DE1259577B - Process for the production of graft copolymers - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

Number:
File number:
Registration date:
Display day:

C08f

C08d

German KL: 39 c - 25/05

1259 577
R38061IVd / 39c
4th June 1964
January 25, 1968

The invention relates to a process for the preparation of graft copolymers by polymerization of a 2- to 3Q ° / _o solution of a natural or synthetic rubber in a vinyl aromatic monomer, or a mixture thereof with acrylonitrile, optionally in the presence of 3 to 30 weight percent, based on the total weight of the Mixture, an inert diluent. This process is characterized in that a reaction mixture is used from which water and acidic constituents have been removed by distillation before the start of the polymerization.

The process according to the invention can be used to produce high-impact polystyrene resins, which also have excellent melt flow, strength and surface properties.

It is known to use modified rubbery polymers from vinyl aromatic compounds such as styrene, Methyl styrenes and the like. with various vulcanizable, d. H. to produce unsaturated rubbery materials. Among the known methods for Manufacture of such polymers include block, emulsion, and suspension polymerization, the present The invention relates to a further development, the block polymerization process.

It is known that in bulk polymerization processes, including those in those in the manufacture of high-impact polystyrenes, a small amount of an inert solvent is also used contamination of the end product is a significant problem. .

It has been found that this contamination of the end product can have various causes, but is based in particular on the presence of undesirable constituents in the monomer, inert Diluent and / or the rubbery material used for the graft polymerization will. The impurities are not only harmful in the products as such, but often also react with the reaction apparatus, so that the apparatus parts are subject to corrosion discolored and dirty polymers result. Otherwise, as a result of such contamination good polymer may be viewed as inferior, whereby the Significantly increase the cost of producing an impact-resistant polymer of sufficient quality.

These disadvantages are avoided in the method according to the invention. This process is characterized in that a reaction mixture is used from which process for the preparation of before the start of the polymerization
Graft copolymers

Applicant:

Rexall Drug and Chemical Company,

Los Angeles, Calif. (V. St. A.)

Representative:

Dipl.-Ing. K. Lengner, patent attorney,

2000 Hamburg 26, Jordanstr. 7th

Named as inventor:
Barna Toekes, Oakland, NJ;
Michael Erchak Jr., Ridgewood, NJ;
Frederick Elias Carrock, Wyckoff, NJ
(V. St. A.)

Claimed priority:

V. St. v. America June 24, 1963 (290 202) ■

Water and acidic components have been removed by distillation.

The method according to the invention is particularly suitable for improving the impact resistance properties of polystyrene. Furthermore, the polymerization reaction and the properties of the accurately manufacture polymers by applying controlled anhydrous conditions and incorporating them Control and influence defined amounts of an alkyl aromatic hydrocarbon.

In a preferred embodiment, a reaction mixture is brought to the polymerization, the water content of which has been reduced to less than 10 parts per million.

In the preferred embodiment of the invention In the process, the inert diluent is preferably from the beginning to the end of the polymerization reaction present. It has been shown that a particularly suitable inert diluent an alkyl substituted benzene with at least

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i 259 577

The process steps described above can be carried out continuously or batchwise it is also possible to continuously carry out a combination of individual process steps lead, while the remaining process steps are carried out in batches.

The use of ethylbenzene as a diluent in the process according to the invention enables excellent control of the reaction of an alkyl group containing at least two carbon atoms, or at least two alkyl groups,
which contain one or more carbon atoms,
which is liquid at room temperature is used
can be. The inert diluent has
preferably a boiling point above 110 ^° C., most preferably
between 130 and 200 ⁰ C. Examples of such compounds are ethylbenzene, diethylbenzene, methylethylbenzenes and xylenes, such as. B. paraxylene, especially ethylbenzene. In the further description io temperature ^ slight heat dissipation as well as slight

the present invention is always ethylbenzene handling of prepolymer and final polymer

mentioned as a diluent. merisatmischungen, so that if the

The process for the production of rubber modification products with essential conditions for the invention

fied polystyrenes according to the present invention - excellent color and physical feel can also advantageously be carried out in such a way as to obtain chemical and chemical properties

that a graft polymerization of the monomeric styrene will be.

and / or α-methylstyrene in the mass, d. H. in ab- The amount of inert diluent used, absence of additional inert diluent, is between 3 and 30 percent by weight, average, is made. based on the total weight of the reaction mixture.

It has been found that when carrying out 20 it is preferably not less than about 5%

of the present invention of crucial ■ (especially for approaches with a low content of

It is important that all reactants, diluent rubber-like material, e.g. during production

medium and additives of various kinds and for medium impact-resistant polystyrenes) and no more

various purposes anhydrous and essentially than 25% (especially for approaches with high must be free of corrosive residues, with 25 content of rubber-like material, e.g. B. Pre

these conditions are used in particular for the monomer, mixture).

the inert solvent or diluent To carry out the process, first

and the rubbery material, which is a mixture of about 70 to 98 percent by weight

lying method are used, the vinyl aromatic component, about 2 to have to. It is therefore when carrying out the 30 30 weight percent of the rubber-like material,

Driving the present invention, it is essential that which in the preferred embodiment of the

before the initiation of the polymerization reaction, a process according to the invention from linear cis-

Process stage for removing the water is polybutadiene, as a second component as well

is switched. This ensures an additional 3 to 30% ethylbenzene, based on the

that any water present as well as corrosive 35 total weight of the reaction mixture, to a

sive residues, e.g. B. acidic ingredients, mixed together from the solution. If necessary, can

rubber-like material before the formation of the poly- heat applied to the full

be removed. To achieve solution of the constituents. Some or

The method according to the present invention includes all additional ingredients, if any

can be carried out as follows: The reaction 40 to be added are then added to the

participants, e.g. B. styrene or styrene and acrylonitrile mixture added. The like additions

(as well as in some cases smaller amounts of a-Me- include agents to regulate the chain length,

ethylstyrene), optionally ethylbenzene, the rubber initiators, plasticizers, antioxidants and others

like materials and the additives are used in stabilizers as well as other materials which are used in

one or more reaction vessels, in which 45 per se known manner during polymerization reactions

also the dissolution of the rubbery material to improve the properties of the end product

is made, mixed. Subsequently will be used.

the mixture with agitation in the kettle or styrene and acrylonitrile are added as monomers Boilers are heated and the polymerization is used together with 2 to about 20% rubber, catalytic or thermal introduction up to a 50 so the acrylonitrile can be determined in amounts up to 35 weight Point led. In this under agitation percentage, based on the total monomer mixture, carried out first polymerization stage will be used. Up to 20 percent by weight of the rubber-like material precipitated and obtained styrene in the above mixture can agreed critical properties. In the following to improve the softening point and the or in the second polymerization stage, the partial heat resistance is replaced by oc-methylstyrene Mixture without noticeable bottom.

further polymerized movement. In the second process stage, the polymerization is practically carried out to remove the water during the end of the process. The mixture from the polymerizing or mixing stage, the ethylbenzene (3 to 30 GeMaterial and any weight percent used, based on the total mixture), thinner (ethylbenzene) is added in further steps before the batch is heated. Process stages worked up, with the dilution finally the mixture is transferred into the prepolymer and any non-conversion vessel present and removed or volatile components are removed under vacuum. Temperatures heated from about 75 to 9O ⁰ C; In conclusion, the volatiles 65 temperature is maintained until everything is before

freed polymer melt extruded or with other suitable aids in their final physical form transferred.

existing water has been removed using suitable distillation devices provided on the apparatus is. In this stage of the process are simultaneous

5 6

volatile acidic residues, such as HCl, which may be present in the further polymerization stages

Rubber component, e.g. B. styrene-butadiene-Kau- can be connected.

chuk, may have been formed or may be present, once the polymerization reaction removes the desired. A mixture is removed, which has reached the degree of completeness, the styrene (or styrene and acrylonitrile), ethylbenzene, 5 mixture is subjected to a further process stage, consists of water and volatile acidic residues. in which ethylbenzene and other, if appropriate, then any volatile constituents present, including vacuum, are removed and the mixture with modi possibly unreacted styrene or other indicators, plasticizers and other selected vinyl aromatic compounds are removed. Admixtures. It is also possible to use an io. The hot polymer is then extruded or in small quantities, e.g. B. about 2 ° / ₀ , benzene from the starting point to add another suitable way to the finished resin mixture, so that water and acidic return product are worked up.

stand as an azeotropic benzene-water mixture while it is determined by experimental investigations

removed after distillation. been asked that the presence only

The same procedure can also be used, 15 minute amounts of water during the polymer

if the process does not use ethylation to form black and dark-colored

benzene, d. h leads as block polymerization only with mono-colored particles in the product. It is also

merem styrene or styrene and acrylonitrile, which in that possible due to the presence of water

liquid form (with α-methylstyrene partly- dirt and other undesirable impurities

can be used instead of styrene) 20 can be dragged into the end product,

is carried out. It is an essential feature of the present

The polymerization is initiated by heating the invention that the total water content in the mixture with sufficient agitation on the reaction mixture is lowered as much as possible about 60 to 140 ⁰ C, preferably in a kettle, preferably below 10 parts per million, um or kettles (prepolymerization kettle) , d ^; e of the 25 dirt-free polymers from much better kettles in which the polymerisation was completed to produce color. Which is usually found in styrene-buta, are separated. In the acidic mixtures present according to the process diene rubber produced by emulsion polymers of the present invention contemplated, temperatures of at least residues dissolving in the styrene monomer should reach 60 ° C in the prepolymerization stage. 30 and are essentially during the vacuum-The polymerization proceeds in this stage up to distillation (pressure evaporation stage) or during a certain degree; preferably the azeotropic distillation is removed,
a degree of conversion of the monomer (s) of Without wishing to limit the present invention to a theory which is specific to about 10 to 45 ° / ₀ , based on the total conversion, is achieved. The necessary movement in the prepolymer, assuming one of the possible factors for the meiization stage, is to be achieved by stirring. In addition, it is necessary to ensure that the corrosive action of the water on the reaction is cooled in the presence of water, since the polymerisation is an exothermic reaction seen at least on some surfaces of the apparatus. In the absence of this, it must be more sufficient. Even very small amounts of water, cooling can lead to local overheating and un- 40 z. B. 50 parts per million, result in the formation of a desired temperature rise. Unconfined no longer marketable and discolored Protrolled temperatures in this process stage ductile. The acidic residues, even if they are able to form a product with an undesirable essence in very small quantities, promote a molecular weight distribution and / or undesirable discoloration of the polymer. Water can on paid gel structure, z. B. crosslinked materials, 45 rich places get into the reaction mixture, lead. so that it is considered particularly advantageous

The prepolymerized mixture is then transferred directly to the water from the reactant just prepared in the second polymerization vessel, in the mixture immediately before the start of the polymerization, the polymerization being carried out essentially to the end of the reaction or at least as early as possible. To be removed in the second polymerization vessel 50 in the process flow. Of course, the temperatures to about 100 to 200 ⁰ C, the absence of water and acidic back can be increased and kept under critical control. The conditions in the polymerization mixture, also due to critical conditions of the second polymerization, other process stages or combinations of stages can, as has been found, include an approximately 8 to process stages and treatment modes achieved 18-hour temperature cycle (thermal 55. In the context of the present invention, polymerization), which is 4 to 7 hours at about, two embodiments in particular at 100 to 135 ⁰ C and subsequent gradual temperature are considered. In one method, a raturerhöhung up to a final temperature at the end suitable means, z. Benzene, was added, forming the 8 to 18 hour period from about 150 to 200 ⁰ C with water an azeotropic mixture, so that encloses. It is important that the polymerization is carried out to the greatest possible completeness in the subsequent water and acid distillation stage, constituents as components of binary or ie up to a conversion of 90 to 100%> ternary azeotropes are removed. The agent required to form preferably at least 92% of the added or azeotropic mixture may be polymerizable material present. In which to be recovered if necessary. After the second polymerization vessel (or vessels), water and more or less conventional, but extensive acidic residues are provided directly under reduced heat exchange devices in order to be able to control the internal temperatures after preparation of the reaction mixture. removed.

7 8

The monovinyl aromatic compounds which are metal salts of saturated higher fatty acids, e.g. B. according to the invention for the preparation of the modified acids having 16 or more carbon atoms in Rubber polymers can be used, alkyl radical of the acid; to close such connections also styrene. Examples, for other higher butyl palmitate, butyl stearate, amyl palmitate, Compounds which can be used are alkyl and halogen 5 amyl stearate and hexyl stearate. .

derivatives of styrene. a-Methylstyrene can be a small one. Antioxidants can also be used in amounts of about

Replace part of the styrene in the process of the present invention from 0.1 to 2 weight percent, preferably in amounts. In general, the vinyl aromatic component makes up from 0.3 to 1 percent by weight, in the process of which. Suitable antioxidants are e.g. B, Trisnonylphenylvor present invention about 70 to 98 weight io phosphite and materials from. Phenol type ,. . as percent and preferably 85 to 95% of the polymeric 2,6-di-tert-butyl-4-methylphenol. It is easily possible to use the method according to

Diluent, from.- Although, as explained above the present invention without a catalyst, Acrylonitrile can also be used, and preferably the polymerization is carried out hereinafter nui; no catalyst added to the mixture, nor was reference made to styrene. To be given. , -...:. . ■ if; however, relatively small amounts can be

A variety of non-vulcanized natural i.e. about 0.02 to 0.5%, maximum 1.0%, based on or synthetic rubber materials can .. as based on the monomeric material used, a free one second component in the poly radicals forming the invention. Compound, e.g. an organic one merization method used. will. Suitable 20 peroxide, can be used .. Among the suitable Rubber materials are e.g. B. natural crude peroxide catalysts include benzoyl peroxide, cyclo-rubber; Crepe rubber, gutta-percha and synthe- hexanone peroxide, lauroyl peroxide ,. Tertiary butyl tables Rubbers. Among the suitable synthetic oxide, tertiary butyl peroxybenzoate, tertiary butylhydrotic Types of rubber include the copolymers peroxide, diacetyl peroxide, diethyl peroxycarbonate, from styrene and butadiene, e.g. B. from 40 to 95 weight 25 cumene hydroperoxide. and cumyl peroxide. percent butadiene and 5 to 60 percent by weight styrene, in one embodiment of the invention

nonlinear, emulsion polymerized polybutadienes, process will be about 92 to 9.7 weight percent synthetic nitrile rubber, which contains 65 to 82 percent styrene and about 3 to 8 percent by weight (excluding weight percent Butadiene and 35 to 18%. Acrylonitrile fch diluent) h'neares cis-l ^ -Pqlybutadiene, contains homopolymers of butadiene and isoprene 30 which is at least 35 up to 98%. Cjs-1,4-Konfigu- (especially from the. linear type with high or ration, along with about 5 to 15 low Cis-1,4 content) and the mixed polymers weight percent, based on the total mixture, of isobutylene with butadiene or isoprene. Ethylbenzene dissolved in a kettle. The formation of the

. If 6 to 8% ^of synthetic Jinearem poly solution is achieved with stirring. The butadiene obtained in this way with 35 to 98% of the cis-1,4-configuration is then used in the prepolymerization vessel, so excellent Izod- Impact values of transferred, and in this stage of the process, before -1.6 to 2.2 or higher is reached. The use of these preferably water up to a limit of 10 parts synthetic rubbers also eliminates the problem of acidic residues in the polymer removed per million or below from the reaction mixture. This is most easily achieved by using product, since these do not, during their manufacture, result in less contamination of the prepolymerization vessel with such residues. Emul pressure of about 7 to 14 kg / cm ^a maintained or set sion-polymerized rubber, on the other hand, as soon as the temperature reaches 80 to 90 ° C, acidic residues or constituents which have acidic properties. The mixing vessel is suitably contaminated with impurities, e.g. B. HCl, are able to form, which is equipped with a distillation device, so that they are corrosive even if they are only present in either water alone or, in general, as very small amounts. Component of a small fraction of the original

Alkyl mercaptans with six, preferably ten or a mixture can be removed. Then be more carbon atoms can be added in the process of the anhydrous solution thus obtained, the additive according to the present invention as an agent for the agent. These additives include about Adjustment of the chain length can be used. This 50 1.5 to 3 weight percent inert mineral oil, approximately Means for regulating the chain length are in 0.3 to 1 percent by weight of an antioxidant, Amounts from about 0.01 to a maximum of 0.2 weight such. B. trisnonylphenyl phosphite, and about 0.02 percent (excluding the weight of the up to 0.08% tertiary dodecyl mercaptan. The mixture in the prepolymerization vessel

important used. Although ethylbenzene per se as 55 can z. B. moved with the help of a stirring device must be designated as an inert diluent. Furthermore, in the prepolymerization shown that there is a certain chain transfer vessel means to be provided through which a thermal activity possesses, so that in the process after the exchange liquid both for supply and present invention smaller amounts of mer- can be performed to dissipate heat. That captan can be used. It is also preferably done quickly, but less than 60 heating up advantageous to use a small amount, about 5 weight-controlled conditions, with the temperatures percent, preferably about 1.5 to 3 percent by weight, should not exceed 130 ° C. in the reactor the reaction mixture should not fall below 100 ° C exclusively on the other hand, the diluent to add a material once the reaction has started. Of the that can act as a plasticizer. Small amounts of 65 batch are kept in the prepolymerization vessel, such plasticizers, such as paraffin wax or up to about 15 to 40% conversion of the mono mineral oil, increase tear strength and elongation. meren is reached. The obtained reaction product Other plasticizers that can be used are esters or are then transferred to the second polymerization vessel.

led, in which the reaction shot as a block polymerization of ethylbenzene, to the formation of the azeotropic

is carried out to the end. If necessary, mixtures can be used between. To the other

These two process stages include a filtration stage to remove the water

be switched on. Vacuum distillation during the dissolution stage, wherein

After the end of the polymerization, the water can be removed either before or after the admixture of the mixture, optionally into a storage container for the additives. It is also possible to transfer or directly to the evaporation the water before the introduction of the polymer vessel. The melted product drawn off from the vessel is removed from the evaporation sation by pressure evaporation, with the aid of appropriate aids, e.g. B. benzene, or transferred to an extruder. The extruder can be worked with a high impact azeotropic mixture even without such aids to form a product leaving the extruder. Further strength, excellent melt flow properties, all reactants, diluents should have strength and elongation properties as well as agents and additives prior to introduction to the mixing process. A loading and dissolving vessel should be as anhydrous as possible,
special advantage of the modified linear chewing 15
chuke, which are essentially anhydrous

Reaction conditions, ie experiments with a water content
manufactured from less than 10 parts per million

It can be seen that they are free from. Experiments have been carried out to show Dirt and colored particles are an essential part of the aroma of water Are lighter in color than the conventional table hydrocarbon mixtures available from distillers Products. lation removed with the least possible reflux

Which can be used in the examples below. In this experiment, in particular

mentioned measurements of the physical properties of two mixtures, namely one which consists of

Shafts of the polymers are according to standard ASTM 25 90% styrene and 10% ethylbenzene, and one

Process has been carried out, with eventual second ones consisting of 88% styrene, 10% ethylbenzene and

Deviations from these are mentioned in each case. Which consisted of 2% benzene was used. The initial one

Izod impact strength was determined according to ASTM-D-256-56 water content of the mixtures was between 70 and

certainly; Melt flow characteristics were after 140 parts per million.

ASTM-D-1238-57T determined (measurement conditions: 30 about 2300 ml of the corresponding mixture, which was 19O ⁰ C and a load of 5000 g); Heat deflection containing a small amount of tertiary butylcatechol as a polymer was determined according to ASTM-D-648-56 and Rockwell-L-scale- sationsinhibitor for styrene, were determined in a hardness according to ASTM-D-785. The samples placed 3-1 flasks, which were briefly prepared according to ASTM-D-618-58. angled elbow connected to a radiator

The percentage of volatile matter as was 35. A dip tube for sampling, given above, is a measure of the loss of residual hydrocarbons that was also advancing volatile material from the polymer, if seen. The flask was surrounded by a heating mantle of the time and temperature indicated above, which covered the entire flask and was subjected to temperature conditions. The apparatus was heating. Any remaining non-heated areas consists of a Brabender Feuchtigkeitsprüf- and 40 have been surrounded with heating tape and boiled down to 95 ⁰ C measuring instrument, in which a certain amount (keeping in; this temperature is at least 5 to 10 ° grams) of powdered sample weighed above the maximum evaporation temperature, which is then ^{heated to 140 0} C for 40 minutes, the two mixtures mentioned, so that one is about. Then the amount of volatile possible reflux substances restricted to the minimum is determined in percent. 45 will.

The elongation at break is a measure of the extreme The distillation of the styrene-ethylbenzene mixture elongation of a molded plastic material was carried out under a vacuum of 130 mm Hg and which was made using the "gagelenght-dial" one of the styrene-ethylbenzene mixture carried out under a Vateilung on an Instro measuring device by stretching a vacuum of 150 mm Hg. In both cases it is found to the point of tearing. The samples which were to be below the flask temperature during the distillation were kept ^{at 90 to 92 ° C. in accordance with ASTM-D-638.} The steam is set to temperature. It is clear from the above, was the absence of benzene 83 to 89 ° C and clear that the essential feature in the presence of benzene 80 to 83 ⁰ C.
of the method of the present invention the for sampling from the hydrocarbon virtually complete removal of water 55 mixture, which remains after distilling off the desired and acidic residues, if any are present, was opened on the dip tube, from the reactants or the attached tap and 100 ml of the mixture reaction mixture before the actual polymer is in a previously evacuated flask, which is introduced for the time sation reaction. The point of application of sampling, however, no longer evacuated azeotropic distillation, is explained in detail in this context to protect against loss of moisture, although others have also been transferred. The faucet was immediately closed again. Methods used for removing the water and the samples can be placed in a dry alder, provided that an effective Meyer flask was transferred, which was sealed with a rubber stopper to remove the water at temperatures reached. The flask for sampling can be below those at which 65 has been withdrawn and evacuated and polymerization of the reactants occurs. the above-described process can also be repeated within the scope of the present desired point in time. All samples find aids other than benzene, e.g. B. an over- were subjected to the Karl Fischer water analysis.

The following Tables I and II contain the results of the tests for the two-component and three component mixtures. The calculations in the tables! and II were according to the following: Formulas made:

° / "residual water = 7o distilled =

Parts per million water in the sample

Parts per million water in the original mixture

Volume of the distilled portion

100,

Volume of the remaining amount minus the volume of the sample

100.

From the test results it can be seen that the styrene-ethylbenzene and styrene-ethylbenzene-benzene mixtures 92% of their original water content by distilling off a maximum of 0.15% lose any mix. Further distilling off about 1.5% of the mixtures resulted in only a decrease the water content of 1 to 2%, from which it is clear that essentially all of the removable water was contained in the first 0.15% distillate fraction.

Table I.
Data for styrene-ethylbenzene mixture

Distilled 0 Rest water Parts per % 0.09 ° / o Million water 0.18 100 94 0.28 10.6 10 0.49 7.4 7th 0.78 8.5 8th 1.39 6.4 6th 2.69 5.3 5 6.4 6th 5.3 5

Table II
Data for styrene-ethylbenzene-benzene mixture

Distilled 0 Rest water Parts per % 0.09 % Million water 0.20 100 140 0.30 12.8 18th 0.41 7.1 10 1.00 7.1 10 1.65 7.1 10 3.04 5.0 7th 4.3 6th 4.3 6th

example

The following materials were used:

Weight percent

Styrene 88.00

Rubber ^) 7.98

Mineral oil 3.00

Antioxidant ( ² ) 1.00

tert-DDM ( ³ ) 0.02

Ethylbenzene ( ⁴ ) 10.00

^x ) Cis-1,4-polybutadiene - 35% cis-1,4 content.

² ) trisnonylphenyl phosphite.

³ ) tert-dodecyl mercaptan.

⁴ ) Percentage by weight of the total weight of the remaining materials.

First, styrene, rubber and ethylbenzene were in a solution vessel in the above described manner converted into a solution. The solution was then poured into the prepolymerization vessel brought and under a vacuum of 130 mm Hg to a temperature of about 86 ° C heated, with a mixture of styrene,

Ethylbenzene and essentially all of the water present in the mixture was withdrawn. The heating continued under vacuum until essentially 1.5% by weight of the starting solution (to complete To ensure removal of the water)

were pulled overhead. In and of itself, good results are obtained if only about 0.2 percent by weight removed from the starting solution. The vacuum was then released by the introduction of nitrogen canceled the reduction mixture with the

Additives are added and the temperature, but increased to about 100 ⁰ C at 13O ⁰ C to the thermal prepolymerization carried out. After about 3 hours, the resulting reaction product was removed from the prepolymerization vessel.

The above reaction mixture was then transferred to a second polymerization vessel brought, in which they under the conditions given above to temperatures slightly below 200 ° C was heated, the polymerization up

was led to a degree of conversion of 92 to 93%. The polymer obtained in this way became then the volatile components are removed. The polymer had a notched Izod impact number of 2.1 and a melt flow value at 190 ° C of 4.5. in the

otherwise the polymer was essentially white and did not contain any dirt particles.

A second experiment was carried out under the same conditions, but 2 percent by weight Benzene, based on the total weight of the

So other materials exclusively ethylbenzene, too added to the starting solution. During the vacuum distillation in the prepolymerization stage practically all of the water is drawn off overhead in the form of a water-benzene azeotrope. Low

Amounts of styrene and ethylbenzene were also removed, but the total amount of that was distilled off Starting mixture did not exceed 1.5 percent by weight. The polymer essentially had same physical properties as that of des

first attempt and also had no dirt particles.

In a third experiment, the reaction conditions were repeated again, the starting solution but directly to the prepolymerization without prior

Subjected previous treatment to remove the water below the critical limit. The physical Properties of the product thus obtained were just as good as in the first two experiments, im

but the rest of what the product is strongly interspersed with dirt particles. The presence of these dirt particles reduced the commercial value of the product to a considerable extent, so that this did not go into the first Quality class could be classified.

In series tests on a large scale, in which no removal of the prior to prepolymerization Water was found to be about 50% of the yield in terms of color poor quality and less than 3% of the yield essentially free of debris. In a further series of experiments, in each of which vacuum distillation to reduce the water content was made below 10 parts per million prior to prepolymerization, a first class material, d. H. obtain a material substantially free of dirt particles.

From the foregoing, it can be said that polystyrene resins are excellent Quality can be produced if essentially all of the water present is made up the reaction mixture removed before heating to prepolymerization temperatures above 100 ° C will. The physical properties of the final product were enhanced by the removal of the water has been improved in a manner most economically desirable the problem of corrosion of the apparatus parts, which used to be a considerable disadvantage, is also eliminated. As stated above, these corrosion problems were related to the water content and / or acidic residues in the reactants. In addition, the procedure allows According to the present invention, the use of less expensive equipment. The above The invention is of course not limited to the embodiments described in detail, but also includes the changes and modifications that are obvious to the person skilled in the art a.

Claims (3)

Patent claims: 1. A process for the preparation of graft copolymers by polymerization of a 2 to 30% ^e n solution of a natural or synthetic rubber in a vinyl aromatic monomer, or a mixture thereof with acrylonitrile, optionally in the presence of 3 to 30 weight percent, based on the total weight of the mixture, an inert diluent, characterized in that a reaction mixture is used from which water and acidic constituents have been removed by distillation before the start of the polymerization. 2. The method according to claim 1, characterized in that there is a reaction mixture for Polymerization brings about the water content of which has been lowered to less than 10 parts per million is. 3. The method according to claim 1 and 2, characterized in that the inert diluent is used Ethylbenzene is used. 709 720/514 1.68 © Bundesdruckerei Berlin