Thermoplastic moulding compositions with an improved heat distortion point

The present invention relates to the use of a copolymer with an Mw of 2.times.10.sup.6 to 1.times.10.sup.7 in amounts of 0.5 to 5 parts by weight for improving the heat distortion point of thermoplastic mixtures containing polycarbonates, graft polymers and copolymers, and the thermoplastic mixtures correspondingly rendered dimensionally stable under the influence of heat.

The present invention relates to the use of a copolymer of (a) 95 to 50% by 
weight of a vinylaromatic and (b) 5 to 50% by weight of an ethylenically 
unsaturated nitrile compound and/or an ester of (meth)acrylic acid, which 
has a molecular weight Mw (weight-average) of 2.times.10.sup.6 to 
1.times.10.sup.7, preferably 2.times.10.sup.6 to 5.times.10.sup.6, in 
amounts of 0.5 to 5 parts by weight, in each case based on 100 parts by 
weight of the mixture of polycarbonates, graft polymers and copolymers, 
for improving the heat distortion point of thermoplastic mixtures 
containing polycarbonates, graft polymers and copolymers. 
The invention furthermore relates to thermoplastic mixtures containing 
thermoplastic polycarbonates (A), graft polymers (B) and two types of 
copolymers (C) and (D), preferably (A) 20-75 parts by weight of a 
thermoplastic polycarbonate, (B) 10-50 parts by weight of a graft polymer 
of (B)(1) 5 to 90 parts by weight, preferably 30 to 80 parts by weight, of 
a mixture of (B)(1)(1) 50 to 90% by weight of styrene, 
.alpha.-methylstyrene, nuclear-substituted styrene, methyl methacrylate or 
mixtures thereof and (B)(1)(2) 50 to 5% by weight of (meth)acrylonitrile, 
methyl methacrylate, maleic anhydride, N-substituted maleimide or mixtures 
thereof, on (B)(2), 95 to 10 parts by weight, preferably 70 to 20 parts by 
weight, of a rubber with a glass transition temperature 
TG.ltoreq.10.degree. C., and (C) 10 to 70 parts by weight of a 
thermoplastic copolymer with an Mw of 15,000 to 200,000 (measured by light 
scattering or sedimentation) of (C)(1) 50 to 95% by weignt of styrene, 
.alpha.-methylstyrene, nuclear-substituted styrene, methyl methacrylate or 
mixtures thereof and (C)(2) 50 to 5% by weight of (meth)acrylonitrile, 
methyl methacrylate, maleic anhydride, N-substituted maleimide or mixtures 
thereof, which are characterised in that they contain a copolymer (D) of 
(a) 95 to 50% by weight of a vinylaromatic and (b) 5 to 50% by weight of 
an ethylenically unsaturated nitrile compound and/or of an ester of 
(meth)acrylic acid, with an Mw (weight-average molecular weight) of 
2.times.10.sup.6 to 1.times.10.sup.7, preferably 2.times.10.sup.6 to 
5.times.10.sup.6, in amounts of 0.5 to 5 parts by weight, in each case 
based on 100 parts by weight of the mixture of polycarbonates (A), graft 
polymers (B) and the two copolymers (C) and (D). 
The mixtures according to the invention of polycarbonates, graft polymers 
and copolymers can also contain the usual amounts of the additives 
customary in polycarbonate, graft polymer or copolymer chemistry, such as 
flameproofing agents, stabilisers, pigments, flow control agents, mould 
release agents and/or antistatics. 
DE-OS (German Published Specification) No. 1,964,915 describes the use of 
corresponding copolymers in thermoplastic styrene polymers, thermoplastic 
styrene polymers also including styrene/acrylonitrile copolymers or graft 
polymers of acrylonitrile and styrene on polybutadiene elastomers (page 7 
of DE-OS). Such mixtures, which must be compatible, have an improved 
processability, especially in respect of stretching or elongation during 
thermal deformation of films, and a better foaming ability in the various 
foaming processes. According to British Patent Specification No. 
1,558,835, such copolymers can be used as polymeric modifiers for 
improving the mechanical properties of other polymers (page 3, lines 
114/115). 
According to Japanese Patent Application No. 57 117 505 of Sumitomo Chem. 
KK of 12.1.1981, such high molecular weight polymers are also suitable as 
mixture constituents for improving the mechanical properties. 
To our knowledge, no indication of improved heat distortion point of the 
admixtures according to the invention is to be found in these literature 
references. 
Thermoplastic aromatic polycarbonates of component (A) which are suitable 
according to the invention are homopolycarbonates and copolycarbonates of 
one or more of the following diphenols, chosen from hydroquinone, 
resorcinol, dihydroxydiphenyls, bis-(hydroxyphenyl)-alkanes and 
-cycloalkanes, bis-(hydroxyphenyl) sulphides, ethers, ketones, sulphoxides 
and sulphones and 
.alpha.,.alpha.'-bis-(hydroxyphenyl)-diisopropylbenzenes. 
Thermoplastic aromatic polycarbonates of component (A) which are preferred 
according to the invention are those based on diphenols of the formula (I) 
##STR1## 
wherein A is a single bond, C.sub.1 -C.sub.5 -alkylene, C.sub.2 -C.sub.5 
-alkylidene, C.sub.5 -C.sub.6 -cycloalkylidene, --S-- or --SO.sub.2 --, 
Hal, chlorine or bromine, 
x is 0, 1 or 2 and 
"n" is 1 or zero. 
Diphenols of the formula (I) are either known from the literature or can be 
prepared by processes which are known from the literature. 
The preparation of the polycarbonates of component (A) which are suitable 
according to the invention is known from the literature and can be carried 
out, for example, with phosgene by the phase boundary process or with 
phosgene by the process in a homogeneous phase system (the so-called 
pyridine process), the particular molecular weight to be established being 
achieved in a known manner by a corresponding amount of known chain 
stoppers. 
The polycarbonates of component (A) which are suitable according to the 
invention have mean weight-average molecular weights (Mw, measured, for 
example, by ultracentrifugation or scattered light measurement) of 10,000 
to 200,000, preferably 20,000 to 80,000. 
Examples of suitable diphenols of the formula (I) are hydroquinone, 
resorcinol, 4,4'-dihydroxydiphenyl, 2,2-bis-(4-hydroxyphenyl)-propane, 
2,4-bis-(4-hydroxyphenyl)-2-methylbutane, 
1,1-bis-(4-hydroxyphenyl)-cyclohexane, 
2,2-bis-(3-chloro-4-hydroxyphenyl)-propane, 
2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane and 
2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane. 
Particularly preferred diphenols of the formula (I) are 
2,2-bis-(4-hydroxyphenyl)-propane, 
2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane, 
2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane and 
1,1-bis-(4-hydroxyphenyl)-cyclohexane. 
The polycarbonates of component (A) which are suitable according to the 
invention can be branched in a known manner, and in particular preferably 
by incorporation of 0.05 to 2.0 mol %, based on the sum of the diphenols 
employed, of compounds which are trifunctional or more than trifunctional, 
for example those with three or more tnan three phenolic OH groups. 
Rubbers which are suitable for the preparation of the graft polymers of 
component (B) are, in particular, polybutadiene and butadiene/styrene 
copolymers with up to 30% by weight, based on the weight of rubber, of a 
lower alkyl ester of acrylic or methacrylic acid (for example methyl 
methacrylate, ethyl acrylate, methyl acrylate or ethyl methacrylate). 
Examples of other suitable rubbers are polyisoprene or polychloroprene. 
Alkyl acrylate rubbers based on C.sub.1 -C.sub.8 -alkyl acrylates, in 
particular ethyl, butyl and ethylhexyl acrylate, are furthermore suitable. 
These alkyl acrylate rubbers can optionally contain up to 30% by weight, 
based on the weight of rubber, of copolymerised monomers, such as vinyl 
acetate, acrylonitrile, styrene, methyl methacrylate and/or vinyl ether. 
These alkyl acrylate rubbers can furthermore contain relatively small 
amounts, preferably up to 5% by weight, based on the weignt of rubber, of 
ethylenically unsaturated monomers with a crosslinking action. Examples of 
such crosslinking agents are alkylene diol di(meth)-acrylates, polyester 
di-(meth)-acrylates, divinylbenzene, tri-vinylbenzene, triallyl cyanurate, 
allyl (meth)-acrylate, butadiene or isoprene. Such alkyl acrylates are 
known. Acrylate rubbers as the graft base can also be products which 
contain a crosslinked diene rubber of one or more conjugated dienes, such 
as polybutadiene, or a copolymer of a conjugated diene with an 
ethylenically unsaturated monomer, such as styrene and/or acrylonitrile, 
as the core. Examples of other suitable rubbers are EPDM rubbers, that is 
to say rubbers of ethylene, propylene and a non-conjugated diene monomer.

Preferred rubbers for the preparation of the graft polymers (B) are diene 
monomer and alkyl acrylate rubbers. 
The rubbers are present in the graft polymers (B) in the form of at least 
partly crosslinked particles with an average particle size of 0.09 to 5 
.mu.m, in particular 0.1 to 1 .mu.m. The graft polymers (B) are prepared 
by free radical grafting copolymerisation of the monomer mixtures defined 
above, of (B)(1)(1) and (B)(1)(2) in the presence of the rubbers (B)(2) to 
be grafted, and are all known. Preferred preparation processes for the 
graft polymers (B) are emulsion, solution, bulk or suspension 
polymerisation. Particularly preferred graft polymers (B) are the 
so-called ABS polymers. Halogenostyrenes and p-methylstyrene may be 
mentioned as nuclear-substituted styrenes. 
Preferred copolymers of component (C) are those of at least one monomer 
from the series comprising styrene, .alpha.-methylstyrene, halogenostyrene 
and methyl methacrylate of (C)(1) with at least one monomer from the 
series comprising acrylonitrile, methacrylonitrile, methyl methacrylate 
and maleic anhydride of (C)(2). 
Copolymers of component (C) are frequently formed as by-products during 
grafting polymerisation to prepare component (B), especially if large 
amounts of monomer are grafted onto small amounts of rubber. 
The amount of copolymers (C) to be used according to the invention of 10 to 
70 parts by weight, based on 100 parts by weight of (A)+(B)+(C)+(D), does 
not include these by-products of the grafting polymerisation. 
The copolymers of component (C) are resinous, thermoplastic and free from 
rubber. Particularly preferred copolymers (C) are those of styrene with 
acrylonitrile and optionally with methyl methacrylate, of 
.alpha.-methylstyrene with acrylonitrile and optionally with methyl 
methacrylate, or of styrene and .alpha.-methylstyrene with acrylonitrile 
and optionally with methyl methacrylate. 
Particularly preferred weight ratios in the thermoplastic copolymer (C) are 
60 to 80% by weight of (C)(1) and 40 to 20% by weight of (C)(2). 
The copolymers of component (C) are known and can be prepared by free 
radical polymerisation, in particular by emulsion, suspension, solution or 
bulk polymerisation. The copolymers of component (C) have molecular 
weights Mw (weight-average, determined by light scattering or 
sedimentation) of between 15,000 and 200,000. 
The copolymer components (D) to be employed according to the invention are 
thermoplastic and preferably contain styrene, .alpha.-methylstyrene, 
nuclear-substituted styrene or mixtures of these vinylaromatics, as the 
vinylaromatic, methacrylonitrile or acrylonitrile, as the ethylenically 
unsaturated nitrile compound, and methyl acrylate or methyl methacrylate, 
as the ester of (meth)acrylic acid. 
Such copolymers (D) are known (see, for example, DE-OS (German Published 
Specification) No. 1,964,915, Japanese Patent Application No. 57-117 505, 
Japanese Patent Application 52-084 269 and British Patent Specification 
No. 1,558,835), or they can be obtained by the processes known from these 
literature references, or can be prepared by the process described in 
Example 1 of this Application. 
The molecular weights of tne copolymers (D) were determined via gel 
chromatography (in CH.sub.2 Cl.sub.2 at room temperature) utilising the 
universal calibration according to Benoit, or via light scattering 
measurements of solutions of the polymers in dimethylformamide by means of 
a Fica 50 scattered light instrument from ARL (refractive index increment 
dn/dc=0.145). The molecular weights of the copolymers (D) according to the 
invention are weight-average values. 
The mixtures according to the invention containing components (A), (B), (C) 
and (D) and, if appropriate, the customary additives, such as 
flameproofing agents, stabilisers, pigments, flow control agents, mould 
release agents and/or antistatics, are prepared by mixing the particular 
constituents simultaneously or successively at room temperature or at 
elevated temperature in the known manner and subjecting the mixture to 
melt compounding or melt extrusion at temperatures of 200.degree. C. to 
300.degree. C. in customary units, such as internal kneaders, extruders or 
twin-screw extruders. 
The moulding compositions of the present invention can be used to produce 
all types of shaped articles, it being possible to utilise the customary 
production processes, and in particular shaped articles can be produced by 
injection-moulding. Examples of shaped articles which can be produced are 
all types of housing components (for example for domestic appliances, such 
as juice presses, coffee machines and mixers) or covering sheets for the 
construction sector and components for the vehicle sector. The moulding 
compositions according to the invention are also employed in the field of 
electrical engineering, because they have very good electrical properties. 
Another type of processing of the moulding compositions according to the 
invention is the production of shaped articles by deep-drawing from sheets 
or films previously produced by known processes. 
In this Application, particle size always denotes the average particle 
diameter d.sub.50, determined by ultracentrifuge measurements in 
accordance with the method of W. Scholtan et al. Colloids u. Z. Polymere 
250 (1972) 782-796. 
EXAMPLES 
Components employed 
Polycarbonate (A) employed: 
Linear polycarbonate based on bisphenol A, with a solution viscosity of 
1.28, measured in CH.sub.2 Cl.sub.2 at 25.degree. C. and in a 
concentration of 0.5 g/100 ml. 
Graft polymer (B): 
SAN graft polymer of 50% of styrene/acrylonitrile mixture (in a weight 
ratio of 72:28) on 50% of polybutadiene in particle form, with an average 
particle size (d.sub.50) of 0.4 .mu.m, obtained by emulsion 
polymerisation. 
Copolymer (C): 
Styrene/acrylonitrile copolymer with a styrene/acrylonitrile ratio of 70:30 
and a limiting viscosity of [.eta.]=0.75 dl/g (measurement in 
dimethylformamide at 20.degree. C.). 
Preparation of a high molecular weight copolymer (D): 
360 g of styrene, 140 g of acrylonitrile and 30 g of 1-octadecanol are 
dispersed together in 4,090 g of water in a reactor, with stirring, the 
dispersion is warmed to 58.degree. C. and 7.5 g of potassium persulphate 
(dissolved in 660 g ot water) are added. 
After the reaction mixture has been stirred at this temperature for 30 
minutes, a mixture of 3,240 g of styrene and 1,260 g of acrylonitrile is 
metered in over a period of 4 hours, a solution of 25 g of sodium 
n-dodecylbenzenesulphonate in 1,250 g of water being metered in via a 
separate feed line. After an after-reaction time, the latex is coagulated 
with magnesium sulphate/acetic acid and the resulting polymer powder is 
dried at 70.degree. C. in vacuo. The copolymer thus prepared has a 
molecular weight (Mw) of 2.5.times.10.sup.6. 
The heat distortion point was determined by the Vicat (B) method according 
to DlN 53 460/ISO 360. 
The notched impact strength was determined in accordance with the method of 
DIN 53 452/ISO R 179, on flat bars (90 mm.times.10 mm.times.4 mm) witn a 
V-shaped notch with a notch depth of 2.7 mm. 
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(Compar- 
Examples ison) 1 2 3 
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Polycarbonate 
parts by weight 
45 45 45 45 
(A) 
Graft polymer 
" 33 33 33 33 
(B) 
Copolymer (C) 
" 22 21 19 17 
Copolymer (D) 
" -- 1 3 5 
Notched impact 
kJ/m.sup.2 31 34 29 30 
strength 
(room temper- 
ature) 
Heat distortion 
.degree.C. 113 119 116 117 
point (Vicat B) 
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