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Lubricating Agent and Its Impact in Wet Processing

Abstract:

In textile wet processing, many chemical have been used to ease the main processes in wet processing. These chemicals are not responsible for main purposes like scouring, bleaching and dyeing but they are so important to be used in those processes to satisfy the modern sophisticated wet processing requirements. These are called auxiliaries. The mechanism and impact of auxiliaries need to be understood clearly. This article focuses lubricating agent which is one of those auxiliaries that is very important for problem free processing. This study will serve that and also will help to ensure appropriate uses of auxiliaries to increase the performance of wet processing. The knowledge is for R&D, optimum uses of auxiliaries and further development of auxiliaries.

Introduction:

Different kinds of auxiliaries are used in wet processing for specific purpose. Using appropriate amount of auxiliaries can give the solution of various types of problem e.g. prevention of the crease mark on the fabric surface during processing by using lubricating agent, removing water hardness by using sequestering agent, easing the dyeing and achieving level dyeing by using leveling agent etc.

Lubricating agent:

In low liquor ratios and high temperature, when fabric is processed in full-loaded rope dyeing machines (jets, overflows or winch becks) fabric prone to crease(line caused by folding) , chafe (make or become sore or damaged by rubbing) as well as wrinkle line. In high temperature, if crease or chafe mark and wrinkle line is formed, these are permanently seen on the fabric surface and cannot be removed easily. So the Lubricating agent is used to prevent running crease-crack-chafe and crush mark as well as wrinkle line. It offers reliability in the pretreatment, dyeing and soaping bath for difficult textiles.

Buyer or consumer does not accept the crease mark in product. So, using the lubricating agent is the proper solution of mentioned problem. Lubricating agent has such type of characteristics which gives benefit in wet processing to prohibit crease mark.

fig_1Figure 1: Fabric is passed through nozzle

Table 01: Characteristics and Benefit of Lubricating agent [1]

Characteristics Benefits
Reduce fabric to  fabric friction -No imposition of crease mark during processing.
-Ropes opens and displacement more easily.
Reduce fabric to metal friction -Fabrics run better and no chafe or crush marks are formed
Lower the co-efficient of friction -Higher utilization of jets and winches.
-Improved results in short-liquor processing
Increases cohesion, adhesion as well as viscosity of liquid -Increase viscosity and wet pick up, water become thick.
-Avoid the formation of crease marks and improves running properties of ropes
Makes water behaves as lubricating -Fabric surface become slippery, gets sliding effects and protected from crease marks.

 These positive effects on the running properties of piece goods allow greater loading of the dyeing machine and or a higher circulating speed of the rope. [3]

 The auxiliary often is called anticreasing agent in our country but it is named as lubricating agent by the chemical manufacturer. The chemical does not provide the property of anticrease or wrinkle resistance after processing. But the chemical gives very slightly anticrease effects in end product due to remaining some anticreasing agent in the textile but it can be ignored. The auxiliary acts as the way of lubrication. So, it is better to say lubricating agent.

Factors of Crease Possibility:

The Probability of crease mark depends on some factor which is described in shortly;

Fabric Type: Woven fabric is processed in open-width, certain tension and less time required. So, the possibility of creasing is less in woven fabric and lubricating agent does not use in woven fabric processing. But knit fabric is processed in rope form; require longer fabric exposure in high temperature. Crease possibility is higher in knit fabric but the possibility is not same in all kind of knit fabric. Single jersey and its derivatives are highly crease prone. Crease proneness of single jersey fabric depends on its GSM. Normally crease proneness increases proportionally with increase GSM up to 200 GSM fabrics. But interestingly it decreases on further increment of GSM from 200 GSM fabrics. Single jerseys of 190-200 GSM is highly crease prone. Double jersey (as like rib, purl and interlock fabric) is less creases prone. Because they are balanced due to it looks same in both sides and it has more space to relax in its structure. Generally lubricating agent need not to be used in double jersey fabric.

Also crease possibility increase with increasing yarn count, yarn twists and yarn tension during knitting. If manmade fiber could be processed at cotton processing temperature, crease possibility will be less. But manmade fiber (like polyester, nylon) is processed at 130oC therefore crease possibility will be high.

Reasons of creasing in detail:

  1. Imposition of high friction. It is seen in figure 1 that when fabric is passed through nozzle where high friction is imposed between fabric to fabric and fabric to metal.
  2. High twisting tension is caused by tighten rope and entangled during continuous circulation of fabric inside the machine.
  3. In high temperature liquor viscosity reduces dramatically. In the machine fabric in rope form faces continuous squeezing (when pass through the winch) and cushioning (when come out from the inch). In high temperature when liquor viscosity is very less fabric cushioning ability decreases hence permanent crease marks are being produced.

Water viscosity is decreased in order to increase temperature; it can be seen in following table.

Table 02: Water viscosity versus Temperature (From en.wikipedia.org/viscosity)

Temperature oC Viscosity (mPa.s) mili pascal-second
20 1.002
50 0.5471
80 0.3550
100 0.2850

In pretreatment, dyeing and finishing bath, temperature is kept (60-95)oC. In this temperature water viscosity becomes one third which is shown above table. Viscosity falls because of reduction of cohesion (Cohesion is the attraction between similar molecules[2]) of water. For increasing temperature molecular movement raises and intermolecular attraction force reduces (as like vander walls force), therefore cohesion of water decreases as well as viscosity. As a result water becomes harsh and wet pickup of fabric reduces so that the friction increases between fabric to fabric and fabric to metal.  So, possibility of crease mark increases in crease prone fabric. Therefore crease prone fabric is creased, in high temperature and tension the crease mark become permanent.

Chemical constitution and property of lubricating agent:

  1. Poly-ethers co-polymer: it is nonionic character and low foaming. Also Polyethers is more resistant to hydrolysis but tend to swell more in aqueous environment [4].

fig_2                                         Basic form of polyether [4]

  1. Acrylamide or Acrylic acid copolymer: It may be got anionic and nonionic. Most of the chemical manufacturing company uses this chemical because it has no impact on solubilizing of dyes or other auxiliaries and high swelling property. Also nonionic chemical remain neutral in wet processing bath.

 fig_3fig_4  Figure 1: Polyacrylamide[6]                                   polycrylic acid[6]

  1. Sodium salt of sulfated fatty acid: It has anionic character. It can be used with anionic and nonionic fiber. It is none foaming and even reduces the foam.

Mechanism of lubricating agent:

The action of Agent is easily defined in the way of physical chemistry and related to the term of viscosity. Some terms are described above. (Viscosity is the “thickness” of fluid. Thus, water is “thin”, having a lower viscosity, while honey is “thick”, having a higher viscosity.[2]) Lubricating agent increases viscosity resulting reduces the friction of solid parts while rubbing against each other. The mechanism is elaborated in three ways:

  1. By providing Lubricating:
    Lubricating agent is polymer based and easily soluble in water. It swells in water by accomplishing this feat by organizing water molecules around the ions using ion-dipole.

fig_5Figure 2: Swelling polymer increases viscosity. From the presentation of Viscosity Control in H&FC Formulations with RHEOVIS ® Polymers /Ciba/Home and fabric Care/ October, 2003.

This means charged things or polymer swelling increases the viscosity of the water. Here more ions dissolved in the water will organize more water molecules. In figure 2, an example of polymer swelling is given for cellulosic fabric processing. Swelling property varies from polymer to polymer. (e.g. The poly[acrylamide–stat–(acrylic acid)] hydrogels can be made to swell up to 20,000 times, v/v[4].) If polymer has high swelling property, less amount of chemical requires to increase viscosity or thickness of water. In Figure 3 show polymer swelling and organize water molecule. After swelling, polymer increases water viscosity and providing thick layer of water having lubricating function.

fig_6Then the coefficient of friction reduces between fabric to fabric and fabric to metal. Therefore fabric surface become slippery and the possibility of crease mark is less. So, fabric can run without friction in treatment bath. How many coefficient of friction is reduces, it cannot be expressed easily. The machine of measuring of coefficient of friction is highly expensive.

  1. By increasing wet pick-up:
    With increasing temperature

fig_7Figure: 4, high viscous liquid are held by Steel stick (from www.physics.usyd.edu.au/teach_res/jp/fluids)

water viscosity falls as well as cohesion and adhesion. Adhesion is the tendency to adhere dissimilar molecule due to attractive force[2]. By reducing adhesion of water, the wet pick up of fabric is decreased during processing. After using Lubricating agent wet pickup of fabric rises. An experiment result taken from BASF; They got water carrying capacity about 9431g of water without using lubricating agent where by using lubricating agent showed 12835g of water by using 3g/L lubricating agent and liquor retention increased about 36%[7]. So, lubricating agent increases viscosity and adhesion of water in treatment bath as well as liquor carrying capacity. Also another example can be given, two wood stick is sunk in water and oil. More oil is held in wood stick because of their high viscosity. Oil viscosity (110 centipois) is more than water (0.89 centipoise) at 25oC[2]. For that oil adhesion property is more than water.

If wet pick up of fabric is high then the fabric get the environment as like floating on  water and reduces friction between fabric to fabric or fabric to metal. The advantage is that at the nozzle higher liquor viscosity means the same circulation pump carries more water enhancing higher flow with lower pressure. This lowers the tension and prevents less sharp crease marks which enable easy displacement of fabric rope.

  1. Increasing Cushioning property:
    Cushioning is the prevention from more crease or fold while fabrics are loaded in compact or compressed condition. Normal water cannot provide cushioning effect because of low viscosity.  So, fabric becomes creases during processing at high temperature resulting imposition of permanent sharp crease mark. Bath liquor has high viscosity at low shear acting as a cushion. It is seen at figure 5 that thickened water sags between two layers of fabric when fabric becomes fold.

fig_8Figure 5: Lubricating agent provides cushioning property. From grouchier of Primasol® JET(Lubricating agent of BASF) 

As a result fabric is prevented from sharp crease mark. When the fabric arrives at the bottom of the machine, the fabric presses less on lower which helps to maintain less sharp crease marks.

There is another mechanism developed by Clariant®, it especially developed for the dyeing of cellulose fibers alone and blends with other fibers. It is liquid and acts in two ways:
1- It migrates into fibers, providing sliding properties to the yarns in knit fabrics so that the friction between fibre to fibre and fiber to metal is less.

2- It changes the flow behavior by film formation of the bath so that a liquor forms on the surface of the goods which promotes sliding down of the material and prevent the formation of creases.

Uses of the agent:

The lubricating agent should be used as per the recommendation of chemical manufacturer, as per the type of fabric and condition of the process. In pretreatment bath the agent is used as more than dyeing bath because high temperature is required in pretreatment compared to dyeing. More uses of the chemical produce high viscous water which have adverse effect (such as gel formation, impairs solubility of dyes, causing crack marks in the fabric etc). Many of the auxiliaries are used in pretreatment or dye bath and they have to be solubilized. But the solubility of chemicals and dyes reduces in high viscosity. Also it is an expensive auxiliary compared to other. It should not use more than necessary.

Also, in modern machine (Thiese-Luft-Roto plus) friction between machine to fabric is less than conventional machine. In Thiese-Luft-Roto Plus fabric is transported smoothly to the rear to machine by air [8], here less amount of lubricating agent can be used to reduce cost.

Conclusion:

Uses of the lubricating agent give the solution of crease mark in treatment bath. So, fabric is saved from the permanent sharp crease mark. Using of the chemical is very sensitive, depends on fabric GSM. We have to optimize the use of the chemical to reduce cost and get better effect.

Acknowledgement:

I gratefully acknowledge the help rendered by A.S.M Tareq Amin (Editor and Publisher, Bangladesh Textile Today), Syed Mohammad Ismail (sales head, HUNTSMAN), Sujit Saha Roy(Asst Manager, BASF), Mohammad Mohsin Uddin (Marketing Manager, Clariant), Dr. Saifur Rahman (Chief Faculty member, NITTRAD), Ismat Zerin (Lecturer, City University), and Shaheen Akhter(Labrotary incharge, HUNTSMAN), for giving information about this topics.

References:

[1] Technical Data Sheet of Lubricating Agent of HUNTSMAN®
[2] en.wikipedia.org/viscosity, cohesion, adhesion
[3] Technical Data Sheet of Lubricating agent of BASF
[4] L.H. Sperling, Introduction to physical polymer science”, Fourth Edition,  John Wiley & Sons, 2006 P.16, 484, 474
[5] Technical Data Sheet of Lubricating Agent of Clariant®
[6] JAMES E. MARK,Polymer Data Handbook, Oxford University Press, 1998, p.247,251
[7] Grouchier of Primasol® JET (Lubricating agent of BASF)
[8] Mr. Thomas Mende, presentation/Thies/Innovations in Dyeing/ IFC International Conference March 2005
[9] F. A. Holland,R. Bragg, “Fluid Flow for Chemical Engineers”, ARNOLD PUBLICATION, London, May, 1994

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