyeing machines, the strips of sheet material for
processing being formed into bales in the first case,
and, in the second, being joined end to end into loops
which are fed on to the machines and recirculated.-
Whichever of the above methods is employed, thedyeing stage requires continuous, accurate metering of
the dye solution components, and a processing time of
several hours, thus resulting in relatively high proces-
sing cost. Moreover, and particularly in the case of
rotary drums, a continuous check cannot be kept on the
quality of the processed material, so that whole lots of
material may possibly be ruined in the event of
inaccurate dyeing parameters. Finally, numerous in-
process handling operations are required of the sheet
material, which, being in strip form, is normally in
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rolls which must be unrolled for forming the rnaterial
into bales or loops and subsequently reformed into
rolls.
It is an object of the present invention to
provide a process for dyeing sheet material of the
aforementioned type more rapidly and relatively cheaply,
and which at the same time provides for minimum in-
process handling of the material and continuous control
of the dyeing stage.
According to the present invention, there is
provided a process for dyeing composite synthetic sheet
materîal designed to imitate natural leather and
comprising a porous matrix, and a fiber reinforcement
selected from a group conslsting of non-woven fabric,
polyamide, polyethylene or polyester fibers, and
embedded in said matrix; characterized by the fact that
said synthetic material, in strlp form, is processed
chemically with dyeing substances over its entire
section consisting of said porous matrix and said
reinforcement, by feeding the strip of composite
material reciprocatingly and at a predetermined speed
inside a bath containing a solution and/or emulsion of
said dyeing substances, and by maintaining the strip
taut.
A non-limiting embodiment of the present invention
will be described by way of example with reference to
the accompanying drawing, which shows a schematic
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section of an apparatus for implementing the dyeing
process according to the present invention.
Extensive research and testing by the Applicant's
technicians has shown that, providing the strip is
subjected to a given amount of mechanical traction,
dyeing a strip of vesicular material by simply immersing
it in a bath of dye provides, for a given dye
solution/emulsion formula and other given physical-
chemical operating parameters, for drastically reducing
dyeinq time, even by as much as over 60~, as compared
with rotary drum andlor textile machine dyeing methods.
This translates into an average reduction in dyeing time
ranging ~rom several to a few hours (e.g. from 6 to
little less than 3 hours) with substantially no change
in the end result (colour quality and distribution over
the strip, life and stability), thus enabling a drastic
reduction in dyeing cost. Moreover, an immersion process
provides for more easily controlling the physical and
chemical parameters of the bath ttemperature,
concentration, pH, etc.) as well as for eliminating any
handling of the material for processing, which, being in
roll form, may simply be unwound into the bath and
subsequently rewound. What is more, at least part of the
material being processed is constantly out of contact
with the dye solution/emulsion, thus enabling it to be
quality checked.
The material for dyeing, which, to achieve the
above results, must necessarily comprise a porous matrix
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(and, preferably, a fiber reinforcement selected from a
group consisting of nonwoven fabric, polyamide,
polyethylene or polyester fibers embedded in the
matrix), is processed chemically in strip form, over its
entire section consisting of the porous matrix and
reinforcement (if any), with dyeing substances
containing appropriate (known) auxiliary additives, by
feeding the strip o~ v~sicular material reciprocatingly
~nd at a predetermined speed inside a bath containing a
solution and/or emulsion of said dyeing substances and
additives, and by maintaininy the strip taut. The
synthetic material in strip form is fed reciprocatingly
inside the bath by alternately winding and unwinding the
strip on and off two opposed rollers having means for
maintaining the strip at a predetermined tension and
guiding it through a tank located between the rollers
and containing the dye bath.
; More specifically, and as ~hown in the
accompanying drawing, a strip 1 of known microporous
(vesicular) synthetic sheet material, in particular made
of polyurethane with embedded polyamide fibers free to
move inside the porous matrix (e.g. the raw material for
producing SOFRINA - registered trade mark), is processed
in an apparatus 2 defined by a pressure casing 3 housing
a tank 4 and two opposed powered rollers 5, 6 at the
opposite longitudinal ends of tank 4. Tank 4 contains a
dye bath 7 of known composition, and, according to the
purely indicative example shown, a powered tensioning
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cylinder 10. Strip 1 is formed into a roll 11, which is
mounted on to roller 5, unwound off roller 5 into tank 4
and through bath 7, and rewound on to roller 6 from
which, by inverting the rotation direction of rollers 5
and 6, it may subsequently be unwound and fed through
tan~ 4 in the opposite direction, and rewound on to
roller 5, so as to feed strip 1 reciprocatingly inside
bath 7. By means of motors 12, tensioning cylinder lO
may be moved vertically inside tank 4 and bath 7, so as
to adjust as required the tension of strip 1 traveling
back and forth through bath 7 in tank 4. Apparatus 2
also presents means for controlling the temperature of
bath 7, e.g. a heatingJcooling coil 15; known sensor
means (not shown), such as a thermometer, pH meter and
level sensor; and supply means for bath 7, wash
solutions, and acid and base pH-correcting solutions,
all of known type and therefore not shown for the sake
of simplicity.
Preferably, operating pressure is above
atmospheric, and bath 7 is maintainèd at a temperature
of over 100C, by virtue of pressure apparatus ~, inside
which rollers 5 and 6 and tank 4 are housed, being
fluidtight and hence pressurizable; and tensioning
cylinder 10 is so positioned by motors 12 as to feed
strip 1 reciprocatingly through bath 7 at a tension of
no less than 30 Nw/s~.cm of cross section of strip 1.
Powered rollers 5 and 6 are so operated as to feed strip
1 reciprocatingly through bath 7 at an average linear
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speed of roughly 20 m/minute and, at any rate, ranging
from B to 40 m/minute. Operating with the above
parameters and traditional dye formulas, the dyeing sta-
ge, by immersing and feeding strip 1 reciprocatingly in
bath 7, takes from 30 minutes to 4 hours, at the end of
which, strip 1 is dyed evenly and stably, and presents
an excellent appearance.
The present invention will now be described
further by means of a number of practical examples.
EXAMPLE 1
Twelve strips of raw "SOFRINA" material of KURARAY
Co. LTD - Japan (a vesicular synthetic material
comprising a microporous polyurethane matrix embedded
with NYLON (registered trade mark) fibers, and a compact
polyurethane surface coating printed to imitate natural
leather), each 10 m long, 0.8 mm thick and weighing 182
kg, are divided into four lots of 3 strips each; and the
strips in the first two lots, A and B, are dyed using an
aqueous solution of 3% by weight of LEVADERM (registered
trade mark) as follows:
- The strips in lot A are folded and tied into bales
measuring cm 250 x 120 x 120, and are loaded into a
roughly 5.6 m3 rotary drum of the type used for tanning.
Into the drum, rotating at a speed of 15 rpm, are fed
300 liters of the above 3% aqueous solution in LEVADERM,
and the strips are treated with the solution for 65
minutes at 40C and 75 minutes at 60C, the temperature
being adjusted slowly, for a total of roughly 6 hours.
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After being washed with 650 liters of water, the bales
are taken out, the strips rewound, and the colour
checked.
- The strips in lot B, wound into a roll, are treated on
a JEGGER processing machine corresponding to the machine
shown schematically in the accompanying drawing. Each
roll is mounted on to a powered roller from which it is
unwound on to a second roller, opposite the first, and
vice versa, so as to feed the strip reciprocatingly
inside a tank between the rollers and containing 60
liters of the above 3% LEVADERM solution. The strip is
held between the rollers at a tension of 40 Nw/sq.cm and
is f~d through the tank containing the solution at a
speed oE 30 m/minute. Ambient pressure is applied, and a
temperature of 40C maintained for 30 minutes, after
which, the temperature is gradually raised to 940c for
2.5 h. At the end of the operation, the strips, still in
roll form, are colour checked.
- The strips in lots C and D are tied into bales as for
lot A, and are treated in a 5.5 m3 drum rotating at a
speed of 15 rpm, first with 300 liters of an aqueous
solution of surface-ac~ive agents at 60~c for 20
minutes, then with 300 liters of an aqueous solution of
30% by weight of chromium sulphate at 60C and with a pH
of 3.2. After 40 minutes, the pH is raised to 7.1 by
adding NaOH lON and precipitating the hydroxide with
abundant coagulation. After rinsing, the drum is fed
with 300 liters of an aqueous solution of 6% by weight
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of aspartic aldehyde for 40 minutes, followed by 300
liters of a 30% solution by weight of sulphited fatty
esters (sulphited whale oil - "sperm oil") for 45
minutes. The strips in lot C are then dyed in a rotary
drum as for lot A, and those in lot D are formed into a
roll and dyed as for lot B.
When compared, the strips in lots A and C present
the same colour and uniform shading as those in lots B
and D: the dyeing operation of lots A and C, however,
required roughly 6 hours as compared with only 3 hours
for lots ~ and D.
EXAMPLE 2
Twelve strips as in Example 1 are divided into two
lots E and F of 6 strips each. The strips, unrolled and
stitched into a loop, are txeated on a JET type dyeing
machine using the same solutions and operating
parameters as lots C and D, except that, following
precipitation with chromium sulphate and before being
treated with glutaric aldehyde solution, they are
treated with 650 liters of an aqueous emulsion of 7% by
weight of APRITAN PQ (registered trade mark), a known
maleic styrene filler used in tanning, and 2% by weight
of BASITAN MN (registered trade mark) and 3% by weight
of TANIGAN PAX (registered trade mark), known
synthetic-tannin-based retanning agents used in the
tanning industry. The strips in lot E are then dyed on
the JET machine by treating them with 650 liters of an
aqueous solution of 3% by weight of LEVADERM (registered
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trade mark), a known polyurethane dye, and 3% by weight
of SELLASET (registered trade mark), a specific known
dye for polyamide fibers, for 4 hours at 98~C. The
strips in lot F, on the other hand, are removed from the
JET machine, formed into a roll, after first unstitching
the loop, and treated with an identical dye solution (3%
by weight of LEVADERM and 3% by weight of SELLASET) for
2 h at s8C and atmospheric pressure using a JEGGER
: machine and the same parameters as for lots B and D. In
this case also, when compared, lots E and F presented
the same colour alongside a marked difference in the
duration of the dyeing stage.
~: EXAMPLE 3
wenty-four strips of the same material as in
Example 1, but with the compact polyurethane surface
coating removed mechanically by means of a blade (and
thus consisting solely of the microporous matrix and
fiber reinforcement), are divided into two lots (1 and
2) of 12 strips each, and treated on a JE~ type machine
: with 500 liters of an aqueous solution of 3% aniline and
5% 24Bé ammonia (weight percentages calculated according
to the weight of the strips) for 90 minutes. After
washing in water, the strips are then dyed using the
following formulas:
The strips in lot 1 are dyed on the JET machine as
follows:
l.a) - Three strips are treated at 95C for 120 minutes
with a dye solution concisting of a water mixture of
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TELON A~3RL, ISOLAN K-3GLS and TELON FRL (registered
trade marks) in respective proportions oP 1.6%, 0.2% and
0.3~ o the weight of the strips.
i.b) - Three strips are treated at 30C for 15 minutes
with a dye solution comprising 300% by strip weight of
water, and 1% by strip weight of ABEGAL SW (registered
trade mark). The temperature is then raised to 110C in
90 minutes, 5% by strip weight of premetallized dyes
(LANACROM and IRGALAN - registered trade marks) are
added, and the strips treated for a further 60 minutes.
l.c) -- Three strips are treated for 90 minutes, and by
raising the tempera~ure from 30 to 96C, with a dye
solution comprising, by strip weight, 300% water, 3~
AVOLAN IW (registered trade mark), 10% AS~RAGAL
(registered trade mark) and 5% ISOLAN K-PRL (grey).
After washing, the treatment i5 repeated twice for 50
and 90 minutes respectively, to eliminate the AVOLAN and
reduce the ISOLAN to 2~ and the ASTRAGAL to 4%.
l.d) - Three strips are treated at 30C for 60 minutes
with a dye solution comprising, by strip weight, 200~
water and 30% organic pigments (IRGAFIN - registered
trade mark). Acetic acid is then added to bring the pH
to 3.5, the temperature is raised to 80C, 2% of TELON
and 10% of ASTRAGAL are added, and the kempera~ure is
raised to 110C for 90 minutes. At this point, the tem-
perature is lowered to 60C, and a further dyeing
operation is performed by raising the temperature to
110C in 60 minutes.
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The strips in lot 2 are dyed using the same solutions
and compo~itions, but on a JEGGER machine and with the
same operating parameters as in Example 1, except that
the speed of the strip through the tank ranges from 8 to
m/minute, and the strip tension from 30 to 38
Nw/sq.cm, with the following dye solution in the tank:
2.a) - Three strips are treated with the solution as per
point l.a) maintained in the tank at 95C for 1 h.
2.b) - Three strips are treated with the complete
solution as per point l.b) (ABEGAL + LANACROM + IRGALAN)
maintained in the tank at 110C for 1.5 h, and 1.5 bar
pressure.
2.c) - Three strips are treated only once with the com-
plete solution as per point l.c) (AV3LAN 3~, ISOLAN 10~,
ASTRAGAL 5%) at 110C and 1.6 bar pressure for 1.5 h.
2.d) - Three strips are treated with the complete
solution as per point l.d) (IR~AFIN 30%, TELON 2%,
ASTRAGAL 10%) at 110C and 1.5 bar pressure for a total
of 2.5 h, acetic acid being added after 30 minutes'
treatment to vary the p~ and precipitate the pigments.
Samples taken from the strips in each lot were
then subjected to dry comparative colour inspection
using a spectrophotometer, after first being treated
with synthetic perspiration, alcohol, water, and
prolonged exposure to sunlight (BL~E scale evaluation).
The results were substantially identical for the three-
strip groups in each lot treated with the same dye bath.
The lot 2 samples, however, treated by tensioning the
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strip to less than 32 Nw/sq.cm as it is fed through the
dye bath, presented a lighter and, above all, less
evenly distributed colour as compared with the
corresponding s.amples in lot 1.
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