DE1091329B - Process for the production of improved copolymers from styrene and methyl methacrylate - Google Patents

Description

GERMAN

Styrene and methyl methacrylate are so far after conventional processes, such as in bulk, in solution and in aqueous emulsion, copolymerized. Usually it is stated that the copolymers have properties which are between those of the corresponding Homopolymers lie. The already known copolymers of styrene and methyl methacrylate however, are molecularly inhomogeneous and inhomogeneous, which means that an ordinary copolymer contains polymeric molecules of considerably different types. Distinguish such molecules by both the proportion and the arrangement of the polymer-bound monomer output units as well as the length and molecular weight of such molecules. In many cases there is the inconsistency and the inhomogeneity of the mixed polymerizate products recognizable by cloudiness or fogging in the products.

It has now been found that novel, unusually uniform and homogeneous copolymers are produced can be if styrene and methyl methacrylate under certain conditions specified later are copolymerized. There is another unexpected advantage of these new copolymers in that their physical properties, especially their tensile strength, clarity, ductility and deformation properties, are particularly good. The new copolymers are clear, hard and thermoplastic Compositions that can be shaped and deformed by methods commonly used for polystyrene or polymethyl methacrylate plastics used, such as compression molding, injection molding, extrusion, hot molding, Machining, welding, etc.

The new copolymers are produced by a homogeneous liquid mixture of monomeric Styrene, monomeric methyl methacrylate and their copolymers at a practically constant temperature is heated, while additional amounts of the monomeric styrene and the monomeric methyl methacrylate dem Mixture are supplied, whereby a constant ratio of monomeric styrene to monomeric methyl methacrylate and maintaining a constant ratio of the same to the copolymer in the mixture will.

The essential and decisive requirements of this new procedure are firstly the uniformity of the liquid polymerization mixture, secondly constant composition of the polymerization reaction mixture and thirdly, constant polymerization conditions.

It is particularly recommended that the copolymerization of styrene and methyl methacrylate in a single phase liquid mixture and with the exclusion of immiscible solid and liquid components through-

improved copolymers

made of styrene and methyl methacrylate

Applicant:

The Dow Chemical Company,
Midland, me. (V. St. A.)

Representative: Dr.-Ing. H. Ruschke, Berlin-Friedenau,

and Dipl.-Ing. K. Grentzenberg,
Munich 27, Pienzenauer Str. 2, patent attorneys

John Lester Lang, Midland, Mich.,

Clifford Jones, Linwood, Mich.,

and Arthur Foster Roche, Freeland, Mich. (V. St. A.j, have been named as inventors

respectively. Non-polymerizable, miscible liquid diluents can be used provided that they are practically inert, e.g. H. the interpolymerization not affect. Such diluents are e.g. benzene, toluene, xylene, ethylbenzene, Chlorobenzene, cumene and methyl ethyl ketone, which have a smaller proportion, d. H. no more than 40 and preferably 0 to 30 percent by weight of the total reaction mixture, provided that the Proportion of such constituents in relation to that of the other constituents in the polymerization mixture practically is kept constant.

The monomeric styrene and the monomeric methyl methacrylate can be in the reaction mixture in any ratio between about S: 95 and 95: 5 parts by weight. The ratio in which the monomers Combine constituents to form a mixed polymer molecule if the starting monomers are in a certain proportion are present, can easily be determined in a known manner from the respective polymerization rates be calculated. Conversely, the ratio of the starting monomers required for the production of a particular copolymer product must exist, can be calculated from such conversion speed data. Means and Procedures for such calculations are detailed in the book "Copolymerization" by Turner Alfrey, Jr., John J. Bohrer and H. Mark, published 1952 by Interscience Publishers, Inc., New York.

In the claimed method, the proportion of

Copolymer constant in the reaction mixture

and relatively low, d. H. at a constant

Value of about 10 percent by weight of the total Gk-

009 628/440

3 4

Mix up to about 60% of the total weight of the mono starting materials at controlled speeds

mers and the copolymer, held. Implementation zone, for intensive mixing in the

The copolymerization is equating zone with practically, for regulating the temperature of the constant temperature between room temperature and the mixture in the reaction zone, for withdrawing a about 25O ⁰ C, particularly 100-190 ⁰ C, transit 5 part of the reaction mixture with one of the feed Professional . At lower temperatures, the molecular products corresponding to the starting materials will exist at a higher speed but at a lower speed. In this way, the speed can be obtained, whereas higher temperatures easily keep constant at higher conversion conditions; They can be determined by means of preliminary experiments with low molecular weight polymerization rates.
Deliver products. io The resulting copolymer is from the

The mixture on the polymerization reaction mixture separated in any manner, e.g., by Exerted pressure is of no great importance, but is intended to precipitate in a liquid that is responsible for the monomers at least be dimensioned so that the constituents of the substances are a solvent for the copolymer Mixtures are in the liquid phase. Anyone can do it. The polymerization mixture becomes preferentially available Pressure can be used. 15 wisely decomposed by heating under reduced pressure,

Although to activate the interpolymerization whereby the volatile constituents are evaporated and

Heat alone is sufficient to accelerate the copolymer as a non-volatile residue

Implementation of soluble catalysts are added. remains behind.

Suitable catalysts are those that free radicals, of course, the properties of the produce, so organic peroxides and hydroperoxides, 20 copolymers, among other things from the quantity z. B. Benzoyl peroxide, cumene hydroperoxide and di-tert. ~ Ratio of polymer-bound styrene and methylbutyl peroxide, and the azo catalysts, e.g., α, α'-Αζο-methacrylate and of the average molecular bisisobutyronitrile. You use them in an amount up to weight determined. The physical properties of the New, uniform copolymers up to about 1 percent by weight of the reaction mixture are usually better on, being a constituent of the implementation 25 as those of known non-uniform mixed mixtures and their proportion during the mixed polymerizates with the same average monopolymerization must be kept practically constant. meren chemical proportions and the like

Various methods are suitable for equal-solution viscosity.

permanent composition and polymerization conditions. The term "solution viscosity" as used here is intended to

to secure. 30 is the viscosity of a solution of 10 percent by weight of the

According to one of these methods, for example, the reaction of copolymer in toluene at a temperature of batches with a relatively small charge 25 ° C is specified in centipoise, which is determined according to the ASTM Veraus a mixture of styrene and methyl methacrylate drive D 703-49 T and in "American started to heat these to polymerization temperature, Society for Testing Methods 1955 Standards", p. 18 (e), the temperature kept constant and the progression 35 is described. The solution viscosity corresponds to that of the polymerization observed. When the mixed polymer molecular weight in relation to the higher merizate content of the mixture has reached the desired level, e.g. viscosity values for higher molecular weight polymers 25 percent by weight, the mixture is charged with and, conversely, lower viscosity values with lower additional styrene and methyl methacrylate. The molecular polymers are observed.
The composition of the mixture can be determined, 40 The tensile strengths of the new copolymers are taken from time to time by taking a sample and are analyzed analytically much higher than those of known copolymers. The rate of addition of styrene and methyl methacrylate of the same each monomer is then adjusted so that the average chemical composition and the desired constant composition of the reaction have the same solution viscosity, while that of the mixture remains unchanged. However, this process is somewhat cumbersome from 45 to 85 percent by weight of methyl methacrylate in the mixture, since the absolute addition rate polymer has an uppermost value. The highest tensile strength of the monomers for maintaining a consistency value is usually obtained when the constant mixed polymer content has to be increased, the solution viscosities at least between about 10, if the amount of the accumulated conversion and 15 cP. The minimum load increases within this range. The small amount of the solution viscosities also remains, the lower values initially formed non-uniform copolymers correspond to copolymers with higher uppermost tensile strengths in the mixture and contaminates, albeit progressively and the higher viscosities of the lower uppermost, progressively lower amounts, the later forming tensile strengths, being the different supreme unified product. Tensile strengths of the copolymers on the chemical

An improvement in the above process composition of the copolymer, as above wise consists in the fact that the neglect, which takes place in batches, is to be traced back. For any such mixed driving The tensile strength values at Löwird are converted into an uninterrupted process. as soon as a suitable amount of the conversion viscosities is above the lowest minimum values charge has accumulated. With such a change, the range is between about 10 and 15 cP, as just mentioned drive a proportion of the homogeneous conversion 60 is described, practically constant.

Mixture with progressive addition of the monomers. H. continuously deducted, at a rate of the minimum values in the just specified If both the total amount of the reaction area, the tensile strength values of the interpolymer blend fall as well as the ratio of the monomers and sate. But even with solution viscosities in that the proportion of the mixed polymer contained therein ranges from 5 to 7 to 10 to 15 cP, the tensile strength are constant being held. The first formed poly- keitswerte the new copolymers, in particular This removes merisat from the system. in the composition between 50 and 85 weight

A particularly practical embodiment of the above percent methyl methacrylate, at least as good as that The method described is carried out in a simple system with the best achievable tensile strength values of known mixtures, those from devices for feeding the 70 polymers and much better than the tensile strength values

known copolymers with the same solution viscosity values.

The extensibility values of the new copolymers are also significantly higher than those of known copolymers made of styrene and methyl methacrylate with the same average chemical composition and the same solution viscosity, being in the range of 50 to 85 weight percent methyl methacrylate have an uppermost value in the copolymer. Copolymers of about 65 percent by weight Methyl methacrylate and about 35 percent by weight styrene, the solution viscosities of about 15 and have more cP, show "necking" as an unexpected behavior when test bars are subjected to a tensile strength test be pulled out. Such rods can be repeatedly double bent and then stretched without breaking.

The relationship between the tensile strength and the solution viscosity of the new copolymers is has already been mentioned above. When the copolymers are processed by means of heat, as in injection molding they are particularly beneficial. In contrast to the deformation temperatures, which at Usual copolymers are required, the new copolymers, which have the same chemical Composition and physical properties - e.g. tensile strength - are much lower Temperatures are deformed.

The regulation of the solution viscosity of the new copolymer products takes place easily by a suitable choice of the polymerization conditions. The solution viscosity of the copolymer is generally inversely related to the temperature of the copolymer. When styrene and methyl methacrylate in the absence of non-polymerizable liquid diluents and of catalysts in the presence of a constant proportion of the copolymer of about 10 to 60 percent by weight of the mixture and are thermally copolymerized at a constant temperature, the Solution viscosity of the copolymers with the copolymer conversion temperature roughly in the following relationship:

Interpolymerization
conversion temperature Solution viscosity 13O ⁰ C 30 to 50 cP 140 ° C 20 to 40 cP 150 ° C 15 to 30 cP 160 ° C 10 to 20 cP 170 ° C 10 to 15 cP 180 ° C 5 to 10 cP

The solution viscosity of a copolymer produced at a certain temperature is shown in to a certain extent on the respective proportions of styrene and methyl methacrylate in the reaction mixture determined, the solution viscosity of the copolymer at higher proportions of methyl methacrylate usually increases.

If in the reaction mixture catalysts and / or non-interpolymerizable liquid diluents and especially those diluents are used which also act as chain transfer agents are the solution viscosity values of the copolymers at each polymerization temperature lower than those just shown, the degree of degradation depending on the type and proportion of the added Catalyst and / or diluent is determined. In the same way allows the use of added catalysts and / or liquid Ver

thinners the use of a lower constant interpolymerization temperature in order to achieve a Produce mixed polymer with the same solution viscosity. Let it be repeated that the rate of polymerization also directly from the copolymerization temperature and from the catalyst concentration is determined and that it is inverse to the concentration of the inert liquid diluent behaves in the polymerization mixture.

ίο The new copolymers are thermoplastic solid Substances that can be converted into usable objects, such as device housings and panels, rain capes, Motor vehicle taillights, medallions, devices, shaped letters and figures for indicators, Windows, light scattering devices and counting boards and the like, can be shaped and deformed, their usability and value is increased by the advantageous physical properties of the new copolymers. The copolymers can be prepared according to known

ao drive with pigments, stabilizers, lubricants and other additives are compounded.

Styrene and methyl methacrylate were copolymerized in several experiments according to the process according to the invention, those in devices A, B, C and D of different capacities continuously were carried out.

Devices were used to feed a liquid mixture of the liquid monomers and optionally an inert liquid diluent and / or a catalyst at a certain rate. The polymerization vessel consisted of a coil connected to a pump for quickly circulating the contents of the coil back into a closed circuit. The vessel was also provided with means for maintaining a predetermined constant temperature in the reaction zone. At a point in the queue furthest from the feed point, a portion of the returning polymerization mixture could be withdrawn at a rate corresponding to the feed rate in such a way that sufficient pressure was exerted on the polymerization mixture in the reaction zone maintained and thereby the mixture was kept in the liquid phase. The withdrawn portion of the polymerization mixture was fed into a vacuum evaporator in which the unreacted monomers were evaporated off under reduced pressure, by heat, the polymer as a residue, which is about _1/0 ° containing residual volatile material was incurred. At intervals, samples were taken from the polymerization mixture and from the polymer, and these were analyzed and investigated using customary methods.
The coils in these containers had the following properties:

Container A:

3.17mm tube, 6.8mm inner diameter; Inconel (alloy of 80 percent by weight Ni, 14 Cr, 6 Fe;

see German patents 332 811, 51214); Length 3.4 m.
Container B:

Stainless steel pipe with a diameter of

25.4 mm; Length 2.5 m.
6g container C:

Aluminum tube with a diameter of 63.5 mm; Length 2.1 m.

Container D:

Stainless steel pipe with a diameter of 31.8 mm; Length 1.7 m.

example 1

Two series of polymerizations - namely, the one at a temperature of 14O ⁰ C and the other at a temperature of 160 ⁰ C - were carried out in vessel A. Each series consisted of several tests, with each test changing the proportions of styrene and methyl methacrylate contained in the feed mixture. No catalyst or inert liquid diluent was added to the reaction mixture. Each experiment was continued until equilibrium was reached, after which samples were taken and examined.

Table I shows the proportions of styrene and methyl methacrylate used in the feed mixtures in percent by weight, the feed rate of the monomer mixture in grams per hour, the proportion of polymer in the polymerization mixture in percent by weight and the properties of the polymer. The composition of the polymer is given in percent by weight of the chemically bound methyl methacrylate; the remainder of each polymer is therefore chemically bound styrene. The chemical composition of the copolymers was calculated from information obtained by elemental analysis of carbon and hydrogen and / or from infrared absorption spectra. Due later experiences the specified values at the high molecular weight Methylmethacrylätmischpolyrnerisaten are likely to be about 3 to 5 ° / _s and at niedermolekularefi Methylmethacrylatmischpölymerisaten by about 5 to 10% too low.

In Table I, the intrinsic viscosity values of the polymers in methyl ethyl ketone (MEK) at 25 ⁰ C are given. These values are characteristic of the molecular weight of the polymers and were determined according to the standard method by determining the reduced specific viscosities at various lower concentrations of the polymer in a solution of methyl ethyl ketone and plotting the reduced specific viscosities as a function of the concentration in grams per deciliter and this function was extrapolated to the value zero, so that the intrinsic viscosities in grams per deciliter were obtained.

Tensile strength and ductility were measured with test rods which had an intermediate part 50.8 mm long with a cross section of 3.17 × 6.35 mm. These test bars had been injection molded at a temperature of about 28 to 42 ° C. above the "insufficient filling temperature" in a 28.3 g Watson-Stillman injection molding machine at a molding pressure of 700 kg / cm ² . The expression "insufficient filling temperature" is intended to denote the temperature at which, during injection molding under a certain molding pressure, the injected plastic just does not yet fill the mold. The bars were tested on a Dillon Model K tensile tester at a tensile strength of 6.35 mm per minute. The tensile strength values obtained with such test bars and by this method, which are reported in Table I, are probably too high ^{by 35 to 70 kg / cm 2.} The percent elongation to break elongation values are likely to be reliable.

The heat distortion temperature values given in Table I are obtained by one method reported by G.A. Heirholzer and R. F. Boyer in ASTM Bulletin, No. 134, May 1945, p. 36 has been.

All of the copolymers of styrene and methyl methacrylate given in Table I were clear and translucent.

Table I.

f styrene, ⁰ /,

Feed mixture hylmethacrylat j _Met, · /,

Polymerization at 14O ⁰ C

Feed rate, g per hour

Polymer in the reaction mixture,%

Polymer composition, ° / ₀ methyl methacrylate limiting viscosity in methyl ethyl ketone at 25 ⁰ C, dl / g ...

Tensile strength, kg / cm ²

Extensibility,%

Heat distortion temperature ^{, 0 C}

Polymerization at 16O ⁰ C

Feed rate, g per hour

Polymer in the reaction mixture, ° / ₀

Polymer composition,% methyl methacrylate Limiting viscosity in methyl ethyl ketone at 25 ° C, dl / g ...

Tensile strength, kg / cm ²

Extensibility,%

Example 2

A number of experiments were carried out according to the general procedure described above, but under the Conditions and with the results given in Table II. For experiments 1 to 17 no catalyst was used.

Table II shows the composition for each experiment the weight percent of the charge styrene, methyl methacrylate and ethylbenzene, if used was reported based on the total charge. The table also shows the chemical composition of the copolymer obtained in

95 65 50 35 5 5 35 50 65 95 256 271 224.6 214 17.8 16.4 18.9 16.1 6.5 27.5 45.0 55.2 0.524 0.579 0.691 0.698 566 640 777 790 3.0 3.5 4.8 5.1 82.6 84.9 82.5 84.2 392 281.5 299 409 421 30th 32.5 25.3 26.5 11.7 7.0 34.2 46.2 56.2 84.2 0.433 0.543 0.494 0.561 0.785 438 714 770 805 763 1.8 3.9 4.6 4.9 4.5

0
100

172
10.4
100

0.827 632

3.4

223
11.0
100

0.618 632
3.4

Weight percent indicated. These values are for styrene by ultraviolet absorption spectrum analysis has been determined, the difference being the corresponding value for methyl methacrylate. It is believed, that this method is more accurate, reproducible and reliable than analysis by chemical methods or infrared absorption method.

The table shows the container used in each experiment, the polymerization temperature, the rate of charge of the monomer mixture, the withdrawal rate of the reaction mixture (in kilograms Polymer indicated per hour; the deduction

speed of the entire reaction mixture corresponds to the feed speed), the proportion of Polymer indicated as percent by weight of the reaction mixture and the rate of polymerization (this as the formation of the polymer in percent by weight of the container capacity per hour).

As already described above, the withdrawn portion of the reaction mixture in the heat and in Vacuum evaporated for the purpose of obtaining the polymers.

The table also shows the properties of the polymers. As described above, the solution viscosity is the viscosity of a solution of 10 percent by weight of the polymer in toluene at 25 ° C. in cP. The melt viscosities were determined in poises at a shear force of 700,000 dynes per cm ² using a "caplastometer" using a method described by HJ Karam, KJ Cleereman and JL Williams in Modern Plastics, Vol. 32, No. 7, p. 129 (1955). The heat distortion values were measured with a measuring device described by GA Heirholzer and RF Boyer in ASTM Bulletin, No. 134, May 1945, p.37. Notch toughness values were determined in foot-pounds per inch of notch using ASTM method D-256-56 (Izod method).

The tensile strength and elongation values were determined with test bars which had a 101.6 mm long central section with a cross section of 3.17 x 12.7 mm. These test bars were injection molded at a temperature about 14 ° C. above the "insufficient filling temperature" in a 28.3 g Watson-Stillman injection molding machine at a molding pressure of 700 kg / cm ² , the actual Mold temperature is given in the table. The bars were examined with an "Instron" tester at a crosshead speed of 6.35 mm per minute, the elongation being measured over an original length of 50.8 mm with an elongation device (Baldwin-Lima-Hamilton PS-6M). It is believed that the test bars made and tested by this method will give the most accurate, reproducible, and reliable results.

All of the copolymers of styrene and methyl methacrylate given in Table II were clear and translucent.

In Table II, certain tests (14 to 17 inclusive) have also been included, which the production of homopolymers of styrene and methyl methacrylate in the same device and after practically show the same process, so that the results obtained in this way with those of the copolymers can be compared which have been produced by the method according to the invention. Instead of ethylbenzene (Experiment 13), another miscible, liquid diluent, its The type and amount described above can be used with the results reported. These attempts can also lead to the results given with catalysts (see above).

Table II

Attempt no.

I 5 I.

Composition of
Charge, weight percent

Styrene

Methyl methacrylate

Ethylbenzene

Polymer composition,
Weight percent

Styrene

Methyl methacrylate

Polymerization

container

Temperature, ° C

Monomer feed rate, kg / hour

Polymer discharge rate, kg / hour.

Amount of polymer, percent by weight of the reaction mixture

Polymerization rate, ° / "per hour

Physical Properties

Solution viscosity, cP

Melt viscosity, poise ..
Refractive index (25 ° C)

Mechanical properties

Mold temperature, ° C

Tensile strength, kg / cm ²

Extensibility,%

Notch toughness, foot-pounds /
inch (Izod)

Heat distortion temperature, ° C,

80 20

74 26

140

1.95 0.34

17.5 24.0

22.0 11625

269 604 3.1

0.39 88

70 30

32

D 160

1.82 0.9

50.2 65.2

10.9

232 548 1.9

0.21

4160 1.5627

60
40

58
42

141

1.61
0.34

19.0
21.5

18.4
30000

283
672
3.6

0.48
87

50
50

51
49

C.
170

7.5
4.53

60.0
59.0

10.5
18000

260
630
2.5

0.30
86

50
50

51
49

C.
163

7.7
3.85

50.0
50.0

14.2
8000

269
675
3.0

0.42
86

50 50

51
49

144

1.83 0.48

22.1 28.6

30.2 40 800 1.5461

291 692 3.8

0.43 87

40 60

44 56

140

1.67 0.268

16.1 19.0

40.1 1.5363

321 692 3.9

0.51 91

C 180

3.95 2.36

60.0 30.6

7.3 4340 1.5303

263 560 2.7

0.23 84

009 628/440

Table II (continued)

10 30th
70 12th Try
13th no.
14th 15th 16 30th
70 36
64 20th
80 8th
77
15th 100
0 100
0 100
0 36
64 C.
163 28
72 17th
83 100
0 100
0 100
0 C.
178 7.95 B.
140 C.
170 D.
160 B.
150 C.
140 11.3 3.62 1.11 3.98 2.72 1.6 4.9 5.0 45.5 0.177 1.36 0.685 0.505 1.95 46.0 47.0 15.7 34.0 39.8 31.1 39.4 65.0 17.0
26,000
1.5303 12.4 17.6 48.8 35.4 25.0 10.5
1.5303 269
705
8.4 40.4 11.9
30 250
1.5100 9.0
1.5910 19.7
3530
1.5910 24.8
4600
1.5910 255
710
3.5 0.55 305
695
4.0 302
707
4.5 210
300
0.9 232
488
1.7 263
502
1.2 0.28 88 0.51 0.40 0.18 0.42 0.44 - 93 86 83 85 83

Composition of
Charge, weight percent

Styrene

Methyl methacrylate

Ethylbenzene

Polymer composition,
Weight percent

Styrene

Methyl methacrylate

Polymerization

container

Temperature, ° C

Monomer feed rate, kg / hour

Polymer discharge speed, kg / hour ...

Amount of polymer, percent by weight of the reaction mixture

Polymerization rate,% per hour

Physical Properties

Solution viscosity, cP

Melt viscosity, poise

Refractive index (25 ⁰ C)

Mechanical properties

Mold temperature, ⁰ C

Tensile strength, kg / cm ²

Extensibility,%

Notch toughness, foot-pounds /
inch (Izod)

Heat distortion temperature ^{, 0 C}

Claims (2)

Patent claims: 1. A process for the preparation of improved copolymers of styrene and methyl methacrylate, characterized in that a homogeneous, liquid reaction mixture consisting essentially of (a) a monomeric component consisting of styrene and methyl methacrylate in a practically constant ratio of 5 to 95 parts by weight of styrene and from 95 to 5 parts by weight of methyl methacrylate, the monomeric part making up a total of 100 parts by weight, (b) the copolymer of the monomers in an amount which is practically a constant value of 10% by weight of the total reaction mixture up to 60% by weight of the combined mixtures of the monomeric part and of the copolymer, (c) a non-polymerizable, inert, miscible, liquid diluent in an amount that corresponds to a practically constant value of 0 to 30 percent by weight of the total reaction mixture, and (d) a free radical-generating catalyst in an amount that corresponds to corresponds to an approximately constant value of 0 to 1 percent by weight of the total reaction mixture, in a polymerization zone 0 100 B 178 0.5 0.195 39.7 17.8 insoluble 1.4910 300 491 3.5 practically constant polymerization temperature is heated, so that the styrene and the methyl methacrylate are copolymerized, and that the respective amounts of the constituents of the reaction mixture are practically constant on the above Values are maintained by continuously adding further amounts of components (a), (c) and (d) fed in as required and mixed intensively with the mixture, and of at least one Part of the reaction mixture isolated the resulting copolymer of styrene and methyl methacrylate will. 2. The method according to claim 1, characterized in that the total amount of the reaction mixture is kept practically constant in the polymerization zone by continuously part of the obtained mixture withdrawn and from the withdrawn part the copolymer of styrene and Methyl methacrylate is isolated. Documents considered: U.S. Patent Nos. 2137393, 2321759, 2521754, 2537031; Brief handbook of polymerisation technology by Franz Krczil, Vol. II (1941), pp. 145 to 147. © 009 628/440 10.60