GB2185745A - Branched esters of halogenated compounds - Google Patents

Abstract

The present invention relates to branched esters of trihaloneopentyl alcohols and a method of their preparation. The esters have the general formula <IMAGE> wherein each X is independently Br, Cl or H provided that at least one of X is Br or Cl; R1 is a C1-5 alkyl or substituted C1-5alkyl radical and R2 is a radical (CH2)nCH3 in which n is an integer of 1 to 10, and R3 is H or a C1-5alkyl or substituted C1-5alkyl radical. The esters are prepared by the esterification of the free alcohol with the corresponding organic acid in the presence of an acidic catalyst. The new branched esters, covered by the above general formula, were found to be useful as flame retardants for hydraulic fluids possessing outstanding hydrolytic stability.

Description

SPECIFICATION Branched esters of halogenated compounds The present invention relates to new branched esters of halogenated compounds. More particularly, the invention relates to new branched esters oftrihaloneopentyl alcohols which are useful as effective liquid flame retardant in general andforhydraulicfluidsin particular.

Hydraulic fluids are of high importance in mechanical systems where power has to be applied from a generator to a point orto a multitude of points remote from the generator. Such systems are widely used in automotive systems, airplanes, ships, in industry and in many military applications.

To be useful in hydraulic systems, a fluid has to meet a series of physical properties such as viscosity and density as well as chemical properties such as heat stability hydrolytic stability and non-corrosiveness. In many applications, fire-resistance of the fluid is of great importance, and of course, the fluid should not ignite spontaneously at the opening temperature. The many rigorous requirements have resulted in the provision of numerous specialty compositions whereby, much as in the lubricant and motor fuel arts, additives of various kinds have been admixed with the base fluid forthe purpose of imparting to it one or more ofthe properties in which the base stock is defficient.However, it iswell-known that properties such as thermal stability and resistance to hydrolysis generally cannot be conferred upon a fluid by the use of an additive and although fire-retardant additives for fluids are known, such additives are of little value for these particular properties.

There are known a number of patents dealing with the subject, utilising various compositions as hydraulic fluids. Thus according to U.S. Patent No. 3,290,253, chlorine-substituted diarylalkanes are suggested as hydraulic fluids, possessing improved fire-retardancy and viscosity properties. According to U.S. Patent No.

4,187,188, dialkanoate derivatives of dibromoneopentyl glycols are suggested as dielectric agents which impart also fire retardancy and improved physical properties. While the above known reagents might be quite useful in respect to some required properties, they suffer from a relatively poor hydrolytic stability. This can be also noticed from the disclosure in the above U.S. Patent No. 4,187,188 (see Col. 2, lines 62-3),where hydrolytic stabilizers are suggested to be also incorporated.

Halogenated neopentyl alcohols are known compounds encountered in many syntheses as reagents for various compounds. They are easily obtained by the hydrohalogenation of pentaerythritol and are commercially available. Derivatives of halogenated neopentyl alcohol are characterized bythermal stability which is higher than that of the free alcohol.

It has now been found according to the present invention, that branched esters oftrihalonepentyl alcohol having the general formula:

wherein each X is independently Br, Cl or H, provided that at least one of X is Br or Cl; R1 is a lower alkyl or substituted lower alkyl radical, R2 is a radical (CH2)n CH3 in which n is an integer of 1 to 10 and R3 is H or a lower alkyl or substituted lower alkyl radical, are new compounds possessing outstanding hydrolyticstability, being also useful as flame retardants for hydraulic fluids. The term of lower alkyl radical has the general known meaning containing between 1 and 5 carbon atoms.

Among the specific new branched esters oftrihaloneopentyl alcohol included in the above general formula, the following compounds can be mentioned: 1. 3-bromo-2,2-(bromomethyl)-propyl-2-ethyl hexanoate:

2. 2,2-(bromomethyl)-propyl-2-ethyl hexanoate:

3. 3-Chloro-2,2-(bromomethyl)-propyl-2-ethyl hexanoate.

4. 3-bromo-2,2-(bromomethyl)-propyl-2-ethyl butyrate.

5. 3-bromo-2,2-(bromomethyl )-propyl-pivalate.

6. 3-bromo-2,2-bromomethyl-propyl-2,2 dimethyl pentanoate.

The branched esters oftrihaloneopentyl alcohols according to the present invention, are easily obtained by the esterification of the free alcohol with the corresponding acid in the presence of an acidic catalyst such as sulfuric acid or p-toluene sulfonic acid. During the reaction of esterification, water is removed and the final product is recovered. The preparation can be carried out either in the presence of an inert solvent (such as toluene or other hydrocarbon) or without any solvent, the latter serving merely as a vehicle to remove the waterfromthe reaction.

Atypical example of the branched esters oftrihaloneopentyl alcohol, is 3-bromo-2,2(bromomethyl)-propyl-2 ethyl hexanoate. This compound appears as a transparent liquid, having a density of 1.52 g/cc. It is characterized by its high bromine content (53% Br2) which imparts flame resistance to the hydraulic fluid. The boiling point at atmospheric pressure is above 200 degres C, the measurement at 0.5-0.7 mm Hg being 135-140 degrees C. Another beneficial property of this compound is its relatively low freezing point (below -20 C) which is quite important for hydraulic fluids used in cold areas.

The thermal stability of this ester is given in the following Table 1.

Table 1 The thermal stability of3-bromo-2,2-(bromomethyl) propyl- 2 ethyl-hexanoate % loss ofweight Temp. (degrees C} 5 190 10 205 20 220 50 250 Since the tested compound is a liquid, the loss of weight includes also the amount of volatilized material, which is quite appreciable attemperatures above 200 degrees C.

One of the most important properties of the new compounds according to the present invention, is their outstanding hydrolytic stability, which is particularly required for hydraulic fluids. Several accelerated hydrolyticstabilitytestswere carried out by maintaining these composition under boiling in the presence of distilled waterfor 264 hours (11 days). The stability was determined by analysis of the alcohol formed. For comparison purposes, tests were carried out with isomeric compounds, possessing the same general formula, butwithoutthe branched structure. In these tests it was found that compounds according to the present invention, i.e. possessing the branched structure, did not liberate free alcohol even after boiling for 264 hours.However, with the isomeric compounds, which do not possess the branched structure, significant amounts offree alcohol were found. These findings are in accordance with the Inventors assumption thatthe branched structure imparts the outstanding hydrolytic stability to the new compounds.

Owing to their very good fire-retardant properties, the compounds according to the present invention are particularly useful in hydraulic fluids for hydraulic pressure devices that are employed under conditions wherein any leak or break in the hydraulic system could provide great danger from fire. The low pour points of the compounds, permitfabrication of pressure devices which are destinated for use in cold climates and their good vapor pressure characteristics and stability to heat, allows use of the same devices in hot environments.The viscosity characteristics make them of great utilityforthe transmission of power in a hydraulic system having a pump therein which supplied powerforthe system, e.g. in a fluid motor comprising a constant- or variable discharge piston pump which is caused to rotate by the pressure of the hydraulic fluid of the system. The compounds according to the present invention, are also useful for lubricating the frictional, moving parts of such hydraulicsystems.

Another important useful property of the new branched esters according to the present invention is their viscosity. Itwasfound that the viscosity is much higher than that of the corresponding esters possessing a non-branched structure. Thus, the viscosity viscosity of 3-bromo-2,2(bromomethyl) propy-2-ethyl-hexanoate is about 95 cps, compared with 45 cps of its corresponding isomer possessing a non-branched structure.

In orderto further illustrate the nature of the invention and the manner of practicising it, thefollowing Examples are presented for clearness of understanding only and no limitation should be understood therefrom.

Example 1 Preparation of3-bromo-2,2(bromomethyl)-propyl-2-ethyl-hexanoate.

An amount of 650 g oftrinol was heated with 302 g of 2-ethyl hexanoic acid in the presence of 10 ml of concentrated sulfuric acid (as catalyst) and 1200 ml oftoluene, in a vessel provided with a reflux condenser and a dean-starkdevicefor continuous removal of water until the theoretical amount ofwaterwas removed.

The product obtained consisted of 874 9 of 3-bromo-2,2(bromomethyl) propyl-2-ethyl-hexanoate (yield 97%) andwas identified by NMRanalysis: (CDCl33 in ppm) 4.18 (s,2H); 3.54 (s,6H); 2.31 (m,1H; 1.56(m,4H); 1.29 (m,4M); 0.91 (m,6H).

The infra red spectrum of the compound was as follows: KBr (in cam~1) 2980-28000-H (carbon-hydrogen absorption)

(carbonyl-ester absorption) Example 2 Preparation of3-bromo-Z2(bromomethyl)-propyl-2 ethyl-hexanoate An amount of 162 g of 3-bromo-2,2(bromomethyl)-propanol was treated with 86 g of 2-ethyl hexanoic acid in the presence of 89 of p-toluene sulfonic acid as catalyst The mixture was stirred and heated to 120-130 degrees C under vacuum (water aspirator of about 40 mm Hg)to remove the water produced during the esterification. After six hours, itwas found by thin layer chromatography that the reaction was completed, obtaining 214 9 of the ester (95%yield).

Example 3 Preparation of3-bromo-2,2-(bromomethyl)-propyl-pivalate An amount of 162 g of 3-bromo-2,2(bromomethyl)-propanol was treated with 56 g of pivalic acid (2,2-dimethyl propanoic acid) in 500 ml toluene. Sulfuric acid conc. (3g) was added as catalyst and thewhole mixture was heated to reflux, the water produced being continuously removed. After 5 hours, the reaction was completed and the product obtained amounted to 188 g (92%yield).

Claims (12)

1. Branched esters oftrihaloneopentyl alcohol having the general formula:

wherein each X is independently Br, Cl or H provided that at least one of X is Br or Cl; R1 is a lower alkyl or substituted lower alkyl radical and R2 is a radical (CH2)n OH3 in which n is an integer of 1 to 10, and R3 is H, a loweralkyl or substituted loweralkyl radical, possessing outstanding hydrolyticstability.

2. Branched esters according to Claim 1, wherein said compound is 3-bromo-2,2-(bromomethyl)propyl-2-ethyl hexanoate.

3. Branched esters according to Claim 1,wherein said compound is 3-bromo-2,2-(bromomethyl)propyl-pivalate.

4. Branched esters according to Claims 1 to 3, wherein said esters are useful as flame retardantsfor hydraulicfluids.

5. Branched esters according to Claim 4, wherein other known additives are also incorporated.

6. A method for the preparation of branched esters according to Claims 1 to 3, wherein said esters are prepared by the reaction oftrinol with the corresponding organic acid in the presence of an acidic catalyst

7. A method according to Claim 6, wherein said acidic catalyst is selected from concentrated sulfuric acid and p-toluene sulfonic acid.

8. A method according to Claims 6 or 7, wherein the reaction is carried out in the presence of an inert solvent.

9. A method according to Claim 8, wherein said inert solvent is an aromatic hydrocarbon.

10. A method according to Claim 9, wherein said aromatic hydrocarbon istoluene.

11. A method according to Claims 6to 10, wherein the reaction is carried out under reflux ata temperature close to the boiling.

12. Branched esters oftrihaloneopentyl alcohol substantially as described in the specification and claimed in any ofthe Claims 1 to 3.