In pigment printing, insoluble pigments, which have no affinity for the fibre, are fixed
on to the textile with binding agents in the pattern required. This description is
perhaps oversimplified, but it does obviously set pigments apart from dyes that are
absorbed into the fibre and fixed there as a result of reactions specific to the dye.
The economic importance of pigments in printing is substantial: since around 1960
these have become the largest colorant group for textile prints.
More than 50% of all textile prints are printed by this method, mainly because it is the cheapest and simplest printing method. After drying and fixation, these prints meet the requirements of the market. The washing process, carried out on classical prints to remove unfixed dye, thickening agents and auxiliaries, is not normally necessary when using the pigment printing technique. For more than 3000 years, mineral pigments have been ground with natural binding agents (drying and boiled oils, or viscous, aqueous solutions of albumen products and vegetable gums) and ‘applied’ to the textile to form a pattern.
Even though pigment printing is the oldest printing method, it was unimportant until the Second World War because of the poor results of the technique: dull colours, loss of textile character as a result of hardening, and poor fastness to wear and washing. The basic products for modern pigment printing were available quite early, but the techniques required development. In the 1920s dispersions of useful organic pigments like those found in pigment printing today were available on the market; Hansa Yellow pigment pastes were an example. In the 1930s emulsion copolymerisation of olefinic substances (such as butadiene, vinyl esters, acrylonitrile and acrylic acid esters) was discovered at the former IG Farben in Leverkusen and Ludwigshafen. These were integral steps in the development of modern pigment printing. Another important step was the introduction of emulsions as printing paste thickeners.
In 1937 the first pigment printing pastes based on water-in-oil (w/o) emulsions were developed in the USA by Interchemical Corporation. In the following years these emulsions were often used on the American continent – even as late as the 1960s – for cheap staple goods with modest fastness requirements. These water-in-oil emulsion pigment pastes were not accepted by the European market, where fastness properties were of more importance. In Europe aqueous pigment systems, for use in oil-in-water emulsions, were developed. The o/w emulsions ultimately drove out the w/o emulsion-based systems, even in the USA [1,2].
Eventually, synthetic thickeners became available. A good-quality pigment print is characterised by: – brilliance and high colour value relative to the pigment concentration in the paste – minimum stiffening in the handle of the textile – generally acceptable fastness properties. The currently available ISO-approved methods for fastness testing and evaluation of prints do not take into account the mechanical effect on pigmented binder films during washing, and do not adequately reproduce the mechanical action of washing in a household machine. In practice, additional tests have proved successful in judging fastness properties, tests of resistance to scrubbing under defined conditions being particularly important.
Successful pigment printing systems are based upon three equally important components: – pigment dispersions – binders and crosslinking agents – thickeners and auxiliary agents giving the required rheology.
More than 50% of all textile prints are printed by this method, mainly because it is the cheapest and simplest printing method. After drying and fixation, these prints meet the requirements of the market. The washing process, carried out on classical prints to remove unfixed dye, thickening agents and auxiliaries, is not normally necessary when using the pigment printing technique. For more than 3000 years, mineral pigments have been ground with natural binding agents (drying and boiled oils, or viscous, aqueous solutions of albumen products and vegetable gums) and ‘applied’ to the textile to form a pattern.
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| PIGMENT PRINTING |
Even though pigment printing is the oldest printing method, it was unimportant until the Second World War because of the poor results of the technique: dull colours, loss of textile character as a result of hardening, and poor fastness to wear and washing. The basic products for modern pigment printing were available quite early, but the techniques required development. In the 1920s dispersions of useful organic pigments like those found in pigment printing today were available on the market; Hansa Yellow pigment pastes were an example. In the 1930s emulsion copolymerisation of olefinic substances (such as butadiene, vinyl esters, acrylonitrile and acrylic acid esters) was discovered at the former IG Farben in Leverkusen and Ludwigshafen. These were integral steps in the development of modern pigment printing. Another important step was the introduction of emulsions as printing paste thickeners.
In 1937 the first pigment printing pastes based on water-in-oil (w/o) emulsions were developed in the USA by Interchemical Corporation. In the following years these emulsions were often used on the American continent – even as late as the 1960s – for cheap staple goods with modest fastness requirements. These water-in-oil emulsion pigment pastes were not accepted by the European market, where fastness properties were of more importance. In Europe aqueous pigment systems, for use in oil-in-water emulsions, were developed. The o/w emulsions ultimately drove out the w/o emulsion-based systems, even in the USA [1,2].
Eventually, synthetic thickeners became available. A good-quality pigment print is characterised by: – brilliance and high colour value relative to the pigment concentration in the paste – minimum stiffening in the handle of the textile – generally acceptable fastness properties. The currently available ISO-approved methods for fastness testing and evaluation of prints do not take into account the mechanical effect on pigmented binder films during washing, and do not adequately reproduce the mechanical action of washing in a household machine. In practice, additional tests have proved successful in judging fastness properties, tests of resistance to scrubbing under defined conditions being particularly important.
Successful pigment printing systems are based upon three equally important components: – pigment dispersions – binders and crosslinking agents – thickeners and auxiliary agents giving the required rheology.
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