Bicyclic thioamides as additives for lubricating oils

Abstract

A composition comprising: (a) from 0.1% to 20% of at least one bicyclic thioamide of formula I: 1

Description

BACKGROUND

[0001] This invention relates generally to bicyclic thioamides useful as additives for lubricating oils.

[0002] Zinc dialkyldithiophosphates (ZDDP) are widely used as lubricant additives. The principal disadvantages of these compounds are that an ash residue is produced by the zinc as the additive is consumed, and that phosphorus is known to affect the efficiency of catalytic converters in motor vehicles, thereby causing emissions problems. Cyclic compounds useful as lubricant additives are disclosed in U.S. Pat. No. 6,187,722. However, the compounds disclosed therein are imidazolidinethiones which are not within the scope of the present invention.

[0003] The problem addressed by this invention is to find additional non-metallic, non-phosphorus-containing oil-soluble additives for lubricating oils.

STATEMENT OF INVENTION

[0004] The present invention is directed to a composition comprising:

[0005] (a) from 0.1% to 20% of at least one bicyclic thioamide of formula I: 2

[0006] wherein X is O, S, NR6 or CR7R8; R1, R2, R4, R5, R7 and R8 independently are hydrogen, alkyl, alkenyl, aryl or aralkyl; R3 and R6 independently are hydrogen, alkyl, alkenyl, aryl, aralkyl, alkanoyl or aroyl; and bond “a” is a single or double bond; and

[0007] (b) a lubricating oil.

[0008] The present invention is further directed to a method for improving the anti-wear characteristics of a lubricating oil by adding from 0.1% to 20% of a compound of formula I.

[0009] The present invention is further directed to a lubricating oil composition containing the reaction product of a compound of formula (I) with an imine; an unsaturated carboxylic acid or ester; an isocyanate or isothiocyanate; or an alkyl, alkenyl or aralkyl group bearing a leaving group.

[0010] The present invention is further directed to a compound having formula (IV), as depicted herein, and a composition containing the compound and a lubricating oil.

DETAILED DESCRIPTION

[0011] All percentages are weight percentages based on the entire composition described, unless specified otherwise. An “alkyl” group is a saturated hydrocarbyl group having from one to twenty-two carbon atoms in a linear, branched or cyclic arrangement, and having from 0 to 2 oxygen, nitrogen or sulfur atoms. Substitution on alkyl groups of one or more halo, hydroxy, alkoxy, alkanoyl or amido groups is permitted; alkoxy, alkanoyl and amido groups may in turn be substituted by one or more halo substituents. In one preferred embodiment, alkyl groups contain from two to twelve carbon atoms and from 0 to 1 oxygen, nitrogen or sulfur atoms; in another preferred embodiment, alkyl groups contain from 4 to 22 carbon atoms; in another preferred embodiment, alkyl groups contain no heteroatoms. An “alkenyl” group is an “alkyl” group in which at least one carbon-carbon single bond has been replaced with a double bond. An “aryl” group is a substituent derived from an aromatic compound, including heterocyclic aromatic compounds having heteroatoms chosen from among nitrogen, oxygen and sulfur. An aryl group has a total of from five to twenty ring atoms, and has one or more rings which are separate or fused. Substitution on aryl groups of one or more halo, alkyl, alkenyl, hydroxy, alkoxy, alkanoyl or amido groups is permitted, with substitution by one or more halo groups being possible on alkyl, alkenyl, alkoxy, alkanoyl or amido groups. An “aralkyl” group is an “alkyl” group substituted by an “aryl” group. A “lubricating oil” is a natural or synthetic oil, or a mixture thereof, having suitable viscosity for use as a lubricant, e.g., as crankcase oil in an internal combustion engine, automatic transmission fluid, turbine lubricant, gear lubricant, compressor lubricant, metal-working lubricant, hydraulic fluid, etc.

[0012] Preferably, at least one of R1, R2, R3, R4, R5, R6, R7 and R8 is alkyl, alkenyl, aryl or aralkyl; more preferably at least two of R1, R2, R3, R4, R5, R6, R7 and R8 are alkyl, alkenyl, aryl or aralkyl. In one embodiment of the invention at least one of R1, R2, R3, R4, R5, R6, R7 and R8 is aryl, aralkyl, C4-C22 alkyl or C4-C22 alkenyl; more preferably at least one of R1, R2, R3, R4, R5, R6, R7 and R8 is C4-C22 alkyl or C4-C22 alkenyl; and most preferably at least one of R1, R2, R3, R4, R5, R6, R7 and R8 is C6-C22 alkyl. Preferably, X is NR6. The composition of the present invention includes at least one compound of formula (I). In one embodiment of the invention, the composition contains at least two compounds of formula (I), and more preferably contains at least three compounds of formula (I).

[0013] In one embodiment of the invention, bond “a” is a double bond, and the compound of formula (I) can be represented by formula (II) 3

[0014] In one embodiment of the invention, a compound of formula (II) is prepared, for example, by the cycloaddition reaction of an isothiocyanate and a substituted or unsubstituted furan, thiophene, pyrrole or cyclopentadiene, as shown below in Scheme 1: 4

[0015] Preferably, R3 is C6-C22 alkyl, C6-C22 alkenyl, aryl or aralkyl; more preferably R3 is C6-C22 alkyl or aryl; most preferably R3 is C8-C22 alkyl. Preferably, R1, R2, R3, R4, R5, R6, R7 and R8 contain no heteroatoms. Preferably, at least one of R1, R2, R3, R4 and R5 is aryl, aralkyl, C4-C22 alkyl or C4-C22 alkenyl; more preferably C6-C22 alkyl or C6-C22 alkenyl; and most preferably C10-C22 alkyl. Preferably, X is NR6.

[0016] In one embodiment of the invention, bond “a” is a single bond, X is NR6, and the compound of formula (I) can be represented by formula (III). 5

[0017] In one embodiment, a compound of formula (III) in which R3 and R6 are hydrogen, and R4 and R5 are hydrogen, is prepared from a 1,4-diketone, HCN and ammonium sulfide, in a two-step process, as shown below in Scheme 2: 6

[0018] The NH amino group of the product optionally is further functionalized by reaction with alkyl, alkenyl, aralkyl, alkanoyl or aroyl groups having suitable leaving groups capable of being displaced by the NH group. For example, suitable leaving groups include iodide, bromide, chloride, tosylate, mesylate and triflate.

[0019] In a preferred embodiment of the invention, the thioamide group or a primary or secondary amino group of the compound of formula (I) is further functionalized by reaction with imines of formula R9N═CR10R11; unsaturated carboxylic acids or esters of formula CHR12═CR13COOR14; isocyanates, R15NCO, or isothiocyanates, R15NCS; or R16Y; wherein R10, R11 and R14 independently are hydrogen, alkyl, alkenyl, aryl or aralkyl; R16 is alkyl, alkenyl or aralkyl; R12 and R13 independently are hydrogen or C1-C4 alkyl; R9 and R15 independently are alkyl, alkenyl, aryl or aralkyl; and Y is a suitable leaving group capable of being displaced by the nitrogen or the sulfur of a thioamide group, or by a primary or secondary amine nitrogen. For example, suitable leaving groups include iodide, bromide, chloride, tosylate, mesylate or triflate. Functionalization of the thioamide group can occur on the thioamide nitrogen or the thioamide sulfur, provided of course that the thioamide nitrogen bears at least one hydrogen. The product also can be a mixture of the compound functionalized on the nitrogen and the one functionalized on the sulfur. In compounds also having a primary or secondary amino group, functionalization also may occur solely or partially on the amino group.

[0020] Preferably, R12 and R13 independently are hydrogen or methyl. Preferably, the compound of formula CHR12═CR13COOR14 is an alkyl or aralkyl acrylate having R12=R13═H and R14=alkyl or aralkyl; or a methacrylate ester having R12═H and R13═CH3; or a crotonate ester having R13═H and R12═CH3. Preferably, R12 is hydrogen. Preferably, R14 is alkyl or aralkyl, most preferably C4-C22 alkyl. Preferably, R15 is aryl, aralkyl or alkyl; most preferably C8-C22 alkyl. Preferably, R9 is C12-C22 alkyl. In one embodiment, R9 is derived from an unsubstituted C16-C22 alkyl amine, R9NH2, preferably one which is an oil-soluble amine. In one embodiment, the alkyl amine is a tertiary alkyl primary amine, i.e., a primary amine in which the alkyl group is attached to the amino group through a tertiary carbon. Examples of commercially available tertiary alkyl primary amines are the Primene™ amines available from Rohm and Haas Company, Philadelphia, Pa. Preferably, R10 and R11 independently are alkyl or hydrogen. In a preferred embodiment of the invention, R9N═CR10R11 is a formaldehyde imine, R9N═CH2. Preferably, R16 is C4-C22 alkyl, C4-C22 alkenyl or aralkyl; more preferably C6-C22 alkyl or C6-C22 alkenyl; and most preferably C8-C22 alkyl.

[0021] As an example, the reaction of the compound of formula (I) in which X is CR7R8, R3 is hydrogen, and none of R1, R2, R4, R5, R7 and R8 contains a primary or secondary amine nitrogen, with an imine and an acrylate is illustrated below in Scheme 3. 7

[0022] The compound resulting from functionalization of the thioamide group, or an NR6 group, with R6═H, in the compound of formula (I) in which X is CR7R8, O, S or NR6, wherein R6 is B3, alkyl, alkenyl, aryl or aralkyl; R3 is hydrogen; and none of R1, R2, R4, R5, R6, R7 and R8 contains a primary or secondary amine nitrogen, can be represented by formula (IV). 8

[0023] wherein bonds b and c are single or double bonds, provided that one of b and c is a single bond and the other is a double bond; at least one of B1, B2 and B3 is —CR12H—CR13H—COOR14, —CR10R11NHR9, —C(O)NHR15, —C(S)NHR15 or R16; when one of B1 and B2 is —CR12H—CR13H—COOR14, —CR10R11NHR9, —C(O)NHR15, —C(S)NHR15 or R16, then the other is absent. When B1 is present, bond “c” is a double bond; and when B2 is present, bond “b” is a double bond. Preferably, at least one of B1, B2 and B3 is —CR12H—CR13H—COOR14, —CR10R11NHR9, —C(O)NHR15 or —C(S)NHR15. Analogous structures exist for the compounds resulting from functionalization of compounds having a primary or secondary nitrogen atom as part of an “R” substituent, in which functionalization may occur on the primary or secondary nitrogen atom, as well as on the NR6 group if R6═H, or the thioamide nitrogen or sulfur.

[0024] Preferably, the compound(s) of formula (I) is present in a lubricating oil in a total amount of at least 0.2%, more preferably at least 0.3%, and most preferably at least 0.4%. Preferably, the compound(s) of formula (I) is present in a lubricating oil in a total amount no greater than 10%, more preferably no greater than 5%, and most preferably no greater than 2%. Preferably, the compounds are soluble at the aforementioned levels.

[0025] Optionally, other additives typically used in lubricating oils are present in the composition. Such additives include, but are not limited to, other anti-wear additives, anti-corrosion additives, dispersants, detergents, antioxidants, antifoamants, friction modifiers, seal swell agents, demulsifiers, viscosity index improvers and pour point depressants. Other anti-wear additives that can be used in combination with the compound of formula (I) include the commercial products known as ZDDP, which are zinc dialkyldithiophosphates. In addition to improving the anti-wear characteristics of lubricating oils, the compound of formula (I) typically also improves anti-corrosion characteristics and functions as an anti-oxidant.

Claims

1. A composition comprising:

(a) from 0.1% to 20% of at least one bicyclic thioamide of formula I:

9

wherein X is O, S, NR6 or CR7R8; R1, R2, R4, R5, R7 and R8 independently are hydrogen, alkyl, alkenyl, aryl or aralkyl; R3 and R6 independently are hydrogen, alkyl, alkenyl, aryl, aralkyl, alkanoyl or aroyl; and bond “a” is a single or double bond; and

(b) a lubricating oil.

2. The composition of claim 1 in which at least one of R1, R2, R3, R4, R5, R6, R7 and R8 is aryl, aralkyl, C4-C22 alkyl or C4-C22 alkenyl.

3. The composition of claim 2 in which bond “a” is a double bond.

4. The composition of claim 3 in which R3 is C6-C22 alkyl, C6-C22 alkenyl, aryl or aralkyl.

5. The composition of claim 4 in which X is NR6.

6. The composition of claim 2 in which bond “a” is a single bond.

7. The composition of claim 6 in which X is NR6.

8. A composition comprising:

(a) a reaction product of a compound of formula (I) with an imine; an unsaturated carboxylic acid or ester; an isocyanate or isothiocyanate; or an alkyl, alkenyl or aralkyl group bearing a leaving group; and

(b) a lubricating oil.

9. A compound of formula (IV)

10

wherein X is O, S, NR6 or CR7R8; R1, R2, R4, R5, R7 and R8 independently are hydrogen, alkyl, alkenyl, aryl or aralkyl; R6 is B3, hydrogen, alkyl, alkenyl, aryl, aralkyl, alkanoyl or aroyl; bond “a” is a single or a double bond; bonds “b” and “c” are single or double bonds, provided that one of b and c is a single bond and the other is a double bond;

B1, B2 and B3 independently are —CR12H—CR13H—COOR14, —CR10R11NHR9, —C(O)NHR15, —C(S)NHR15 or R16; provided that at least one of B1, B2 and B3 is —CR12H—CR13H—COOR14, —CR10R11NHR9, —C(O)NHR15, —C(S)NHR15 or R16; and provided that when one of B1 and B2 is —CR12H-CR13H—COOR14, —CR10R11NHR9, —C(O)NHR15, —C(S)NHR15 or R16, then the other of B1 and B2 is absent;

R10, R11 and R14 independently are hydrogen, alkyl, alkenyl, aryl or aralkyl; R16 is alkyl, alkenyl or aralkyl; R12 and R13 independently are hydrogen or C1-C4 alkyl; R9 and R15 independently are alkyl, alkenyl, aryl or aralkyl.

10. The compound of claim 9 in which at least one of B1, B2 and B3 is —CR12H—CR13H—COOR14, —CR10R11NHR9, —C(O)NHR15 or —C(S)NHR15.