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Identification and assessment of alternatives to selected phthalates

3 Identified alternatives to DEHP, DBP and BBP

• 3.1 Functional mode of external plasticisers
• 3.2 Introduction to plasticiser substance families
• 3.3 Alternative plasticisers and polymers used in toys and childcare articles
  • 3.3.1 Toys and childcare articles on the Danish Market
  • 3.3.2 Toys and childcare articles on the Dutch market
  • 3.3.3 Toy s and childcare products on the market in Germany, Austria and Switzerland
• 3.4 Alternatives recommended by plasticiser producers
  • 3.4.1 Phthalate alternatives
  • 3.4.2 Non-phthalate alternatives
• 3.5 Alternative plasticisers applied with processing adjustments
• 3.6 Alternatives plasticisers selected for further assessment
• 3.7 Alternative flexible polymers
  • 3.7.1 Alternative materials suggested for further assessment

Information on alternatives to DEHP, DBP and BBP, actually applied today, has been collected from the following data sources:

• Danish manufacturers and importers of toys and childcare articles;
  
  
• Surveys of plasticisers in marketed toys and childcare articles;
  
  
• Direct contact to major suppliers of plasticisers.

These data sources have been supplemented with information from the literature and manufacturers' web sites.

The first section gives a general introduction to the way plasticisers work and to the different available plasticiser substance families, followed by a description of information collected directly from the above mentioned data sources.

3.1 Functional mode of external plasticisers

To get an impression of the many possibilities for plasticising polymers, we give an introduction to the basic functions of plasticisers, the variability in these functions, and which properties govern the functions. The description is used as basis for the later discussion of the technical feasibility of replacing phthalate plasticisers with alternatives.

We describe here the basics of external plasticisation of PVC, the major use of plasticisers. The word "external" denotes plasticisers that are not bound chemically in the polymer matrix, and can therefore migrate out of the polymer at certain conditions. Polymers can also be plasticised "internally" by incorporation of functional groups into the polymer itself, which imparts flexibility. Phthalates are external plasticisers, as are their direct substitutes, and external plasticisation is described in this section.

PVC consists of long chains of the basic vinyl building block. The polymer is bound together in three dimensions by two overall types of forces. In some points the polymer is crystallised into a fixed geometric pattern with strong chemical bonds. In the rest of the polymer matrix, the polymer chains are somewhat more randomly organised and bound together by weaker forces based on attraction between polar parts of the polymer chain with different polarity. The ideal plasticiser works in these less strictly organised parts of the polymer.

In the hard polymer, the chains are packed closely together, also in the randomly organised parts, and the weak attraction forces bind the polymer together to a rigid structure with no flexibility. The (external) plasticiser has solvent capabilities and penetrates the less strongly bound parts of the polymer in the so-called swelling, where plasticiser and polymer resin is mixed. In the polymer, the plasticiser acts as a kind of sophisticated lubricant, as it creates distance between the freely organised polymer chain parts, and shields the attraction forces between polar parts of the chain, and thereby weakens the attraction between the chain parts. This allows for more free movement amongst the weakly bound chain parts, which means that the material becomes flexible.

The properties of the plasticiser have immense influence of how well it plasticises the polymer, and on the performance characteristics of the plasticised material. It is however important to understand that the plasticiser (with a few exceptions) does not form specific chemical bonds with the polymer, and there is therefore in principle a flexibility in which type and configuration of plasticisers that actually can be used to obtain the desired plasticising performance characteristics.

External plasticisers may be separated from the PVC matrix due to extraction by solvents, oils, water, surface rubbing, volatility, migration into adjacent media, or degradation mechanisms.

Structure of some plasticiser families
As mentioned, many families of plasticisers are available. Most of them have however certain chemical functionalities in common with the phthalates family. This can be seen in Figure 3.1, which shows representatives of some different plasticiser families. They are typically branched, quite "voluminous" molecules, with many oxygen bonds (= carbonyl groups). Many have benzyl rings or the hydrogenated counterpart, cyclohexane.

Even so, many similar plasticisers have distinctly different impacts on health and environment, and are therefore relevant alternatives to phthalates. This is probably primarily due to the fact that many types of interactions with biological systems are substance specific, and even shape-specific (structurally specific), meaning that substances with identical chemical composition may work differently, if just a part of the molecule has shifted position from one place to another.

Figure 3.1 Structural diagrams of different plasticiser (Source: www.chemblink.com)

Phthalate (DEHP, DOP; di 2-ethylhexylphthalat)
Terephthalate, (DEHT, DOT DOTP; di 2-ethylhexyl terephthalate)
Trimellitates (TOTM; tri (2-ethylhexyl) trimellitate)
Aliphatic dibasic esters, adipates (DEHA, DOA = di (2-ethylhexyl) adipate )
(DBS = Dibutyl sebacate)
Benzoates (DGD; dipropylene glycol dibenzoate)
Citrates (ATBC; acetyl tributyl citrate)
Phosphates (tri(2-ethylhexyl) phosphate)
Glyceryl triacetate (GTA, Triacetin)

The substance family of the plasticiser influences its performance significantly, but some functional groups in the molecules also influence the performance across families, and plasticisers can thus to a certain extend be tailor-made to suit different performance needs. In addition, plasticisers can be mixed to achieve desired properties. Some of the important performance parameters of plasticisers are shown in Table 3.1 with some general chemical features influencing a plasticiser's performance for each parameter. All these parameters influence the performance of a plasticiser, and they are not independent, because one change in the plasticiser molecule may affect most or all of the parameters. Finding the good plasticiser is therefore not a distinct theoretical science, but rather an empiric process supported by a large number of measuring methods designed for this purpose.

Another important factor for plasticiser selection is the ease of processing of the resin-plasticiser system in the various steps involved in flexible polymer manufacture. Both the polymer and the plasticiser characteristics influence the processability. For a given polymer resin, the choice of plasticiser influences the temperatures needed for gelling (absorption of the plasticiser in the resin) and fusing (settling of the mixture in its final state), and the viscosity of the hot PVC melt or the plastisol blend, etc. Solvency for the PVC resin plays a role, and strong solvating plasticisers may be mixed into the general plasticiser to enhance processability. The volatility of the plasticiser, on the other hand, is typically the limiting factor on levels of strong solvating plasticisers used. Higher molecular weight plasticisers typically decrease volatility, but also viscosity, etc., with resulting constraints in processability (Krauskopf and Godwin, 2005). BBP is an example of a plasticiser which can reduce the operating temperatures in PVC processing.

3.2 Introduction to plasticiser substance families

This section focuses on the alternative plasticisers. The phthalates are described in more detail in Chapter 2.

Hundreds of substances have plasticising properties in PVC and other polymers. According to Krauskopf and Goodwin (2005), about 70 different plasticisers are available today, even though the consumption has so far been dominated by phthalates. DEHP, DINP and DIDP together comprise around 80% of global plasticiser consumption.

The main families of available plasticisers are shown in a generalised overview in Table 3.2 along with an indication of their performance characteristics. It shall be noted, however, that a number of plasticisers on the market are not member of any of the listed substance families. Each substance family has many members with different performance characteristics, and the table may not include all performance options for all families. The table also shows a traditional grouping of plasticisers in "general purpose" plasticisers with a vide application field and currently low prices (such as DEHP), "performance plasticisers" which provide special performance possibilities and are currently more expensive (such as DBP and BBP), and last "speciality plasticisers" which also provide other functionalities than flexibility and have generally currently even higher prices (Krauskopf and Goodwin, 2005).

A general description of the plasticiser substance families is given in Annex 2. Technical aspects for selected plasticisers are described in more detail in Chapter 6.

X denotes primary performance function; x denotes other performance functions (as used in Krauskopf and Goodwin, 2005).

*1: In Krauskopf and Goodwin (2005) these plasticisers were pooled in one group in a similar table, and primary/secondary function distinction may be imprecise here.

*2: Designated as "phthalate-like esters" in Krauskopf and Goodwin (2005). Include substances such as DEHT (terephthalate), DEHIP (metaphthalate) and DINCH (cyclohexane counterpart to DINP).

*3: Extenders are low price oils which are used to extend the effect of other plasticisers, but cannot work as plasticisers alone; e.g. chlorinated paraffins.

*4: Includes adipates.

*1: phr = parts per hard resin, meaning parts per weight of hard PVC.

*2: A measure for the plasticiser's efficiency in making PVC flexible; the lower the number, the softer the PVC and the more efficient plasticiser.

*3 Measured performance in another PVC resin (the same for DEHP and EHT).

*4 Data from Danisco; at concentration 40 phr; PVC resin type not specified.

3.3 Alternative plasticisers and polymers used in toys and childcare articles

3.3.1 Toys and childcare articles on the Danish Market

Data on alternative plasticisers and polymers have been obtained by direct contact to Danish manufacturers and larger suppliers of toys and childcare articles. A list of contacted companies can be found in Annex 1. Five out of eleven contacted manufacturers/suppliers have responded with information on alternative plasticisers, whereas four report that they do not have any experience with PVC, DEHP, DBP, BBP or alternatives. All manufacturers have been asked to provide examples of own polymer products containing plasticisers and to specify the applied polymers and plasticisers. Furthermore they were requested information on the technical and economical applicability of the alternative plasticisers.

The results are based on statements by three large companies on the Danish marked for toys and childcare articles. Table 3.4 shows the plasticisers used in PVC products by these three companies.

Chemical name of plasticiser:
DINA: diisononyl adipate,
TMP (trimethylolpropane): 2,2-dihydroxymethybutanol, 2-ethyl-2-hydroxyl-1,3-propanediol,
ATBC: acetyl tributyl citrate,
DEHT: 1,4-benzenedicarboxylic acid, di(2-ethylhexyl) ester,
DINCH: di(isononyl) cyclohexane-1,2-dicarboxylate,
LG-Flex BET: trimethylolpropane, mixed triesters and diesters with benzoic acid and 2-ethylhexanoic acid,
Mesamoll: alkyl sulfonic acid ester of phenol (ASE).

Table 3.5 shows examples of product types and currently applied plasticisers from one of the large toy companies on the Danish marked.

Chemical name and CAS No: DINA: diisononyl adipate, CAS No 33703-08-1, ATBC: acetyl tributyl citrate, CAS No 77-90-7, DEHT: 1,4-benzenedicarboxylic acid, di(2-ethylhexyl) ester CAS No 6422-86-2, TMP: 2,2-dihydroxymethybutanol, CAS No 77-99-6, DINCH: di(isononyl) cyclohexane-1,2-dicarboxylate, CAS No 166412-78-8.

Experiences with alternative plasticisers
The restriction of the use of DEHP, DBP, BBP, DINP, DIDP and DnOP in toys and childcare articles has challenged the companies on the Danish marked on toys and childcare articles to find alternative solutions for product manufacturing. The companies contacted in this study have various experiences with substitution and some of these are described in the following.

In 2005, a company switched to the alternative ATBC (Citroflex A-4) for all toys for children under 3 years and those of any age which are designed to go to the mouth. This particular plasticiser had been given a favourable opinion by the CSTEE for use in toys. However it suffered from a variety of technical drawbacks when compared with DINP. For instance ATBC would not take decoration and it had high migration into adjacent materials leading to swelling and splitting. There was consequently a need for changes of tools and it had a relatively high cost. The work on alternatives to ATBC suffered technical set backs as the company discovered that alternatives could give rise to mal-odours and poor colour matching in the final PVC. Three potential replacements for DINP were identified: ATBC, DINCH and DEHT. These could be blended in a variety of combinations to achieve softened PVC that performed to the required standards of safety and reliability. These blends could be used in many cases as one-to-one replacements for DINP so major changes to designs and tooling were not necessary.

According to a Danish manufacturer, when the Danish ban came into force, the price of products for the company raised by approximately 50% because the international manufacturers had to produce special deliverances to the Danish marked without phthalates. After the restrictions comprised the entire EU, the prices dropped again. The company estimates that the ban has resulted in a remaining increase in prises of approximately 10-20% because the alternative substances generally are more expensive even after the preliminarily reduced costs related to changing the production.

3.3.2 Toys and childcare articles on the Dutch market

In addition to the information obtained from manufacturers and suppliers of toys and childcare articles in Denmark, data on plasticisers and polymers in toys have been provided by the Dutch Food and Consumer Product Safety Authority, under the Dutch Ministry of Agriculture. The Dutch Food and Consumer Product Safety Authority has investigated plastic softeners in toys and childcare articles for several years.

During May 2007 in total 200 samples of soft plastic toys and 12 samples of soft childcare articles were acquired by The Dutch Food and Consumer Product Safety Authority from the local retail market. These included bath toys, bouncy balls and inflatable aquatic toys as well as bibs, changing table pillows and seats of high chairs. At least 96 brands were represented. Regulated phthalates were analysed quantitatively, whereas other plasticisers, phthalates as well as alternatives, were analysed qualitatively only. The surveys conducted the other years included analyses on regulated phthalates only.

Most examined samples (67%) were made of PVC. Of the examined samples, toys as well as childcare articles, 41% exceeded the legislative limit for DEHP, DBP, BBP, DINP, DIDP and DnOP.

Statistics of the occurrence of non-phthalate plasticisers ranked the alternatives according to the number of products in which they were used as follows (clearly identified substances): DINCH, nonylphenol, TXIB, TBAC, ATBC, DEHTP, DINA, DEHA (see Table 3.6). It is not clear whether the nonylphenol serves as a plasticiser in the plastics. In the literature other applications of nonylphenol in plastics are described, e.g. as an antioxidant.

The plasticisers and polymers by product type are shown in Table 3.7. The table includes only the product types for which both phthalate plasticisers and alternatives were found.

Compared to similar surveys in 2001, 2004 and 2005 there seems to be only a slight reduction in the use of the six phthalates during the period as shown in Figure 3.2. Notably DBP were found in 30% of the samples in 2004. The percentage had decreased to about 10% in 2007 and further to 1% in 2008 (FCPSA 2008b). BBP is found in only a few percentages of the samples all the year.

Figure 3.2 Percentage of samples of toys and childcare products from the Dutch retail market that contain 6 specified phthalates (n = number of samples) (FCPSA, 2008a)

3.3.3 Toy s and childcare products on the market in Germany, Austria and Switzerland

A joint study performed in Germany, Austria and Switzerland screened and analysed for all possible plasticisers in 252 samples from 172 toy and childcare products collected in these countries in 2007 (Biedermann-Brem et al., 2008). The study identified the substances shown in Table 3.8 and made detailed statistics of the occurrence, concentrations and mixtures of the identified plasticisers across product groups enabling a ranking of the phthalates as well as the alternatives.

* Abbreviation used in this study in brackets.

The results for each products group involved are shown in Table 3.9, for all plasticiser with occurrence above 4% (main plasticisers in each product). Across all product categories examined, the most important non-phthalate plasticisers used in these products were DINCH, ATBC, DEHT, TXIB and NPG-EHA-BA; see chemicals names in Table 3.8.

Phthalates were detected in 27% of the samples. The phthalates DEHP, DINP, DBP, DIBP, DIDP and DnOP were found. In most cases, the PVC products contained more than one plasticiser; the number of plasticisers in the same product varied between 1 and 5.

Click here to see: Table 3.9 Main plasticisers (>4% conc.), their occurrence and concentrations in 5 products groups (table reproduced from Biedermann-Brem et al., 2008)

3.4 Alternatives recommended by plasticiser producers

In view of the wide spectre of alternative plasticisers available, and in order to get more detailed information on the experience gained on the market with alternatives plasticisers, a number of plasticiser producers were contacted directly with detailed questions on the following issues:

• Proposals for alternative plasticisers for specified traditional DEHP, DBP and BBP applications;
• Level of experience gained on the market with proposed alternatives, according to the manufacturers’ own judgement (4 simplified categories);
• Important processing adjustments, if any, compared to DEHP, DBP and BBP, respectively;
• Limitations in use of alternatives for specified applications;
• Prices of alternatives.

The following plasticiser producers have been contacted based on an initial literature and Internet identification, and asked for this detailed information on their alternatives with focus on non-phthalate alternatives:

• BASF
• Lanxess (formerly Bayer)
• Genovique
• Vertellus (formerly Morflex)
• Eastman Chemicals
• Danisco
• Indo-Nippon Chemicals
• Exxon Mobil

The responses provide an improved indication of, which alternatives are important on the market, and which are emerging or more peripheral. Some producers have not adhered strictly to the market categorisation texts suggested, and here an interpretation was needed to allow for a uniform presentation. Some of the responding companies have not mentioned all their products that otherwise appear to be relevant alternatives to the phthalates judging from their websites. The reasons for this are unknown.

3.4.1 Phthalate alternatives

A number of phthalates are marketed as alternatives to the regulated phthalates and as mentioned above several of the alternatives have a significant market share.

It is highly dependent on the specific application which phthalates are recommended as alternatives. Table 3.10 lists the alternatives recommended by one major manufacturer for five different layers in flooring applications; the main application area for DEHP and BBP.

*1 Diisoheptyl phthalate (DIHP). CAS No. 71888-89-6
*2 DEHP is designated DOP at the webpage.

According to ECPI (2009) 21 different phthalates are in common use. It has been beyond the limits of this study to make a comprehensive assessment of all phthalates that may be used as alternatives to the classified substances. Selected alternatives marketed as alternatives for major applications of the three classified substances are shown in Table 3.11.

3.4.2 Non-phthalate alternatives

The received responses as regards identification of non-phthalate alternatives to DEHP, DBP and BBP, their application, as well as the level of market experience are presented in Table 3.12, Table 3.13 and Table 3.14 below as recommended by contacted manufacturers.

Besides the results presented in the tables, BASF has reported, that it is their understanding of their customers' experiences that in most, if not all, PVC polymer applications the DEHP functionality may be substituted by applying other plasticisers such as DINP, DPHP (Di- (2-propyl heptyl)phthalate), Hexamoll DINCH or others.

Danisco has further reported that Soft-n-safe (consisting of two substances here designated as COMGHA 1 and COMGHA 2) can be used as alternative to DEHP for various applications.

Click here to see: Table 3.12 Alternatives to DEHP proposed by contacted producers, by application and with indication of market experience

Click here to see: Table 3.13 Alternatives to DBP proposed by contacted producers, by application and with indication of market experience

Click here to see: Table 3.14 Alternatives to BBP proposed by contacted producers, by application and with indication of market experience

3.5 Alternative plasticisers applied with processing adjustments

As indicated in the sections above, a large spectre of plasticisers are available, which can influence the final product quality in a number of ways, and additional variety can be obtained by mixing different plasticisers. Besides this, the possibility exists, of accepting that the production conditions or the specifications of the final product are slightly altered, as compared to the present situation. For some products, this may not be critical, whereas for applications requiring specific technical functionalities, such as low temperature flexibility, specific migration thresholds, etc. such deviations may be critical. A closer evaluation of possibilities for substitution of plasticisers with resulting altered performance must be taken in each case.

3.6 Alternatives plasticisers selected for further assessment

Table 3.15 below lists the identified plasticisers and indicates the plasticisers selected for further evaluation in this study (marked in gray).

The selection was based on the following factors:

• Experience with the substances on the marked, based on data collected from suppliers of alternative plasticisers.
  
  
• Occurrence as plasticisers in toys and child care articles, based on the studies of plasticisers in these products described above.
  
  
• The list should cover the main alternatives for each of the three phthalates DEHP, DBP, and BBP.
  
  
• Representation of major substance groups used as plasticisers based on description above.
  
  
• Substances with identified significant environment and health effects (CMR or PBT, based on reviews in COWI, 2009 a) were not suggested for further assessment.

Click here to see: Table 3.15 Identified plasticisers and reason for selection for environmental and health assessment

3.7 Alternative flexible polymers

Besides the direct alternatives to DEHP, DBP and BBP used as chemicals in various applications, a large number of materials can substitute for flexible PVC in the production of the products.

These alternative materials include, among others, such diverse examples as linoleum and wood for flooring, woven glass fibre and paper for wall coverings, and glass for medical appliances.

The ECHA study on DEHP (COWI, 2009a) concludes that available studies demonstrate that for many applications of DEHP/PVC, alternative materials exist at similar price. Many of the materials seem to have equal or better environment, safety and health performance and cost profiles, but clear conclusions are complicated by the fact that not all aspects of the materials' lifecycles have been included in the assessments.

Due to the wide spectre of products and applications covered, it was decided in this study to limit the considerations for assessment of alternative materials to alternative flexible polymers with characteristics similar to the characteristics of flexible PVC. Based on the information in previous studies, the following flexible polymers are among the principal alternatives to flexible PVC:

• Ethylene vinyl acetate, EVA;
• Low density polyethylene, LDPE;
• Polyolefin elastomers (polyethylene and polypropylene elastomers);
• Several types of polyurethanes (may in some cases be plasticised with phthalates);
• Isobutyl rubber;
• EPDM rubber (may in some cases be plasticised with phthalates);
• Silicone rubber.

3.7.1 Alternative materials suggested for further assessment

A number of studies have been undertaken on replacing PVC with other materials for different applications. For example, an environmental and health assessment of two alternative materials has been conducted by Stuer Lauridsen et al.(2001): PU (polyurethane) and LDPE (low density polyethylene). On the basis of the available data it was not possible to make a full assessment of the materials. This has been the case for several other studies on the subject.

To focus the efforts in this study, it was decided to include an assessment of polyolefin (polyethylene/polypropylene) elastomers as alternatives to flexible PVC - on an overall screening level - of its lifecycle impacts, supplemented by brief description of other flexible polymers mentioned above based on available aggregated reviews.

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Version 1.0 November 2010, © Danish Environmental Protection Agency