DE1051505B - Process for polymerizing vinyl chloride in an aqueous emulsion - Google Patents

Description

The invention relates to a process for polymerizing vinyl chloride in aqueous emulsion, if desired together with other olefinically unsaturated compounds, such as vinylidene chloride, Vinyl acetate, acrylic acid and methacrylic acid esters.

It is known to polymerize vinyl chloride in emulsion using water-soluble catalysts, such as potassium persulfate, and fatty acid soaps as an emulsifier. When H ₂ O _{2 is used} as a catalyst, sulfonates have been used as emulsifiers. Although the polyvinyl chloride thus obtained had good mechanical properties, the electrical properties were not entirely satisfactory. The polyvinyl chloride obtained heretofore by emulsion polymerization has therefore only been of limited use for use as an electrical insulating material.

It has now been found that polyvinyl chloride can be used with substantially improved electrical and paste forming properties by polymerizing vinyl chloride in aqueous emulsion, either alone or together with other olefinically unsaturated compounds obtained if hydrogen peroxide is introduced into the emulsion which is a p _H - Has a value between 8.5 and 11 and contains a carboxylic acid salt with 8 to 22, preferably 10 to 14, carbon atoms as emulsifier. The process is preferably carried out continuously, ie the polymerization is carried out in a reaction space to which water, emulsifier and monomer (monomers) are continuously fed and from which part of the reaction mixture is continuously withdrawn, the addition and discharge being measured in such a way that the Composition of the reaction mixture remains essentially the same. In such a procedure, the hydrogen peroxide is usually also fed in continuously. A very useful embodiment of the continuous process consists in introducing the monomer into the reaction space in the form of an aqueous emulsion. The continuous process can also be carried out, for example, using the so-called "Seppol process", in which a stream of monomeric droplets is passed through the aqueous phase. As is known, the emulsion polymerization of vinyl chloride is carried out at a temperature which is usually between 30 and 85 ° C, and preferably between about 35 and 55 ° C.

It is very surprising that the invention from 8.5 to 11 and is application of an emulsion, the _pH value preferably in accordance with 9.0 to 9.5, the hydrogen peroxide the polymerisation

procedure

for polymerizing vinyl chloride
in aqueous emulsion

Applicant:

NV De Bataafsche Petroleum
Maatschappij, The Hague

Representative: Dr. K. Schwarzhans, patent attorney,
Munich 19, Romanplatz 9

Claimed priority:
Netherlands 19 April 1955

Arnold Noorduyn and Adolf Bier,

Rotterdam (Netherlands),
have been named as inventors

sation can still be initiated, since hydrogen peroxide is not stable in such an alkaline medium. The aforementioned limits for the pH value of the aqueous emulsion are determined on the one hand by the fact that in a weak alkaline medium, e.g. Example, with a _pH value below 8.5, the emulsifiers used, such as Ammoniumlaureat, insufficient Emulgierungsvermögen possess characterized on the other hand, that in a too strongly alkaline medium, eg. B. over a p _H value of 11, the hydrogen peroxide breaks down before it can exert the initiating effect. The hydrogen peroxide is introduced into the emulsion in the form of an aqueous solution. The concentration of this solution is preferably between 0.1 and 15%. The carboxylic acid salts with 8 to 22 carbon atoms to be used according to the invention are preferably derived from saturated or unsaturated fatty acids, such as from lauric acid, myristic acid, oleic acid, stearic acid, linoleic acid, palmitic acid. Ammonium salts of saturated fatty acids, especially ammonium laureate, are preferred.

The amount of emulsifier used can vary widely. Generally 0.1 to 2% is in the contain aqueous phase. If ammonium laureate is used, one will suffice in most cases Amount of about 1%, calculated on the aqueous phase.

809 767/531

The polyvinyl chloride can be separated from the resulting latex by coagulation, preferably with organic or inorganic acids such as nitric acid, hydrochloric acid, formic acid. After washing the, if necessary, carried out depending on the coagulants used Coagulates, the polyvinyl chloride can be further processed, for. B. with a solution which a alkaline reaction results, such as caustic soda, sodium carbonate, ammonium hydroxide or amines, z. B. Diethanolamine. After washing the coagulate this is preferably heated and placed in a Screw press introduced, which greatly reduces the water content, e.g. B. on a salary less than 5%. The resulting sintered product is then finely ground. It it was found that the polymer obtained in this way has excellent electrical properties.

When the latex is dried by spraying it in hot air, preferably at a temperature of about 140 to 160 ° C., the polymer obtained in this way has excellent paste-forming properties. If ammonium laurate is used as the emulsifier, this compound is decomposed at this temperature, NH _{3 being} removed and some of the fatty acid formed being further decomposed. When used in plastisols (ie dispersions of, for example, polyvinyl chloride in plasticizers), these retain the desired viscosity for a long time.

Examples of plasticizers suitable for this purpose are dibutyl phthalate, tricresyl phosphate and Dioctyl phthalate.

example 1

2.5 kg of vinyl chloride, 0.75 l of a 0.13% strength hydrogen peroxide solution, 0.7 l of a 15% strength aqueous ammonium laurate solution and 5.5 l (oxygen-free) water were introduced every hour into a reaction vessel equipped with a stirrer. The emulsion obtained had a _pH value of 9. The polymerization was carried out at at 51 ° C and a pressure of 6.6 to 6.8. 2.1 kg of latex were withdrawn every hour. This latex contained about 20% by weight polyvinyl chloride.

In order to separate off the polyvinyl chloride, the latex formed was diluted with water until the concentration of the polymer in the latex was 10 ¹⁰ / o. Thereupon 40 milliequivalents of formic acid were added to 1000 g of the thus diluted latex, whereby the _pH value decreased to third Then, a ³ cm lOVoigen sodium hydroxide solution added to 40 ·, increased whereby the _pH value in the ninth The obtained coagulum, which was washed with water and centrifuged, was then heated and fed into an oil press type screw press. The product exiting the press was finely ground in a hammer mill and then a pin mill. The finely ground product was adjusted to a particle size of less than 0.050 mm by air sifting, the coarser particles separated off being passed through the grinding device once more. The product obtained had an electrical resistance of 250 · 10 ¹¹ ohm / cm.

When potassium laurate was used as an emulsifier in the process described above, the final product was found to have an electrical resistance of 150 x 10 ¹¹ ohms / cm.

Example 2

In the manner described in Example 1, using ammonium laurate as an emulsifier a latex containing about 20 weight percent polyvinyl chloride was prepared. With the help of a with The compressed air sprayer was the latex in hot air at a temperature between and 160 ° C sprayed.

The powder obtained was suspended in dioctyl phthalate, with 80 parts of dioctyl phthalate 100 parts of polyvinyl chloride were used. At room temperature, the plastisol obtained had a Viscosity of 50 poise which increased to 54 poise after the plastisol had stood for 14 days.

If the polyvinyl chloride was made using potassium laurate as an emulsifier, so had a plastisol containing 80 parts of dioctyl phthalate per 100 parts of polyvinyl chloride at room temperature a viscosity of 150 poise. This value remained unchanged when the plastisol was left to stand for 14 days.

Claims (6)

Patent claims: 1. A process for polymerizing vinyl chloride in aqueous emulsion, either alone or together with other olefinically unsaturated compounds, in the presence of hydrogen peroxide as a catalyst, characterized in that adjusting a _pH value from 8.5 to 11 and in the emulsion as a Emulsifier a carboxylic acid salt with 8 to 22 carbon atoms is used. 2. The method according to claim 1, characterized in that it is carried out continuously. 3. The method of claim 1 or 2, characterized in that the _pH value of the emulsion is from 9 to 9.5. 4. The method according to any one of claims 1 to 3, characterized in that an ammonium salt a fatty acid, especially ammonium laurate, is used as an emulsifier. 5. The method according to any one of claims 1 to 4, characterized in that after acidification and washing the latex, the coagulum obtained is heated and passed through a screw press will. 6. The method according to any one of claims 1 to 4, characterized in that the latex obtained is dried by spraying. Considered publications:
German patent specification No. 749 586.