MI1-Höhn – Fahne 1 substances in deaerators are significantly lower than they are in pure defoamers. In addition, a so-called penetrator ensures the agent penetrates better into the fabric. A fur- ther essential component are the emulsifiers, which as a rule are based on ethoxylated fats and fatty alcohols, often with the addition of alkyl/aryl sulfonates to make them tempera- ture and electrolyte-stable. In certain cases, silicone surfactants (ethoxylated silicones) are also used to enhance the penetrative and defoaming effect. These emulsifiers are largely responsible for the surfactant effect. The chemical complexity and variety of the different formulations in commercial use is reflected by wide differences in performance profile between deaerators of different brands and especially different types. How deaerators work In simple terms, a deaerator combines the effects of a defoamer and a surfactant. Fig. 1 shows this in schematic form, using the dye- ing of a yarn bobbin as an example. What- ever the condition or format of the fabric, the deaerator must ensure that unwanted air pockets are eliminated. This is achieved by defoaming, surfactant and penetrative ef- fects. It is generally measured by assessing the fluid uptake of a bobbin that is fully im- Deaerators – textile auxiliaries that can do (almost) anything Deaerating agents have been part of textile finishing processes for many years now, and significantly improve the quality of the end result. Tradition- ally, they have been used to get unwanted air pockets out of the fabric be- fore the start of the dyeing process. However, what is less well known is their versatility, and the way that they can be used to improve a number of wet finishing processes. Almost any fabric substrate, at any stage of processing and in any finishing process can be significantly improved by a deaerating agent. The chemical properties of these substances, how they work and what they can be used for will be outlined here. The advantages and dis- advantages of different types of deaerators will be described, and finishes with a look at the current state of the art. Wolfgang Höhn Pulcra Chemicals GmbH, Düsseldorf/Germany The way in which these individual compo- nents combine, is what gives this class of product both its eponymous deaerating effect (Figs. 1 and 2), and its high level of stability, and in particular shear stability. It is these two characteristics that distinguish deaerators from the chemically and function- ally related category of products known as defoamers. The defoaming components are typically based on silicone, mineral or plant oils, tri- isoalkyl phosphates, fatty alcohols and fatty amides, and on binary and ternary combina- tions of these. The concentrations of these Chemical structure and basic principle of deaerators Scientifically speaking, the term “deaerator” covers a very disparate group of process chemicals that vary hugely in terms of their molecular composition and applications. However, what all deaerators have in com- mon is a combination of defoaming, pene- trating, surfactant and emulsifying compo- nents that work together chemically and functionally. Abb. 1 Wirkungsweisen von Netzmitteln, Entschäu- mern und Entlüftern
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substances in deaerators are significantlylower than they are in pure defoamers. In addition, a so-called penetrator ensures theagent penetrates better into the fabric. A fur-ther essential component are the emulsifiers,which as a rule are based on ethoxylated fatsand fatty alcohols, often with the addition ofalkyl/aryl sulfonates to make them tempera-ture and electrolyte-stable. In certain cases,silicone surfactants (ethoxylated silicones)are also used to enhance the penetrative anddefoaming effect. These emulsifiers arelargely responsible for the surfactant effect. The chemical complexity and variety of thedifferent formulations in commercial use isreflected by wide differences in performanceprofile between deaerators of differentbrands and especially different types.
How deaerators workIn simple terms, a deaerator combines the effects of a defoamer and a surfactant. Fig. 1shows this in schematic form, using the dye-ing of a yarn bobbin as an example. What -ever the condition or format of the fabric, thedeaerator must ensure that unwanted airpockets are eliminated. This is achieved bydefoaming, surfactant and penetrative ef-fects. It is generally measured by assessingthe fluid uptake of a bobbin that is fully im-
Deaerators – textile auxiliaries that can do (almost) anything
Deaerating agents have been part of textile finishing processes for manyyears now, and significantly improve the quality of the end result. Tradition-ally, they have been used to get unwanted air pockets out of the fabric be-fore the start of the dyeing process. However, what is less well known is theirversatility, and the way that they can be used to improve a number of wetfinishing processes. Almost any fabric substrate, at any stage of processingand in any finishing process can be significantly improved by a deaeratingagent. The chemical properties of these substances, how they work andwhat they can be used for will be outlined here. The advantages and dis -advantages of different types of deaerators will be described, and finisheswith a look at the current state of the art.
Wolfgang HöhnPulcra Chemicals GmbH, Düsseldorf/Germany
The way in which these individual compo-nents combine, is what gives this class ofproduct both its eponymous deaerating effect (Figs. 1 and 2), and its high level of stability, and in particular shear stability. It isthese two characteristics that distinguishdeaerators from the chemically and function-ally related category of products known asdefoamers. The defoaming components are typicallybased on silicone, mineral or plant oils, tri-isoalkyl phosphates, fatty alcohols and fattyamides, and on binary and ternary combina-tions of these. The concentrations of these
Chemical structure and basic principleof deaeratorsScientifically speaking, the term “deaerator”covers a very disparate group of processchemicals that vary hugely in terms of theirmolecular composition and applications.However, what all deaerators have in com-mon is a combination of defoaming, pene-trating, surfactant and emulsifying compo-nents that work together chemically andfunctionally.
Abb. 1 Wirkungsweisen vonNetzmitteln, Entschäu-mern und Entlüftern
mersed in stationary cold fluid (Fig. 2). Whilethese tests are differentiating and replicable,and do allow an assessment of the surfactanteffect to be made, in certain circumstancesthis should be measured separately using theusual methods, such as DIN ISO 1822.
Applications of deaeratorsDeaerators are suitable for use in a widerrange of processes than practically any othertextile auxiliary. While dyeing remains theirprimary area of application, they are also essential to pretreatment, printing, washing,finishing and coating processes.The main process applications of deaeratorsare as follows:
Discontinuouspretreatment/dyeing/finishing• For package systems (loose stock, rovings,
bobbins, muffs, beams): deaeration andoptimum penetration of the fabric; partic-ularly important during dyeing. For best re-sults, it is recommended to add the deaer-ator five minutes before the other (surfac-tant) auxiliaries. In yarn dyeing, the dyeflow direction should be exclusively in:outat this stage.
• In jet dyeing: deaeration of the fabric forbetter dye retention without immersion.The defoaming effect complements the
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components of dyeing accelerators) caus-ing the same problem.
Continuous applications in pretreatment,dyeing and finishing (padding/maximumbatch size/minimum batch size process)In this case, the combination of surfactant,defoaming and penetrative effect is a partic-ular benefit over and above the basic deaer-ation. What is more, a deaerator emulsion isnaturally less likely to separate in low-turbu-lence liquid flows than a liquid defoamer, aproperty which is particularly useful in con-tinuous processes.
Textile printing and coating/laminationHere, the focus is on deaerating the paste.Improving the solubility and penetration ofthe dye is desirable. Deaerators also have apositive effect on the flow behavior of printpastes.
Garment washing and dyeingThe keys here are an excellent surfactant andpenetrative effect, combined with good en-zyme tolerance. This improves the depth andevenness of garment dyeing, particularly institched hems.
Advantages and disadvantages ofdifferent types of deaerators/historicaloverviewDeaerators have been in use for more than30 years, and throughout this period there
typical foam profile of (non-ionic) surfac-tants, which normally decreases as tem-perature rises. In this case, it is recom-mended to add the deaerator before load-ing the machine.
• In all discontinuous systems: prevention ofcavitation, i.e. stopping liquid chemicalsfrom vaporizing on the pump suction sideand thereby keeping the liquid circulatingproperly. If deaerators are not used, abuild-up of sufficient static pressure couldresult in foaming elements in the liquid(surfactants) or volatile compounds with ahigh vapor pressure (e.g. solubilizers or
have been both specialist and general-pur-pose variants, also both silicone-based andsilicone-free types. Over the years, aeratorshave constantly been developed to improvetheir safety and efficiency.
First-generation silicone deaeratorsThis is the standard deaerator, and even today, it remains the most widely used. De-pending on their silicone content, productsmay be more suited to jet or package dyeing.However, their stability in alkalis, electrolytesand especially in cyan and anthraquinonedyes can be highly variable. Moreover, sili-cone-based products are not used in certainareas, such as automotive applications andflame-retardant PET.
Tri-isobutyl phosphate-based deaeratorsThis type of silicone-free deaerator repre-sents an interesting and complementary alternative to first-generation silicone-basedproducts, particularly where a rapid surfac-tant effect is required. On the other hand,defoaming performance is poor, and in someproducts, the volatile, solvent-like tri-isobutylphosphate can attack certain plastics, as well
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as causing undesirable emissions. However,tri-isobutyl phosphate-based deaerators aresuitable for use in automotive applicationsand on flame-retardant PET, offer good stability in alkalis and electrolytes, and arenot known to exhibit an intolerance to cyandyes.
Mineral-oil and plant-oil deaerators These silicone-free products are an alterna-tive to conventional first-generation siliconedeaerators that are suitable for the samesorts of application. While their universal ef-fects are weak and they are not very stable inalkalis, they can however be used in automo-tive applications and on flame-retardant PET.
Fatty alcohol deaerators This class of product is an evolution of tri-isobutyl phosphates, and represents a signif-icant advance in terms of workplace safety(emissions) and material tolerance. They canbe used without any problem in automotiveapplications and on flame-retardant PET. Likedeaerators based on tri-isobutyl phosphate,they have a rapid surfactant effect, but theirtolerance of alkalis and, in particular, cyan
dyes is limited. Fatty alcohol deaerators havelargely replaced tri-isobutyl phosphate-basedproducts, but for many applications, they arenot a viable substitute for silicone deaera-tors.
Second-generation deaerators Breviol ELN from Pulcra Chemicals is a highlyefficient universal deaerator. Extremely versa-tile and safe to use, it combines virtually allthe key benefits of the four types of deaera-tor discussed above, thanks to a number ofspecial additives in its formulation. It is man-ufactured using a sophisticated new emulsi-fying technology. It is also designed to sup-port the latest requirements of users, such aseasy automatic dosing.The only slight limitation of Breviol ELN relates to its use in automotive applicationsand flame-retardant fibers (such as modifiedPET and viscose), where even tiny amounts ofsilicone oil can have a detrimental effect. Forthis reason, it is recommended that othertypes of deaerators, typically those based onfatty alcohols or tri-isobutyl phosphate, areused for these applications, because of theirwater vapor volatility when drying.
