chemical softeners

7/27/2019 Chemical Softeners

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Chemical Softeners


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Chemical Softeners

Chemical softeners have gained great importance infinishing; almost no piece of textile leaves theproduction facilities without being treated with a

softener. Softening treatment is to give the textiles the

desired handle, make further processing easier andimprove the handling properties.

A nice, soft handle is often the decisive criterionfor buying a textile and is therefore of most vitalimportance for marketing many textiles product.


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Objectives of chemical softening

A Softener's main purpose is to improve the aestheticproperties of textiles

It gives the fabric the desired handle; usually withimaginative descriptions such as soft, full, super soft,

smooth, elastic, firm, dry, sludgy etc. It positively influences the technological properties

such as antistatic, hydrophilic properties, elasticity,sewability, abrasion resistance etc.

It gives synthetic fibres a certain degree of naturalfeeling and improve the handling properties throughsecondary effects (antistatic, smoothness, moistureregulation etc.).


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Desirable properties of textile Softeners

Easy handling (liquid, pump able, stable dilution)

Good compatibility to chemicals, easy to combine

Stable to high temperatures, not volatile by Water Vapour

No yellowing

No effect on fastnesses No colour shade changes

Leaves no deposits on rollers

Regular and complete bath exhaust

Spray able Not toxic, not caustic, not corrosive

Easily biodegradable

Dermatologically harmless

No restriction for transport and storing (flash point)


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Classification of textile softeners

according to their Ionogenity

Ionic Activity Electric Charge

Nonionic No charge

Ionic Negative Charge

Cationic Positive Charge

Pseudo Cationic At acid pH slightly cationic

Quaternary Cationic (no matter of pH)

Amphoteric Depending on the pH


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Mechanisms of the softening effect

Softeners provide their main effects on thesurface of the fibres. Small softener molecules,in addition, penetrate the fibre and provide an

internal plasticisation of the fibre formingpolymer by reducing of the glass transitiontemperature Tg.

The physical arrangement of the usual softenermolecules on the fibre surface is important . Itdepends on the ionic nature of the softenermolecule and the relative hydrophobicity of the

fibre surface.


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Cationic Softener

Cationic softeners have the best softness and are reasonablydurable to laundering. They can be applied by exhaustion toall fibres from a high liquor to goods ratio bath and theyprovide a hydrophobic surface and poor rewettingproperties.

They are usually not compatible with anionic products(precipitation of insoluble adducts).

Cationic softeners attract soil, may cause yellowing uponexposure to high temperatures and may adversely affect thelight fastness of direct and reactive dyes.

Inherent ecological disadvantages of many conventional(unmodified) quaternary ammonium compounds(quaternaries) are fish toxicity and poor biodegradability. Butthey are easily removed from waste water by adsorption andby precipitation with anionic compounds.


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Mechanism of the softening effect of

Cationic softeners

Cationic softeners orient

themselves with their positively

charged ends toward the partially

negatively charged fibre (zeta

potential), creating a new surface

of hydrophobic carbon chains that

provide the characteristic excellentsoftening and lubricity seen with

cationic softeners.


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Anionic Softeners

Anionic softeners are heat stable at normal textile

processing temperatures and compatible with other

components of dye and bleach baths.

They can easily be washed off and provide strong

antistatic effects and good rewetting properties

because their anionic groups are oriented outward

and are surrounded by a thick hydration layer. They are often used for special applications, such as

medical textiles, or in combination with anionic

fluorescent brightening agents.


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Anionic Softeners

Anionic softeners, orient

themselves with their

negatively charged ends

repelled away from the

negatively charged fibre

surface. This leads to higher

hydrophilicity, but lesssoftening than with cationic

softeners.


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Amphoteric Softeners

They have good softening effects, low

permanence to washing and high antistatic

effects (because of their strong ionic

character).

They have fewer ecological problems thansimilar cationic products.


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Nonionic softeners

Nonionic softeners do not carry any electricalcharge and therefore do not possess anydistinctive substantivity. Such products are

applied by means of forced application i.e.usually in padding mangle procedures.

Non-ionic softeners can be combineduniversally, are stable to temperature and donot yellow. This is the reason why this productclass is perfect for finishing optically brightenedhigh-white articles.


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The orientation of non-ionic softeners dependson the nature of the

fibre surface, with thehydrophilic portion ofthe softener beingattracted to hydrophilic

surfaces and thehydrophobic portionbeing attracted tohydrophobic surfaces.


Nonionic Softeners


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Non-ionic softeners based on polyethylene

Polyethylene can be modified by air oxidation in the melt at high pressure

to add hydrophilic character (mainly carboxylic acid groups).

Emulsification in the presence of alkali will provide higher quality, more

stable products.

They show high lubricity (reduced surface friction) that is not durable todry cleaning, they are stable to extreme pH conditions and heat at normal

textile processing conditions, and are reasonably priced and compatible

with most textile chemicals.


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Ethoxylated non-ionic softeners

Polyglycol ethers are synthesized by the addition of ethylene oxide tofatty alcohols, carboxylic acids, esters, amides or amines .

They are surfactants and often used as antistatic agents and ascomponents of fiber spin finishes.

Their main characteristics are relatively high substantivity and

hydrophilicity, non yellowing and sometimes a low softening effect andlubricity, and a potential for foaming during processing.


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Silicone softeners Amino functional silicones have a big importance to textile

softening companies. Their surface smoothening and softening

properties are above all other product groups.

Micro and semi-micro emulsions can be made with specially

selected emulsifying recipes using amino-functional silicones.

They offer a number of advantages which ,are totally in keeping for

modern textile finishing. The low particle size (micro emulsions


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They show good temperature stability and durability,with a high degree of permanence for those productsthat form cross linked films and a range of propertiesfrom hydrophobic to hydrophilic.

Depending on their method of synthesis, siliconesofteners can contain variable amounts of volatilesiloxane oligomers. Together with volatile emulsifiersthese oligomers can cause pollution problems in thewaste air from tenter frames.

In textile finishing, silicones are also used as waterrepellents, elastomeric finishes, coatings and asdefoamers.

Silicone softeners


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Compatibility and combinability

Softener finishes are often combined with easy careand antistatic treatments. As a rule of thumb,hydrophobic softeners cause an extra soft handwhere as hydrophilic softeners bring about some

fullness. In combination with fluorocarbons, most softeners

reduce oil repellency.

Some ionic, surface active and silicone free softeners

are not compatible with water repellents. Since softeners are usually also excellent fiber

lubricants, softening finishes often give poor anti-pilling and slippage properties.


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Properties of emulsions and micro

emulsions


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Particulars of and troubleshooting for

softening finishes

Emulsion stability: When the stability of a normal (notmicro-) emulsion is very high in an exhaust treatment,then the softening effect decreases. An emulsion ofmoderate stability gives the best results, probably

because small drops of the emulsified softener canexhaust to the fiber surface. Poor emulsion stabilitycauses stains.

Reactive softeners: Some softeners have functionalgroups that can react with the corresponding groups of

some fibres, The result is a very durable finish, combinedwith the typical advantages and disadvantages of thiscrosslinking chemistry.


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softening finishes

Softeners and thermo-migration of dyes: Many

hydrophobic softeners are solvents for disperse dyes.

Therefore they increase thermo-migration of the dyes and

the staining of adjacent yarns (bleeding). The crockfastness and wash fastness of the fabric decrease as the

dyes migrate to the fiber surface.

Volatility: Some softeners are volatile or contain volatile

components. During drying, heat setting or curing thesevolatile components can condense on cooler areas of the

ovens and then drop back onto the fabric, causing spots.

Heating the top of the ovens can help prevent this

problem.


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softening finishes

Yellowing: This problem arises especially with undyed

fabrics. It can be caused by the oxidation of cationic

softeners or amino-modified silicones or by the ionogen

attraction of cationic softeners and anionic fluorescent

brighteners (extinguishing the fluorescence by salt

formation). Dispersing agents and product selection are

helpful to reduce this effect.

Mechanical softening: Softening effects can be gained onsome fabrics without chemicals, only by mechanical

treatment, for example washing or in a tumbler or with

high pressure water jets.


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Correlation between molecule structure and

application technical properties


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The Kawabata Evaluation System (KES

The Kawabata Evaluation System (KES) is used to make objective

measurements of hand properties. The KES instruments measure

mechanical properties that correspond to the fundamental

deformation of fabrics in hand manipulation.

The Kawabata system of instruments, featured in the fabric hand

laboratory, measures properties of textile fabrics and predicts theaesthetic qualities perceived by human touch.

The Kawabata Evaluation System (KES) includes five highly sensitive

instruments that measure fabric bending, shearing, tensile and

compressive stiffness, as well as the smoothness and frictionalproperties of a fabric surface.

This evaluation can include measurement of the transient heat

transfer properties associated with the sensation of coolness

generated when fabrics contact the skin during wear.


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The Kawabata Evaluation System (KES)

KES provides a unique capability, not only to predict human

response, but also to provide an understanding of how the

variables of fiber, yarn, fabric construction and finish

contribute to the perception of softness.

A standard specimen size of 20 x 20 cm is used in three

replications. All measurements are directional, except for

compression, and are made in both the lengthwise direction,

and in the crosswise direction of the sample. Appropriate

instrument settings are used for the material being tested


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Handle-O-Meter

The Handle-O-Meter is another method in whichdifferent kinds of deformation have a simultaneous

effect on the sample, resulting in a total value for the

hand.

A rectangular sample of maximum 20 cm or 8 inches

width is pushed by a blade into a variable slit.

Maximum resistance force on the blade is registered,

giving a value that depends on the flex rigidity of thesample and the frictional resistance on the corner of

the slit.

Both the surface smoothness and the compressibility

are included in the measurement.


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Handle-O-Meter

The mean values of both sides of the fabric in

lengthwise and crosswise directions are

determined and recorded. In other relatively

simple methods the resistance is measured,when a textile sample is drawn through a ring

aperture or a nozzle.

The measured resistance force consists ofcomponents of the flexural rigidity, the surface

friction, the shear rigidity and the compressibility.

chemical softeners

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