DE1242570B - Organopolysiloxane-containing antifoams - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

BOId

German class: 12 e-3/11

Number: 1 242 570

File number: S 71728IV c / 12 e

Filing date: December 19, 1960

Open date: June 22, 1967

The antifoams known up to now based on organosilicon compounds are in generally in the form of thick liquids or pastes obtained by finely dividing them Adding fillers such as silica to organosilicon oils of varying viscosity. These products can can also be diluted with organic solvents or used in the form of aqueous emulsions, because in this form they are more easily dispersible in the media to be treated and also not are flammable.

As the emulsifying agent, there have heretofore been those of the cationic type, anionic type or nonionic type such as polyethylene glycol stearate or Polycondensation derivatives of ethylene oxide, as additional stabilizers, methyl celluloses and polyvinyl alcohols, used.

It can also be seen from the subject matter of patent specification 1110 862 that aqueous organopolysiloxane emulsions are used with improved quality if a mixture of organopolysiloxane oil and Before emulsifying, the silica is heated to a temperature between 100 and 250 ° C for a few hours.

It has now been found that aqueous emulsions have good anti-foam properties and can be used in media of any pH value and, moreover, are completely free of toxicity and therefore usable in the field of the food industries and further enable longer storage when used as aqueous emulsions 1 to 60 %, based on the total weight of the emulsion, of a dimethylpolysiloxane oil with a CH ₃ / Si ratio between 1.9 and 2.1, a viscosity between 10 and 10,000 centistokes at 25 ° C., 0.1 to 10% of a fine divided silica, the particles of which have a mean diameter below 50 ΐημ and whose surface is at least 50 m ² / g, 0.2 to 10% of a polyvinyl alcohol as a 4% aqueous solution with a viscosity between 20 and 50 centipoise at 25 ° C, and a saponification number between 25 and 200, is used. The polyvinyl alcohols are used here alone, without the addition of emulsifiers.

As dimethylpolysiloxane are products whose CH ₃ / Si ratio is between 1.9 and 2.1, and the viscosity of 10 to 10,000 centistokes at 25 ⁰ C, preferably 100 to 1000 centistokes is, used. These compounds, whose structure can be linear or cyclic, are prepared in a known manner.

The silicic acids used are finely divided products, the particles of which have an average diameter below those containing organopolysiloxane Antifoam agents

Applicant:

Rhone-Poulenc. S. A., Paris

Representative:

Dr. F. Zumstein, Dr. E. Assmann

and Dr. R. Koenigsberger, patent attorneys,

Munich 2, Bräuhausstr. 4th

Named as inventor:

Raoul Michel JoIy, Lyon (France)

Claimed priority:

France of February 25, 1960 (819 594)

half 1000 millimicrons, preferably below 50 millimicrons, and the surface area is at least 50 m ² / g, is used. They are made either by precipitation or by burning silicon tetrachloride or various organosilicon compounds.

The polyvinyl alcohols used are those whose viscosity in 4% aqueous solution is between 20 and 50, preferably 25 and 35 centipoise at 20 ° C and their saponification number between 25 and 200, preferably 100 and 150. Such polyvinyl alcohols lead to very stable and siloxane emulsions that are very effective in terms of their anti-foaming effect.

The products of lower or higher viscosity than those defined above generally result in emulsions that are poorly held and, moreover, the emulsions obtained are difficult to dilute.
The procedure for preparing the emulsions used according to the invention is as follows: The silica is introduced into the selected dimethylpolysiloxane oil, for example with the aid of a ball mill, the ratio of the two components depending in particular on the viscosity of the oil used. The slurry thus obtained is then heated for a few hours to a temperature between 100 and 250 ° C. in an apparatus equipped with a stirrer. The duration of the thermal treatment depends on the temperature at which one works. The higher the temperature, the shorter it is. In general, less than 24 hours is sufficient. A treatment on the order of magnitude

709 607/467

16 hours at 200 ° C is well suited. Put in the so treated and then cooled paste then gradually with stirring the polyvinyl alcohol in the form of an aqueous solution in the All or part of the water intended for the composition. One adds if necessary the amount of water and put the whole thing in a colloid mill.

No patent protection is claimed here for the production of the emulsions.

The emulsions used according to the invention are in both an acidic and an alkaline medium effective. Their antifoam effect can be measured by putting a stream of air into an aqueous one Solution that conducts a foaming product and a small amount of the antifoam to be tested (on the order of 1 part / 1000 to 1 part / 1000,000). The introduction of air into the in A graduated test glass introduced liquid causes the formation of foam, the height of which is in the The test glass increases as the effectiveness of the agent decreases. The time after which foam passes over the edge of the test glass is a measure of the effectiveness of the Product.

In practice, a test glass with a height of 40 cm and a 6 cm diameter used. The solution of the foaming product initially took a height of 18 mm in the test glass. The foaming solution was used for the experiment in acidic medium prepared by adding 5 g of a foaming agent based on sodium lauryl sulfate and 15 g of acetic acid to 11 distilled water were added, while for the experiment in alkaline solution the Solution by adding 1.5 g of oleic acid to 15 g of sodium hydroxide and then topping up the Whole with water on 11 was made.

The stability of the antifoam emulsions used according to the invention can be tested by shaking for two hours on a shaker (frequency 150 to and fro / minute) and by storage on the one hand for three hours at -2O ⁰ C and on the other hand for 7 days at + 50 ° C.

It is found so that the emulsions prepared using polyvinyl better stability against shaking and extreme storage temperatures have (-20 ⁰ C and +50 ⁰ C) than the usual using emulsifying agents, such as Fettsäureestern and multivalent alcohols obtained analog products.

The following example explains the invention without restricting it. The parts are parts by weight.

example

950 parts of a dimethylpolysiloxane oil with a viscosity of 100 centistokes at 25 ° C and 50 parts silica made by incineration (mean diameter of the particles 15 millimicrons) and grind for 6 hours. After standing, the mill is emptied and heated the product obtained for 16 hours in an apparatus equipped with a stirrer 200 ° C. Then it is allowed to cool.

300 parts of the mixture thus obtained are introduced into an apparatus equipped with a stirrer and 384 parts of a solution containing 10% of a polyvinyl alcohol which has the following characteristics are allowed to flow in over the course of 1 hour: saponification number: 115; Viscosity at 20 ° C of a 4% aqueous solution: 26.3 centipoise. The temperature rises in the course of the flow from 21 to 24 ° C. Towards the end of the flow, the mass becomes thick. They are made liquid by adding 316 parts of water. The mixture is then stirred for 15 minutes and then the liquid obtained is placed in a colloid mill. An oil-in-water emulsion is then obtained, with which the experiments described above are carried out. It is not by dilution with water or by -dreistündiges Store at - destroyed 20 ⁰ C nor seven-day heating at +50 ⁰ C. The results of the tests for antifoam effectiveness and stability against shaking are compiled in the table below.

For comparison purposes, the same determinations were carried out with an emulsion in which the polyvinyl alcohol was replaced by 6% polyoxyethylene stearate and 8% sorbitan tristearate.

Anti-foam effect alkaline Anti-foam effect 7 days Antifoam effect in 7 days Stability against after 48 hours at 20 ° C medium in an acidic medium at + 5O ⁰ C alkaline medium at + 5O ⁰ C Shake (2 hours Emulsions sour Minutes 3 hours Minutes 3 hours Minutes in a shake medium at -20 ° C at -2O ⁰ C apparatus; frequency Minutes 33 Minutes > 60 Minutes 26th 150 per minute) With polyvinyl alcohol 100 75 22nd unchanged Appearance With polyoxyethylene lenstearate and Sorbitan tristea 20th > 50 26th advice received product 78 54 21 Separation in two phases, a solid and a liquid one

Claims (1)

Claim: Use of aqueous emulsions, from 1 to 60%, based on the total weight of the emulsion, of a dimethylpolysiloxane oil with a CH ₃ / Si ratio between 1.9 and 2.1, a viscosity between 10 and 10,000 centistokes at 25 ° C, 0.1 to 10% of a finely divided silica 5 6 acid, the particles of which have an average diameter of 25 ° C, and a saponification number between have knives below 50 πΐμ and their upper 25 and 200, as antifoam agents. area is at least 50 m ² / g, 0.2 to 10% of a polyvinyl alcohol as a 4% aqueous solution. with a viscosity between 20 and 50 centipoise 5 German Auslegeschrift No. 1067 003. 709 607/467 6.67 © Bundesdruckerei Berlin