DE2644202A1 - PROCESS FOR THE POLYMERIZATION OF VINYL CHLORIDE IN AQUATIC SUSPENSION - Google Patents

Description

DR. A. VAN DERWERTH

DlPL-ING. (1934-1974)

P AT E N T A K VVA LT E

DR. FRANZ LEDERER

DlPL-CHEM.

2b442u2

REINER F. MEYER

DIPL-ING.

8000 MUNICH 80 ' LUCILE-GRAHN-STRASSE

TELEPHONE: (089) 472947 TELEX: 524624 LEATHER D TELEGR .: LEATHER PATCNT

Sept. 15 1976 pp. 75/31

Solvay & Cie.

33, Rue du Prince Albert, Brussels, Belgium

Process for the polymerization of vinyl chloride in aqueous Susnension

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The invention "relates to a process for polymerization of vinyl chloride in aqueous suspension, which is used to improve the productivity of polymerizers leads. In particular, it relates to a method in which the polymerization in the presence of a Initiator pair is carried out.

Polymerization in aqueous suspension is common Polymerization procedure used for the production of vinyl chloride polymers. At this . Procedure soluble initiators are used in the monomer, e.g. B. organic peroxide compounds or azo compounds. Usually the polymerization carried out intermittently, and the phenomenon of self-acceleration is observed, i.e. H. the reaction rate increases in the course of how the degree of conversion to polymer increases. In common practice, therefore, the amount of used Initiator fixed at such a value that the control of the polymerization temperature in the course of the Period of time in which the phenomenon of self-acceleration is most intense, can be maintained. One is therefore content with not making full use of the Cooling capacity of the reaction vessels during the first part of the polymerization cycle. These measures are for reasons indispensable for the safety and quality of the resins. However, they "bring about a reduction in the average rate of polymerization and thus also the productivity of the polymerization facilities.

Various measures have already been proposed to improve the productivity of reaction vessels for the polymerization of vinyl chloride in aqueous suspension. This includes the use of pairs of specific initiators. For example, one can use

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of systems that call acetylcyclohexylsulfonyl peroxide, which is a more rapid, low dose used Is initiator, and another initiator such as terbutyl peroxypivalate, the diisopropyl or di-2-etherealhexyl peroxydicarbonates and azo-bis-2,4-dimethylvaleronitrile, the used in larger doses include, see Belgian U.S. Patent 756,976.

The use of such systems makes it possible to effectively increase the productivity of the reaction vessels to enhance. However, this improvement is not very essential as there is an absolute need to the amount of acetylcyclohexylsulfonyl peroxide increases in this way limit it to being completely consumed before the phenomenon of self-acceleration becomes significant and there is a risk that thermal control of the polymerization reaction becomes difficult.

The object of the invention is an improved method to the productivity of equipment for the polymerization of vinyl chloride in aqueous suspension increases significantly to enhance.

The invention therefore relates to a process for the polymerization of vinyl chloride in aqueous suspension using of oil-soluble initiators for radical polymerization, which is characterized in that one initially a pair of initiators is used, and that one of the initiators is selectively used in the course of the polymerization deactivated.

It has been found that the selective deactivation of one of the initiators in the course of the polymerization makes use of it of larger doses of very active initiators

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made possible, but the overall thermal control of the polymerization reaction is always taken into account • The method according to the invention enables the polymerization of vinyl chloride in aqueous suspension to carry out according to a kinetic which is referred to as "square" " will, d. H. the rate of polymerization is essentially constant during the polymerization cycle. Therefore one can use the cooling devices of the ee action vessels Use up to full capacity from the beginning of the polymerization. In addition, the properties of the Polymers produced by the process according to the invention, such as their thermal and electrical properties excellent.

^J o ^v

The point in time at which the selective deactivation of one of the initiators is carried out is not particularly critical. This can therefore be carried out at any point in time in the course of the polymerization, ie after the start but before the end of the polymerization. However, in order to ensure a substantial increase in the productivity of the polymerization equipment, one of the initiators is advantageously deactivated before the degree of conversion to polymer exceeds 70a. In fact, it has been found that if the deactivation at high Umwandlungsgra to is performed, which are equal to or higher than about 70% of the productivity gain is minimal or zero. In addition, it is not advantageous to carry out the deactivation when the degree of conversion is still very low, e.g. B. in the order of a few percent. In such a case, there is a risk that the polymerization rate slows down intermittently and, moreover, the improvement in productivity is not optimal. In general, one of the initiators is selectively deactivated,

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after the degree of conversion has reached at least 10 % . According to a preferred embodiment of the process according to the invention, one of the initiators is selectively deactivated when the degree of conversion is between 20 and 60% and particularly preferably between 30 and 50%.

The ones used to carry out the selective deactivation Funds can be anything, although they are of course must be adapted to the type of initiators used in combination. So if you are a couple of initiators is used which has a first initiator that is exclusively oil soluble, d. H. soluble in the monomer, however Little or no solubility in water, and a second initiator that is oil-soluble and water-soluble at the same time is, d. H. is soluble in the monomer, but is also relatively soluble in water, one can use one of the Selectively deactivate initiators with the aid of a water-soluble substance which is capable of the Deactivation (reduction or destruction) of the initiator, which has the higher solubility in water, to bring about.

If the two initiators used are exclusively oil-soluble, i. H. but soluble in the monomer to me Are little or not soluble in water, one of the initiators is selectively deactivated with the help of an oil-soluble one Substance which is able to bring about the deactivation of only one of the initiators, which however, is practically inert to the other initiator.

In the description, selective deactivation is the practical deactivation of one of the initiators without substantial deactivation of the other initiator too

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to understand. Therefore the type of initiators is not particularly critical. You can therefore choose from among the Polymerization of vinyl chloride in aqueous suspension applied, oil-soluble initiators are selected. Examples of such initiators include: lauroyl and benzoyl peroxides, tert-butyl peroxypivalate, Acetylcyclohexylsulfonyl peroxide, dialkyl peroxydicarbonate and azo compounds ·. Of course, it is advisable to select catalytic initiator pairs, which is the selective deactivation of one of its components enable.

In general and advantageously, pairs of initiators are used which contain at least one initiator which is very active under the polymerization conditions, such as. B. Acetylcyclohexylsulfo ^. / Peroxide or the dialkyl peroxydicarbonates. Preference is given to using pairs of initiators which contain at least one dialkyl peroxydicarbonate. Initiator pairs, which are particularly suitable, are selected from the following:

- di-lower alkyl peroxydicarbonate plus di-higher alkyl peroxydicarbonate;

- Di-lower alkyl peroxydicarbonate plus azo-bis-nitrile;

- Di-higher alkyl peroxydicarbonate plus azo-bis-nitrile.

Among di-lower alkyl peroxydicarbonates. In the description, dialkyl peroxydicarbonates are to be understood, the alkyl chains of which contain 1 to 6 carbon atoms and preferably 1 to M carbon atoms, it being possible for these alkyl chains to be different or identical and optionally substituted, for example, by halogen atoms. A di-lower alkyl peroxydicarbonate that is particularly preferred is diethyl peroxydicarbonate. Such peroxydicarbonates have a noteworthy solubility in water.

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Under di-higher alkyl peroxydicarbonates are in the description Exercise to adjust dialkyl peroxydicarbonates, their alkyl chains at least 7 carbon atoms and preferably at least Containing 12 carbon atoms, the alkyl chains being different or identical and optionally substituted could be.

Peroxydicarbonates are advantageously used, their Alkyl chains contain 12 to 20 carbon atoms. A di-higher alkyl peioxydicarbonate, which is particularly preferred is dicetyl peroxydicarbonate.

Azo-bis-nitriles in the description are compounds to understand the following general formula:

CN-E-N = N-H-CN

wherein E is straight or branched, 2 to 10 carbon atoms and preferably represents alkylene chain containing 4 to 8 carbon atoms.

A particularly preferred azo-bis-nitrile is azo-bis-2,4-dimethylvaleronitrile.

As already described above, the must for the selective deactivation of one of the initiators of the catalyst pair agents used be adapted to each initiator pair.

If you use catalyst pairs which contain two exclusively oil-soluble initiators, one of which is reducible, e.g. B. Couples containing a di-higher alkyl peroxydicarbonate contained in a mixture with an azo compound, the selective deactivation of one of the takes place Initiators advantageously by adding a selective, oil-soluble reducing agent to the polymerization medium. Examples of such reducing agents are

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phenolic compounds such as phenol, hydroquinone, p-tert. Butylcatechol or 8-hydroxyquinoline, thioethers and organic phosphites called which are the peroxydicarbonates deactivate, but without affecting the Azo initiators are.

When using pairs of catalysts which have both an oil-soluble and a water-soluble initiator in the Contain a mixture with an exclusively oil-soluble initiator, e.g. B. the "preferred catalyst pairs,. which is a di-lower alkyl peroxydicarbonate in a mixture with a di-higher alkyl peroxydicarbonate or an azobisitrile contain, the selective deactivation of the oil- and water-soluble initiator takes place advantageously by adding a water-soluble, basic substance or a water-soluble, reducing substance to the polymerization medium, which is able to reduce the oil- and water-soluble initiator. Examples of basic substances are water-soluble alkali metal, alkaline earth metal and ammonium hydroxides, called carbonates and bicarbonates. Examples of water-soluble, reducing substances are called the nitrites and the sulfites of alkali metals. Alkali metal and ammonium hydroxides are preferably used to add the di-lower alkyl peroxydicarbonates deactivate which in a mixture with exclusively oil-soluble Initiators are used. A particularly preferred hydroxide is ammonium hydroxide. Because of his higher volatility, this hydroxide is not found in the finished polymer. Its use moreover ensures that polymers are obtained which have a number of highly desirable properties have, namely not only excellent heat stability but also increased transparency

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and good electrical properties.

According to a particularly preferred embodiment of the invention, a pair of catalysts is therefore used that by a di-lower alkyl peroxydicarbonate in the mixture with a di-higher alkyl peroxydicarbonate or an azo compound is formed, and the di-lower alkyl peroxydicarbonate is selectively deactivated with the aid of ammonium hydroxide when the degree of conversion is between 30 and 50%.

The amount of deactivating agent to be used depends of course on the initiator to be deactivated. It is therefore advantageously carried out by simple experiment determined in advance for each particular case. In general one uses the deactivating one Agent in just sufficient amount to selectively deactivate an initiator.

The relative amounts of the polymerization according to the Initiators used according to the invention are also determined experimentally: they depend in particular on the half-life of the initiators under the polymerization conditions as well as the Heat exchange capacity of the polymerizer away.

As an example it should be stated that when using the preferred Catalyst pairs based on di-lower alkyl peroxydicarbonates, generally 0.1 to 0.8 parts of di-lower alkyl peroxydicarbonate and 0.1 to 3 parts of di-higher alkyl peroxydicarbonate or 0.1 to 0.8 parts of azobisitrile per 100 parts by weight of the monomer can be used.

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Except for the selective deactivation of one of the initiators the polymerization of vinyl chloride is carried out in aqueous suspension under the classic conditions of this type of polymerization.

Therefore, the polymerization of vinyl chloride is carried out in the presence of the usual components for the polymerization in aqueous suspension by, d. H. Suspending agents as well as possibly various additives, which are added at any stage of the polymerization, e.g. B. stabilizers, plasticizers, coloring substances, reinforcing agents or agents that facilitate processing.

The suspending agent can be any of the usual suspending agents be selected, e.g. B. polyvinyl alcohols, gelatin, water-soluble alkyl celluloses and carboxymethyl celluloses as well as various copolymers and condensation products such as. B. from the condensation products derived from polyalkylene glycols and polyamines. Of course you can also use mixtures of suspending agents, and the way in which they are introduced is not critical.

The general working conditions for the polymerization according to the process according to the invention do not differ from the conditions usually used. The temperature is generally between 4-0 and 75 ^° C. and the pressure is generally less than 15 kg / cm

Polymerization of vinyl chloride according to the invention is both homopolymerization of vinyl chloride as also to understand the copolymerization of vinyl chloride with other polymerizable monomers. As examples

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for the latter are vinyl esters such as vinyl acetate, acrylic esters such as methyl acrylate and butyl methacrylate, acrylic-like nitriles such as acrylonitrile and methacrylonitrile, unsaturated diesters such as diethyl maleate, allyl esters such as allyl acetate, α-olefins such as ethylene and propylene, vinyl ethers and styrene called like connections.

However, the process according to the invention is preferably used for the production of polymers which at least 50 mol% and "particularly" preferably at least Contain 80 mol% of vinyl chloride.

When selecting the deactivating connection, the Type of comonomer, if any, is taken into account.

The invention is further illustrated by the following examples explained, this referring to the polymerization of vinyl chloride in aqueous suspension in the presence of Couples of initiators refer to diet hy! Peroxydicarbonate in a mixture with dicetyl peroxydicarbonate (Example 1) or azo-bis-2,4-dimethylvaleronitrile (Example 2) contained th.

The short-term heat stability (initial discoloration) and the long-term heat stability of the polymers produced were determined on pelts obtained by kneading the two compositions given below 180 ° C (roller mixer) were obtained.

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2844202

Composition in weight A B

Polyvinyl chloride 100 100 Dioctyl phthalate 50 40 tribasic lead sulfate - 2 Barium-Cadmium Stabilizer 1 - Polyethylene wax - 0.5 Stearic acid 0.5 0.5

The initial discoloration was determined after kneading for 2 minutes. The long-term heat stability was determined by measuring the amount of time that elapsed before the fur turned black.

Example 1

140 kg of demineralized water, 180 g of polyvinyl alcohol, 26.6 g of diethyl peroxydicarbonate and 60 g of dicetyl peroxydicarbonate were introduced into an autoclave with a capacity of 300 l, which was provided with a stirrer and a double jacket, at ambient temperature and with stirring (100 rpm). The autoclave was sealed, stirring was stopped and the autoclave was placed under partial vacuum (100 mm Hg abs.), Then purging with nitrogen (600 mm Hg abs.) Before placing it under the same partial vacuum . Stirring was resumed (180 rpm) and 100 kg of vinyl chloride was then introduced. The medium was then heated ^{to 53 ° C.} This point in time at which the polymerization starts is regarded as the beginning of the complete polymerization cycle.

After 3 hours and 30 minutes (degree of conversion = 50%) were in the aqueous suspension 30 g of ammonium hydroxide in

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Introduced in the form of an aqueous n / 10 solution and continued the polymerization. After 6 hours (T _n + 6 h) the pressure in the reaction vessel had dropped to 3.4 kg / cm. The polymerization was stopped (the monomer was blown off), the mixture was cooled and the polymer was recovered by centrifugation and subsequent drying.

The essential characteristics of the polymerization reaction are summarized in Table I below. The essential properties of the polymer are given in Table II below.

Example 2

This example relates to the polymerisation of vinyl chloride in aqueous suspension at 53 ° C. accordingly the procedure of Example 1, but using 26.6 g of diethyl peroxydicarbonate and 4-0 g of azo-bis-2,4-dimethylvaleronitrile. jtfach 3 hours and 30 minutes (Degree of conversion = 50%) were 30 g of ammonium hydroxide introduced into the suspension in the form of an aqueous n / 10 solution and the polymerization continued. After 6 hours

the pressure in the reaction vessel was 2.8 kg / cm abs. fallen off. The polymerization was stopped, the polymer was recovered and its properties determined, these are also given in Tables I and II.

Example 3 (comparative example)

This example, which corresponds to the general procedure of Example 1, relates to the polymerization of vinyl chloride in the presence of diethyl peroxydicarbonate as the only initiator. The polymerization was carried out at 53 ° C in The presence of 24.5 g of diethyl peroxydicarbonate was carried out.

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After 7 hours and 30 minutes the pressure was in the reaction vessel to 4 kg / cm. Section. sunk. The Polymerization ' was stopped, the polymer recovered and its properties determined.

The comparison of the results of Examples 1 and 2 with that of Comparative Example 3 clearly shows those resulting from the process according to the invention Advantages, namely, a substantial improvement in the productivity of the reaction vessel and the manufacture of vinyl chloride polymers, which have excellent thermal and electrical properties.

Table I. Polymerization conditions

E.g. total duration of the polymerisation maximum point in time duration under constant temperature the maximum pressure ⁵ ^ turgra- paint

serves ** G-radii- ( ⁰ C) th

1 6th H ^4th H 10, 0 after 3
30 min H 2 6th H 4th H 11 5 after 3
45 min H 3
(Cf.) 7h3O 6 h 15 minutes 12, 0 after 6 H

the duration is calculated from time t _Q on. ΔΤ: temperature difference between the autoclave and its double jacket

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. 4P.

Table II Properties of the polymers

E.g. heat stability of the kneaded pelts initial coloring long-term stability
AB AB

specific line resistance in the transverse direction, 10-12 Ohm.cm at 2O ° C at 60 ⁰ C

pink-white colors,
very

clear

borrowed slightly white-pink-yellow

slightly rose-0 / ergl) rose-colored

Colours.

> 20 min> 30 min

1200

1.5

> 20 min> 30 min 1100> 20 min> 30 min 8400

0.82

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Claims (18)

Claims M J Process for the polymerization of vinyl chloride in aqueous suspension using oil-soluble initiators for radical polymerization, thereby
characterized in that one initially uses a pair of initiators, and that one of the initiators in the
The course of the polymerization is selectively deactivated. 2. The method according to claim 1, characterized in that one of the initiators is selectively deactivated before the degree of conversion exceeds 70%. 3. The method according to claim 1 or 2, characterized in that that one of the initiators is selectively deactivated after the degree of conversion has reached at least 10%. 70981S / 1063 ORiGJNAL 26442Ü2 • X- 4. The method according to claim 1, characterized in that one of the initiators is selectively deactivated as soon as the degree of conversion is between 20 and 60 % . 5. The method according to any one of claims 1 "to 4-, characterized
characterized in that the initiator pair comprises an initiator which is oil-soluble and water-soluble at the same time, and an initiator which is exclusively oil-soluble, ■. 6. The method according to any one of claims 1 "to 4-, characterized
characterized in that the initiator pair comprises two initiators which are exclusively oil-soluble. 7. The method according to any one of claims i "to 6, characterized
characterized in that the initiator pair comprises at least one dialkyl peroxydicarbonate. 8. The method according to claim 7 ·, characterized in that the initiator pair is formed by a dialkyl peroxydicarbonate, the alkyl chains of which contain 1 to 6 carbon atoms, and a dialkyl peroxydicarbonate, the alkyl chains of which contain at least 7 carbon atoms
will. 9. The method according to claim 7, characterized in that the initiator pair is formed by a dialkyl peroxydicarbonate, the alkyl chains of which contain 1 to 6 carbon atoms, and by an azo compound of the azobis-nitrile type. 10. The method according to claim 7? characterized in that the initiator pair by a dialkyl peroxydicarbonate, the alkyl chains of which contain at least 7 carbon atoms, and by an azo compound of the type one
Azo-bis-nitrile is formed. 703815/1063 11. The method according to claim 8, characterized in that the initiator pair by diethyl peroxydicarbonate and Dicetyl peroxydicarbonate is formed. 12. The method according to claim 9, characterized in that the initiator pair by diethyl peroxydicarbonate and is formed by azo-bis-2,4 ~ dimethyrvaleronitrile- 13. The method according to claim 10, characterized in that the initiator pair by dicetyl peroxydicarbonate and is formed by aso-bis-2,4-dimethylvaleronitrile. 14. The method according to any one of claims 1 to 5, 7 to 9, 11 and 12, characterized in that one of the initiators by adding a water-soluble, basic Substance selectively deactivated in the aqueous suspension. 15. The method according to claim 14, characterized in that that alkali metal hydroxide or ammonium hydroxide is used as the water-soluble, basic substance. 16. The method according to claim 15, characterized in that that ammonium hydroxide is used as a water-soluble, basic substance. 17. The method according to any one of claims 1 to 4, 6, 10 and 13, characterized in that one of the Deactivated initiators by adding an oil-soluble, reducing substance to the aqueous suspension. 18. The method according to claim 17, characterized in that that the oil-soluble reducing substance is a phenolic compound. 709815/1063