Flame-resistant polycarbonate moulding compounds

Details Flame-resistant polycarbonate moulding compounds Flame-resistant polycarbonate moulding compounds

2002-09-03

2004-12-07

Szekely, Peter (Department: 1714)

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

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S437000, C524S451000

Reexamination Certificate

active

06828366

ABSTRACT:

The present invention relates to impact-modified polycarbonate compositions having a low fluorine content which are distinguished by excellent flame resistance even at low wall thickness, as well as exceptionally good chemical and heat resistance.
Impact-modified polycarbonate moulding compositions which are rendered flame-resistant in chlorine-free, bromine-free manner are known.
EP-A 0 345 522 describes polymer mixtures prepared from aromatic polycarbonate, ABS graft polymer and/or copolymer which comprises styrene, which are rendered flame-resistant with monophosphoric acid esters. In addition the polymer mixtures contain Teflon at a concentration of 0.3 wt. % as a drip-prevention agent.
U.S. Pat. Nos. 5,204,394 and 5,672,645 describe PC/ABS moulding compositions which are rendered flame-resistant by oligophosphoric acid ester and mixtures of oligophosphoric and monophosphoric acid ester, respectively. The moulding compositions described also contain as a drip-prevention agent Teflon used at concentrations of from 0.2 to 0.5 parts by weight, in relation to 100 parts by weight of the moulding composition without Teflon.
JP-A 111 997 68 describes PC/ABS blends which are rendered flame-resistant with monomeric and oligomeric phosphoric acid esters, with the flame resistance being improved markedly by the addition of an inorganic filler such as, for example, talc. Teflon, at concentrations of from 0.2 to 0.5 parts by weight, in relation to 100 parts by weight of PC+ABS, must also be added to these moulding compounds in order to prevent the dripping of burning material. In each case this corresponds to a Teflon concentration of >0.15 wt. %. JP-A 111 997 68 also discloses a flame-resistant PC/ABS moulding composition based on triphenyl phosphate as the flame retardant, which even without the addition of Teflon meets the V-0 standard in the UL94 V test. This moulding composition contains stabilised red phosphorus and larger quantities of talc which affect the mechanical properties and the inherent colour of the polymer blend to great disadvantage.
U.S. Pat. No. 5,849,827 describes PC/ABS moulding compositions which are rendered flame-resistant with resorcinol-based oligophosphate, with the afterburning times being reduced markedly by the addition of nanoscale inorganic materials at low concentrations. Experience shows that the tendency to drip burning material is not reduced by the nanoparticles, such that the addition of drip-prevention agents such as, for example, Teflon continues to be necessary in order to meet the V-0 standard in the UL94 V test.
WO 99/07782 describes PC/ABS moulding compositions which are rendered flame-resistant with a special oligophosphate derived from bisphenol A and which contain additionally synergistic quantities of a nanoscale inorganic compound. The moulding compositions are distinguished by improved resistance to environmental stress cracking (ESC) and high heat resistance. The moulding compositions contain Teflon at a concentration of 0.35%.
EP-A 0 754 531 also describes, inter alia, flame-resistant PC/ABS moulding compositions which are rendered flame-resistant with oligophosphates of the bisphenol A type or methyl-substituted derivatives thereof and comprise flake-form fillers such as mica and/or glass flakes, optionally also in combination with glass fibres. The moulding compositions described do not contain Teflon. They are distinguished by good stiffness and dimensional stability (low warpage) and show negligible plate-out when processed by injection moulding. No information as to the quality of the flame resistance of the PC/ABS moulding compositions, in particular regarding the tendency to drip burning material, is disclosed. The high inorganic filler content of the moulding compositions described affects negatively some mechanical properties. This results, for example, in a degree of impact strength which for many applications is inadequate.
In some plastics applications, in particular in some areas within the electrical and electronics industry, safety considerations dictate customer requirements or even legal requirements for a restriction not only of the chlorine and bromine content, but also of the fluorine content. Thus, for example, a material is deemed to be “halogen-free” in accordance with DIN/VDE standard 0472, Part 815 only when the percentages by mass of the halogens chlorine, bromine and iodine, calculated as chlorine, are ≦0.2% and the proportion by mass of fluorine is furthermore ≦0.1%.
WO 99/57198 describes PC/ABS moulding compositions which are rendered flame-resistant with a resorcinol-derived oligophosphate (RDP) and are classified as halogen-free in accordance with VDE/DIN 0472, Part 815 by virtue of their low Teflon content of only 0.1—corresponding to a fluorine content of 0.076%. Such moulding compositions, however, have poor resistance to ESC and inadequate heat resistance, as well as a melt stability which is frequently inadequate, in particular for extrusion applications.
The object of the present invention was to provide a moulding composition which conforms to VDE/DIN standard 0472, Part 815, having a fluorine content of ≦0.1%, which is distinguished by excellent flame resistance, good mechanical properties, improved beat resistance and improved resistance to ESC, and which by virtue of its rheological properties (melt viscosity and melt stability) is also usable for extrusion applications.
It has now been found that impact-modified polycarbonate compositions which are rendered flame-resistant with special oligophosphates derived from bisphenol A or analogous diols and which optionally additionally contain small quantities of inorganic materials show the desired property profile.
The present invention consequently provides polycarbonate compositions containing
A) at least one aromatic polycarbonate or polyester carbonate,
B) at least one impact modifier and
C) at least one phosphorus compound corresponding to the general formula (I)
in which
R
1
, R
2
, R
3
and R
4
in each case independently of one another denote C
1
-C
8
-alkyl and/or optionally alkyl-substituted C
5
-C
6
-cycloalkyl, C
6
-C
10
-aryl or C
7
-C
12
-aralkyl,
n independently of one another denotes 0 or 1,
q independently of one another denotes 0, 1, 2, 3 or 4,
N denotes a number between 0.1 and 30, preferably between 0.5 and 10, in particular between 0.7 and 5,
R
5
and R
6
independently of one another denote C
1
-C
4
-alkyl, preferably methyl, and
Y denotes C
1
-C
7
-alkylidene, C
1
-C
7
-alkylene, C
5
-C
12
-cycloalkylene, C
5
-C
12
-cycloalkylidene, —O—, —S—, —SO—, SO
2
or —CO—, wherein the moulding compositions are characterised in that they conform to VDE/DIN standard 0472, Part 815, that is to say that they contain ≦0.1 wt. % fluorine and ≦0.2 wt. % chlorine, bromine and iodine, in relation to the total composition.
Optionally the compositions may additionally contain
D) a fluorinated polyolefinic compound as a drip-prevention agent,
E) a further polymer component,
F) an inorganic material and
G) conventional polymer additives such as, for example, drip-prevention agents, lubricants and mould release agents, nucleating agents, antistatic agents, stabilisers, dyes and pigments.
The compositions according to the invention are further characterised in that they pass the UL94 V test to the standard V-0, preferably at wall thickness ≦1.55 mm.
The fluorine content is preferably determined by means of the photometric analytical procedure described in DIN/VDE standard 0472, Part 815.
Preferred moulding compositions comprise
A) from 60 to 98 parts by weight, preferably 70 to 95 parts by weight, particularly preferably 75 to 90 parts by weight of at least one aromatic polycarbonate,
B) from 0.5 to 30, preferably 1 to 15, particularly preferably 2 to 10 parts by weight of at least one graft polymer having a backbone of rubber,
C) from 1 to 20 parts by weight, preferably 2 to 15 parts by weight of a bisphenol A-based oligophosphate,
D) from 0 to 0.13 part by weight Teflon, and
E) from 0 to 20 parts by weight, preferably 0

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