STRENGTHENING THE WIDENING PERFORMANCE OF FINISHES
►►► INTRODUCTION

Through the whole manufacturing chain, Fibre finishes accompany the fibre, most commonly in a topical solution. A finish helps the fibre in passing through machinery. Without it, friction would immediately stop the machine. Now a need is felt for fibre finishing technologies, which are indispensable to manufacture as well to grow rapidly. An upsurge in textile production has given fibre finish suppliers a reason to continuously seek new and enhanced technologies that provide value and cost efficiency to their customers. Fibre finishes have two uses in the industry: to process Fibre (e.g. spin finishes) and to give advantageous end properties to an accomplished article (e.g. effect finishes), such as wicking for a diaper cover stock. Fibre finishes are compulsory for processing synthetic Fibres and without their use, various areas where synthetic Fibres are now applicable would have remained unrealized. To cope with the specific processing environment and for the end-use application, Fibre finishes are evolved. If properly chosen, Fibre finish is able to give can provide differentiation among the contributions of diverse producers, creating a competitive benefit. The "bar" on the performance of Fibre finishes is continuously being raised. Any advancement in the performance of Fibre finishes would be gladly appreciated. Controlling the costs, whenever possible, is the pressing need of the competitive environment. Thus, together with the craving for higher performing Fibre finishes is the craving to apply as little Fibre finish as required to give the necessary effect. As a result, the need exists for higher performance finishes that "do more with less." Another stress is the environmental effect of applying processing Fibre finishes. It is normal that a considerable amount of the Fibre finish applied does not really coat the Fibre. Approximate calculations of the bulk of the lost finish vary between 10% to nearly 50% in some cases. This "lost" finish is an environmental load as well as a cost exhaustion. Thus, the need exists for Fibre finishes which are greatly associated with the Fibre surface during application. Work is in motion at companies, who deliver critical Fibre finish modules and Fibre finishes, improving solutions to these recognized market needs. It is beyond doubt that the effect of new chemistry used in Fibre finishes would be important, but given the time for qualification of the new chemistry and the regulatory processes that go with the introduction of new chemistry; this would seem to be a longer-term solution. An immediate answer would be to improve the performance of present Fibre finish technology through ace formulation of the spin finish module chemistry available. Uniqema is a supplier of Fibre finish modules and completely formulated Fibre finishes. It has evolved Enhanced Surface Coverage (ESC) technology to advance Fibre finish performance. The ESC technology strikingly upgrades the degree of surface coverage of the finish on Fibre surfaces. Better surface coverage offers the following advantages:


. Improves the effect performance of the Fibre finish, properties of friction, antistatic and wicking in particular;
. Puts up with a lower finish loading to be used because of better surface coverage;
. Decrease the amount of finish lost into the environment during application.


►►► WETTING vs. SPREADING

Surface coverage by a Fibre finish includes two crucial, yet dissimilar features: wetting and spreading. It is important to figure out the difference between these two aspects.


Wetting: Normally, spin finish formulations are composed of a lubricant and antistatic properties, albeit other effect components such as antimicrobials and wicking agents also can be incorporated. Very often, the spin finish


formulation is used in adulterated form, either as an emulsion (whereby, an emulsifier would be formulated into the spin finish), a solution or dispersal. In each of these cases, water would be the diluent. Smooth coverage of the Fibre surface by the diluted finish is desirable. This effect can be brought to fruition by including a wetting agent into the spin finish formulation. Many superior wetting agents are available for fusing into spin finish formulations. Wetting performance of diluted spin finishes is rarely an issue.


Spreading: The final performance of any Fibre finish relies upon the strength of the finish to preserve even surface coverage after the water diluent has faded out from the finish. Moreover, the performance of any neat (undiluted) finish depends on its capacity to cover evenly the Fibre surface upon application. Neat finishes are significant for many crucial applications; therefore, surface coverage is a related issue. This phenomenon of the spin finish to evenly cover the Fibre surface is the complete opposites of the phenomenon of wetting. Spreading is the end product that is depicted by the capability of the spin finish to cover the Fibre surface. Bad spreading lessens the efficiency of the spin finish on the Fibre surface. Good spreading improves the effect delivered by the Fibre finish components which could lead to advanced performance at a given spin finish loading or the knack to apply less spin finish and still obtain preferred Fibre surface effects. Often, good wetting agents do not perform well to cater spreading performance to the Fibre finish. Thoroughly separate chemistry is required to provide the preferred effect.


►►►PERFORMANCE RESULTS:

The advantages of the improved surface coverage can be seen in various performance parameters. Data have been produced by comparing the lubricant, antistatic and wicking performance of Fibre finishes with and without the increased surface coverage technology. Polypropylene was used for the assessments.



Lubrication: Lubrication performance in a Fibre application characteristically includes two noticeable frictional measurements: Fibre-to-metal (F/M) friction and Fibre-to-Fibre (F/F) friction. Both measurements are equally significant for the processing of a Fibre and its transformation into a complete article. To improve performance in each of these frictional measurements, better surface coverage has been displayed.


Figure I. mentions the F/M frictional performance of a standard spin finish and the same finish with the improved surface coverage technology included therein. The standard spin finish displays comparatively inferior performance at low spin finish loading level. Inadequate product is introduced to provide the preferred degree of protection. The increase in loading of spin finish creates a positive effect on performance (i.e. lower F/M/ friction). Hydrodynamic lubrication is the system of performance at the higher finish loading.

In contrast, the same spin finish with improved surface coverage furnishes excellent performance at a considerably lower loading. Unlike hydrodynamic lubrication, at low spin finish loading, the influential lubrication system would be boundary lubrication. The improved spreading technologies display a uniform molecular orientation on the surface of the Fibre, leading to the impressive performance. As the loading of spin finish extends, hydrodynamic lubrication becomes the leading mechanism and the benefit of the improved surface coverage is reduced.

Commercial experience on polypropylene staple Fibres has proved that the frictional advantages of developing the surface coverage of the finish can allow a major (ca. 40%) decrease in the finish level while at the same time allowing an important boost (ca. 30%) in the yarn spinning speed. Moreover, the healthier coverage enriches abrasion properties of the Fibre and consequently reduces the generation of dust during subsequent processing.

Figure II. mentions the effect of the improved surface coverage technology on F/F friction. The influence of the enhanced surface coverage technology is not as prominent as was the case of F/M friction. F/F friction is dangerous at lower speeds than the range that is significant for F/M friction. At lesser speeds, the influence of prompt and complete coverage is not as great an advantage as is the case with higher speeds.




Very often, it is not preferred to distinctly lessen F/F friction as a certain degree of orderliness between the Fibres may be vital for effective functions like carding. Thus, it can be said that the improved surface coverage technology does not make hostile effect on this parameter.


Antistatic Performance: Overall, Synthetic Fibres are inferior electrical conductors. Electrostatic charges can easily develop a Fibre surface unless and until the surface is treated with a spin finish having an antistatic force.


Antistatic agents are performed by drawing a molecular cover of water to the surface of the Fibre. The water constructs an uninterrupted path on the Fibre surface. The water has a greater amount of conductivity than does the Fibre surface, enabling the treated Fibre to discharge electrostatic buildup. Performance is directly applicable to the level to which antistatic agent has covered the Fibre surface.

Once again, a "standard" spin finish was assessed with and without the improved surface coverage additive. Figure III. displays the results. The improved surface coverage technology sanctions antistatic performance to be achieved at far lower loading than is the case with the "standard" finish. The improved surface coverage technology allows the finish to cover the surface briskly and thoroughly.



Wicking: Polypropylene has a poor surface energy. As such, high surface energy liquids, like body fluids or water, will not easily moisten a polypropylene surface. Nevertheless, the fruitful use of polypropylene in applications such as diaper cover stock relies on the strength of the polypropylene surface to let liquids move quickly through it to "super absorbent" layers below. The conversion of polypropylene into a useful material of construction for these applications includes the use of wicking agents. Wicking agents alter the surface features of polypropylene, allowing liquids to quickly "wick" through the cover stock layer.


Various successful hydrophilic wicking agents are available and each functions well in a single use application. Nevertheless, an urgent need is to enhance wicking agents that will cope with several insults or have the strength to re-moisten the polypropylene surface. Most standard wicking agents are washed from the surface after one or two insults and are not strong enough to give wicking performance.


The improved surface coverage technology offers better wicking performance in proportion to a standard finish, for both melt-blown fabric and spun-bond fabric. The outcomes are displayed in Figure IV. The performance of two improved surface coverage technology finishes is compared to that of a "standard" finish.


Given the improved lubricant and antistatic performance, the improved wicking performance of the developed surface coverage technology is not surprising. Nevertheless, what is astonishing is that the improved surface coverage technology produced Fibre, which was strong enough to cope with numerous insults still has wicking property.


The "standard" finish loses its strength in wicking performance after 1-2 insults. Nevertheless, the improved surface coverage technology finishes endure 4-5 insults. We assume that the better spreading of the finishes is made by a greater alliance of the finish for the polypropylene surface, which results in resilience of the effect on the surface.


►►► FINISH RETENTION ON FIBRE

One thought occurs to mind with the improved surface coverage technology is that it may escalate the finish absorbed on the Fibre as a percentage of the amount applied. Commercial experience with a neat finish for polyester screened as-is and with the enhanced surface coverage technology, showed a sudden boost in the amount of finish retained. The effect of minimizing the "lost" finish from 16% to 2% is two-fold:
. Finish Costs: Scope would exist to minimize finish application level and still be able to bring the same FOY (i.e. finish on yarn) loading to fruition and
. Environmental Responsibility: The outcomes would point out that emissions of "lost" finish could be decreased nearly 90%

Similar commercial experience with a neat finish for polypropylene filament yarn has proved that the level of sling, while not quantified, was suddenly decreased when using an "ESC" finish, leading to a spotless working atmosphere in respect of both air-borne droplets and floor/machine contamination.


►►► SUMMING UP

The performance of Fibre finishes is abundantly improved by the inclusion of developed surface coverage technology. The improved surface coverage technology approves the finish to evenly cover the Fibre surface. The outcomes of the improved surface coverage are added properties for the Fibre, in proportion to Fibre with "standard" finishes; the strength to optimize finish loading to balance cost/effect; and, the scope to decrease the environmental load of Fibre finish.