NO130129B - - Google Patents

Description

Lubricant mixture.

For aircraft engines and gas turbine engines, lubricating oils with a high viscosity index are required in order for the lubrication to be satisfactory over a large temperature range, and which are heat-resistant and exhibit a high resistance to oxidation so that they retain their desired properties even after long-term use at high temperatures , as well as having a low pour point so that they work satisfactorily even at low temperatures without any special heating device, and a high flash point so that the risk of ignition at high operating temperatures and loss of lubricant through evaporation is avoided.

Various fluids have been proposed

for use under such conditions, but for the vast majority it applies that there are one or more shortcomings or disadvantages with each one of them. For example

silicone fluids are very stable at high temperatures, but as is known have poor lubrication properties. Esters are often excellent lubricants at low temperatures due to their low pour point and their high viscosity index, but do not have satisfactory thermal stability at temperatures of about 200°C and above. Mineral lubricating oils that exhibit satisfactory viscosity at low temperatures generally have a dangerously low flash point and too low a viscosity at higher temperatures. Additives will not improve the properties of the lubricant to a sufficient extent.

Recent studies in the field of synthetic lubricants have shown that certain types of polyphenyl ethers exhibit excellent thermal stability and resistance to oxidation at very high temperatures. However, most of these compounds are unfortunately solids or liquids of high viscosity at the usual temperatures. Consequently, they can only be used in connection with special heating equipment to prevent them from solidifying in lines and tanks.

It has now been found that certain mixtures

of polyphenyl ethers not only exhibit a high thermal stability and resistance to oxidation, but also have good properties at lower temperatures, so that they can be used as lubricants in engines with high operating temperatures. The mixtures of polyphenyl ethers according to the invention are also stable against ionizing radiation, even at high temperatures, so that they can be used as a fluid in heat exchangers, moderators, as well as as lubricants and hydraulic fluids in radiation-emission equipment.

The mixtures according to the invention contain two or more polyphenylethers of the general formula

in which A is oxygen, sulfur or selenium or

ler isopropylidene radicals, with at least y3

of the atoms A are oxygen atoms and no more than y3 of the atoms A are sulfur and/or selenium atoms and where n means the number of substituents B linked to the phenyl radicals and is 0 or a whole number, and where B is tert-butyl or alpha-cumyl -groups, and

at least y3 of the bonds from the phenyl radicals to A calculated for the entire mixture as a whole are in the meta position in relation to each other.

The polyphenyl ether mixture preferably has an average of 3-8 phenyl radicals per molecule, an average of 4-6 phenyl radicals per molecule is particularly preferred. molecule.

In preferred mixtures, 40-100% of the groups A are oxygen atoms and the other groups A are isopropylidene radicals (CE, -

IN

C-CH,j). Mixtures in which a part of

IN

the groups A are sulfur and/or selenium are particularly suitable as lubricants at high bearing pressure.

In a preferred embodiment of the invention, at least 50 percent by weight of the mixture consists of components in which all groups A are in the meta position in relation to each other or at least 60 percent by weight of the mixture consists of components in which at least % of the groups A are in the meta position in relation to each other. Furthermore, it is preferred that at least 25% by weight of the mixtures consist of components in which all groups A are oxygen atoms and the phenyl radicals have no substituents B.

A preferred embodiment of the present invention comprises mixtures in which at least one component contains both such groups A which are in the meta position in relation to each other, as well as groups A which are in the ortho position and/or para position in relation to each other within one and the same molecule . This is a particularly effective way to lower the pour point of the mixture. The effect is enhanced when the number of metabonds is at least % of the total, and preferably between approx. 75 and 90% of the bonds, the others being either ortho or para bonds, preferably the latter.

Table I indicates typical polyphenyl ethers that may be present in the mixtures.

Table 1: bis(meta-phenoxyphenyl)-ether bis(para-phenoxyphenyl)-ether bis(ortho-phenoxyphenyl)-ether meta-bis(meta-phenoxyphenoxy)-benzene meta-bis(para -phenoxyphenoxy)-benzene para-bis (meta-phenoxyphenoxy) -benzene meta(meta-phenoxyphenoxy) (meta-tert-bu tylf enoxyphenoxy)-benzene meta(meta-alpha-cuimylphenoxyphenoxy) (meta-phenoxyphenoxy)-benzene meta(meta-tert-butylphenoxyphenoxy) (para-tert-butylphenoxyphenoxy)benzene Preferred compositions include an ether of the formula

in which A are oxygen atoms or isopropylidene radicals and B and n have the same meaning as above, and where the molar ratio between the first ether and the second ether is between 1 : 2 and 9 : 1.

Other preferred mixtures include m-bis(m-phenoxyphenoxy)-benzene and ortho- and/or para-isomers thereof, the molar ratio between metaether and the other ethers being between 1:2 and 9:1.

The mixtures according to the invention can of course be prepared by mixing selected types of polyphenyl ethers. A particularly advantageous method for producing the mixtures according to the invention consists in allowing a mixture of suitable alkali metal phenolates, hereinafter abbreviated as alkali metal phenates, to react with a suitable mono- or dibromaryl compound. Alternatively, a single alkali metal phenate is reacted with a mixture of mono- or dibromaryl compounds or a mixture of alkali metal phenates is reacted with a mixture of mono- or dibromaryl compounds. The reagents and their quantities are chosen so that the desired mixture of polyphenyl ethers is obtained. This presents no difficulties.

The conditions under which such reactions can take place include heating the reagents (an excess of alkali metal phenate of 5-10 mole percent is used) for a period of time between approx. 0.5 and approx. 10 hours at a temperature between approx. 150° C and approx. 300° C. The reaction can be carried out in the presence of a catalyst such as copper, the catalyst being present in amounts of between approx. 0.1 and approx. 20 grams per moles of alkali metal phenate. After the reaction is finished, the hot reaction mixture is diluted by emptying it into a solvent such as e.g. cold toluene or xylene and the alkali metal bromide which is the by-product of the reaction are filtered off.

Suitable monobromaryl compounds for use in reactions of this type are listed in Table 2.

Table 2: l-alpha-cumyl-3-bromobenzene l-alpha-cumyl-2-bromobenzene dimethyl-(meta-tert-butylphenyl)-(meta- bromophenyl)methane phenyl-(metabromophenyl)-ether (meta-tert-butylphenyl)-(meta-bromophenyl)

-ether

phenyl-(2-tert-butyl-3-bromophenyl)-ether phenyl-(para-foromphenyl)-ether phenyl-(ortho-bromphenyl)-ether ortho-, meta-, and para-tert-butylbromobenzenes

(ortho-tert-butylphenyl) - (ortho-bromophenyl) -

ether

(meta-tert-butylphenyl)-(para-bromophenyl)-ether

(para-tert-butylphenyl) (para-bromophenyl) -

ether.

Suitable dibromaryl compounds for use in reactions of this type are listed in Table 3.

Table 3:

0-, m- and p-dibromobenzenes 1-tert-butyl-3,5-dibromobenzene l-tert-butyl-2,4-dibromobenzene l-tert-butyl-2,6-dibromobenzene l-alpha-cumyl-3, 4-dibromo<bene l-alpha-cumyl-2,5-dibromobenzene l-alpha-cumyl-3,6-dibromobenzene l-alpha-cumyl-4,6-dibromobenene l-tert-butyl-3,6-dibromobenzene l -tert-butyl-2,5-dibromobenzene

1-alpha-cumyl-3,5-dibromobenzene

Suitable alkali metal phenates that can be used in the above reaction are listed in table 4.

Table 4: potassium-meta-phenoxyphenate potassium-para-phenoxyphenate potassium-ortho-phenoxyphenate sodium-meta-phenoxyphenate potassium-meta-alpha-cumylphenate potassium-meta (meta-tert-butylphenoxyl) -

fanate

sodium para (para-tert-butylphenoxy)-phenate

potassium meta-phenoxy (para-tert-butylphenate) potassium meta-phenoxy (para-tert-butylphenate)

lithium meta-(meta-phenoxyphenoxy)-phenate

Of the alkali metal phenates, potassium phenates are preferred.

If one wishes to use a mixture of the alkali metal phenate, such a mixture can be prepared synthetically by regrouping the substituents, e.g. by heating para-bromo-phenoxy-phenyl ether in the presence of an alkali such as potassium hydroxide for 1-10 hours at temperatures of around 250-350° C, which results in a partial rearrangement of the substituents, so that there a mixture comprising potassium meta-phenoxy-phenate and potassium para-phenoxy-phenate is formed.

The following examples will further illustrate the invention.

Example 1:

A mixture of 1.1 mol of potassium meta-phenoxyphenate, 1 mol of potassium para-phenoxyphenate and 2 mol of (para-tarom-phenyl)-phenyl ether was heated for 4 hours at 200-250° C. The reaction mixture was poured into toluene, filtered, dried and the toluene was distilled off. The product was a mixture of (meta-phenoxyphenyl)-(para-phenoxy-phenyl)-ether and bis-(para-phenoxyphenyl)-ether.

In each of the following examples, essentially the same reaction conditions were used.

Example 2:

Reagents: potassium meta-phenoxyphenate-1.1 mol potassium para-phenoxyphenate-1 mol mixture of isomeric dibromobenzenes (60% meta-isomer-1 mol Product: mixture of isomeric tus-^phenoxyphenyl)-benzenes, of which approx. y3 is meta-bis-(meta-phenoxyphenoxy)-benzene.

Example 3:

Reagents: potassium meta-(alpha-cumyl)-phenate-1 mol

potassium para-(alpha-cumyl)-phenate-1 mol (para-bromophenyl)-phenyl ether-1 mol

Product:

mixture of (meta-alpha-cumylphenyl)-(pa- α-phenoxyphenyl)-ether and (para-phenoxy-phenyl)-(para-alpha-cumylphenyl)-ether.

Example 4:

Reagents: potassium-meta-(alpha-cumyl)-phenate-1.1 mol potassium-para-(alpha-cumyl)-phenate-1 mol mixture of isomeric dibromobenzenes-1 mol

Products:

mixture of (alpha-cumylphenoxy)-benzenes with meta-bis-(meta-alpha-cumylph enoxy)-benzene predominating.

Example 5:

Reagents: potassium meta-phenoxyphenate-1.1 mol potassium para-phenoxyphenate-1 mol dimethyl-(phenyl)-(para-bromo-phenyl)-methane

Product:

mixture of (metaphenoxyphenyl)-(para- alpha-cumylphenyl)-ether and (paraphenoxy-phenyl)-(para-alpha-cumylphenyl)-ether.

Example 6:

Reagents: potassium meta-phenoxyphenate-1.1 mol potassium para-phenoxyphenate-1 mol mixture of isomeric tert-butyl-dibromobenzenes.

Product:

mixture of isomers (phenoxyphenyl)-tert- butyl benzenes with meta-bis-(phenoxy-phenyl)-tert-butyl benzenes in excess.

Example 7:

Reagents: potassium 2-tertbutyl-3-phenoxyphenate-1.1 mol potassium 4-phenoxyphenate-1 mol mixture of isomeric dibromobenzenes, containing 60% meta isomer.

Product:

mixture of meta-bis-(2-tertbutyl-3-phen- oxyphenyl) ether and para-bis-(4-phenoxy-phenyl) ether.

For certain applications, the mixtures according to the invention can be improved by adding additives such as e.g. agents for lowering the pour point, agents for improving the viscosity index, thickeners, antioxidants, agents against corrosion, agents against film formation and additives for use at extreme pressures.

When temperatures below approx. 150° C is pre-exposed, while the lubricant retains its properties, agents can be used to lower the pour point and agents to improve the viscosity index, such as e.g. polymers of esters of acrylic acid or of 2-alkylacrylic acid. The most suitable polymers have a relative molecular weight between 100 and 180 centistokes, but polymers with a relative molecular weight of up to 400 centistokes can also be used. The term "relative molecular weight" means the viscosity in centistokes at 38° C. (100° F.) of a 30 weight percent solution of the polymer in toluene. Typical esters that can be used to produce such polymers are methyl, ethyl, n-propyl, isopropyl, isobutyl, lauryl, phenyl or benzyl esters of acrylic acid, methacrylic acid, 2-ethylacrylic acid, 3yre and 2-propylacrylic acid. Typical suitable commercially available polymers are polymers based on alkyl methacrylates with 8-12 carbon atoms. The polymers can be homopolymers of a single ester or they can be copolymers of a mixture of such esters, and the term "polymerisate" is therefore to be understood in accordance with this in the present preparation. The polymers can be used in the present substance compositions in amounts of 2 to 30 percent by weight calculated on the entire mixture. In general, from 5 to 15 percent by weight is the most advantageous ratio within the aforementioned range.

Some of the commercially available polymers that are suitable for use in the mixtures according to the invention are not stable under shear stresses (shear-stable), and if such polymers are used it is desirable that they are subjected to shear stresses, e.g. . by allowing them to pass through an injection nozzle before being added to the mixture. Alternatively, the polymers can be mixed with one or more components of the mixtures and subjected to such shear stress before use.

Suitable agents against film formation for addition to the mixtures according to the invention are salts of aromatic carboxylic acids or of phenols and metals of group 2 in the periodic table, which salts are soluble in polyphenyl ethers. These salts increase the heat resistance and oxidation resistance of the mixtures at high temperatures and prevent film formation at lower ones. Of the metals in group II, zinc and calcium are the most suitable for the present purpose, but beryllium, magnesium, strontium, cadmium, barium or mercury salts can also be used. The salts are preferably used in such quantities that the metal content in the finished mixture is between 0.01 and 1.0 percent by weight. Normal or basic salts or mixtures of normal and basic salts can be used. Suitable aromatic acids, which are used in the form of salts with metals from group II, are benzoic acid, naphtholic acid, 4-tert-butyl-benzoic acid, 2,4-di-tert-butylbenzoic acid, di-iso-propylsalicylic acids, octylsalicylic acids, pentadecenylsalicylic acids, octadecyl salicylic acids, stearyl salicylic acids and octyl-4-hydroxybenzoic acids. The salts of alkylated hydroxybenzoic acids are particularly advantageous and they can be used in mixture with each other. One can thus use salts of mixtures of alkylated hydroxybenzoic acids, obtained by reaction between salicylic acid or 4-hydroxybenzoic acid with a mixture of alkenes, such as e.g. a mixture obtained by cracking paraffin wax, or with a mixture of alcohols in the presence of a suitable condensing agent of the Friedel-Crafts type. Salts of a mixture obtained by alkylating a phenol with a mixture of alkenes or alcohols can likewise be used, the alkylphenols formed being transferred to alkylsalicylic acids by means of the Kolbe-Schmidt reaction.

Suitable phenols for use in the form of salts with metals from group II in the present lubricating oils are phenol itself, naphthols, cresols and the higher alkylated phenols, such as e.g. amyl, octyl, nonyl, decyl, tetradecyl, pentadecenyl and octadecyl phenols. Salts or mixtures of alkylphenols, e.g. those formed by the alkylation of a phenol with mixtures of alkenes can be used and are preferred because of their lower melting points compared to the melting points of pure alkyl phenols. Mixtures of alkenes obtained from paraffin wax by cracking or from higher fatty alcohols by dehydration are valuable and easily available starting materials for the production of such mixtures of alkylphenols. Thus, one can use a mixture of alkylphenols produced by alkylation of phenol or a cresol or 1- or 2-naphthol with a mixture of alkenes, containing from 8-18 carbon atoms in the molecule and produced by the above-mentioned method. There may also be more than one alkyl or alkenyl group present in the phenolic compound, such as e.g. in the case of compounds prepared by di- or tri-alkylation of phenols with alkenes, alkyl halides, alcohols or ethers, or in compounds prepared by monoalkylation of e.g. a cresol, a xylenol, carvacrol, or cardanol. Other substituents such as halogen atoms or alkoxy, alkylmer-capto and alkylamino groups may be present in the phenolic compound.

Particularly effective metal salts are the zinc salts of alkylated salicylic acids, containing 8-20 carbon atoms in the alkyl group. A particularly effective compound is the zinc salt of a mixture of alkylsalicylic acids produced by alkylation of phenol with a mixture of alkenes, containing 14-18 carbon atoms in the molecule with subsequent transfer of the obtained alkylphenols to the corresponding salicylic acids by means of the Kolbe-Schmidt reaction.

Where the ability to withstand high loads is required, additives can be used for this. Examples of suitable such additives are the trialkyl, triaryl or trialkyl phosphates, which e.g. trioctyl or tricresyl phosphate, as well as the haloalkylphosphonates, such as e.g. monobutyl hydrogen trichloromethyl phosphonate and its amino salts, such as the salt with di(2-ethylhexyl)amine.

Claims (9)

1. Lubricant mixture, characterized in that it comprises a mixture of two or more polyphenylethers of the general formula in which A are oxygen, sulfur or selenium atoms or isopropylidene radicals, at least y3 of the groups A are oxygen atoms and no more than y3 of the groups A are sulfur and/or selenium atoms, n means the number of substituting groups B linked to the phenyl radicals and is 0 or a whole number, the groups B being tertbutyl or alphacumyl groups, and where at least y3 of the links A between the phenyl radicals calculated for the entire mixture are in the meta position in relation to each other. 2. Mixture according to claim 1, characterized in that the polyphenyl ethers have on average 3-8, especially 4-6 phenyl radicals per molecule. 3. Mixture according to any of the preceding claims, characterized in that 40-100% of the connecting links A between the phenyl radicals are oxygen atoms and the other connecting links A between the phenyl radicals are isopropylidene radicals. 4. Mixture according to any of the preceding claims, characterized in that at least 50 percent by weight of the mixture consists of compounds in which the links A between the phenyl radicals are in the meta position in relation to each other. 5. Mixture according to any one of claims 1-3, characterized in that at least 60% by weight of the mixture consists of compounds in which at least % of the links A between the phenyl radicals are in the meta position in relation to each other. 6. Mixture according to any of the preceding claims, characterized in that at least 25 percent by weight of the mixture consists of compounds in which all members. A between the phenyl radicals are oxygen atoms and that the phenyl radicals have no substituents B. 7. Mixture according to any of the preceding claims, characterized in that at least one compound is present in which part of the links A between the phenyl radicals are in the meta position in relation to each other and the other links A are in the ortho- and/or para- position in relation to each other. 8. Mixture according to claim 1, characterized in that it comprises an ether with the general formula and an ether with the general formula in which A are oxygen atoms or isopropylidene radicals and B and n have the same meaning as stated in claim 1, and where the molar ratio between the first ether and the second lies between 1 : 2 and 9 : 1. 9. Mixture according to claim 1, characterized in that it contains meta-bis-(meta-phenoxyphenoxy)-benzene together with ortho-to- and/or para-isomers thereof, and where the molar ratio between metaether and the other ethers lies between 1 : 2 and 9 : 1.