Seal swell additive

Abstract

A seal swell agent for a lubricating fluid is described. The invention relates to a seal swell agent for use in lubricating oils, such as engine oils, turbine oils, automatic and manual transmission, or gear, fluids, drivetrain and gear oils and hydraulic fluids. The seal swell agent comprises a diester of sorbitol or a derivative thereof and at least one carboxylic acid. The invention extends to the use of a diester of sorbitol or a derivative thereof and at least one carboxylic acid as a seal swell agent, and a method of maintaining seal integrity.

Claims

1. A lubricating oil comprising a base oil and a seal swell additive, wherein the seal swell additive comprises a diester of an isosorbide and a mixture of at least two carboxylic acids, wherein the diester is present in a concentration ranging from 0.01% to 15% by weight based on the total weight of the lubricating oil, wherein the mixture of at least two carboxylic acids consists of C.sub.4 to C.sub.12 carboxylic acids, wherein the base oil is selected from Group I to Group V base oils having a kinematic viscosity from 2 to 15 cSt at 100 C., and wherein the lubricating oil is selected from the group consisting of an engine oil, drivetrain oil, gear oil, manual and automatic transmission fluids, turbine oil, and hydraulic fluids.

2. A method of maintaining the seal integrity of natural and/or synthetic rubber seals in a lubricated system, the method comprising adding a seal swell agent to a lubricating oil present in the lubricating system, the seal swell agent comprising a diester of an isosorbide and a mixture of at least two carboxylic acids, wherein the diester is present in a concentration ranging from 0.01% to 15% by weight based on the total weight of the lubricating oil, wherein the mixture of at least two carboxylic acids consists of C.sub.4 to C.sub.12 carboxylic acids, wherein the lubricating oil comprises a base oil selected from Group I to Group V base oils having a kinematic viscosity from 2 to 15 cSt at 100 C., and wherein the lubricating oil is selected from the group consisting of an engine oil, drivetrain oil, gear oil, manual and automatic transmission fluids, turbine oil, and hydraulic fluid.

3. The lubricating oil of claim 1, wherein the seal swell agent is stable from 20 C. to 100 C.

4. The lubricating oil of claim 1, wherein the seal swell agent has a kinematic viscosity of at least 0.1 cSt, and up to 100 cSt at 100 C.

5. The lubricating oil of claim 1, wherein the seal swell agent is anhydrous.

6. The lubricating oil of claim 1, wherein the seal swell agent is oil-soluble.

7. The lubricating fluid oil of claim 1, wherein the diester is present in a concentration ranging from 0.05% to 15% by weight based on the total weight of the lubricating oil.

8. The lubricating oil of claim 1, wherein the diester is present in a concentration ranging from 0.1% to 15% by weight based on the total weight of the lubricating oil.

9. The lubricating oil of claim 1, wherein the diester is present in a concentration ranging from 2.5% to 15% by weight based on the total weight of the lubricating oil.

10. The lubricating fluid oil of claim 1, wherein the C.sub.4 to C.sub.12 carboxylic acids are selected from the group consisting of butanoic acid, hexanoic acid, octanoic acid, decanoic acid, dodecanoic acid, isobutanoic acid, isohexanoic acid, isooctanoic acid, isodecanoic acid, isododecanoic acid, methylhexanoic acid, dimethylhexanoic acid, ethylhexanoic acid, and dimethyloctanoic acid.

11. The lubricating oil of claim 1, wherein the C.sub.4 to C.sub.12 carboxylic acids are selected from the group consisting of butanoic acid, hexanoic acid, octanoic acid, decanoic acid, isobutanoic acid, isohexanoic acid, isooctanoic acid, isodecanoic acid, methylhexanoic acid, dimethylhexanoic acid, ethylhexanoic acid, and dimethyloctanoic acid.

12. The method according to claim 2, wherein the C.sub.4 to C.sub.12 carboxylic acids are selected from the group consisting of butanoic acid, hexanoic acid, octanoic acid, decanoic acid, dodecanoic acid, isobutanoic acid, isohexanoic acid, isooctanoic acid, isodecanoic acid, isododecanoic acid, methylhexanoic acid, dimethylhexanoic acid, ethylhexanoic acid, and dimethyloctanoic acid.

13. The method according to claim 2, wherein the C.sub.4 to C.sub.12 carboxylic acids are selected from the group consisting of butanoic acid, hexanoic acid, octanoic acid, decanoic acid, isobutanoic acid, isohexanoic acid, isooctanoic acid, isodecanoic acid, methylhexanoic acid, dimethylhexanoic acid, ethylhexanoic acid, and dimethyloctanoic acid.

Description

EXAMPLES

(1) The invention will now be illustrated further by the following non-limiting examples. All parts and percentages are given by weight of the total composition unless otherwise stated.

(2) 1) Preparation

(3) A variety of diesters of isosorbide were prepared by combining isosorbide and carboxylic acids, as listed in Table 1 below, in a batch reactor fitted with a mechanical stirrer, inert gas sparger, vapour column, condenser, and distillate receiver. The acid was present in slight excess from 5 to 15% molarthe higher excess of acid, the faster the reaction reaches completion. The pressure in the batch reactor was controlled by a vacuum pump that was attached to the reactor.

(4) Anywhere from 0.05 to 0.5 parts of catalyst per 100 parts of acid was added to the reaction mixture, and the mixture was heated to from about 180 C. to about 220 C. The catalysts used were not reaction specific and were selected from a group of effective catalysts. The group of effective catalysts includes but is not limited to tetrabutyltitanate, phosphorus acid, sodium hypophosphite, tin oxalate and others. The colour of the product was significantly lightened by using sodium hypophosphite as a co-catalyst at 0.02-0.1 (mass percent) concentrations. The pressure in the batch reactor was slowly reduced until sufficient conversion to the desired product was reached.

(5) The excess acid was removed from the reaction product by vacuum distillation. The crude ester was further purified by steam distillation and treatment with hydrogen peroxide/water, followed by filtration with filter-aid. The resulting ester generally was a clear, slightly yellow to brownish liquid possessing the typical properties outlined in Table 1 below.

(6) TABLE-US-00001 TABLE 1 Isosorbide diesters and their properties KV40 KV100 VI Flash (ASTM (ASTM (ASTM Point, Pour Point, Acid Chemistry D445) D445) D2270) C. C. Number Isosorbide Di-Hexanoate 17 3.7 104 210 57 <1 Isosorbide Di-Octoate 23 4.6 117 241 5.9 <1 Isosorbide Di-Decanoate Solid N/A <1 Isosorbide diester with C-810 26.9 5.9 173 244 8.3 <1 Caprylic/Capric Acid mix from Procter & Gamble Chemicals Isosorbide diester with 2-Ethyl- 32.3 4.5 48.1 231 45.5 <1 Hexanoic acid Isosorbide diester 3,5,5- 70.3 7.4 48 253 24.5 <1 trimethylhexanoic acid

(7) 2) Experimental Evaluation

(8) In order to evaluate the efficiency of various materials as seal swell agents, the conditions from the ASTM D7216-05 (Standard Test Method for Determining Automotive Engine Oil Compatibility with Typical Seal Elastomers) were used and followed. Materials were blended into PAO 4 (standard grade from global manufacturer) at several treat rates, or concentrations. Elastomer specimens of hydrogenated nitrile butadiene rubber (HNBR), polyacrylate or acrylic rubber (ACM), fluoropolymer elastomers (Viton) (FKM) and silicone rubber (VMQ) were obtained from ASTM authorized suppliers for GF-5 testing.

(9) Seal swell agents, both of the type falling within the scope of the present invention (agents 1 to 5) and a number of comparative agents (agents A to G), were blended with PAO at 66 C. for 1 hour at 0.5, 2.5 and 10% treat rates.

(10) Elastomer specimens were cut, and weight and volume values were measured before and after testing in accordance with ASTM D7216-05 method description.

(11) HNBR elastomers were tested by suspending the test specimen in prescribed amount of lubricating oils at 100 C. for 366 hours. All other elastomers were tested in a similar manner at 150 C. (according to ASTM test procedure). All tests were carried out in duplicate. At the end of the test period, the test rubber specimens were removed from the test oil and placed on lint-free tissue. Excess oil was removed from the specimens with clean, absorbent towel before the weights and volumes were measured. The difference in weight and volume of each of the specimens as a result of the exposure to the seal swell agents was calculated by comparing the measurements taken after the exposure with those taken before the exposure.

(12) The results for each of the tested seal swell agents on each of the elastomers are given below in Tables 2, 3, 4 and 5.

(13) TABLE-US-00002 TABLE 2 Seal Swell Agents with HNBR Elastomer 0.5% concentration 2.5% concentration 10% concentration Agent Mass Volume Mass Volume Mass Volume Name Agent Chemistry change, % change, % change, % change, % change, % change, % 1 Isosorbide 2.8 2.5 1 1.2 6.85 4.7 Dihexanoate 2 Isosorbide 2.9 2.7 1 0.8 2.5 3 Dioctanoate 3 Isosorbide 3.1 3 1.6 1.9 1.9 1.5 Didecanoate 4 Isosorbide Di-2- 3.9 3 1.5 1.7 1.7 0.9 Ethylhexanoate 5 Isosorbide Di- 2.6 2.4 2.4 1.9 1 2 3,5,5- trimethylhexanoate A Di-n-hexyl 2.9 2.8 1.2 1 4.4 3.9 Phthalate B Di-n-octyl 3.1 2.5 2.1 1.8 2.1 2.4 Phthalate C Di-n-dodecyl 3.1 2.2 2.8 2.4 1.3 1 Phthalate D Di-2-Ethylhexyl 3.6 2.3 3.2 1.9 2.7 1.9 Phthalate E 2-Ethylhexyl 2.19 2.2 0.99 0.7 benzoate F Di-isodecyl 1.64 1.2 adipate G PAO 4 (no 4.45 4.1 4.45 4.1 4.45 4.1 Additive)

(14) TABLE-US-00003 TABLE 3 Seal Swell Agents with FKM Elastomer 0.5% concentration 2.5% concentration 10% concentration Agent Mass Volume Mass Volume Mass Volume Name Agent Chemistry change, % change, % change, % change, % change, % change, % 1 Isosorbide 0.1 0 1.1 0.5 11.3 12 Dihexanoate 2 Isosorbide 0.2 0 0.6 0.2 5.9 5 Dioctanoate 3 Isosorbide 0 0.1 0 0.2 0.9 0.7 Didecanoate 4 Isosorbide Di-2- 0 0.3 0.1 0 0.9 0.3 Ethylhexanoate 5 Isosorbide Di- 0.4 0.6 0 0.3 1.5 3.9 3,5,5- trimethylhexanoate A Di-n-hexyl 0.1 0.1 0.2 0 1 0.4 Phthalate B Di-n-octyl 0.2 0 0.4 0.1 0.7 0.6 Phthalate C Di-n-dodecyl 0.1 0 0.28 0.1 0.5 0.4 Phthalate D Di-2-Ethylhexyl 0.2 0.7 0.3 0.5 0.7 0.3 Phthalate E 2-Ethylhexyl 0.6 0.3 0.8 0.3 benzoate F Di-isodecyl 0.3 0.2 adipate G PAO 4 (no 0.1 0 0.1 0 0.1 0 Additive)

(15) TABLE-US-00004 TABLE 4 Seal Swell Agents with ACM Elastomer 0.5% concentration 2.5% concentration 10% concentration Agent Mass Volume Mass Volume Mass Volume Name Agent Chemistry change, % change, % change, % change, % change, % change, % 1 Isosorbide 2.3 2.1 0.4 0.5 17 15 Dihexanoate 2 Isosorbide 2.5 1.9 1.5 1.2 4.3 3.7 Dioctanoate 3 Isosorbide 2.6 2.8 0.7 0.2 5.25 4 Didecanoate 4 Isosorbide Di-2- 1.4 0.6 0 0.8 2.2 1.4 Ethylhexanoate 5 Isosorbide Di- 2.7 3 1.7 1.3 1.4 0.4 3,5,5- trimethylhexanoate A Di-n-hexyl 2.9 2.2 1.8 1.5 4.9 4 Phthalate B Di-n-octyl 2.5 2 1.9 1.5 0.5 0.1 Phthalate C Di-n-dodecyl 3.1 3.2 2.6 2.2 1.2 1.1 Phthalate D Di-2-Ethylhexyl 2.5 2.7 2 1.4 1.8 1 Phthalate E 2-Ethylhexyl 2.6 1.8 1.2 0.5 benzoate F Di-isodecyl 1.2 0.7 adipate G PAO 4 (no 2.4 2 2.4 2 2.4 2 Additive)

(16) TABLE-US-00005 TABLE 5 Seal Swell Agents with VMQ Elastomer 0.5% concentration 2.5% concentration 10% concentration Agent Agent Mass Volume Mass Volume Mass Volume Name Chemistry change, % change, % change, % change, % change, % change, % 1 Isosorbide 17 15 7 6 17 19 Dihexanoate 2 Isosorbide 5 5 7 5 28 25 Dioctanoate 3 Isosorbide 5 3 8 5 13 12 Didecanoate A Di-n-hexyl 5 4 5 4 6.5 5 Phthalate B Di-n-octyl 5 3 6 5 16 13 Phthalate C Di-n-dodecyl 5 4 5 5 6 5 Phthalate D Di-2-Ethylhexyl 6.8 6 9.8 11 Phthalate E 2-Ethylhexyl 6 5 benzoate G PAO 4 (no 4.5 3 4.5 3 4.5 3 Additive)

(17) In the results, a positive number corresponds to an increase in mass and/or volume due to exposure to the seal swell agents, and a negative number corresponds to a decrease in mass and/or volume due to exposure to the seal swell agents. A good result in these tests is a positive numberthe higher the number, the better performance the seal swell agent exhibits.

(18) The results indicate that isosorbide diesters, e.g. agents 1, 2, 3, 4 and 5 are as effective as similar molecular weight phthalates, i.e. comparative agents A, B, C and D in preventing weight loss and volume shrinkage of the HNBR elastomer. Whereas, for the FKM and ACM elastomers, the effectiveness of agents 1, 2, 3, 4 and 5 were similar to that of comparative agents A, B, C and D at lower treat rates but significantly more effective at higher concentrations.

(19) Any or all of the disclosed features, and/or any or all of the steps of any method or process described, may be combined in any combination.

(20) Each feature disclosed herein may be replaced by alternative features serving the same, equivalent or similar purpose. Therefore, each feature disclosed is one example only of a generic series of equivalent or similar features.

(21) The above statements apply unless expressly stated otherwise. The term specification, for these purposes, includes the description and any accompanying claims, abstract and drawings.