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1. (WO2018108869) UTILISATION DE POLYESTERS COMME AMÉLIORANTS D'INDICE DE VISCOSITÉ POUR FLUIDES HYDRAULIQUES D'AÉRONEFS
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Claims

A composition comprising a polyester and a phosphate ester base stock,

wherein

the polyester comprises from 30 mol% to 50 mol%, based on the total number of repeating units constituting the polyester, of repeating units of Formula I


Formula I

and

from 25 mol% to 50 mol%, based on the total number of repeating units constituting the polyester, of repeating units of Formula II


Formula I I

wherein is represented by a C-|.g-alkyl group,

is a hydrogen atom or a C-|.g-alkyl group, and

R1 and together may form a cycloalkane structure; and

the phosphate ester base stock substantially consists of one or several compounds, each of which being represented by Formula I II ;


Formula II I

wherein R3, R and R5 are each independently selected from a C-|.g-alkyl group.

Composition according to Claim 1 , wherein the phosphate ester base stock substantially consists of tributylphosphate, triisobutylphosphate or a mixture thereof.

3. Composition according to Claim 1 or 2, wherein the weight average molecular weight Mw of the polyester is from 5 000 g/mol to 60 000 g/mol, preferably from 10 000 g/mol to 40 000 g/mol, more preferably from 20 000 g/mol to 30 000 g/mol, determined according to DIN 55672-1.

4. Composition according to any of Claims 1-3, wherein R1 in Formula II is a methyl group and is a hydrogen atom or a methyl group.

5. Composition according to any of Claims 1-4, wherein the polyester comprises 50 mol%, based on the total number of repeating units constituting the polyester, of repeating units of Formula I and

50 mol%, based on the total number of repeating units constituting the polyester, of repeating units of Formula II, wherein and R2 in Formula II are both represented by methyl groups.

6. Composition according to any of Claims 1-5, wherein the polyester has an acid value from 0.01 to 3.0 mg KOH/g and a hydroxyl value from 5.0 to 20.0 mg KOH/g.

7. Composition according to any of Claims 1-6, wherein the polyester has a polydispersity index Mw/Mn from 2.0 to 5.0, preferably from 2.5 to 4.5.

8. Composition according to any of Claims 1-7, wherein the polyester comprises end groups and more than 80 mol%, preferably more than 90 mol% of end groups, based on the total number of end groups in the polyester, are hydroxyl groups.

9. Composition according to any of Claims 1-8, wherein the polyester is an amorphous

polymer and has a glass transition temperature Tg below -35 °C.

10. Composition according to any of Claims 1-9, wherein the composition substantially consists of the polyester and the phosphate ester base stock.

1 1. Composition according to any of Claims 1-10, wherein the composition comprises

from 45 to 75 wt.-%, based on the weight of the composition, of the polyester and from 25 to 55 wt.-%, based on the weight of the composition, of the phosphate ester base stock,

and the phosphate ester base stock substantially consists of tributylphosphate, triisobutylphosphate or a mixture thereof.

12. Composition according to Claim 1 1 , characterized in that it substantially consists of the polyester and the phosphate ester base stock.

Composition according to any of Claims 1-10, wherein the composition comprises from 45 to 75 wt.-%, based on the weight of the composition, of the polyester and from 25 to 55 wt.-%, based on the weight of the composition, of the phosphate ester base stock,

wherein the polyester comprises from 30 mol% to 50 mol%, preferably 50 mol%, based on the total number of repeating units constituting the polyester, of repeating units of Formula I


Formula I

and

from 25 mol% to 50 mol%, preferably 50 mol%, based on the total number of repeating units constituting the polyester, of repeating units of Formula II


Formula II

wherein is a methyl group and

is a hydrogen atom or a methyl group; and

the phosphate ester base stock substantially consists of tributylphosphate,

triisobutylphosphate or a mixture thereof.

A hydraulic liquid for an aircraft comprising the composition according to any of Claims 1- 13, wherein the hydraulic liquid comprises

from 0.5 wt% to 20 wt%, based on the weight of the hydraulic liquid, of the polyester and not less than 50 wt.%, based on the weight of the hydraulic liquid, of the phosphate ester base stock.

Hydraulic liquid according to Claim 14, wherein the hydraulic liquid substantially consists of the polyester, the phosphate ester base stock and at least one further additive selected from corrosion inhibitors, antifoam agents, acid scavengers and dyes.

16. Hydraulic liquid according to Claim 14 or 15, wherein the hydraulic liquid has a kinematic viscosity at 100°C (KV100) of from 2.0 to 5.0 cSt and a kinematic viscosity at -54°C (KV- 54) of not higher than 2 000 cSt.

17. Use of the composition according to any of Claims 1-13 for the manufacturing of a hydraulic liquid of an aircraft, wherein the hydraulic liquid has a viscosity index (VI) from 200 to 400, preferably from 250 to 350.