binders in textile printing

7/27/2019 Binders in Textile Printing

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BINDERS IN TEXTILE PRINTINGBy

Akshay Yuvraj Bhagat

(2009TT10782)

Introduction

Pigment particles are molecular aggregates which do not have any group capable of reacting

with fibre or substrate. Due to this lack of functionality and size, pigment particles are

required to bond to the substrate by use of high molecular weight film forming substance

called binder. The binder forms a film when dried which encloses pigment and adheres to

fabric. Binder is the only linkage between fabric and the pigment.

Binders are organic polymer products used for the fixation of pigment prints/dyeing and as

adhesive bonding agents like resins to provide structural integrity to web of nonwovens.

They are mainly solid plastic products like thermoplast powders, plastic solution anddispersions.

The use of pigment binder is very essential in producing pigment coloured fabric in textile

industry. The colour fastness is adequate for majority of the cases for the end use but

printing is accompanied by degradation in hand feel. The coloured fabric is slightly harsher

than the non-coloured one. With proper selection of binders and application method and

variables it is possible to produce acceptable effects after printing. Not only hand feel is

vital, but retention of colour on substrate i.e. durability is also important. Other important

factors are elastic resilience, flexibility, absorbency, dry-cleaning fastness, etc.

Water based synthetic acrylic, vinyl acrylic and styrene butadiene co-polymers are principal

binders for pigment printing. An important requirement for these binders is the balance

between adhesion and cohesion. Binders for textile pigment printing contain self

crosslinking free methylol groups which are protected against premature crosslinking

through esterification.

Colouration to textile can be done in various ways like padding, printing or by exhausting

the colour onto the fabric. In each case there are three major components required for

colouration to be reasonably permanent. For padding it is water, pigment and binder; for

printing thickener, pigment and binder and in garment dyeing it is water, pigment and


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binder with assistance of pretreat. In all binder is an integral part of textile colouration and

have influence on the properties of the end product.

Chemistry of Binders

Binders are made using polymer latexes which are made from certain monomers. This

monomers give certain properties to final polymers. Polymers used in pigment printing are

made by a process called emulsion polymerization. Emulsion polymerization is a process in

polymerization of monomer which are emulsified with the help of an emulsifier in the

dispersion medium like water.

Monomer properties

The choices of polymer have significant effect on the properties of the dyed and printed

fabric, so polymer composition is critical for binder performance and selection. Butadiene,

acrylates, vinyl acetate, styrene and acrylonitrile are primary monomers used to design

textile binder. Functional monomers are often added to enhance binder properties. Binders

are high molecular weight products i.e. long chain organic compounds. The softness of

binder film is directly related to respected glass transition temperature. A soft film at room

temperature has low glass transition temperature.

Copolymers are produced from this monomers with best possible compromise.


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1,3 butadiene produces a very soft homopolymer, so it wouldn t be sticky enough to be an

acceptable binder. Therefore, to be effective monomer it must be polymerized with stiffer

monomer. It has two double bonds so when it polymerizes one double bond is left which

gives it elastic property and good dimensional recovery. This double bond is also susceptible

to oxidation which may cause discolouration.

Acrylates are thermoplastic which means they have poor dimensional recovery and hence

have reduced abrasion resistance. Common acrylates are methyl methacrylates, ethyl

acrylates and butyl acrylates. Butyl acrylates have to be copolymerized with firmer

monomer as it is too soft. All acrylates polymer have to be copolymerized with functional

monomer for acceptable fastness.

Vinyl acetate exhibit good adhesion to variety of substrate and is expensive. As a

homopolymer it is stiff and has poor fastness properties and water resistance. When

copolymerised with acrylates it this disadvantages are overcome without affection the

adhesion. Vinyl acetate copolymers are not stable at low pH and will go hydrolysis to form

polyvinyl alcohol and acetic acid and cause discolouration.

Styrene is generally used to increase the toughness of softer monomers like butadiene. It is

used to improve the adhesion properties of binder. Styrene is susceptible to non-polar

solvent degradation and when exposed to UV rays it undergoes oxidation which is evident

from yellowing of substrate. This can be controlled by addition of anti-oxidant. Acrylonitrile

is also hand building polymer and is used to increase the toughness without increasing the

stiffness to the extent of styrene.

There are two classifications of general monomers, ionic and non-ionic. Ionic monomers are

generally carboxyl containing monomers and increase the film integrity of polymer by

hydrogen bonding and internal crosslinking during polymerization. They increase the water

resistance of the polymer and mechanical stability of binder by imparting a charge on

particle surface which will electrostatically stabilize binder. Non- ionic functional group

include epoxy and amide monomers and are added for post polymerization crosslinking.

They improve fastness properties and water resistance as it is better than carboxyl group in

inter particle crosslinking.

Binder Properties

Pigments have certain properties which contribute to overall properties of the end fabric.

Certain pigments are more heat sensitive while other have better light fastening effect.

While there are specific fastness properties that are dependent on the pigment used, the

choice of binder can significantly influence this properties. The properties of some of the

common binders are given in the table below.


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Conclusion

Binders are used to keep the colour on fabric during pigment printing or dyeing. The choice

of binders will always depend upon the properties we have to give to final product and the

cost of process. Choosing a proper binder is complex but very critical step and the place to

start is to determine what final properties we wish to incorporate in our end product. If

softness and crockfastness are the most important then butadiene should be used but if the

fabric is light and is going to be exposed to sunlight for long time then acrylate binder

should be used.

Through new technology and development in science of textile colouration, different ways

are being explored in order to address the ever changing need of this industry. New

polymers and additives are continuously evaluated in order to advance the performance of

pigment colouration.

binders in textile printing

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