DD213945A1 - FOAM INHIBITORS FOR LUBRICATING OILS ON MINERALOELBASIS -II- - Google Patents

Abstract

The invention relates to foam inhibitors for mineral oil-based lubricating oils for use in, in particular, transmission, hydraulic, turbine, engine and metalworking oils. The aim of the invention is the cost-effective provision of foam inhibitors which prevent or reduce the surface foam formation and at the same time the Luftabgabevermöegen the oils as little as possible deteriorate and are hydrolytically stable. The foam inhibitors according to the invention consist of a compound or of a mixture of compounds of the general structure having an average molecular weight of from 10,000 to 20,000 g.mol-1, a ratio m: n of from 1: 1 to 1: 8 and a ratio p: q to 1 : 2 to 2: 1 and are added to alloyed and unalloyed lubricating oils in a concentration of 0.001 to 0.01 mass%.

Description

22, II. 1983

Title of the invention.

Foam inhibitors for mineral oil lubricating oils Field of application of the invention

The invention relates to foam inhibitors for mineral oil based alloyed and unalloyed lubricating oils for use in, in particular, transmission, hydraulic, turbine, engine TO and metalworking oils.

Characteristic of the known technical solutions

It is known to add mineral oil based lubricating oils, especially gear, hydraulic, turbine, engine and metalworking oils, foam inhibitors to prevent or reduce the formation of surface foam which deleteriously affects the operation of aggregates, machinery and equipment. 20

As foam inhibitors, almost exclusively polyalkylsiloxanes, preferably polymethylsiloxanes, are used commercially. In the application of polyalkylsiloxane foam inhibitors, the air release capacity of unalloyed and alloyed lubricating oils, depending on the degree of alloying, deteriorates to some extent to a considerable extent. However, a reduced air release capacity of the respective lubricating oils jeopardizes the technical reliability and operational reliability.

Safety, in particular, of such units that operate with high oil circulation rates and in which the oil in the oil tank little time left for air separation, such as gears, hydraulic systems, turbines, motors and machinery for metalworking · CLAJTOlT u. For this reason, a * advise against the use of polyalkylsilozanes in turbine oils.

It is also known, unspecified in the literature polyester or polyacrylates as Schauminhi-. , Although these compounds have an adverse effect on the air-removing capacity of the oils compared with the polyalkylsilozanes, they also generally cause an increase in the propellability of the air-releasing agent. HUBMAKIT and PASS as well as EQIHSR show in this connection that no foam inhibitors have become known which improve the air release capacity of mineral oil based lubricating oils.

Moreover, the polyester- or polyacrylate-based inhibitors are less effective than polyalkylsiloxanes in preventing surface foam formation and therefore must be used in much higher concentrations. Furthermore, undesirable IT effects may occur through interactions with other alloying constituents of the oil which reduce the effectiveness of the foam inhibitor.

The compounds of the silicone-polyglycol copolymer type listed in US Pat. No. 3,951,832 are likewise usable as foam inhibitors. A disadvantage for practical use is that the compounds described are unstable to hydrolysis and, moreover, have limited availability at high cost ,

Object of the invention

The object of the invention is to provide foam inhibitors for lubricating oils based on mineral oil in a cost-effective and sufficiently available manner, which prevent or reduce surface foam formation and at the same time deteriorate the air release capacity of the oils as little as possible and are hydrolytically stable.

Explanation of the essence of the invention

The object of the invention is to find suitable organic foam inhibitors which counteract the formation and stabilization of surface foam and, on the same side, influence the deposition of the air dispersed in mineral lubricating oils as little as possible.

Surprisingly, it has been found that the object is achieved with foam inhibitors based on polyalkylsiloxane polyether copolymers which consist of a compound or of a mixture of compounds of the general structure

GH ₃

Si-OI

GH ₂

CH ₂ CHO

0- (CH ₂ )

^ -! OGH ₀ -

Yourself.,)

with an average molecular weight of 10,000 to 20,000 g ·

-1

mol, a silisium content of 5 to 15% by mass, a dimethylsiloxane content of 15 to 30% by mass, a polyether content of 70 to 85% by mass, of a polyether component of the type of an ethylene-propylene copolymer, a

average molecular weight of the siloxane block from 2,000 to 6,000 g. mol of an average molar mass of a polyether chain of from 1000 to 3000 g.mol "*, a ratio m: η such as 1: 1 to 1: 8 and a ratio ρ: q such as 1: 2 to 2: 1.

The foam inhibitors according to the invention are admixed to mineral oil-based alloyed or unalloyed lubricating oils in a concentration of 0.001 to 0.01% by mass so as to form a dispersion with the oil in finely divided form. The fine distribution of the foam inhibitor in the oil takes place in a known manner by mechanical means, for example by intensive stirring, vigorous shaking, co-grinding of oil and foam inhibitor in a colloid mill or by means of ultrasound. Conveniently, stock solutions are first prepared with a low-viscosity mineral oil, the weräen then added in the desired concentration of the 'respective lubricating oil "The Einsatz'der foam inhibitors of the invention based on Polyalkylsilozan polyether Copolyrneren in lubricating oils based on mineral oil leads to a considerable reduction in the surface foam formation, wherein Furthermore, the Schauininhibitoren invention have the advantageous property of being hydrolytically stable, since the linking of Polyosyalkylenkatten with the silicon atoms via a hydrolysis-stable C-3i-3indung takes place · This is Of particular importance in the practical use of the foam inhibitors in mineral lubricating oils, where always with the presence of water must be expected ·

The amount of air taken up in the foaming by the mineral oil is not influenced by the foam inhibitors according to the invention in the specified concentration limits.

- 5 embodiments

The invention will be explained in more detail below with reference to some embodiments.

example 1

0.001% by mass of a technical methylsiloxane-polyether copolymer having an average molecular weight of 12,600 g.mol ", a silicon content of 8% by mass, a dimethylsiloxane content of 20% by mass, a polyether content of 80% by mass, a polyether component of Type of ethylene-propylene copolymer, an average molar mass of the silozane block of 3,000 g.mol ", an average molecular weight

- 1

mass of a polyether chain of 1500 g.mol, a ratio m: η as 1: 5 »a ratio ρ: q as 1: 1, a viscosity of 1 500 mPa · s at 20 ⁰ C and a surface tension of 25» 4 mlfai "'at 20 ⁰ G are dispersed from a stock solution in an unalloyed hydraulic oil having a viscosity of 36 mm ² s" ¹ at 50 ⁰ C with ultrasound. The stock solution is prepared using a mineral oil in the viscosity of 5 mm s at 50 ⁰ G.

Example 2

0.001% by mass of a technical methylsiloxane-polyether copolymer having an average molecular weight of 17 000 g ^β mol "*, a silicon content of 13% by mass, a dimethyl siloxane content of 22% by mass, a polyether content of 78% by mass, a polyether component of the [Dyp of an Ithy-len-propylene copolymer, an average molecular weight of

-1

Silosanblockes of 5 000 g * mol, an average molecular weight of a polyether chain of 2,000 g * mol "', a ratio m: η as 1: 7, a ratio ρ: q as 1: 1, a viscosity of 2 500 mPa · s at 20 ⁰ G and a surface tension of 22.5 ralTm at 20 G are under

the conditions mentioned in Example 1 are admixed with the unalloyed hydraulic oil listed there.

Example 3

0.01% by weight of a technical methylsiloxane-polyether copolymer having the characteristics according to Example 2 are admixed under the conditions mentioned in Example 1 to the unalloyed hydraulic oil listed there.

The test results listed in Table 1 illustrate the advantageous properties of the foam inhibitors according to the invention in comparison to a corresponding product of the prior art. As comparative

ις product was a polydimethylsiloxane with a middle

" -1

Molar mass of 60 000 g · mol and in concentrations of 0.001 and 0.01 mass% below those in the

  Example 1 in a non-alloy

2 -1

dispersed hydraulic oil with a viscosity of 36 mm s at 50 ⁰ C ·

The hydraulic oils added with the foam inhibitors according to the invention according to Examples 1 to 3 and with the comparative foam inhibitor were then investigated with regard to their air release capacity and their tendency to surface foam formation. The liveability was determined according to TGL 32 432-81 = DHT 51 566-79; the surface foam behavior of the inhibited oils was measured according to TGL 31 167-76 = AS ¹ Bi D 892-74, but using a foam blower instead of the ball frit analogously to DDT (S) 51 566-76 for the relative measurements that were sufficient here *

Table 1

Results of

qualitative

investigations

unalloyed hydraulic oil

Unalloyed hydraulic oil + foam inhibitors according to the invention correspond accordingly in accordance with Example 1 Example 2 Example 3

unalloyed hydraulic oil + foam inhibitor of the prior art (polydimethylsiloxane) 0.001 Ma. ~% 0.01 Ma. -%

Air tabgeability according to TGL 32 432-81

at 30 ° 0 in min

23

24

35

34

Surface cladding behavior according to TGL 31 167-76 300 0 0 0 0 0 Surface βchaumne i tion 25 0 0 45 0 0 at 25 ^° C. in ml 330 90 70 0 0 0 at 95 ° G in ml at 25 ° 0 to 95 0 in ml 0/285 0/20 - - 0/20 - - Surface foam stability 0/310 0/360 0/130 - - - at 25 ⁰ O in ml after ß at 90 ⁰ G in ml after s at 25 ⁰ O to 95 0 in ml after s

Claims (2)

Srfindungsanspruch Foam inhibitors for mineral oil-based lubricating oils, consisting of polyalkylsiloxane-polyether copolymers, characterized in that they consist of a compound or of a mixture of compounds of the general structure ₃ -Si-O Si-O 1 CH ₂ j CHp ί 0- (CH ₀ ) CH- OCH ^ CH q 4 9 Si CLSI (CH-J CL lim having an average molecular weight of from 10,000 to 20,000 g.mol, a silicon content of from 5 to 15% by weight, a dimethyl siloxane content of from 15 to 30% by weight, a polyether content of from 70 to 85% by weight, of a polyethylene type polyether component Propylene copolymers, having an average molar mass of the siloxane block of from 2,000 to 6,000 g.mol ", an average molar mass of a polyether chain of from 1,000 to 3,000 g.mol", a ratio m; η as 1; 1 to 1: 8 and a ratio ρ: q such as 1: 2 to 2: 1 exist. 2 · Foam inhibitors according to item 1§, characterized in that they are added in a concentration of 0.001 to 0.01 % by mass of mineral oil-based alloyed and unalloyed lubricating oils.