DE2017277A1 - Polystyrene prepn - Google Patents

Abstract

Prepn. consists of (A) combining styrene mononer, a rubber cpd. and polystyrene, (B) the wt. percentage of polystyrene in the initial mixture is maintained at a value exceeding the polystyrene phase inversion rate so that the polystyrene forms a continuous phase in soln. in the styrene monomer, coexisting with a suspension of rubber globules (C) the mixture is brought to a temp. a which polymerisn. does not occur and is stirred to give a uniform suspension. (D) the mixture is then polymerised. The rubbery composn. is polybutadiene. The mixture consists initially of 1-5 wt.% rubber polymer 12-20% polystyrene, and 87-75 wt.% styrene monomer. Polymer is extremely resistant to mech. shock and does not fracture.

Description

Method and apparatus for making polystyrene The invention relates to a wet polymerisation process for the production of high-quality, high impact polystyrene and in particular a continuous process for its manufacture of impact-resistant polystyrene.

Polystyrene, which has been available for many years, owns some undesirable properties - such as an extraordinary brittleness, which makes it unsuitable for many modern uses. For modification Various processes have already been proposed for polystyrene in order to give it a definite character to impart physical properties. One of these methods is to polymerizing monomeric styrene in the presence of a rubbery compound. The polystyrene obtained, modified by rubber (impact-resistant polystyrene) has improved impact resistance, improved toughness, and is not brittle. Of the The need for impact-resistant polystyrene is extraordinarily great; it is estimated that one annual production capacity of about 500 million tons (one trillion pounds) is required, which is increasing every year.

There are various processes for the production of impact-resistant polystyrene. known. These methods can generally be divided into two classes. The first Class, represented by U.S. Patents 3,243,481 and 2,694,692, -covers continuous Process in which the starting compounds in a first polymerization vessel are combined and heated until the polymerization begins and a predetermined one Degree achieved. Then the polymerizing mixture becomes a second and more Transferring polymerization vessels, - e are operated at higher and higher temperatures, wonac finally formed the desired impact-resistant polystyrene A stirring treatment, in particular in the process in US Pat. No. 2,694,692 in the first Polymerization vessel is carried out, the rubber'.ar-term compound is used break up into particles of various sizes, which are finely dispersed in the monomeric styrene will.

These methods have several disadvantages. First of all, it is useful the distribution of the molecular weight, which is characteristic of the end product, to be kept within as narrow limits as possible, because of the distribution of the molecular weight the properties of the product are determined to a large extent. A key factor the one that affects the molecular weight of the final product is the temperature at which it is placed is subjected during its manufacture. Since conventional methods with more as a polymerization vessel or a multi-temperature polymerization vessel that - successive zones of increasing Temperature, work, that will be impact-resistant. Polystyrene subjected to more than one polymerization temperature, and the process cannot be isothermal. This degrades the end product, since its molecular weight cannot be kept within narrow limits. Part of the high impact polystyrene produced by these traditional methods can therefore-have a very convenient and desirable molecular weight, while the kest does not have this molecular weight.

Second, the control of the first polymerization vessel becomes very great important and difficult. The already existing procedures are characterized by the Attempt to achieve the required phase inversion while simultaneously applying the reactive monomers are polymerized. The particle size of the precipitated Rubber globules are used to determine the mechanical properties of the end product very important, and the two simultaneous operations complicate the control this variable. The type and extent of stirring used normally to do so to be able to control the particle size distribution; However, with the conventional Operations managers also consider heat transfer requirements, d, ie with the system.

are linked, as the polymerization that takes place generates heat, which must be removed for temperature control. Another type of manufacturing process of high impact polystyrene represented by US Patents 3,144,420 and 3,370 105 uses batch polymerization from an aqueous suspension. This aqueous suspension is usually made by mixing monomeric styrene, Polystyrene and a rubbery compound from the first polymerization vessel with Water is made to increase the viscosity of the resulting mass for ease of handling to keep it sufficiently low during the further bolymerization.

A major disadvantage of these methods is that the water takes up a considerable amount of water Part of the capacity of the tank in which the polymerisation takes place is claimed. In addition, unwanted initiators, suspension medium and in the process Catalysts needed. The water must also be separated from the end product, thereby increasing the operator costs. As the polymerization vessels emptied The process may have to do this before it can be filled with new materials are not continuously carried out, they are carried out in batches Impact polystyrene manufacturing plant takes considerable labor and time is wasted. As the procedural costs make up a significant proportion of make up the final cost of high impact polystyrene, these methods are inconvenient.

In order to achieve high impact polystyrene with desirable after the process mentioned To produce properties is the addition of significant amounts of a rubbery one Modification compound required. Because rubber is also a major factor For the cost of the high impact polystyrene, it is convenient to use the same Best properties for impact-resistant polystyrene using a smaller amount to achieve the rubbery compound.

5 has now been found that the important properties of the end product are primarily determined during premixing, in which the phase reversal occurs. This process iz> t analogous to a suspension reversal, with a first component becoming the continuous phase, while a second Component that was previously continuous, in the form of discrete globules, i.e. in discontinuous i '¢ rm is dispersed. ir special can be the phase reversal point as the inversion of a continuous phase of the rubbery compound solution in monomeric styrene, in which discrete beads of polystyrene are suspended and dispersed are, in a continuous phase from a solution of polystyrene in monomeric Styrene, in which discrete beads of the rubbery compound are suspended and are dispersed.

It was also found that the polymerization for the production of impact-resistant polystyrene this phase inversion of the rubber-like modification compound into discrete spheres that are dispersed in a matrix of polystyrene and monomeric styrene are required, preferably at the time when the final polymerization has not yet taken place has taken place. In the. The phase reversal point became known in the art normally only achieved in the first polymerization vessel. This is also one of the Reasons for using the combination-type methods where after a initial polymerization in a first polymerization vessel, a water fusion process is applied, the phase inversion necessarily before the suspension step must be carried out in the polymerization vessel.

The phase inversion process is reversible, and the relationships are discontinuous become a continuous phase by the relative amounts of the components forming the mixture Components determined. For example, rubber beads are made in the: matrix Polystyrene and styrene dispersed when the content of polystyrene at least Is 12.2% by weight. (In the following, all percentages are based on the weight related) If the content of polystyrene falls below 12.2%, it will precipitate in a matrix a solution of the rubbery compound ir, monomeric styrene dispersed. Of the The process of phase inversion goes both ways and is mainly through controlled the percentage of polystyrene in the composition.

A main aim of the present invention is, however, to provide a new process for the production of impact-resistant polystyrene.

Further objectives of the invention are to make such a process cheaper the production of impact-resistant polystyrene with improved properties as well as the isothermal Wr continuous implementation of the process.

Another aim of the invention is for an output system a matrix relationship between monomeric styrene, polystyrene and a Kamchuk-like compound to ensure in such a way that the rubber-like connection in discrete spheres dispersed and suspended in a matrix of polystyrene and monodermic styrene as well as to achieve this matrix relationship at a temperature at which none Polymerization occurs, and this matrix relationship between the starting components to register and control.

Further objects of the present invention will become apparent from the following Description and in connection with the drawings.

The invention relates to a process for the production of impact-resistant. Polystyrene, which is characterized in that (a) monomeres as starting substances Styrene, polystyrene and a rubbery compound put together, (b) the content of polystyrene in the starting mixture at a value that the polystyrene content at the phase inversion, above which the starting mixture takes the form of a continuous Matrix phase of a solution of polystyrene in monomeric styrene, in which discrete beads the rubbery compound are suspended and dispersed, assumes, exceeds, (c) maintaining the starting mixture at a temperature at which no polymerization occurs occurs, and meanwhile it is about the mean size of the rubber-like spheres to advance so that they are relatively uniform, ur.d (d) the starting mixture then polymerized.

According to the present invention is in a highly effective process an impact-resistant polystyrene of high quality testifies by. in detail the following Process steps are lined up in a row: In a first tank, which is in a is kept below the polymerisation temperature, freely selectable temperature, impact-resistant poly-styrene, monomeric styrene and a rubber-like compound mixed, the polystyrene content being at least 12.2 wt. Alpha is maintained; then the product of the first pank transferred to a polymerization vessel, which is preferably within a narrow temperature range is held; it is then polymerized until the viscosity of the material has reached a predetermined value; and eventually becomes a part. of the product from the polymerization vessel into an evaporation vessel and the rest back into the first Tank led, around the polystyrene content4 of at least 12.2 Weight- to hold.

The first tank can be used to mix the monomeric styrene, the polystyrene and mechanical stirring or other mixing method of the rubbery compound be used for a relatively uniformly small particle size for the rubber beads to arrive during the subsequent polymerization able to coagulate to form rubber balls.

NEN, which in the end product are preferably no larger than 10 r -in diameter are.

In the process according to the invention, an isothermal polymerization is used enabled by the rubbery compound and the polystyrene through the phase breakpoint be brought before the polymerization step takes place and without high temperatures would have to be applied. It has been found that when blending a predetermined Amount of polystyrene in solution with monomeric styrene and rubber is the phase reversal point is achieved and sustained; The amount of pre-determined polystyrene required is normally between 10 to 15%, but is determined by the type and amount of elastomer as well as temperature and the amount of polystyrene grafted onto the elastomer.

According to the essentials of the present invention, the molecular weight distribution and the related properties of the high impact polystyrene produced controlled within narrow limits, so that a larger proportion of the produced impact-resistant Polystyrene has the desired properties. Another feature of the present Invention is that the method for the production of impact-resistant Polystyrene large-scale application is capable, as it is continuously operated by what returning part of the output of the polymerization vessel to the first Tank to maintain the desired phase inversion concentrations in the first tank mixed ingredients is made possible. The process can be continuous can be carried out without the first tank having to be emptied before using new material is filled. The content of the first tank is homogeneous, what by the previously known method was not achievable. Another feature of the invention is that the entire volume capacity of the plant for the production of Schl Tough polystyrene is used, which is compared to the conventional method that made use of aqueous suspensions is an improvement since the water takes up a considerable proportion of the available space.

Since the recycled material has a pesticide content of. polymerized well beyond 12.2 polymer, the mixture is in the first tank held slightly at the phase reversal point. Thus, by mixing of predetermined amounts of recycled polystyrene, rubber-like compound and monomeric styrene in the first tank, the phase reversal point due to the recirculation process up-to-date, which makes it unnecessary, already in the first procedural stage carry out a polymerization as required in the conventional method was just to reach the phase reversal point.

Another feature of the present invention is that the recycled material contains high-impact polystyrene, and it is believed that this die-kautachuk-like Compound incorporated Graft copolymer, which is fed to the first or premix tank, with for Achievement of improved properties of the end product compared with those after; conventional processes produced impact-resistant polystyrenes, contributing. Judged according to the customary I-ZOD test, that produced according to the invention is impact-resistant Polystyrene compared to the impact-resistant polystyrene produced by other processes a comparable toughness and comparable impact properties, while At the same time, there are lower proportions of rubber-like modifiers serving as modifiers Compounds Containing This feature is in view of the above mentioned cost significant for rubber.

Since the method according to the present invention is continuous, i.e. without filling and emptying the tanks in batches it was used for the important large-scale production of impact-resistant polystyrene will.

Another feature of the invention relates to maintenance the phase unique concentration in the first tank. A method of maintenance the correct content of polystyrene, rubber-like compound and monomer Styrene in the first tank consists of the polystyrene content in the The amount of material fed to the polymerization vessel is monitored Tank- recycled material may vary depending on the changes in the detected Content can be changed so as to reverse the phase for the material in the first tank guarantee. Another method is to have one from time to time Sample from the first tank examined under the microscope and then the amount of attributable Material adjusts to the desired phase reversal to achieve.

The material in the polymerization vessel does not become too incomplete polymerized, otherwise its viscosity would be too high for recycling. aside from that Too high a viscosity would cause convection (movement) in the polymerization vessel disturb, which is required for heat transfer in the polymerization vessel. aside from that the reaction rate in this type of chemical conversion in the degraded as it nears its completion. To the cost of the unit of weight of impact-resistant polystyrene, which is produced according to the present process, To keep it as low as possible, it is expedient to reduce the speed with which it is produced is to bring to a maximum value. According to the present invention, this Objective achieved because not all of the material in the polymerization vessel fully polymerizes Is ensured so that compliance with the maximum reaction speed while the viscosity of the polymerizing mass in the polymerization vessel is kept so low that the dissipation of the heat of polymerization facilitates will. Monomeric styrene that is still in the one that leaves the polymerization vessel Material may be contained by one of several known methods, for example with the aid of a twin-screw evaporation extruder.

The invention is explained in more detail below with reference to drawings, in which Figure 1 shows an apparatus arrangement for performing the method according to of the present invention; Figure 2 is a reproduction of a photomicrograph of early stage polystyrene dispersed in a matrix of rubber and styrene the phase reversal process; ; igur 3 the reproduction of a photomicrograph showing the shows the phase reversal zone in which both continuous phases are present, and FIG. 4 is a reproduction of a microphotograph of in a matrix of polystyrene and styrene dispersed rubber at the completion of the phase inversion process.

According to FIG. 1, the dissolving vessel 10 is charged with styrene and polybutadiene. Preferably, 90 to 99% of the material introduced into the dissolving vessel 10 consists; made of styrene and up to 10% of polybutadiene. The concentration of polybutadiene will be determined by the properties desired in the end product.

Most commercial products have a content of between 3 and 8. The compound polybutadiene is merely exemplary of one type of Elastomer compounds that are soluble in styrene and have a chemical bond can enter with styrene. The Blatoner chosen as the modifier is determined by the properties desired in the end product. The polybutadiene will 'bis dissolved to a desired concentration in styrene and can in the dissolving vessel 10, for example be present at a concentration of 5.9%.

U to promote the dissolving process, a propeller stirrer 11 with high Speed can be used. The discharge of the dissolving vessel 10 is by means of a Pump 13 is fed to a premixing or precipitation vessel 12. In the precipitation vessel 12 takes place the phase reversal described above, and by means of a pump 17 is from the precipitation vessel 12 material is continuously fed to the polymerization vessel 14.

As already mentioned, the phase reversal point must be reached in order to To be able to produce impact-resistant polystyrene, in the exemplary embodiment of the process according to the present invention becomes part of the output of the polymerization vessel 14 fed back into the discharge vessel 12 by means of pump 15 and control valve 16. Of the The phase reversal point is ensured by ensuring that at least 12.2% of the contents of the precipitation vessel 12 consist of polystyrene. According to the invention the mixture in the precipitation vessel 12 is preferably intimate by means of a stirrer 12 ' touched, ur. to achieve that the polybutadiene particles are in the disperse phase are present, and in the continuous matrix of monomeric styrene, which is preferably contains at least 12.2% dissolved polystyrene, are of the same size. The size of the violet is preferably 5 to 10. In the method according to the invention, the low rubber content the coagulation speed of the rubber beads, and the uniform ball size is relatively easy thanks to the stirrer 12 ' ensured, the effects of the elastomer beads on the physical Properties of the end product can be optimized.

The phase reversal point is reached in the method according to the invention, without the use of high polymerization temperatures, as is the case with conventional ones Procedure, would be required. The output of the precipitation vessel 12, the Polymerization vessel 14 is supplied, is there within a narrowly delimited Temperature range polymerized, so that the Polymerisation process can be described as isothermal.

This leads to significant advantages, as already mentioned.

The temperature at which the polymerization takes place can be desired properties of the impact-resistant polystyrene to be produced are selected, must be at least 930 C in any case.

The phase reversal point in the present system is defined by -the inversion of a continuous matrix phase from a solution of the rubbery Compound in monomeric styrene that suspends discrete spheres of polystyrene and dispersed in a continuous matrix of a solution of polystyrene in mon-ome-rem styrene, the discrete spheres of the rubbery compound are suspended and contained discergized.

Figure 2 shows the initial continuous matrix phase of the solution the rubbery compound in monoinereu.- styrene, which consists of discrete beads Contains dispersed polystyrene.

The numerous dark spots 25 in Figure 2 represent polystyrene, while the light, contiguous area means 30 d @@ rubber / styrene matrix. As can be clearly seen, the polystyrene 25 is discontinuous and over the continuous matrix 30 of rubber and styrene dispersed. With a polystyrene content of less than 5% in the polystyrene / styrene / polybutadiene system, a phase inversion occurs not a.

With increasing polystyrene concentration in this system begins the phase reversal and lasts until completion.

Figure 3, a photomicrograph of the polystyrene / styrene polybutadiene system shows the relationships during phase inversion.

The light areas 30 mean polybutadiene material, while the dark areas 25 represent the polystyrene. You can use both substances at the same time recognize in continuous and discontinuous phase. These two phases coexist during the phase transition period and occur at one PoTystyrene concentration from 5 to 15 o / o depending on the type of elastomer used, temperature and other factors. Completed with increasing polystyrene content the phase inversion.

Figure 4, a photomicrograph of the system polystyrene / styrene polybutadiene, illustrates the dispersions of rubber in the polystyrene / styrene matrix .. The lighter areas 30A represent the rubber particles that are in the darker ones Areas, 25A, of the polystyrene / styrene matrix. In this photomicrograph the process of phase reversal is already completed, i.e. the previously continuous one Matrix phase of the solution of the rubbery compound 30 in styrene is the discrete Containing beads of polystyrene 25 suspended and dis-e'-yed, as in Figure Figure 2 represents is in a continuous matrix phase from a solution of polystyrene been converted into styrene 25A, the discrete beads 30A of the rubbery Contains compound suspended and dispersed, as shown in FIG.

The 800x magnification used to make the photomicrographs proved suitable for examining and measuring the individual particles in this System. In addition, an observation through an oil immersion lens (oil immersion objective lens), which resulted in a 2000-fold overall magnification and Investigation of the internal structure of the precipitated particles was suitable.

Continuously measuring devices such as the flow meter 18, represent the content of polystyrene in the discharge of the precipitation vessel 12 solid, which is fed to the polymerization vessel 14. The output measurement signal of the Meter 1.8 is with the control valve. 16 linked that the amount of from the polymerization vessel 14 controls the polystyrene returned to the precipitation vessel 12 in order to ensure that the polystyrene content is sufficient to keep the phase reversal correct.

Some of the recycled material consists of polybutadiene, which has been graft or copolymerized in the polymerization vessel 14. One takes suggests that this recycling and repolymerization of the polybutadiene is a significant one Influence on the achievement of the 'improved properties of the according to the invention Process made of impact-resistant polystyrene has been found to do this impact-resistant polystyrene has at least as good properties as the products conventional methods, but using lesser amounts of rubbery ones Connections is established. This is in terms of the economics of the Process for the production of impact-resistant polystyrene is important.

The proportion a'n the output of the polymerization vessel 14- that is not is returned to the precipitation vessel 12, an evaporation vessel is used for production fed by high impact polystyrene. In detail, the output of the polymerization vessel 14 supplied to the evaporation vessel 19 by means of a pump 15.

The vapor from non-polymerized styrene is removed from it and fed to a condensation device, dmit it is reused in the present process can be. The polymerized material that remains in the evaporation vessel 19, will directly fed to the extruder 21. if desired, a pump 20 can be interposed the evaporation vessel 19 and the extruder 21 must be connected. The extruder 21 delivers the impact-resistant polystyrene in the form of extruded, solid strands, which are immediately attached suitable for chopping or tableting.

The apparatus arrangement shown in FIG. 1 merely illustrates the principles of the present invention, according to which an isothermal polymerization made of impact-resistant polystyrene. The principles of this invention can can also be concretized by other devices.

The following example explains the invention without restricting it.

Example A continuous process for the production of 2.3 kg of the desired high impact polystyrene was passed through.

200 g of material were fed to the precipitation vessel 12 per hour.

Of this feed, 152 g per hour were accounted for by a fresh feed from the dissolving vessel 10, consisting of 2% polybutadiene and 98% monomeric styrene, and 50 g per hour on recycle mixture from the polymerization vessel 14, consisting from 2% folybutadiene, 60% polystyrene and 38% monomeric styrene. These speeds are average values, they varied as follows: The feed rate of dissolving vessel 10-varied between 128 and 175 g per hour, while the feed rate from the return line varied between 40 and 60 g per hour. The output of the precipitation vessel 11 averaged 200 g ever Hour and varied between 168 and 235 g per hour.

Its composition averaged 2% polybutadiene, 15 % Polystyrene and 83% monomeric styrene and varied within the following limits: 2% polybutadiene, 12, to 20 polystyrene and 86 to 78% monomeric styrene. In the precipitation vessel 12 was mechanically agitated at an average speed of 300 rpm and one Range of variation between 250 and 350 rpm.

The reaction was carried out at ambient temperature, around the residence time in the precipitation vessel was 1.75 to 2.5 hours.

The input into the polymerization vessel 14 was equal to the output of the precipitation vessel 12. The output of the polymerization vessel 14 was average 202 g per hour and varied between 168 and 2.35 g per hour; its composition averaged 2 polybutadiene, 60% polystyrene and 38% monomeric styrene, the following fluctuations occurred: 2% polybutadiene, 45 to 65% polystyrene and 53 to 33% styrene monomer. The reaction temperature in the polymerization vessel 14 was kept between 126 and 1330 C; the residence time was average 5 hours and varied from G to 5.3 hours. In the polymerization vessel 14 was stirred at a speed of 60 to 120 rpm.

The output of the polymerization vessel 14 was into an exhaust vessel which contained a vacuum oven. Its temperature was 1400 C / 13 mm Hg and the residence time of the material in it was 1.5 hours. The rest Monomer was also removed from the final product by making the final product cut into small pieces and put in a VaiLuu ¢ oven at 700 C / 13 mm Hg for 24 hours long dried again.

2.3 kg of the product were produced. The shredded product was thoroughly mixed; and for the achievement of prior test results randomly sampled.

The test results are summarized in Tables 1 and 2 below relate to physical properties and represent the average result of four separate determinations. Literature values for a comparable product from 'Dow Chemical Company are also listed for comparison.

Table 1 Test Average Variation Dow Styrene Result width for No. 338 5 samples rubber content 2.9% - approx. 3.0 basic molar viscosity, dl / g 1.00 0.980-1.017 melt flow index g / 10 min. 2.54 2.31-2.63 tensile strength Yield (kg / cm²) 425.5 422 - 440 457 Break (kg / cm²) 402.6 390.5 - 415.7 457 IZOD impact strength mkg / cm 0.0915 0.0822-0.109 0.0708 Young's modulus (kg / cm² X 105) 0.314 0.275 - 0.344 0.305 elongation yielding,% 2.58 2.38 - 2.88 3.0 break. % 11.5 8.8-13.0 6.0 The Dow Styron # 338, chosen for comparison purposes, is just one one large number of the general grade of moderately impact resistant polystyrenes, the are in trade.

The purpose of the comparison is only to show that the invention Process for the production of impact-resistant polystyrene using the simple Laboratory apparatus of the present example and without an attempt being made, really to maintain optimal conditions for the delivery of material that has the same properties as commercially available material. Really important is the higher value for the impact strength despite the lower melt flow index and the higher molecular weight, both usually associated with brittleness and low impact strength of the material go hand in hand.

The unexpectedly high impact strength is the new recycling process attributed according to the present invention.

Melt flow index and molecular weight of the product are usually by internal lubricants, reaction modifiers and reaction temperature controlled. In the above example, an arbitrarily chosen reaction temperature was used applied and dispensed with lubricants or modifiers. The middle one Molecular weight therefore differed from the Dow Chemical comparative material Co: npany, and also the properties that are linked to the molecular weight, should be different.

The molecular weight was determined by gel diffusion chromatography (Gel Permeation Chromatography) determined; the results are in the table below 2 summarized: T a b e l 1 e- 2 product of the comparable according to the invention Product of the "Dow Chemical Co." process Weight average molecular weight (MW) 269,000 170,000 Molecular Weight Average Molecular Weight (MN) 105,000 60.000; AriN (polydispersity index) 2958 2.8 The investigations using gel diffusion chromatography of the eride product also gave a narrow molecular weight distribution range for the 2.3 kg of according to the above example produced impact-resistant polystyrene This narrow range of distribution is of economic Often desirable from the point of view as the main part of the invention Process produced product the predicted and desired, valuable Possesses properties. In contrast, gel diffusion chromatography showed for conventional products a wider distribution range for the molecular weight, i.e., a greater percentage of the conventional material does not have what is desired Properties and is therefore not a top product.

Some molecular weight distribution is essential for the final product Desired because certain properties of the impact-resistant polystyrene are random Depend on the orientation of the molecules. But if 'the distribution is too wide; how the case with conventional procedures because of their non-is-othermen nature undesirable properties. If the molecular weight is too low, this is impact polystyrene too soft and weak "while in the reverse pall, i.

if the molecular weight is too high, the high impact polystyrene too is brittle and difficult to shape.

As can be seen from Table 1, the IZOD impact strength test shows that the impact-resistant Po styrene produced according to the invention has significantly better properties possesses than the Dow Styron 338. These better properties are approximated with achieved the same rubber content, although the rubber gel in the invention manufactured '; product is slightly lower than that in the comparable material found by Dow.

Claims (12)

P a t e n t a n s p r ü c h e 1. A process for the production of impact-resistant polystyrene, characterized by that one (a) as starting substances monomeric styrene, polystyrene and a rubber-like Compound combines ;, (b) the content of polystyrene in the starting mixture a value that holds the polystyrene content at the shase reversal, above that the initial mixture takes the form of a continuous matrix phase of a solution of Polystyrene in monomeric styrene, in which discrete globules of the rubbery compound are suspended and dispersed, assumes, exceeds, (c) the starting mixture at a temperature at which no polymerization occurs, and while it does so. stirs to reduce the mean size of the rubbery balls, so that they are relatively uniform, and (d) the starting mixture subsequently polymerized. 2. The method according to claim 1, characterized in that one Part of the polymer to maintain the polystyrene content in the starting mixture to at least the value previously determined for the phase reversal. 3. The method according to claim 2, characterized in that one (a) the polystyrene content in the initial mixture is determined and (.b) according to the deviations in-the determined values for the polystyrene content to compensate for these deviations de amount of recycled polystyrene regulated. 4. The method according to any one of the preceding claims, characterized in that that the initial mixture is polymerized isothermally. 5. The method according to claim 4, characterized in that the Polymerization at a temperature of at least 930 C carried out. 6. The method according to any one of the preceding claims, characterized in, that polybutadiene is used as the rubbery compound. 7. The method according to any one of the preceding claims, characterized in, that the starting mixture is partially polymerized. 8. method according to one of the preceding claims, characterized in that that the polystyrene content for the reversal is a value of at least 12.2% by weight Polystyrene chooses. 9. The method according to any one of the preceding claims, characterized in, that the mean size of the rubber spheres should not exceed a value of 10 p brings. 10. The method according to any one of the preceding claims, characterized characterized in that the product of the polymerization stage is subjected to evaporation. 11. The method according to any one of the preceding claims, characterized in that that one for the starting mixture 1 to 5 wt .-% rubbery compound, 12 to 20% polystyrene and 87 to 75% monomeric styrene are used. 12. Device for the production of impact-resistant polystyrene, consisting of: (a) Means for dissolving a rubbery compound in styrene and at the same time Stirring the mixture, (b) a precipitation vessel to form a starting mixture of monomeric styrene, the rubbery compound and polystyrene, (c) agents for transferring the starting mixture into the precipitation vessel while holding it at the same time of the starting mixture at a temperature at which no polymerization occurs, (d) a polymerization vessel for receiving the product from the precipitation vessel and for the production of polystyrene, (e) controllable means for the promotion of a part of the generated polystyrene from the Polymerisati onsgefäß -in the precipitation vessel for Maintaining the polystyrene content in the precipitation vessel at a value above the phase inversion content, above which the starting mixture has the form "'of a continuous Matrix phase from a solution of polystyrene in monomeric styrene, the discrete spheres the rubbery compound contains suspended and dispersed, assumes, and (f) means for agitation in the precipitation vessel to reduce the mean diameter of the globules of the rubbery compound to relatively uniform values. L e r s e i t e