STABILISERS

Stabilisers are added to PVC to allow its processing and to improve its resistance especially in outdoor applications, weathering and heat ageing and have an important influence on the physical properties of PVC finished articles. Factors such as process technology involved, technical requirements of PVC end product, regulatory requirements and cost, influence the choice of the stabiliser used.

Stabilisers are categorized as follows :

CALCIUM-BASED STABILISERSLIQUID STABILISERSTIN STABILISERSLEAD STABILISERSCADMIUM STABILISERS

Calcium-based stabilisers (including Ca-Zn ones) are now largely used in wires and cables, in window and technical profiles (also foamed ones), and in any type of pipes (such as soil and sewer pipes, foam core pipes, pressure pipes, corrugated pipes, land drainage pipes and cable ducting) as well as the corresponding fittings.

Calcium-based stabilisers have also been introduced in PVC rigid calendering film production when improved organoleptics characteristics are required, for instance as alternative to tin mercaptides in transparent food packaging application or as alternative to tin carboxylates in PVC blown films shrinkable and for candy wrap. Similarly, calcium-based stabilisers are now an alternative to Liquid Mixed Metals (LMM) for several flexible applications, especially for the indoor ones, when stringent air quality requirements are in place (see “VOC improvement” under the liquid stabilisers).

ESPA members have committed to proactively use in their systems only molecules which, at the current knowledge, don’t incur into future restrictions.

The liquid mixed metal stabilisers are used in several PVC flexible applications like: calendered films; extruded profiles; injection moulded, soles, footwear; extruded hoses and plastisols (flooring, wall covering, artificial leather, coated fabrics, toys).

Liquid mixed metal stabiliser systems are based on Ba, Zn, Ca, Mg or K carboxylates. In general liquid mixed metals like Ba-Zn, Ca-Zn and Mg-Zn require the addition of co-stabilisers, antioxidants and organo-phosphites to provide optimum performance. The costabilisers are usually imparted to the liquid mixed metal stabiliser system. To adjust the viscosity different solvents are used including hydrocarbon solvents and plasticisers.

Liquid Ba-Zn stabilisers and liquid Ca-Zn stabilisers have successfully replaced cadmium-based stabilisers in any PVC semi-rigid and flexible applications.

The stabilisers are formulated to meet specific requirements such as good initial colour, long-term stability, good transparency, good printability, weatherability, ageing resistance, good compatibility with all types of PVC, with fillers, and pigments. A good stabiliser achieves the best possible compromise of all the necessary requirements, including cost.

VOC improvements

In recent years, different technologies have been introduced to the industry to improve VOC (volatile organic compounds) emissions in flexibles articles, particularly in relation to the building and construction industry. Low emission and low odour are the key characteristics required by the industry and reductions in VOCs can be achieved using Ca/Zn solids, phenol-free liquids and pastes. The available stabilisers are suitable for all kind of PVC applications: transparent, filled, pigmented, technical and food contact. In case of pastes, the liquid carried is generally ESBO or plasticisers.

 

News
17 December 2014

 

DOTE Classification and SVHC/Candidate List

 

DOTE Regulatory Update

 

By far the largest use for tin compounds is in the stabilisation of PVC. Contrary to North America, where tin systems are used for almost all-rigid PVC applications, the main usage in Europe is for rigid, transparent applications where rigorous processing conditions require an outstanding stabilisation.
In addition to maintaining high transparency, tin stabilisers also provide a very good early colour (no yellowing) and very good colour retention (delay of yellowing). Due to their fast and complete mechanism of stabilisation, tin stabilisers are also suitable for use in opaque applications and particularly where light colours are required, or when process requirements are demanding (thick plate extrusion, furniture films). Additionally, tin stabilisers provide a very good processability with high through put and no plate out.
Moreover tin stabilisers are approved for use in food contact applications, potable water applications and some tin stabilisers are approved for use in rigid medical applications.
Examples of applications where tin stabilisers are widely used are: calendered films for pharmaceutical or food packaging, foils such as credit cards, sheets and sidings, extruded pipes and profiles, extruded blown films, injection moulding fittings and other technical articles.
Tin stabilisers can be divided into two main groups, the first containing stabilisers with tin-oxygen bonds and the second stabilisers with tin-sulphur bonds.
The first group is Tin carboxylates, which provide an excellent light- and weathering stability to PVC products and find rising use particularly in outdoor applications. Some examples are transparent panels and translucent double-wall panels for greenhouses. Specific stabilisers within this group – Octyltinmaleates – are approved for food contact, for the production of PVC blown films, like candy wrapping.
The second group is often described as Tin mercaptides. These stabilisers are highly efficient and allow the production of rigid PVC articles even under high-demanding processing conditions (calendering, extrusion and injection moulding). Tin mercaptides have a typical characteristic strong odour, detectable during processing and in many cases on PVC finished articles. They show moderate light-stability. The most powerful compounds within the mercaptide class are the mercapto-acetate (thioglycolate) ester derivates and these are the most common tin compounds applied today. The Tin mercaptides are usually mixtures of di-alkyl –and mono-alkyl tin-compounds, of which the ratio can be varied to create suitable stabilisers with best performance, mainly dependent upon process technologies and PVC end-use application. The alkyl groups are Octyls, Methyls and Butyls.
Health and environmental concerns and restrictions on specific organotins used in anti-fouling paints (TBT) generated some questions about the future of organotin compounds. Risk assessments on various organotin compounds including stabilisers have been conducted between 2002 and 2007. The final decisions resulting from these risk assessments led to some restrictions on specific applications, and clarified that there is still a future for organotin stabilisers. Most organotin stabilisers have already been successfully REACH registered.

 

1 July 2013

 

ETINSA Position Paper on the EU public consultation about the opportunity of launching an initiative for responsible sourcing of minerals coming from conflict-affected areas

 

ETINSA Position Paper

Traditionally, lead-based compounds have been used in many parts of the world to stabilise rigid PVC for the construction industry use (e.g. pipes, fittings and profiles applications) and in flexible PVC, mainly for wires and cables.  The list of registered substances is available below.
Lead-based stabilisers’ cost/performance ratio and physical properties, in terms of excellent heat and light stability, good electrical resistance, excellent short and long-term mechanical properties and low water absorption, have made them the materials of choice for many long life applications.
Types of lead stabilisers are tetra-basic lead sulphate, tri-basic lead sulphate, di-basic lead phosphite, di-basic lead phthalate, di-basic lead stearate, neutral lead stearate.
Concerns have been expressed about possible adverse effects of lead on health and the environment. A full Risk Assessment on lead was conducted in 2004 and results were presented to the EU Authorities.
In the VinylPlus Voluntary Commitment, ESPA and EuPC (European Plastics Converters) committed to replacing lead-based stabilisers (see list below) completely by the end of 2015 on the EU-28, with interim targets of a 15% reduction by 2005 and a 50% reduction by 2010. The commitment of 100% phase-out by the end of 2015 was extended to the EU-27 in 2007 (EU-28 in 2014). The progressive substitution of lead-based stabilisers is ongoing and confirmed by the corresponding growth in calcium-based stabilisers, used as an alternative to lead-based stabilisers, more and more also outside Europe.
LiBRE (Lead in Blood REduction Programme)
An initiative from ELSA to foster good practices to promote blood-lead reduction
Risk Assessment on lead:conclusions
The Voluntary Risk Assessment on Lead was funded by the lead industry and managed by ILA Europe, the International Lead Association. ELSA (European Lead Stabilisers Association – a sub-group of ESPA) contributed for the stabilisers.

The studies indicated as early as 2005 that the DNEL (Derived No-Effect level) for blood lead was:

1) 40 µg Pb / dL blood for male worker

2) 30 µg Pb / dL blood for women of non-reproductive age

3) 10 µg Pb / dL blood for women of reproductive age to ensure protection of the unborn child

Those values were lower than most national limits in force at that time.
LIBRE : the response by the stabilisers manufacturers
ELSA aknowledged the DNEL derived from the Risk Assessment and the need to reduce exposure to lead. The association launched the LIBREprogramme in May 2005. ELSA involved the Downstream Users (DU) associations through the EuPC structure. Gradually the manufacturers and the downstream users of lead compounds managed to reduce the exposure in their plants below the DNEL.
REACH Registration and Exposure Scenario
The DNEL derived from the Voluntary Risk Assessment were used for the REACH registrations. As a consequence, they have to be observed by the Downstream Users (DU) through the Exposure Scenario. In addition the national limits remain applicable, eg. the lead-in-air limits.
Good practices suggestions in the lead industry
The lower the better: lead is under continuous regulatory pressure. Therefore ELSA wishes to share with all DU the set of Recommended Good Practices established by the lead industry.
List of registered substances :
EC No. CAS RN Substance Name Note and common name
215-290-6 1319-46-6 trilead bis(carbonate) dihydroxide Not relevant for stabilisers anymore!
235-067-7 12065-90-6 pentalead tetraoxide sulphate tetrabasic lead sulfate
235-252-2 12141-20-7 trilead dioxide phosphonate dibasic lead sulfate
235-380-9 12202-17-4 tetralead trioxide sulphate tribasic lead sulfate
235-702-8 12578-12-0 dioxobis(stearato)trilead dibasic lead stearate
263-467-1 62229-08-7 Sulfurous acid, lead salt, dibasic dibasic lead sulfite
273-688-5 69011-06-9 [phthalato(2-)]dioxotrilead dibasic lead phthalate
292-966-7 91031-62-8 Fatty acids, C16-18, lead salts neutral lead stearate

Cadmium based systems have been available for many years due to their excellent performance qualities. However, their use in the European Union was phased out on a voluntary basis as part of the industry’s Voluntary Commitment of 2000 (Vinyl 2010).
Cadmium was used in form of a stearate or laurate for stabilising PVC and was combined with barium ester or lead stabiliser. Cadmium stabilisers offered excellent heat stability and weatherability to PVC compounds. There were mainly used in semi-rigid and flexible foil for products such as roofing membranes and in rigid applications for outdoor use such as window profiles.
Since June 1991, the Council Directive 91/338/EEC (now Annex XVII (Restrictions) of REACH) limits the use of cadmium compounds in most applications. Except in a very few applications, placing on the market articles manufactured from plastic material coloured or stabilised with cadmium is prohibited if the content exceeds 0.01% by mass of the plastic material. With the implementation of the PVC industry’s Voluntary Commitment in 2000, the use of cadmium in all stabiliser systems placed on the European market has been phased out voluntarily by all ESPA members: the use of cadmium was voluntary stopped in EU-15 in 2001. The commitment was extended to the new EU countries in 2007 (EU-27).