DE2062976A1 - Polymerization process - Google Patents

Description

The invention relates to a process for the continuous bulk polymerization of acrylic monomers such as methyl methacrylate

In known bulk polymerizations for the production of acrylic polymers As polymerization occurs along the reaction device, the polymer tends to increase in viscosity. The more viscous polymer collects along the walls of the reaction device and thereby effectively reduces the space available for the reaction device for conversion,

Further, due to the accumulation of polymer on these walls of the reaction apparatus, there is a tendency to occur of heat transfer problems. From these variable heat transfer conditions along the reaction device results unstable work. When trying to get a Maintaining an isothermal system in which the temperature is kept constant varies the rate of polymerization along the reaction device due to a

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unevenly in the direction of the reaction device length Exploitation of the initiator. The speed at which form radicals from an initiator in such a system, decreases with the consumption of the initiator as it progresses the reaction along the reaction device. These and other peculiarities that cause irregularities known methods can be determined by applying the system according to the invention, that in a simple and economical Way, an improved utilization of the reaction space Accumulation of uniform and high molecular weight polymer results, minimize or substantially eliminate.

b The process according to the invention for continuous polymerization in bulk of acrylic polymer is characterized by the fact that, *

a) a stream, the methyl methacrylate monomer and polymer syrup, the polymer containing monomer units based on methyl methacrylate mbnomeres, an initiator and a telogen, a reaction zone, the stream containing 30 to 80% monomeric components and into the reaction zone at a Temperature of 120 to 170 ° C occurs,

b) flow through the reaction zone at a flow temperature between 120 and 200 ° C and with an essentially uniform temperature rise of between

* and 30 C moved forward along the reaction zone, with

the reaction zone to essentially adiabatic conditions is held, and

c) withdraws a polymer syrup with a polymer content between 25 and 75 % from the zone.

Typically 1 to 25 % of the monomeric components are ethyl acrylate.

Preferably the one part of the reaction zone feed contains forming methyl methacrylate syrup circulatory syrup, the im can have essentially the temperature of the product stream. In

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AD-Miio '<5 2Q62976

is typically fed to the formation of the reaction zone Feed stream of polymer and unreacted monomer containing syrup feed with new cold stored Mixed monomer. In a particularly preferred embodiment, the syrup feed component is comprised of ■ essential from circulating syrup. The initiator can be chosen that it has a half-life at the reaction zone inlet temperature substantially equal to the residence time Has passage in the reaction zone. He would in this way due to the temperature rise in the reaction zone in this effectively fully utilized, and in the product emerging from the reaction zone initiator would only be in minimum quantity.

Typical initiators are tert-butyl peroxide, tert-butyl hydroperoxide, tert-butyl perbenzoate, 2,5-dimethyl-2,5-di- (tert-butylperoxy) -hexane, 2,5-dimethylhexyl-2,5- dihydroperoxide. Preferably, when tert-butyl perbenzoate, the preferred initiator, is used, at least Ο. % by weight of water is also present in the feed stream.

The amount of polymer syrup in the feed stream, preferably recycled material from the material flowing out of the reaction zone, should correspond by weight to at least 55% of the current flowing out of the reaction zone.

Other comonomers present can typically be selected from the group butadiene, styrene, ct-methylstyrene, derivatives of bicyclobutane, Choose acrylic and methacrylic acid and their esters.

In the particularly preferred embodiments, the reaction takes place in a reaction zone, so that one has the full lifetime of the initiator, but the process can also be carried out in a number of reaction zones, wherein usually: different initiators are used in each zone.

The rise in temperature should be between 10 and 30 ° C.

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The temperature of the stream emerging from the reaction end zone or reaction zone (depending on the embodiment used) should not be above 200 ° C., so that the product can remain stable. This outlet temperature of the discharge stream is preferably not more than 180 ° C., and the discharge stream preferably has a polymer content of 25 to 75 %, in particular 50 to 70 %. The product of the (depending on the embodiment used) reaction end zone or (single) reaction zone can then be subjected to high temperature and reduced pressure separately or at the same time in order to volatilize most of the monomer present in the reaction product. Preferably not more than 5 to 10% of the monomer j, based on the syrup weight, remain in the product stream after this stage. The stream can then be treated in an extraction extruder which further processes the polymer in the sense of removing further residual monomers and which at the same time extrudes the polymer in strand or sheet material form or can also press the polymer into a granulating device.

By controlling the amount of polymer syrup, preferably circulating syrup, in the feed stream the amount of heat dissipated in the reaction zone and the corresponding increase in temperature directed in the zone for a given polymer formation rate.

In the meaning used here is under

"Bulk polymerization" or bulk polymerization is the direct conversion of liquid monomers into polymers in a reaction system, in which the polymer remains soluble in its own monomer, understood - a solvent becomes in one such a system is not required -,

"continuous polymerization" means a polymerization in which over a given period of time monomer to the reactor system fed in at a steady rate and product polymer withdrawn at a steady rate, "Acrylic polymer" polymer, its main monomer component goes back to the monomer methyl methacrylate,

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"Initiator" means a chemical or chemicals that are used to induce free radicals enabled isw. or, which in a monomer-containing medium the polymer chain growth in motion set, .

"Telogen" means a substance or substances that make one grow The polymer chain ends or ends and the beginning of a new one causes or effects,

"self-scraping locomotor organs" locomotive organs, such as Stirrer, in a container of such construction that, with each revolution, part of one of two or more organs is close to it sweeps past one or more of the other organs so that every part of the organ is scraped off is, each moving member in the container is stripped in this way and also a stripping of the The walls of the container occur through the organs of motion, and "forward movement" is essentially a movement through the body entire inlet flow through the reaction zone essentially without any accumulation of polymer on the walls or surfaces the reaction device or locomotive organs, which is best achieved using "self-stripping" locomotives in the reaction zone can be accomplished.

The "flow number" means the rate at which polymer under the action of the pressure of a stamp of 9.53 mm in diameter and 3800 g in weight at 230 ° C. through an outlet opening of 2.100 mm in diameter.

The "inherent viscosity" is determined and calculated in chloroform using a Cannon-Fenske viscometer according to the equation

_TV _ In t / t . _{IV s} o — o- *

where t is the outflow time of the solution,

t is the outflow time of the solvent and C is the concentration of the solution in g / 100 ml (for the provisions described here approximately 2)

1 0 9 8 2 "δ / * 1 ~ 8 2 S

The “weight loss at 300 ° C.” - hereinafter also referred to as GV _{500 for} short - is equal to the loss (without moisture) of the polymer in wt. ^ If the polymer is kept at 300 ° C. under nitrogen at atmospheric pressure for 30 minutes.

The "free monomer" in the polymer is determined by the monomer is distilled off from a solution in acetic acid and water and titrated it with potassium permanganate in the presence of sulfuric and periodic acids.

Under "circuit" is that part of a stream in one. To understand the process that is being deducted and, after or without knowing- " older treatment, leads back to an earlier point in the process.

The "expansion chamber" means a container in which one Introduces liquid at a temperature above its boiling point is at the pressure in the container, and evaporates.

The "extraction extruder" is to be understood as a machine that conveys, heats and pressurizes material in such a way that this can be passed through a nozzle or opening. the The machine has openings in its walls so that volatile material can be removed in vapor form.

I The method according to the invention is shown schematically in FIG

Drawing shown, where stream 1 is a feed stream, Stream 2 is the discharge stream, stream 3 is the product stream for further finishing and extrusion, and stream 4 is the circulating stream and stream 5, the monomer replenishment and the monomer cycle from the finishing and extraction extruder. Typical extraction extruders (extractor extruders) are in "Modern Plastics Encyclopedia", Vol. * J5, Oct. 1968, and Vol. 46, Oct. 1969, McGraw-Hill.

Suitable self-wiping motion systems are in the publication "W-P Machines for Process Engineering, Issue Mo, 1, Continuous Machines ", No. R2284 / 68e, Werner & Pfleiderer, Stuttgart, described.

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In the following examples, when tert-butyl perbenzoate is used as initiator, at least 0.0 * 1% by weight of water is present in the feed stream.

All "parts" in the following examples are parts by weight unless otherwise specified.

Examples 1 to 5

A jacketed chamber of served as the reaction device 81.3 cm long with one of two intersecting circles of 2.5 cm spaced 3.9 cm from each other Diameter defined cross-section, within this container two common circumferentials, each other and the walls stripping screws were used, which had a two-flight training * and each thread turn its own (independent) beginning and its own (independent) end at the beginning or end of the snail.

Syrup was at the "feed end" of the reaction apparatus introduced and withdrawn at the "end of discharge". Circuit syrup, a portion of the dispensing syrup was, through a jacketed 9.5 mm pipe, into the fresh monomers, initiator and Telogen pumped back to the feed end of the reaction apparatus. The driving force for circulation through the syrup circulation line supplied a speed controllable Gear pump of 10 ecm displacement.

Uncirculated syrup from the discharge end of the reaction device was made on the "flash chamber" principle (whereby the feed line can take place through a heated pipeline) into the screws of an extraction extruder (Finishers) with non-meshing twin screw from 2.0 cm diameter introduced, evaporated monomer from the Finisher collected, condensed, mixed with virgin monomer and returned to the reaction device and that from the finisher obtained, strand-shaped, molten polymers are quenched in water and cut. ·

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The telogen in Examples 1 and 2 is tert-amy mercaptan and in Examples 3 to 5 n-buty! mercaptan.

In the table, MMA means methyl methacrylate, EA means ethyl acrylate, TAM tert-amyl mercaptan and MBM monomeric butyl mercaptan. TBP is tert-butyl perbeneoate and DHDP is 2,5 "-dimethylhexyl * 2, S-dihydroperoxide. ... ..

Regarding the measured feed syrup temperature it should be noted that that, due to the small diameter of the line, this should appear somewhat eu high »The actual Measurement of the mixture of circulating syrup and added monomer (feed Bßstrom-Teraperatur) was difficult because of the low amounts of plastinate.

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example • 1 2 3 4th - 5 - \ J
I.
J? attempt 18th 18th 11 11 22nd JSr:
.He
O Recipe to supplement the feed
MMA, kg
EA
TAM, g 32.7
1540 g
61 (like 1) 32.7
1540 g
44 (like 3)
I. 32 7
15 * 10 g
45. initiator TBP TBP TBP TBP DHDP Amount of initiator per hour 2.55 g 2.72 g 2.75 g 3.05 g 3.5 g Solids,? Leaving the reactor. syrup 53 -. 55 60 44 49 Circulation syrup, kg / hour 22.54 30.53 22.45 21.68 22.95 Product, kg / hour 2.50 2.72 2.88 2.28 2.08 Feed syrup, kg / h 27.2 35.4 27.2 27.2 27.2 Circulatory monomer, kg / hour 2.18 2.18 1.91. 3.27 2.18 _t Monomer,?, In charge 44 47 49 32 41 Monomer temperature * ⁰ C 33 28 29 34 26th Theoretical feed flow
Temperature (calculated) 143 144 134 143 170 Feed syrup temperature, mixed
sen, C (see note above) 150 149 146 146 174 Discharge syrup temperature, ⁰ C 165 163 157 170 195 Reactor screw, rpm 6.5 8.6 6.5 -6.5 6.5 Finisher temperature, ⁰ C 280 280 280 280 280 Product; Inherent viscosity 0.56 0.56 0.59 0.54 0.42 O Monomer, % 0.23 0.22 0.34 0.31 0.43 CJ) ^GV 300 1.17 1.02 1.64 1.73 4.10 CO; CJ) I
%
1

Example 6

During an experiment lasting 1 and 9 hours, a polymer with a flow rate of 2.0 g / min and 6.0 g / min at 230 ° C was produced under the following conditions:

For flow number

Monomer supplement solution, kg / hr. Circulating monomer solution, kg / hour Initiator solution in MMÄ »kg / h. Product, kg / hour
Circulation syrup, kg / hour

ψ Initiator (tert-butyl perbenzoate), g / h

n-butyl mercaptan, g / Sfcdi. Monomer solution partial temperature » ⁰ C

Syrup temperature at the reactor inlet, C

Syrup temperature at the exit ⁰ C

Coat temperature on the front half of the heak fire, ⁰ C

Temperature on the second half of the jacket - ⁰ C

Finisher temperature, ⁰ C

The product of these tests gave an inherent viscosity of} 0.56, a GV ₃₀₀ of 1.9 %, a monomer content of 0.3 % (material of Fliesszatil 2.0} or 0.46., 1.7 and 0.3 % (material with a flow number of 6.0). The clarity of the polymer was good and the material was easy to compress into shape.

The same apparatus as in Examples 1 and 2 was used.

Example 7

In another attempt, a polymer was found with an inherent Viscosity of 0.51 using 2.5 ~ dimethyl-2,5-di- (tert-butylperoxy} -hexane Cowpersol "101) as the initiator

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2.0 6.0 2.54 ^; 2.54 2.17 2.17 0.11 » 0.18 2.59 2.54 28.1 28.1 2.1 » 2.4 3.3 4.9 30th 30th 118 146 165 167 150 151 160 162 250 300

at a reactor charging temperature of 155 ° C and a discharge temperature of 175 ° C and the rest in each case Example 6 produced corresponding conditions.

The same apparatus as in Examples 1 and 2 would be used. .

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Claims (4)

Claims a) a from 50 to 80 % monomeric components and consisting essentially of methyl methacrylate monomer and polymer syrup containing polymer with a content of monomeric units derived from methyl methacrylate monomer, initiator and telogen stream of a reaction zone or the first of two or more Reaction zones feeds, with the stream ρ enters the reaction zone at a temperature of 120 to 170 ° C, b) the flow is advanced through the or each reaction zone at a flow temperature between 120 and 200 ° C. and with an essentially uniform temperature rise of between 10 and J> 0 ° C. along the zone or zones and the or each reaction zone is opened maintains essentially adiabatic conditions, each initiator being fed in separately when two or more reaction zones are used, and c) withdraws polymer syrup with 25 to 75 % polymer from the zone or the last zone. 2. The method according to claim 1, characterized in that ethyl acrylate is used as 1 to 25% of the monomeric components in the feed stream. J3. Method according to claim 1 or 2, characterized in that that the polymer syrup in the feed stream is essentially from the product stream exiting the reaction zone syrup recirculated in the cycle begins. 4. The method according to one or more of claims 1 to j5, characterized in that one works in a single reaction zone. - 12 - 109826/182 5