**1. Introduction**

It has been found, that N-alkyl-(C8 to C18) pyrrolidones are highly efficient, strong solvating performance plasticizers which decrease gelling temperatures substantially (Bonnet & Kaytan, 2008). They facilitate fast gelling, produce flexibility at extremely low temperatures. Higher alkyl pyrrolidones also exhibit very low volatility. After these excellent properties were proven by industrial trials in several different applications such as flooring, gloves, window sealing and wires, they were introduced to the market as Flexidone plasticizers.

Solubility temperatures of the N-alkyl-pyrrolidones (DIN 53408) are between 52ºC (N-octylpyrrolidone) and 80ºC (N-octadecyl-pyrrolidone). Accordingly, the gelling temperatures are substantially lower than with the standard plasticizers.

Plasticizing efficiency of the different Flexidone Types were tested through comparative determination of Shore A values. It could be shown that Flexidones are about 30-50% more efficient than the standard plasticizer DINP (diisononyl phthalate).

Cold Flexibility with the Flexidones was checked by the Folding test DIN EN 495-5.

Further trials in filled systems showed that Flexidones are highly compatible with e.g. calcium carbonate and allow very high filler loads with outstanding mechanical properties. Manufacturing tests with a highly filled system using an extruder resulted in increased output while significantly reducing plasticizer levels and processing temperatures.

In the broader effort to offer to the flexible-PVC industry cost-effective plasticizer systems with desired process- and end product properties, tests were performed on blends with various low cost secondary plasticisers. In these experiments, all Flexidone types have worked as performance boosters and compatibilizers.

Exemplarily the results of blends with certain fatty acid esters and chlorinated types will be presented. As a function of the ratio of mixture indentation hardness, tensile properties and gelling properties (plastisol) have been evaluated.

Compared to common systems, these new Flexidone mixtures surpass the performance characteristics and are superior to most of the phthalate and phthalate free systems. All of

Flexidone™ – A New Class of Innovative PVC Plasticizers 3

Chemically binding a exible non-polar alkyl chain with a compact hydrophilic head makes the alkyl pyrrolidones soluble in both polar and non-polar solvents. Even though the alkyl chain length can be adjusted to lie between C4 and C30 it has been found that chain lengths between C8 and C18 are particularly suitable for use as plasticizers. Due to their excellent dissolving power and good compatibility with PVC both gelling temperature (very low solubility temperatures – see Fig. 2) and gelling time (see gelling curves Fig. 9 and 14) can be substantially reduced. At the same time this leads to highly flexible PVC formulations that

A measure of the effectiveness of a plasticizer is its solubility temperature. This is the temperature at which a plasticizer completely dissolves a given PVC. Typical solubility temperatures lie between 87°C for butyl benzyl phthalate and 151°C for DINCH, with diisononyl phthalate at 129°C. Figure 2 shows the solubility temperatures for alkyl pyrrolidones with various alkyl chain lengths. It can be seen that the solubility temperature can be adjusted by chain length to lie between 52 and 80°C and is thus signicantly lower

> 6 8 10 12 14 16 18 20 **Alkyl chain length**

Fig. 2. The dependence of solubility temperature of various alkyl pyrrolidones on alkyl

This also reduces the time taken to produce a dry blend in a high speed cooler mixer without the need for external heating. Depending on the formulation mixing times can be reduced down to 20 % in comparison to phthalate plasticizer formulations. In addition,

N O


R

do not lose their exibility even at extremely low temperatures.

N O

R

than the solubility temperatures of conventional plasticizers.

Fig. 1. Electron delocalization in pyrrolidones.

**2.2 More cost effective dry blending** 

chain length in accordance with DIN 53 408.

**Temperature**

 **ºC**

the products are now industrially produced REACH-compliant types that are globally available in appropriate volumes.
