Flame-resistant molding compounds

Details Flame-resistant molding compounds Flame-resistant molding compounds

1995-01-03

2003-07-08

Buttner, David J. (Department: 1712)

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

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S125000, C524S126000, C525S067000

Reexamination Certificate

active

06590015

ABSTRACT:

This invention relates to flame-resistant poly-carbonate/ABS molding compounds which are considerably improved in their mechanical properties and thermal stability by an addition of polyalkylene terephthalate and an oligomeric phosphate.
EP-A 0 174 493 (U.S. Pat. No. 4,983,658) describes flame-proofed halogen-containing polymer blends of aromatic polycarbonate, styrene-containing graft copolymer, monophosphates and a special polytetrafluoroethylene formulation. Although these blends show adequate burning behavior and mechanical properties, the surface quality of moldings produced from them can be impaired at high processing temperatures. In addition, deficiencies can arise in their resistance to stress cracking.
U.S. Pat. No. 5,030,675 describes flame-resistant thermo-plastic molding compounds of aromatic polycarbonate, ABS polymer, polyalkylene terephthalate and monophosphates with fluorinated polyolefins as flameproofing additives. However, the high resistance to stress cracking is offset by disadvantages in the form of deficiencies in notched impact strength and inadequate heat resistance on exposure to high temperatures, for example during processing.
Diphosphates are known as flameproofing additives. JA 59 202 240 describes the production of one such product from phosphorus oxychloride, diphenols, such as hydroquinone or bisphenol A, and monophenols, such as phenol or cresol. These diphosphates may be used as flameproofing agents in polyamide or poly-carbonate. However, there is no reference in this document to an improvement in heat resistance and notched impact strength by addition of the oligomeric phosphate in conjunction with polyalkylene terephthalates to polycarbonate molding compounds.
EP-A 0 363 608 describes polymer blends of aromatic polycarbonate, styrene-containing copolymer or graft copolymer and oligomeric phosphates as flameproofing additives. The stress cracking resistance of these blends is often too low for the production of thin-walled housing parts.
According to JP 59 193 920, flame-resistant polyesters, such as polyalkylene terephthalates, are obtained by polycondensation of ethylene glycol, terephthalic acid and hydroquinone diphosphate in the presence of antimony oxide, cobalt acetate and inorganic phosphates. However, the blends described in this document show a mechanical property level that is inadequate for numerous applications in the information field. In addition, the use of heavy metals makes the molding compounds in question difficult to reuse.
It has now surprisingly been found that flame-resistant polycarbonate/ABS molding compounds, which combine excellent notched impact strength and stress cracking resistance with very high heat resistance under processing conditions, can be produced providing an additive combination of a polyalkylene terephthalate and an oligomeric phosphate is added. These molding compounds are particularly suitable for the production of thin-walled moldings (housing parts in the field of data processing equipment) where high processing temperatures and pressures impose severe strains on the material used.
The present invention relates to flame-resistant thermoplastic molding compounds of
A) 40 to 98 parts by weight, preferably 50 to 95 parts by weight and more preferably 60 to 90 parts by weight of an aromatic polycarbonate,
B) 0.5 to 40 parts by weight, preferably 1 to 30 parts by weight and more preferably 2 to 10 parts by weight of a polyalkylene terephthalate,
C) 0.5 to 40 parts by weight, preferably 1 to 20 parts by weight and more preferably 2 to 12 parts by weight of a graft polymer,
D) 0.5 to 20 parts by weight, preferably 1 to 18 parts by weight and more preferably 2 to 15 parts by weight of an oligomeric phosphorus compound corresponding to formula (I)
 in which
R
1
, R
2
, R
3
and R
4
independently of one another represent C
1-8
alkyl, C
5-6
cycloalkyl, C
6-10
aryl or C
7-12
aralkyl,
the n's independently of one another are 0 or 1,
N is a value between 0.5 and 5 and
X is a mononuclear or polynuclear aromatic radical containing 6 to 30 carbon atoms, and
E) 0.05 to 5 parts by weight, preferably 0.1 to 1 part by weight and more preferably 0.1 to 0.5 part by weight of a fluorinated polyolefin having a mean particle diameter of 0.05 to 1000 &mgr;m, a density of 1.2 to 2.3 g/cm
3
and a fluorine content of 65 to 76% by weight.
The sum of all the parts by weight A+B+C+D+E is 100.
COMPONENT A
Thermoplastic aromatic polycarbonates A suitable for use in accordance with the invention are those based on diphenols corresponding to formula (II)
in which
A is a single bond, C
1-5
alkylene, C
2-5
alkylidene, C
5-6
cycloalkylidene, —S— or —SO
2
—,
B is chlorine or bromine,
x=0, 1 or 2 and
p=1 or 0, or alkyl-substituted dihydroxyphenyl cycloalkanes corresponding to formula (III)
 in which
R
1
and R
2
independently of one another represent hydrogen, halogen, preferably chlorine or bromine, C
1-8
alkyl, C
5-6
cycloalkyl, C
6-10
aryl, preferably phenyl, and C
7-12
aralkyl, preferably phenyl-C
1-4
—alkyl, more particularly benzyl,
m is an integer of 4 to 7, preferably 4 or 5,
R
3
and R
4
may be individually selected for each Z and, independently of one another, represent hydrogen or C
1-6
alkyl and
z represents carbon, with the proviso that, at at least one atom Z, R
3
and R
4
can both be alkyl.
Suitable diphenols corresponding to formula (II) are, for example, hydroquinone, resorcinol, 4,4′-di-hydroxydiphenyl, 2,2-bis-(4-hydroxyphenyl)-propane, 2,4-bis-(4-hydroxyphenyl)-2-methyl butane, 1,1-bis-(4-hydroxyphenyl)-cyclohexane, 2,2-bis-(3-chloro-4-hydroxy-phenyl)-propane, 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane.
Preferred diphenols (II) are 2,2-bis-(4-hydroxy-phenyl)-propane, 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane and 1,1-bis-(4-hydroxyphenyl)-cyclohexane.
Preferred diphenols (III) are 1,1-bis-(4-hydroxy-phenyl)-3,3-dimethyl cyclohexane, 1,1-bis-(4-hydroxy-phenyl)-3,3,5-trimethyl cyclohexane and 1,1-bis-(4-hydroxyphenyl)-2,4,4-trimethyl cyclopentane.
Polycarbonates suitable for the purposes of the invention are both homopolycarbonates and copolycarbonates.
A may also be a mixture of the thermoplastic polycarbonates defined above.
Polycarbonates may be obtained in known manner from diphenols with phosgene by the interfacial process or with phosgene by the process in homogeneous phase, the so-called pyridine process. Their molecular weight may be regulated in known manner by a suitable quantity of known chain terminators.
Suitable chain terminators are, for example, phenol, p-chlorophenol, p-tert.butyl phenol or 2,4,6-tribromophenol and also long-chain alkylphenols, such as 4-(1,3-tetramethylbutyl)-phenol according to DE-OS 2 842 005 (Le A 19 006) or monoalkylphenol or dialkylphenol containing a total of 8 to 20 carbon atoms in the alkyl substituents according to German patent application P 35 06 472.2 (Le A 23 654), such as 3,5-di-tert.butylphenol, p-isooctylphenol, p-tert.octylphenol, p-dodecylphenol and 2-(3,5-dimethylheptyl)-phenol and 4-(3,5-dimethylheptyl)-phenol.
The chain terminators are generally used in a quantity of 0.5 to 10 mol-%, based on the sum of the diphenols (I) and/or (II) used.
The polycarbonates A suitable for the purposes of the invention have average molecular weights ({overscore (M)}w, weight average, as measured for example by ultracentrifugation or scattered light measurement) in the range from 10,000 to 200,000 and preferably in the range from 20,000 to 80,000.
The polycarbonates A suitable for the purposes of the invention may be branched in known manner, preferably by the incorporation of 0.05 to 2 mol-%, based on the sum of the diphenols used, of trifunctional or more than trifunctional compounds, for example those containing three or more than three phenolic groups.
Besides bisphenol A homopolycarbonate, preferred polycarbonates are the copolycarbonates of bisphenol A with up to 15 mol-%, based on the total mols of diphenols used, of 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane and the copolycarbonates of b

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