The present invention relates to novel succinic acid ester mixtures and to the use thereof as plasticizers for plastic materials. The claimed mixtures are characterized by having good plasticizing effects with low dissolution temperatures.

177 g of succinic acid(cas:110-15-6) 268 g of 2-ethyl-1-hexanol, and 221 g of benzyl alcohol are used as initial charge in 175 ml of xylene in a nitrogen-gas-inertized 1 l multinecked round-bottomed flask with water separator and reflux condenser, internal thermometer, and stirrer. After addition of 0.3 g of tetrabutyl titanate, the mixture was heated to reflux, with stirring, and resultant water of reaction was removed from the system. The course of the reaction was monitored by means of titration [acid number] and water separation. Once an acid number smaller than or equal to 1 had been reached, the reaction was terminated. After modification of the apparatus, xylene and the excess of alcohol were removed by distillation in vacuuo, starting at 20 mbar; the bottom temperature at the end of the distillation process was 190° C. After cooling, the catalyst was washed with water and aqueous sodium carbonate solution. The volatile constituents were then removed by distillation from the organic phase, starting at 120° C. and 20 mbar. and the performance of the mixture as plasticizer was tested. Yield was 435 g (91%). Composition by GC area percent is: 29.8% di(2-ethylhexyl) succinate, 49.7% benzyl-2-ethylhexyl succinate, and 20.3% dibenzyl succinate.

Performance Testing

48.0 g of the substance to be tested were weighed into a glass beaker with magnetic stirrer rod and thermometer. The glass beaker was placed on a magnetic heater-stirrer in a holder between a lamp and a photocell. The change in light transmittance of the sample was recorded by way of a photocell. 2 g of polyvinyl chloride (Vinnolit® S4170; Vinnolit GmbH & Co. KG, Germany), and, by means of a pipette, 2 drops of PVC stabilizer (organotin stabilizer) were then added. The polyvinyl chloride was stirred into the plasticizer and the mixture was heated rapidly at from 5-8° C. per minute to 100° C., with stirring, and then further heated at an average of 3° C. per minute. Solvation temperature was considered to have been reached when for 3 successive minutes no further rise in the transmittance value was recorded by the photocell, and the polyvinyl chloride had been dissolved. Measurement was terminated when the temperature of the contents of the glass beaker reached 200° C. Low solvation temperature indicates good compatibility of the plasticizer and of the plasticizer preparations with polyvinyl chloride and indicates that high-speed processing is possible.

Hardness was determined by homogenizing and gelling a plasticizer-containing PVC powder mixture on a two-roll mill; the compounded material was then pressed to give test sheets, and hardness was determined by Zwick Shore-hardness equipment. Hardness (Shore A) was measured on smooth and even test samples measuring 6 mm×40 mm×50 mm. Low Shore A hardness values mean relatively soft products and are a measure of the efficiency of the plasticizers.