Hi Sartaj,
The main colouring matters used in the paper trade are synthetic organic dyes and pigments, but a number of inorganic pigments can be used e.g. iron oxide, prussian blue etc. the synthetic organic dyes are members of the basic, acid or direct dye classes.
Basic dyes: have very low affinity for bleached pulps, show a tendency to "mottle" i.e selectiving dyeng of certain fibres in the furnish; basic dyes precipitate both acid and direct dyes and therefore should not be mixed; light fasteness of basic dyes is poor but reasonably good water fastness.
Acid dyes: no affinity for cellulose fibres, must be fixed on fibre using fixing agents e.g. alum, rosin-alum size;tendency to two sidedness on drying, fastness is generally better than basic dyes.
Direct dyes(substantive dyes): excellent affinity for cellulosic fibres and light fastness is generally good.
Pigments: do not combine with the fibres but are deposited on the fibre and their retention depends on various physical phenomenon such as adsorption,occlusion, flocculation and filtration. pigments added in water carry a slight negative charge and repels fibres which also carry a negative charge. The charge id=s reversed by adding aluminium ions nad the pigment particles are adsorbed onto the fibre; excellent fastness to light, water, alkali and acid.
Preparation of a coloured sheet. using a standard laboratory method using direct dyes
Measure 330ml of pulp (3%) into a wax coted cup.
Add 0.5% Alum
Stir to mix
Add the requiste amount of dyestuff solution
Stir with high speed stirrer
Allow to dye for 10 minutes
Add 2% rosin
Allow to stand for 2 minutes
Add 3.5% Alum
Stir to mix
Dilute pulp in the vat to 2litres to give the stuff a consistency of 0.5%
Prepare a wet sheet using a hand mould and deckle
Press between wet felts to remove excess water
Dry slowly
NB. Dyeing of wool is different using metal complex dyes in an acidic media, the isoelectric point for wool is pH 4-5.
Hoping this will help you
thank you Joseph sir for this information as u hv mentioned the dyeing of paper ,can you provide me any reference of this, that will be more helpful
thank you............
Unfortunately, i am unable to give reference as the material i have was a training course on paper making, dyeing, finishing and aftertreatment CIBA CLAYTON LIMITED, This document is not in any softcopy but hardcopy. I will be looking for any references to submit to you. Thanks
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Polymers