DE1109370B - Process for the polymerization of fluorine-containing olefins - Google Patents

Description

It is known to carry out a suspension polymerization of tetrafluoroethylene atm in an aqueous medium in the presence of inorganic or organic peroxides in the door temperature range from -30 to + 15O ⁰ C and in the pressure range of 3 to 1000th The polytetrafluoroethylene produced by this process is partly obtained as a coarse-grained or clod-like polymer, which can often only be discharged from the reaction vessels with difficulty. In addition, when working according to this process, there are often deposits on the surfaces of the autoclave which make it necessary to clean the autoclave from time to time. Finally, the mechanically removed wall coverings are unusable for further processing due to their reduced quality.

If the suspension polymerization is carried out according to the already known method, one remains Comminution of the resulting coarse polymer is unavoidable by known methods. Any mechanical Stress on the polymer, which leads to a reduction in the size of the particles, is usually associated with the enlargement and formation of a heterogeneous surface and not desirable. Strong mechanical stress on the polymer leads to the following disadvantageous properties:

1. Low bulk weight,

2. poor flowability,

3. Tendency to form spheres when drying while moving.

These difficulties can partly be caused by the special arrangement of the stirring elements in the autoclave to be overcome; d. That is, one must strive to choose the polymerization conditions so that the Polymer in statu nascendi is obtained in an even form that is as finely distributed as possible.

In the polymerization of tetrafluoroethylene from the gas phase, which takes place at the liquid-gas space interface, the individual polymer particles are reduced in size by increasing the shear forces, ie by increasing the stirring speed on the one hand and by installing suitable baffles on the other. Fast-running special stirrers, which are also built into pressure vessels, lead to the stuffing box problems known to every person skilled in the art. These problems can still be adequately solved in smaller units, but are often difficult to overcome with larger units. In addition, with high-speed stirrers, the wear on the packing material is great, time-consuming and costly maintenance is necessary and, moreover, an unavoidable process for polymerisation
of fluorine-containing olefins

Applicant:

Farbwerke Hoechst Aktiengesellschaft

formerly Master Lucius & Brüning,

Frankfurt / M., Brüningstr. 45

Dr. Klaus Weissermel, Frankfurt / M.-Unterliederbach, and Dr. Manfred Reiher, Hofheim (Taunus),

have been named as inventors

rubbed on packing or sealing material significantly impaired the quality of the polymer.

It is also known that polymers with good processing properties are obtained if the Polymerization of tetrafluoroethylene in the presence of saturated, perfluorinated solvents with a Bp <150 ° C. Since the perfluorinated solvents suitable for this are very expensive and difficult are accessible, and must be recovered as quantitatively as possible after each approach is a technical use associated with considerable costs.

It has now been found that all of the difficulties listed are largely overcome when the suspension polymerization of fluorine-containing olefins in an aqueous medium in the presence of 0.004 up to 0.0001 percent by weight, based on the aqueous phase, of perhalogenated fluorine or fluorine and chlorine containing carboxylic acids and / or their salts under the usual polymerization conditions. Among these perfluorocarboxylic acids and perfluorochlorocarboxylic acids, their use as emulsifiers the emulsion polymerization of fluorine-containing olefins is already known, perfluorooctanoic acid is particularly important well suited for the stated purpose. The carboxylic acids mentioned are preferably in the form of their Alkali or ammonium salts are used. Particularly favorable results are obtained when the acids in an amount of 0.0015 to 0.0005 percent by weight, based on the aqueous phase, can be used.

The polymerization of tetrafluoroethylene carried out by the process according to the invention leads

109 618 / 504-

3 4

to a polymer which is adjusted without difficulty from the polymerization. It is important that it can be carried and, after the usual work-up, that oxygen is excluded from products with a high bulk density and good trickle during the polymerization,
properties results. The known catalysts are suitable

However, the process according to the invention does not offer 5 organic and inorganic peroxide compounds,

only a whole series of technical polymerisation advantages in amounts of 0.001 to 0.5 percent by weight,

parts, but also leads to products that are used in relation to the monomer. Further

Processing to moldings behave more favorably than can the polymerization in the presence of

Polymers obtained after the conventional emulsion redox activators and in the presence of such metals

or suspension processes arise. io or inorganic or organic metal salts through-

While emulsion polymers are used in the compression molding process, they are in several valence levels

work and can therefore react only with great difficulty.

are to be demolded, is ^: this disadvantage with the pressure and temperature can also be in

Polytetrafluoro- produced by the present process vary within wide limits. In general, through

ethylene not to be observed; perfect release of pressure and temperature increase the polymerization

shaping is easily possible. accelerated.

The polymerization of Tetrafiuoräthylen is obtained by the known suspension process before polymers usually occur in an unfavorable particle size in reaction distribution lined with enamel. The powder is uneven and often carried out to vessels, but can also use coarse-grained, so that a mechanical 20 V4A steel or silver-lined vessels crushing becomes necessary to turn the fibrous particles.

delivers which easily clump together. In such a case, a continuous or discontinuous poly-sieving is unavoidable before processing. Here, too, merization is possible,
polymers prepared according to the invention as over 25

place as they are in the form of a fine, evenly granular description of the experiments
th powder. The flowability is excellent. For all polymerization approaches, there is hardly any risk of enamel and lump formation, an autoclave of vertical design used, which is equipped with something that can be used when filling molds and feeding stirrers and baffles. Pressure, piston extrusion advantageously makes noticeable and the temperature profile and monomer consumption are made the work process much easier. Which is determined in the registering. The stabilizer-free manner described, polymerized products delivering monomer is used. The polymerization is carried out with, moreover, moldings from a very uniform exclusion of air.
Nature. The surface of the parts leaves nothing

Recognize inhomogeneities; the density of the finished 35 example

Article is very even, and much less occurs there are presented

often mechanical defects than when using _{10Q parts by} weight of water

of conventional suspension polymer. Loading _{Q (m parts by weight of} p _he fluorooctanoic acid as

Sodium salt is particularly effective in difficult manufacturing processes

the last-mentioned advantages are beneficial. It 40 _{n 19} Orwirhtstpi'le Rm-a *
can e.g. B. shuttering foils are obtained that have a

have completely uniform structure and thereby and Tetrafiuoräthylen up to a pressure of 27 to

are less porous than those foils that can be made from roughly 30 atmospheres at 25 ^° C.

granular polymer wins. For applications then will be channeled

in the electrical sector and in the chemical 45 q 25 parts by weight of water

Technique are the very even and homogeneous _o ; _{o02 parts by weight of} potassium persulfate,

Foils because of their higher purchase _{strength QQm parts by weight of} copper sulfate with 5 crystal

and their lower permeability for liquids water CCuSO -5HO)

and gases are particularly suitable, not to mention ^{4 2}

that their mechanical properties are also better. 50 ^u _ "__. .,., ",

In the polymerization composition according to the invention, 25 parts by weight of water
drive is the ratio of liquor to monomer so to ^{0 001} parts by weight of sodium bisulfite.
choose that thorough mixing during the The polymerization begins immediately and polymerization is guaranteed. Advantageously connected with a pressure drop. As the operating pressure increases, the ratio of aqueous phase to 55 is not achieved by continuously introducing monomer phase of 1: 1, but instead carries out the further tetrafluoroethylene in the rhythm of the polymerization in the presence of 2 to 6 parts of water consumption, kept constant, the polymerization according to 1 Part monomer through. Absorption of 38 parts by weight of tetrafluoroethylene

The perfluorocarboxylic acids and perfluorochlorocarbon terminated by releasing the pressure in the autoclave. the

acids or their salts can be pre-heated with the liquor. Heat of polymerization is transferred through the cooling jacket of the

placed or removed in the course of the polymerisation- autoclave in which cold water circulates,

be dosed. It becomes a polymerization temperature of 22 to

The pH range can be varied within wide limits from e.g. B. 27 ⁰ C complied with.

2.5 to 12 can be varied and is essentially based on numerous, under the same polymerization Experiments carried out according to the catalyst and / or conditions used moved Activator systems. Preferably, the rate of polymerization is between 50 and PH value> 7 polymerized by adding 150 parts by weight of polymer per liter of liquor and Ammonia or a phosphate or borax buffer hour.

Example 2

The same polymerization conditions as in Example 1. Instead of 0.002 parts by weight of perfluorooctanoic acid 0.0015 parts by weight of perfluorooctanoic acid are used.

Example 3

The same polymerization conditions as under 1. Instead of 0.002 parts by weight of perfluorooctanoic acid 0.001 parts by weight of perfluorooctanoic acid are used.

In the polymerization experiments listed under Examples 1 to 3 a loose, fine-grained polymer is obtained which is easy to work up and is characterized by excellent workability.

For the following polymerization experiments (Examples 4 to 6), instead of perfluorooctanecarboxylic acid, a Fluorochlorocarboxylic acid used.

This was obtained by telomerization of CF ₂ = CFCl with perchloracryloyl peroxide in the presence of sulfuryl chloride and subsequent saponification of the resulting fluorochlorocarbon telomer oil with concentrated sulfuric acid to give the fluorochlorocarboxylic acid. The crude acid thus prepared was converted into the fluorochlorocarboxylic acid chloride and then fractionally distilled. The acid chloride fraction of boiling point. _50mm 135 to 15O ⁰ C was saponified. The average molecular weight of the fluorochlorocarboxylic acid obtained by saponification of the carboxylic acid chloride was found to be 450. The ammonium salt of this acid was used.

Example 4

35

40

45

It is presented

100 parts by weight of water,
0.002 parts by weight of the ammonium salt of fluorochlorocarboxylic acid, the acid chloride of which has a bp _50mm 135 to 50 ° Chat,
0.1 part by weight borax.

The autoclave is then flushed with nitrogen at 30 ° C. and evacuated. Gaseous, Destabilized tetrafluoroethylene up to a pressure of 25 atmospheres at 30 ° C initiated. Afterward are added one after the other:

0.25 parts by weight H ₂ O,
0.003 parts by weight (NH ₄ ) S ₂ O ₈ ,
0.0001 parts by weight CuCO ₄ · 5 aq
and

0.25 parts by weight H ₂ O,
0.0015 parts by weight NaHSO ₃ .

After 10 minutes, the polymerization, which is associated with a pressure drop, sets in. Through continuous Introducing pure tetrafluoroethylene in the rhythm of consumption, the operating pressure of Maintained 25 atmospheres and the polymerization after taking up 35 parts by weight of tetrafluoroethylene canceled. For this purpose, the autoclave is depressurized and the fine-grained, powdery polymer together with the polymerization liquor discharged through the bottom valve.

The polymerization temperature is 27 to 32 ° C. The space-time yield of polymer is 19 parts by weight of polymer per 100 parts by weight of liquor and hour.

Example 5

It is polymerized under the same conditions as in Example 4, except that the chlorofluorocarbons carboxylic acid (boiling point of the acid chloride at 50 mm 135-150 ⁰ C) was used in place of 0,002 parts by weight of ammonium salt now 0.0015 parts by weight of ammonium salt. Space-time yield of polymer: parts by weight of polymer per 100 parts by weight of liquor per hour.

Example 6

In this experiment, the polymerization is carried out at 20 atmospheres and 18 to 22 ° C. Instead of 0.0015 parts by weight of ammonium salt of the fluorocarboxylic acids (boiling point of the acid chloride at 50 mm from 135 to 15O ⁰ C) is used in the same chlorofluorocarbons carboxylic acid 0.001 part by weight of ammonium salt. The space-time yield of polymer is 9 parts by weight of polymer per 100 parts by weight of liquor per hour.

In the polymerization experiments listed under Examples 4 to 6 a loose, fine-grained polymer is also obtained from the autoclave can be discharged without difficulty and that thanks to its ease of processing and excellent Processability is marked.

Claims (4)

PATENT CLAIMS: 1. A process for the polymerization of fluorine-containing olefins in an aqueous medium in the presence of catalysts and perhalogenated carboxylic acids, characterized in that the polymerization is carried out as a suspension polymerization in the presence of 0.004 to 0.0001 percent by weight, based on the aqueous phase, of a perhalogenated fluorine or fluorine and Carboxylic acid containing chlorine and / or a salt of such an acid. 2. The method according to claim 1, characterized in that the polymerization is carried out in the presence from 0.0015 to 0.0005 percent by weight, based on the aqueous phase, of a perhalogenated Carboxylic acid containing fluorine or fluorine and chlorine and / or a salt thereof Acid performs. 3. Process according to Claims 1 and 2, characterized in that the fluorine-containing olefin is used Tetrafluoroethylene uses. 4. Process according to Claims 1 to 3, characterized in that one is perhalogenated as Carboxylic acid perfluorooctanoic acid and / or its salts are used. Considered publications:
German Patent No. 916 470;
French patent specification No. 1 115 720. © 109 618/504 6.61