DE2127439A1 - Process for the polymerization of vinyl chloride - Google Patents

Description

Dr. F. Lederer t.Junittfl

βΐ Hamburg öO ^

Solvay & Cie., 33 Rue du Prince Albert, Brussels / Belgium

Process for the polymerization of vinyl chloride. Addition to patent (application P 17 45 409.0-44)

Priority: June 10, 1970, Belgium, n ° 90 156

The main patent (application P 17 45 409.0-44)

relates according to claim 1 to a process for polymerization of vinyl chloride alone or together with other monomers in bulk with stirring in the presence of one or more Free radical forming catalysts, characterized in that the polymerization in the gas phase in In the absence of any liquid phase.

According to claim 2, the polymerization can be carried out in the presence of a previously introduced inert solid will·

If the polymerization of vinyl chloride is carried out in the presence of such a pesticide, it has now been found that one obtains improved polymerization yields when the temperature and pressure conditions between certain well-defined limits fluctuate.

The invention therefore relates to an improvement of the process for the polymerization of vinyl chloride according to the main patent and is characterized in that when working in the presence of a previously introduced inert solid, the polymerization ^{temperature is between 40 and 80 °} C. and the pressure in the autoclave is higher

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than the pressure threshold above which the effects of inert pesticides-gaseous-vinyl chloride are significantly modified but is below the saturation vapor pressure of the vinyl chloride at the polymerization temperature

In the particular pail, where, polyvinyl chloride is called When using inert pesticides, the temperature and pressure conditions are limited to the following criteria:

The temperature is between 40 and 80 ⁰ C the relative pressure (p_) is given by the relationship

two 0.45 <. P _r <1 is defined, the / polymerization parameters also being delimited by the hatched area ABC of diagram I.

The pressure is expressed in terms of a relative pressure (p _r ) which is determined by the ratio between the polymerization pressure (p) and the saturation vapor pressure of the vinyl chloride at the polymerization temperature

Cd j ή = * -
^ e ' ^p rp _s

is defined «,

In order for the polymerization of the gaseous vinyl chloride to be effected at a high rate, one must have adequate Select temperature and pressure conditions

In diagram 1 (Pig. 1) an interesting work zone is defined. This zone hatched in diagram 1 is limited by:

two horizontal straight lines CE and BD corresponding to the temperatures of 40 and 80 ^° C

a vertical straight line BC corresponding to at «mr8» g ± Mm: ρ = 1, that is a pressure at the beginning of saturation

a curve AQ, the course of which results from the following.

Under these conditions there is no liquid phase in the reaction medium and the process is particularly in ■ economically and technically advantageous.

The boundaries of this hatched zone are exclusive: if ρ = 1, one is at a pressure corresponding to nd ^ i ^ mSättij ^ ungsbegJ ^

10 9 8 5 1/16 5 2

of liquid vinyl chloride.

The temperature and pressure parameters as just defined, which are the critical factors of the method according to the invention represent, emerge from the study of the effects between the inert solid, for example polyvinylchloride (PVC), and gaseous vinyl chloride (VG) in the process conditions.

This study has led to the determination according to which these effects go beyond a certain, from the polymerization temperature the dependent point can be clearly modified ©

The dynamic method testing of the adsorption and desorption phenomena in the PVO-VC system made it possible to to define the influence of the parameters temperature and pressure on the effects.

Method used to study the phenomena of adsorption and desorption from vinyl chloride to polyvinyl chloride.

The method used is based on the principle of chromatography in the vapor phase and is known as frontal analysis odei known as continuous injection.

It consists in saturating an adsorption column (PVC) by continuously passing gaseous vinyl chloride (VC) through it up to a given pressure ρ, then saturating the adsorbate (VC) by means of a pure inert gas (N ₂ , Ar, Ne, ...) , Called carrier gas, to elute.

If you look at the composition of the gas as a function of time analyzed during desorption, one can find the constant of Determine the rate of desorption under the temperature and pressure conditions used.

In this case the chosen temperature between 40 and 80 ⁰ C and is -Uruck varies between 3 kg / cm and the saturation pressure. The polyvinyl chloride is degassed in a vacuum of 10 mm Hg for one hour before it is introduced into the apparatus.

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The polyvinyl chloride is then saturated with vinyl chloride by purging with pure gaseous vinyl chloride of a given amount in the unit of time at the selected temperature and the selected total pressure p _Q.

When saturation is reached, elution is ensured by a given amount per unit of time of nitrogen, which is equal in volume to the amount of vinyl chloride, the total pressure being kept constant and equal to p _Q. The desorption curve obtained enables the desorption

—Kt constant k according to the following relationship: P = p _Q .e to be calculated, where ρ is the maximum pressure of the gaseous vinyl chloride realized during the experiment and whose "value is equal to the total pressure in the apparatus, ρ the partial pressure of the gaseous vinyl chloride in the Eluate after an elution time t.

Diagram 2 (Pig. 2) + shows the variation of the constant k of desorption rate as a function of relative pressure ρ'emperaturen -i-40, 55 and 70 ⁰ C for (curves I, II and III) and for a Eluierungsleistung of 5.5 liters of nitrogen per hour.

The relative pressure ρ is, as previously defined, by the relationship between the test pressure ρ and the saturated vapor pressure of the vinyl chloride at the test temperature. I ¹ Ur temperatures above 40 ⁰ C one finds that the relation between log k and -—— can be represented by

^p r
two parts of straight lines of different slopes, the intersection of which marks a break in the development of the constant of the rate of desorption.

In other words, it exists for all temperatures above 40 ^ b a pressure threshold above which the effects of PVC-VC are significantly changed.

The relative pressure corresponding to this discontinuity is increased as the elution efficiency decreases. These The phenomenon is shown in Diagram 3 (Figo 3), where you can see the fluctuations in the constant of the desorption rate as a puncture of the pressure for a temperature of 55 ° n

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Elution capacities of 4-5 »5 and 7» 6 1 nitrogen per · Hour with curves I, II and III.

By taking the value of the pressure according to the discontinuity as a function of the elution performance V, expressed in liters

«^ ^ 4 JT * ^ L · - * Λ for £ r * m « X »

per hour (4-5.5 and 7.6 liters of nitrogen per hour) /, the pressure corresponding to the discontinuity can be obtained by extrapolation for a zero elution rate.

An example of such extrapolation is shown in Chart 4 for a temperature of 55 ⁰ O.

The corresponding relative pressure was obtained by dividing the value of the extrapolated pressure by the value of the saturation pressure of vinyl chloride at 55 0 (9 kg / cm)

^p r * ps ^{a 1} ^ ⁼ ° » ⁸⁸ This value forms point 2 (curve AG - diagram 1).

* k O

An airloges experiment was carried out at 70 G, which made it possible to obtain point 3 (curve AC - diagram 1). Meanwhile at 40 ⁰ G the jerk threshold, which is linked to the modification of the PVC-YG actions, falls together with the saturation (p = 1) and its value is not influenced by the elution power, which is point 1 (curve AG diagram 1 ) explained.

The curve Aö, limit of diagram 1, was obtained by Connect the points extrapolated as indicated above (1, 2 and 3).

This curve AC shows the relative temperature for a given temperature Pressure above which the effects of PVC / gaseous VC are modified in such a way that the polymerization of the gaseous vinyl chloride is of particular interest.

Under these conditions, the vinyl chloride acts sufficiently on the polyvinyl chloride to cause the polymerization reaction particularly advantageous in economic and technical Respect runs

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The discontinuity observed in diagram 2 (points D, E and F) defines for each temperature a value of the relative pressure which, extrapolated to zero elution rate (diagrams 3 and 4) ₍ indicates the pressure of gaseous vinyl chloride which must be exceeded so that the PVC-gaseous VC system is in the zone of interest in terms of polymerisation.

At 40 ⁰ C must be a relative ^ Rpt equal to 1 (saturation pressure) exceed, for the system to PYC-VC is in the interesting polymerization. At this temperature and below it is not possible to carry out an interesting gas phase polymerization.

On the other hand, the more the polymerization temperature is increased by so the relative pressure does not have to be important in order to be interesting to realize te polymerization conditions »

According to the process of the invention, one works in the presence of a previously introduced solid. This solid, which can be powder, granule or fiber form, must be inert under the polymerization conditions.

The nature of this solid phase can be any, though it just does not represent or contain a polymerization inhibitor

For example, one can cite asbestos, silica, perlite, and the like.

If the polymerization reaction takes place in the presence of such a carrier, they become loaded with polyvinyl chloride right at the beginning of the reaction and the polymerization proceeds under the same conditions as those described above, when using polyvinyl chloride as a carrier.

However, it is preferable to use plastic material, and whole especially polyvinyl chloride itself, or a resin which one wants to mix with the polymer to be obtained.

The amount of previously introduced into the Polymeric 1-i.Gßs reaction solid phase is variable and the solid phase / monomer to be polymerized ratio is not critical. However used

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one preferably 1-20% solids, based on weight of the polymer to be obtained.

All catalysts can be used as catalysts for the polymerization or use all catalytic systems which are in solid form, usually for the polymerization of vinyl chloride are needed and in particular the free radical generating catalysts.

The amount of catalyst used is preferably between 0.01 and 5 wt. ^, Based on the monomer to be used,

Stirring the reaction medium has an important influence on the polymerization yield. One therefore subjects the solids contained in the reactor continuous and constant stirring by means of appropriately selected M stirrers, which are operated at very specific speeds.

Agitators of the type used for mixing and homogenizing powdery products will preferably be chosen are used, and in particular agitators of the type of ribbon mixer, blade scraper, and the like.

The method according to the invention can also be used for the copolymerization of vinyl chloride with other monomers, e.g. ethylene, propylene etc. "

Resins can also be used according to the process of the invention Obtained improved stabilization if powdered stabilizers are incorporated into the solid starting phase.

The process according to the invention is very economical Interest, because apart from the fact that the polymerization yields are significantly improved, the obtained require Resins neither spinning off nor drying due to the lack of a liquid phase in the reaction medium «,

In addition, the unreacted monomer or monomers in Gaseous form can be recovered and returned immediately and without subsequent cleaning treatment «,

Another very important advantage is the absence of Encrustation on the walls of the polymerization reactor.

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Resins with a number K between 40 and 80 at polymerization ^{temperatures between 40 and 80 °} C. ± h can be produced in the pallet for the polymerization of vinyl chloride.

One can resins having an apparent bulk specific gravity from 0.25 to 0.86 / kg dm obtained, wherein the adsorption of ^w calibration machern 6-53 g per 100 g of resin chwankt s.

The resins obtained have an increased degree of purity and therefore excellent! Transparency · This is mainly due to the fact that no foreign substance is the Contaminated polymer during polymerization

example 1

A homogenized mixture of 100 g of polyvinyl chloride as a powder and 1 g of lauroyl peroxide is introduced into the autoclave.

This mixture is mixed in a continuous else ^w by means of a ribbon stirrer, wherein the entire height of the autoclave and covered with a rotating speed of 250 revolutions per minute "

The temperature of the autoclave is brought to 59 ° C. and gaseous vinyl chloride is introduced.

The pressure prevailing in the autoclave pressure is 8 kg / cm (p = 0.84), and is in this ert ^w during the polymerization by successively introducing the gaseous vinyl chloride maintained.

After 5 hours of reaction, the introduction of vinyl chloride is interrupted and 800 g of polyvinyl chloride are obtained, which is a Yield of 140 g / hour corresponds.

Dm is an equivalent polymerization yield according to the Process in aqueous suspension under - ^ go down from the It took 8 hours to obtain equal amounts of the different reactants and at the same reaction temperature polymerize for a long time.

10 9 8 5 1/16 5

Examples 2-4

The following examples are intended to prove that if you go outside the claimed Frenzen with the inventive Process works, the polymer yields obtained are very low. Example 4 is given as a comparison

The polymerization is carried out according to the method of Example 1, but under the conditions shown in Table 1.

Table 1

Examples ρ J A. Polymerization ^ "- ■ ——.___ ^ _ ^^ 70 τ- conditions ⁰ C 45 0.55 70 temperature 0.9 7.1 0.92 Relative - ^ jerk kg / cm 6.3 60 12th Absolute pressure G 60 1 60 Used solid (PVC) G 1 5 1 lauroyl peroxide hours 5 260 5 Reaction time G 110 40 760 Obtained amount of PVC g / hour 10 140 Polymerization yield

The results of Table 1 clearly show that if one works outside the claimed limits determined by the hatched area ABC of diagram 1, which PVC yields obtained are very low.

1 Q 9 8 5 1/16 5 2

Claims (6)

Claims 1. Process for polymerization and / or copolymerization of vinyl chloride according to the method of the main patent (Registration P 17 45 409.Q-44), characterized in that in the case when one is in the presence of an inert, previously introduced Solid works, the polymerization temperature is between 40 and 80 C and the prevailing in the autoclave ^ jerk above the pressure threshold, above those that Actions of inert solid-gaseous vinyl chloride are significantly modified, and below the saturated Is the vapor pressure of the vinyl chloride at the polymerization temperature. 2 ο The method according to claim 1, wherein the inert solid is polyvinyl chloride, characterized in that at a polymerization ^{temperature between 40 and 80 0} C and at a relative - ^ jerk, defined by the relationship 0.45 £. p_ <, 1 works, the two parameters temperature and pressure also being limited by the hatched area ABC of diagram 1. 3. The method according to claim 1, characterized in that the polymerization of the vinyl chloride in the presence of 0.01 up to 5 wt. # of a free radical generating catalyst carried out 4. The method according to claim 1, characterized in that one the polymerization of the vinyl chloride is carried out in the presence of 1 to 20 wt. ^ of the inert solid. 5. The method according to claim 1, characterized in that the inert solid is selected from the group of asbestos, silica and perlite » 6. The method according to claim 1, characterized in that the inert solid is in fiber form. 10 9 8 51/16 5 2 7β Method according to claim 1, characterized in that the polymerization is effected in the presence of a previously introduced solid stabilizer ". B. New industrial products, namely the polymers obtained by a process according to one of the preceding claims 109851/1652