GB1591180A

GB1591180A - Mixed synthetic ester lubricant

Info

Publication number: GB1591180A
Application number: GB4329577A
Authority: GB
Original assignee: Hercules LLC
Current assignee: Hercules LLC
Priority date: 1977-10-18
Filing date: 1977-10-18
Publication date: 1981-06-17

Description

(54) MIXED SYNTHETIC ESTER LUBRICANT (71) We, HERCULES INCORPORATED, a Corporation organised under the laws of the State of Delaware, United States of America, of 910 Market Street, City of Wilmington, State of Delaware, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the lubricant art.

In summary, this invention comprises a composition of matter useful as a lubricant, comprising a blend of (1) a normally liquid pentaerythritol ester or mixture of esters and 2 a neopentylene glycol ester or mixture of esters, the weight ratio of said esters (1) and 2 being in a range from 2:3 to 9:1, said pentaerythritol ester or mixture of esters consisting of pentaerythritol material (as herein defined) fully esterified by at least one C4-C12 alkonoic acid said neopentylene glycol ester or mixture of esters having a substantially higher viscosity at 770F than said pentaerythritol ester or mixture of esters, and consisting of the reaction product of neopentylene glycol, at least one C4-C12 alkanedioic acid, and at least one C4-C12 alkanol, the mole ratio of said glycol to said alkanedioic acid to said alkanol being substantially n:(n + 1):2 with n being a whole number in the range from 1 to 12.

The term "normally liquid" means flowable or liquid at 770F.

The normally liquid pentaerythritol ester consists of pentaerythritol material completely esterified by at least one C4-C12 alkanoic acid. By the term "pentaerythritol material we mean a material consisting of at least one member of the group consisting of pentaerythritol and polypentaerythritols.

The pentaerythritol material in some embodiments of this invention comprises only one member qf the group consisting of pentaerythritol and polypentaerythritols, while in other embodiments it comprises two or more such members. Preferably the pentaerythritol material substantially consists of technical pentaerythritol, or technical dipentaerythritol, tripentaerythritol and tetrapentaerythritol, these being preferred. Especially preferred is a pentaerythritol material consisting substantially of monopentaerythritol, dipentaerythritol, tripentaerythritol and tetrapentaerythritol at weight ratios of about 35:38:19:8.

The or each C4-C12 alkanoic acid is a straight or branched chain alkanoic acid having 4-12 carbon atoms. In some embodiments of this invention there is only one such acid. In other embodiments of this invention there are two or more C4-C12 alkanoic acids. In preferred embodiments of this invention the C4-C12 alkanoic acid comprises one or more C6-C8 alkanoic acids. Also preferred are mixtures of normal C5-C9 alkanoic acids with an average carbon atom content of about 6.6. Examples of C4-C12 alkanoic acids include: butyric acid isobutyric acid valeric acid isovaleric acid alpha-methylbutyric acid pivalic acid caproic acid enanthic acid caprylic acid pelargonic acid and capric acid.

In one preferred form of this invention the alkanoic acid is a mixture of caprylic and capric acids and has an average carbon atom content of about 8.4.

Specific examples of the normally liquid pentaerythritol ester or mixture of esters are commercially available or can be made by processes well known to the art.

The neopentylene glycol ester or mixture of esters, specific examples of which at 77"F range from a flowable or liquid state to a wax-like consistency, is the reaction product of neopentylene glycol, at least one C4-C12 alkanedioic acid and at least one C4-C12 alkanol at mole ratios of substantially n:(n + 1):2, n being a whole number in a range from 1 to 12. A preferred mole ratio is 6:7:2.

The or each C4-C12 alkanedioic acid is a straight or branched chain alkanedioic acid having 4-12 carbon atoms. In some embodiments of this invention there is only one such acid. In other embodiments of this invention there are two or more C4-Cl2 alkanedioic acids.

Examples of such acids include: succinic acid glutaric acid adipic acid pimelic acid suberic acid and azelaic acid.

The or each C4-C12 alkanol is a straight or branched chain alkanol having 4-12 carbon atoms. In some embodiments of this invention there is only one such alkanol. In other embodiments of this invention these are two or more C4-C12 alkanols. Examples of such alkanols include: n-butanol sec. butanol t-butanol n-pentanol 2-methylbutanol n-hexanol 2,4-dimethylbutanol n-heptanol n-octanol 2-ethylhexanol n-nonanol n-decanol and n-dodecanol.

The weight ratio of the pentaerythritol ester or mixture of esters to the neopentylene glycol ester or mixture of esters is in a range from 2:3 to 9:1. In general, within this range as the weight ratio of pentaerythritol ester or mixture of esters to the neopentylene glycol ester or mixture of esters is increased the viscosities of the lubricant at temperatures from 0 to 210 F.

are decreased.

The lubricant of this invention is made by admixing the normally liquid pentaerythritol ester or mixture of esters and the neopentylene glycol ester or mixture of esters until an intimate blend is formed. While this is normally done at 77"F., such can be done also at higher and lower temperatures, with higher temperatures being preferred to lower temperatures because of the ease of admixing.

The lubricant can be used alone or with one or more additives. Thus, one or more alkali metal salts of higher fatty acids, for example, lithium stearate at 10 or more per cent by weight of the lubricant, can be added to thicken the lubricant and give a stable, water-resistant dispersion. Polybutene at 1% by weight of the lubricant or an isoalkyl methacrylate polymer at 0. 1-5 % by weight of the lubricant can be added to give body and smooth appearance to the lubricant. Sorbitan monooleate can be added to inhibit rusting of lubricated parts. Various antioxidants and thermal stabilizers, for example, 4,4'-dioctyl-diphenyl-amine at 0.75% by weight of the lubricant, and phenyl-p-naphthyl-amine at 0.75% by weight of the lubricant, can be added to further enhance the thermal and oxidative stability of the lubricant.

The lubricant either alone or with additives is used by applying it to surfaces to be lubricated. Generally, such surfaces are relatively movable with one surface bearing on the other.

The best mode now contemplated for carrying out this invention is illustrated by the following examples of various aspects of the invention, including specific embodiments. This invention is not limited to these specific embodiments. In these examples, unless otherwise indicated, all percentages are bv weight. Viscosity indices were calculated in accordance with ASTM D2270-64 Method B.

Examples 1-5 These examples illustrate specific embodiments of the lubricant of this invention, which embodiments are based on a normally liquid pentaerythritol ester mixture and a neopentylene glycol ester mixture, which products have the following characteristics.

The normally liquid pentaerythritol ester mixture consists of technical pentaerythritol (monopentaerythritol is about 88-90%, dipentaerythritol is about 10-12% fully esterified by an alkanoic acid mixture consisting of valeric acid (25%), caproic acid (15 who}, enathic acid (31%), caprylic acid (9%) and pelargonic acid (20%), with the average carbon atom content of the alkanoic acid mixture being about 6.6. The viscosity of this pentaerythritol ester mixture at 770F is typically about fifty centistokes.

of this pentaerythritol ester mixture at 770fits typically about fifty centistokes.

The neopentylene glycol ester mixture consists of the reaction product of neopentylene glycol, azelaic acid and 2-ethylhexanol at a mole ratio of 6:7:2. The viscosity of this neopentylene glycol ester mixture at 770F is typically about three thousand centistokes.

The composition of the blend of each example as well as typical properties of each blend are set forth in Table I.

TABLE I Blend Composition Pentaerythritol Neopentylene Clycol Viscosity Ex. Ester Mixture Ester Mixture (Centistokes) Viscosity No. Parts by Weight Parts by Weight 770F. 100 F. 210 F. Index 1 87 13 70 41 8.2 193 2 81 19 100 60 10 165 3 72 28 190 100 14 153 4 60 40 260 140 17 141 5 50 50 400 190 22 149 In each example the blend is made by admixing at 770F. the indicated quantities of the pentaerythritol ester mixture and the neopentylene glycol ester mixture until an intimate blend is formed.

Examples 6-10 These examples illustrate specific embodiments of a grease base stock of this invention based on another normally liquid pentaerythritol ester mixture and on the neopentylene glycol ester mixture of Examples 1-5.

The normally liquid pentaerythritol ester mixtures of these examples consists of technical pentaerythritol (monopentaerythritol is 88-98%, dipentaerythritol is 10-12So) fully esterified by an alkanoic acid mixture consisting of caprylic and capric acids with the average carbon atom content of the alkanoic acid being about 8.4. The viscosity of this pentaerythritol ester mixture at 77"F is about sixty centistokes.

The composition of the blend of each example and typical properties of each blend are in Table II.

TABLE II Blend Composition Pentaerythritol Neopentylene Glycol Viscosity Ex. Ester Mixture Ester Mixture (Centistokes) Viscosity No. Parts By Weight Parts By Weight 77"F. 100 F. 210 F. Index 6 70 30 200 114 17 173 7 65 35 250 141 19 163 8 60 40 310 172 23 171 9 55 45 390 210 27 173 10 50 50 440 235 27 158 The blend of each of these examples is made by admixing at 770F. the indicated quantities of the normally liquid pentaerythritol ester mixture and the neopentylene glycol ester mixture until an intimate blend is formed.

Examples 11-15 These examples illustrate specific embodiments of lubricant of this invention, which are based on still another normally liquid pentaerythritol ester mixture and on the neopentylene glycol ester mixture of Examples 1-5.

The normally liquid pentaerythritol ester mixture of these examples consists of technical dipentaerythritol (dipentaerythritol is 90-95%, monopentaerythritol is 5-10%) completely esterified by an alkanoic acid mixture consisting of valeric acid (25 %), caproic acid (15%) enanthic acid (31%) caprylic acid (9%) and pelargonic acid (20%) with the average carbon atom content of the alkanoic acid material being about 6.6. The viscosity of this pentaerythritol ester mixture at 770F. typically is about one hundred and twenty centistokes.

The composition of the blend of each example as well as typical properties of each blend are presented in Table III.

TABLE III Blend Composition 0106 0800 0900 1000 0406 Ex. Ester Mixture Ester Mixture (Centistokes) Viscosity No. Parts By Weight Parts By Weight 0 F. 77"F. 100 F.210 F. Index 11 70 30 9700 330 180 23 165 12 65 35 12400390 210 27 173 13 60 40 15600 470 250 29 163 14 55 45 19600560 280 33 171 15 50 50 17400 660 330 37 169 The blend of each of these examples is made in the same way as the blends of Examples 1-5 and 6-10.

Examples 16-18 These examples illustrate specific embodiments of a lubricant of this invention, which comprise yet another normally liquid pentaerythritol ester mixture of this example consists of monopentaerythritol, dipentaerythritol, tripentaerythritol and tetrapentaerythritol at weight ratios of about 35:38:19:8, fully esterified by the alkanoic acid mixture described in connection with Examples 1-5. The viscosity of this pentaerythritol ester mixture at 770F typically is about one hundred and fifty centistokes.

The composition of the blend of each example as well as typical properties of each blend are given in Table IV. TABLE IV Blend Composition Pentaerythritol Neopentylene Glycol Viscosity Ex. Ester Mixture Ester Mixture (Centistokes) Viscosity No. Parts By Weight Parts By Weight 77"F. 100 F. 210 F. Index 16 90 10 200 110 15 153 17 85 15 240 130 17,5 155 18 80 20 320 170 20 146 Each blend of these examples is made in the same way as the blends of Examples 1-5.

As is evident from the typical data for each of the blends of Examples 1-18, each embodiment of the lubricant of this invention is characterized by a high viscosity index and by substantial viscosity at 2100F. These properties are important when the lubricant is used at high temperatures and loads, and resistance to flow from the lubrication area and maintenance of the load bearing properties of the grease are necessary.

Each embodiment of the lubricant of this invention is also characterized by outstanding thermal stability. For example, when a lubricant consisting of the blend of Example 6, 4,4'-dioctyl-diphenyl-amine (0.75% by weight) and phenyl-p-naphthyl-amine (0.75% by weight) is heated in air at a temperature increase of 5"C. per minute, up to 300"C. there is no significant weight loss due to thermal degradation.

Another feature of advantage of the lubricant of this invention is its low volatility. The high average molecular weight of the blend combined with the polarity of the ester groups gives the composition very low volatility. For instance, when the blend of Example 6 is heated in air at a rate of 5"C. per minute, no significant volatile loss occurs up to 2500C., and when the blend is heated at 400at. for 6.5 hours in-air during the ASTM D972056 evaporation test, the typical weight loss is only 0.8%.

Still another feature of advantage of the lubricant of this invention is its outstanding corrosion and oxidation stability. For example, when the blend of Example 6 is subjected to the MIL-L-23699 B corrosion and oxidation stability test at 4000F. for 72 hours in the presence of steel, silver, aluminum, magnesium and copper, typically no pitting, etching, staining or corrosion is observed. Moreover, the viscosity at 1000F. typically increases only 13 % during this time and the acid number increases by 1. Also, generally there is practically no accumulation of sludge during the test. These results show the lubricant resists deterioration when heated in the presence of oxygen and metals, and does not attach typical metals found in lubrication applications.

Consequently, this invention provides a highly desirable lubricant especially for use in high temperature applications.

WHAT WE CLAIM IS: 1. A composition of matter useful as a lubricant, comprising a blend of (1) a normally liquid pentaerythritol ester or mixture of esters and (2) a neopentylene glycol ester or mixture of esters, the weight ratio of said esters (1) and (2) being in a range from 2:3 to 9:1, said pentaerythritol ester or mixture of esters consisting of pentaerythritol material (as herein defined) fully esterified by at least one C4-C12 alkanoic acid, said neopentylene glycol ester or mixture of esters having a substantially higher viscosity at 770F than said pentaerythritol ester or mixture of esters, and consisting of the reaction product of neopentylene glycol, at least one C4-C12 alkanedioic acid, and at least one C4-C12 alkanol, the mole ratio of said glycol to said at alkanedioic acid to said alkanol being substantially n:(n + 1):2 with n being a whole number in the range of 1 to 12.

2. A composition according to Claim 1 in which the alkanedioic acid is azelaic acid, and the alkanol is 2-ethylhexanol.

3. A composition according to Claim 1 or 2 in which said mole ratio is 6:7:2.

4. A composition according to Claim 1, 2 or 3, in which the alkanoic acid is a mixture of caprylic and capric acids and has an average carbon atom content of about 8.4.

5. A composition according to Claim 1, 2 3 or 4, in which the pentaerythritol material is technical pentaerythritol.

6. A composition according to Claim 1, 2, 3 or 4 in which the pentaerythritol material is technical dipentaerythritol.

7. A composition according to any one of Claims 1 to 4 in which the pentaerythritol material is a mixture of monopentaerythritol, dipentaerythritol, tripentaerythritol, and tet rapentaerythritol at weight ratios of about 35:38: 19:8.

8. A composition according to any one of Claims 1 to 7 in which the alkanoic acid consists of normal C5-C9 alkanoic acids with an average carbon atom content of about 6.6.

9. A process for making a lubricant, which comprises blending (1) a normally liquid pentaerythritol ester or mixture of esters with (2) a neopentylene glycol ester or mixture of esters at a weight ratio of pentaerythritol ester or mixture of esters to said glycol ester or mixture of esters in a range from 2:3 to 9:1, said pentaerythritol ester or mixture of esters consisting of pentaerythritol material (as herein defined) fully esterified by at least one C4-C12 alkanoic acid, said neopentylene glycol ester or mixture of esters having a substan tially higher viscosity at 77"F than said pentaerythritol ester or mixture of esters, and consisting of the reaction product of neopentylene glycol, at least one C4-C12 alkanedioic acid and at least one C4-C12 alkanoic acid, said neopentylene glycol ester or mixture of esters having a substantially higher viscosity at 770F than said pentaerythritol ester or mixture of esters, and consisting of the reaction product of neopentylene glycol, at least one C4-C12 alkanedioic acid and at least one C4-C12 alkanol, the mole ratio of said glycol to said alkanedioic acid to said alkanol being n: (n + 1):2, n being a whole number in the range from 1 to 12.

10. A lubricant when made by the process of Claim 9.

11. A method of lubricating relatively movable surfaces, one of which bears on the other, which comprises applying to said surfaces a lubricant in accordance with any one of Claims 1 to8or10.

12. Lubricant compositions substantially as described in the foregoing Examples.

13. A process for making a lubricant substantially as described herein with reference to .the Examples.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the composition very low volatility. For instance, when the blend of Example 6 is heated in air at a rate of 5"C. per minute, no significant volatile loss occurs up to 2500C., and when the blend is heated at 400at. for 6.5 hours in-air during the ASTM D972056 evaporation test, the typical weight loss is only 0.8%. Still another feature of advantage of the lubricant of this invention is its outstanding corrosion and oxidation stability. For example, when the blend of Example 6 is subjected to the MIL-L-23699 B corrosion and oxidation stability test at 4000F. for 72 hours in the presence of steel, silver, aluminum, magnesium and copper, typically no pitting, etching, staining or corrosion is observed. Moreover, the viscosity at 1000F. typically increases only 13 % during this time and the acid number increases by 1. Also, generally there is practically no accumulation of sludge during the test. These results show the lubricant resists deterioration when heated in the presence of oxygen and metals, and does not attach typical metals found in lubrication applications. Consequently, this invention provides a highly desirable lubricant especially for use in high temperature applications. WHAT WE CLAIM IS:

1. A composition of matter useful as a lubricant, comprising a blend of (1) a normally liquid pentaerythritol ester or mixture of esters and (2) a neopentylene glycol ester or mixture of esters, the weight ratio of said esters (1) and (2) being in a range from 2:3 to 9:1, said pentaerythritol ester or mixture of esters consisting of pentaerythritol material (as herein defined) fully esterified by at least one C4-C12 alkanoic acid, said neopentylene glycol ester or mixture of esters having a substantially higher viscosity at 770F than said pentaerythritol ester or mixture of esters, and consisting of the reaction product of neopentylene glycol, at least one C4-C12 alkanedioic acid, and at least one C4-C12 alkanol, the mole ratio of said glycol to said at alkanedioic acid to said alkanol being substantially n:(n + 1):2 with n being a whole number in the range of 1 to 12.

3. A composition according to Claim 1 or 2 in which said mole ratio is 6:7:2.

10. A lubricant when made by the process of Claim 9.