AIR3-CT94-2063 Vegetable Oils and their Fatty Acid Esters (VOFA) as Substitutes for Organic Solvents in Industrial Processes (VOFAUSE)

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AIR Cluster IV - Oils and Fats : Fine Chemicals : Paints/Coatings/Plastics : Process Engineering : Vegetable Oil/Fat

	Proposal No:	AIR3-CT94-2063
	Date Prepared:	September 1999, April 1998
	Source:	Final Consolidated Report April 1998 2nd Annual Progress Report 1997

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Final Consolidated Report April 1998

Summary

Introduction
Various industrial processes use solvent-based products for cleaning. However, during use, these volatile organic solvents evaporate into the air, endangering workers' health and contributing to environmental pollution. Fatty acid esters derived from vegetable oils represent a new generation of emission free, non-toxic and environment friendly cleaning agents based on renewable resources. The core objective of the project VOFAPro was to test fatty acid esters of vegetable oils (VOFA) as substitutes for the organic solvents currently used in industrial cleaning processes.

VOFAPro investigated esters based on vegetable oils such as rapeseed and coconut oils. The research was focused on the description of the technical properties and cleaning abilities of fatty acid esters with particular regard to metal surface cleaning and removal of paints/inks. In addition, a life cycle assessment and studies of the environmentally important properties of VOFAS, technical experiences of surface cleaning in selected industries and the availability of vegetable oils were carried out.

Scientific objectives
The main objective of the project was to test less hazardous substitutes for the organic solvents currently used in industrial cleaning processes. The suggested alternatives to these organic solvents are fatty acid esters of vegetable oils (VOFA). The esters are based on vegetable oils such as rapeseed and coconut oils and have the potential to be used as substitutes in cleaning processes. The VOFAPro project was set up to investigate these VOFAS. The research was focused on the description of the technical properties and cleaning abilities of fatty acid esters with particular regard to metal surface cleaning and removal of paints/inks. In addition, a life cycle assessment and studies of the environmentally important properties of VOFAS, technical experiences of surface cleaning in selected industries and the availability of vegetable oils were carried out.

Renewable resources for cleaning purposes
Natural oils and fats are themselves esters. In general, pure vegetable oils have high viscosities, and are not sufficiently stable against oxidation. To improve their chemical and physical properties, fatty acid esters are synthesised by reacting fatty acids derived from vegetable oils with alcohols (esterification/transesterification). Both, production of alcohols and esterification/transesterification are well-established and adaptable standard procedures in industrial chemistry. Industrial capacity for producing esters can be adapted to market needs to produce specially designed products.

Chemical characteristics and cleaning ability
The measured physico-chemical parameters indicate that VOFA products have good cleaning potential. They have low viscosities which mean that they are easily applied to the objects which have to be cleaned. They have surface tensions in the same range as other organic compounds, which means that the wetting ability of VOFAs is as good as conventional solvent based cleaning agents. Several models for estimation of different physico-chemical properties of VOFAs were investigated. Calculation of critical parameters, density, normal boiling point temperature, vapour pressure, surface tension, viscosity, solubility behaviour and flash point temperature has been performed within the project. Models which provide a good description of vegetable fatty acid esters have been found for density, boiling point temperature, surface tension and viscosity.

Metal surface cleaning and VOFA properties
VOFA products can be used with a variety of cleaning techniques, i.e. manual, immersion and spray. These products cannot be used with vapour degreasing facilities since the technique is dependent on the volatility of the cleaning agent. The conditions of use (duration, temperature, etc.) must be adapted to reflect the nature of the dirt and the degree of cleanliness required, etc.

VOFA products and removal of industrial dirt
VOFA products are effective against mineral oil based products (such as lubricants, temporary protectives, cutting fluids, etc.), grease, Lanolin (a compound particularly resistant to cleaning) and certain paints. In common with organic solvents, VOFA products have limited effect on oxide layers or baked on dirt. Cleaning with VOFA products result in an oily residue on the surface of the cleaned object. This residue may, in some cases, act as a temporary protective layer. Further processing, however, necessitates the removal of the residue. This can be accomplished in a number of ways - wiping, wiping with an organic solvent such as white spirits, evaporation (only possible under certain conditions) or emulsification of the VOFA product followed by a water rinse. The degree of cleanliness required for the application of water-borne, solvent- borne and conversion coatings is attainable with VOFA products if the ester residue is removed. The long-term durability of the coatings may be affected by incomplete removal of the residue.

Compatibility of VOFA products
Vegetable oil based fatty acid esters are not inherently corrosive towards metals. Stainless steel and aluminium are the most resistant whilst zinc coated or zinc containing metals are attacked by VOFA products containing some free fatty acid. VOFA products can cause the swelling of rubber and the leaching of plasticisers from certain plastics, however the effect in general is comparable to that of organic solvents. VOFA products are not volatile, which in turn means that they have high flash points and are neither flammable nor explosive by nature. For this reason there are no special handling requirements. However spillage must be dealt with promptly since VOFA products are oily and can make surfaces slippery. Cleaning in connection with paint and ink VOFA products are effective cleaners if they can solubilise or mix with the material to be removed.

VOFA products can be used as cleaners in connection with the manufacturing of paint and ink, if the product is soluble or miscible with the VOFA. This is normally only applicable if the cleaning is performed manually and the equipment is resistant towards the VOFA products. VOFA products can be used as cleaners for application devices such as brushes and rollers in connection with alkyd, polyester/melamine and chlorinated rubber. VOFA can also be used as cleaners in connection with uncured systems, which have to be cured by heat, oxidation or UV-light, by dilution of the system. VOFA products can also be used as cleaners for coated surfaces if the binder system is unaffected by the VOFA. VOFA products can also be used as cleaners for equipment in application processes. This has been proven in offset printing since, in general, VOFA are miscible with the solvent system of the ink.

VOFA with an emulsifier or as a microemulsion will open new areas for a use of VOFA as cleaning agents. The above guidelines for VOFA use are to a large extent based on solubility aspects. In most cases the binder system dictates if VOFA can be used, but it is also necessary to consider the miscibility with the solvent system (if not a 100 % binder system).

Environmental benefits
Within VOFAPro the (potential) environmental effects caused by the use of VOFAs and organic solvents have been studied by means of an environmental Life Cycle Assessment (LCA). In some cases, the substitution of organic solvents by VOFAs would clearly be an ecological improvement. From the study of the various raw materials it appears that a coconut oil based methylester would, for the time being, be the most favourable option. Several improvements can be made within the VOFA life cycle. These involve, for example, a more complete utilisation of coconut by-products and a more controlled use of fertilisers in rapeseed cultivation.

Mild environmental effects
Biodegradability tests were performed in order to characterise the possible environmental effects of VOFA. All tested products were rapidly degraded by the sewage treatment bacteria used in the tests, indicating that these esters are readily biodegradable and as such are expected to be rapidly degraded in the environment. With regard to the aquatic toxicity, there proved to be no acute effect on the Daphnia test organisms, even in saturated ester solution. This clearly shows that the toxicity of these compounds is very low. Finally, an environmental risk assessment of some fatty acid esters was performed. The result shows that there is a very large safety margin between concentrations likely to be present in the environment and those expected to lead to effects on aquatic organisms.

Conclusions
The overall results of the pilot tests are positive and encouraging for the use of vegetable esters as industrial cleaning agents. Their physical and chemical properties make them suitable as cleaning agents in a range of industrial applications. The products evaluated performed extremely well despite the fact that they were almost entirely pure fatty acid esters and not formulated cleaning agents. Additives such as emulsifiers can be used so that the cleaning agent can be easily removed with water. Mechanical energy, temperature and duration of process are ways to optimise the efficiency of the cleaning products. To date, offset printing has the greatest success with VOFA. The area with the greatest potential for successful substitution of organic solvents by VOFA products in the future is the metal sector, i.e. cleaning and maintenance of equipment where no further treatment is required or as pre-cleaners to remove the bulk of the contamination. In the paint and ink area the basic conclusion is that if the binder system of a paint/ink is soluble in VOFA it will be possible to dilute a wet and in some cases solubilise a semi- wet film. For dry coatings the binder system dictates if VOFA can be used as a cleaning agent. VOFA products do not pose a health risk for the workforce and can be considered to be environmentally safe. Dissemination activities within the VOFAPro project showed that companies, unions and governmental institutions are becoming increasingly interested in further testing and information on the potential substitution of organic solvents by products based on fatty acid esters.

Copies of a VOFAPro Bulletin, a VOFAPro Guide and workshop documents are available from the VOFAPro partners.

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2nd Annual Progress Report 1997

Introduction
The core objective of this project was to find substitutes for the organic solvents which are currently used in industrial processes, such as cleaning, coating and degreasing. The suggested alternatives to these organic solvents are fatty acid esters of vegetable oils. The VOFAPro project was set up to investigate these "VOFAs" (vegetable oils and their fatty acid esters) with respect to commercial and environmental considerations (availability, classification, life cycle etc.) as well as their compatibility with other materials and their cleaning ability. The overall objective of the project is to make VOFAs more attractive to industry as substitutes for VOCs (volatile organic compounds) in specific cleaning processes.

Background information
The experimental work for this project is still ongoing. Preliminary results, of the investigation of the suitability of VOFAs as cleaning agents, confirm their potential in several areas. This potential does, however, have limitations. Availability of vegetable oils is subject to considerable fluctuation which is reflected in the world market prices. In the eighties and early nineties due to a remarkable increase in world wide production, the availability of vegetable oils was quite good and prices were stable. Increasing demand in the nineties led to a shortage of vegetable oils. However, an increase in oil seed yields, which is expected in the future, would result in availability and prices of vegetable oils that are conducive to their industrial use. The industrial capacity for the esterification of the vegetable oils (and the production of the alcohols required for this process) can be adapted to market needs quite easily and therefore place no restrictions on the availability of vegetable esters. Rapeseed methyl ester (RME) has become readily available and inexpensive due to the large quantities of rapeseed grown in Europe over the last few years.

Substitution is important for the reduction of the amount of solvents used, which for example in EU12 in 1990 was 4,920,000 t. The uses of solvents and the quantities required are sector specific. Metal industry uses solvents for cleaning purposes in manual, vapour, ultrasonic/dipping, spraying - often as completely automated cleaning processes. Further treatment, i.e. coating, requires a high degree of surface cleanliness. The metal services industry is similar to metal industry in many respects, with the exception that manual cleaning is more frequently used. Also, the likelihood of the parts to be cleaned being made from both metal and non-metal materials is greater for the metal services industry. In the paint and ink industry, large amount of solvents are used not only as cleaning agents but also in the manufacture of paints.

For solvent based paints, quite often the same solvent is used for the cleaning process and as a base for the paint which means that the cleaning agent can be mixed with the paints. Another use of solvents is in the cleaning of brushes, rollers (both used in manual and automatic application), jigs and conveyors (automatic application). In the printing industry organic solvents are still largely used in open or semi-open containers for cleaning purposes. As with the paints, the cleaning agent is often the same as the solvent in the ink. In offset printing oil based inks are used. AII and AI solvents have been used for most cleaning purposes for a long time, nowadays AIII solvents are commonly used. High boiling solvents as well as ester-based cleaners are also widely used. In flexographic as well as in gravure printing, inks are generally solvent based but some water borne ones are also used. For cleaning purposes toluene is most the widely used solvent. In screen printing the most common solvents are glycol ethers. They are often removed by organic solvents but can also be removed by water. Analysis of conventional cleaning technology shows that the greatest exposure to solvents occurs with the use of manual cleaning in the metal and metal services industries and in offset and flexographic printing.

Activities
The current cleaning technology in use in the different industries was investigated by distributing four industry specific questionnaires in the participating countries and analysing the results. The results of these questionnaires indicated the problems that occur with the current technology and were used to identify the areas where a possible substitution with VOFAs seemed reasonable. One important result of this investigation was the finding that 40 percent of the 136 cleaning processes described in detail by the questionnaires were manual. The cleaning of steel, to a degree of cleanliness that would allow a subsequent coating process, was of the greatest importance for the metal industry. With regard to the use of VOFAs, it is an important result that in 23 percent of the processes described oily residues are acceptable and may even be desirable in some cases. This is important, since VOFAs do leave a light film that would have to be removed mechanically or by other means, if oily residues are not acceptable. This is the case in the metal industry where only 14 percent indicated that oily residues are acceptable. Therefore, in order for VOFAs to be used by the metal industry they must be removed effectively prior to further treatment. This requirement was dealt with under cleaning ability and technical applications.

Political pressure arising from environmental concerns (e.g. effects on the climate), has resulted in increased interest, amongst large companies, in less harmful alternatives to organic solvents. 67 percent of the surveyed companies are considering a reduction in the use of organic solvents and 69 percent are looking for information on alternative cleaners. The prospects for VOFA products are good provided the products could be developed and adapted to suit specific applications. The results of these activities have been important in understanding the needs of industry and in supporting the decisions, which have been made in other parts of the project.

To allow for the definition, classification and modelling of VOFA products, 20 pure esters (including fatty acid esters and lactates) and 15 commercial products were chemically characterised. Boiling points, surface tensions, vapour pressures, densities and viscosities have been measured. This data will be the basis for the classification of VOFA in keeping with EC labelling requirements. The measured surface tensions are typical of organic compounds (2040 dynes/cm). The measured viscosities for the esters have been found to be extremely low, an important consideration in the cleaning of close-packed parts and parts that are not easily accessible.

Several models for the estimation of the physico-chemical parameters of pure compounds have been found in the literature. Estimation of the pure VOFAs was performed using some of the models. The most common input parameters for the models are the liquid density and the boiling point. The need for reliable values for these two properties is therefore obvious. VOFAs have very high boiling points and vapour pressures. To measure the boiling points at atmospheric pressure, two new methods have been developed in the course of the project. The results of both methods have been compared and are in good agreement.

For the cleaning tests (metal/metal services industries) four typical test dirts with increasing resistance to cleaning have been defined. The cleaning ability of four different esters has been tested. Tests with emulsions are planned but not yet completed. While all of the tested esters removed a thin oily film quite easily, differences between esters have been shown with the tougher dirts. With regard to the removal of the esters prior to coating, wiping with a clean cloth gave good results based on the appearance of the coating. Oven drying at one hundred degrees was successful for some of the esters, they could be removed to the extent where coating was possible. The cleanliness was assessed by applying various coatings to cleaned panels and subjecting them to durability and weathering tests. In general coating with water borne paints performed better on humidity testing than solvent borne paints. Electroplating, which is extremely sensitive to surface cleanliness, failed in all cases. The results of the salt spray tests showed on average a 20 to 30 percent increase in the loss of adhesion compared to the standards (solvent wipe with white spirits). Cleaning test with paints and inks have been designed and performed.

The ability of VOFAs to solubilize binders was tested to determine the Hansen Solubility Parameters: Solubility tests with standard dirts have been carried out. The ability of VOFAs t solubilize is decreases with increasing size of the ester group. While VOFAs can solubilize some binders, for other binders the effect can be better described as swelling. With regard to standard dirts the esters are according to theory not entirely solubilising the dirt, but still mixing and mechanical forces might be enough to lift of the dirt. As the cleaning tests show that the standard dirts can be removed by most esters without vigorous mechanical force, it can probably be noted that mixing between ester and dirt is sufficient for most cleaning tasks. The solubility behaviour is also being tested to assess the compatibility with other materials used for tubes and fittings. Preliminary results point to some swelling with all kinds of rubbers. However experience from offset-printing (rubber blankets) show, that this swelling, in many cases, is lower than with conventional HC-solvents, and does not cause problems in practice. Corrosivity tests (supported by measurements of acid number) showed a high corrosivity toward zinc which can be directly related to the acidity of the ester.

A life cycle analysis of two VOFA products and a de-aromatised hydrocarbon product has been performed. A direct comparison was made, based on 1000 kg of both the VOFA and the hydrocarbon products, since there was insufficient detailed practical experience available for the definition of the functional unit. The resulting data implies a comparable degree of negative impact during production for both types of products, albeit in different areas. While ester products are ecologically more favourable with regard to depletion, toxic effects on humans and VOC-emission, they are less favourable in aspects related to agricultural practices (use of fertiliser, water hazards, solid waste, and eutrophication). In practice recycling of the cleaners will greatly effect the respective ecological performances. However the internationally agreed LC method does not include an assessment of biodegradation, occupational health hazards, etc., areas where VOFAs perform better than organic solvents. Also the actual amount of VOFAs required may be significantly less than the amount of solvent required (the amount of solvent used is influenced by evaporation during use), which would place VOFAs in a more favourable light.

The assessment of biological degradation, bio-accumulation and toxicity all gave very favourable results for VOFAs. VOFAs are environmentally safe. Most (straight chain) esters are degraded completely in less than 10 days. It is assumed that branched esters will take somewhat longer however this has not been confirmed.

Dissemination
This has included articles have been submitted for publication and several of the partners have attended meetings where some of the aspects of VOFA-use have been presented and discussed. In association with the project, several industrial trials have been carried out in various countries that have been observed and documented. The results of these trials are in good agreement with the findings of the laboratory work. VOFAs could be used successfully in a certain fields including the metal services and the metal industry.

Conclusions
Many of the issues regarding the properties of VOFAs have been addressed. The assessment of the cleaning ability is in the final stages of completion. Emulsions and microemulsions, which are both very promising as cleaning agents, will be (has been) tested during 1997. The ability of VOFA to remove paint in different states of dryness and cure will be examined over the winter months. Also a comparison between the mathematical models and the experimental data for the commercial products will be performed during the next reporting period. A picture is emerging of VOFAs as powerful cleaning agents which are suitable for many applications. This justifies a thorough dissemination phase, with the aim of informing as wide a section of the public as possible.