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Siloxanes - Consumption, Toxicity and Alternatives

5 Alternatives

• 5.1 Alternatives to siloxanes in cosmetic products
  • 5.1.1 Neopentylglycol heptanoate
  • 5.1.2 Isodecyl neopentanoate
  • 5.1.3 Glycol distearate
  • 5.1.4 Dicaprylyl carbonate (vegetable oil components)
  • 5.1.5 Diethylhexyl carbonate
  • 5.1.6 Hydrogenated polydecen
  • 5.1.7 Summary and general experience
• 5.2 Alternatives to siloxanes in cleaning agents and polishes
  • 5.2.1 Mineral oils (tensides)
  • 5.2.2 Paraffin oils and vegetable oils
  • 5.2.3 Lipophilic tensides
  • 5.2.4 Block polymers
  • 5.2.5 Summary

The use of some types of siloxanes is regarded potentially to cause problems to the aquatic environment and human health. The investigation on alternatives has therefore focussed on product groups where the risk of exposure to humans and releases to the aquatic environment is regarded to be present.

The investigation has focused on the following product groups:

• Cosmetics;
• Cleaning agents, waxes and polishes.

The information in this chapter is based on telephone interviews with manufacturers and suppliers of both siloxanes and alternatives to siloxanes.

In the following chapter the names of the compounds when they are used in cosmetic products (INCI names) will be used. Dimethicone is synonymous with linear polydimethylsiloxane, cyclopentasiloxane with decamethylcyclopentasiloxane and cyclomethicone with cyclic siloxanes, either pure or in mixtures.

5.1 Alternatives to siloxanes in cosmetic products

The investigation has primarily focused on the siloxanes cyclomethicone and dimethicone, which are commonly used in the cosmetics industry. Cyclomethicone is volatile and is furthermore suspected to cause different types of health and environmental problems.

As mentioned in section 2.2.4 the siloxanes have many applications in the different types of cosmetic products, and the siloxanes have very specific properties depending on the composition of the compounds. Because of this it is not possible to find just one alternative for e.g. cyclomethicone, as cyclomethicone can have many different applications and compositions depending on the product in which the substance is used.

The alternatives for siloxanes must therefore be very specific, as they have to comply with the special characteristics that the given siloxane has in the given product.

The use of alternatives to siloxanes in cosmetic products is still modest. The Danish suppliers of both siloxanes and alternatives to siloxanes have so far not experienced great demand for alternatives, but most of the contacted suppliers expect an increased demand for alternatives in the coming years. The suppliers have consequently started to develop alternatives to especially cyclomethicone and dimethicone.

It has so far been a difficulty that some of the properties of siloxanes are lacking in the developed alternatives. For soaps and leave-on products (lotions and creams for skin) the siloxanes can give the product the combination 'smooth and soft feeling' on the skin combined with the effect that the product does not feel greasy on the skin after application. These properties are obtained because the used siloxanes are volatile and can give extra softness. It has so far been difficult to find alternatives that can match these properties, and especially cyclomethicone is difficult to substitute. Dimethicone is in general easier to substitute, because the same properties can often be obtained with different types of vegetable oils. A test of one of the alternatives in Table 5.1 has shown that the developed alternative can give almost the same properties as cyclomethicone in the tested cosmetic emulsion. Emulsions are regarded to be one of the most problematic products to substitute cyclomethicone from.

The functional silicone oils, which for example can be a mix of cyclomethicone and dimethicone, are even more problematic to substitute, as the mixture of the different siloxanes is made to obtain some very specific properties. Polyether-modified silicones and other types of functional silicones will give the same problem, and alternatives have so far not been regarded.

The typical content of siloxanes in the products is below 2% of the final cosmetic product, but the content can according to SPT (The Danish trade organization for cosmetics and toiletries) vary between 0.5-40%, depending on the products in which the siloxanes are used.

Table 5.1 shows identified alternatives to siloxanes used in cosmetic products.

5.1.1 Neopentylglycol heptanoate

Neopentylglycol heptanoate is an alternative to dimethicone in different cosmetic products like conditioners and leave-on products. Neopentylglycol heptanoate has the same good spreadability as dimethicone and can like dimethicone be used as solvent for other substances and emulsifiers. The substance has just been introduced in Denmark, and customers have according to the supplier shown great interest in the alternative, but the substance cannot be found in Danish cosmetic products yet.

The price of neopentylglycol heptanoate is approximately the double of the price for dimethicone, as 1 kg of dimethicone costs approximately 50 DKK per kg, while the alternative costs approximately 100 DKK per kg. The use of neopentylglycol heptanoate should according to the supplier not result in changes in the production equipment. It would though be necessary to change the packaging, due to changes in the declaration.

5.1.2 Isodecyl neopentanoate

Isodecyl neopentanoate is an alternative to cyclomethicone. It can be used in leave-on products, conditioners and perhaps also in shampoos and cream soaps. Isodecyl neopentanoate has high spreadability like cyclomethicone and gives a soft feeling like cyclomethicone. It can be used as solvent and emulsifier. The alternative is new on the Danish market and has not been sold to Danish customers yet, but customers have shown great interest in the product.

Isodecyl neopentanoate is quite expensive compared to cyclomethicone. Cyclomethicone costs approximately 45 DKK/kg, while the price of isodecyl neopentanoate is expected to be approximately 100 DKK/kg. The use of the isodecyl neopentanoate should according to the supplier not result in changes in the production equipment. It would though be necessary to change the packaging, due to the changes in the declaration.

Table 5.1 Identified alternatives to siloxanes from Danish producers and suppliers

N/A CAS No. has not been available - the substances are not included in the 1st update of the inventory of ingredients used in cosmetic products (INCI 2000)

5.1.3 Glycol distearate

Glycol distearate is an alternative to siloxanes in different types of soaps. Glycol distearate gives the product a "milk-like" appearance and contains wax that gives shine and smooth feeling to cream soaps, shower gels and shampoos. Glycol distearate can typically not directly substitute all properties of dimethicone, cyclomethicone or other types of siloxanes, which often can give a more distinct feeling of softness etc., but it has similar qualities. Glycol distearate has been used in cream soaps sold in Denmark for the last 2 - 3 years, and the use of glycol distearate is increasing.

A compound containing glycol distearate costs approximately 20 - 25 DKK/kg, but the compound only contains 20-40% of glycol distearate - the rest are other additives used in soaps. Glycol distearate is therefore economically competitive compared to the siloxanes. The use of glycol distearate instead of siloxanes will according to the supplier not cause changes in the production equipment. It would though be necessary to change the packaging, due to changes in the declaration.

5.1.4 Dicaprylyl carbonate (vegetable oil components)

Different vegetable oil components can be used in creams and lotions instead of siloxanes. One particular example of these oils is dicaprylyl carbonate. Dicaprylyl carbonate cannot directly substitute the properties of siloxanes used in creams and lotions, as the alternative does not have the foam reducing effect that the siloxanes have. But except from this dicaprylyl carbonate can be used instead of cyclomethicone, dimethicone and other siloxanes and can add softness and spreadability to the products. The product is in use in products sold in Denmark.

The price of dicaprylyl carbonate is approximately the same as for the different types of siloxanes, perhaps a bit more expensive than cyclomethicone and dimethicone. It should be possible to use the same production facilities. It would though be necessary to change the packaging, due to changes in the declaration.

5.1.5 Diethylhexyl carbonate

Diethylhexyl carbonate is an extremely spreadable and low-viscous ester oil, which can substitute cyclopentasiloxane in lotions and emulsions. A cream product based on diethylhexyl carbonate has been tested together with a cream product based on cyclopentasiloxane. The test, where 6 people in a sensory panel tested the two creams, showed that the cream based on cyclopentasiloxane was perceived by all panellists, because it feels better with respect to spreadability and soft feeling than the cream based on diethyl carbonate. If an additive was added to the cream with diethylhexyl carbonate, three of the panellists did not find any difference between the two creams, while the three remaining still found that the cream with cyclopentasiloxane was a bit lighter. The conclusion of the test is that it is possible to make a product based on diethylhexylcarbonate that has almost the same qualities as the product based on cyclopentasiloxane.

The diethylhexyl carbonate has so far not been used in products sold in Scandinavia. The price of the alternative is approximately 35 - 40 DKK/kg while cyclopentasiloxane is more expensive, approximately 55 - 65 DKK/kg. The use of the diethylhexyl carbonate will not result in changes in the production equipment, but will of course involve new packaging due to new declarations of the product.

5.1.6 Hydrogenated polydecen

Hydrogenated polydecen is an alternative to different basis mineral oil or paraffin oils. If a product contains both paraffin oils and cyclomethicone, hydrogenated polydecen can, however, usually substitute both substances, as hydrogenated polydecen can give some of the soft feeling on the skin and can easily be absorbed in the skin without greasing. Hydrogenated polydecen will therefore to some extent match the properties of cyclomethicone. It can, however, not give the extra soft feeling that the siloxanes can add to a cosmetic leave-on product.

The product has been sold in Denmark for the last two years and can be found in several products in Denmark. The price of hydrogenated polydecen cannot be compared to cyclomethicone due to fact that it is not a direct alternative to cyclomethicone.

5.1.7 Summary and general experience

The investigation of alternatives to siloxanes in cosmetic products has shown that some alternatives have been developed and are used in Denmark, but the alternatives can at present typically not substitute the properties of siloxanes 100 %. The producers of cosmetic products must therefore often dispense with some of the properties of the siloxanes. Cyclomethicone and dimethicone in emulsions and creams are especially difficult to substitute, as the alternatives typically do not have a foam-reducing effect in the products. One alternative used in a cream has, however, been tested to have the same qualities as a cream with cyclopentasiloxane.

The suppliers of alternatives are experiencing great interest in alternatives to siloxanes, partly because of the environmental and health aspects, partly due to the options for evading different patents.

Many international producers use the Internet to advertise for hair and skin care products that are "silicone-free", but it seems that this is so far not a competition parameter for Danish producers.

Most of the alternatives are competitive with the siloxanes as regards price, however for some of the alternatives the price is twice the price of the siloxanes. A few of the alternatives are more expensive than the siloxanes. It is the general opinion that the use of alternatives to siloxanes does not cause changes in the production equipment, and the costs of substitution will therefore primarily be the extra costs for buying an alternative substance. Costs of new packaging are not regarded to be significant, as the substitution in most cases can be implemented when it suits into the production. As earlier mentioned the Danish industrial organization for cosmetics and toiletries, SPT, assesses the consumption of cyclomethicone used in Danish production to be approximately 5-6 tonnes per year. If the price of the most expensive alternative is used to predict an estimate of the costs of substitution of this amount of cyclomethicone, the price of the substitution will be approximately 200,000-300,000 DKK for the 5-6 tonnes. The 5-6 tonnes are however only a small part of the total consumption of siloxanes with cosmetics in Denmark (approximately 240 tons/year), as cyclomethicone is only one out of several siloxanes, and most cosmetic products are imported and not produced in Denmark.

5.2 Alternatives to siloxanes in cleaning agents and polishes

The siloxanes used in cleaning agents, waxes and polishes are in general not the same as the siloxanes used in cosmetics, although some of the wanted properties are the same, for example shine, spreadability and antifoaming. The identified alternatives are therefore also quite different from the alternatives developed for cosmetic products.

As for alternatives to siloxanes in cosmetic products it is the general opinion in the cleaning agent trade that silicones have some special properties that cannot easily be found in alternatives. These properties are especially as solvent, emulsifier and anti-soiling agent. Especially the use of the siloxane as defoaming agent is in many products difficult to substitute.

Siloxanes are used for polish, primarily because they give extremely high shine and strong adherence to the materials, especially glass, metal and plastic.

The siloxane content in cleaning agents is for most products less than 1% of the product which is further diluted in use. For polish products the siloxane content can be up to 5%, perhaps 10 % in some products.

The use of siloxanes and alternatives to siloxanes in cleaning agents and polishes has been investigated through contact with manufacturers and suppliers. The 6 main suppliers of siloxanes and chemicals to the cleaning agent trade and 10 of the Danish main manufacturers of cleaning agents and polishes have been contacted. It has however been difficult to identify alternatives to siloxanes, because substitution of siloxanes has not had special focus in the cleaning agent trade. Some alternatives have been used for several years, but have not been developed in the aim of substituting siloxanes, and it is a question to what extent they actually have similar properties.

Substances that are insoluble in water and with long carbon chains are in general suitable as alternatives to siloxanes in cleaning and maintenance agents. The longer carbon chains the substance have the more effective defoaming effect is obtained.

It is the general impression that there are fewer different types of alternatives to silicones in cleaning and maintenance products than in cosmetic products. If a search is made on the Internet for 'silicone-free' antifoaming agents, wax or polishes several products can be found, indicating that the use of alternatives is quite widespread. The reason for using the 'silicone-free' products is, however, most often technical.

The alternatives have been developed both due to the general interest in environment-friendly products in the trade for cleaning and maintenance agents, but also because the use of siloxanes can be problematic in some products. Silicones are for example often avoided in car waxes and other polish products for cars, because the use of silicones is disadvantageous if the car should later be re-painted.

Table 5.2 shows the types of alternatives to siloxanes in cleaning and maintenance agents identified through contact to Danish suppliers and manufacturers.

Table 5.2 Identified alternatives to siloxanes from Danish producers and suppliers

5.2.1 Mineral oils (tensides)

Many of the suppliers and manufacturers of maintenance products point at nonionic mineral oils or tensides as the main alternative to polydimethylsiloxanes in antifoaming agents. The mineral oils can be used in both polish products and antifoaming agents. Odourless kerosene is mentioned as a possible alternative to antifoaming.

The mineral oils typically do not have all the properties of polydimethylsiloxan. It can especially be difficult to obtain the same smooth surface for polishes. As antifoaming agents, the mineral oils are not always suitable for cleaning agents used in cold water, for example in floor cleaning machines.

The price level of the mineral oils is approximately the same as that of siloxanes, and in some cases they are cheaper, but as the siloxanes or alternatives only constitute few per cent of the product or even less than one per cent, the costs for using an alternative instead of a siloxane is regarded to be minimal.

5.2.2 Paraffin oils and vegetable oils

Paraffin oils and vegetable oils may like mineral oils be used as alternatives to polydimethylsiloxanes. Paraffin oils and vegetable oils are not very frequently used as alternatives to siloxanes in cleaning agents and polish products, but these types of oils can be used, as they have the defoaming properties.

The price of the paraffin oils and vegetable oil is in general lower than that of siloxanes.

5.2.3 Lipophilic tensides

Lipophilic tensides can be used as alternative to aminofunctional polydimethylsiloxanes used in polishes. The attractive shine and easy-cleaning surface that is obtained by using siloxanes can however not always be obtained to the same degree by using lipophilic tensides instead of siloxanes.

5.2.4 Block polymers

Block polymers consisting of polyethylenglycol and polypropylenglycol are a very applicable alternative to siloxanes in cleaning agents and polish products. The block polymer can be supplied with an extra alkyl chain by which the substance gets a lower surface tension that makes it possible to use the block polymer as antifoaming agent.

Block polymers are some of the most used alternatives to siloxanes in cleaning and maintenance agents, but are still less widespread used than the siloxanes. Block polymers are in general more expensive than the siloxanes that can be used in this type of products.

5.2.5 Summary

It has been difficult to identify alternatives to siloxanes, because substitution of siloxanes has not had particular focus in the cleaning agent trade. Some alternatives have been used for several years, but have not been developed in the aim of substituting siloxanes, and it is a question to what extent they actually have similar properties. Siloxanes are mainly used as antifoaming agent and to provide shine and spreadability to polishes. The antifoaming properties can be provided by a number of alternatives at approximately the same price as the siloxanes, but often the properties of the alternatives cannot fully match the properties of the siloxanes.

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Version 1.0 September 2005, © Danish Environmental Protection Agency