Dilauryl 3,3 -thiodipropionate

A.ntioxidants. PhenoHc antioxidants, added at about 0.1—0.5 phr, are usually chosen from among butylated hydroxytoluene [128-37-0] (BHT), and Nnonylphenol [104-40-5] for Hquid stabilizer formulations and bisphenol A [80-05-7] (2,2-bis-(/)-hydroxyphenyl)propane) for the soHd systems. Low melting thioesters, dilauryl thiodipropionate [123-28-4] (DLTDP) or distearyl thiodipropionate [693-36-7] (DSTDP) are commonly added along with the phenoHcs to enhance their antioxidant performance. Usually a 3 1 ratio of thiodipropionate to phenoHc antioxidant provides the desired protection. Most mixed metal stabilizer products contain the antioxidant iagredient. 

The synergistic effect of a hydroperoxide decomposer, eg, dilauryl thiodipropionate [123-28-4] (34), and a radical scavenger, eg, tetrakis[methylene(3,5-di-/ f2 butyl-4-hydroxyhydrocinnamate)]methane (9), ia protecting polypropylene duting an oxygen-uptake test at 140°C is shown ia Table 3. 

Tetiakis[methylene(3,5-di-/( /f-butyl-4-hydioxyhydio-ciiinamate)]methane. Dilauryl thiodipropionate. 

The peroxide decomposer will drastically reduce the number of radicals, which can then be more effectively mopped up by the chain-breaking materials. A widely used combination is 4-methyl-2,6,di-t-butylphenol and dilauryl thiodipropionate. It is possible to envisage most powerful combinations where a chain-breaking antioxidant, a regenerating agent, a peroxide decomposer, a metal deactivator and an ultraviolet absorber are all employed together. 

Figure II. 8. Synergistic effect of two antioxidants in polypropylene (DLTP=dilauryl thiodipropionate. MCPC-2,2 -methylenebis[6-(l-melhylcyclohexyl-p-cresol)]. (After Leyland and Watls )...

Dilauryl thiodipropionate Didodecyl 3,3 -thiodipropionate Thiobis(dodecyl propionate) Thiodipropionic acid dilauryl ester Bis(dodecyloxycarbonylethyl) sulfide... 

Decomposition of Peroxides by Various Stabilizers. The efficiency of tert-butyl hydroperoxide decomposition in tert-butyl alcohol by various additives was determined (Table 9). Under the conditions of these experiments, the phenolic antioxidants and dilauryl thiodipropionate had little or, often, no effect on the hydroperoxide decomposition. The three zinc salts effectively inhibited peroxide decomposition. This effect might briefly inhibit the onset of substrate oxidation under weathering-test conditions, but the peroxide would decompose whenever its concentration reached a sufficient level to permit significant light... 

Dilauryl thiodipropionate, antioxidant useful in cosmetics, 7 830t Dilavase, molecular formula and structure, 5 11 It... 

Phenolic antioxidants together in combination with thiodiprop-ionate compounds as synergists have been used for this purpose, e.g., n-octadecyl-3-(4 -hydroxy-3, 5 -di-ferf-butylphenyl)propionate and dilauryl thiodipropionate (14). These systems have a tendency to develop colored impurities as a byproduct of their antioxidant function. The production of colored impurities becomes particularly evident in spray drying processes that utilize partially inert atmospheres (12). 

An improved antioxidant composition contains l,l,3-tris(2-meth-yl-4-hydroxy-5-tert-butyl phenyl)butane, (Topanol CA). Here also in addition dilauryl thiodipropionate is used as a co-stabilizer (12). 

The kinetics of the decomposition of Tetralin and tert-butyl hydroperoxides by dilauryl thiodipropionate were determined in the temperature range 30°-90°C. The reaction had an induction period which was eliminated by acetic acid but not by dilauryl sulfinyldipropionate. The rate equation... 

Dilauryl Thiodipropionate (DLTP). DLTP (American Cyanamid) m.p., 39°C. was used without further purification. A series of experiments in which recrystallized material was used gave identical results to experiments in which the commercial sample was used. 

Kinetic Procedure. In a typical experiment 0.82 gram Tetralin hydroperoxide (5 X 10"3 mole) and 0.3214 gram dilauryl thiodipropionate... 

Figure 1. First-order plot for the decomposition of Tetralin hydroperoxide (4.8 X 10" M) by dilauryl thiodipropionate (2.47 X 10 M) at 80°C.

Products of the Reaction. A solution containing 5 X 10"2 mole/liter hydroperoxide and 2 X 10"2 mole/liter dilauryl thiodipropionate was allowed to react at 70 °C. until no hydroperoxide remained. A brown resinous precipitate was formed which was filtered, washed, and dried in vacuo. The infrared spectrum of the solid revealed the presence of —O—SOo— groups and the presence of an ortho-substituted aromatic compound, but no further details of its constitution could be obtained. This precipitate was not formed in the kinetic experiments which had a... 

Figure 3. Order of reaction with respect to dilauryl thiodipropionate at 80° C.

Effect of Dilauryl Sulfinyldipropionate (DLTP Sulfoxide ). The addition of dilauryl sulfinyl dipropionate to a solution containing Tetralin hydroperoxide and dialuryl thiodipropionate had little effect on the length of the induction period, but the rate of the subsequent reaction was increased. Comparison of the rate of decomposition of the hydroperoxide (5.0 X 10 2 mole/liter) by dilauryl thiodipropionate (1.60 X 10"2 mole/liter) or dilauryl sulfinyl dipropionate (1.60 X 10"2 mole/liter)... 

Figure 4. Decomposition of Tetralin hydroperoxide (5.0 X 10 M) by (A) dilauryl thiodipropionate (1.6 X 10 M) and by (B) dilauryl sulfinyldipropionate...

Effect of Acetic Acid. Addition of acetic acid (35 X 10 2 mole/ liter) to a solution containing Tetralin hydroperoxide (2.0 X 10 2 mole/ liter) and dilauryl thiodipropionate (2.5 X 10 2 mole/liter) not only eliminated the 60-minute induction period but substantially increased the rate of reaction (Figure 5). The over-all rate equation in the presence of acetic acid at 70°C., determined by the initial slopes method was... 

Effect of a Phenolic Antioxidant. The rate of decomposition of a solution containing the hydroperoxide (5.0 X 10 2 mole/liter) dilauryl thiodipropionate (2.5 X 10 2 mole/liter) and l,l,3-tris(2 -methyl-5 -fert-butyl-4 -hydroxyphenyl) butane (2.5 X 10"2 mole/liter) at 80°C. was identical with that containing no phenolic compound. In addition no formation of polymer was observed when solutions of Tetralin hydroperoxide and dilauryl thiodipropionate were allowed to react at 70 °C. in sealed tubes in the presence of inhibitor-free acrylonitrile in nitrogen... 

Decomposition by Distearyl Thiodipropionate. The rate of decomposition at 80 °C. of Tetralin hydroperoxide by distearyl thiodipropionate was very similar to the rate with dilauryl thiodipropionate although the induction period was longer (Figure 6). 

Figure 5. Decomposition of Tetralin hydroperoxide by dilauryl thiodipropionate in the presence of acetic acid at 70° C.

Table II. Second-Order Rate Constants for the Decomposition of Tetralin Hydroperoxide by Dilauryl Thiodipropionate in Chlorobenzene...

A solution containing 5.0 X 10 2 mole/liter terf-butyl hydroperoxide and 2.5 X 10 2 mole/liter dilauryl thiodipropionate was allowed to react at 80 °C. until no hydroperoxide remained. A slight precipitate was obtained which could not be identified. Vapor phase chromatography of the residual solution at 100°C. on a column containing 20% w/w di-n-decyl phthalate on 60-80 mesh C22 firebrick gave tert-butyl alcohol as the main identifiable product. 

The mechanism proposed so far takes account of the induction period and initial stages of the reaction only, and it is difficult to see how it can account for the large amount of hydroperoxide decomposed by the sulfur compound. However, Tetralin hydroperoxide is decomposed catalytically by acids (5). Although in the absence of dilauryl thiodipropionate the decomposition of Tetralin hydroperoxide in the presence of acetic acid at 70 °C. was very slow, if the acid species is a much stronger acid than acetic—e.g., a sulfonic acid as seems likely from the nature of the products of the reaction, the rate of acid-induced decomposition may be comparable with the rate of decomposition by the sulfur compound. Some evidence that acid-induced decomposition does occur at some stage in the over-all reaction is found in the presence of an ortho substituted aromatic compound in the solid product of the reaction. The acid catalyzed decomposition of Tetralin hydroperoxide follows the path of Reaction 14 (5) to give y-(o-hydroxyphenyl)butyraldehyde. This forms a brown resin which is mainly the aldol of this aldehyde (cfthe resin obtained in this work). 

The similar rate of decomposition of Tetralin hydroperoxide by distearyl and dilauryl thiodipropionate at 80 °C. is of interest when compared with the formers better antioxidant properties in polypropylene at 140 °C. Tests showed that the stearyl compound was superior to the lauryl compound as a synergist, in the presence of a phenolic antioxidant, in delaying the embrittlement of polypropylene sheet in an air oven at 140°C. (Table IV). 

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