CA1090500A - Process for the manufacture of impact resistant styrene compounds - Google Patents

Abstract

Abstract of the disclosure:
There is disclosed a process for preparing impact resistant styrene graft copolymers having improved properties, especially an excellent combination of toughness, hardness and gloss. They are obtained by polymerizing a solution of an ethylene-propylene-tercomponent rubber in a mixture of styrene and acrylonitrile in one step (mass polymerization) or two steps (mass/suspension poly-merization) in the presence of an organic peroxide and subjec-ting the copolymer obtained to a shear extrusion yielding rubber particles with an average size below 1 µm and thereafter cross-linking said rubber particles, care being taken that an amount of 0.02 to 0.5 weight % of a cross-linking initiator is present when cross-linking starts.

Description

109~500 - The present invention provides a process for preparing thermoplastic copolymers, having a high toughness, a high hard-ness and good melt flowing properties as well as a high surface gloss.
Graft copolymers of styrene and acrylonitrile on a buta-diene homo- or copolymer are known as ABS polymers. AXS polymers prepared by graft copolymerization of styrene and acrylonitrile on an ethylene/propylene/tertiary component rubber and havinq an essentially improved weather resistance are known as well.
Such graft copolymers may be prepared by mass or by mass/
suspension polymerization. This process where a solution of the rubber in monomeric styrene or a styrene/acrylonitrile mixture is partly polymerized in mass and is further polymerized in mass or in suspension until the polymerization is complete normally yields impact resistant polystyrene or impact resistant styrene/
acrylonitrile copolymers having a good toughness, go~d flow pro-perties ana a sufficient hardness. Injection molded parts pre-pared from these product, however, have only a very dim surface ~loss.
For this reason ABS polymers intended to have a high sur-face gloss, most frequently are prepared according to the emul-sion polymerization process. In this process both the rubber and the graft copolymer of styrene/acrylonitrile on the rubber are prepared in aqueous emulsion. The ABS polymers thus obtained are characterized by an especially high surface gloss of the injection molded parts prepared therefrom as compared witn those prepared by a mass suspension process. On the other hand it is ~nown that the emulsion process is more expensive technically 29 and, consequently, less profita~le than the mass and/or suspen-lO90SOO HOE 75/F 344 sion process, among others owing to the fact that the working up of the wast~ water obtalned is necessary to achieve environ-- mental protection.
Three processes have become known hitherto for partially overcoming the difficulties due to the mass/suspension process.
The surface gloss may be improved 1) by using extremely high shaering forces in the prepolymeri-zation (cf. British Patent 1,383,017)

2) by adding nonpolar hydrocarbons as solvents Icf. U.S. Pub-lished Application B 469,468; U.S. Patent 3,538,190)~

3) by adding separately prepared graft copolymers of styrene/
acrylonitrile on ethylene/propylene/tertiary component rub-ber or on polybutadiene acting as oil in oil emulsifiers (cf. U.S. Patent Specification 3,538,192).
It is further known that polymer melts are subjected to a more or less great shearing in suitable machines such as ex-truders, which may even partially cause a breaking of the poly-mer molecules. Advantage is taken of this fact especially in the degradation process of polyethylene melts of high molecular weight. It is also known that polymers may be cross-linked in the melt by the addition of initiators.
A process has now been found for preparing impact resistant copolymers exhibiting a high gloss by radical mass polymerization or mass/suspension polymerization of a) 98 to 70 weight %, preferably 92 to 75 weight %, o~ a mix-ture of aa) 90 to 60 weight %, preferably 90 to 70 weight %, especially of 80 to 70 weight %, of styrene and/or of at least one 29 styrene derivative, with - . _ 3 _ 1~9~SOO HOE 75/F 344 ab) 10 to 40 weight %, preferably 10 to 30 weight ~, especially of 20 to 30 weight ~, of acrylonitrile and/or of at least one different copolymerizable derivative of acrylLc acid, in admixture with b) 2 to 30 weight %, preferably 8 to 25 weight %, of an ethy-lene-propylene-tertiary component rubber (EPTR), the quantities (aa) and (ab) being calculated on the total quan-tity of (aa) + (ab) of the monomers and the quantities (a) and (b) being calculated on the total quantity of (a) + (b) of mo-nomers and EPTR, and cross-linki~ of the rubber particles, which comprises submitting the copolymer, which contains from 0.02 to 0.5 weight ~, preferably from 0.08 to 0.3 weight % of a cross-linking initiator, to a shearing extrusion prior to cross-linking, until the rubber particles have an average size of be-low 1 ~m.
Instead of styrene as monomeric component (aa) there may be used as well styrene derivatives such as ~-methyl-styrene or styrenes met~ylated in the nucleus (for example o- or p- vi-nyl toluene or vinyl xylenes~ or styrenes halogenated in the nuc-leus (for example o- or p-chloro- or brom~styrene.) or vinyl cyclo-hexane or methylated or halogenated derivatives of v.inyl cyclo-hexane or mixtures of styrene and one or more derivatives of styrene, or mixtures of two or more derivatives of styrene, pre-ferably mixtures of 95 to 60 weight % styrene and 5 to 40 weight ~ of ~ -methyl styrene.
Instead of acrylonitrile as monomeric component ~ab) there may also be used different copolymerizable acrylic acid deriva-tives such as methacrylonitrile or esters of acrylic acid, of 29 methacrylic acid, of itaconic acid (= carboxymethylacrylic acid), HOE 75/F 3~4 1~)9'~500 of maleic ~cid (= carboxyacrylic acid) or of fumaric acid with lower ali-phatic alcohols (for example methanol, ethanol, isoprq~ol, butanol, iso-butanol, he~ol, octanol, isooc ~ ol or 2-ethyl hexanol) alone or in combi-nation with one another or with acrylonitrile.
Mixtures of 20 to 30 weight % of acrylonitrile and 80 to 70 weight % of styrene are especially advantegous to obtain the desired resistance to solvents, tensile stre~h, crazing and heat resistance, and are therefore used preferably.
Suitable ethylene/propylene/tertiary component rubbers are those obtained by polymerization of 69.5 to 30 weight ~ of ethylene, 30 to 69.5 weight ~ of propylene and 0.5 to 15, prefe-rably 3 to 12~weight % of a non-conjugated diene having at least 5 carbon atoms, such as 5-ethylidene-norbornene 2, di-cyclo-pentadiene, 2,2,1-bicycloheptadiene and 1,4-hexadiene as ter-tiary components.
It is recommended to dissolve the rubber first in the non-polar monomer(s) (aa), the addition of usual nonpolar substances e.g. white oils (mixtures of aliphatic hydrocarbons having a boiling point in the range of from 100 to 300C) being also possible. After heating and addition of the polar monomer(s) (ab), a solution of the EPT rubber in the monomer mixture is present when the polymerization temperature is attained.
The radical polymerization of the monomers is carried out in known manner either thermally or with the use of one or several polymerization initiators soluble in the monomers, e.g. peroxy compounds such as t-butylperbenzoate, t-butyl peracetate, di-benzoyl peroxide, t-butyl peroctoate, dilauroyl peroxide or nitrogen compounds yielding radicals when decomposing such as 29 azodiisobutyronitrile. These polymerization initiators are lO9V500 used in the usual concentration range of about 0.05 to 1 weight ~, preferably 0.1 to 0.4 weight %, calculated on the total quan- -tity of monomers and EPT rubber.
Possible alternatives of the process are the known mass and mass/suspension processes. ~oth processes are carried out as mass polymerizations while stirring until a phase inversion can be observed. In the case of the mass/suspension, process polymerization is continued and terminated as a suspension polymerization after suspension in water of the reaction mixture from the mass polymerization, while in the case of a mass process the polmyerization is continued and terminated as a mass polymeri-zation.
The mass/suspension polymerization is usually carried out discontinllously and the mass polymerization is carried out contin-uously, which distinction does not influence the properties of the products formed.
The suspënsion polymerization is carried out in the pre-sence of 0.05 to 0.4 weight % of known suspension stabilizers such as water-soluble cellulose ether, gelatine, polyvinyl al-cohol, partially saponified polyvinyl acetate or tricalcium phosphate and, optionally, in the presence of complex-forming substances such as ethylene diamine sodium tetraacetate.
The desired polymerization degree tmolar weight) is ~b-tained by means of the regulators known to be used in the sty-rene polymerization such as dimeric ~-methyl-styrenesin a con-' centration range of about 0.1 to 1 weight % or wïth mercaptans such as n- or t-dodecyl mercaptan being added in an amount of about 0.01 to 0.5 weight %.
~he polymerization initiators as well as the molar weight 29 regulators may be added at the same time or subsequently in . ..

~09V5~ HOE 75/F 344 measured portions as the polymerization proceeds in the pre-polyrnerization (first step=/mass polymerization) and/or in the following second polymerization step (suspension polymeri-zation).
The cross-linking initiator to be used according to the in-vention is added most advantageously either prior to or at any time in the course of the polymerization. The essential function of said cross-linking initiator is to initiate the cross-link-ing of the sheared rubber particles. The initiator may decom-pose to a minor extent already in the course of the polymeri-zation and influence the latter. The initiator is added in an amount of about 0.06 to 0.6 weight % (calculated on the total quantity of monomers and rubber), it is however evident that -- consideration must be given to the fact that depending on the polymerization temperatur~ and shearing temperatures,on the moment of the addition and on the half life a more or less im-portant part of the cross-linking initiator will be decomposed at the beginning of the cross-linking. The selection of the initiator with respect to its half life, the quantity and the moment of addition and the polymerization and shearing tempe-rature are to be adjusted to each other such that after termi-nation of the shearing the initiator will be present in the po-lymer in a sufficient amount of about 0.02 to 0.3 weight %, preferably of 0.08 to 0.3 weight %, calculated on the total quantity of monomers and rubber, so as to guarantee the cross-linking of the polymer.
As a cross-linking initiator to be used according to the - invention there is added preferably an organic peroxide having 29 a half life of at least 5 hours at 120C.

- 7 - ~-lV9 V~OU HOE 75/F 344 The following cross-linking initiators may stand for examples dicumyl peroxide, 2,5-di-(t-butyl peroxy)-2,5-dimethyl hexane, 1,4-bis-(2-t-butylperoxy-isopropyl)-benzene, 3-t-butyl-peroxy-3-phenyl-phthalide, t-butylhydroperoxide, cumene-hydro-peroxide, di-t-butyl peroxide, 3,3,6,6,9,9-hexamethyl-cyclo-1, 2,4,5-tetraoxanonane, di-t-amylperoxide, t-butyl-1,1,3,3-tetra-methylbutyl peroxide, bis-(t-butylperoxy)-diphenyl-silane, t-amylhydroperoxide, bis-(t-butylperoxy) dimethylsilane, t-butyl-peroxy-trimethylsilane, ;ris-(t-butylperoxy)-vinylsilane, 2,4-pentadione peroxide, 2,5-dimethyl-2,5-bis-(hydroperoxy)-hexane, 2,5-dimethyl-2-t-butylperoxy-5~hydroperoxy hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexine-(3), ~ ,c~ -bis-(t-butylperoxy)-diisopropylbenzene.
Di-t-butyl peroxide is preferably used. T~s peroxide, owing to its relatively long half life, may be added prior to or in the course of the prepolymerization (in case that the poly-merization is effected:~n two steps), without running the risk of excessive decomposition during the polymerization and the following shearing in an extruder. The shorter the half life of the cross-linking initiator, the larger must be the quantity added and/or the later must the addition be effected at the given polymerization and shearing temperatures. These relations may be readily estimated by one skilled in the art and be de-termined quantitatively by a few control tests.
The indication that the addition of the cross-linking ini-tiator to be used according to the process of the invention may be effected also in the course of the polymerization is to be understood to mean that there must be still a sufficiently lon~
29 period of time for a homogeneous distribution of the cross-link-8 - ~ .

ing initiator in the polymer prior to the end of the polymeri-zation. It is ~uite evident that such a homogeneous distri-bution may not be assured, i-f the cross-linking initiator to be used according to the process of the invention is not added until just before termination of the polymerization. Therefore the cross-linking initiator should be added generally not later than the time at which a conversion of about 80 ~ has been ob-tained. This is also the rea~on why peroxides having a half life of at least 5 hours at 120C and thus permitting an early addition are preferably used for the process of the invention.
In a preferred embodiment of the process of the invention there are added, besides the cross-linking initiator, 0.02 to 0.5, preferably 0.05 to 0.3 weight % of a phenolic heat sta-bilizer, e.g. 2,6-di-t-butyl-4-methylphenol, 4-hydroxy-3,5-di-t-butyl-phenyl-propionic acid octadecyl ester, tetra-(4-hydroxy-3,5-di-t-butylphenyl propionic acid)-pentrae~rite ester, bis-(4-hydroxy-3,5-di-t-butylphenyl)-methane, 1,4-bis-(4'-hydroxy-3'-butyl-6'-methylphenyl)-butane, bis-(4-hydroxy-3-t-butyl-6-methylphenyl)-sulfide, 1,1,3 tris-(4-hydroxy-3-t-butyl-6-methyl-phenyl)-butane, 4-hydroxy-3,5-di-t-butyl anisol or bis-~3,3-bis(4'-hydroxy-3'-t-butylphenyl)butanic acid7 glycol ester.
The resulting polymer substantially consits of a random copolyr,ler of aa) and ab), of a graft copolymer of aa) and ab) on b) and of practically non-cross-linked EPT rubber. The lat-ter is present in the form of relatively coarse particles having an average size of 5 to 500 ~m and being imbedded in the matrix of the random copolymer. The polymer additionally contains 0.01 to 5 ~ of residual monomer.
The shearing extrusion is carried out in one or several, 29 preferably in one to four, shearing ~ections (where the extruder lO9VSOO HOE 75/F 34~

screw(s) is(are) fitted with shearing elements) of an extruder with one or several screws, in such a way that the material has a temperature of from 150 to 350C and that the average resi-dence time of the material in the shearing zone(s) varies from 5 seconds to 5 minutes, preferably from 10 to 60 seconds. The temperature of the material is influenced by the external heat-ing, by the geometric shape of the shearing section(s) and by the circumferential speed of the screw(s), while the average residence time of the material in the shearing zone(s) is de-termined by the geometric measurements of this(these) shearing zone(s) and by the throughp~t rate. The essential point is that the shearing is continued until the rubber particles have an average size of below 1 ~m, preferably of below 0.6 ~m.
Contrary to known processes, in which relatively large rubber-particles are cross-linked,according to the process of the invention substantially rubber particles which have been comminuted by shearing are cross-linked,preferably to an extent of > 98 %. Nevertheless, the cross-linking reaction may well start during the comminution while shearing goes on, however shearing must not be interrupted by cross-linking. However, the cross-linking which determines the morphology takes place after leaving the last shearing zone of the extruder.
The sheared rubber particles may be cross-linked in the same extruder, wherein shearing had been carried out before.
But the cross-linking may be effected as well in a subsequent container in which the motion of the material is not caused by mechanical devices. It is also possible that the cross-linking begins in the extruder and is continued in a subsequent contalner.
29 Suitable subsequent containers are especially pipes, static mixers ~09V500 and reaction towers. Particularly uniform products are ob-tained when static mixers are used, as compared to those obtained by the use of reaction pipes or reaction towers. In order to be able to maintain a given cross-linking temperature, the sub-sequent containers are heated externally. Similarly to the ex-truder, the product leaves the cross-linking container through a perforated plate or a sieve plate and is then granulated in kno~n manner.
The cross-linking temperature generally ranges from 150 to 400C, preferably from 200 to 350C. The cross-linking time which determines the dimensioning of the space to serve this purpose in the extruder or in,/the subsequent container, ranges from 10 seconds to 60 minutes. The chosen temperature will be relatively high, if only a short cross-linking tlme can be em-ployed, e.g. in an extruder; on the other hand, if the purpose is to cross-link the rubber as gently as possible at a low tem-perature, a relatively long cross-linking time has to be chosen.
Moreover, the choice of cross-linking temperature and cross-linking time must also take into consideration the chosen con-tent of cross-linking initiator.
The cross-linking has attained a sufficient degree, when the rubber particles do not exhibit any substantial deformation under shearing stress on processing machines. This factor, as well as the rubber particle size,can be controlled electron mi-croscop~ally thin slices after having been submitted to a thorough treatment- ~ith osmium tetroxide.
In a preferred embodiment the cross-linking is effected under reduced pressure, for example on a so-called degassing 29 extruder. In the cross-linking section a reduced pressure of 1 1 _ . .-109U~00 10 to 700 mm ~g, preferably 30 to 400 mm Hg, is created via a common degassing socket-piece and the product is freed from volatile components. Degassing may also be carried out in the metering zones between two shearing zones.
The shearing extrusion may be effected in the presence of the usual plastics additives, for example heat stabilizers, light stabilizers, anti-static agents, lubricants and color pigments.
The admixture of these materials being usually desirable per se, the shearing extrusion does not mean an additional processing step. In the case of a mass/suspension polymerization it is most useful to blend the granular polymer with the additives after drying in known manner, while in the case of a mass polymeriza-tion the feed-in of a concentrated additive into the extruder is preferably effected by means of a side extruder.
Surprisingly, neither does the presence of lubricants im-pair the shearing nor does the presence of stabilizers interfere with the cross-linking.
The process has the advantage that the residual monomer content of the polymer decreases during the shearing extrusion and the cross-linking operation. This fact permits to either cut the polymerization time and/or to keep the residual monomer contentslower than those achieved with known processes.
Surprisingly, when processing in accordance with the pre-sent invention, produchts are obtained which are characterized -by an excellent combination of the properties thoughness, hard-ness and gloss such as the conventional mass/suspension or mass polymerization could not produce it hitherto.
An important advahtage of the process accordil1g to the in-29 vention resides in the fact,that the processing step~ which had - 12 - ~

~09VS00 HOE 75/F 344 been required in the past by the known processes for preparing similar products hereinabove cited in the introductory para-graphs - such as the separate manufacture of graft copolymers or the application of high shearing forces during prepolymeri-zation - are no more necessary.
The ~roducts being manufactured according to the process of the invention are suitable for the production of all shaped articles which are known to be made of ABS polymers. The high surface gloss and the excellent weatherability recon~end these products for the manufacture of e.g. casings for radios, tele-vision sets and lawn mowers, of garden furniture, plates and dishes for use in camping, boat hulls.

The following examples illustrate the invention:
E X A M P L E S
E X A M P L E 1:
28.4 kg of EPT rubber (composition: about 50 weight % of ethylene, about 40 weight ~ of propylene and 10 weight % of 5-ethylidene-norbo~ene-2-units; viscosity according to Moon~y =
9l0 - in the form of pieces cut to small sizes ~ere dissolved in 102.8 kg of styrene and 3.29 kg of~lite oil (boiling point ranging from 100 to 300C) within 4 hours at 50C in a poly-merization apparatus comprising a 300 l pressure vessel for the mass polymerization (prepolymerization) which was equipped with an impeller agitator,a baffle, a reflux cooler with con-trol valve, a bottom valve and with external cooling as well as heating means. Subsequently were added 33.1 kg of acrylonitrile, 329 g of di-t-butyl peroxide as cross-linking initiator and 29 329 g of dimeric ~ -methyl styrene. During this latter operation - 13 - ~

lO9QSOO

the rubber precipitated in the form of a compact swollen gel.
l~er,~
The contents of the vessel rereheated to 115C within 20 minutes,-the EPT rubber gel dissolving again. Agitation at this tempe-rature was continued while effecting external and reflux cooling of operating the control valve towards the reflux cooler for so long a period until the reaction mixture had achieved the phase inversionat-a solid matter content of about 35 ~. The vessel contents ~e~ then cooled within 15 minutes to 65C by means of external cooling and cooling by expansion via the reflux cooler.
Subsequently a mixture of 765 g of a 75 % water-containing di-benzoyl peroxide, and of 164 g of 2,6-di-t-butyl-4-methylphenol and 164 g of 4-hydroxy-3,5-di-t-butylphenyl propionic acid octa-decyl ester as stabilizers, and of 765 g of styrene was added while stirring the prepolymer mixture t~roughly. The contents of the prepolymerization vessel (p-vessel)wer~ then forced through the bottom valve and the feed-in pipe into the 700 1 suspension polymerization pressure vessel (s-vessel) equipped with an impeller agi*ator, a baffle, a bottom valve, a feed pipe from the prepolymerization vessel and with external cooling as well as heating means, in which a solution consisting of 255 g of polyvinyl alcohol (having a saponification dec~ree of 88 ~ and a solution viscosity of 40 centipoises, measured on a

4 weight % aqueous solution at 20C), of 5 g of ethylene diamine tetra-sodium acetate, of 5 g Qf sodium pyrophosphate and 22S l of water was stirred vigorously. The resulting suspension was agitated successively for one hour at 80C, for one hour at 85C, for one hour at 90C and for three hours at 100C, after which period a conversion rate of 98.9 % was obtained. The 29 suspension was then d~charged through the bottom valve of the - 14 ~

~OE 75/F 344 ~090500 s-vessel onto a filter and after separation of the liquid, the polymer was washed twice with water and dried in an air current at 80C within three hours. The product still contained about 92 % of the employed cross-linking initiator.
The shearing extrusion and the cross-linking in the presence of the cross-linking initiator was carried out on a commercial-ly available double ~rew extruder having the trade name of ZSK
53/v and being a product of Messrs. Werner & Pfleiderer, W.
Germany. The two mating screws having each two shearing zones, separated by a metering zone, of a diameter of 53 mm and a length of 36.5 D, were driven by a 32 kW-motor with 270 `~pm. The cas-ing was divided in seven segments, which independently of each other could be heated electrically or cooled with water under the control of a regulator. The extruder was additionally equipped with a degassing socket being located about 60 cm before the extruder outlet and in which a vacuum pump produced a pres-sure of 0.05 bar. The 10 granulate strand leaving the extrusion head were out to chips in a strand granulator after having been cooled in water. The average residence time of the material in the shearing zones was about 8 seconds and in the cross-linking zone after the second shearing zone about 15 seconds. The shear-ing temperature (temperature of the material during shearing) was 270C measured at a location 7 cm farther from the end of the first shearing zone and the cross-linking temperature (tem-perature of the material during cross-linking) was 290C, mea-sured at the extrusion head. The average residence times in the shearing and cross-linking zones respectively of the extru-der were determined approximately on the basis of the average 29 residence time of the copolymer in the total extruder and of the - 15 - w ~

HOE_75/F 3~4 109~500 length of the shearing and cross-linking zones respectively.
The product characteristics are represented in table 1.

Example 1 was repeated with the following modifications:
Prior to prepolymerization 165 g of di-t-butyl-peroxide were added to the EPT rubber solution instead of 329 g, the prepoly-merization was carried out at a temperature of 120C instead of 115C untila solid matter content of about 35 % was achie~eq and after having cooled to 65C an additional quantity of 820 g of tris-(t-butylperoxy-)vinylsilane (50 % moisture) was added as a second cross-linking initiator. The shearing extrusion and the cross-linking were carried out in the same way as des-cribed in Example 1. The pxoduct is described in table 1.
E X A M P L E S 3 to 6:
Example 1 was repeated with the modifications of the pre-polymerization as stated in table 2. The n-dodecyl mercaptan and ~ -methyl styrene mentioned therein were added to the rub-ber solution prior to the prepolymerization. The descriptions of the products are shown in table 1.
Table 2-. Modifications of Examples 3 through 6 as compared - to Example 1.

Example 3 4 5 6 Dimeric ~-Methylsty-rene kg 0.658 0.329 0.670 0 n-Dodecylmercaptan kg 0~033 0 0.034 0 White Oil kg 3.29 0 3.29 3.29 EPT Rubber kg 28.4 28.4 22.0 22.0 ~ -Methylstyrene kg 0 0 0 38.4 Styrene kg 102.8 102.8 10g.5 71.1 .

l~9~

Table 1: ~escriptions of the products referring to Examples 1 through 6 Example 1 2 .
.~verage size of the EPT rubber particles 0;4 O,2 t~m) impact strength % no break 60 40 (DIN 53 453) at 23C (kg cm/cm2) 72 63 at -40C (kg cm/cm2) 60 57 _ _ ._ .. . __ Notched impact strength (DIN 53 453) at 23C (kg cm/cm2) 20.9 9.0 gloss (ASTM D-523-67) (%) 72 95 gloss ~ccording to Lange) (~) 89 > 100 . _ ................. .. _ _ ball indentation hardness .
(DIN 53 456) (kg/cm~) 990 1026 _ __ . _ ...
melt index MFI 220/10 (g/10') . (DIN 53 735) . 11.0 14.6 shear stability of the EPT rubber par-. yes yes , ticles upon re-granulation .
+ at an angle of incidence of 60 ++ referring to a black glass standard according to Bruno Lange;
the measuremen~ were carried out on a Lange-gloss measuring apparatus (45) 1~9VS~O

Table 1 continued .

Example 3 4 Average size of the EPT 0.2 0.1 rubber particles (~m) .
Impact strength % no bxeak 30 100 (DIN 53 453) at 23C (kg cm/cm2) 63 at -40C (kg cm/cm2) 53 70 _ Notched impact strength (DIN 53 453)at 23C (kg cm/cm2) 13.6 9.5 Gloss (AST~ D-523-67) (%) 80 90 Gloss (according to Lange) (~) _ 710Q

Ball indentation hardness (DIN 53 456) ~kg/cm2) 988 1000 melt-index ,~I 2~0/ g , 13.4 13.4 Shear stability of the EPT rubber parti-cles upon re-granulation yes yes + at an angle of incidence of 60 ++ referring to a black glass standard according to Bruno Lange; the measurements were carried out on a Lange-gloss measuring apparatus (45).

- 18 - f 109~500 HOE 75/F 344 Table 1 continued Example 5 6 verage size of the EPT rubber partic- 0.3 0.1 les (~m) _ _ _ Impact strength % no break 20 0 (DIN 53 45~) a~-23C (kg cm/cm2) 61 67 at -40C (kg cm/cm2) 63 42 . ._ _._ ¦ otched impact strength (DIN 53 435) at 23C (kg cm/cm2) 10.1 14.1 Gloss (AS~M-D-523-67) (%) 83 80 Gloss (according to Lange) (%) 91 ? 100 __ _ .
Ball indentation hardness (DIN 53 456) (kg cm/cm2) 1022 1013 melt index MFI 220/10 (g/10') (DIN 53 735) . 23.8 22.7 . _.. .
Shear stability of the EPT rubber yes yes particles upon re-granulatlon - ~ at an angle of incidence of 60 ++ referring to a black glass standard according to.~runo Lange; the measurementSwere carried out on a L~nge-gloss - measuring apparatus (45).

1 9 _ ~, ~

1~9~SOO EIOE 75/F 344 E X A M P L E S 7 through 13:
, Polymerization was carried out according to Example 1, and the shearing extrusion and the cross-linking of the poly-mer were effected on the double-crew extruder described in example 1. The screws employed here diferred by their number of shearing zones, and further modifications related to tempe-ratures and residence times for the shearing and cross-linking The details of theses modifications are stated in table 3.
The products obtained are described in table 4.

.
Table 3: Shearing and cross-linking conditions of examples 7 through 13 ¦Example 7 8 9 10 11 12 13 ~nu ber of t~ e shearing ¦ I ¦ 1 ¦ 1 ¦ 1 ¦ 4 ¦ 1 ¦ 1 ¦

shearing temperature C
. (after the 1st shearing- 160 210 240 160 260 200 320 average residence time 8 12 6 10 20 10 15 in sec. s~earing zones cross-linking tempera- 285285 345 285 275 240300 ¦

average residence time I ~ IInk~nq ¦ 60 ¦ 55 ~ 25 1 50 1 15 1 20 1 20¦

f - .

. -l~9-~SOO HOE 7S/F 344 Table 4: Description of the products of Examples 7 through 13 Example 7 8 _ _, Average size of the EPT-rubber partic- 0.2 0.2 les (~m) . . .
impact strength % no break 60 100 (DIN 53 453) at 23C (kg cm/cm2) 63 _ at -40C (kg cm/cm2) 81 67 ,.___ notched impact strength (DIN 54 453)at 23C (kg cm/cm2) 24.916 __ Gloss (ASTM D-523-67) (%) 86 94 Gloss (according to Lange) (%) 100 95 .__ _ ball indentation hardness (DIN 53 456) (kg cm/cm2) . 1020 1025 . _ _ _ . .. __ melt index MFI 220/10 (g/10') (DIN 53 735) 11.3 Shear stability of the EPT-rubber par- yes yes ticles upon re-granulation __ -+ at an angle of incidence of 60 ++ referring to a black glass standard according to Bruno Lange; the m~asurements were carried out on a Lange-gloss measurir.g apparatus (45).

10~)5UV HOE 75/F 344 Table 4 continued xample 9 10 _ verage size of the EPT-rubber par- 0.3 0.1 ticles (~m) _ . ._ impact strength % no break 60 100 (DIN 53 453) at 23C(kg cm/cm2 ) 74 at -40C(kg cm/cm2 ) 53 71 - -- _ _ otched impact strength (DIN 53 453) at 23C(kg cm/cm2) 18.1 17 ...__ loss (ASTM D - 523-67) (~) 93 96 ¦ loss (according to Lange) (%) 96 ~ 100 __ ._............................ _ all indentation hardness (DIN 53 456) (kg cm/cm2) _ ...................... :_ . _ .
elt index MFI 220/10 (g/10') 13.9 10.7 (DIN 53 735) _ ._ hear stability of the EPT-rubber par-yes yes icles upon re-granulation __ __ __ . _ .__ - + at an angle of incidence of 60 ++ referring to a black glass standard according to Bruno Lange; the measuremen~ were carried out on a Lange-gloss measuring apparatus (45).

.

- 22 - ~

_ ble 4 continued Example 11 12 13 .
Average size of the EPT-rubber par-. 0.2 0.3 0.2 ticles (~m) . ____ impact strength ~ no break 80 100 70 (DIN 53 453) at 23C (kg cm/cm2) 84 _ 68 at -40C (kg cm/cm2) 58 77 66 .~
notched impact strength 10.8 20.2 19 (DIN 53 453) at 23C (kg cm/cm2) . ._ Gloss (ASTM D-523-67) (~ 92 79 88 Glosfi ~according to Lange) (~) ~100 87 98 ball indentation hardness (DIN 53 456) (kg/cm2) 959 1010 990 .
melt index MFI 220/10 (g/10') 10.7 4.2 8.8 (DIN 53 735) _ ._ . . .
shear stability of the EPT-rubber par-yes yes yes ticles upon re-granulation .

at an angle of incidence of 60 ++ refer~ing to a black glass standard according to Bruno Lange; the measurements were carried out on a Lanye-gloss measuring apparatus (45).

. - 23 - ~.

1~5~ HOE 75/F 344 E X A ~ P L E S 14 throu~h 16:
_ The polymerization was carried out ascording to example 1.
The obtained polymer was blended in a common Henschel-mixing de-vice for pulverulent substances, with the following additives:
Example 14: 2.0 % of a commercially available titanium dioxide, being dispersable in plastics and made water-repel-lent Example 15: 0.3 ~ of 2,6 di-t-butyl-4-methylphenol as heat sta-bilizer Example 16: 0.3 % of 2.6-di-t-butyl-4-methylphenol as heat sta-bilizer and 0.15 % of N-2-(2'-hydroxy-S'-t-butyl-phenyl)-benzotriazol as light stabilizer.
The shearing extrusion and the cross-linking of the mix-ture was effected in accordance with example 9. The resulting product characteristics are shown in table S.
E X A M P L E 17:
The polymerization was carried out in accordance with Exam-ple 1. The shearing extrusion and the cross-linking were carried out in a double-screw extruder (20 D) manufactured by machine-factory Paul Leistritz, NUrnber~,W.-Germany,with a subsequent static mixing tube. The screwshaving a 34 mm diameter were driven by a 4 kW motor with 70 rpm. The shearing zone was lo-cated next to the head of the screw, so that the cross-linking operation took place substantially in the mixing tube. The sta-tic mixing tube had an inside diameter of 37.5 mm and a length of 1800 mm and could be heated electrically from the outside in the same way as the extruder. The shearing temperature (tem-perature of the material) was 180C, measured at a location S cm behind the shearing æone of the screw, and the cross-link-ing temperature (temperature of the matexial) was 230C, measured lO9~S~U HOE 75/F 344 at the outlet nozzle. The average residence timeswere 14 se-conds in the shearing zone and about 20 minutes in the static mixing tube. The product characteristics are shown in table 5.
E X A M P L E 18:
Example 17 was repeated under modified cross-linking con-ditions. Screws were employed the shearing zone of which was located in the middle of the screw. 300C was the temperature to which the extruder segments which followed the shearing zone as well as the heating segments of the static mixer were adjust-ed, so that a cross-linking temperature of 305C was attained, measured at the head nozzle of the mixing tube. The average residence time in the total cross-linking zone of the extruder and of the mixing tube was 12 minutes. The product characte-ristics are shown in table 5.
E X A M P L E _19:
Example 17 was repeated in such a manner that the static mixing tube was replaced by a heated tube without mixing ele-ments. This tube had a length of 1200 mm and an inside diameter of 30 mm. The polymer processed was the same as in example 3 prior to extrusion. The cross-lin~ing temperature was 280~C
and the average residence time in the tube was about 5 minutes.
The product characteristics are shown in table 5.

_ ZS _ ,.J

~090500 HOE 75/F 344 Table 5 Example 14 15 1 6 color white yello- yello-wish wish _._ improved heat stability no yes yes ..
improved light stability no yes yes _ Impact strength (DIN 53 453) at 23C (kg cm/cm2) 75 83 63 at -40C (kg cm/cm2) 71 76 86 . ._._._ notched impact strength .
(DIN 53 453) at 23C (kg cm/cm2 ) 8.8 23.7 22.3 . .
Gloss (ASTM D-523 - 67) (%) 90 92 88 Gloss (according to Lange) (%) 94 90 93 ;~ .
ball indentation hardness (DIN 53 456) (kg/cm2) . _ . melt index MFI 220/10 (g/10') 9.5 9.6 9.7 (DIN 53 735) shear stability of the EPT-rubber yes yes yes particles upon . re-granulation I --:

- + at an angle of incidence of 60 ++ referring to a black glass standard according to Bruno Lange; the measurements were carried out on a Lange-gloss measuring apparatus (45).

Table 5 ~ d ¦Example 1718 19 . . .
Impact strength (DIN 53 453) at 23C (kg cm/cm2 ) 73 81 65 at -40C (kg cm/cm2 ) 6870 62 . . . . ._ __ notched impact strength 1611 .4 9.0 (DIN 53 453) at 23C(kg cm/cm2) .... _ _ _ . ._ Gloss (ASTM D-523 - 67) (%) 89 81 85 Gloss (according to Lange)(%) 85 - 91 88 _ .
ball indentation hardness (DIN 53 456) (kg/cm2) .~ . _ melt index MFI 220/10 (g/10') 7.2 5.916.5 (DIN 53 735) _ ._ ._ .. _ shear stability of the EPT-rubber yes yes yes particles upon re-granulation _ _ . . _ + at an angle of incidence of 60 ++ referring to a black glass standard according to Bruno Lange; the measurements were carried out on a Lange-gloss measuring apparatus (45).

- 27 - ~.~' - 1090~00 COMPAR~TIVE EXAMPLES
COMPARATIVE EXAMPLE 1:
The polymerization was carried out in the same way as in Example 1. But this was not followed by any shearing extrusion and cross-linking operation. The product characteristics are compiled in table 6.
COMPARATIVE EXAMPLE 2:
The polymerization was carried out in the same way as in Example 1. However, prior to discharging the suspension onto the filter, the EPT rubber was cross-linked by stirring the sus-pension for five hours at 140C. Subsequently a filtering and drying operation took place in accordance with Example 1. The shearing extrusion was omitted. The product characteristics are compiled in table 6.

!
` The polymerization was carried out in the same way as in Example 1. The polymer was submitted to shear extrusion and cross-linking on a laboratory scale extruder manufactured by Maschinenfabrik Alpine, Augsburg, W.-Germany, and available under the denomination HS 35 being equipped with a shearing means located next to the screw head, the extruder having been connected to the static mixiny device described in Example 17.
The shearing temperature was 190C, measured immediately behind the shearing zone at the static mixer inlet, the average re-sidence time in the shearing zone being; from 1 to 2 seconds.
the cross-linking temperature was 230C measured at the outlet nozzle of the mixing tube, and the average residence time during the cross-linking operation was about 20 minutes. The product 29 characteristics are shown in table 6.

11~9V~.OO HGE ?5/F 344 CO~IP~RATIVE E~Ai~PLE 4:
The procedure described in example 7 was repeated in such a manner that screws with shearing zones shortened by 2/3 of their length were employed. The average residence time in the shearing zone was 2.5 seconds, the shearing temperature was 200C, the cross-linking temperature 245C and the average re-sidence time in the cross-linking zone was 30 seconds. The pro-duct characteristics are shown in table 6.

` lO~SOO HOE 75/F 344 Table 6: Descrip~ion of the products of comparative Examples 1 to 4 Comparative ~xample 1 2 _ ~verage size of the EPT-rubber 15 5 particles ~m) ._.. ...._ _ Impact strength (DIN 53 4~3-) at .23C(kg cm/cm2) 51 42 at -40C(kg cm/cm2) 25 22 _._ notched impact strength 7.7 7.4 (DIN 53 453) at 23C(kg cm/cm2) ..._. .
Gloss (ASTM D-523-67) (%) 49 _ : Gloss (according to Lange) (%) 46 35 ball indentation hardness (DIN 53 456) (kg/cm2) .. _ .............. . . _ _ melt index MFI 220/10 (g/10') 2.0 3 2 .
(DIN 53 735) .
. . . _ shear stability of the EPT-rubber no yes particles upon .re-granulation - __ ..

+ at an angle of incidence of 60 referring to a black glass standard according to Bruno Lange; the measuramen~ were carried out on a Lange-gloss measuring apparatus ~ 45 ~ . -lO~OSOO ~ ~ ~

Table 6 continued v7- ~

Comparative Example 3 4 Average size of the EPT-rubber 4 2.5 particles ~m) Impact strength .
(DIN 53 453) at 23C(kg cm/cm2) 75 68 at -40C(kg cm/cm2) 51 65 . .
notched impact strength (DIN 53 453) at 23C(kg cm/cm2) 8.0 . 12.3 Gloss (ASTM D-523-67) (%) 48 52 Gloss (according to Lange) (%) 53 58 ball indentation hardness (DIN 53 456) (kg/cm2) melt index MFI 220/10 (g/10') _ 8.1 (DIN 53 735) shear stability of the EPT-rubber yes yes particles upon re-granulation + at an angle of incidence of 60 +~ referring to a b~ack glass standard according to Bruno Lange; the measuremen~ were carried out on a Lange-gloss mea~Xing apparatus (45).

Claims (12)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the preparation of an impact resistant copolymer exhibiting a high gloss in which a mixture of (a) 98 to 70 weight % of a mixture of (aa) 90 to 60 weight % of styrene, at least one styrene derivative or a mixture thereof, with (ab) 10 to 40 weight % of acrylonitrile, at least one other copolymerizable derivative of acrylic acid, or a mixture thereof, with (b) 2 to 30 weight % of an ethylene-propylene-tertiary compo-nent rubber (EPTR), the quantities (aa) and (ab) being calculated on the total quantity (aa) + (ab) of the monomers and the quantity (a) + (b) being calculated on the total quantity of (a) + (b) of monomers and EPTR, is subjected to radical mass polymerization or mass/suspension polymerization, the resultant copolymer containing 0.02 to 0.5 weight % of a cross-linking initiator is subjected to a shearing extrusion until the rubber particles have an average size of below 1 um, and the rubber particles are subsequently cross-linked.

2. A process as claimed in claim 1, in which the cross-linking initiator has a half life of at least 5 hours at 120°C.

3. A process as claimed in claim 1 in which the copolymer, prior to shearing, contains from 0.02 to 0.05 weight % of a phenolic heat stabilizer.

4. A process as claimed in claim 1, claim 2 or claim 3 in which the shearing is carried out at a temperature of the mixture of 150° to 350°C.

5. A process as claimed in claim 1, claim 2 or claim 3 in which the copolymer is subjected to shearing for a period of from 5 seconds to 5 minutes.

6. A process as claimed in claim 1, claim 2 or claim 3 in which the cross-linking of the rubber particles is carried out at a temperature of the mixture of 150 to 400°C.

7. A process as claimed in claim 1, claim 2 or claim 3 in which the copolymer is subjected to cross-linking for a period of from 10 seconds to 60 minutes.

8. A process as claimed in claim 1,-claim 2 or claim 3 in which volatile components are eliminated from the copolymer during cross-linking.

9. A process as claimed in claim 1, claim 2 or claim 3 in which the cross-linking is carried out without imparting any motion to the polymer by mechanical means.

10. A process as claimed in claim 1, claim 2 or claim 3 in which (a) comprises 92 to 75% by weight of (aa) 90 to 70% of styrene, at least one styrene derivative or a mixture thereof with (ab) 10 to 30 weight % of acrylonitrile, at least one other copolymerizable derivative of acrylic acid or a mixture thereof, in admixture with (b) 8 to 25 weight % of EPTR.

11. A process as claimed in claim 1, claim 2 or claim 3 in which (b) comprises a terpolymer of 69.5 to 30 weight % of.
ethylene, 30 to 69.5 weight % of propylene and 0.5 to 15 weight % of a non-conjugated diene having at least 5 carbon atoms.

12. An impact-resistant styrene copolymer, whenever obtained according to a process as claimed in claim 1, claim 2 or claim 3.