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More environmentally friendly alternatives to PFOS-compounds and PFOA

Appendix F Identified alternatives

• PFBS - Perfluorobutanesulfonate
• C6-fluorinated compound
• Fluorotelomer-based products
• Fluorinated polyether
• Propylated aromatics
• Aliphatic alcohols
• Sulfosuccinate
  • Information from Münzing Chemie
  • Information from Cognis
  • Information from BASF
• Silicone polymers

Telomer-based products are in general alternatives to PFOS-related compounds. However, a search for other alternatives was carried out during the project. First of all, the Internet was used. Secondly, the producers of relevance were contacted by email in order to learn more about the alternatives (see a more detailed description in appendix B). Furthermore, a different approach was used within the paint and varnish area, as EnPro ApS (a laboratory within the area of paint, ink and varnish) participated in this project. A raw materials catalogue was used to identify possible producers of alternatives. An email was sent to the companies that produced products with the same function as the listed fluorosurfactants in the catalogue. Therefore, more alternatives are presented within this area.

The following compounds have been identified as alternatives to PFOS-related compounds during the project. No alternatives to PFOA have been identified. Several producers of PFOA were asked about alternative options to PFOA, and those who replied had no alternative options to PFOA. However, as described in the report, use of PFOA does not seem to be the biggest problem. This will be the production of telomer alcohols that in the environment can degrade to PFOA.

One company mentioned that their products (fluorinated) can be used as alternatives for telomer based products as well.

Table 0.1: Alternatives to PFOS-compounds

Each of the alternatives described above is presented more detailed in the following paragraphs.

PFBS – Perfluorobutanesulfonate

In June 2003, the 3M Company replaced the PFOS-compound in their Scotchgard products with PFBS (perfluorobutanesulfonate). 3M's Schotchgard products are cleaners and stain protectors for carpets, leather, furniture, automotives, hard surfaces and other apparels. After the phase-out of PFOS in the Scotchgard products, the 3M Company first presented an aerosol-can based on non-perfluoro chemistry. However, the product worked on water but not on grease. Therefore, 3M now uses the perfluoro-compound with a shorter chain length – C₄ instead of the former C₈ PFOS compound. (Flouride Action Network, 2004).

In the following table properties of PFBS are presented. The technical and environmental properties are found in different product information at 3M's website (www.3m.com).

Table 0.2: Properties of the alternative PFBS

C₆-fluorinated compound

According to 3M's website, a C₆-fluorinated compound is used in their Fire Protection Fluid. The compound is dodecafluoro-2-methylpentan-3-one (CF₃-CF₂-C(=O)-CF(CF₃)2). This compound is also a part of the Novec product series.

Table 0.3: Properties of the alternative C₆ – fluorinated compound

Fluorotelomer-based products

DuPont manufactures a range of fluorotelomers especially designed for fire-fighting foam formulations – DuPont FORAFAC®. These fluorotelomer products are predominantly based on C₆ molecules (more than 80%). According to DuPont, their FORAFAC® 1157 and 1183 products are based on more than 95% C₆ telomer, whereas FORAFAC® 1157N is based on more than 65% C₆ telomer. (Personal communication DuPont, 2004).

Table 0.4: Properties of DuPont's Forafac

Fluorinated polyether

One of the contacted companies in search for alternatives gave the following information about their alternative, which is a fluorinated polyether. This has specifically been used in about 40 floor polish products in the USA, Europe and Asia. According to OMNOVA the PolyFox product line is, besides an alternative to PFOS-based products, also an alternative to the long chained telomer based products (which have showed to have the potential to degrade to PFOA in the environment). (Personal communication OMNOVA, 2004).

OMNOVA Solutions Inc. manufactures a line of fluorosurfactants called PolyFox™. The entire PolyFox family of fluorosurfactants is polymers with a molecular weight greater than 1,000. The PolyFox polymers are based on ether links – both the polymer backbone linkages and the link between the backbone and the perfluoroalkyl pendant side chains. The PolyFox flurosurfactants are synthesized from perfluoroalkyl starting materials with a fully fluorinated carbon chain length of C₄ or less. The current first generation products are all made with C₂F₅ or CF₃ perfluoroalkyl side chain structures. (Personal communication OMNOVA, 2004).

The fluorinated polyethers are either hydroxy-terminated or acrylate-terminated according to the MSDS's found for PolyFox products.

The basic structure of some of the different PolyFox™ compounds is illustrated in the figures below. (Personal communication, PoraTek, 2004).

Figure 0.1: The basic structure of PolyFox 3320 compound (Personal communication, PoraTek, 2004). x+y equals about 20.

Figure 0.2: The basic structure of PolyFox 136 A with CF₃ as the basic perfluoralkyl group (Personal communication, PoraTek, 2004). x+y equals about 6.

Figure 0.3: The basic structure of PolyFox 156 A with C₂F₅ as the basic perfluoralkyl group (Personal communication, PoraTek, 2004). x+y equals about 6.

Figure 0.4: The basic structure of PolyFox 656 with C₂F₅ as the basic perfluoralkyl group. The technical properties of this compound are described in Table 0.5 (Personal communication, PoraTek, 2004). x+y equals about 6.

The technical properties listed in the table below are for PolyFox 656, which is shown in Figure 7.2 just above. However, all PolyFox compounds have similar technical properties.

Table 0.5: Properties of the alternative fluorinated polyether

Propylated aromatics

Rütgers Kureha Solvents produces different propylated aromatics (naphthalenes and biphenyls), which can be used as water repelling agents for different applications. For example rust protection systems, marine paints, resins, printing inks, coatings, electrical applications, electronically and mechanical applications. (Personal communication RKS, 2004). The different propylated aromatics are presented in table Table 0.6 below and some of the compounds are illustrated in the figures below.

Figure 0.5: The chemical structure of Ruetasolv DI (CAS-No. 38640-62-9) – to the left, and Ruetasolv TTPN (CAS-No. 35860-37-8) – to the right.

Figure 0.6: The chemical structure of Ruetasolv BP 4103 (CAS-No. 25640-78-2) – to the left, and Ruetasolv BP 4201 (CAS-No. 69009-90-1) to the left. Both products are mixtures of isomers.

Table 0.6: Properties of the alternative propylated aromatics

Aliphatic alcohols

BASF produces a large range of surfactants for different purposes. In coatings application fluorosurfactants are, according to BASF, mainly used for substrate wetting, levelling and reduction of surface tension (e.g. in spray applications). The key to the often-superior performance of the fluorosurfactants is the extremely low surface tension, which cannot be matched with other surfactants. However, due to high prices of the fluorosurfactants and due to environmental reasons, other surfactants can be used as alternatives if it is not a technical must to achieve such low surface tension levels.

Possible replacements to fluorosurfactants are silicone surfactants, which BASF does not produce, or surfactants based on aliphatic alcohols. BASF produces a range of aliphatic alcohols, both anionic and non-ionic surfactants. However, especially the effect of the non-ionic surfactants is mixed, because these products can also be used as defoamers or emulsifiers. So the non-ionic surfactants are difficult to use as replacements for fluorosurfactants. Therefore, only the anionic surfactants of BASF (Emulphor® FAS 30 and Lutensit® A-BO) are described in details. The Emulphor product from BASF is a fatty alcohol polyglycolether sulfate, whereas the Lutensit A-BO product is a sulfosuccinate. The Lutensit A-BO product is therefore described together with the other sulfosuccinate products. (Personal communication BASF, 2004).

Table 0.7: Properties of the alternative fatty alcohol ethoxylate

Sulfosuccinate

Information from Münzing Chemie

Münzing Chemie produces wetting agents for water-based applications, which are used to lower the surface tension of water to wet substrates or pigment surfaces. With some of their products they are able to replace fluorobased wetting agents, e.g. in wood primers. The best product for this kind of applications is their product EDAPLAN LA 451, which is based on a sulfosuccinate derivative in ethanol (19%) and water (12.5%). Sulfosuccinates are esters of succinic acid (HOOC-CH₂-CH₂-COOH) in reaction with hydrogen sulfite. The product EDAPLAN 451 contains a mixture of chemicals. (Personal communication with Münzing Chemie, 2004)

Table 0.8: Properties of the alternative Sulfosuccinate (by Münzing Chemie)

Information from Cognis

Cognis produces surfactants, wetting agents and dispersing agents for the paint and coating industry. The group of products technically competing with fluorosurfactants are sulfosuccinates. However, the sulfosuccinates do not reach such low surface tensions as it is possible with fluorinated surfactants, but nevertheless sulfosuccinates produced by Cognis are widely used in printing inks, where they also are approved for food contact. The best product for competing with fluorinated surfactants is their product Hydropalat® 875, which is based on the sodium salt of di(2-ethylhexyl) sulfosuccinate in ethanol (5%) and water (20%). (Personal communication with Cognis, 2004)

Table 0.9: Properties of the alternative Sulfosuccinate (by Cognis)

Information from BASF

As described in the previous section BASF also produces a sulfosuccinate products, which can be used as an alternative to fluorosurfactants within the coating industry.

The Lutensit® A-BO product of BASF contains a di-octyl-sulfosuccinate (di(2-ethylhexyl) sulfosuccinate), which has the following structure.

Table 0.10: Properties of the alternative sulfosuccinate

Silicone polymers

Worlée-Chemie produces silicon polymers, which in the paint and ink industry in several cases can be used as alternative wetting agents to fluorosurfactants. Two products are emphasized: WorléeAdd® 340 and WorléeAdd® 345. The first product is a non-ionic modified silicone polyether, where the latter is a mixture of a silicone polyether and a dioctylsulfosuccinate in ethanol and water. (Personal communication Worlée-Chemie, 2004).

Table 0.11: Properties of the alternative silicone polymers

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Version 1.0 June 2005, © Danish Environmental Protection Agency