WO2003016363A2

WO2003016363A2 - Device and method for polymerisation

Info

Publication number: WO2003016363A2
Application number: PCT/EP2002/008297
Authority: WO
Inventors: Heinz Klippert; Roland SCHÄFER
Original assignee: Vinnolit Gmbh & Co. Kg
Priority date: 2001-07-25
Filing date: 2002-07-25
Publication date: 2003-02-27
Also published as: DE10135402A1

Abstract

The invention relates to a device and a method for polymerisation, especially a pressure container for the polymerisation of vinyl chloride and/or monomers which can be copolymerised with vinyl chloride. Said device and method enable a continuous reaction to be carried out until a quasicrystalline covering surpresses the formation of a coating on the inner walls.

Description

description

Polymerization apparatus and method

The invention relates to an apparatus and a method for polymerization, in particular a pressure vessel for the polymerization of vinyl chloride and / or of monomers copolymerizable with vinyl chloride.

In the polymerization of vinyl chloride, devices such as pressure vessels in sizes up to 200 m ³ are used for economic reasons. Polymerization is a highly exothermic process in which considerable amounts of heat (in the case of vinyl chloride 1,550 kJ / kg) are released. In order to allow the polymerization to proceed in a controlled manner, the waste heat must be removed. This generally takes place via the inner wall of the container, so that good thermal conductivity of the inner wall of the container is important for rapid dissipation of the heat of reaction and thus for controlling the highly exothermic reaction.

In the case of polymerization, more or less strongly adhering polymer deposits form on the inner wall of the reaction vessel and the internals, which on the one hand severely hinder the removal of the heat of reaction and on the other hand significantly impair the product quality due to flaking polymer deposits.

As a technical solution, there is still mainly the cleaning of the reaction vessel and the internals with high pressure water after emptying the completely polymerized reaction mixture. This solution is uneconomical, since no new reaction batch is charged during cleaning. that can. The specific output (t product / cbm reaction volume), for example, serves as a measure of the economy of a reaction container, which is significantly deteriorated by a cleaning time.

Flanking the removal of the polymer coating, anti-coating agents, in particular based on phenothiazine oligomers, polyarylphenols, phenoxazine derivatives, phenol-formaldehyde condensation products and bisphenol-A condensation products, are used to suppress its formation, which are applied in different, generally known ways the inner wall of the container and the surfaces of the internals in the container are applied. By adding a deposit-preventing additive to the reaction medium, e.g. of an inorganic reducing agent (e.g. sodium nitrite) can

Tendency of deposit formation to be further reduced. The disadvantage of this procedure is that the application of the anti-fouling agent has to be repeated before each new reaction batch and additional costs arise.

The tendency towards deposit formation, with the heat dissipation worsening after a reaction batch, has hitherto been the development of continuous polymerization processes, e.g. inhibited the polymerization of vinyl chloride to polyvinyl chloride.

The invention is therefore based on the object of creating a device and a method for polymerization which overcomes the disadvantages of the prior art by creating a permanently effective modification of the surface of the reaction vessel and / or the existing internals, as a result of which the Polymer deposits on the reaction vessel wall and / or the internals permanently prevented is changed and consequently the use of expensive anti-fouling agents and / or additives can be dispensed with.

It has surprisingly been found that in the case of a quasi-crystalline coating, the formation of polymer deposits on the inner wall of the container and / or on the internals during a polymerization, e.g. that of vinyl chloride, largely or even completely omitted.

Depending on the extent of the quasi-crystalline coating, cleaning with high pressure water, the use of anti-fouling agents before each new reaction batch and / or the anti-fouling liquor additives can be dispensed with.

The quasi-crystalline coating of a device for polymerization can be applied to a device that is used or to a device that is still new. The coating is applied to e.g. Sandblasting, mechanical grinding, electropolishing according to prepared and cleaned inner wall made of e.g. Stainless steel and / or carbon steel by means of chemical vapor deposition (CVD), physical vapor deposition (PVD), plasma coating and / or flame spraying, as known for example from EP 356287 or US Pat. No. 5,433,978.

For example, only the surface of particularly critical internals of a device for polymerization (such as thermal sensors, baffles and / or stirrer blades) can be completely or partially coated, or all surfaces of the internals and / or the inner walls of the device can be completely or partially coated with a quasi-crystalline surface. Preferably the surfaces or inner walls completely coated with a quasi-crystalline surface.

The term "aluminum transition metal alloy" here comprises an alloy of at least two metals, in particular of more than two metals, such as a ternary, quaternary and / or higher alloy, as long as the stoichiometry involves the formation of a quasi-crystalline phase, as described, for example, by Stephens and Goldman in "The structure of Quasicrystals", Scientific American, April 1991.

Sensors such as temperature sensors, pressure sensors, stirrer blades and / or baffles or the like are referred to as internals of the pressure vessel. In general, all parts of the pressure vessel that come into contact with the reaction mixture can be coated with a quasi-crystalline alloy to avoid a deposit.

For example, the coating will be carried out as completely as possible on the inner surface of the device and / or on its internals, so that the formation of a coating is suppressed and the homogeneity of the surface of the inner wall and / or the surface of the internals which come into contact with the reaction mixture (and thus Influence the course of the reaction and / or the quality of the product).

The device can e.g. a pressure vessel for the production of a plastic such as for the polymerization of monomers such as vinyl chloride and its copolymers such as vinyl esters, e.g. Vinyl acetate and vinyl propionate, such as (meth) acrylic acid and its

Esters and salts such as maleic acid, fumaric acid and their esters and anhydrides such as diene monomers such as butadiene, chloroprene and isoprene such as styrene and such as acrylonitrile. These monomers can be used alone or in combination of two or more monomers.

The containers coated according to the invention are particularly effective in the homopolymerization of vinyl chloride or the copolymerization of vinyl chloride with comonomers, which e.g. Vinyl esters such as vinyl acetate or vinyl propionate or (meth) acrylic acid esters such as methacrylate, butyl acrylate, 2-ethylhexyl acrylate or methyl methacrylate or olefins such as ethene and propene or acrylonitrile, styrene and vinylidene chloride can be.

The inner wall of a polymerisation device to be coated, such as that of a pressure vessel, is made of steel, in particular of carbon steel and / or a stainless steel such as e.g. V2A or V4A.

The polymerization device is used, for example, for the production of plastics and can in particular be a pressure vessel.

The invention was made with regard to the polymerization of vinyl chloride, if appropriate in the presence of monomers copolymerizable with vinyl chloride, in the aqueous phase at a temperature between 35 and 90 ° C. under elevated pressure, in the presence of at least one free radical initiator and at least one suspending agent and / or an emulsifier is developed. This process can be carried out continuously or discontinuously because of the avoidance of the coating on the inner wall.

The temperature of the reaction mixture, in particular of the water, can be above the polymerization temperature. The temperature control in the pressure vessel or reactor takes place, for example, via external or internal heating and / or cooling circuits and / or units. By avoiding deposits on the inner surface of the pressure vessel or reactor, a significantly improved heat conduction is achieved and the effectiveness of the cooling / heating is increased.

Depending on the embodiment of the method, the reaction mixture in the container is brought to the polymerization temperature by charging part of the water of reaction as preheated water, the temperature of which is higher than the polymerization temperature, by the required amount of heat in whole or in part via the heating or cooling circuit or entirely or is introduced in part via additional heating and / or cooling units and / or in that the required amount of heat is introduced in whole or in part by the direct introduction of steam into the liquid reaction phase.

The aluminum transition metal alloy comprises at least two metals, aluminum (Al) and a transition metal (M ¹ / M ² ). It is advantageous to use a ternary, quaternary or higher alloy, the decisive factor in the choice being the temperature / pressure range in which the alloy forms the most stable quasi-crystalline phase.

The alloy comprises, for example, a compound of the general formula M0-M1-M ² , where M ° is aluminum or aluminum / beryllium; M ^{1 is} a transition metal selected from the group comprising copper (Cu), cobalt (Co), nickel (Ni), palladium (Pd) and / or platinum (Pt) and M ^{2 is} a transition metal selected from the group comprising iron (Fe ), Ruthenium

(Ru), nickel (Ni), manganese (Mn), chromium (Cr) and / or Co. For example, the alloy has a composition in which the Al content is 55 to 90 atom%, the M ¹ content is at least 5 atom% and the M ² content is the rest. Alloys are mentioned as examples, whose Al content is 60 to 80 atom%, preferably 60 to 75 atom%, whose M ^x content 10 to 30 atom%, preferably 10 to 20 atom% and whose M ² content 10 to 25 Atom%, preferably 10 to 20 atom%.

Cu and / or Ni and / or M ² Fe and / or Co is preferably used as M ¹ .

There are completely new possibilities for the continuous polymerization of vinyl chloride and thus copolymerisable monomers using the emulsion and suspension processes.

The reaction vessels and the internals are coated with a continuous, quasi-crystalline surface in a manner known to the person skilled in the art from EP 356287 and US 5433978 by CVD, PVD, plasma coating, flame spraying or other suitable processes. Any subsequent surface refinement that may be required, such as grinding or polishing, is also carried out in a manner known to those skilled in the art.

Quasicrystalline compounds represent a new type of metal alloy, they have a well-ordered crystal structure, but the crystal lattice shows no periodicity. A number of quasicrystalline compounds have now been found, all of which are basically for the

Coating surfaces of reaction vessels and their internals are suitable. Two quasi-crystalline surfaces with different compositions were examined. These were i-Al-Cu-Fe and i-Al-Ni-Co alloys, which were applied to V4A and C steel.

The invention is explained in more detail below with the aid of examples which describe embodiments of the invention.

Example 1:

In a Im ³ reactor, a flat metal plate made of V4A steel was determined, half of which was made using the PVD method with an i-Al-Ni-Co metal alloy, the composition of which was Al ₆₉ , ₈ Nii ₅ , ιCθi ₅ , _ι was coated and attached to the reactor wall. The reactor was cleared by evacuation 0 ₂ - and 40 l of water, 42 g of a polyvinyl alcohol with a viscosity of the 4% strength aqueous solution of 5 mPas and a saponification number of 280, 42 g of a methylhydroxypropyl cellulose with a viscosity the 2% aqueous solution of 45 mPas, 150 g sorbitan monolearate, 80 g of a water-insoluble polyvinyl alcohol with a saponification number of 405.

Thereafter, 350 kg of vinyl chloride (VCM) and 410 kg of water were simultaneously charged into the reactor while stirring with a stirring energy of 1.6 kW / m ³ , the temperature of the water being chosen so that an internal temperature of 70 ° C. was reached. The polymerization is started at this temperature by adding 306 g of Perkadox® 16W40 and 152 g of dilauroyl peroxide. It is stopped after 5 hours and a pressure drop of 4 bar. After emptying the reactor and rinsing the reactor surface with washing water, the sample plate was examined for PVC coating.

The coated part with the quasi-crystalline surface made of Al-Ni-Co was completely free of deposits, while the uncoated part of the test specimen was covered with a continuous layer of polyvinyl chloride.

Example 2:

In a 400 1 - pressure reactor made of the material 1.4404 an area of 10 dm2 linen with a i-Al-Cu-Fe-quasikristal- surface was coated the composition of which was determined to be Al ₆ _3/4 Cu ₂₄ Feι _2,. 6 The reactor was cleared by evacuation 0 ₂ - and 16 l of water, 56 g of a methylhydroxypropyl cellulose with a viscosity of the 2% strength aqueous solution of 35 mPas, 28 g of a non-water-soluble polyvinyl alcohol with a saponification number of 405 were charged.

Thereafter, 140 kg of vinyl chloride (VCM) and 164 kg of water were charged into the reactor with stirring with a stirring energy of 1.5 kW / m ^3, and the reactor contents were heated up via the heating / cooling jacket until an internal temperature of 56 ° C. was reached. At this temperature, 48 g of Trigonox® 423 W50 and 100 g of Trigonox® EHP W50 were charged to start the polymerization. After 4.5 hours and a pressure drop of 2 bar, the polymerization was stopped, the reactor was emptied and washed. The quasi-crystalline surface was free of deposits, the other reactor surface and all internals were covered with a continuous polymer coating, which made it necessary to clean the reactor with high-pressure water. Example 3

The procedure was as in Example 2. The reactor was made 0 ₂ - free by evacuation and 16 l of water, 56 g of methylhydroxypropyl cellulose with a viscosity of the 2% strength aqueous solution of 35 mPas, 28 g of a non-water-soluble polyvinyl alcohol were also added a saponification number of 405, 27 g of 30% hydrogen peroxide, 210 g of NaHC0 ₃ in the reactor. Thereafter, 140 kg of vinyl chloride and then 51 g of ethyl chloroformate were charged with stirring. By adding 164 liters of hot water, the polymerization temperature was set at 56 ° C. and the mixture was polymerized for 5 hours to a pressure drop of 2 bar, and the reactor was emptied and washed. The quasi-crystalline surface was free of deposits, the other reactor surface and all internals were covered with a continuous polymer coating, which made it necessary to clean the reactor with high-pressure water.

Example 4

The sleeve of the thermal sensor in an Im ³ reactor made of V4A steel was completely coated with an i-Al-Ni-Co metal alloy using the PVD method, the composition of which was determined as Al ₆ 9, ₉ Nii5, ιCθi5, o, coated and installed in the reactor. The procedure was then as in Example 1. After emptying the reactor and rinsing the reactor surface with wash water, the thermal sensor was examined for PVC coating.

The coated part with the quasi-crystalline surface made of Al-Ni-Co was completely free of deposits. Example 5

The entire surface and the internals of a 400 1 test reactor consisting of carbon steel Hl were coated with a continuous quasi-crystalline surface i-Al-Cu-Fe and the polymerization approach of Example 2 was repeated. After the polymerization reaction was complete, the reactor was emptied and opened. The entire reactor was free of deposits and could be used again immediately after rinsing with wash water.

Example 6

An i-Al-Cu-Fe was coated with a continuous, quasi-crystalline surface in a ³ reactor made of boiler steel Hl plated with stainless steel 1.4401 and the polymerization approach of Example 1 was repeated. After the polymerization reaction was complete, the reactor was emptied and opened. The entire reactor was free of deposits and could be used again immediately after rinsing with wash water.

Claims

claims

1. Device for polymerization, the inner surface (s) and / or installation (s) of which are at least partially covered with a quasi-crystalline coating.

2. The apparatus of claim 1, comprising a pressure vessel.

3. Apparatus according to claim 1 or 2, wherein the quasi-crystalline coating comprises an aluminum transition metal alloy.

4. The device of claim 3, wherein the coating comprises a compound of the general formula M ° -M ¹ -M ² , wherein M ° is aluminum or aluminum / beryllium; M ^{1 is} a transition metal selected from the group comprising Cu, Co, Ni, Pd and / or Pt and M ^{2 is} a transition metal selected from the group comprising Fe, Ru, Ni, Mn, Cr and / or Co.

5. Device according to one of the preceding claims, wherein the Al content or the Al / Be content of the coating 55 to 90 atom%, the M ^ content is at least 5 atom% and the M ² content is the rest.

6. Device according to one of the preceding claims, wherein the material of the inner surface (s) comprises a stainless steel and / or a carbon steel.

7. Device according to one of the preceding claims, which is used for the polymerization of ethylenically unsaturated compounds.

8. A process for the polymerization of vinyl chloride, optionally in the presence of monomers copolymerizable with vinyl chloride, with an initiator and / or a suspending agent and / or an emulsifier, which is carried out batchwise in a device according to one of the preceding claims 1 to 7.

9. A process for the polymerization of vinyl chloride, optionally in the presence of monomers copolymerizable with vinyl chloride, with an initiator and / or a suspending aid and / or an emulsifier, which is carried out continuously in a device according to one of the preceding claims 1 to 7.

10. The method according to any one of claims 8 or 9, which is carried out in the aqueous phase.

11. The method according to any one of claims 8 to 10, which is carried out at a temperature between 35 ° C and 90 ° C.

12. The method according to any one of claims 8 to 11, which is carried out under increased pressure.

13. The method according to any one of claims 8 to 12, wherein the initiator is a free-radical initiator.

14. The method according to any one of claims 8 to 13, wherein the reaction mixture in the device according to one of claims 1 to 7 is brought to the polymerization temperature by charging part of the water of reaction as preheated water, the temperature of which is higher than the polymerization temperature.

15. The method according to any one of claims 8 to 14, wherein the reaction mixture in the device according to one of claims 1 to 7 is brought to the polymerization temperature by the required amount of heat in whole or in part via the heating or cooling circuit and / or in whole or in part additional heating or cooling units is introduced.

16. The method according to any one of claims 8 to 15, wherein the reaction mixture in the device according to one of claims 1 to 7 is brought to the polymerization temperature by introducing the required amount of heat in whole or in part by the direct introduction of steam into the liquid reaction phase.