Flame-resistant polycarbonate ABS molding materials

Details Flame-resistant polycarbonate ABS molding materials Flame-resistant polycarbonate ABS molding materials

2000-02-04

2002-09-03

Medley, Margaret (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C525S067000, C525S462000

Reexamination Certificate

active

06444735

ABSTRACT:

The present invention relates to polycarbonate/ABS moulding compositions which have been rendered flame-resistant with phosphorus compounds, which have an outstanding set of mechanical properties, in particular an outstanding resistance to stress cracking, and are flame-resistant.
EP-A 0 174 493 describes flame-resistant, halogen-containing polymer mixtures consisting of aromatic polycarbonate, styrene-containing graft copolymer, monophosphates and a specific polytetrafluoroethylene formulation. Although these mixtures have adequate fire resistance and mechanical properties, the surface quality of moulded items may be impaired when using high processing temperatures. The moulded items also exhibit some deficiencies in stress crack resistance.
EP-A 0 363 608 describes polymer mixtures consisting of aromatic polycarbonate, styrene-containing copolymer or graft copolymer and oligomeric phosphates as flame-resistant additives. The stress crack resistance of these mixtures is often not sufficient to enable the production of thin-walled housing parts.
EP-A 771 851 describes moulding compositions which contain aromatic polycarbonate, graft copolymer based on a diene rubber, an SAN copolymer, a phosphate and tetrafluoroethylene polymers, wherein the polycarbonate has a variety of molecular weights. However, no very finely divided inorganic compounds are described as a constituent of the moulding compositions.
The object of the present invention was to provide flame-resistant polycarbonate/ABS moulding compositions which have outstanding stress crack resistance as well as very good processing properties and which are particularly suitable for producing thin-walled housing parts.
Surprisingly it was found that polycarbonate/ABS moulding compositions which have a greatly improved stress crack resistance are produced by using specific mixtures of polycarbonates, each with clearly differentiated solution viscosities, combined with very finely divided inorganic compounds.
Therefore the invention provides flame-resistant, thermoplastic moulding compositions containing
A 5 to 95, preferably 10 to 90, in particular 20 to 80 parts by weight of a mixture of two aromatic polycarbonates A.1 and A.2 with different solution viscosities, wherein
1. the relative solution viscosity of A.1 is 1.18 to 1.24,
2. the relative solution viscosity of A.2 is 1.24 to 1.34 and
3. the difference between the relative solution viscosities of A.1 and A.2 is equal to or greater than 0.06,
wherein one or more further polycarbonates may be added to the mixture of A.1 and A.2,
B 0 to 50, preferably 1 to 30, in particular 2 to 25 parts by weight of a (co)polymer consisting of 1 or at least 2 ethylenically unsaturated monomers.
C 0.5 to 60, preferably 1 to 40, in particular 2 to 30 parts by weight of graft polymers, obtainable by graft polymerisation of at least two monomers selected from the group consisting of chloroprene, butadiene, isoprene, styrene, acrylonitrile, ethylene, propylene, vinyl acetate and (meth)acrylates with 1 to 18 carbon atoms in the alcohol component,
D 0.5 to 20 parts by weight, preferably 1 to 18 parts by weight, in particular 2 to 15 parts by weight of a phosphorus compound of the formula (1)
 in which
R
1
, R
2
′ R
3
and R
4
, independently of each other, represent an optionally halogenated C
1
-C
8
alkyl group, or a C
5
-C
6
cycloalkyl, C
6
-C
20
aryl, or C
7
-C
12
aralkyl group, each optionally substituted by halogen and/or C
1
-C
4
alkyl groups
n each, independently, represents 0 or 1
N is 0 to 30 and
X represents a mono- or polynuclear aromatic group with 6 to 30 carbon atoms,
E 0.05 to 5 parts by weight, preferably 0.1 to 1 part by weight, in particular 0.1 to 0.5 parts by weight of a fluorinated polyolefin,
F 0.01 to 50 parts by weight, preferably 0.1 to 10 parts by weight per 100 parts by weight of A to E of very finely divided inorganic compound with an average particle diameter of less than or equal to 200 nm, preferably less than or equal to 150 nm, in particular less than or equal to 100 nm.
The sum of all the parts by weight of A+B+C+D+E+F is 100.
Moulding compositions according to the invention, due to their exceptional flame resistance, stress crack resistance and very good processing properties are particularly suitable for preparing thin-walled moulded articles (housing parts for data processing units), where high processing temperatures and pressures lead to considerable strain on the material used.
Component A
Thermoplastic, aromatic polycarbonates which are suitable for use as component A according to the invention are those based on diphenols of the formula (II)
in which
A represents a single bond or a C
1
-C
5
alkylene, C
2
-C
5
alkylidene, C
5
-C
6
cycloalkylidene, —S—, —SO
2
—, —O—, —CO—or C
6
-C
12
arylene group,
B represents chlorine or bromine,
X is 0, 1 or 2 and
P is 1 or 0
or alkyl substituted dihydroxyphenylcycloalkanes of the formula (III)
 in which
R
11
and R
12
, independently of each other, each represent hydrogen, a halogen, preferably chlorine or bromine, or a C
1
-C
8
alkyl, preferably C
1
-C
4
alky, C
5
-C
6
cycloalkyl, C
6
-C
10
aryl, preferably phenyl, or C
7
-C
12
aralkyl, preferably a phenyl-C
1
-C
4
alkyl, in particular benzyl, group
m is an integer, from 4 to 7, preferably 4 or 5,
R
13
and R
14
can be individually chosen for each Z, and, independently of each other, represent hydrogen or a C
1
-C
6
alkyl group, preferably hydrogen, methyl or ethyl,
and
z represents carbon, with the proviso that, on at least one atom Z, R
13
and R
14
simultaneously represent an alkyl group.
Suitable diphenols of the formula (II) are e.g. 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-dibromo-4-hydroxyphenyl)-propane.
Preferred diphenols of the formula (II) are 2,2-bis4-hydroxyphenyl)propane, 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane and 1,1-bis-(4hydroxyphenyl)-cyclohexane.
Preferred diphenols of the formula (III) are dihydroxydiphenylcycloalkanes with 5 or 6 ring carbon atoms in the cycloaliphatic grouping (m=4 or 5 in formula (III)) such as for example diphenols with the formulae
wherein 1,1-bis-(4-hydroxyphenyl)-3 ,3,5-trimethylcyclohexane (formula (IIIa)) is particularly preferred.
Polycarbonates which are suitable for use as component A according to the invention may be branched in a known way, that is preferably by the incorporation of 0.05 to 2.0 mol %, with respect to the sum of diphenols used, of tri-functional or more than tri-functional compounds, e.g. those with three or more than three phenolic groups, such as for example
phloroglucine
4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-hept-2-ene
4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane
1,3,4-tri-(4-hydroxyphenyl)-benzene
1,1,1-tri-(4-hydroxyphenyl)-ethane
tri-(4-hydroxyphenyl)-phenylmethane
2,2-bis-(4,4-bis-(4-hydroxyphenyl)-cyclohexyl)-propane
2,4-bis-(4,4-bis-(4-hydroxyphenyl)-isopropyl)-phenol
2,6-bis-(2-hydroxy-5′-methylbenzyl)-4-methyl-phenol
2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-propane
hexa-(4-(4-hydroxyphenylisopropyl)-phenyl) orthoterephthalate
tetra-(4-hydroxyphenyl)-methane
tetra-(4-(4-hydroxyphenylisopropyl)phenoxy)-methane and
1,4-bis-((4′-,4′-dihydroxytriphenyl)-methyl)-benzene
A few other trifunctional compounds are 2,4-dihydroxybenzoic acid, trimesic acid, cyanuric chloride and 3,3-bis-(3 methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole.
Preferred polycarbonates, in addition to bisphenol-A homopolycarbonate, are copolycarbonates of bisphenol-A with up to 15 mol %, with respect to the molar sum of diphenols, of 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane.
Some of the aromatic polycarbonates in component A may be exchanged for aromatic polyestercarbonates.
Aromatic polycarbonates in component A may also contain polysiloxane blocks. The preparation of these is described, for example, in DE-OS 33 34 872 and U.S. Pat.

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