Polycarbonate moulding compounds

Details Polycarbonate moulding compounds Polycarbonate moulding compounds

2002-05-08

2004-05-25

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...

C524S100000, C524S151000, C524S154000, C524S208000, C524S311000, C524S312000, C524S313000, C428S412000, C554S122000

Reexamination Certificate

active

06740693

ABSTRACT:

The invention relates to polycarbonate moulding compositions and objects, in particular sheets, produced partly or completely from these moulding compositions.
Polycarbonate sheets are known, for example, from EP-A 0 110 221 and are provided for a large number of intended uses. They are produced by extrusion of polycarbonate moulding compositions and optionally coextrusion with polycarbonate moulding compositions which comprise an increased content of UV absorbers.
An ever recurring problem in the extrusion of such sheets is the deposition of volatile constituents from the moulding composition on the calibrator (in the case of spaced sheets) or on the rolls (in the case of massive sheets), which can cause surface defects. Volatile constituents are, for example, UV absorbers, mould release agents and other low-volatility secondary constituents.
EP-A 0 320 632 describes coextruded sheets of polycarbonates which comprise a UV absorber and can comprise a lubricant. A disadvantage is that during the relatively long extrusion time the surface of the sheets is adversely influenced by evaporations from the polycarbonate melt, especially in the case of coextrusion. Increased evaporation of the UV absorber out of the polycarbonate melt leads to the formation of a deposit on the calibrator or the rolls and finally to the formation of defects in the sheet surface, for example white specks and waviness. Furthermore, the abraded polycarbonate on the calibrator can cause pulverulent deposits on the coextruded polycarbonate sheets.
EP-A 0 649 724 describes a process for the production of multilayered slabs of plastic from branched polycarbonates with molecular weights {overscore (M)}
w
of 27,000 to 29,500 by coextrusion of a core layer and at least one top layer with 1 to 15 wt. % of a UV absorber. If the mould release agents described in EP-A 0 300 485, glycerol monostearate, pentaerythritol tetrastearate and mixtures thereof with glycerol monostearate, are employed as main components in the moulding compositions for the production of these slabs of plastic, a deterioration in the surfaces of the sheets nevertheless occurs in time.
The invention is thus based on the object of optimizing polycarbonate moulding compositions for sheet production to the extent that the good quality of the surface of the extruded polycarbonate sheets can be retained even during a relatively long continuous operation.
This object is achieved by polycarbonate moulding compositions which comprise compounds of the general formula (I)
wherein
A represents a C
10
to C
40
-fatty acid radical, preferably C
22
to C
34
-fatty acid radical,
B represents a radical derived from a trivalent alcohol having 3 to 20, preferably 5 to 10 carbon atoms, particularly preferably the trimethylolpropane radical,
C represents a dicarboxylic acid radical having 4 to 40, preferably 5 to 10 carbon atoms and
n represents an integer from 0 to 15.
These compounds are commercially available.
The use of these compounds has proved to be particularly favourable for polycarbonate moulding compositions. They can be processed with polycarbonates without problems and show no impairment in the shaped articles obtained as the product. Surprisingly, it has been found that when these compounds are employed as polycarbonate moulding composition additives which are known to be volatile, they no longer lead to the problems described above.
The concentration of the compounds of the formula (I) to be employed according to the invention in the polycarbonate moulding composition can preferably be 0.02 to 1 wt. %, in particular 0.05 to 0.4 wt. %, based on the weight of the moulding composition.
Thermoplastic aromatic polycarbonates for the moulding compositions according to the invention or the sheets of plastic to be produced therefrom are those which have also been used hitherto for this purpose. These are homopolycarbonates, copolycarbonates and thermoplastic polyester-carbonates. They have average molecular weights {overscore (M)}
w
of 25,000 to 40,000, preferably 26,000 to 36,000, and in particular 28,000 to 35,000, determined by measuring the relative solution viscosity in methylene chloride or in mixtures of equal amounts by weight of phenol/o-dichlorobenzene, calibrated by light scattering.
For the preparation of polycarbonates, reference is made by way of example to “Schnell”, Chemistry and Physics of Polycarbonates, Polymer Reviews, vol. 9, Interscience Publishers, New York, London, Sydney 1964, to D. C. PREVORSEK, B. T. DEBONA and Y. KESTEN, Corporate Research Center, Allied Chemical Corporation, Moristown, N.J. 07960, “Synthesis of Poly(ester)carbonate Copolymers” in Journal of Polymer Science, Polymer Chemistry Edition, vol. 19, 75-90 (1980), to D. Freitag, U. Grigo, P. R. Müller, N. Nouvertne, BAYER AG,
“Polycarbonates” in Encyclopaedia of Polymer Science and Engineering, vol. 11, second edition, 1988, pages 648-718 and finally to Dres. U. Grigo, K. Kircher and P. R. Müller “Polycarbonate [Polycarbonates]” in Becker/Braun, Kunststoff-Handbuch [Plastics Handbook], volume 3/1, Polycarbonate, Polyacetale, Polyester, Celluloseeste [Polycarbonates, Polyacetals, Polyesters, Cellulose Esters], Carl Hanser Verlag Munich, Vienna 1992, pages 117-299. The preparation is preferably carried out by the phase boundary process or the melt transesterification process and is described using the phase boundary process by way of example.
Compounds which are preferably to be employed as starting compounds are bisphenols of the general formula HO—Z—OH, wherein Z is a divalent organic radical having 6 to 30 carbon atoms, which contains one or more aromatic groups. Examples of such compounds are bisphenols which belong to the group of dihydroxydiphenyls, bis(hydroxyphenyl)alkanes, indanebisphenols, bis(hydroxy-phenyl)ethers, bis(hydroxyphenyl)sulfones, bis(hydroxyphenyl)ketones and &agr;,&agr;′-bis(hydroxyphenyl)-diisopropylbenzenes.
Particularly preferred bisphenols which belong to the abovementioned groups of compounds are bisphenol A, tetraalkylbisphenol A, 4,4-(meta-phenylenediisopropyl)-diphenol (bisphenol M), 4,4-(para-phenylenediisopropyl)-diphenol, 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (BP-TMC) and optionally mixtures thereof. Homopolycarbonates based on bisphenol A and copolycarbonates based on the monomers bisphenol A and 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane are particularly preferred. The bisphenol compounds to be employed according to the invention are reacted with carbonic acid compounds, in particular phosgene or, in the melt transesterification process, diphenyl carbonate or dimethyl carbonate.
Polyester-carbonates are obtained by reaction of the bisphenols already mentioned, at least one aromatic dicarboxylic acid and optionally carbonic acid equivalents.
Suitable aromatic dicarboxylic acids are, for example, orthophthalic acid, terephthalic acid, isophthalic acid, 3,3′- or 4,4′-diphenyldicarboxylic acid and benzophenonedicarboxylic acids. Some, up to 80 mol %, preferably 20 to 50 mol %, of the carbonate groups in the polycarbonates can be replaced by aromatic dicarboxylic acid ester groups.
Inert organic solvents used are, for example, methylene chloride, the various dichloroethanes and chloropropane compounds, carbon tetrachloride, chloroform, chlorobenzene and chlorotoluene, and chlorobenzene and methylene chloride or mixtures thereof are preferably employed.
The reaction can be accelerated by catalysts, such as tertiary amines, N-alkylpiperidines or onium salts. Tributylamine, triethylamine and N-ethylpiperidine are preferably used. If the melt transesterification process is used for the preparation of polycarbonates, the catalysts mentioned in DE-A 42 38 123 can be used.
The polycarbonates can be branched deliberately and in a controlled manner by the use of small amounts of branching agents. Suitable branching agents are, for example, phloroglucinol; 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-hept-2-ene; 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane; 1,3,5-tri-(4-hydr

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