Note: Descriptions are shown in the official language in which they were submitted.
1 155608
escription o~f Invent on
Improvements in or relating to a method of dyeing
This invention relates to a method of dyeing and more particularly to
a method of dyeing textiles, in which various kinds of fibres are spatially
separated, for example pile fabrics such as velvet, plush or velours, although
, the invention also relates to the dyeing of webs in the fonm of carpets and the
i like. Such fabrics or webs frequently have a pile made of one kind of artificial
fibre and a back made of natural or artificial oe llulose fibre. Most velours for
use on furniture, for example, are now producedwith a polyacryl nitrile pile and
a cotton back.
There are differences between the types of dyes which are best for dye-
ing the individual kinds of fibres or which are the only ones that can be so used.
The follcwing dyes, for example, are used for frequently occurring fibre combina-
tions:
Fibres: Dyes:
Polyacryl nitrile/cotton Basic/substantive
Polyamide/cotton Acid/substantive
Metal complex/substantive
Polyester/cotton Dispersion/substantive.
Theoretically a textile containing various kinds of fibre can be dyedby first dyeing one kind of fibre in a first bath and then dyeing the other kind
in a second bath. This is expensive, however, and an attempt is usually made to
dye materials containing various fibres in a single bath containing the various
kinds of dyes required for the various fibres.
Even during the process of preparing the dyeing liquor, different dyes
may interfere with one another and thus become partly ineffective. It is esti-
mated that this may affect up to 30% of the dyes used.
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When a dye liquor which contains different dyes is applied to a textile
material, e.g. by complete immersion in a padding machine, since, of course, the
different dyes are dispersed throughout the liquor, each fibre conponent of the
textile receives some dye which is intended for dyeing the other component.
~ These dye CQmpOnents are entrained by the textile without being used and are sub-
; sequently washed out. The washing-out must be particularly thorough, especially
if one fibre component is cotton. Owing to its absorption capacity, cotton re-
tain dyes intended for the other fibre components but not capable of being fixed
on cotton. If these dye components remain on the fibres they adversely affect
the fastness of the colouring in the fabric or web. Consequently, the main prior
~: art method of completely impregnating the fabric results in heavy dye consumption
and high washing costs.
One important modern fibre cQmbination is polyacryl nitrile/cellulose,
from which most furniture plush is produced. Polyacryl nitrile is dyed with
basic dyes which are cationic whereas substantive dyes for cellulose are anionic.
Unless special precautions are taken, these two types of dye will precipitate if
they are mixed in a single liquor. Precipitation is l æ gely prevented by adding
suitable extra chemicals. At high concentrations of dye, e.g. of the kind re-
quired for dark colours, correspondingly large quantities of such extra chemicals
are needed. These increase the cost and they also impair the stability of the
liquor. The large amounts of extra chemicals must also be washed out, which
further increases the washing costs.
The aforementioned problems cannot at present be avoided in the case of
a textile comprising a mixed fibre, the components of which are uniformly distri-
buted in the textiles. The above described method, hcwever, has hitherto also
been used to dye fabrics or webs in which the various kinds of fibres are spati-
ally separated from one another, and the present invention seeks to provide an
improved method of dyeing such a fabric or web.
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According to this invention there is provided a method of dyeing a web
or textile containing v æ ious kinds of fibres which are substantially separated
fran one another and are respectively on the two sides of the web or textile
wherein a first dyeing fluid which is suitable for dyeing the fibres on one side
of the web or textile is applied in the form of a foam to said one side, and a
; second dyeing fluid which is suitable for dyeing fibres on the other side of the
web or textile is applied in the fo~n of a foam to said other side. The inven-
tion also relates to a web or textile when dyed by such a method.
The web may be a pile fabric in which the pile consists of one kind of
fibre and the back consists of another kind of fibre. The dyes may be such that
they are subsequently fixed by steaming.
Preferably a measured quantity of foam is applied to each side of the
web or textile.
It will be appreciated that the dyes are separated in the same manner
as the fibres in the textile, and thus each dye is applied only to that side of
the web or textile containing the kind of fibre for which the dye is intended.
Since each dye is applied in foam form, the applied dye liquid and consequently
the amount of dye can be exactly proportioned and the mobility of the dye fluid
is sufficiently reduced to prevent dye fluid introduced fran one side from
immediately pentrating through the entire fabric. In addition, the various dye
fluids are prevented from mixing inside the textile.
In the case, for example, of a plush with a polyacrylic pile, only
basic dye is applied to the pile, the amount being just sufficient to dye the
polyacrylic fibres, whereas the back remains substantially free fr~m this dye and
is only given the required quantity of a substantive dye.
m e dyes, therefore, do not interfere with one another and no dye is
removed without being used. m ere is no need for the said extra chemicals
especially adapted to the
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simultaneQus presen oe of a nu~ber of dyes.
m e result, therefore, is less oonsumption of dyes and special chemicals
lower washing costs and improved fastness to rubbing.
m e method of applying a dye liquor in foam form to a textile is
known per se from German Auslegeschrift 22 14 377 and United States Patent
; Specification 3,969,780.
In a preferred embodiment the foams and/or the dye fluids forming
them are driven from both sides into the textile material. m us the dye fluids
are used with maximum efficiency in that the individual dye fluids are intro-
duced from the side into the web or textile but penetrate to only a predetermin-
ed depth, so that the dyed regions do not overlap and there is no interference
between the dyes inside the material.
By way of example, the foam can be applied on both sides and driven
inwards by a devi oe described in applicant's co-pending Canadian patent appli-
cation no. 343,789 filed January 16, 1980, now Canadian patent no. 1,138,605.
A comparative test was made on an acrylic cotton fabric weighing 480g
per linear metre and coloured brcwn. When the material was dyed in a padding
machine, i.e. in which the liquor contained the dye components for both kinds
of fibre, the dyes and auxiliaries cost DM 0.45 per linear metre, whereas
when the dye was a foam and the liquor was separated, the cost was DM 0.39 per
metre. In addition there were the following advantages: Better fastness, shorLer
steaming times and less washing, which led to a saving energy, no thickening
of the fabric and an improved appearan oe for the fabric. As the dye was applied
as a foam there were no problems in applying the dye liquor. These advantages
also cont~ hute to redu oe the cost.
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