GB2123429A - Phosphorus-containing polymeric lubricant additives - Google Patents

Abstract

A lubricating oil additive obtainable by reacting a dialkyl phosphonate of the formula (R<1>O)2PH = O with an organic compound having available = NH groups in its molecular structure and molecular weight greater than 500, for example a hydrocarbyl substituted succinimide dispersant, in the presence or absence of either an aldehyde or a ketone of the formula (R<2>)(R<3>)C = O, in which formulae the groups R<1> are independently alkyl groups having from 1 to 30 carbon atoms and R<2> and R<3> are independently either hydrogen or alkyl groups having from 1 to 5 carbon atoms. In the absence of an aldehyde or ketone the product is a salt, whereas in the presence of an aldehyde or ketone the product is an N-substituted aminoalkylphosphonate. The product may be reacted, simultaneously or subsequently, with elemental sulphur.

Description

SPECIFICATION Lubricating oil additives derived from dialkyl phosphonates The present invention relates to lubricating oil additives obtainable by reacting a dialkyl phosphonate with a high molecular weight organic compound having available = NH groups in its molecular structure and optionally also either an aldehyde or a ketone.

It has for some time been the practice to add to lubricating oils a dispersant in order to prevent the deposition of sludge caused by the presence in the oil of dirt, soot, water and decomposition products resulting from breakdown of the oil. Dispersants are additives which are capable of dispersing the sludge formed in engines, thereby maintaining the sludge in fine suspension in the lubricating oil, in which condition it does not deposit on engine parts such as oil screens, valve train components and oil control rings where it could cause problems with respect to the efficient operation of the engine. A dispersant which has gained wide acceptance is that generally referred to as a succinimide which can be produced by reacting a hydrocarbyl substituted succinic acid or succinic anhydride with a polyamino compound as described for example in GB 922831.It is also known to add phosphorus-containing compounds, such as dialkyl phosphonates and/or trialkyl phosphonates, to lubricating oils as anti-wear and anticorrosion agents. Generally, these additives together with others, such as antioxidants and viscosity index improvers, are sold by additive manufacturers in the form of additive packages, which are blended into base oils by the finished lubricating oil manufacturer. A very important property of an additive is its compatability with other additives both in the additive package and in the finished oil. In this respect problems have been encountered in mixing dialkyl phosphonates with other components of the additive package. Whilst the compatability problem can be substantially reduced by careful selection of the components, this approach is not entirely satisfactory because it severely curtails operational flexibility.

It is known from, for example, US Patent No 4083897 that dialkyl phosphonates of the formula (R10)2 - PH = O will react with an amine having the formula R4#N(H)n(R5)2#n and an aldehyde or ketone having the formula (R2)(R3)C = O to form an N-alkylated aminoalkylphosphonate of formula: [ (R1 0)2 P(0)C(R2)(R3) ] n N(R4)(R5)2 n wherein R', R4 and R5 are straight or branched lower alkyl having two to five carbon atoms; R2 and R3 are selected from the group consisting of straight or branched lower alkyl having one to five carbon atoms and hydrogen and n is the integer one or two.

We have now found that a dialkyl phosphonate will react with an organic compound having available = NH groups in its molecular structure and a molecular weight greater than 500 in the absence of an aldehyde or ketone to form a salt, and in the presence of an aldehyde or ketone to form an N-substituted aminoalkylphosphonate, both of which are more compatible with other components in the additive package than is the dialkyl phosphonate alone. Moreover, the N-substituted aminoalkylphosphonate derived from a succinimide can exhibit multifunctional behaviour in that it can act as both a dispersant and an anti-wear additive in lubricating oil compositions.

Accordingly, the present invention provides a lubricating oil additive obtainable by reacting a dialkyl phosphonate of formula: (R10)2-PH = 0 (I) with an organic compound having available = NH groups in its molecular structure and a molecular weight greater than 500 in the presence of absence of either an aldehyde or a ketone having the formula: (R2)(R3) = 0 (II) in which formulae (I) and (II), the groups R' which may be the same or different are straight or branched alkyl groups having from 1 to 30 carbon atoms and R2 and R3 are independently either hydrogen or straight or branched alkyl groups having from 1 to 5 carbon atoms.

With regard to the phosphonate of formula (I), the groups R' may suitably be straight or branched alkyl groups having from 1 to 20 carbon atoms. Suitable compounds of formula (I) are diethyl phosphonate, diisopropyl phosphonate and dibutyl phosphonate. An advantage of using the lower alkyl phosphonates is that by virtue of their lower boiling points the use of excessive stripping temperatures can be avoided.

The organic compound having available = NH groups in its molecular structure and a molecular weight greater than 500 may be chosen from a wide range of materials. It may suitably be selected from materials which are viscosity index improvers, eg amino functionalised polyolefins, or dispersants, eg succinimides, or materials which incorporate both viscosity index improver and dispersancy properties.A preferred organic compound is the hydrocarbyl substituted succinimide in which the hydrocarbyl substituent contains from 30 to 200 carbon atoms obtained by reacting a substituted succinic acid having the structural formula: R4.CH(CH2COOH).COOH (111) or a substituted succinic anhydride having the structural formula:

in which structural formulae (III) and (IV) the substituent R4 is a large substantially aliphatic hydrocarbon radical having from 30 to 200 carbon atoms, with at least one-half an equivalent amount of an amine of formula:: H2N [ CH2CH(R5)NHJ#H (V) in which formula (V) the substituent R5 is a C1 to C6 alkyl radical or hydrogen and x is an integer in the range 1 to 5, at a sufficiently elevated temperature to effect formation of the succinimide and to remove the water formed in the reaction. For convenience the product is generally referred to in the art as a succinimide, which term has been adopted in this specification.

Preferably the substituent R4 in the structural formulae (III) and (IV) is a large substantially aliphatic hydrocarbon radical having at least 50 carbon atoms. The group R4 may be either an alkyl or an alkenyl radical. Suitably the group R4 may be derived from polyolefins such as polyethylene, polypropylene or polybutylene although they may be derived from any substantially aliphatic hydrocarbon. Preferably the group R4 is a polyisobutylene group.

The substituted succinic acids and anhydrides of formulae (III) and (IV) are readily available from the reaction of maleic anhydride with a high molecular weight olefin or a chlorinated high molecular weight olefin. The product from such a reaction is the corresponding alkenyl succinic anhydride. The reaction may be effected by heating the reactants at a temperature in the range of from 150 to 200 C.

Amines of the formula (V) are generally known as polyalkyl polyamines, though when B5 = H they are generally referred to as ethylene amines. The group R5 may be a C1 to C6 alkyl group but is preferably hydrogen. Suitable amines of formula (V) are ethylene diamine, diethylene, triamine, triethylene tetramine, tetraethylene pentamine and pentaeethylene hexamine. Such compounds are well-known in the art and are generally prepared by reacting ethylene dichloride with ammonia. In addition to the pure compounds mixtures of such compounds may also be used.

Whilst at least one half of a chemical equivalent amount of the compound of formula (V) per equivalent of substituted succinic acid or anhydride must be used in the production of the substituted succinimide, up to 2.0 chemical equivalents may be used. The chemical equivalency of the amine reactant is based upon the nitrogen content thereof. Thus triethylene tetramine, for example, has four equivalents per mole.

The substituted succinic acid of structural formula (III) or the substituted succinic anhydride of structural formula (IV) may suitably be reacted with the amine of formula (V) at a temperature in the range of from 80 to about 200 C, preferably from 100 to 1 60 C. A suitable method of carrying out the reaction is to add some hydrocarbon solvent eg toluene, to the reaction mixture and remove the water formed by azeotropic distillation. Further details of the process for producing a hydrocarbyl substituted succinimide may be found in the aforesaid British Patent No 922831.

A suitable substituted succinimide useful in the performance of the invention is the bissuccinimide obtained by reacting a substituted succinic anhydride wherein the substituent is derived from a polyisobutene of molecular weight about 1000 with half a mole of triethylene tetramine. Such a substituted succinimide has, theoretically, two amino (= NH) groups available for bonding. Another suitable succinimide is the mono-succinimide derived from triethylene tetramine in the aforesaid reaction. The mono-succinimide has, theoretically, four = N-H groups available for bonding.

As mentioned hereinbefore the product in the absence of an aldehyde or a ketone is a salt.

Examples of suitable compounds having the formula (lì) are formaldehyde, acetaldehyde, nrnoionaldehvde, acetone and methyl ethyl ketone. Preferably the compound of formula (li) is formaldehyde. Formaldehyde may be employed in its monomeric form or in a polymeric form, eg paraformaldehyde. Paraformaldehyde is preferably added in the form of a solution in a suitable alcohol, for example methanol or ethanol. Furthermore, the aldehyde or ketone may be added as an aqueous solution or in a substantially anhydrous state. Thus formaldehyde may be added as formalin. The amount of aldehyde or ketone employed may suitably be in the range from zero up to twice the molar amount of the dialkyl phosphonate employed.

The reaction in the presence of an aldehyde or a ketone may be carried out in a variety of different ways. The water formed as a by-product of the reaction may be removed during the course of the reaction, as described in US Patent Nos 3268450 and 3555124. Alternatively, the water may be removed at the completion of the reaction, as described in US Patents Nos 2635112; 2,847,442; 2870190; 3076010; 3257479; 3821335 and 3855363. In a further alternative, nonaqueous aldehyde or ketone may be employed, as described in US Patents Nos 3134742; 3257479; 3352948; 3385914; 3457333; 3498969; 3505431 and 3551422.It is preferred however to use the process described in the aforesaid US Patent No 4083897 wherein in a first step a mixture of the appropriate dialkyl phosphonate and the hydrocarbyl substituted succinimide is prepared and in a second step aqueous formaldehyde or ketone is added to the reaction with the reaction temperature kept below about 70 C. The water is removed at the conclusion of the reaction. For further details of this process reference may be made to USP 4083897 which is hereby incorporated into the specification. The process of USP 4083897 shares with those patents covering the use of nonaqueous aldehyde or ketone the advantage that products having low acid numbers can be obtained, thereby eliminating the need for a final and expensive distillation stage.The desirability of using a product having a low acid number in lubricant applications will be readily apparent to those skilled in the art. As hereinbefore mentioned the product in the presence of an aldehyde or a ketone is an Nsubstituted aminoalkylphosphonate.

In a further embodiment of the invention sulphur may be incorporated into the lubricant additives so-obtained by exchange with oxygen atoms of the additive or reactant phosphonate.

The exchange may be accomplished either by reacting the additives with elemental sulphur or by the addition of elemental sulphur to the initial reaction mixture.

In another aspect, the invention provides a concentrate composition for use in the production of finished lubricating oils which composition comprises a lubricating oil additive obtained in the manner as hereinbefore described and a lubricating oil.

The lubricating oil additive may suitably be present in the concentrate composition in an amount sufficient to provide up to 15% by weight, preferably from 0. 1 to 10%, by weight in the finished oil composition.

The concentrate composition may additionally contain other additives, such as detergents, antioxidants, anti-wear agents, anti-corrosion agents and viscosity index improvers.

The lubricating oil may be a petroleum-derived lubricating oil or a synthetic lubricating oil, eg a high molecular weight ester. Of the hydrocarbon-derived lubricating oils, solvent neutral oils are suitable.

In yet another aspect the invention provides a finished lubricating oil composition which composition comprises a minor proportion of the concentrate composition as hereinbefore described and a major proportion of a lubricating base oil.

The invention will now be described in further detail by reference to the following Examples.

Example 1 A commercially available hydrocarbyl substituted bis-succinimide (190g) derived from triethy lene tetramine and a hydrocarbyl substituted succinic acid in which the hydrocarbyl substituent is a polyisobutene of molecular weight about 1000 and di(C12-C14) phosphonate (41.99) were heated for approximately 2 hours at 60 C. To this mixture formaldehyde (a 37% aqueous solution) (7.6g) was added dropwise and the resultant mixture reacted for 1 > hours at 60 C.

The product was then vacuum stripped for 2 hours at 20 mm Hg pressure and at 70do. The product was analysed and its viscosity at 100 C was measured. The results were as follows: P 1.28% b.w.

N 1 17% bow Basic N 0.40% b.w.

V100 1293 cSt Example 2 The reactant composition was the same as that used in Example 1 except that only 3.8g of formaldehyde was used and diethyl phosphonate (6.9g) was used in place of the di(C,2-C,4) phosphonate. The experimental procedure was the same as that used in Example 1 except that during the last hour of vacuum strip the temperature was raised to 100 C to remove any unreacted phosphonate (boiling point approximately 72 C at 12 mm Hg pressure).

The results of the product analysis and viscosity measurement were as follows: P 0.54% b.w.

N 1 14% bow Basic N 0.46% b.w.

V100 179.6 cSt Example 3 The reactant composition was the same as that used in Example 2 except that the bissuccinimide was replaced by a mono-succinimide (1 000g) derived from the same reactants, formaldehyde was increased to 81.5 g and diethyl phosphonate was increased to 1389. The experimental procedure was the same as that described in Example 2.

The results of the product analysis and viscosity measurements were as follows: P 2.42% b.w.

N 1.94% b.w.

Basic N 0.50% b.w.

V100 460.1 cSt Comparison Test 1 A 5% solution of the bis-succinimide in BP 150 SN base oil was subjected to a Panel Coker test (Panel temperature 300 C). The results are given in Table 1.

Comparison Test 2 A 5% solution of the mono-succinimide in BP 150 SN base oil was subjected to a Panel Coker test (Panel temperature 300 C). The results are given in Table 1.

Example 4 A 5% solution of the product of Example 2 in BP 150 SN base oil was subjected to a Panel Coker test (Panel temperature 300 C). The results are given in Table 1.

Example 5 A 5% solution of the product of Example 3 in BP 150 SN base oil was subjected to a Panel Coker test (Panel temperature 300 C). The results are given in Table 1.

Table 1 Panel Coker Performance Example Additive Panel Gain (mg) Comp Test 1 bis-succinimide 9.0 Comp Test 2 mono-succinimide 9.0 Example 4 product Example 2 4.8 Example 5 product Example 3 11.4 Comparison Tests 3 to 5 and Examples 6 to 8 Blotter Spot Tests Method 5 drops of test oil were placed on a filter paper. 1 drop of used oil containing 2% insolubles was then added, followed by 10 drops of oil. The chromatograph was developed for 5 hours, following which the percentage dispersion was determined by calculating the ratio between the distance travelled by the deposits to the distance travelled by the solvent front. High values indicate materials are satisfactory as dispersants. The test was carried out on the bas oil itself (LP 501) (Comparison Test 3), a 2.5% by weight solution of the bis-succinimide in LP 501 (Comparison Test 4), a 2.5% by weight solution of the mono-succinimide in LP 501 (Comparison Test 5), a 2.5% by weight solution of the product of Example 3 in LP 501 (Example 6), a 2.5% by weight solution of the product of Example 2 in LP 501 (Example 7) and a 3.0% by weight solution of the product of Example 1 in LP 501 (Example 8). The results are given in Table 2.

Table 2 Example % Additive % Dispersion Comp Test 3* base oil 52.0 Comp Test 4 2.5% bis-succinimide 49.4 83.6 Comp Test 5 2.5% mono-succinimide 40.2 79.7 Example 6 2.5% product Example 3 53.1 82.6 Example 7 2.5% product Example 2 44.5 79.4 Example 8* 3.0% product Example 1 84.3 * gave only one deposit front indicating all the carbonaceous deposit had been transported.

With the others, two deposit fronts were obtained, the lowest value result being the darkest, indicating that the oii and the dispersant acted separately.

Comparison Tests 6 to 11; Examples 9 to 11 Shell 4 Ball Evaluation The materials listed in Table 3 were evaluated in the Shell 4 Ball test.

Table 3 Initial Weld Active Seizure Point Example (wt% in 100SN base oil) (kg) (kg) Comp Test 6 5% mono-succinimide 70 160 Comp Test 7 5% bis-succinimide 70 170 Example 9 5% product Example 3 130 250 Comp Test 8 3.33% mono-succinimide + 20mM ZDT* 120 210 Example 10 5% product Example 2 100 180 Comp Test 9 4.63% bis-succinimide + 4.4mM ZDP 70 190 Example 11 5% product Example 1 126 230 Comp Test 10 4.15 bis-succinimide + 1 OmM ZDT* 80 210 Comp Test 11 4.1% bis-succinimide + 1 ohm X 80 180 * ZDT = zinc dialkyl thiophosphate prepared from C7 to C9 alcohol.

Concentration of ZDT equates to level of P contributed by the experimental additives.

X X = di(C12-C,4) phosphonate.

Concentration equates to the level of P contributed by product of Example 1.

With reference to the above results, by comparison with the conventional succinimide dispersants the product of Example 2 gave better results in the Panel Coker Test, comparable results in the Blotter Spot Test and better results in the Shell 4 Ball Evaluation; the product of Example 3 gave slightly inferior results in the Panel Coker Test, comparable or better results in the Blotter Spot Test and better results in the Shell 4 Ball Evaluation and, although not tested in the Panel Coker Test, the product of Example 1 gave markedly improved results in the other Tests.

Example 12 The monosuccinimide as used in Example 3 (4009) was heated to 55 to 60 C. Diethyl phosphonate (27.69) was dripped in and the mixture reacted for 1 < hours at 55 to 60 C. The mixture was then heated for 1 hour at 60 to 65 C. The product was vacuum stripped for 1 hour at 70 C and then for 1 hour at 120 C. Finally, the product was filtered.

The results of the product analysis and viscosity measurements were as follows: P 0.41% b.w.

N 2.00% b.w.

Basic N 0.92% b.w.

V100 381.2 cSt Example 13 270g of a 1:1:1 charge mole ratio of a monosuccinimide/formaldehyde solution/diethyl phosphonate complex having the chemical analysis (% by weight) P(0.66), N(approx. 2.29), S(0.26), a viscosity as measured at 100 C of 425 cSt and a copper strip test rating of IB was heated to 120 C. 5.4g sulphur and 10.89 ethylene glycol were then added and the reaction continued for 1.5 hours at 120-130 C. Ethylene glycol was then removed by vacuum stripping to 200 C/20 mmHg pressure for 20 minutes. The resultant material was filtered to yield a product with the following composition: P0.66% b.w.

N2.29% b.w.

S0.90% b.w.

The product had a viscosity as measured at 100 C of 474 cSt and a copper strip test rating of IB.

Claims (10)

1. A lubricating oil additive obtainable by reacting a dialkyl phosphonate of the formula: (RlO)2-PH = 0 (I) with an organic compound having available = NH groups in its molecular structure and a molecular weight greater than 500 in the presence or absence of either an aldehyde or a ketone having the formula: (R2)(R3)C = 0 (II) in which formulae (I) and (II), the groups R' which may be the same or different are straight or branched alkyl groups having from 1 to 30 carbon atoms and R2 and R3 are independently either hydrogen or straight or branched alkyl groups having from 1 to 5 carbon atoms.

2. A lubricating oil additive according to claim 1 wherein the dialkyl phosphonate of formula (I) is either diethyl phosphonate diisopropyl phosphonate or dibutyl phosphonate.

3. A lubricating oil additive according to either claim 1 or claim 2 wherein the organic compound having available = NH groups in its molecular structure and a molecular weight greater than 500 is the hydrocarbyl substituted succinimide in which the hydrocarbyl substituent contains from 30 to 200 carbon atoms obtained by reacting a substituted succinic acid having the structural formula: R4.CH(CH2COOH).CO0H (Ill) or a substituted succinic anhydride having the structural formula:

in which structural formulae (III) and (IV) the substituent R4 is a large substantially aliphatic hydrocarbon radical having from 30 to 200 carbon atoms, with at least one-half an equivalent amount of an amine of formula:: H2N [ CH2CH(R9)NHJxH (V) in which formula (V) the substituent R5 is a Ct to C9 alkyl radical or hydrogen and x is an integer in the range from 1 to 5, at a sufficiently elevated temperature to effect formation of the succinimide and to remove the water formed in the reaction.

4. A lubricating oil additive according to claim 3 wherein the substituent R4 is a large substantially aliphatic hydrocarbon radical having at least 50 carbon atoms.

5. A lubricating oil additive according to claim 4 wherein the substituent R4 is a polyisobutylene group.

6. A lubricatir#g oil additive according to any one of the previous claims wherein the dialkyl phosphonate is reacted with the organic compound having available = NH groups in its molecular structure and a molecular weight greater than 500 in the presence of an aldehyde of formula (II), which aldehyde is formaldehyde.

7. A lubricating oil additive according to any one of the previous claims wherein the dialkyl phosphonate is reacted with the organic compound in the presence of elemental sulphur.

8. A lubricating oil additive obtained by reacting a dialkyl phosphonate of formula (I) with an organic compound having available = NH groups in its molecular structure and a molecular weight greater than 500 in the presence or absence of an aldehyde or ketone of formula (II), and thereafter reacting the product with elemental sulphur.

9. A concentrate composition for use in the production of finished lubricating oils which composition comprises the lubricating oil additive as claimed in claims 1 to 8 and a lubricating oil.

10. A concentrate composition according to claim 9 wherein the lubricating oil additive is present in an amount sufficient to provide up to 15% by weight in the finished oil composition.