Исследование влияния количества добавок на свойства эфиров адипиновой кислоты

P olyvinylchloride contains up to 56% chlorine, so it is not combustible in pure form. However, with the addition of plasticizers the combustibility of materials based on it increases, a dramatic change is observed when the content of additives is more than 25% [1–6].

It is known from the researches that low combustibility indices of polymeric materials are given by phosphoruscontaining compounds [7–13]. The most effective flame retardants are triarylphosphates. However, phosphorus-containing plasticizers are not widely used, as they adversely affect a number of physical and mechanical properties of the compositions: low-temperature flexibility, volatility, thermal stability and color stability; use of them also complicates the technology of processing of polymeric materials [14–17].

Adipic acid esters don’t possess these disadvantages, they also give PVC materials stability at low temperatures, resistance to UV light, high resistance to migration to gasoline and oil [18–22].

Therefore, we have studied mixed plasticizers based on adipic acid esters with the addition of small amounts of aryl-containing phosphates.

MAIN PART

Experimental part

We have conducted research on the preparation of a mixture of adipate of aliphatic alcohols and small amount of phenoxypropylated phosphate with low flammability PVC compounds.

This paper describes methods for the synthesis, physico-chemical properties of symmetrical and asymmetrical adipate of aliphatic alcohols and phenoxy-propylated phosphate, results of their testing as cable tracks.

DEVELOPMENT OF NEW POLYMER MATERIALS • РАЗРАБОТКА НОВЫХ ПОЛИМЕРНЫХ МАТЕРИАЛОВ

The method of obtaining symmetrical adipate of cyclic aliphatic alcohols

The production of symmetrical adipate is carried out in the presence of concentrated sulfuric acid (catalyst) in a solution of azeotrope waterpicker toluene, at reflux of the latter. The molar ratio taken for the reaction of alcohols and adipic acid is 2.2:1. The reaction is controlled by the amount of produced water, and acid number of ester. After cooling, the reaction mass is washed sequentially from the catalyst with a 5% solution of alkali and water to a neutral reaction. The resulting esters are dried over freshly calcined sodium sulfate and the solvent is distilled under vacuum. The yield of target products is 96–98%.

The method of obtaining asymmetric adipate of cyclic and acyclic aliphatic alcohols

Asymmetric esters of adipic acid are obtained in two stages. At the first stage, under the conditions described above at the molar ratio acid: alcohol = 1:1, monoesters of acyclic alcohols are synthesized. Further, they are isolated with the use of 10% solution of sodium hydroxide with subsequent treatment with hydrochloric acid. At the second stage, the obtained monoesters under the same conditions react with cyclohexylcarbinol at the molar ratio acid: alcohol = 1:1,2. The outcome of asymmetric esters is not less than 96%.

Physical and chemical parameters of the synthesized esters of adipic acid are shown in table 1.

The table shows that the structure of alcohol radicals in the obtained esters significantly affects the low-temperature properties of esters. The replacement of two acyclic alkyl radical in the cyclic structure results is likely to receive more rigid and less flexible molecules. Replacement of alkyl groups of normal structure by branched allows obtaining adipic acid esters with a pour point below –60oC.

Phosphate of oxypropylated phenol was obtained in two stages. At first stage, oxypropylated phenol was syn- thesized. Then by means of esterification of it with adipic acid the final product was obtained.

Methods of phenol oxypropylating

94.0 g (1 mol) of phenol and 1.6 g (1.0 % by weight of the total load) of sodium hydroxide catalyst are loaded in the reactor equipped with a stirrer, refrigerator, thermometer, lowered into the liquid, and a drop funnel. Mixing and heating of the flask is launched and remove air by nitrogen blowing. Upon reaching the desired temperature, 58.0 g (1 mol) of propylene oxide is gradually introduced from the drop funnel. After stopping the feed, the reaction mixture is stirred for 1.5 hours without changing the temperature, then it is cooled. To remove the catalyst, the mixture is neutralized with the calculated amount of sulfuric acid and filtered. After drying with anhydrous sodium sulfate it is distilled under vacuum. Outcome is 1-phenoxy-2-propanol 147.1 g (96.8%), d204 = 1,063 g/ml, n20D = 1,525, m.w. 152, the degree of oxypropylating – 1.

Method of esterification of phosphoric acid

456 g (3.1 mol) of 1-phenoxy-2-propanol is added to a mixture of 153.3 g (1.0 mol) phosphorus oxychloride and 1.0 g (0.01 mol) anhydrous magnesium chloride, heated to 45°C for three hours. The reaction mixture is stirred and heated to 80oC/30 mm Hg within eight hours. 25 g (0.27 mol) of epichlorohydrin was added to the reaction mixture and further heating at 80oC lasted for another 3 hours. The resulting mixture is alternately washed with 1% sodium carbonate solution and water. Filtration is performed after drying at 90oC and 130 mm Hg. The outcome of phosphate of oxypropylated phenol is 485.0 g (97%), acid number is 0.07 mg KOH/g, ester number is 336 mg KOH/g, m. w. 500.

In order to study the obtained plasticizers for flammability, their mixtures were composed on the basis of the obtained esters of adipic acid with the addition of various amounts of phosphate of oxypropylated phenol.

Table 1

Physical and chemical properties of adipic acid esters (ROCO(CH2)4COOR1)

№ ester	R	R1	Boiling point at 12 mm Hg, o C	Acid number, mg КОН/g	Ester number, mg КОН/g	d20 4	20 nD	Pour point, oC
1	n -С6Н13	Cyclo-С 6 Н 11 СН 2	210–235	0.08	344	1.4592	0.9734	–47
2	Cyclo-С 6 Н 11 СН 2	Cyclo-С 6 Н 11 СН 2	257–260	0.08	328	1.4759	1.0202	+1
3	2-ethylhexyl	Cyclo-С 6 Н 11 СН 2	245–255	0.08	310	1.4586	0.9568	–60

DEVELOPMENT OF NEW POLYMER MATERIALS • РАЗРАБОТКА НОВЫХ ПОЛИМЕРНЫХ МАТЕРИАЛОВ

Table 2

Indicators of flammability for mixtures of plasticizers (sec)

№ ester	Phosphate of oxypropylated phenol, % weight.
	0	2	4	6
1	28.7	28.2	25.5	26.1
2	29.0	28.7	26.5	27.0
3	28.0	27.7	25.0	25.9

Discussion of results

To determine the effectiveness of the developed mixtures of plasticizers, the change in the combustibility of PVC-plastic cable samples from the amount of phosphate of oxypropylated phenol was studied.

Tests of plasticizers in the formulation of cable plasticate brand O-40 composition OM-40

To obtain cable plastics, a suspension for mixing plasticizers and stabilizers was initially prepared at speed of 8000 rpm. Further, PVC composition was prepared in a rotary mixer at 120oC and 70 rpm for 30 minutes. Samples of plastic were expanded at 145–150oC for 7–10 min.

Tests of finished samples of cable plastics were carried out in accordance with state standard 5960-72 with changes 3-9 «PVC Elastron for isolation and protective environments of wires and cables». The test results are shown in table 2.

The results show that the flammability of the samples depends on the structure of the alcohol radical in the adipate molecule and on the content of phosphates in the mixture of plasticizers.

The results given in table 2 show that the samples of asymmetric ester of adipic acid with a content of 4% by weight of phosphate oxypropylated phenol in terms of flammability provide lower values than commercially available (according to state standard 5960-72 with changes 3-9 for cable plastic compound of the O-40 brand the norm makes no more than 30 sec). An increase in the amount of phosphate of oxypropylated phenol leads to a deterioration in the flammability of plastics obtained with this mixture of plasticizers. Namely small quantities of additives to achieve optimal results – maintaining good compatibility adipate with PVC and improved physico-mechanical properties of PVC compounds based on them, as well as giving a new quality, reducing flammability.