Avoidance of solvents in natural colors

An ecological management conception of a  
producer of natural paints  

Lecture by Adolf Riedl, Manager of Sehestedt's Natural colors, in the Department for Nature and Environment on the occasion of the campaign „Concerted Action of Ecological Technique and Economy - Opportunities for Environment and Economy" - Presentation of examplary environmental activities on Oct. 6, 1994 in Heide.  

Presentation of my firm „Sehestedt's Natural colors"  

Assisted by six employees I have been producing 90 different products since 1982: floor oils, wallpaints, varnishes, glazes, floor adhesives, care waxes, cleaners ... 

It is the essential aim of our enterprise to utilize raw materials from regenerating resources as far as possible. Where this is not possible, as with chalk, we utilize only raw materials not polluting the environment, neither when produced, manufactured, applied nor finally disposed of. 

The production of 90 different products offered in up to four different container sizes requires a high degree of cooperation in such a small enterprise. Each employee must give of his best and cannot expect to do assembly-line work or wait for directives. 

Further participation of the employees in the decisions of the enterprise could not be realized as none of them was prepared to take the risks. So the structure of the enterprise is traditionally hierarchic but the necessary division of labor is not experienced as negative by none of them. There has always been a strong sense of community. 

We are keeping close contact to our customers which is very advantageous when new products are developed and ways of application changed. 

Normally it takes two years for an industrial product to be developed and put on the market. We only take a few weeks. So it could be said that our smallness is our strength. 

Today's advancing concentration of capital and with it constantly increasing enterprises, the conception of my firm cannot be thought of as retrogressive. On the contrary, I am planning to have small paint firms built regionally (Franchise system) in the future that will keep contact to the customer, manual worker and user. They will be a counterbalance to the industrial giants. 

2. History of Natural Paints 

It is known that I am not the only paint producer to produce this way. Twenty years ago a small group of students around Lüneburg started to produce waxes and oils after old recipes that were soon sold well because of thegeneral state of uncertainty the damages caused by wood protecting products had caused. Experts smiled, laughed at them and made them look stupid. At that time - only a few years ago - an unreflected belief in progress prevailed that was not called into question before our present time. 

Quite a series of firms developed from the first one. They are now all producing after the same methods that differ only slightly from the basical recipes. 

The share of the german market of natural paints still does not exceed 3%. The rest is covered by chemical industry. But the impulse of the producers of natural paints has had quite an effect in the ecological movement. Not least because of the emissions of solvents and other ingredients in paints , the ecological crisis was clearly felt and smelt with one's own nose. 

3. Ingredients of Natural Paints 

What is the difference between a natural paint and a chemical paint copied after it? 

Basically all paints, adhesives and care products consist of: 

1. Binders ( i.e. linseed oil or acrylate ) 
2. Filling material and active substances ( chalk or titan dioxide ) 
3. Color pigments ( soil colors or sythetical colors ) 
4. Solvent ( natural turpentine from conifers or oranges or else turpentine substitute) 
5. Auxiliary materials as solvent agents, preservative and drying agents 
    ( casein, synthetical emulsifiers ) 

Often a raw material can be used as well as binder and active substance, pigment etc. It depends on what materials are used, how they react with each other and what effect they have. 

From the ecological point of view all products made by Man ought to imitate Nature, i.e. they should not disturb the ecological balance neither during production, use nor disposal. Each raw material should be checked before its use referring to these three criteria. Mostly the result is that using raw materials from regenerating resources is safest. Mineral oil is also often called a natural material - it does not come from the Moon or Mars - but it will not regenerate before 20 million years. All plant oils as linseed oil and wood oil comply with the three ecological criteria and they regenerate. Of course the reproduction process of the plants must be well planned. Flax - linseed oil is pressed from its seeds - must not exhaust the ground by uncontrolled large scale cultivation. 

There are, however, among the ingredients of natural paints also raw materials as chalk, rock meal, talcum, and soil color pigments that do not regenerate. But these natural raw materials do not disturb the ecological balance at all (s. a.). 
The solvent turpentine, produced from coniferous resin, was replaced by the surrogate turpentine substitute, a derivate from mineral oil. This example can show us clearly what it is involved with. The actual solvents in the turpentine substitute are benzole, toluole and xylole. These so-called aromates are carcinogenic. On one hand these petrochemical materials make us independent from Nature, from the unstable prices of raw materials (due to ungaranteed results of crops) , on the other hand they produce enormous health, technical = ecological problems. This is quite different with the products of natural paints producers. A wood surface treated with natural oils always proves to be breathable, steam permeable and absorbent, and it feels good to the touch. A wall painted with a casein natural resin paint improves the climate in the room. A natural resin latex adhesive does not give off any toxic gases and a floor treated with beeswax reduces electrostatic charging and with it dust development in living rooms. 

Trying to give the consumer an indication to ecological products, legislators in Germany have created the label „blue angel". It is meant to indicate that the product is more ecological than its predecessor. This means that natural paints and bicycles cannot be given the label, unlike toilet paper that has been produced with reduced use of energy. The concept of the blue angel was invented subsequent to the oil crisis. Suddenly everybody had realized that mineral oil could become a more expensive raw material. Instead of sparing no effort to research into alternative energy and sources of other raw materials, it was decided to economise. How inconsistently this is realised is to be seen with the so called blue angel water varnishes. Here the solvent turpentine substitute was replaced by 90% with water, but acrylates - from mineral oil - were used; their energy use during production is very high and they still contain 3 - 15% turpentine substitute and glycole with all their dangers to health. All this is however not declared on the label. 

4. Solvents in Natural Paints 

It is a strictly respected rule for all producers of natural paints to declare all ingredients on the label. All environmental associations have always been calling for this claim. 

What do labels tell us about the solvents in natural paints and what else is in the containers? Very soon the different firms started quarelling about that. 

For processing resin, wax or thick oil a solvent is necessary. Here too, Man used to imitate Nature. To protect injuries some trees produce a thick juice - balsam, balm ( Hebrew: agreeable, pleasant ) . Balsams are solvents from solid resin substances (resin alcohol, resin ester, resin acid, highly molecular hydrocarbon) in etheric oils (i.e. turpentine oil). In the air the thick, viscous balsams harden gradually as the volatile oil evaporates and often clear, glass-like amorphous masses remain. To obtain resin and the volatile substances, the trees, mainly conifers, are injured, slit. From the now flowing thick turpentine, balsamic turpentine is produced by destillation. The remainder is colophonium, a splintering resin of inferior quality. Balsamic turpentine is an excellent solvent for all resins and waxes. Unfortunately it irritates the skin. The so called turpentine allergy is thought to be connected with its content of caren and pines known to have an excem producing effect. Therefore balsamic turpentine has been taken into the MAK list. 

During the first years the producers of natural paints were mainly criticized because they were using balsamic turpentine. Very soon almost only orange turpentine was used. All products smelled strongly of lemon, orange and grapefruit. For the hobby worker , an attractive alternative to the bad smelling BTXes. But I am mainly producing for the manual worker. If a carpenter or painter works all day long inside a room, he will have a headache in the evening. This is why I looked for a healthier alternative for my customers. Petrochemistry offers an aromate-free turpentine substitute containing no solvents; addition of 5% balsamic and orange turpentine serves the technical aim. Most producers of natural paints did something similar. It is an ecological compromise. 

5. Oil in Water 

Producing a solvent that is free from hydrocarbon is certainly the best solution. It is, however, connected with many difficulties particularly if the producers have taken up the cause of using nothing but raw materials from regenerating resources. They all agree that water is the best thinner available at all. But the question is how to get oil or fat, wax or resin into water so that they will remain there stable. Here Nature has shown us again how to do this. In milk for example fat pellets are finely spread in water. This is an oil-in-water emulsion that can be diluted with water in any ratio while being relatively stable. 

Digression: 

An emulsion is a dispersion of two non mixable liquids, i.e. water and oil, the internal open, disperse phase of which is spread in the external, closed phase - in the dispersion material - in form of finest drops. While lots of small drops are developed, the surface of the spread liquid is considerably increased. 

The small drops have an energy considerably higher than the coherent oil phase. This energy, also called surface tension, counteracts the spreading of the oil phase and is directed parallel to the surface. This means that work is necessary to achieve the state of an emulsion. 
This work can be supplied by mechanical energy, in most cases with a mixer, or else by the physical-chemical energy of an emulsifier. In practice, however, a combination of both kinds of energy is applied. In cases where the phases are solid, i.e. wax, a third form of energy , warmth is used, as the phases that are to be emulsified must be made liquid before emulsifying. 

The mechanical work can be considerably reduced by decreasing the tension of the surface. 

If an emulsifier is produced merely with the help of mechanical energy, there will be a dispersed system in a very unstable state. The small particles will flow together giving up the emulsified state to be finally seperated again. An emulsion must, however, be sufficiently stable against mechanical, thermic and temporal influences. To achieve this, something is needed to avoid the separation of the two phases. Stabilisers and/or emulsifiers are the solution. 

It is very important to find the proper emulsifiers and stabilisers and to mix them in the correct ratio to be able to develop a stable emulsion. From the ecological point of view stabilisers should be predominant over emulsifiers that ought to be used as little as possible. Emulsifiers reduce the tension of the bordering surfaces between the two phases and so the emulsion produced is stabilised. This is actually the main function of emulsifiers, it is even more important than primary spreading as for this purpose mechanical means are sufficiently available. 

The oldest emulsifiers are casein and hen's eggs. Egg yolk is an excellent emulsifier due to the different substances it contains. It can bind about 700% oily substance and it is the most efficient emulsifier known. 

For the production of a cream basis , to start with wool fat was used as an emulsifier in 1885. Apart from wool fat (lanolin) fat alcohol of higher valency and saponified beeswax are suitable as emulsifiers, all of them being active compounds of bordering surfaces and therefore tensids. They are mainly the same substances as are used in cleaners and must therefore be water soluble. That is why too much of this substance in paints and care products for wood and metal will always be a mistake because the emulsion will be washable. 

Stabilisers can stabilise the mechanically produced emulsions by increasing their viscosity , by thickening them and producing mechanically stable films on the bordering surface. Many thickening agents ( hydrocolloids) are able to interact with the emulsifying particles by being taken up by the particles that are to be protected. They also increase either their charging or strengthen their soluble shell or even both. Hydrocolloids are natural materials like gum arabic, tragant, agar-agar, various celluloses, polyacrylates being used most frequently today, products of petrochemistry with their high energy use during production, and polysaccharides. 

6. Chitosan 

Something was necessary to make oil, resin and wax water dilutable but resistant to water and friction like a paint after drying. 

In connection with the essay on adhesives commissioned by the Department of the Environment of Schleswig-Holstein, chitosan provided a solution. The possibilities for the application of chitin, chitosan and their derivates in Schleswig-Holsteins economy were then examined by Prof. Peter on behalf of the Minister for Nature, Environment and Land Development of the Land Schleswig-Holstein. 

Chitin is a natural, nitrogenous polysaccharide. It occurs in numerous organisms, in particular, however, in insects, crustacea, and fungi. Chitin is after cellulose the second most frequent polysaccaride. 

It is won particularly in Japan and the USA from wastes of shrimp fishing. In Schleswig-Holstein, too, it is thought to use the shells of shrimps instead of disposing of them as before as waste or fodder.. 

The highly cationically charged polysaccharide chitosan is won from chitin by alcaline hydrolysis of the acetylene groups. Chitin is non toxic whereas the acute toxicity of chitosan is estimated as very low. It has an antibacterial and anticandida effect. Both polymeres are biocompatible and biodegradable by natural enzymes. Research in connection with chitin/chitosan has been strongly intensified worldwide. Its application range is cosmetics, food industry ( precipitation of protein and cheese whey treatment ) and agriculture ( coating of seeds and fruit ) *, medicine ( the basic chemical structure of chitosan being similar to that of skin, hair and cellulose) and water treatment. 

Chitin and chitosan are well biodegrable by naturally occuring enzymes. „ It can therefore be expected that polysaccharides being nitrogenous natural material may be supplied to composting. Unlike numerous synthetical mineral oil products that are not or hardly biodegrable the argument of recycling to prevent refuse dumps can be dropped." ( M.G. Peter, Chitin, Chitosan and theit Derivates, Kiel 1992, p. 10 ). 

With chitosan all natural waxes and oil can be made water dilutable. The solid state of products based on turpentine could be maintained. Partly completely unexpected side effects resulted as ten times faster drying of floor wax. Just imagine chitosan as a large polymer with many arms. Each arm keeps hold of the water. The enormous capability of absorbing water enables fast drying on the surface allowing polishing of wax after 10 minutes' drying. 

As chitin is the second richest polymer in nature after cellulose its application in exchange for cellulose for the production of natural paints is obvious, all the more as the production of cellulose is ecologically problematic ( cutting down Canadian woods, sewage pollution etc.). Chitosan has made Sehestedt's Wallpaint easier to paint, improved its rubb-off fastness and absorbability. 
I was rewarded the Prize for Ecological Building in Schleswig-Holstein for improving my wallpaint in 1991. An even greater success was the use of the polysaccharide chitosan as emulsifier and stabiliser with the production of solvent-free glazes, varnishes, and wax care products. Sehestedt's Natural Colors has discovered this highly interesting natural raw material for its natural products. 

7. New Products 

When a new paint, adhesive or care are conceived, it depends what criteria, demands are made on the product. A varnish or glaze for exterior use must be waterproof but also steam permeable. Just imagine a wooden window. Windows are high impact parts of a house. The sun heats the wood enormously with the result that it shrinks and bursts. Rain has now a large target and can wash the wood out and groove it. In winter the ice will break up the wood in the cracks and its destruction takes its course. 

Many lines were followed in the past. It was the wrong track to protect wood with a hard synthetical resin varnish. After some time, when the necessary softening agents leave the varnish, hairline cracks occur. Water can penetrate. On the other hand such a synthetical resin varnish is so steam impermeable that steam trying to find its way out of the house remains behing the varnish. In winter the frozen water will let the varnish flake off. Not long ago industry went over to applying thinner coats as a glaze. But basically with the same negative results. Better results were not achieved before water dilutable glazes with polyacrylates were used. 

I want to go one step further and produce water dilutable glazes with polysaccharides, precisely with chitosan. I have already produced a white and colored water varnish for interior use. Outdoors its water absorbency is still too high. Together with the University of Kiel we are looking for suitable chitosan and other additives for this purpose. This research project is supported by the German Federal Foundation of the Environment. In 1993 I was awarded the Prize for Ecological Building in Schlewig-Holstein for a water dilutable floor wax, particularly advantageous for machine application due to its fast drying capability. 

The numerous possibilities for application of chitosan is shown in the publication of my patent DE 4303415 A1 of the German Patent Office from which I am quoting: „The invented emulsions can be applied for wood protection inside and outside the house, for antifouling yacht underwater paints, for artistic paints, and in the household for various care products as well as for cosmetics in connection with suitable raw materials. With the invented product many glazes and care products for wood, cork, stone and metal having contained solvents can be produced with chitosan as water dilutable and solvent-free paints. As chitosan is an excellent moisturizer these paints and care products are especially suitable for the care of wood surfaces and for the sector of cosmetics. Chitosan improves adhesion and water resistance of oil and wax films. The products are more resistant to rubb-off, better paintable and simultaneously preserved. They are not only ecologically better products but can also be produced more economically." 

*To finish I would like to mention another highly interesting new application and product group I am concerned with at present. It is based on neemoil, a plant oil from the crushed seeds of the neemtree ( azadirachta indica ) originated in India but in the meantime also being cultivated in Africa, Australia, Central and South America. The composition of neemoil depends very much on the origin of the oil. Its essential compounds are different stereoisomeres and derivates of azadirachtin (50 - 4000 ppm). Beyond that it contains many limonoides and different disulphides, causing the smell of garlic of the neemoil. 

Neemoil can be used as natural insecticide for protection of wood and plants. This effect is due to azadirachtin. It causes inhibition of growth of the larva. It is non toxic for mammals. The oil is superior in its effectiveness to the pure active substance due to the stabilizing effect of the oil, respectively its content of other effective substances. Watery seed extracts or emulsions of the oil are traditionally used as insecticides in India and are an important alternative to the use of sythetical neurotoxines. Approx. 80 000 tons/year of neemoil are produced in India mainly for the production of soap though. With chitosan emulsified neemoil can be a highly effective pesticide for the woodworm, house longhorn, and other beetle larva. It may also be used in forestry against bark beetles and in agriculture as seed coating preparation. Even allotment holders may so have something that will keep worms away from their apples without needing to be afraid of theit children or grandchildren eating them in autumn.