[0001] The present invention relates to a process of printing fabrics and to the printed
fabric products thus obtained.
[0002] Printing fabric is a process by which a colour is imparted to selected portions of
a textile fabric; there are known several different methods of printing fabric, such
as screen printing, rotation printing, jet printing; different dyes and pigments can
be applied to the fabric, such as reactive dyes, discharge dyes etcetera.
[0003] Fabric can be printed as a flat piece or as a finished (or almost finished) garment.
In fabric printing a minimum amount of fabric is required for printing a colour. Printing
a garment rather than printing a flat fabric, is preferred by the clothes producers
because it makes it possible to decide for the colour of printing to be done at the
last minute. However, printing a garment is much more difficult and more expensive
than printing a flat fabric piece.
[0004] Another problem with printing fabric is that in general the printed portions has
a new look that does not agree with the faded look of the rest of the garment.
[0005] It is an aim of the present invention to solve the above problems and to provide
a process of printing fabrics that is easy and not expensive and that could be used
to provide on the fabric, namely a cotton denim fabric, printed patterns of the required
colour in a short time.
[0006] The process should be useful in particular to provide printed patterns on a cotton
denim fabric with a faded, i.e. worn, look.
[0007] The above aim is reached by means of the present invention that provides a printing
method according to which a fabric is printed with a composition comprising 4-40%
by weight, preferably to 4 to 25% by weight of at least one strong base MOH, where
M is an alkali metal, water and a thickener, said composition being not suitable to
provide a color on said fabric, and treating the printed fabric with a dye that is
suitable to react with said base to provide a coloured printed area corresponding
to the area where the basic formulation was applied. The composition is free of amines
and of compounds having amino groups; preferably the composition is not coloured.
The colour is imparted at least to the area where the composition containing the base
MOH has been applied.
[0008] Strong bases are e.g. KOH, CsOH, NaOH, LiOH, RbOH; preferably M is Na or K. In the
following description reference will be made to Na and K; the combination of these
two metals with the other features of the invention is expressly disclosed with this
reference.
[0009] The dye is preferably in the form of a solution, e.g. an aqueous bath.
[0010] The printed fabric, not yet treated with the dye, is preferably dried before the
subsequent step of imparting a colour. Before the step of imparting a colour to the
fabric, the fabric printed with the non-coloured composition is heated to a temperature
of at least 90 °C. preferably in the range of 130°c to 220°C.
[0011] In the preferred embodiment, the fabric to be printed with the MOH formulation is
not yet coloured and the bath gives a colour both to the fabric and to the printed
area with different intensity. This makes it possible to obtain a worn look without
having to use the other standard methods or with a limited use to said methods. Any
type of textile fabric that is resistant to the basic composition of the invention
can be used. In the case of denim fabrics, suitable fabrics have a weight in the range
of 50-500 g/m
2.
[0012] The dye is provided in a known way in an aqueous dying bath and is selected from
dyes suitable to react with and be "fixed" on the printed areas of the fabric more
than on the remaining parts of the fabric. The concentration of the dye in the bath
is such as to avoid imparting an excessive colouring to the fabric and to allow to
show the difference in colouring of the printed areas and the remaining fabric. A
suitable concentration of the dye in the dyeing bath is 0,1% - 10% by weight on the
weight of the fabric.
[0013] Suitable dyes are reactive dyes, sulphur dyes, direct dyes and vat dyes.
[0014] An object of the invention is a composition according to claim 12. Said composition
comprises 4% to 40% by weight of at least one strong base MOH, where M is an alkali
metal, water and a thickener, has a viscosity suitable to be printed on fabric and
is free from amines and amino groups in general.
[0015] Preferably, the strong base is NaOH or KOH.
[0016] To prepare the NaOH and/or KOH composition, water, a concentrated solution of MOH
are mixed together, then a thickener is added to reach the viscosity required for
the printing step on a known printing machine. Suitable printing machines are rotary
screen and flatbed screen devices.
[0017] Suitable concentrated solutions of MOH for preparing the invention composition are
those having a concentration within the range of 8 to 48 Be (Baume degrees), preferably
35 to 45 Be, corresponding to ranges of 1 to 10 moles/litre and 5 to 8 moles/litre,
respectively.
[0018] In general, the amount of MOH solution in the composition is within the range of
30% to 70% by weight of the final composition. The amount of thickener is enough to
reach a viscosity suitable for the composition to be used on a printing machine for
textile printing; suitable viscosities are in the range of 5 to 40 dPa.s. Suitable
thickeners are thickeners for aqueous solutions that are resistant to highly basic
conditions such as in the invention composition. An example of suitable thickener
is anionic pregelatinized carboxymethylated starch which is able to resist to alkali
solutions.
[0019] The amount of MOH-containing composition applied to the fabric is within the range
of 50 to 500 g/m
2, preferably within 70 to 150 g/m
2. The fabric is generally a flat piece of fabric but it can also be in the form of
a part of a garment.
[0020] It is therefore a further object of the invention a fabric or garment as obtainable
through a process according to step a) of claim 1 and any depending claim, said fabric
or garment including an area comprising a composition of MOH and a thickener and that
is free from additional colours. It also is an object of the invention a printed fabric
or garment further comprising an additional colour derived from step b) of claim 1.
[0021] The invention has several advantages over the prior art. It makes it possible to
prepare a fabric with a pre-printed pattern and to subsequently decide what will be
the final colour to be imparted to the fabric/pre-printed area. Another advantage
is that by avoiding the use of amines and molecules having amino groups in general,
the final printed coloured area will have a worn look as the rest of the fabric.
[0022] The invention will now be further described with reference to the following non-limiting
example.
EXAMPLE 1
Preparation of a base composition.
[0023] 528 g of an NaOH concentrated solution having 38 Be were added to 444,5 g H
2O and mixed with 27,5 g of anionic pregelatinized carboxymethylated starch as a thickener.
The composition was thoroughly stirred and a viscosity of 30 dPa.s(decipascal-seconds)
was reached.
EXAMPLE 2
Printing of a fabric.
[0024] A denim fabric of about 200 g/m
2 was screen printed with a composition according to example 1. The printed fabric
shows no difference in the colours of the printed area and of the non-printed area.
[0025] The fabric was dried at 145°C for 1 minute.
[0026] The dry fabric was immersed in a bath containing the following compounds:
Dye: solution A colour beige, 20 ml.
Water up to 1 It.
Dye solution A is obtained by combining the following dyes:
8,4 g solar brun RLNI
5,8 g indosol yellow SFGL
[0027] The dry fabric is dyed in a bath containing 20 ml of the prepared dye solution A
per litre of water at 60°C for 20 minutes.
[0028] The treated fabric was then removed from the bath and dried. The area previously
printed with the basic composition of example 1 is coloured in dark beige while the
remaining fabric is light in colour.
1. A method for printing a fabric,
characterized in comprising the following steps:
a) applying to selected areas of a fabric a composition comprising 4% to 40% by weight
of at least one strong base MOH, where M is an alkali metal, water and a thickener;
and
b) treating the printed fabric with a dye that is suitable to react with said base
to impart a colour on said fabric area where said composition was applied.
2. A method according to claim 1, wherein M is Na or K.
3. A method according to claims 1 or 2, wherein said printed fabric is dried before said
step of imparting a colour.
4. A method according to any previous claim, wherein said printed fabric is heated to
a temperature of at least 90°C, preferably in the range of 130°C to 220°C before said
step of imparting a colour.
5. A method according to any previous claim, wherein said dye is provided in a bath and
is selected from reactive, sulphur, direct and vat dyes.
6. A method according to any previous claim, wherein said base composition is obtained
from a solution of NaOH having a concentration within the range of 8 to 48 Be, preferably
35 to 45 Be.
7. A method according to claim 6, wherein the amount of MOH solution is within the range
of 30% to 70% by weight of the final composition.
8. A method according to any previous claim, wherein the amount of said MOH-containing
composition applied to said fabric is within the range of 30 to 500 g/m2, preferably within 40 to 250 g/m2.
9. A method according to any previous claim, wherein said fabric is part of a garment.
10. A fabric or garment as obtainable through a process according to step a) of claim
1 and any depending claim, said fabric or garment including an area comprising a composition
of MOH and a thickener and that is free from additional colours with respect to the
remaining fabric.
11. A printed fabric or garment according to claim 10, further comprising an additional
colour derived from step b) of claim 1.
12. A composition comprising 4% to 40% by weight of at least one strong base MOH, where
M is an alkali metal, water and a thickener, said composition having a viscosity suitable
to be printed on a fabric.
13. A composition according to claim 12, wherein M is Na or K.
14. A composition according to claim 12 or 13, wherein said thickener is selected from
anionic carboxymethylated starches.