WO2003054120A1

WO2003054120A1 - Lubricant compositions

Info

Publication number: WO2003054120A1
Application number: PCT/GB2002/005779
Authority: WO
Inventors: Elizabeth Dixon
Original assignee: Cognis Performance Chemicals Uk Limited
Priority date: 2001-12-20
Filing date: 2002-12-19
Publication date: 2003-07-03
Also published as: GB0130490D0; AU2002352451A1

Abstract

Lubricant compositions comprise a block copolymer having a first block comprising polymerised units of an alkylene oxide and a second block comprising polymerised units of an alkylene oxide and a lactone; or a copolymer comprising polymerised units of one or more alkylene oxides, one or more lactones, and a monofunctional initiator; and a corrosion inhibitor. Also provided is the use of a copolymer comprising polymerised units of one or more alkylene oxides, one or more lactones, and a monofunctional initiator, as a lubricant.

Description

LUBRICANT COMPOSITIONS

This invention relates to lubricant compositions comprising alkylene oxide- lactone copolymers.

Co- and homo-polymers of alkylene oxide are widely used as non-ionic surfactants, foam control agents, mineral wetting agents, emulsifiers, de-emulsifiers, dispersants, and synthetic lubricants. In particular, polyoxyalkylene copolymers made from propylene oxide, 1,2-butylene oxide and ethylene oxide represent a major class of such materials.

The principle advantages of polyglycol copolymers as lubricants are their very high hydrodynamic lubricity and their very low temperature dependence of viscosity (i.e. high viscosity index). Polyalkylene glycols have very low pourpoints and exhibit good thermal, chemical and oxidative stability.

Alkylene oxide-lactone block copolymers are also known to be useful for similar applications. US 5525702, for example, describes a copolymer having antifoam and lubricant utility, which comprises a first block comprising polymerised units of one or more alkylene oxides and one or more lactones, and a second block comprising polymerised units of one or more alkylene oxides. Such compounds are prepared by polymerising the lactone and alkylene oxide monomers of the first block in the presence of an organic initiator, and then capping the resulting polymer with the alkylene oxide monomer of the second block. The presence of a lactone in the first block is said to introduce ester functionality into the copolymer, which in turn, enhances its overall biodegradability. US 5525702 further describes copolymers which are uncapped, i.e. which do not contain a second block of polymerised alkylene oxide units. These random copolymers comprise polymerised units of one or more alkylene oxides, one or more lactones, and a polyfunctional initiator. The above copolymers are said primarily to have utility in antifoam applications, although utility as lubricants is also mentioned. We have found that introduction of a lactone into the second block of an alkylene oxide copolymer, or copolymers comprised of polymerised units of one or more alkylene oxides, one or more lactones, and a monofunctional initiator, have enhanced biodegradability, without compromising the lubricating properties of such a structure. Accordingly the present invention provides the use of a copolymer comprising polymerised units of one or more alkylene oxides, one or more lactones, and a monofunctional initiator, as a lubricant. This copolymer is obtainable by polymerising an alkylene oxide and a lactone in the presence of an organic initiator to form the copolymer. Regarding this first aspect of the invention, the copolymer may have a molecular weight of 300 to 10000, preferably 500 to 6000 and most preferably 1000 to 4000. The number of monomer units may range from 1 to 300, preferably 5 to 100. The mole ratio of alkylene oxide to lactone units may range up to 99:1, but is preferably 10:1 or less. The invention also provides in a second aspect a lubricant composition comprising a) a block copolymer having a first block comprising polymerised umts of an alkylene oxide and a second block comprising polymerised units of an alkylene oxide and a lactone; or a copolymer comprising polymerised units of one or more alkylene oxides, one or more lactones, and a monofunctional initiator; and (b) a corrosion inhibitor. The invention further provides a method of providing lubrication to a system, which comprises incorporating into the system in contact with a part or parts requiring lubrication, a block copolymer having a first block comprising polymerised units of an alkylene oxide and a second block comprising polymerised units of an alkylene oxide and a lactone; or a copolymer comprising polymerised units of one or more alkylene oxides, one or more lactones, and a monofunctional initiator. The method may be used for the lubrication of mechanical elements in a wide range of applications for example those listed below.

The copolymer having a first block comprising polymerised units of an alkylene oxide and a second block comprising polymerised units of an alkylene oxide and a lactone is obtainable by polymerising an alkylene oxide in the presence of an organic initiator to form said first block, and reacting the first block with a mixture of an alkylene oxide and a lactone. Typically, one end of the first block is bonded directly to the organic initiator, whilst the other end of the first block is bonded directly to the second block of the copolymer. The recurrence of the alkylene oxide and lactone groups within the second block is typically random, but may contain some degree of block character. For example, the second block itself may comprise alternate blocks of alkylene oxide and lactone rather than randomly distributed units of each. Preferably the total number of blocks of alkylene oxide and lactone in the copolymer is between 5 and 9. Preferably the copolymer has at least 3 umts of alkylene oxide in each block thereof, or 2 units of lactone in each block thereof. In the process associated with this embodiment, instead of being reacted with a mixture of alkylene oxide and lactone, the first block is reacted alternately with either alkylene oxide or lactone. The number of such reactions is preferably between 4 and 8 (so as to give between 5 and 9 blocks in total).

The copolymer may have a molecular weight of 200 to 20,000, preferably 400 to

15000, most preferably 500 to 12000. The molecular weight of the first block is typically at least 150, for example 200 to 2000, preferably 200 to 1000 and most preferably 250 to 600; whilst the molecular weight of the second block is typically more than that of the first, preferably greater than 500.

The number of monomer units in each of the first and second blocks may independently range from 1 to 500, preferably 5 to 50. In the second block, the mole ratio of alkylene oxide to lactone units may range up to 99 : 1 , but is preferably 10: 1 or less.

For both types of copolymer used in this invention, the alkylene oxide components of the copolymer include those of formula (I)

Formula (I)

in which each R is independently hydrogen, -Cβ alkyl or d-Cό haloalkyl.

Alternatively, the two R substituents may, together with both vicinal epoxy carbons, form a saturated or monoethylenically unsaturated cycloaliphatic hydrocarbon ring, of preferably five or six carbon atoms. The preferred alkylene oxide monomers contain 2 to 12 carbon atoms. Examples include ethylene oxide, propylene oxide, butylene oxides, 1,2-epoxydodecane, cyclopentene oxide, cyclohexene oxide and styrene oxide. Of these, butylene oxides (particularly 1,2-butylene oxide), propylene oxide and ethylene oxide are most preferred.

For a copolymer having a first block comprising polymerised units of an alkylene oxide and a second block comprising polymerised units of an alkylene oxide and a lactone, the alkylene oxide of the first block may be the same as the alkylene oxide of the second block. Preferably, however, the alkylene oxides of the first and second blocks are different. In a preferred embodiment, for example, ethylene oxide is employed to form the first block of the copolymer, whilst propylene oxide or 1,2- butylene oxide is employed to form the second block of the copolymer. The alkylene oxide portions of both first and second blocks of the copolymers of the present invention may optionally comprise mixtures of alkylene oxide monomers, e.g. a mixture of ethylene and propylene oxides.

The lactone used may be any lactone or combination of lactones having at least four carbon atoms in the ring, and these lactones include those of formula (II)

Formula (II)

in which when n is at least 1 and each R¹ is independently hydrogen, Cι-C₄ alkyl, Cι-C₆ cycloalkyl, Cι-C alkoxy or single ring aromatic hydrocarbon; with the proviso that when n is 2, at least four R¹ in total are hydrogen.

The lactones preferred as starting materials include unsubstitued ε-caprolactones, ε- caprolactones substituted on the carbon atoms in the ring by one, two or three lower (e.g. one to four carbon atoms) alkyl radicals, and unsubstituted δ-valerolactones and γ- butyrolactones. The preparation of unsubstituted lactones is well known. The substituted ε-caprolactones, and mixtures of such lactones, can readily be prepared by reacting a corresponding substituted cyclohexanone with an oxidizing agent such as peracetic acid. The cyclohexanones may be obtained from substituted phenols or by other convenient synthetic routes. Other lactones that are suitable as starting materials include alkoxy ε-caprolactones such as methoxy and ethoxy ε- caprolactone, cycloalkyl, aryl and aralkyl ε-caprolactones such as cyclohexyl, phenyl and benzyl ε-caprolactone, and lactones such as ζ-enantholactone and η-caprylactone which have more than six carbon atoms in the ring.

The ε- caprolactones are the preferred lactones for use in this invention. These include those of formula (III)

Formula (Tfl)

in which each R² is independently either hydrogen or a Cι-C alkyl or d-C₄ alkoxy radical, with the proviso that no more than three R² substituents are groups other than hydrogen. Unsubstituted ε-caprolactone is the preferred ε-caprolactone.

The copolymer having a first block comprising polymerised units of an alkylene oxide and a second block comprising polymerised units of an alkylene oxide and a lactone is prepared by first polymerizing an alkylene oxide or mixture of alkylene oxides using an organic initiator. The initiator may be mono or poly-functional. Examples of monofunctional initiators include alcohols, amines, mercaptans, phenols, amino alcohols and mercapto alcohols. Hydroxyl and amino terminated initiators are preferred.

Suitable monohydroxyl initiators include those represented by the formula (IN)

R³(OR⁴)_a OH (IV) in which R³ is hydrocarbyl such as alkyl, cycloalkyl, aryl, aralkyl, alkaryl, etc., preferably containing up to 18 carbon atoms; R⁴ is an alkylene radical preferably containing from two to four carbon atoms; and a is an integer having a value of 0 to 18, preferably a value of 0 to 2. Illustrative monohydroxyl initiators include the alkanols, e.g. methanol, ethanol, isopropanol, n-butanol, 2-ethylhexanol, dodecanol, tridecanol, and tetradecanol; the monoalkyl ethers of glycols and polyglycols, e.g., 2-ethoxyethanol, 2-propoxyethanol, 2-butoxyethanol, the monoethyl ethers of diethylene glycol, of triethylene glycol, of tripropylene glycol; the monopropyl ethers of polyethylene glycol, of polypropylene glycol, of polybutylene glycol; and the alkylene oxide adducts of substituted and unsubstituted phenols, e.g. the ethylene oxide and/or propylene oxide adducts of alkylphenols such as nonylphenol. Mixtures of organic initiators may be employed.

The initiator may alternatively be polyfunctional. Preferred polyfunctional initiators have at least two and possibly up to 20 reactive hydrogens in the form of hydroxyl groups. The polyfunctional initiators include compounds of the formula (V)

R⁵(YH)_b (V) where R⁵ is an aliphatic, aromatic or heterocyclic radical, b is at least 2, and each Y is - O-, -S-, -NH- or NR⁶ where R⁶ is hydrocarbyl. Preferred such initiators are diols, polyols, diamines, hydroxy amines and thiols, such as ethylene/propylene glycol, diethylene/dipropylene glycol, 1,2-dibutylene glycol, glycerine, trimethylol propane, pentaerythritol, ethylenediamine, ethanolamine etc. Such compounds may also be ethoxylated.

A copolymer comprising polymerised units of one or more alkylene oxides, one or more lactones, and a monofunctional initiator may be prepared by a process comprising polymerising a mixture of alkylene oxide(s) and lactone(s) using a monofunctional organic initiator. The copolymer itself may comprise alternate blocks of alkylene oxide and lactone rather than randomly distributed units of each. The advantage of this method of reaction is the lack of requirement for alkylene oxide and lactone premixing, or simultaneous addition equipment. The initiator is preferably a monofunctional initiator as described above.

The polymerisation of alkylene oxide and or alkylene oxide and lactone may be carried out in the presence of a catalyst. Any catalyst that will promote the necessary polymerization reaction may be employed. Representative catalysts include alkali metal and alkaline earth hydroxide, and Lewis acids. Preferred catalysts are the alkali hydroxides, particularly potassium hydroxide (KOH). The catalyst may be used in catalytically significant amounts which is a function of many variables, including the nature and quantities of reactants, temperature, mixing, and the like. Catalyst concentrations of about 0.001 to about 2 weight percent are typical, with a concentration of about 0.01 to about 1 weight percent being preferred. It may be necessary to neutralise the catalyst prior to recovering the polymer product. The copolymers used in the present invention may be prepared at a reaction temperature of 75 to 175°C, preferably 85 to 150°C. These temperature ranges may be suitable for the formation of all sections or blocks of the copolymer. Reaction pressures range from, but are not limited to, 1 to 15 bar, preferably 6 to 10 bar. Preferably, anhydrous conditions are employed. The reaction may be performed on a batch, semicontinuous or continuous basis.

The copolymers used in the present invention have utility as lubricants in many applications. These include:

HF-C type hydraulic fluids (hydraulic fluids containing mainly the compounds of the invention and water) for applications where fire resistance is important such as mining.

Industrial gear and bearing lubricants - used in gear / bearing lubrication where high load and high temperature conditions are commonly encountered.

Compressor lubricants - used in the compression of many different gases including hydrocarbon gases, chemical gases and inert gases.

Quenchants - used in the heat treatment (controlled cooling) of ferrous and non- ferrous metals.

Hydraulic fluids in general (not containing any water) - used in a wide range of general hydraulic fluid applications; biodegradable versions of particular interest in off- road vehicles and eg. tree-cutting equipment.

Textile lubricants - used to lubricate equipment used in the manufacture and processing of textiles.

Components of metalworking fluids - used to provide lubrication and cooling in a wide range of metal cutting processes. Components of greases - can be used as components of superior greases for particularly high and low temperature applications.

Components of rubber lubricants - can be used as lubricants during the manufacture and assembly of rubber components.

Lubricating compositions according to the present invention may contain any suitable form of corrosion inhibitor. Such corrosion inhibitors are well known in the art, and a wide variety of chemical types may provide effective metal corrosion inhibition. Examples of such types may include alkali / alkali metal sulphonates, succinic acid derivatives, imidazoline derivatives and amine phosphates. Typically the corrosion inhibition of yellow metals in polyalkylene glycol based systems is derived from supplementary chemical types such as triazole derivatives. Certain specific types within this broad range of chemistries will show particular synergies with polyalkylene glycol type basefluids and are well known to those skilled in the art of formulating polyalkylene glycol basefluids.

The lubricant compositions of the invention may contain other additives which are well known to those skilled in the art. A typical lubricant composition is as follows (amounts are approximate only): Industrial Gear / Bearing Lubricant

Lubricant basefluid: 90 - 99+ %

White Metal Corrosion Inhibitor: 0.01 - 1%

Yellow metal corrosion inhibitor: 0.01 - 0.05%

Antioxidant(s): 0.1 - 2% Extreme pressure /antiwear additive: 0.1 - 2.0%

Antifoam: 10-100 ppm HF-C type hydraulic fluid

Lubricant basefluid: 10-20%

Water: 30 - 40% Glycol (eg.monefhylene glycol or diethylene glycol): 40-50%

Antifoam: 0.01 - 0.05

White metal corrosion inhibitor: 0.1 - 3%

Yellow metal corrosion inhibitor: 0.01 - 0.1% EXAMPLES Biodegradability Example 1

To a mixture of ethoxylated dodecanol / tetradecanol (available commercially as Softanol 120, a product of the Nippon shokubai company), molecular weight 711, was added potassium hydroxide as catalyst. To this mixture was added a blend of propylene oxide (4 parts molar) and caprolactone (1 part molar) in a pressurised vessel inerted with nitrogen, reaction occurring at a temperature of 120 to 130°C, such that the final product had a theoretical molecular weight of 2990. Biodegradability [OECD 301b Sturm test, 28 days] 85%

Cloud point [ 1 % aqueous] 6 - 8°C

Example 2

To a mixture of ethoxylated dodecanol / tetradecanol (available commercially as Soflanol 120, a product of the Nippon shokubai company), molecular weight 711, was added potassium hydroxide as catalyst. To this mixture was added a blend of propylene oxide (5 parts molar) and caprolactone (1 part molar) in a pressurised vessel inerted with nitrogen, reaction occurring at a temperature of 120 to 130°C, such that the final product had a theoretical molecular weight of 1740. Biodegradability [OECD 301b Sturm test, 28 days] 55%

Cloud point [ 1 % aqueous] 6 - 8°C

Example 3

To a mixture of ethoxylated dodecanol / tetradecanol (available commercially as Soflanol 120, a product of the Nippon shokubai company), molecular weight 683, was added potassium hydroxide as catalyst. To this mixture was added a blend of propylene oxide (2.5 parts molar) and caprolactone (1 part molar) in a pressurised vessel inerted with nitrogen, reaction occurring at a temperature of 120 to 130°C, such that the final product had a theoretical molecular weight of 1176.

Biodegradability [OECD 301b Sturm test, 28 days] 60% Cloud point [ 1 % aqueous] 15°C

Claims

1. The use of a copolymer comprising polymerised units of one or more alkylene oxides, one or more lactones, and a monofunctional initiator, as a lubricant.

2. The use according to claim 1, in which the copolymer has a molecular weight of 300 to 10000, preferably 500 to 6000.

3. The use according to either claim 1 or claim 2 in which the mole ratio of alkylene oxide to lactone units in the copolymer is 10:1 or less.

4. The use according to any one of claims 1 to 3 in which the alkylene oxide components of the copolymer include those of formula (I)

Formula (I)

in which each R is independently hydrogen, d-C₆ alkyl or Cι-C₆ haloalkyl.

5. The use according to any one of claims 1 to 4 in which the alkylene oxide is ethylene oxide, propylene oxide and/or butylene oxide.

6. The use according to any one of claims 1 to 5 in which the lactone is of formula (II)

Formula (II)

in which when n is at least 1 and each R¹ is independently hydrogen, Cι-C₄ alkyl, CrC₆ cycloalkyl, C₁-C₄ alkoxy or single ring aromatic hydrocarbon; with the proviso that when n is 2, at least four R¹ in total are hydrogen.

7. The use according to claims 6 in which the lactone is an unsubstitued ε-caprolactone, ε- caprolactone substituted on the carbon atoms in the ring by one, two or three lower C alkyl radicals, or an unsubstituted δ-valerolactone or γ-butyrolactone.

8. The use according to claim 7 in which the lactone is an ε- caprolactone of formula

(m)

Formula (HI)

in which each R² is independently either hydrogen or a d-C₄ alkyl or Cι-C₄ alkoxy radical, with the proviso that no more than three R substituents are groups other than hydrogen.

9. The use as claimed in any one of claims 1 to 8 in which the initiator for the copolymer is a monofunctional initiator selected from an alcohol, amine, mercaptan, phenol, amino alcohol and mercapto alcohol.

10. The use as claimed in claim 9 in which the initiator is represented by the formula . (IN)

R³(OR⁴)_a OH (IV) in which R is hydrocarbyl such as alkyl, cycloalkyl, aryl, aralkyl, alkaryl, etc., preferably containing up to 18 carbon atoms; R⁴ is an alkylene radical preferably containing from two to four carbon atoms; and a is an integer having a value of 0 to 18, preferably a value of 0 to 2.

11. The use according to any one of claims 1 to 10, which is use in a hydraulic fluid, use as an industrial gear or bearing lubricant, use as a compressor, use to lubricate equipment used in the manufacture and processing of textiles, use to provide lubrication and cooling in a metal cutting process, use as a component of a grease, or use as a lubricant during the manufacture and assembly of rubber components.

12. A lubricant composition comprising a) a block copolymer having a first block comprising polymerised units of an alkylene oxide and a second block comprising polymerised units of an alkylene oxide and a lactone; or a copolymer comprising polymerised units of one or more alkylene oxides, one or more lactones, and a monofunctional initiator; and (b) a corrosion inhibitor.

13. A lubricant composition according to claim 12 in which the copolymer is as defined in any one of claims 1 to 11.

14. A lubricant composition according to claim 12 in which the copolymer is a block copolymer having a first block comprising polymerised units of an alkylene oxide and a second block comprising polymerised units of an alkylene oxide and a lactone.

15. A lubricant composition according to claim 14 in which the copolymer has a molecular weight of 200 to 20,000, preferably 400 to 15000.

16. A lubricant composition according to claim 14 in which the molecular weight of the first block of the copolymer is at least 150, preferably 200 to 2000 and the molecular weight of the second block is more than that of the first.

17. A lubricant composition according to any one of claims 14 to 16 in which the alkylene oxide components of the copolymer include those of formula (I)

R R

I I

HC— CH

Formula (I) O in which each R is independently hydrogen, d-C₆ alkyl or Cι-C₆ haloalkyl.

18. A lubricant composition according to claim 17 in which ethylene oxide is employed to form the first block of the copolymer whilst propylene oxide or 1,2-butylene oxide is employed to form the second block of the copolymer.

19. A lubricant composition according to any one of claims 14 to 18 in which the lactone is of formula (II)

Formula (II)

in which when n is at least 1 and each R¹ is independently hydrogen, d-C₄ alkyl, d-C₆ cycloalkyl, Cι-C₄ alkoxy or single ring aromatic hydrocarbon; with the proviso that when n is 2, at least four R¹ in total are hydrogen.

20. A lubricant composition according to claim 19 in which the lactone is an unsubstitued ε-caprolactone, ε- caprolactone substituted on the carbon atoms in the ring by one, two or three lower C alkyl radicals, or an unsubstituted δ-valerolactone or γ- butyrolactone.

21. A lubricant composition according to claim 20 in which the lactone is an ε- caprolactone of formula (HI)

Formula (HI)

in which each R² is independently either hydrogen or a Cι-C₄ alkyl or C₁-C4 alkoxy radical, with the proviso that no more than three R² substituents are groups other than hydrogen.

22. A composition according to any one of claims 12 to 21 which is adapted for use in a hydraulic fluid, use as an industrial gear or bearing lubricant, use as a compressor, use to lubricate equipment used in the manufacture and processing of textiles, use to provide lubrication and cooling in a metal cutting process, use as a component of a grease, or use as a lubricant during the manufacture and assembly of rubber components.

23. A method of providing lubrication to a system, which comprises incorporating into the system in contact with a part or parts requiring lubrication a copolymer as defined in any one of claims 1 to 11 or a lubricating composition as claimed in any one of claims 12 to 22.