Getting the right chemical balance20 January 2017
With the current “greening” trend towards alternative solvents, Tony Vince examines the latest research in the chemical cleaning of textiles
Innovation was a key theme at this year’s Texcare show at Frankfurt in June. New technologies are now providing the professional textile care industry with a broad range of drycleaning machines and cutting-edge solvents.
For while chlorinated solvents such as perchloroethylene have been used successfully worldwide for more than half a century, the new breed of drycleaners are keen to find out what’s new and learn about best practice and the new products that the market has to offer.
Forward-looking industry professionals regard the alternatives now available as providing an immense business opportunity. Far from the somewhat misguided public perception that that drycleaning is “out of date” and that the industry is merely reacting to regulatory requirements brought about by restrictions on perc use, individual cleaners can view the options, assess consumer trends for themselves and determine the best cleaning solution to meet the specific requirements of their business and its future development. Each cleaner can develop a strategy for their business and choose a system that specifically suits that strategy.
Importantly, these cleaning systems are increasingly focused on environmental issues such as biodegradability and biocompatibility. Consumers realise that the alternative solutions have certain advantages as they can clean a wider range of textiles and garments as well as being environmentally sustainable. This move toward a consumer sense of “well-being” is a trend that several manufacturers have picked up on. Cleaners can switch away from the perc “mainstream” as the new solvents offer sustainability and improved efficiency. Besides environmental considerations, the ability to clean a variety of garments effectively is perhaps the most important factor to consider if considering solvent alternatives. The solvent should not cause the fabric or garment to unnecessarily fade, bleed colour, change in dimensions (shrinkage), weaken or damage trims and still be effective at cleaning and removing stains.
In recent years there has been a strong focus on sustainability in all cleaning processes, with wetcleaning seen as a major factor in the UK market. However, as this year’s Texcare showed, while there is a “greening” trend away from the potential health and environmental impact of perc, it would be wrong to say that wetcare is the only way forward for drycleaners in the future.
Two of LCN’s trade association partners for the recent LCN Awards 2016 were the Guild of Cleaners and Launderers and CINET, the International Committee of Textile Care. They have allowed LCN to use the findings from “Solvetex V – Evaluation and Performance of New Solvents”, a report issued by CINET and produced by TKT, the Dutch technical centre for the textile care industry and which was carried in the Guild’s newsletter (Issue 75).
Many chemical suppliers have developed their own solvent system. Most of the new solvent systems are based on hydrocarbons and modified alcohols, also known as glycol ethers, in different formulations. For the textile cleaner this increased availability of solvents on the market makes it difficult to select the optimal cleaning system for their use. The purpose of the TKT review is to provide an overview of the main properties and characteristics of the solvents, based on public test results of research institutes and test reports made available by the suppliers.
The recently introduced solvents are Ktex, Arcaclean, HIGlo, Intense and Sensene. These solvents are available besides established solvents like perc, hydrocarbon solvent (HCS), Solvon K4 and GreenEarth, evaluated in the Solvetex III study. Besides new solvents, alternative technologies are developed for professional textile cleaning like wetcieaning (evaluated in the Solvetex IV study).
Properties of the new solvents
One of the major differences between perc and the alternative solvents is the flammability. Perc is non-flammable while the others are flammable, requiring Class 111A equipment with safety precautions. The volatility of the solvent is important for the energy required for distillation and drying. The higher the vapour pressure and lower the boiling point, the easier it is to evaporate the solvent. This is often reflected in the drying temperature and cycle time.
The density of the solvent and solubility of water is important to manage the water amount in the solvent. Modified alcohols or glycol ethers have a good interaction with water. Attention is required to keep the moisture content well controlled.
Differences in boiling point and solubility in water of the components of a solvent formulation can cause changes in the formulation after distillation and water separator. The composition and stability of the solvent should be checked regularly.
Cleaning properties explained
In the drycleaning industry the kauri butanol (KB) value is adapted as a value for the “power” of the solvent. Only a small part of the cleaning properties is related to the KB value. The cleaning power is a total result of the physical-chemical properties of the solvent and the type of stains.
The KB value was original developed to evaluate the behaviour of petroleum fractions measuring the turbidity when titrated into a kauri butanol standard solution. The cleaning properties of a solvent are determined by the
viscosity, density, surface tension and chemical composition.
The evaluation is based on public test results of research institutes and test reports made available by the suppliers. The performance is based on comparison of the new solvents with perc and hydrocarbon.
The energy use of the alternative solvents is higher compared to the energy use of perc, but is in general comparable with the energy use of HCS. This is mainly due to the energy needed for the drying and distillation (if available) processes. The same applies for the water consumption. The use of cooling water for the new solvents is higher than the cooling water for perc but comparable to the cooling water consumption of HCS. Reuse of cooling water from the drycleaning machine in the laundry process is recommended to reuse the energy and water. The exact figures depend of the machine configuration and process parameters.
To determine the operating costs, the labour costs are the most important followed by consumption of water and energy. The energy costs in general are higher for HCS and the new solvents than for perc. The purchasing costs of the new solvents are higher compared to HCS and perc. In general, the operating costs of the new solvents are higher than perc and more or less comparable with hydrocarbon.
HiGlo is a hydrocarbon-based formulation with glycol ether suitable for regular multi solvent or HCS machines. Comparing the results of HiGlo with perc and HCS resulted in a good performance of the HiGlo solvent. The evaluation of the stain removal capacity of perc, HCS and HiGlo showed that the results are equivalent. The stains evaluated are based on oils, tannins, proteins, pigments and particles and good stain removal is reported on fatty stains and particles (carbon black). Protein and tannic stains are hard to remove for all the solvents. HiGlo showed good results on different textile materials like wool, polyester, cotton, viscose, silk and polyurethane. In perc, HCS and HiGlo PVC-coated work wear was damaged after the first cleaning. No greying and yellowing of cotton is observed after cleaning in HiGlo. The dimensional stability is good for all the materials tested. The finishing effort is comparable with that for perc and HCS.
SENSENE is a formulation based on modified alcohols. Dow (which has perc in its portfolio) has developed Sensene, in partnership with Safechem. The solvent is suitable for regular multi solvent or HCS machines. The cleaning performance of Sensene has been compared with perc and HCS for different stains on wool, cotton and polyester fabric. The evaluated stains are a variety of oil, fat, and water based stains like lanoline, sebum, vegetable oil, milk, lipstick, motor oil and mineral oil. The overall cleaning performance of Sensene is better compared to perc and HCS.Especially on polyester, Sensene has a very good cleaning performance. The greying of the fabrics with Sensene is comparable with greying with perc and lower than greying with HCS, except for cotton, which is higher for Sensene. The colour bleeding is acceptable and the results are equal compared with perc and HCS in the bath process. In the spray cleaning process the colour bleeding is higher due to an increased temperature (43C versus 20-30C for a bath process). It is recommended to run the spray cleaning process at normal temperature, as the solvent characteristics of Sensene do not need an increased temperature to achieve good results.
The solvent Ktex, produced by Bardahl, can best be described as a boosted hydrocarbon solvent. The solvent is suitable for regular multi solvent or HCS machines.
The cleaning properties of this solvent are evaluated in relation to the performance of perc and HCS, without additional detergents. The cleaning performance of Ktex is equal or better than the hydrocarbon solvent and comparable or lower than perc. Protein and tannic stains are hard to remove for all the solvents.
The results of greying and yellowing of cotton is good after cleaning in Ktex. In general the Ktex showed the same results on textile materials as hydrocarbons, while finishing of the garments can take slightly more time compared with perc and HCS.
Arcaclean, produced by Arcane Industries, originates from the metal degreasing process. This new solvent was developed to be as efficient as perc and to be classified as non-hazardous for humans and environment (GHS/CLP regulation). It is a mixture of several glycol ether solvents and about 2·3% water. The density of the solvent is 962 kg/m3, slightly lighter than water with its 997 kg/m3, Until a certain amount, the solvent can be mixed (miscible) with water, resulting in a difficult water separation. The system, patented by Arcane Industries, does not use a water separator, and uses distillation to purify the solvent and remove excess water.
Specialised drycleaning machines are developed with ILSA. Evaluated in comparison with perc and HCS and used on stains based on oils, tannins, proteins, pigment and particles, the performance of Arcaclean is equal to hydrocarbon and perc. Especially good results are reported on the removal of glue and egg yolk, while protein and tannic stains are hard to remove for all the solvents. The overall results of cleaning different textile materials like wool, polyester, cotton and viscose are good with slight decolouration for acetate and silk.
The dimension stability is acceptable and comparable with HCS.
The solvent Intense from Seitz is a boosted hydrocarbon solvent formulated with glycol ethers. The solvent is suitable for regular multi solvent or HCS machines. The solvent has a KB value of 73 and a flashpoint of 64C, which is slightly higher compared to the standard hydrocarbon solvent due to the glycol ethers the solvent has the ability to take up some moisture. This makes it easier to remove water-soluble soil and stains from the fabric. More on cleaning performance will follow.
The new solvents are all formulations based on hydrocarbons and/or modified alcohols. The review of available documentation shows the new solvents provided a good cleaning performance for the garments tested.
Overall, these can be seen as a sound alternative to perc in the future, given that dress habits, textile materials and type of stains are changing for the textile cleaning industry.