WO2023156947A1

WO2023156947A1 - Plastic grease composition and method of its manufacture

Info

Publication number: WO2023156947A1
Application number: PCT/IB2023/051438
Authority: WO
Inventors: Jerzy Antoni Raszkiewicz
Original assignee: Jerzy Antoni Raszkiewicz
Priority date: 2022-02-17
Filing date: 2023-02-17
Publication date: 2023-08-24
Also published as: PL440408A1

Abstract

The object of the invention is a plastic grease composition comprising: - a base oil selected from mineral oil derived from petroleum distillation, paraffinic oil, naphthenic oil, recycled oil, hydrocarbon oil containing lubricating oils, synthetic oil, and mixtures thereof; - a soap-type thickener of the formula R-Me, where R is derived from hydroxyacid, hydroxyacid ester containing 9-36 carbon atoms, or mixtures thereof, and Me is calcium; - a polyurea polymer type thickener; characterized in that the polyurea polymer type thickener present in an amount of 1-5 wt% is represented by the formula (R'-NH-CO-NH-Ar-NH-CO-NH-R'')n, where: R' is derived from a primary amine containing from 12-18 carbon atoms; R" is derived from an aliphatic or aromatic diamine containing from 2-16 carbon atoms; Ar is an aromatic hydrocarbon containing from 6-20 carbon atoms; n is between 2 and 20. Another object of the invention is a method for producing a plastic grease composition according to the invention, characterized in that it includes the following steps: a. into a reactor equipped with a stirrer is introduced, at a temperature of 15-40°C, a base oil selected from mineral oil derived from the distillation of crude oil, paraffinic oil, naphthenic oil, recycled oil, hydrocarbon oil containing lubricating oils, synthetic oil, and mixtures thereof; b. then, a primary amine of 12-18 carbon atoms and a secondary amine of 2-6 carbon atoms in a molar ratio of 2:1 are added successively to the base oil, and stirring with heating to 40-70°C is performed to obtain a homogeneous mixture of amines; c. then, diisocyanate is added under normal pressure in a molar ratio of diisocyanate: primary amine: secondary amine of 2:2: 1; d. after mixing, a hydroxy acid or hydroxy acid ester containing from 9-36 carbon atoms, or a mixture thereof, is added in an amount of 4-6% by weight of the total weight of the grease composition, and after dissolving it in the polymer, a mixture of lime in base oil is added under normal pressure; e. the reactor is heated until the temperature inside the reactor reaches 100-120°C; f. after dehydration, base oil is added to the reactor in the amount of 25-30% per total weight of the grease composition and heated to 110- 130°C until the reactor contents are thickened; g. once the thickening is achieved, the mixture is cooled with base oil in an amount of 30-40% by total weight of the grease composition; h. optional enriching agents selected from the group including: anticorrosive, antioxidant, anti-aging, anti¬ wear, friction-reducing and high-pressure resistance agents are added to the resulting grease; i. the resulting grease is subjected to homogenization and degassing.

Description

Plastic grease composition and method of its manufacture

The subject of the invention is a composition of plastic grease and a method of its manufacture. The plastic grease according to the invention is a multipurpose grease that can be used especially for bearings of all kinds, furnace chains, joints and, in any case, as a substitute for lubricating oil in the temperature range from -40 to 200°C.

In the art, there are known solutions for the manufacture of silicone greases, providing for the use of the following components: methylsiloxane and phenylmethylsiloxane oils, polyalphaolefin oils, diphenylethers, perfluorinated alkylpolyethers and mineral oils, organic and inorganic thickeners, such as polyureas, metallic salts of fatty acids, colloidal silica, and enriching agents: aromatic amines, phosphate esters, benzotriazole derivatives, and solid greasing substances such as colloidal graphite, zinc diethyldithiocarbamate.

As disclosed in the Polish patent PL199440, the plastic grease based on renewable dispersing phases is characterized by the fact that it contains from 8 to 25% by weight of lithium 12- hydroxystearate and from 75 to 92% by weight of triglyceride of higher fatty acids, preferably a natural oil with the following properties: iodine number in the range of 80 to 150 mg /lOOg, preferably 108 to 138 mg /lOOg, kinematic viscosity at 40°C in the range of 25.0 mm2/s to 50.0 mm2/s, preferably 30 to 40 mm2/s, viscosity index from 160 to 250, preferably 190 to 240 and freezing point from -25°C to 0°C, preferably -17°C to 0°C.

The invention described in the PL/EP Publication 3268455 T3 relates to a method of manufacturing solid greases based on lignin derivatives thickened with a polyurea thickener, solid greases manufactured this way, and the use of such solid greases in gearboxes, synchronous pivot shafts and sealed rolling bearings, among others.

Polyurea greases are disclosed in a number of patent applications, including EP 0435745 Al, EP 0508115 Al, EP 0558099 Al, and EP 0661378 Al.

The constant velocity joint grease composition described in EP 0508115 Al includes a base oil containing a thickener and boron nitride powders, and, alternatively, an organotin compound. The thickener used may be a soap-type thickener or a polyurea thickener.

In addition, the European application EP 3613832 describes plastic grease and a method of its manufacture, which contains a polyurea/high base calcium sulfonate composite thickener, colloidally dispersed solid particles of calcium carbonate in the form of calcite, calcium borate or a calcium borate composite, and a calcium soap of fatty acid with 12 to 24 carbon atoms. The above components are uniformly dispersed in an oil phase environment.

U.S. Patent US 5084193 discloses a grease with improved dropping point and shear resistance, containing polyurea and calcium soap, particularly derived from 12-hydroxystearic acid. It should be noted that in the cited patent document, the polyurea used is diurea produced under pressure and in an autoclave in the presence of water, which is detrimental to the isocyanate group, since water causes deactivation of isocyanates, the precursors of polyurea. In the composition of the grease according to the cited patent US 5084193, tetraurea is not used as a thickener of the polyurea polymer type. Moreover, the grease production technology itself is complicated, and the total percentage of thickeners (polyurea type and soap type) is very high, above 10%. The aim of the invention was, on the one hand, to develop a plastic grease composition that retains greasing properties at temperatures above 180°C, and on the other hand, to replace the widespread use of lithium soap in greases due to the limited supply of lithium hydroxide (used in the production of cells for the automotive industry), to reduce manufacturing costs, as well as CO2 emissions The premise was to obtain, in a relatively simple way, plastic grease having a dropping point clearly above 200°C, good shear strength, limited thixotropy, mechanical stability, corrosion resistance, and good performance in the Brinell test, as well as a positive economic effect compared to lithium grease having dropping points below 200°C, and therefore their use below 130°C. In addition, the developed technology allows the "in situ" production of different grades of greases with different dropping temperatures depending on the polymer content.

The object of the invention is a plastic grease composition comprising:

- a base oil selected from mineral oil derived from petroleum distillation, paraffinic oil, naphthenic oil, recycled oil, hydrocarbon oil containing lubricating oils, synthetic oil, and mixtures thereof;

- a soap-type thickener of the formula R-Me, where R is derived from hydroxyacid, hydroxyacid ester containing 9-36 carbon atoms, or mixtures thereof, and Me is calcium;

- a polyurea polymer type thickener; characterized in that the polyurea polymer type thickener present in an amount of 1-5 wt% is represented by the formula (R'-NH-CO-NH-Ar-NH-CO-NH-R")_n, where:

R¹ is derived from a primary amine containing from 12-18 carbon atoms;

R" is derived from an aliphatic or aromatic diamine containing from 2-16 carbon atoms;

Ar is an aromatic hydrocarbon containing from 6-20 carbon atoms; n is between 2 and 20.

Preferably, R is derived from 12-hydroxy stearic acid, hydrogenated ricinoleic acid, fatty acid of animal or vegetable origin containing from 9-36 carbon atoms, salicylic acid, hydroxybenzenesulfonic acid.

Preferably, R¹ is derived from a primary amine selected from the group consisting of primary amines of animal origin with 12-18 carbon atoms and a primary amine of plant origin, C18H37N.

Preferably, the aliphatic diamine is ethylenediamine.

Preferably, the molar ratio of the base oiksoap type thickener :polyurea type thickener is 2:1 :2.

Moreover and preferably, the plastic grease composition according to the invention additionally contains enriching agents selected from the group including: anti-corrosion, anti-oxidation, antiaging, anti-wear, friction reducing and high pressure resistance improving agents.

Another object of the invention is a method of manufacturing a plastic grease composition according to the invention, characterized in that it includes the following steps: a. a base oil selected from mineral oil from crude oil distillation, paraffinic oil, naphthenic oil, recycled oil, hydrocarbon oil containing lubricating oils, synthetic oil, and mixtures thereof is introduced into a reactor equipped with a stirrer at a temperature of 15-40°C; b. then a primary amine of 12-18 carbon atoms and a secondary amine of 2-6 carbon atoms are added successively to the base oil in a molar ratio of 2:1, and stirring with heating to 40-70°C is performed until a homogeneous mixture of amines is obtained; c. then diisocyanate is added under normal pressure at a molar ratio of diisocyanate: primary amine secondary amine of 2:2:1; d. after mixing, a hydroxy acid or hydroxy acid ester containing from 9-36 carbon atoms, or a mixture thereof is added in an amount of 4-6% by weight of the total weight of the grease composition, and after dissolving it in the polymer, a mixture of lime in base oil is added under normal pressure; e. the reactor is heated until the temperature inside the reactor reaches 100-120°C; f. after dehydration, base oil is added to the reactor in an amount of 25-30% by total weight of the grease composition and heated to 110-130°C until the reactor contents are thickened; g. when the thickening is achieved, the mixture is cooled with base oil in the amount of 30- 40% by total weight of the grease composition; h. optionally, enriching agents selected from the group including: anticorrosive, antioxidant, anti-aging, anti-wear, friction-reducing and high-pressure resistance agents are added to the obtained grease; i. the resulting grease is subjected to homogenization and degassing.

Preferably, the diisocyanate is selected from the group including toluene diisocyanate and diphenylmethylene 4,4'-diisocyanate.

Preferably, the hydroxy acid or hydroxy acid ester containing from 9-36 carbon atoms is selected from the group including 12-hydroxystearic acid, hydrogenated ricinoleic acid, fatty acid of animal or vegetable origin containing from 9-36 carbon atoms, salicylic acid, hydroxybenzenesulfonic acid.

Preferably, the primary amine is selected from the group including primary amines of animal origin with 12-18 carbon atoms and a primary amine of plant origin C18H37N.

Preferably, the aliphatic diamine is ethylenediamine.

The advantage of the plastic grease composition according to the invention is the reduction of the total content of thickeners to a level of 7 to 9% while maintaining the desired properties and parameters of the grease. In addition, the developed manufacturing method includes the preparation of both the polyurea-type thickener and the soap-type thickener in situ at a lower temperature (110°C) and in normal atmospheric pressure conditions, without the need to raise the pressure and use an autoclave. This makes the developed technology for the production of a plastic grease composition according to the invention considerably cheaper and less complicated than the methods previously known in the state of the art. The production of the grease composition according to the invention is carried out in conventional equipment without any additional modifications, i.e. only a mixer with a heating jacket and a frame mixer is necessary.

The plastic grease obtained by the method according to the invention has a dropping point according to ASTM above 250°C and mixes in all proportions with other greases without altering the characteristics and side effects. Embodiments

Example 1

Production of 1 ton of plastic grease

300 kg of naphthenic base oil with a viscosity of 100 cst at 40°C is introduced into a reactor equipped with a frame mixer.

Then to the oil is successively added in molar proportions:

- primary amine of animal origin with 12-18 carbon atoms - 23.2 kg;

- secondary amine - ethylenediamine 99.9% - 2.4 kg.

While stirring, the contents of the reactor are heated to 60-70°C to obtain a homogeneous mixture of amines. Then, 14.4 kg of toluene diisocyanate (TDI) is added.

The reaction occurs immediately under normal pressure.

After mixing, 40 kg of 12-hydroxy stearic acid (12 HSA) is added and after its dissolution in the polymer, a mixture of 6 kg of lime in 40 kg of naphthenic base oil with a viscosity of 100 cst at 40°C is added.

The reactor is heated to achieve a temperature of 100-120°C inside the reactor.

The saponification reaction occurs under normal pressure with the release of water.

After dehydration, 250 kg of base oil with a viscosity of 100 cst at 40°C is added to the reactor and heated to 110-130°C until the reactor contents are thickened.

When the thickening is achieved, the mixture is cooled with base oil of 100 cst viscosity at 40°C in the amount of 300 kg.

To the resulting grease are added enriching agents, such as:

- anticorrosive - sorbitol monooleate type - 10 kg;

- antioxidant - phenolic or alpha-naphthylamine type - 15 kg;

- anti-wear - zinc dialkyldithiophosphate (ZDDP) type - 5 kg.

The obtained grease is subjected to homogenization and degassing.

The obtained grease has the following characteristics:

- Penetration after 60 cycles ASTM D217 mm/10 270-290

- Dripping temperature ASTM D2265 260°C.

- Oil release (SDM 433) 1.2%.

- Faux Brinell effect 2.5 mg

Example 2

Production of 1 ton - Grease produced on the basis of synthetic oil of PAO (poly-alpha-olefin) type

300 kg of synthetic oil (PAO) with kinematic viscosity of 66 cst at 40°C is introduced into a reactor equipped with a frame mixer. Then, as in example 1, the mixture of amines and toluene diisocyanate is added to the oil successively in molar proportions of 2:1:2, i.e.: primary amine of the animal origin 23.2 kg, secondary amine - ethylenediamine 2.4 kg and toluene diisocyanate 14.4 kg.

The reaction occurs immediately and under normal pressure.

After obtaining the tetra urea polymer, 40 kg of 12-hydroxystearic acid (12 HSA) is added to the mixture, and after dissolving it at about 60-70°C, a mixture of 6 kg of lime in 40 kg of PAO is added.

The reactor is heated to reach a temperature of 100-120°C inside the reactor. The saponification reaction occurs under normal pressure with the release of water. After dehydration, 250 kg of PAO is added to the reactor and the reactor is heated to 110-120°C until the mixture in the reactor thickens.

The mixture is then cooled with 300 kg of PAO. To the precipitated grease are added enriching agents, such as:

- anticorrosive -sorbitol monooleate - 10 kg;

-antioxidant - phenolic or amine type (alpha-naphthylamine) - 15 kg;

- anti-wear - zinc dialkyldithiophosphate (ZDDP) type - 5 kg.

The grease thus obtained is subjected to homogenization and degassing, resulting in the following characteristics:

- Consistency according to NLGI 2

- Penetration ASTM D217 after 60 cycles mm/10 270- 290

- Drip temperature ASTM D 2265 minimum 250°C

- Mechanical stability after 100000 cycles mm/10 +30 pts

- Service life at 160°C ASTM D 3527-95 80 h

- Oil release SDM 433% after 24 h in 100°C 1-1.5%.

- EMKOR corrosion 0-0

- Brinell effect (50h SNR test) 2.5 mg

Example 3

Production of 1 ton of naphthenic type mineral base oil 110 cst at 40°C

Into a reactor equipped with a frame mixer is introduced, as in examples 1 and 2, in molar proportions:

- base oil 100 cst in 40°C - 300 kg;

- primary amine of vegetable origin C18H37N with a purity of 89% in the amount of 26 kg;

- ethylenediamine secondary amine of 100% purity in the amount of 2.3 kg.

While stirring, the contents of the reactor are heated to 60-70°C to obtain a homogeneous mixture of amines in proportions (9% primary amine and 91% secondary amine).

Toluene 2,4-diisocyanate (TDI) is then added in an amount of 14.70 kg. The reaction occurs immediately under normal pressure.

After mixing and obtaining a tetra urea polymer, 40 kg of 12-hydroxy stearic acid (12 HSA) is added and after dissolving it in the polymer/base oil mixture, a mixture of 6 kg of lime in 40 kg of base oil is added.

The reactor is heated to reach an internal temperature of 100-120°C.

After dehydration, 250 kg of base oil is added to the reactor and heated to a temperature of 110- 130°C until the reactor contents are thickened.

After the mixture is thickened, the contents are cooled with 300 kg of base oil. To the resulting grease are added enriching agents, such as:

- anticorrosive - sorbitol monooleate - 10 kg;

- antioxidant - phenolic or amine type (alpha-naphthylamine) - 15 kg;

- anti-wear - zinc dialkyldithiofostorate (ZDDP) type - 5 kg,

The resulting grease is subjected to homogenization and degassing.

The grease has the following characteristics:

- Consistency according to NLGI 2

- Penetration ASTM D217 after 60 cycles mm/10 270-280

- Drip temperature ASTM D 566 minimum 250°C

- Oil release according to SDM 433 after 24 h at 100 °C 1 - 1.5 %.

- Faux Brinell effect 2.5 mg

- EMC OR corrosion 0-0

- Mechanical stability after 100,000 cycles mm/10 +30 - 40 pt.

- Life span at 160 C ASTM D 3527-95 80h

- Shell Roller Test lOOh at 66C 2 g

Example 4 Production of 1 ton of grease with reduced polymer amount

As in example 1, 2, 3, into the reactor with 300 kg of naphthenic type base oil - 100 cst at 40°C is successively introduced in molar proportions 2: 1 :2:

- animal origin primary amine - 11.6 kg;

- ethylenediamine secondary amine - 1.2 kg;

- toluene diisocyanate (TDI) - 7.2 kg.

The reaction occurs immediately and under normal pressure.

To the resulting tetra urea polymer, 60 kg of 12-hydroxy stearic acid (12 HSA) is added and then a mixture of 9 kg of lime in 50 kg of base oil is added.

The reactor is heated as in example 1 under normal pressure. The reaction occurs with the release of water. After dehydration, 250 kg of base oil is added to the reactor with heating to 110-120°C until the mixture is thickened in the reactor.

The mixture is then cooled with 300 kg of base oil.

To the resulting grease are added enriching agents, such as:

- anticorrosive - sorbitol monooleate - 10 kg;

- antioxidant - phenolic or amine (alpha-naphthylamine) type - 15 kg;

- anti-wear - zinc dialkyldithiofostorate (ZDDP) type - 5 kg.

The resulting grease is subjected to homogenization and degassing, as a result of which the obtained grease has the following characteristics:

- penetration ASTM D217 after 60 cycles mm/10 275

- dripping temperature ASTM D 566 205°C

- oil release according to SDM 433 after 24h at 100°C 1.2%.

The effect of the reduced amount of tetramer polymer is a significant drop in the drip temperature.

Example 5 - Production of 1 ton of grease with tetraurea and calcium soap of hydrogenated castor oil

As in the previous examples, into the reactor with 300 kg of naphthenic base oil with a viscosity of 100 cst, is successively introduced, at 40°C, in molar proportions:

- primary amine of animal origin in the amount of 23.2 kg;

- ethylenediamine secondary amine - 2.4 kg;

- toluene diisocyanate (TDI) - 14 4kg.

After obtaining the tetra urea polymer as in the previous examples, 50 kg of hydrogenated castor oil is added to its mixture and after dissolving it at 70°C, a mixture of 8 kg of lime in 40 kg of base oil is introduced.

The reactor contents are heated to 100-120°C.

After the saponification reaction is complete, while adding 250 kg of base oil, the reactor is continuously heated to 100-120°C until the mixture thickens.

The mixture is then cooled with 300 kg of base oil.

As in previous production examples, enriching agents are added:

- anticorrosive - sorbitol monooleate - 10 kg;

- antioxidant - phenolic or amine (alpha-naphthylamine) type - 15 kg;

- anti-wear - zinc dialkyldithiofostorate (ZDDP) type - 5 kg.

The resulting grease is subjected to homogenization and degassing.

The produced grease has the following characteristics:

- penetration according to ASTM D217 after 60 cycles mm/10 275

- dropping temperature according to ASTM D 566 265°C - oil release according to SDM 433 24h in 100°C 1.2%.

Example 6 Production of 1 ton of tetraurea-based plastic grease with MDI - diphenylmethylene 4,4'-diisocyanate

Into a reactor with 300 kg of naphthenic-type mineral base oil with a viscosity of 100 cst at 40°C, is successively added in molar proportions of 2: 1:2:

- animal origin primary amine - 22.4 kg;

- secondary amine - ethylenediamine - 2.4 kg;

- diphenylmethylene 4,4'-diisocyanate (MDI) - 20 kg.

The reaction occurs at 60-70°C under normal pressure.

After obtaining the tetraurea, 40 kg of 12 hydroxystearic acid is added, and after its dissolution, a mixture of 6 kg of lime in 40 kg of base oil is added while heating the reactor to a temperature of 100-120°C .

After the saponification reaction, the separation of water, and the addition of 250 kg of base oil, the mixture is continuously heated until the reactor contents are thickened and then the mixture is cooled with 300 kg of base oil.

Then, as in the previous examples, enriching agents are added:

- anticorrosive - sorbitol monooleate - 10 kg;

- antioxidant - phenolic or amine (alpha-naphthylamine) type - 15 kg;

- anti-wear - zinc dialkyldithiofostorate (ZDDP) type - 5 kg; and the grease is subjected to homogenization and degassing.

The resulting grease has the following characteristics:

- penetration according to ASTM D217 after 60 cycles in mm/10 258

- dripping temperature according to ASTM D 566 258°C

- oil release according to SDM 433 24h in 100°C 1.4 %.

- corrosion EMCOR 0-0

The plastic grease according to the invention is a multipurpose grease that can be used in any case where the use of other oil-type agents is impossible in the temperature range from -40°C to 200°C.

Claims

1. A plastic grease composition comprising:

R¹ is derived from a primary amine containing from 12-18 carbon atoms;

R" is from an aliphatic or aromatic diamine containing from 2-16 carbon atoms;

Ar stands for aromatic hydrocarbon containing from 6-20 carbon atoms; n is between 2 and 20.

2. The plastic grease composition according to claim 1, characterized in that R is derived from 12- hydroxystearic acid, hydrogenated ricinoleic acid, fatty acid of animal or vegetable origin containing from 9-36 carbon atoms, salicylic acid, hydroxybenzenesulfonic acid.

3. The plastic grease composition according to claim 1, characterized in that R¹ is derived from a primary amine selected from the group including primary amines of animal origin with 12-18 carbon atoms and a primary amine of vegetable origin C18H37N.

4. The plastic grease composition according to claim 1, characterized in that the aliphatic diamine is ethylenediamine.

5. The plastic grease composition according to claim 1, characterized in that the molar ratio of base oiksoap type thickenerpolyurea type thickener is 2: 1 :2.

6. The plastic grease composition according to any of the claims 1 to 5, characterized in that it additionally contains enriching agents selected from the group including: anticorrosive, antioxidant, anti-aging, anti-wear, friction-reducing and high-pressure resistance enhancing agents.

7. A method of producing the plastic grease composition as defined by any of the claims 1 to 6, characterized in that it includes the following steps: a. into a reactor equipped with a stirrer is introduced, at a temperature of 15-40°C, a base oil selected from a mineral oil from the from the distillation of crude oil, paraffin oil, naphthenic oil, recycled oil, hydrocarbon oil containing lubricating oils, synthetic oil, and their mixtures; b. then, a primary amine of 12-18 carbon atoms and a secondary amine of 2-6 carbon atoms are added successively to the base oil in a molar ratio of 2:1, and stirring with heating to 40-70°C is performed until a homogeneous mixture of amines is obtained; c. then, diisocyanate is added under normal pressure at a molar ratio of diisocyanate primary amine: secondary amine of 2:2:1; d. after mixing, a hydroxy acid or hydroxy acid ester containing from 9-36 carbon atoms, or a mixture thereof, is added in an amount of 4-6% by weight of the total weight of the grease composition, and after dissolving it in the polymer, a mixture of lime in base oil is added under normal pressure; e. the reactor is heated until the temperature inside the reactor reaches 100-120°C; f. after dehydration, base oil is added to the reactor at a rate of 25-30% by total weight of the grease composition and heated to 110-130°C until the reactor contents are thickened; g. when the thickening is achieved, the mixture is cooled with base oil in the amount of 30- 40% by total weight of the grease composition; h. optionally, enriching agents selected from the group including: anticorrosive, antioxidant, anti-aging, anti-wear, friction-reducing and high-pressure resistance agents are added to the obtained grease; i. the resulting grease is subjected to homogenization and degassing.

8. The method according to claim 7, characterized in that the diisocyanate is selected from the group including toluene diisocyanate and diphenylmethylene 4,4'-diisocyanate.

9. The method according to claim 7, characterized in that the hydroxy acid or ester of a hydroxy acid containing from 9-36 carbon atoms is selected from the group comprising 12-hydroxystearic acid, hydrogenated ricinoleic acid, fatty acid of animal or vegetable origin containing from 9-36 carbon atoms, salicylic acid, hydroxybenzenesulfonic acid.

10. The method according to claim 7, characterized in that the primary amine is selected from a group including primary amines of animal origin with 12-18 carbon atoms and a primary amine of plant origin C18H37N.

11. The method according to claim 7, characterized in that the aliphatic diamine is ethylenediamine.